SpringCloud 源码系列（5）—— 负载均衡 Ribbon（下）
SpringCloud 源码系列（4）—— 负载均衡 Ribbon（上）
SpringCloud 源码系列（5）—— 负载均衡 Ribbon（下）
五、Ribbon 核心接口
前面已经了解到 Ribbon 核心接口以及默认实现如何协作来查找要调用的一个实例，这节再来看下各个核心接口的一些特性及其它实现类。
1、客户端配置 — IClientConfig
IClientConfig 就是管理客户端配置的核心接口，它的默认实现类是 DefaultClientConfigImpl。可以看到在创建 IClientConfig 时，设置了 Ribbon 客户端默认的连接和读取超时时间为 1 秒，例如读取如果超过1秒，就会返回超时，这两个一般需要根据实际情况来调整。、
1 @Bean
2 @ConditionalOnMissingBean
3 public IClientConfig ribbonClientConfig() {
4 DefaultClientConfigImpl config = new DefaultClientConfigImpl();
5 // 加载配置
6 config.loadProperties(this.name);
7 // 连接超时默认 1 秒
8 config.set(CommonClientConfigKey.ConnectTimeout, DEFAULT_CONNECT_TIMEOUT);
9 // 读取超时默认 1 秒
10 config.set(CommonClientConfigKey.ReadTimeout, DEFAULT_READ_TIMEOUT);
11 config.set(CommonClientConfigKey.GZipPayload, DEFAULT_GZIP_PAYLOAD);
12 return config;
13 }
CommonClientConfigKey 这个类定义了 Ribbon 客户端相关的所有配置的键常量，可以通过这个类来看有哪些配置。
1 public abstract class CommonClientConfigKey<T> implements IClientConfigKey<T> {
2
3 public static final IClientConfigKey<String> AppName = new CommonClientConfigKey<String>("AppName"){};
4
5 public static final IClientConfigKey<String> Version = new CommonClientConfigKey<String>("Version"){};
6
7 public static final IClientConfigKey<Integer> Port = new CommonClientConfigKey<Integer>("Port"){};
8
9 public static final IClientConfigKey<Integer> SecurePort = new CommonClientConfigKey<Integer>("SecurePort"){};
10
11 public static final IClientConfigKey<String> VipAddress = new CommonClientConfigKey<String>("VipAddress"){};
12
13 public static final IClientConfigKey<Boolean> ForceClientPortConfiguration = new CommonClientConfigKey<Boolean>("ForceClientPortConfiguration"){}; // use client defined port regardless of server advert
14
15 public static final IClientConfigKey<String> DeploymentContextBasedVipAddresses = new CommonClientConfigKey<String>("DeploymentContextBasedVipAddresses"){};
16
17 public static final IClientConfigKey<Integer> MaxAutoRetries = new CommonClientConfigKey<Integer>("MaxAutoRetries"){};
18
19 public static final IClientConfigKey<Integer> MaxAutoRetriesNextServer = new CommonClientConfigKey<Integer>("MaxAutoRetriesNextServer"){};
20
21 public static final IClientConfigKey<Boolean> OkToRetryOnAllOperations = new CommonClientConfigKey<Boolean>("OkToRetryOnAllOperations"){};
22
23 public static final IClientConfigKey<Boolean> RequestSpecificRetryOn = new CommonClientConfigKey<Boolean>("RequestSpecificRetryOn"){};
24
25 public static final IClientConfigKey<Integer> ReceiveBufferSize = new CommonClientConfigKey<Integer>("ReceiveBufferSize"){};
26
27 public static final IClientConfigKey<Boolean> EnablePrimeConnections = new CommonClientConfigKey<Boolean>("EnablePrimeConnections"){};
28
29 public static final IClientConfigKey<String> PrimeConnectionsClassName = new CommonClientConfigKey<String>("PrimeConnectionsClassName"){};
30
31 public static final IClientConfigKey<Integer> MaxRetriesPerServerPrimeConnection = new CommonClientConfigKey<Integer>("MaxRetriesPerServerPrimeConnection"){};
32
33 public static final IClientConfigKey<Integer> MaxTotalTimeToPrimeConnections = new CommonClientConfigKey<Integer>("MaxTotalTimeToPrimeConnections"){};
34
35 public static final IClientConfigKey<Float> MinPrimeConnectionsRatio = new CommonClientConfigKey<Float>("MinPrimeConnectionsRatio"){};
36
37 public static final IClientConfigKey<String> PrimeConnectionsURI = new CommonClientConfigKey<String>("PrimeConnectionsURI"){};
38
39 public static final IClientConfigKey<Integer> PoolMaxThreads = new CommonClientConfigKey<Integer>("PoolMaxThreads"){};
40
41 public static final IClientConfigKey<Integer> PoolMinThreads = new CommonClientConfigKey<Integer>("PoolMinThreads"){};
42
43 public static final IClientConfigKey<Integer> PoolKeepAliveTime = new CommonClientConfigKey<Integer>("PoolKeepAliveTime"){};
44
45 public static final IClientConfigKey<String> PoolKeepAliveTimeUnits = new CommonClientConfigKey<String>("PoolKeepAliveTimeUnits"){};
46
47 public static final IClientConfigKey<Boolean> EnableConnectionPool = new CommonClientConfigKey<Boolean>("EnableConnectionPool") {};
48
49 /**
50 * Use {@link #MaxConnectionsPerHost}
51 */
52 @Deprecated
53 public static final IClientConfigKey<Integer> MaxHttpConnectionsPerHost = new CommonClientConfigKey<Integer>("MaxHttpConnectionsPerHost"){};
54
55 /**
56 * Use {@link #MaxTotalConnections}
57 */
58 @Deprecated
59 public static final IClientConfigKey<Integer> MaxTotalHttpConnections = new CommonClientConfigKey<Integer>("MaxTotalHttpConnections"){};
60
61 public static final IClientConfigKey<Integer> MaxConnectionsPerHost = new CommonClientConfigKey<Integer>("MaxConnectionsPerHost"){};
62
63 public static final IClientConfigKey<Integer> MaxTotalConnections = new CommonClientConfigKey<Integer>("MaxTotalConnections"){};
64
65 public static final IClientConfigKey<Boolean> IsSecure = new CommonClientConfigKey<Boolean>("IsSecure"){};
66
67 public static final IClientConfigKey<Boolean> GZipPayload = new CommonClientConfigKey<Boolean>("GZipPayload"){};
68
69 public static final IClientConfigKey<Integer> ConnectTimeout = new CommonClientConfigKey<Integer>("ConnectTimeout"){};
70
71 public static final IClientConfigKey<Integer> BackoffInterval = new CommonClientConfigKey<Integer>("BackoffTimeout"){};
72
73 public static final IClientConfigKey<Integer> ReadTimeout = new CommonClientConfigKey<Integer>("ReadTimeout"){};
74
75 public static final IClientConfigKey<Integer> SendBufferSize = new CommonClientConfigKey<Integer>("SendBufferSize"){};
76
77 public static final IClientConfigKey<Boolean> StaleCheckingEnabled = new CommonClientConfigKey<Boolean>("StaleCheckingEnabled"){};
78
79 public static final IClientConfigKey<Integer> Linger = new CommonClientConfigKey<Integer>("Linger"){};
80
81 public static final IClientConfigKey<Integer> ConnectionManagerTimeout = new CommonClientConfigKey<Integer>("ConnectionManagerTimeout"){};
82
83 public static final IClientConfigKey<Boolean> FollowRedirects = new CommonClientConfigKey<Boolean>("FollowRedirects"){};
84
85 public static final IClientConfigKey<Boolean> ConnectionPoolCleanerTaskEnabled = new CommonClientConfigKey<Boolean>("ConnectionPoolCleanerTaskEnabled"){};
86
87 public static final IClientConfigKey<Integer> ConnIdleEvictTimeMilliSeconds = new CommonClientConfigKey<Integer>("ConnIdleEvictTimeMilliSeconds"){};
88
89 public static final IClientConfigKey<Integer> ConnectionCleanerRepeatInterval = new CommonClientConfigKey<Integer>("ConnectionCleanerRepeatInterval"){};
90
91 public static final IClientConfigKey<Boolean> EnableGZIPContentEncodingFilter = new CommonClientConfigKey<Boolean>("EnableGZIPContentEncodingFilter"){};
92
93 public static final IClientConfigKey<String> ProxyHost = new CommonClientConfigKey<String>("ProxyHost"){};
94
95 public static final IClientConfigKey<Integer> ProxyPort = new CommonClientConfigKey<Integer>("ProxyPort"){};
96
97 public static final IClientConfigKey<String> KeyStore = new CommonClientConfigKey<String>("KeyStore"){};
98
99 public static final IClientConfigKey<String> KeyStorePassword = new CommonClientConfigKey<String>("KeyStorePassword"){};
100
101 public static final IClientConfigKey<String> TrustStore = new CommonClientConfigKey<String>("TrustStore"){};
102
103 public static final IClientConfigKey<String> TrustStorePassword = new CommonClientConfigKey<String>("TrustStorePassword"){};
104
105 // if this is a secure rest client, must we use client auth too?
106 public static final IClientConfigKey<Boolean> IsClientAuthRequired = new CommonClientConfigKey<Boolean>("IsClientAuthRequired"){};
107
108 public static final IClientConfigKey<String> CustomSSLSocketFactoryClassName = new CommonClientConfigKey<String>("CustomSSLSocketFactoryClassName"){};
109 // must host name match name in certificate?
110 public static final IClientConfigKey<Boolean> IsHostnameValidationRequired = new CommonClientConfigKey<Boolean>("IsHostnameValidationRequired"){};
111
112 // see also http://hc.apache.org/httpcomponents-client-ga/tutorial/html/advanced.html
113 public static final IClientConfigKey<Boolean> IgnoreUserTokenInConnectionPoolForSecureClient = new CommonClientConfigKey<Boolean>("IgnoreUserTokenInConnectionPoolForSecureClient"){};
114
115 // Client implementation
116 public static final IClientConfigKey<String> ClientClassName = new CommonClientConfigKey<String>("ClientClassName"){};
117
118 //LoadBalancer Related
119 public static final IClientConfigKey<Boolean> InitializeNFLoadBalancer = new CommonClientConfigKey<Boolean>("InitializeNFLoadBalancer"){};
120
121 public static final IClientConfigKey<String> NFLoadBalancerClassName = new CommonClientConfigKey<String>("NFLoadBalancerClassName"){};
122
123 public static final IClientConfigKey<String> NFLoadBalancerRuleClassName = new CommonClientConfigKey<String>("NFLoadBalancerRuleClassName"){};
124
125 public static final IClientConfigKey<String> NFLoadBalancerPingClassName = new CommonClientConfigKey<String>("NFLoadBalancerPingClassName"){};
126
127 public static final IClientConfigKey<Integer> NFLoadBalancerPingInterval = new CommonClientConfigKey<Integer>("NFLoadBalancerPingInterval"){};
128
129 public static final IClientConfigKey<Integer> NFLoadBalancerMaxTotalPingTime = new CommonClientConfigKey<Integer>("NFLoadBalancerMaxTotalPingTime"){};
130
131 public static final IClientConfigKey<String> NFLoadBalancerStatsClassName = new CommonClientConfigKey<String>("NFLoadBalancerStatsClassName"){};
132
133 public static final IClientConfigKey<String> NIWSServerListClassName = new CommonClientConfigKey<String>("NIWSServerListClassName"){};
134
135 public static final IClientConfigKey<String> ServerListUpdaterClassName = new CommonClientConfigKey<String>("ServerListUpdaterClassName"){};
136
137 public static final IClientConfigKey<String> NIWSServerListFilterClassName = new CommonClientConfigKey<String>("NIWSServerListFilterClassName"){};
138
139 public static final IClientConfigKey<Integer> ServerListRefreshInterval = new CommonClientConfigKey<Integer>("ServerListRefreshInterval"){};
140
141 public static final IClientConfigKey<Boolean> EnableMarkingServerDownOnReachingFailureLimit = new CommonClientConfigKey<Boolean>("EnableMarkingServerDownOnReachingFailureLimit"){};
142
143 public static final IClientConfigKey<Integer> ServerDownFailureLimit = new CommonClientConfigKey<Integer>("ServerDownFailureLimit"){};
144
145 public static final IClientConfigKey<Integer> ServerDownStatWindowInMillis = new CommonClientConfigKey<Integer>("ServerDownStatWindowInMillis"){};
146
147 public static final IClientConfigKey<Boolean> EnableZoneAffinity = new CommonClientConfigKey<Boolean>("EnableZoneAffinity"){};
148
149 public static final IClientConfigKey<Boolean> EnableZoneExclusivity = new CommonClientConfigKey<Boolean>("EnableZoneExclusivity"){};
150
151 public static final IClientConfigKey<Boolean> PrioritizeVipAddressBasedServers = new CommonClientConfigKey<Boolean>("PrioritizeVipAddressBasedServers"){};
152
153 public static final IClientConfigKey<String> VipAddressResolverClassName = new CommonClientConfigKey<String>("VipAddressResolverClassName"){};
154
155 public static final IClientConfigKey<String> TargetRegion = new CommonClientConfigKey<String>("TargetRegion"){};
156
157 public static final IClientConfigKey<String> RulePredicateClasses = new CommonClientConfigKey<String>("RulePredicateClasses"){};
158
159 public static final IClientConfigKey<String> RequestIdHeaderName = new CommonClientConfigKey<String>("RequestIdHeaderName") {};
160
161 public static final IClientConfigKey<Boolean> UseIPAddrForServer = new CommonClientConfigKey<Boolean>("UseIPAddrForServer") {};
162
163 public static final IClientConfigKey<String> ListOfServers = new CommonClientConfigKey<String>("listOfServers") {};
164
165 private static final Set<IClientConfigKey> keys = new HashSet<IClientConfigKey>();
166
167 // ...
168 }
进入到 DefaultClientConfigImpl，可以看到 CommonClientConfigKey 中的每个配置都对应了一个默认值。在加载配置的时候，如果用户没有定制配置，就会使用默认的配置。
1 public class DefaultClientConfigImpl implements IClientConfig {
2
3 public static final Boolean DEFAULT_PRIORITIZE_VIP_ADDRESS_BASED_SERVERS = Boolean.TRUE;
4
5 public static final String DEFAULT_NFLOADBALANCER_PING_CLASSNAME = "com.netflix.loadbalancer.DummyPing"; // DummyPing.class.getName();
6
7 public static final String DEFAULT_NFLOADBALANCER_RULE_CLASSNAME = "com.netflix.loadbalancer.AvailabilityFilteringRule";
8
9 public static final String DEFAULT_NFLOADBALANCER_CLASSNAME = "com.netflix.loadbalancer.ZoneAwareLoadBalancer";
10
11 public static final boolean DEFAULT_USEIPADDRESS_FOR_SERVER = Boolean.FALSE;
12
13 public static final String DEFAULT_CLIENT_CLASSNAME = "com.netflix.niws.client.http.RestClient";
14
15 public static final String DEFAULT_VIPADDRESS_RESOLVER_CLASSNAME = "com.netflix.client.SimpleVipAddressResolver";
16
17 public static final String DEFAULT_PRIME_CONNECTIONS_URI = "/";
18
19 public static final int DEFAULT_MAX_TOTAL_TIME_TO_PRIME_CONNECTIONS = 30000;
20
21 public static final int DEFAULT_MAX_RETRIES_PER_SERVER_PRIME_CONNECTION = 9;
22
23 public static final Boolean DEFAULT_ENABLE_PRIME_CONNECTIONS = Boolean.FALSE;
24
25 public static final int DEFAULT_MAX_REQUESTS_ALLOWED_PER_WINDOW = Integer.MAX_VALUE;
26
27 public static final int DEFAULT_REQUEST_THROTTLING_WINDOW_IN_MILLIS = 60000;
28
29 public static final Boolean DEFAULT_ENABLE_REQUEST_THROTTLING = Boolean.FALSE;
30
31 public static final Boolean DEFAULT_ENABLE_GZIP_CONTENT_ENCODING_FILTER = Boolean.FALSE;
32
33 public static final Boolean DEFAULT_CONNECTION_POOL_CLEANER_TASK_ENABLED = Boolean.TRUE;
34
35 public static final Boolean DEFAULT_FOLLOW_REDIRECTS = Boolean.FALSE;
36
37 public static final float DEFAULT_PERCENTAGE_NIWS_EVENT_LOGGED = 0.0f;
38
39 public static final int DEFAULT_MAX_AUTO_RETRIES_NEXT_SERVER = 1;
40
41 public static final int DEFAULT_MAX_AUTO_RETRIES = 0;
42
43 public static final int DEFAULT_BACKOFF_INTERVAL = 0;
44
45 public static final int DEFAULT_READ_TIMEOUT = 5000;
46
47 public static final int DEFAULT_CONNECTION_MANAGER_TIMEOUT = 2000;
48
49 public static final int DEFAULT_CONNECT_TIMEOUT = 2000;
50
51 public static final Boolean DEFAULT_ENABLE_CONNECTION_POOL = Boolean.TRUE;
52
53 @Deprecated
54 public static final int DEFAULT_MAX_HTTP_CONNECTIONS_PER_HOST = 50;
55
56 @Deprecated
57 public static final int DEFAULT_MAX_TOTAL_HTTP_CONNECTIONS = 200;
58
59 public static final int DEFAULT_MAX_CONNECTIONS_PER_HOST = 50;
60
61 public static final int DEFAULT_MAX_TOTAL_CONNECTIONS = 200;
62
63 public static final float DEFAULT_MIN_PRIME_CONNECTIONS_RATIO = 1.0f;
64
65 public static final String DEFAULT_PRIME_CONNECTIONS_CLASS = "com.netflix.niws.client.http.HttpPrimeConnection";
66
67 public static final String DEFAULT_SEVER_LIST_CLASS = "com.netflix.loadbalancer.ConfigurationBasedServerList";
68
69 public static final String DEFAULT_SERVER_LIST_UPDATER_CLASS = "com.netflix.loadbalancer.PollingServerListUpdater";
70
71 public static final int DEFAULT_CONNECTION_IDLE_TIMERTASK_REPEAT_IN_MSECS = 30000; // every half minute (30 secs)
72
73 public static final int DEFAULT_CONNECTIONIDLE_TIME_IN_MSECS = 30000; // all connections idle for 30 secs
74
75 protected volatile Map<String, Object> properties = new ConcurrentHashMap<String, Object>();
76
77 protected Map<IClientConfigKey<?>, Object> typedProperties = new ConcurrentHashMap<IClientConfigKey<?>, Object>();
78
79 private static final Logger LOG = LoggerFactory.getLogger(DefaultClientConfigImpl.class);
80
81 private String clientName = null;
82
83 private VipAddressResolver resolver = null;
84
85 private boolean enableDynamicProperties = true;
86 /**
87 * Defaults for the parameters for the thread pool used by batchParallel
88 * calls
89 */
90 public static final int DEFAULT_POOL_MAX_THREADS = DEFAULT_MAX_TOTAL_HTTP_CONNECTIONS;
91 public static final int DEFAULT_POOL_MIN_THREADS = 1;
92 public static final long DEFAULT_POOL_KEEP_ALIVE_TIME = 15 * 60L;
93 public static final TimeUnit DEFAULT_POOL_KEEP_ALIVE_TIME_UNITS = TimeUnit.SECONDS;
94 public static final Boolean DEFAULT_ENABLE_ZONE_AFFINITY = Boolean.FALSE;
95 public static final Boolean DEFAULT_ENABLE_ZONE_EXCLUSIVITY = Boolean.FALSE;
96 public static final int DEFAULT_PORT = 7001;
97 public static final Boolean DEFAULT_ENABLE_LOADBALANCER = Boolean.TRUE;
98
99 public static final String DEFAULT_PROPERTY_NAME_SPACE = "ribbon";
100
101 private String propertyNameSpace = DEFAULT_PROPERTY_NAME_SPACE;
102
103 public static final Boolean DEFAULT_OK_TO_RETRY_ON_ALL_OPERATIONS = Boolean.FALSE;
104
105 public static final Boolean DEFAULT_ENABLE_NIWS_EVENT_LOGGING = Boolean.TRUE;
106
107 public static final Boolean DEFAULT_IS_CLIENT_AUTH_REQUIRED = Boolean.FALSE;
108
109 private final Map<String, DynamicStringProperty> dynamicProperties = new ConcurrentHashMap<String, DynamicStringProperty>();
110
111 public Boolean getDefaultPrioritizeVipAddressBasedServers() {
112 return DEFAULT_PRIORITIZE_VIP_ADDRESS_BASED_SERVERS;
113 }
114
115 public String getDefaultNfloadbalancerPingClassname() {
116 return DEFAULT_NFLOADBALANCER_PING_CLASSNAME;
117 }
118
119 public String getDefaultNfloadbalancerRuleClassname() {
120 return DEFAULT_NFLOADBALANCER_RULE_CLASSNAME;
121 }
122
123 public String getDefaultNfloadbalancerClassname() {
124 return DEFAULT_NFLOADBALANCER_CLASSNAME;
125 }
126
127 public boolean getDefaultUseIpAddressForServer() {
128 return DEFAULT_USEIPADDRESS_FOR_SERVER;
129 }
130
131 public String getDefaultClientClassname() {
132 return DEFAULT_CLIENT_CLASSNAME;
133 }
134
135 public String getDefaultVipaddressResolverClassname() {
136 return DEFAULT_VIPADDRESS_RESOLVER_CLASSNAME;
137 }
138
139 public String getDefaultPrimeConnectionsUri() {
140 return DEFAULT_PRIME_CONNECTIONS_URI;
141 }
142
143 public int getDefaultMaxTotalTimeToPrimeConnections() {
144 return DEFAULT_MAX_TOTAL_TIME_TO_PRIME_CONNECTIONS;
145 }
146
147 public int getDefaultMaxRetriesPerServerPrimeConnection() {
148 return DEFAULT_MAX_RETRIES_PER_SERVER_PRIME_CONNECTION;
149 }
150
151 public Boolean getDefaultEnablePrimeConnections() {
152 return DEFAULT_ENABLE_PRIME_CONNECTIONS;
153 }
154
155 public int getDefaultMaxRequestsAllowedPerWindow() {
156 return DEFAULT_MAX_REQUESTS_ALLOWED_PER_WINDOW;
157 }
158
159 public int getDefaultRequestThrottlingWindowInMillis() {
160 return DEFAULT_REQUEST_THROTTLING_WINDOW_IN_MILLIS;
161 }
162
163 public Boolean getDefaultEnableRequestThrottling() {
164 return DEFAULT_ENABLE_REQUEST_THROTTLING;
165 }
166
167 public Boolean getDefaultEnableGzipContentEncodingFilter() {
168 return DEFAULT_ENABLE_GZIP_CONTENT_ENCODING_FILTER;
169 }
170
171 public Boolean getDefaultConnectionPoolCleanerTaskEnabled() {
172 return DEFAULT_CONNECTION_POOL_CLEANER_TASK_ENABLED;
173 }
174
175 public Boolean getDefaultFollowRedirects() {
176 return DEFAULT_FOLLOW_REDIRECTS;
177 }
178
179 public float getDefaultPercentageNiwsEventLogged() {
180 return DEFAULT_PERCENTAGE_NIWS_EVENT_LOGGED;
181 }
182
183 public int getDefaultMaxAutoRetriesNextServer() {
184 return DEFAULT_MAX_AUTO_RETRIES_NEXT_SERVER;
185 }
186
187 public int getDefaultMaxAutoRetries() {
188 return DEFAULT_MAX_AUTO_RETRIES;
189 }
190
191 public int getDefaultReadTimeout() {
192 return DEFAULT_READ_TIMEOUT;
193 }
194
195 public int getDefaultConnectionManagerTimeout() {
196 return DEFAULT_CONNECTION_MANAGER_TIMEOUT;
197 }
198
199 public int getDefaultConnectTimeout() {
200 return DEFAULT_CONNECT_TIMEOUT;
201 }
202
203 @Deprecated
204 public int getDefaultMaxHttpConnectionsPerHost() {
205 return DEFAULT_MAX_HTTP_CONNECTIONS_PER_HOST;
206 }
207
208 @Deprecated
209 public int getDefaultMaxTotalHttpConnections() {
210 return DEFAULT_MAX_TOTAL_HTTP_CONNECTIONS;
211 }
212
213 public int getDefaultMaxConnectionsPerHost() {
214 return DEFAULT_MAX_CONNECTIONS_PER_HOST;
215 }
216
217 public int getDefaultMaxTotalConnections() {
218 return DEFAULT_MAX_TOTAL_CONNECTIONS;
219 }
220
221 public float getDefaultMinPrimeConnectionsRatio() {
222 return DEFAULT_MIN_PRIME_CONNECTIONS_RATIO;
223 }
224
225 public String getDefaultPrimeConnectionsClass() {
226 return DEFAULT_PRIME_CONNECTIONS_CLASS;
227 }
228
229 public String getDefaultSeverListClass() {
230 return DEFAULT_SEVER_LIST_CLASS;
231 }
232
233 public int getDefaultConnectionIdleTimertaskRepeatInMsecs() {
234 return DEFAULT_CONNECTION_IDLE_TIMERTASK_REPEAT_IN_MSECS;
235 }
236
237 public int getDefaultConnectionidleTimeInMsecs() {
238 return DEFAULT_CONNECTIONIDLE_TIME_IN_MSECS;
239 }
240
241 public VipAddressResolver getResolver() {
242 return resolver;
243 }
244
245 public boolean isEnableDynamicProperties() {
246 return enableDynamicProperties;
247 }
248
249 public int getDefaultPoolMaxThreads() {
250 return DEFAULT_POOL_MAX_THREADS;
251 }
252
253 public int getDefaultPoolMinThreads() {
254 return DEFAULT_POOL_MIN_THREADS;
255 }
256
257 public long getDefaultPoolKeepAliveTime() {
258 return DEFAULT_POOL_KEEP_ALIVE_TIME;
259 }
260
261 public TimeUnit getDefaultPoolKeepAliveTimeUnits() {
262 return DEFAULT_POOL_KEEP_ALIVE_TIME_UNITS;
263 }
264
265 public Boolean getDefaultEnableZoneAffinity() {
266 return DEFAULT_ENABLE_ZONE_AFFINITY;
267 }
268
269 public Boolean getDefaultEnableZoneExclusivity() {
270 return DEFAULT_ENABLE_ZONE_EXCLUSIVITY;
271 }
272
273 public int getDefaultPort() {
274 return DEFAULT_PORT;
275 }
276
277 public Boolean getDefaultEnableLoadbalancer() {
278 return DEFAULT_ENABLE_LOADBALANCER;
279 }
280
281
282 public Boolean getDefaultOkToRetryOnAllOperations() {
283 return DEFAULT_OK_TO_RETRY_ON_ALL_OPERATIONS;
284 }
285
286 public Boolean getDefaultIsClientAuthRequired(){
287 return DEFAULT_IS_CLIENT_AUTH_REQUIRED;
288 }
289
290
291 /**
292 * Create instance with no properties in default name space {@link #DEFAULT_PROPERTY_NAME_SPACE}
293 */
294 public DefaultClientConfigImpl() {
295 this.dynamicProperties.clear();
296 this.enableDynamicProperties = false;
297 }
298
299 /**
300 * Create instance with no properties in the specified name space
301 */
302 public DefaultClientConfigImpl(String nameSpace) {
303 this();
304 this.propertyNameSpace = nameSpace;
305 }
306
307 public void loadDefaultValues() {
308 putDefaultIntegerProperty(CommonClientConfigKey.MaxHttpConnectionsPerHost, getDefaultMaxHttpConnectionsPerHost());
309 putDefaultIntegerProperty(CommonClientConfigKey.MaxTotalHttpConnections, getDefaultMaxTotalHttpConnections());
310 putDefaultBooleanProperty(CommonClientConfigKey.EnableConnectionPool, getDefaultEnableConnectionPool());
311 putDefaultIntegerProperty(CommonClientConfigKey.MaxConnectionsPerHost, getDefaultMaxConnectionsPerHost());
312 putDefaultIntegerProperty(CommonClientConfigKey.MaxTotalConnections, getDefaultMaxTotalConnections());
313 putDefaultIntegerProperty(CommonClientConfigKey.ConnectTimeout, getDefaultConnectTimeout());
314 putDefaultIntegerProperty(CommonClientConfigKey.ConnectionManagerTimeout, getDefaultConnectionManagerTimeout());
315 putDefaultIntegerProperty(CommonClientConfigKey.ReadTimeout, getDefaultReadTimeout());
316 putDefaultIntegerProperty(CommonClientConfigKey.MaxAutoRetries, getDefaultMaxAutoRetries());
317 putDefaultIntegerProperty(CommonClientConfigKey.MaxAutoRetriesNextServer, getDefaultMaxAutoRetriesNextServer());
318 putDefaultBooleanProperty(CommonClientConfigKey.OkToRetryOnAllOperations, getDefaultOkToRetryOnAllOperations());
319 putDefaultBooleanProperty(CommonClientConfigKey.FollowRedirects, getDefaultFollowRedirects());
320 putDefaultBooleanProperty(CommonClientConfigKey.ConnectionPoolCleanerTaskEnabled, getDefaultConnectionPoolCleanerTaskEnabled());
321 putDefaultIntegerProperty(CommonClientConfigKey.ConnIdleEvictTimeMilliSeconds, getDefaultConnectionidleTimeInMsecs());
322 putDefaultIntegerProperty(CommonClientConfigKey.ConnectionCleanerRepeatInterval, getDefaultConnectionIdleTimertaskRepeatInMsecs());
323 putDefaultBooleanProperty(CommonClientConfigKey.EnableGZIPContentEncodingFilter, getDefaultEnableGzipContentEncodingFilter());
324 String proxyHost = ConfigurationManager.getConfigInstance().getString(getDefaultPropName(CommonClientConfigKey.ProxyHost.key()));
325 if (proxyHost != null && proxyHost.length() > 0) {
326 setProperty(CommonClientConfigKey.ProxyHost, proxyHost);
327 }
328 Integer proxyPort = ConfigurationManager
329 .getConfigInstance()
330 .getInteger(
331 getDefaultPropName(CommonClientConfigKey.ProxyPort),
332 (Integer.MIN_VALUE + 1)); // + 1 just to avoid potential clash with user setting
333 if (proxyPort != (Integer.MIN_VALUE + 1)) {
334 setProperty(CommonClientConfigKey.ProxyPort, proxyPort);
335 }
336 putDefaultIntegerProperty(CommonClientConfigKey.Port, getDefaultPort());
337 putDefaultBooleanProperty(CommonClientConfigKey.EnablePrimeConnections, getDefaultEnablePrimeConnections());
338 putDefaultIntegerProperty(CommonClientConfigKey.MaxRetriesPerServerPrimeConnection, getDefaultMaxRetriesPerServerPrimeConnection());
339 putDefaultIntegerProperty(CommonClientConfigKey.MaxTotalTimeToPrimeConnections, getDefaultMaxTotalTimeToPrimeConnections());
340 putDefaultStringProperty(CommonClientConfigKey.PrimeConnectionsURI, getDefaultPrimeConnectionsUri());
341 putDefaultIntegerProperty(CommonClientConfigKey.PoolMinThreads, getDefaultPoolMinThreads());
342 putDefaultIntegerProperty(CommonClientConfigKey.PoolMaxThreads, getDefaultPoolMaxThreads());
343 putDefaultLongProperty(CommonClientConfigKey.PoolKeepAliveTime, getDefaultPoolKeepAliveTime());
344 putDefaultTimeUnitProperty(CommonClientConfigKey.PoolKeepAliveTimeUnits, getDefaultPoolKeepAliveTimeUnits());
345 putDefaultBooleanProperty(CommonClientConfigKey.EnableZoneAffinity, getDefaultEnableZoneAffinity());
346 putDefaultBooleanProperty(CommonClientConfigKey.EnableZoneExclusivity, getDefaultEnableZoneExclusivity());
347 putDefaultStringProperty(CommonClientConfigKey.ClientClassName, getDefaultClientClassname());
348 putDefaultStringProperty(CommonClientConfigKey.NFLoadBalancerClassName, getDefaultNfloadbalancerClassname());
349 putDefaultStringProperty(CommonClientConfigKey.NFLoadBalancerRuleClassName, getDefaultNfloadbalancerRuleClassname());
350 putDefaultStringProperty(CommonClientConfigKey.NFLoadBalancerPingClassName, getDefaultNfloadbalancerPingClassname());
351 putDefaultBooleanProperty(CommonClientConfigKey.PrioritizeVipAddressBasedServers, getDefaultPrioritizeVipAddressBasedServers());
352 putDefaultFloatProperty(CommonClientConfigKey.MinPrimeConnectionsRatio, getDefaultMinPrimeConnectionsRatio());
353 putDefaultStringProperty(CommonClientConfigKey.PrimeConnectionsClassName, getDefaultPrimeConnectionsClass());
354 putDefaultStringProperty(CommonClientConfigKey.NIWSServerListClassName, getDefaultSeverListClass());
355 putDefaultStringProperty(CommonClientConfigKey.VipAddressResolverClassName, getDefaultVipaddressResolverClassname());
356 putDefaultBooleanProperty(CommonClientConfigKey.IsClientAuthRequired, getDefaultIsClientAuthRequired());
357 // putDefaultStringProperty(CommonClientConfigKey.RequestIdHeaderName, getDefaultRequestIdHeaderName());
358 putDefaultBooleanProperty(CommonClientConfigKey.UseIPAddrForServer, getDefaultUseIpAddressForServer());
359 putDefaultStringProperty(CommonClientConfigKey.ListOfServers, "");
360 }
361 }
也可以在配置文件中定制配置，例如配置超时和重试：
1 # 全局配置
2 ribbon:
3 # 客户端读取超时时间
4 ReadTimeout: 3000
5 # 客户端连接超时时间
6 ConnectTimeout: 3000
7 # 默认只重试 GET，设置为 true 时将重试所有类型，如 POST、PUT、DELETE
8 OkToRetryOnAllOperations: false
9 # 重试次数
10 MaxAutoRetries: 1
11 # 最多重试几个实例
12 MaxAutoRetriesNextServer: 1
13
14 # 只针对 demo-producer 客户端
15 demo-producer:
16 ribbon:
17 # 客户端读取超时时间
18 ReadTimeout: 5000
19 # 客户端连接超时时间
20 ConnectTimeout: 3000
2、均衡策略 — IRule
IRule 是最终选择 Server 的策略规则类，核心的接口就是 choose。
1 public interface IRule{
2
3 // 选择 Server
4 public Server choose(Object key);
5
6 // 设置 ILoadBalancer
7 public void setLoadBalancer(ILoadBalancer lb);
8
9 // 获取 ILoadBalancer
10 public ILoadBalancer getLoadBalancer();
11 }
Ribbon 提供了丰富的负载均衡策略，我们也可以通过配置指定使用某个均衡策略。下面是整个Ribbon提供的 IRule 均衡策略。
3、服务检查 — IPing
IPing 是用于定期检查 Server 的可用性的，它只提供了一个接口，用来判断 Server 是否存活：
1 public interface IPing {
2
3 public boolean isAlive(Server server);
4 }
IPing 也提供了多种策略可选，下面是整个 IPing 体系结构：
4、获取服务列表 — ServerList
ServerList 提供了两个接口，一个是第一次获取 Server 列表，一个是更新 Server 列表，其中 getUpdatedListOfServers 会每被 Loadbalancer 隔 30 秒调一次来更新 allServerList。
1 public interface ServerList<T extends Server> {
2
3 public List<T> getInitialListOfServers();
4
5 /**
6 * Return updated list of servers. This is called say every 30 secs
7 * (configurable) by the Loadbalancer's Ping cycle
8 */
9 public List<T> getUpdatedListOfServers();
10 }
ServerList 也提供了多种实现，ServerList 体系结构如下：
5、过滤服务 — ServerListFilter
ServerListFilter 提供了一个接口用来过滤出可用的 Server。
1 public interface ServerListFilter<T extends Server> {
2
3 public List<T> getFilteredListOfServers(List<T> servers);
4 }
ServerListFilter 体系结构如下：
6、服务列表更新 — ServerListUpdater
ServerListUpdater 有多个接口，最核心的就是 start 开启定时任务调用 updateAction 来更新 allServerList。
1 public interface ServerListUpdater {
2
3 /**
4 * an interface for the updateAction that actually executes a server list update
5 */
6 public interface UpdateAction {
7 void doUpdate();
8 }
9
10 /**
11 * start the serverList updater with the given update action
12 * This call should be idempotent.
13 */
14 void start(UpdateAction updateAction);
15 }
默认有两个实现类：
7、负载均衡器 — ILoadBalancer
ILoadBalancer 是负载均衡选择服务的核心接口，主要提供了如下的获取Server列表和根据客户端名称选择Server的接口。
1 public interface ILoadBalancer {
2
3 // 添加Server
4 public void addServers(List<Server> newServers);
5
6 // 根据key选择一个Server
7 public Server chooseServer(Object key);
8
9 // 获取存活的Server列表，返回 upServerList
10 public List<Server> getReachableServers();
11
12 // 获取所有Server列表，返回 allServerList
13 public List<Server> getAllServers();
14 }
ILoadBalancer 的体系结构如下：
8、Ribbon 相关配置类
从前面一直看下来，可以发现有很多与 Ribbon 相关的配置类，这里总结下与 Ribbon 相关的配置类，看每个配置类的配置顺序，以及都主要配置了哪些东西。
① 首先是Eureka客户端配置类 EurekaClientAutoConfiguration，这个自动化配置类主要配置了 Ribbon 所需的 EurekaClient。
1 @Configuration(proxyBeanMethods = false)
2 @EnableConfigurationProperties
3 @ConditionalOnClass(EurekaClientConfig.class)
4 @ConditionalOnProperty(value = "eureka.client.enabled", matchIfMissing = true)
5 @ConditionalOnDiscoveryEnabled
6 @AutoConfigureBefore({ NoopDiscoveryClientAutoConfiguration.class,
7 CommonsClientAutoConfiguration.class, ServiceRegistryAutoConfiguration.class })
8 @AutoConfigureAfter(name = {
9 "org.springframework.cloud.netflix.eureka.config.DiscoveryClientOptionalArgsConfiguration",
10 "org.springframework.cloud.autoconfigure.RefreshAutoConfiguration",
11 "org.springframework.cloud.netflix.eureka.EurekaDiscoveryClientConfiguration",
12 "org.springframework.cloud.client.serviceregistry.AutoServiceRegistrationAutoConfiguration" })
13 public class EurekaClientAutoConfiguration {
14 // ....
15 }
② 接着是Ribbon自动化配置类 RibbonAutoConfiguration，这个类主要配置了如下类：
- SpringClientFactory：管理 Ribbon 客户端上下文。
- LoadBalancerClient：负载均衡客户端，默认实现类为 RibbonLoadBalancerClient（实际是在 RibbonClientConfiguration 中配置的）。
- PropertiesFactory：用于判断配置文件中是否自定义了核心接口的实现类，如 NFLoadBalancerClassName、NFLoadBalancerPingClassName 等。
- RibbonApplicationContextInitializer：开启饥饿配置的时候，用这个类来在启动时初始化 Ribbon 客户端上下文。
1 package org.springframework.cloud.netflix.ribbon;
2
3 @Configuration
4 @Conditional(RibbonAutoConfiguration.RibbonClassesConditions.class)
5 @RibbonClients
6 // 在 EurekaClientAutoConfiguration 之后配置
7 @AutoConfigureAfter(name = "org.springframework.cloud.netflix.eureka.EurekaClientAutoConfiguration")
8 // 在 LoadBalancerAutoConfiguration、AsyncLoadBalancerAutoConfiguration 之前配置
9 @AutoConfigureBefore({ LoadBalancerAutoConfiguration.class, AsyncLoadBalancerAutoConfiguration.class })
10 @EnableConfigurationProperties({ RibbonEagerLoadProperties.class, ServerIntrospectorProperties.class })
11 public class RibbonAutoConfiguration {
12
13 @Autowired(required = false)
14 private List<RibbonClientSpecification> configurations = new ArrayList<>();
15
16 @Autowired
17 private RibbonEagerLoadProperties ribbonEagerLoadProperties;
18
19 @Bean
20 public HasFeatures ribbonFeature() {
21 return HasFeatures.namedFeature("Ribbon", Ribbon.class);
22 }
23
24 @Bean
25 @ConditionalOnMissingBean
26 public SpringClientFactory springClientFactory() {
27 SpringClientFactory factory = new SpringClientFactory();
28 factory.setConfigurations(this.configurations);
29 return factory;
30 }
31
32 @Bean
33 @ConditionalOnMissingBean(LoadBalancerClient.class)
34 public LoadBalancerClient loadBalancerClient() {
35 return new RibbonLoadBalancerClient(springClientFactory());
36 }
37
38 @Bean
39 @ConditionalOnClass(name = "org.springframework.retry.support.RetryTemplate")
40 @ConditionalOnMissingBean
41 public LoadBalancedRetryFactory loadBalancedRetryPolicyFactory(final SpringClientFactory clientFactory) {
42 return new RibbonLoadBalancedRetryFactory(clientFactory);
43 }
44
45 @Bean
46 @ConditionalOnMissingBean
47 public PropertiesFactory propertiesFactory() {
48 return new PropertiesFactory();
49 }
50
51 @Bean
52 @ConditionalOnProperty("ribbon.eager-load.enabled")
53 public RibbonApplicationContextInitializer ribbonApplicationContextInitializer() {
54 return new RibbonApplicationContextInitializer(springClientFactory(), ribbonEagerLoadProperties.getClients());
55 }
56 }
③ 接着是负载均衡器配置类 LoadBalancerAutoConfiguration，这个类主要是创建了负载均衡拦截器 LoadBalancerInterceptor，并添加到 RestTemplae 的拦截器中。
1 package org.springframework.cloud.client.loadbalancer;
2
3 @Configuration(proxyBeanMethods = false)
4 @ConditionalOnClass(RestTemplate.class)
5 @ConditionalOnBean(LoadBalancerClient.class)
6 @EnableConfigurationProperties(LoadBalancerRetryProperties.class)
7 public class LoadBalancerAutoConfiguration {
8
9 @LoadBalanced
10 @Autowired(required = false)
11 private List<RestTemplate> restTemplates = Collections.emptyList();
12
13 @Autowired(required = false)
14 private List<LoadBalancerRequestTransformer> transformers = Collections.emptyList();
15
16 // 对 RestTemplate 定制化
17 @Bean
18 public SmartInitializingSingleton loadBalancedRestTemplateInitializerDeprecated(
19 final ObjectProvider<List<RestTemplateCustomizer>> restTemplateCustomizers) {
20 return () -> restTemplateCustomizers.ifAvailable(customizers -> {
21 for (RestTemplate restTemplate : LoadBalancerAutoConfiguration.this.restTemplates) {
22 for (RestTemplateCustomizer customizer : customizers) {
23 customizer.customize(restTemplate);
24 }
25 }
26 });
27 }
28
29 @Bean
30 @ConditionalOnMissingBean
31 public LoadBalancerRequestFactory loadBalancerRequestFactory(LoadBalancerClient loadBalancerClient) {
32 return new LoadBalancerRequestFactory(loadBalancerClient, this.transformers);
33 }
34
35 @Configuration(proxyBeanMethods = false)
36 @ConditionalOnMissingClass("org.springframework.retry.support.RetryTemplate")
37 static class LoadBalancerInterceptorConfig {
38
39 // 创建 RestTemplate 拦截器
40 @Bean
41 public LoadBalancerInterceptor ribbonInterceptor(LoadBalancerClient loadBalancerClient,
42 LoadBalancerRequestFactory requestFactory) {
43 return new LoadBalancerInterceptor(loadBalancerClient, requestFactory);
44 }
45
46 @Bean
47 @ConditionalOnMissingBean
48 public RestTemplateCustomizer restTemplateCustomizer(final LoadBalancerInterceptor loadBalancerInterceptor) {
49 return restTemplate -> {
50 List<ClientHttpRequestInterceptor> list = new ArrayList<>(
51 restTemplate.getInterceptors());
52 list.add(loadBalancerInterceptor);
53 restTemplate.setInterceptors(list);
54 };
55 }
56
57 }
58 }
④ 之后是默认的 Ribbon 客户端配置类 RibbonClientConfiguration，这个类主要配置了 Ribbon 核心接口的默认实现。
- IClientConfig：Ribbon 客户端配置类，默认实现是 DefaultClientConfigImpl。
- IRule：负载均衡策略规则组件，默认实现是 ZoneAvoidanceRule。
- IPing：判断 Server 是否存活，默认实现是 DummyPing，永远都是返回 true。
- ServerList：获取 Server 的组件，默认实现类为 ConfigurationBasedServerList，从配置文件获取。
- ServerListUpdater：Server 列表更新组件，默认实现类为 PollingServerListUpdater。
- ServerListFilter：过滤可用的 Server 列表，默认实现类为 ZonePreferenceServerListFilter。
- RibbonLoadBalancerContext：负载均衡客户端。
- RetryHandler：重试处理器，默认实现类为 DefaultLoadBalancerRetryHandler。
1 package org.springframework.cloud.netflix.ribbon;
2
3 @SuppressWarnings("deprecation")
4 @Configuration(proxyBeanMethods = false)
5 @EnableConfigurationProperties
6 @Import({ HttpClientConfiguration.class, OkHttpRibbonConfiguration.class,
7 RestClientRibbonConfiguration.class, HttpClientRibbonConfiguration.class })
8 public class RibbonClientConfiguration {
9 public static final int DEFAULT_CONNECT_TIMEOUT = 1000;
10 public static final int DEFAULT_READ_TIMEOUT = 1000;
11 public static final boolean DEFAULT_GZIP_PAYLOAD = true;
12
13 @RibbonClientName
14 private String name = "client";
15
16 @Autowired
17 private PropertiesFactory propertiesFactory;
18
19 @Bean
20 @ConditionalOnMissingBean
21 public IClientConfig ribbonClientConfig() {
22 DefaultClientConfigImpl config = new DefaultClientConfigImpl();
23 config.loadProperties(this.name);
24 config.set(CommonClientConfigKey.ConnectTimeout, DEFAULT_CONNECT_TIMEOUT);
25 config.set(CommonClientConfigKey.ReadTimeout, DEFAULT_READ_TIMEOUT);
26 config.set(CommonClientConfigKey.GZipPayload, DEFAULT_GZIP_PAYLOAD);
27 return config;
28 }
29
30 @Bean
31 @ConditionalOnMissingBean
32 public IRule ribbonRule(IClientConfig config) {
33 if (this.propertiesFactory.isSet(IRule.class, name)) {
34 return this.propertiesFactory.get(IRule.class, config, name);
35 }
36 ZoneAvoidanceRule rule = new ZoneAvoidanceRule();
37 rule.initWithNiwsConfig(config);
38 return rule;
39 }
40
41 @Bean
42 @ConditionalOnMissingBean
43 public IPing ribbonPing(IClientConfig config) {
44 if (this.propertiesFactory.isSet(IPing.class, name)) {
45 return this.propertiesFactory.get(IPing.class, config, name);
46 }
47 return new DummyPing();
48 }
49
50 @Bean
51 @ConditionalOnMissingBean
52 @SuppressWarnings("unchecked")
53 public ServerList<Server> ribbonServerList(IClientConfig config) {
54 if (this.propertiesFactory.isSet(ServerList.class, name)) {
55 return this.propertiesFactory.get(ServerList.class, config, name);
56 }
57 ConfigurationBasedServerList serverList = new ConfigurationBasedServerList();
58 serverList.initWithNiwsConfig(config);
59 return serverList;
60 }
61
62 @Bean
63 @ConditionalOnMissingBean
64 public ServerListUpdater ribbonServerListUpdater(IClientConfig config) {
65 return new PollingServerListUpdater(config);
66 }
67
68 @Bean
69 @ConditionalOnMissingBean
70 public ILoadBalancer ribbonLoadBalancer(IClientConfig config,
71 ServerList<Server> serverList, ServerListFilter<Server> serverListFilter,
72 IRule rule, IPing ping, ServerListUpdater serverListUpdater) {
73 if (this.propertiesFactory.isSet(ILoadBalancer.class, name)) {
74 return this.propertiesFactory.get(ILoadBalancer.class, config, name);
75 }
76 return new ZoneAwareLoadBalancer<>(config, rule, ping, serverList,
77 serverListFilter, serverListUpdater);
78 }
79
80 @Bean
81 @ConditionalOnMissingBean
82 @SuppressWarnings("unchecked")
83 public ServerListFilter<Server> ribbonServerListFilter(IClientConfig config) {
84 if (this.propertiesFactory.isSet(ServerListFilter.class, name)) {
85 return this.propertiesFactory.get(ServerListFilter.class, config, name);
86 }
87 ZonePreferenceServerListFilter filter = new ZonePreferenceServerListFilter();
88 filter.initWithNiwsConfig(config);
89 return filter;
90 }
91
92 @Bean
93 @ConditionalOnMissingBean
94 public RibbonLoadBalancerContext ribbonLoadBalancerContext(ILoadBalancer loadBalancer,
95 IClientConfig config, RetryHandler retryHandler) {
96 return new RibbonLoadBalancerContext(loadBalancer, config, retryHandler);
97 }
98
99 @Bean
100 @ConditionalOnMissingBean
101 public RetryHandler retryHandler(IClientConfig config) {
102 return new DefaultLoadBalancerRetryHandler(config);
103 }
104
105 @Bean
106 @ConditionalOnMissingBean
107 public ServerIntrospector serverIntrospector() {
108 return new DefaultServerIntrospector();
109 }
110 }
⑤ Ribbon Eureka 自动化配置类 RibbonEurekaAutoConfiguration，判断是否启用 Ribbon Eureka，并触发 EurekaRibbonClientConfiguration 配置类。
1 package org.springframework.cloud.netflix.ribbon.eureka;
2
3 @Configuration(proxyBeanMethods = false)
4 @EnableConfigurationProperties
5 @ConditionalOnRibbonAndEurekaEnabled
6 @AutoConfigureAfter(RibbonAutoConfiguration.class)
7 @RibbonClients(defaultConfiguration = EurekaRibbonClientConfiguration.class)
8 public class RibbonEurekaAutoConfiguration {
9
10 }
⑥ 默认启用 Ribbon Eureka 的情况下，会使用 Ribbon Eureka 客户端配置类 EurekaRibbonClientConfiguration：
- IPing：替换了默认实现类 DummyPing，改为 NIWSDiscoveryPing，通过判断 InstanceInfo 的状态是否为 UP 来判断 Server 是否存活。
- ServerList：替换了默认的实现类 ConfigurationBasedServerList，改为 DomainExtractingServerList，实际是 DiscoveryEnabledNIWSServerList，从 EurekaClient 获取 Server 列表。
1 package org.springframework.cloud.netflix.ribbon.eureka;
2
3 @Configuration(proxyBeanMethods = false)
4 public class EurekaRibbonClientConfiguration {
5
6 private static final Log log = LogFactory.getLog(EurekaRibbonClientConfiguration.class);
7
8 @Value("${ribbon.eureka.approximateZoneFromHostname:false}")
9 private boolean approximateZoneFromHostname = false;
10 @RibbonClientName
11 private String serviceId = "client";
12 @Autowired(required = false)
13 private EurekaClientConfig clientConfig;
14 @Autowired(required = false)
15 private EurekaInstanceConfig eurekaConfig;
16 @Autowired
17 private PropertiesFactory propertiesFactory;
18
19 public EurekaRibbonClientConfiguration() {
20 }
21
22 public EurekaRibbonClientConfiguration(EurekaClientConfig clientConfig,
23 String serviceId, EurekaInstanceConfig eurekaConfig,
24 boolean approximateZoneFromHostname) {
25 this.clientConfig = clientConfig;
26 this.serviceId = serviceId;
27 this.eurekaConfig = eurekaConfig;
28 this.approximateZoneFromHostname = approximateZoneFromHostname;
29 }
30
31 @Bean
32 @ConditionalOnMissingBean
33 public IPing ribbonPing(IClientConfig config) {
34 if (this.propertiesFactory.isSet(IPing.class, serviceId)) {
35 return this.propertiesFactory.get(IPing.class, config, serviceId);
36 }
37 NIWSDiscoveryPing ping = new NIWSDiscoveryPing();
38 ping.initWithNiwsConfig(config);
39 return ping;
40 }
41
42 @Bean
43 @ConditionalOnMissingBean
44 public ServerList<?> ribbonServerList(IClientConfig config, Provider<EurekaClient> eurekaClientProvider) {
45 if (this.propertiesFactory.isSet(ServerList.class, serviceId)) {
46 return this.propertiesFactory.get(ServerList.class, config, serviceId);
47 }
48 DiscoveryEnabledNIWSServerList discoveryServerList = new DiscoveryEnabledNIWSServerList(
49 config, eurekaClientProvider);
50 DomainExtractingServerList serverList = new DomainExtractingServerList(
51 discoveryServerList, config, this.approximateZoneFromHostname);
52 return serverList;
53 }
54 }
⑦ 各个配置类所属模块
spring-cloud-netflix-eureka-client：
- org.springframework.cloud.netflix.eureka.EurekaClientAutoConfiguration
- org.springframework.cloud.netflix.ribbon.eureka.RibbonEurekaAutoConfiguration
- org.springframework.cloud.netflix.ribbon.eureka.EurekaRibbonClientConfiguration
spring-cloud-netflix-ribbon：
- org.springframework.cloud.netflix.ribbon.RibbonAutoConfiguration
- org.springframework.cloud.netflix.ribbon.RibbonClientConfiguration
spring-cloud-commons：
- org.springframework.cloud.client.loadbalancer.LoadBalancerAutoConfiguration
六、Ribbon HTTP客户端组件
1、Java HTTP 组件库
① HTTP 组件库
首先简单了解下常用的 Java HTTP 组件库，Ribbon 中通过不同的配置便可以启用某个 HTTP 组件来进行服务间的通信。
Java 中的 HTTP 组件库，大体可以分为三类：
- JDK 自带的标准库 HttpURLConnection
- Apache HttpComponents HttpClient
- OkHttp
HttpURLConnection 发起 HTTP 请求最大的优点是不需要引入额外的依赖，但是 HttpURLConnection 封装层次太低，使用起来非常繁琐。支持的特性太少，缺乏连接池管理、域名机械控制，无法支持 HTTP/2等。
Apache HttpComponents HttpClient 和 OkHttp 都支持连接池管理、超时、空闲连接数控制等特性。OkHttp 接口设计更友好，且支持 HTTP/2，Android 开发中用得更多。
② 超时重试配置
先给 demo-consumer 中添加如下默认配置，即读取、连接超时时间设置为 1 秒，这也是默认值。然后重试次数为1，重试一个Server。后面基于这些配置来验证Ribbon HTTP客户端的超时和重试。
1 ribbon:
2 # 客户端读取超时时间
3 ReadTimeout: 1000
4 # 客户端连接超时时间
5 ConnectTimeout: 1000
6 # 默认只重试 GET，设置为 true 时将重试所有类型，如 POST、PUT、DELETE
7 OkToRetryOnAllOperations: false
8 # 重试次数
9 MaxAutoRetries: 1
10 # 最多重试几个实例
11 MaxAutoRetriesNextServer: 1
然后 demo-producer 的接口休眠3秒，造成网络延迟的现象，并且 demo-producer 启两个实例。
1 @GetMapping("/v1/uuid")
2 public ResponseEntity<String> getUUID() throws InterruptedException {
3 String uuid = UUID.randomUUID().toString();
4 logger.info("generate uuid: {}", uuid);
5 Thread.sleep(3000);
6 return ResponseEntity.ok(uuid);
7 }
2、Ribbon 默认使用 HttpURLConnection
① Ribbon 默认的 HTTP 组件
在不添加其它配置的情况下，我们来看下 Ribbon 默认使用的 HTTP 组件是什么。
首先通过之前的分析可以知道，默认情况下，LoadBalancerAutoConfiguration 配置类会向 RestTemplate 添加 LoadBalancerInterceptor 拦截器。然后在 RestTemplate 调用时，即在 doExecute 方法中，创建 ClientHttpRequest 时，因为配置了拦截器，所以 ClientHttpRequestFactory 就是 InterceptingClientHttpRequestFactory，而且创建 InterceptingClientHttpRequestFactory 传入的 ClientHttpRequestFactory 默认是父类的 SimpleClientHttpRequestFactory。
1 protected <T> T doExecute(URI url, @Nullable HttpMethod method, @Nullable RequestCallback requestCallback,
2 @Nullable ResponseExtractor<T> responseExtractor) throws RestClientException {
3 //...
4 ClientHttpResponse response = null;
5 try {
6 // 创建 ClientHttpRequest
7 ClientHttpRequest request = createRequest(url, method);
8 if (requestCallback != null) {
9 requestCallback.doWithRequest(request);
10 }
11 // ClientHttpRequest 发起请求
12 response = request.execute();
13 handleResponse(url, method, response);
14 return (responseExtractor != null ? responseExtractor.extractData(response) : null);
15 }
16 catch (IOException ex) {
17 // ...
18 }
19 finally {
20 if (response != null) {
21 response.close();
22 }
23 }
24 }
25
26 protected ClientHttpRequest createRequest(URI url, HttpMethod method) throws IOException {
27 // getRequestFactory 获取 ClientHttpRequestFactory
28 ClientHttpRequest request = getRequestFactory().createRequest(url, method);
29 initialize(request);
30 if (logger.isDebugEnabled()) {
31 logger.debug("HTTP " + method.name() + " " + url);
32 }
33 return request;
34 }
35
36 public ClientHttpRequestFactory getRequestFactory() {
37 List<ClientHttpRequestInterceptor> interceptors = getInterceptors();
38 if (!CollectionUtils.isEmpty(interceptors)) {
39 ClientHttpRequestFactory factory = this.interceptingRequestFactory;
40 if (factory == null) {
41 // 有拦截器的情况，super.getRequestFactory() 默认返回的是 SimpleClientHttpRequestFactory
42 factory = new InterceptingClientHttpRequestFactory(super.getRequestFactory(), interceptors);
43 this.interceptingRequestFactory = factory;
44 }
45 return factory;
46 }
47 else {
48 // 无拦截器的情况
49 return super.getRequestFactory();
50 }
51 }
InterceptingClientHttpRequestFactory 这个工厂类创建的 ClientHttpRequest 类型是 InterceptingClientHttpRequest。最终 RestTemplate 的 doExecute 方法中调用 ClientHttpRequest 的 execute 方法时，就调用到了 InterceptingClientHttpRequest 中的内部类 InterceptingRequestExecution 中。
在 InterceptingRequestExecution 的 execute 方法中，首先是遍历所有拦截器对 RestTemplate 定制化，最后则通过 requestFactory 创建 ClientHttpRequest 来发起最终的 HTTP 调用。从这里可以看出，无论有没有拦截器，其实最终都会使用 requestFactory 来创建 ClientHttpRequest。
1 private class InterceptingRequestExecution implements ClientHttpRequestExecution {
2 private final Iterator<ClientHttpRequestInterceptor> iterator;
3
4 @Override
5 public ClientHttpResponse execute(HttpRequest request, byte[] body) throws IOException {
6 if (this.iterator.hasNext()) {
7 // 拦截器定制化 RestTemplate
8 ClientHttpRequestInterceptor nextInterceptor = this.iterator.next();
9 return nextInterceptor.intercept(request, body, this);
10 }
11 else {
12 HttpMethod method = request.getMethod();
13 // delegate => SimpleBufferingClientHttpRequest
14 ClientHttpRequest delegate = requestFactory.createRequest(request.getURI(), method);
15 //...
16 return delegate.execute();
17 }
18 }
19 }
这里的 requestFactory 就是前面传进来的 SimpleClientHttpRequestFactory，从它的 createRequest 方法可以看出，默认情况下，就是用的 JDK 标准 HTTP 库组件 HttpURLConnection 来进行服务间的请求通信。
1 public ClientHttpRequest createRequest(URI uri, HttpMethod httpMethod) throws IOException {
2 // JDK 标准HTTP库 HttpURLConnection
3 HttpURLConnection connection = openConnection(uri.toURL(), this.proxy);
4 prepareConnection(connection, httpMethod.name());
5
6 if (this.bufferRequestBody) {
7 return new SimpleBufferingClientHttpRequest(connection, this.outputStreaming);
8 }
9 else {
10 return new SimpleStreamingClientHttpRequest(connection, this.chunkSize, this.outputStreaming);
11 }
12 }
总结：
从前面的源码分析可以看出，Ribbon 默认的 HTTP 客户端是 HttpURLConnection。
在前面默认的超时配置下，可以验证出超时配置并未生效，一直阻塞3秒后才返回了结果，说明 Ribbon 默认情况下就不支持超时重试。
而且 HttpURLConnection 每次都是新创建的，请求返回来之后就关闭连接，没有连接池管理机制，网络连接的建立和关闭本身就会损耗一定的性能，所以正式环境下，最好不要使用默认的配置。
② HttpClient 配置类
另外，我们从 RibbonClientConfiguration 配置类的定义可以看到，其导入了 HttpClientConfiguration、OkHttpRibbonConfiguration、RestClientRibbonConfiguration、HttpClientRibbonConfiguration 四个 HttpClient 的配置类，通过注释也可以了解到，最后一个是默认配置类，前面三个在某些配置启用的情况下才会生效。
1 @Configuration(proxyBeanMethods = false)
2 @EnableConfigurationProperties
3 // Order is important here, last should be the default, first should be optional
4 @Import({ HttpClientConfiguration.class, OkHttpRibbonConfiguration.class,
5 RestClientRibbonConfiguration.class, HttpClientRibbonConfiguration.class })
6 public class RibbonClientConfiguration {
7
8 }
进入 HttpClientRibbonConfiguration，这个配置类在 ribbon.httpclient.enabled=true 时才生效，而且默认为 true。在从 SpringClientFactory 中获取 ILoadBalancer 时，会通过这个配置类初始化 HttpClient，按先后顺序会初始化 HttpClientConnectionManager、CloseableHttpClient、RibbonLoadBalancingHttpClient。CloseableHttpClient 是 Apache HttpComponents HttpClient 中的组件，也就是说默认情况下应该是使用 apache HttpComponents 作为 HTTP 组件库。
但经过前面源码的分析，以及测试发现，最终其实走的的 HttpURLConnection，并没有用到 CloseableHttpClient。把 ribbon.httpclient.enabled 设置为 false，也没有什么影响，还是默认走 HttpURLConnection。我们后面再来分析这个问题。
1 @Configuration(proxyBeanMethods = false)
2 @ConditionalOnClass(name = "org.apache.http.client.HttpClient")
3 // ribbon.httpclient.enabled more文为 true
4 @ConditionalOnProperty(name = "ribbon.httpclient.enabled", matchIfMissing = true)
5 public class HttpClientRibbonConfiguration {
6
7 @RibbonClientName
8 private String name = "client";
9
10 // RibbonLoadBalancingHttpClient
11 @Bean
12 @ConditionalOnMissingBean(AbstractLoadBalancerAwareClient.class)
13 @ConditionalOnMissingClass("org.springframework.retry.support.RetryTemplate")
14 public RibbonLoadBalancingHttpClient ribbonLoadBalancingHttpClient(
15 IClientConfig config, ServerIntrospector serverIntrospector,
16 ILoadBalancer loadBalancer, RetryHandler retryHandler,
17 CloseableHttpClient httpClient) {
18 RibbonLoadBalancingHttpClient client = new RibbonLoadBalancingHttpClient(
19 httpClient, config, serverIntrospector);
20 client.setLoadBalancer(loadBalancer);
21 client.setRetryHandler(retryHandler);
22 Monitors.registerObject("Client_" + this.name, client);
23 return client;
24 }
25
26 // 在引入了 spring-retry 时，即可以重试的 RetryTemplate 时，就创建 RetryableRibbonLoadBalancingHttpClient
27 @Bean
28 @ConditionalOnMissingBean(AbstractLoadBalancerAwareClient.class)
29 @ConditionalOnClass(name = "org.springframework.retry.support.RetryTemplate")
30 public RetryableRibbonLoadBalancingHttpClient retryableRibbonLoadBalancingHttpClient(
31 IClientConfig config, ServerIntrospector serverIntrospector,
32 ILoadBalancer loadBalancer, RetryHandler retryHandler,
33 LoadBalancedRetryFactory loadBalancedRetryFactory,
34 CloseableHttpClient httpClient,
35 RibbonLoadBalancerContext ribbonLoadBalancerContext) {
36 RetryableRibbonLoadBalancingHttpClient client = new RetryableRibbonLoadBalancingHttpClient(
37 httpClient, config, serverIntrospector, loadBalancedRetryFactory);
38 client.setLoadBalancer(loadBalancer);
39 client.setRetryHandler(retryHandler);
40 client.setRibbonLoadBalancerContext(ribbonLoadBalancerContext);
41 Monitors.registerObject("Client_" + this.name, client);
42 return client;
43 }
44
45 @Configuration(proxyBeanMethods = false)
46 protected static class ApacheHttpClientConfiguration {
47
48 private final Timer connectionManagerTimer = new Timer(
49 "RibbonApacheHttpClientConfiguration.connectionManagerTimer", true);
50
51 private CloseableHttpClient httpClient;
52
53 @Autowired(required = false)
54 private RegistryBuilder registryBuilder;
55
56 // HttpClient 连接池管理器
57 @Bean
58 @ConditionalOnMissingBean(HttpClientConnectionManager.class)
59 public HttpClientConnectionManager httpClientConnectionManager(
60 IClientConfig config,
61 ApacheHttpClientConnectionManagerFactory connectionManagerFactory) {
62 RibbonProperties ribbon = RibbonProperties.from(config);
63 int maxTotalConnections = ribbon.maxTotalConnections();
64 int maxConnectionsPerHost = ribbon.maxConnectionsPerHost();
65 int timerRepeat = ribbon.connectionCleanerRepeatInterval();
66 long timeToLive = ribbon.poolKeepAliveTime();
67 TimeUnit ttlUnit = ribbon.getPoolKeepAliveTimeUnits();
68 final HttpClientConnectionManager connectionManager = connectionManagerFactory
69 .newConnectionManager(false, maxTotalConnections,
70 maxConnectionsPerHost, timeToLive, ttlUnit, registryBuilder);
71 this.connectionManagerTimer.schedule(new TimerTask() {
72 @Override
73 public void run() {
74 connectionManager.closeExpiredConnections();
75 }
76 }, 30000, timerRepeat);
77 return connectionManager;
78 }
79
80 // HttpClient => CloseableHttpClient
81 @Bean
82 @ConditionalOnMissingBean(CloseableHttpClient.class)
83 public CloseableHttpClient httpClient(ApacheHttpClientFactory httpClientFactory,
84 HttpClientConnectionManager connectionManager, IClientConfig config) {
85 RibbonProperties ribbon = RibbonProperties.from(config);
86 Boolean followRedirects = ribbon.isFollowRedirects();
87 Integer connectTimeout = ribbon.connectTimeout();
88 RequestConfig defaultRequestConfig = RequestConfig.custom()
89 .setConnectTimeout(connectTimeout)
90 .setRedirectsEnabled(followRedirects).build();
91 this.httpClient = httpClientFactory.createBuilder()
92 .setDefaultRequestConfig(defaultRequestConfig)
93 .setConnectionManager(connectionManager).build();
94 return httpClient;
95 }
96 }
97 }
③ 默认配置下的 RestTemplate 的调用过程大致可以用下图来表示。
3、启用 RestClient
① 启用 RestClient
可以添加如下配置启用 RestClient：
1 ribbon:
2 # 关闭 httpclient
3 httpclient:
4 enabled: false
5 # 启用 RestClient
6 restclient:
7 enabled: true
8 # 启用 RestClient
9 http:
10 client:
11 enabled: true
进入 RestClientRibbonConfiguration 可以看到，只要 ribbon.http.client.enabled、ribbon.restclient.enabled 其中一个配置了启用，就可以启用 RestClient。
1 @SuppressWarnings("deprecation")
2 @Configuration(proxyBeanMethods = false)
3 // 启用条件 ConditionalOnRibbonRestClient
4 @RibbonAutoConfiguration.ConditionalOnRibbonRestClient
5 class RestClientRibbonConfiguration {
6 @RibbonClientName
7 private String name = "client";
8
9 // RestClient 已过期
10 @Bean
11 @Lazy
12 @ConditionalOnMissingBean(AbstractLoadBalancerAwareClient.class)
13 public RestClient ribbonRestClient(IClientConfig config, ILoadBalancer loadBalancer,
14 ServerIntrospector serverIntrospector, RetryHandler retryHandler) {
15 RestClient client = new RibbonClientConfiguration.OverrideRestClient(config, serverIntrospector);
16 client.setLoadBalancer(loadBalancer);
17 client.setRetryHandler(retryHandler);
18 return client;
19 }
20
21 }
22
23 @Target({ ElementType.TYPE, ElementType.METHOD })
24 @Retention(RetentionPolicy.RUNTIME)
25 @Documented
26 @Conditional(OnRibbonRestClientCondition.class)
27 @interface ConditionalOnRibbonRestClient {
28 }
29
30 private static class OnRibbonRestClientCondition extends AnyNestedCondition {
31 @Deprecated // remove in Edgware"
32 @ConditionalOnProperty("ribbon.http.client.enabled")
33 static class ZuulProperty {
34 }
35
36 @ConditionalOnProperty("ribbon.restclient.enabled")
37 static class RibbonProperty {
38 }
39 }
RestClient 继承自 AbstractLoadBalancerAwareClient。需要注意的是，RestClient 已经过期，所以生产环境中我们就不要启用 RestTemplate 了。
1 @Deprecated
2 public class RestClient extends AbstractLoadBalancerAwareClient<HttpRequest, HttpResponse> {
3
4 }
② LoadBalancerContext 类体系结构
负载均衡上下文 LoadBalancerContext 体系的类结构如下。可以看出，Ribbon 是支持 Feign、OkHttp、HttpClient、RestClient 的。默认配置下使用的实现类是 RibbonLoadBalancerContext。
③ RestTemplate 的 ClientHttpRequest 工厂类配置
接着看 RibbonAutoConfiguration 中有如下的配置，跟前面 RestClientRibbonConfiguration 也是一样，满足 @ConditionalOnRibbonRestClient 的条件。
可以看到，它会创建 RibbonClientHttpRequestFactory 并设置到 RestTemplate 中，也就是说，这时 RestTemplate 中的 requestFactory 就不是默认的 SimpleClientHttpRequestFactory 了，而是 RibbonClientHttpRequestFactory。
1 @Configuration(proxyBeanMethods = false)
2 @ConditionalOnClass(HttpRequest.class)
3 @ConditionalOnRibbonRestClient
4 protected static class RibbonClientHttpRequestFactoryConfiguration {
5 @Autowired
6 private SpringClientFactory springClientFactory;
7
8 @Bean
9 public RestTemplateCustomizer restTemplateCustomizer(
10 final RibbonClientHttpRequestFactory ribbonClientHttpRequestFactory) {
11 // RestTemplate 设置 requestFactory 为 RibbonClientHttpRequestFactory
12 return restTemplate -> restTemplate
13 .setRequestFactory(ribbonClientHttpRequestFactory);
14 }
15
16 // ClientHttpRequest 工厂类 => RibbonClientHttpRequestFactory
17 @Bean
18 public RibbonClientHttpRequestFactory ribbonClientHttpRequestFactory() {
19 return new RibbonClientHttpRequestFactory(this.springClientFactory);
20 }
21 }
而且，由于这里配置了 RestTemplateCustomizer，原本默认配置下，在 LoadBalancerAutoConfiguration 中创建 RestTemplateCustomizer 的方法就不会生效了。
LoadBalancerAutoConfiguration 中的 RestTemplateCustomizer 是向 RestTemplate 中添加 LoadBalancerInterceptor 拦截器，所以在启用了 RestClient 的情况下，原本的 LoadBalancerInterceptor 就不会生效了。
1 @Configuration(proxyBeanMethods = false)
2 @ConditionalOnMissingClass("org.springframework.retry.support.RetryTemplate")
3 static class LoadBalancerInterceptorConfig {
4
5 @Bean
6 public LoadBalancerInterceptor ribbonInterceptor(
7 LoadBalancerClient loadBalancerClient,
8 LoadBalancerRequestFactory requestFactory) {
9 return new LoadBalancerInterceptor(loadBalancerClient, requestFactory);
10 }
11
12 @Bean
13 @ConditionalOnMissingBean
14 public RestTemplateCustomizer restTemplateCustomizer(
15 final LoadBalancerInterceptor loadBalancerInterceptor) {
16 return restTemplate -> {
17 List<ClientHttpRequestInterceptor> list = new ArrayList<>(
18 restTemplate.getInterceptors());
19 list.add(loadBalancerInterceptor);
20 restTemplate.setInterceptors(list);
21 };
22 }
23 }
那么 RestTemplate 的 doExecute 方法中，在调用 createRequest 方法创建 ClientHttpRequest 时，就会用 RibbonClientHttpRequestFactory 来创建，进去可以看到 ClientHttpRequest 的实际类型就是 RibbonHttpRequest。
1 public ClientHttpRequest createRequest(URI originalUri, HttpMethod httpMethod) throws IOException {
2 String serviceId = originalUri.getHost();
3 if (serviceId == null) {
4 throw new IOException("Invalid hostname in the URI [" + originalUri.toASCIIString() + "]");
5 }
6 IClientConfig clientConfig = this.clientFactory.getClientConfig(serviceId);
7 RestClient client = this.clientFactory.getClient(serviceId, RestClient.class);
8 HttpRequest.Verb verb = HttpRequest.Verb.valueOf(httpMethod.name());
9
10 return new RibbonHttpRequest(originalUri, verb, client, clientConfig);
11 }
调用 RibbonHttpRequest 的 execute 方法，实际组中是调用了它的 executeInternal 方法，然后最后是使用 RestClient 来发起负载均衡的调用。
1 protected ClientHttpResponse executeInternal(HttpHeaders headers) throws IOException {
2 try {
3 // ...
4 HttpRequest request = builder.build();
5 // client => RestClient
6 HttpResponse response = client.executeWithLoadBalancer(request, config);
7 return new RibbonHttpResponse(response);
8 }
9 catch (Exception e) {
10 throw new IOException(e);
11 }
12 }
④ RestClient HTTP 调用
RestClient 的 executeWithLoadBalancer 实际是进入到父类 AbstractLoadBalancerAwareClient 的 executeWithLoadBalancer 方法中。
从这个方法可以知道，主要的负载均衡请求是在 LoadBalancerCommand 中的，LoadBalancerCommand 必定会通过负载均衡器 ILoadBalancer 得到一个 Server，然后通过 submit 的这个 ServerOperation 对原始URI进行重构，重构之后调用 RestClient 的 execute 发起HTTP请求。
1 public T executeWithLoadBalancer(final S request, final IClientConfig requestConfig) throws ClientException {
2 // 负载均衡命令
3 LoadBalancerCommand<T> command = buildLoadBalancerCommand(request, requestConfig);
4
5 try {
6 // 发起负载均衡请求
7 return command.submit(
8 new ServerOperation<T>() {
9 @Override
10 public Observable<T> call(Server server) {
11 // 重构 URI，将服务名用 Server 的 IP 和端口替换
12 URI finalUri = reconstructURIWithServer(server, request.getUri());
13 S requestForServer = (S) request.replaceUri(finalUri);
14 try {
15 // execute 发起调用，实际调用的是 RestClient 中的 execute
16 return Observable.just(AbstractLoadBalancerAwareClient.this.execute(requestForServer, requestConfig));
17 }
18 catch (Exception e) {
19 return Observable.error(e);
20 }
21 }
22 })
23 .toBlocking()
24 .single();
25 } catch (Exception e) {
26 //....
27 }
28 }
再看 RestClient 的 execute 方法，最终可以发现，RestClient 其实是使用基于 jersey 的 WebResource 来发起 HTTP 请求的。
1 private HttpResponse execute(HttpRequest.Verb verb, URI uri,
2 Map<String, Collection<String>> headers, Map<String, Collection<String>> params,
3 IClientConfig overriddenClientConfig, Object requestEntity) throws Exception {
4 // ...
5 // WebResource 是基于 jersey 封装的 HTTP 客户端组件
6 WebResource xResource = restClient.resource(uri.toString());
7 ClientResponse jerseyResponse;
8 Builder b = xResource.getRequestBuilder();
9 Object entity = requestEntity;
10
11 switch (verb) {
12 case GET:
13 jerseyResponse = b.get(ClientResponse.class);
14 break;
15 case POST:
16 jerseyResponse = b.post(ClientResponse.class, entity);
17 break;
18 case PUT:
19 jerseyResponse = b.put(ClientResponse.class, entity);
20 break;
21 case DELETE:
22 jerseyResponse = b.delete(ClientResponse.class);
23 break;
24 case HEAD:
25 jerseyResponse = b.head();
26 break;
27 case OPTIONS:
28 jerseyResponse = b.options(ClientResponse.class);
29 break;
30 default:
31 throw new ClientException(
32 ClientException.ErrorType.GENERAL,
33 "You have to one of the REST verbs such as GET, POST etc.");
34 }
35
36 thisResponse = new HttpClientResponse(jerseyResponse, uri, overriddenClientConfig);
37 if (thisResponse.getStatus() == 503){
38 thisResponse.close();
39 throw new ClientException(ClientException.ErrorType.SERVER_THROTTLED);
40 }
41 return thisResponse;
42 }
⑤ 最后，RestTemplate 基于 RestClient 的请求流程可以用下图来做个总结。
4、Apache HttpClient 或 OkHttp 对 RestTemplate 不生效（BUG？）
① Apache HttpClient
默认情况下，ribbon.httpclient.enabled=true，在 HttpClientRibbonConfiguration 中会初始化 apache httpcomponents 相关的组件，前已经分析过了，但是在 RestTemplate 中并未使用相关的组件。
也就是说，默认情况下启用了 apache httpcomponents，但是 RestTemplate 最后是使用 HttpURLConnection 来发起 HTTP 请求的，而不是配置的 CloseableHttpClient。
② OkHttp
首先需要加入 OkHttp 的依赖：
1 <dependency>
2 <groupId>com.squareup.okhttp3</groupId>
3 <artifactId>okhttp</artifactId>
4 </dependency>
然后添加如下配置就可以启用 OkHttp：
1 ribbon:
2 httpclient:
3 enabled: false
4 # 启用 okhttp
5 okhttp:
6 enabled: true
配置 ribbon.okhttp.enabled=true 后，在 OkHttpRibbonConfiguration 中会初始化 OkHttp 相关的组件。
但是调试之后会发现，其实它还是走的默认的流程，就是最终用 HttpURLConnection 发起 HTTP 请求，跟 httpcomponents 是一样的效果。
1 @Configuration(proxyBeanMethods = false)
2 @ConditionalOnProperty("ribbon.okhttp.enabled")
3 @ConditionalOnClass(name = "okhttp3.OkHttpClient")
4 public class OkHttpRibbonConfiguration {
5
6 @RibbonClientName
7 private String name = "client";
8
9 @Bean
10 @ConditionalOnMissingBean(AbstractLoadBalancerAwareClient.class)
11 @ConditionalOnClass(name = "org.springframework.retry.support.RetryTemplate")
12 public RetryableOkHttpLoadBalancingClient retryableOkHttpLoadBalancingClient(
13 IClientConfig config, ServerIntrospector serverIntrospector,
14 ILoadBalancer loadBalancer, RetryHandler retryHandler,
15 LoadBalancedRetryFactory loadBalancedRetryFactory, OkHttpClient delegate,
16 RibbonLoadBalancerContext ribbonLoadBalancerContext) {
17 RetryableOkHttpLoadBalancingClient client = new RetryableOkHttpLoadBalancingClient(
18 delegate, config, serverIntrospector, loadBalancedRetryFactory);
19 client.setLoadBalancer(loadBalancer);
20 client.setRetryHandler(retryHandler);
21 client.setRibbonLoadBalancerContext(ribbonLoadBalancerContext);
22 Monitors.registerObject("Client_" + this.name, client);
23 return client;
24 }
25
26 @Bean
27 @ConditionalOnMissingBean(AbstractLoadBalancerAwareClient.class)
28 @ConditionalOnMissingClass("org.springframework.retry.support.RetryTemplate")
29 public OkHttpLoadBalancingClient okHttpLoadBalancingClient(IClientConfig config,
30 ServerIntrospector serverIntrospector, ILoadBalancer loadBalancer,
31 RetryHandler retryHandler, OkHttpClient delegate) {
32 OkHttpLoadBalancingClient client = new OkHttpLoadBalancingClient(delegate, config,
33 serverIntrospector);
34 client.setLoadBalancer(loadBalancer);
35 client.setRetryHandler(retryHandler);
36 Monitors.registerObject("Client_" + this.name, client);
37 return client;
38 }
39
40 @Configuration(proxyBeanMethods = false)
41 protected static class OkHttpClientConfiguration {
42
43 private OkHttpClient httpClient;
44
45 @Bean
46 @ConditionalOnMissingBean(ConnectionPool.class)
47 public ConnectionPool httpClientConnectionPool(IClientConfig config,
48 OkHttpClientConnectionPoolFactory connectionPoolFactory) {
49 RibbonProperties ribbon = RibbonProperties.from(config);
50 int maxTotalConnections = ribbon.maxTotalConnections();
51 long timeToLive = ribbon.poolKeepAliveTime();
52 TimeUnit ttlUnit = ribbon.getPoolKeepAliveTimeUnits();
53 return connectionPoolFactory.create(maxTotalConnections, timeToLive, ttlUnit);
54 }
55
56 @Bean
57 @ConditionalOnMissingBean(OkHttpClient.class)
58 public OkHttpClient client(OkHttpClientFactory httpClientFactory,
59 ConnectionPool connectionPool, IClientConfig config) {
60 RibbonProperties ribbon = RibbonProperties.from(config);
61 this.httpClient = httpClientFactory.createBuilder(false)
62 .connectTimeout(ribbon.connectTimeout(), TimeUnit.MILLISECONDS)
63 .readTimeout(ribbon.readTimeout(), TimeUnit.MILLISECONDS)
64 .followRedirects(ribbon.isFollowRedirects())
65 .connectionPool(connectionPool).build();
66 return this.httpClient;
67 }
68
69 @PreDestroy
70 public void destroy() {
71 if (httpClient != null) {
72 httpClient.dispatcher().executorService().shutdown();
73 httpClient.connectionPool().evictAll();
74 }
75 }
76
77 }
78
79 }
View Cod
③ 启用 HttpClient 或 OkHttp 不生效的原因
经过前面的分析，可以知道启用 apache httpcomponents 或者 OkHttp，对 RestTemplate 都没有起作用，最终还是用 HttpURLConnection 发起 HTTP 请求。那为什么为出现这种情况呢？我们可以看下 RestTemplate 的 setRequestFactory 方法。
通过 RestTemplate 的 setRequestFactory 方法的注释也可以了解到，默认的 requestFactory 是 SimpleClientHttpRequestFactory，它是基于 JDK 标准 HTTP 库的 HttpURLConnection。
默认的 HttpURLConnection 不支持 PATCH，如果想支持，需设置为 Apache HttpComponents 或 OkHttp 的 request factory。
1 /**
2 * Set the request factory that this accessor uses for obtaining client request handles.
3 * <p>The default is a {@link SimpleClientHttpRequestFactory} based on the JDK's own
4 * HTTP libraries ({@link java.net.HttpURLConnection}).
5 * <p><b>Note that the standard JDK HTTP library does not support the HTTP PATCH method.
6 * Configure the Apache HttpComponents or OkHttp request factory to enable PATCH.</b>
7 * @see #createRequest(URI, HttpMethod)
8 * @see SimpleClientHttpRequestFactory
9 * @see org.springframework.http.client.HttpComponentsAsyncClientHttpRequestFactory
10 * @see org.springframework.http.client.OkHttp3ClientHttpRequestFactory
11 */
12 public void setRequestFactory(ClientHttpRequestFactory requestFactory) {
13 Assert.notNull(requestFactory, "ClientHttpRequestFactory must not be null");
14 this.requestFactory = requestFactory;
15 }
ClientHttpRequestFactory 体系类结构如下：
那 RestClient 又是如何生效的呢？通过上一节的分析可以知道，在 RibbonAutoConfiguration 中有如下的配置，这个 RibbonClientHttpRequestFactoryConfiguration 通过自定义 RestTemplateCustomizer 向 RestTemplate 设置了 requestFactory 为 RibbonClientHttpRequestFactory。
1 @Configuration(proxyBeanMethods = false)
2 @ConditionalOnClass(HttpRequest.class)
3 @ConditionalOnRibbonRestClient
4 protected static class RibbonClientHttpRequestFactoryConfiguration {
5 @Autowired
6 private SpringClientFactory springClientFactory;
7
8 @Bean
9 public RestTemplateCustomizer restTemplateCustomizer(final RibbonClientHttpRequestFactory ribbonClientHttpRequestFactory) {
10 return restTemplate -> restTemplate.setRequestFactory(ribbonClientHttpRequestFactory);
11 }
12
13 @Bean
14 public RibbonClientHttpRequestFactory ribbonClientHttpRequestFactory() {
15 return new RibbonClientHttpRequestFactory(this.springClientFactory);
16 }
17 }
RibbonClientHttpRequestFactory 是对应 RestClient 的，也就是说要启用 OkHttp 或 HttpClient，还需自己创建对应的 ClientHttpRequestFactory，并设置给 RestTemplate。从上面的类结构可以看出，是提供了 HttpComponentsClientHttpRequestFactory 和 OkHttp3ClientHttpRequestFactory 工厂类了的。
这里其实也比较奇怪，既然启用了 apache httpcomponents 或者 OkHttp，却没有创建默认的 ClientHttpRequestFactory 实现类设置给 RestTemplate，感觉这是 spring-cloud-netflix-ribbon 的一个 BUG。
5、定制 RestTemplate 使用 Apache httpcomponents
如果想让 RestTemplate 使用 httpcomponents 的组件，就需要自己创建一个 ClientHttpRequestFactory，并设置给 RestTemplate。下面我们一步步来看看如何修复这个问题。
① 设置 HttpComponentsClientHttpRequestFactory
httpcomponents 中提供的 ClientHttpRequestFactory 实现类是 HttpComponentsClientHttpRequestFactory，但是并不能直接使用这个工厂类，因为它创建的 HttpComponentsClientHttpRequest 不具备重试的能力，它直接使用 CloseableHttpClient 执行请求，虽然有超时的功能，但不能重试。而且，它本质上也没有负载均衡的能力，需要借助 LoadBalancerInterceptor 拦截器来重构 URI。
1 final class HttpComponentsClientHttpRequest extends AbstractBufferingClientHttpRequest {
2 private final HttpClient httpClient;
3 private final HttpUriRequest httpRequest;
4 private final HttpContext httpContext;
5
6 @Override
7 protected ClientHttpResponse executeInternal(HttpHeaders headers, byte[] bufferedOutput) throws IOException {
8 // ...
9 // httpClient => CloseableHttpClient
10 HttpResponse httpResponse = this.httpClient.execute(this.httpRequest, this.httpContext);
11 return new HttpComponentsClientHttpResponse(httpResponse);
12 }
13 }
所以，如果不需要重试的功能，可以直接创建一个 HttpComponentsClientHttpRequest，并设置给 RestTemplate 即可。这样就会使用 LoadBalancerInterceptor 来做负载均衡，重构 URI，然后用 HttpComponentsClientHttpRequest 来执行请求。
1 @Bean
2 @LoadBalanced
3 public RestTemplate restTemplate() {
4 HttpComponentsClientHttpRequestFactory requestFactory = new HttpComponentsClientHttpRequestFactory();
5 RestTemplate restTemplate = new RestTemplate();
6 restTemplate.setRequestFactory(requestFactory);
7 return restTemplate;
8 }
② 定制 apache ClientHttpRequestFactory
如果想让 RestTemplate 即有负载均衡的能力，又能使用 apache HttpComponents 组件，且具备重试的功能，我们就需要自己定制 ClientHttpRequestFactory 了。关于重试后面再单独来讲。
对比 RestClient 可以发现，RibbonClientHttpRequestFactory 创建的 RibbonHttpRequest 其实是使用 RestClient 执行请求，而 RestClient 内部使用 LoadBalancerCommand 来进行重试。
类似的，我们至少要用上已经配置好的 RibbonLoadBalancingHttpClient 来执行请求，所以需要自定义一个类似的 RibbonHttpRequest 。
1）定制 apache ClientHttpRequest
创建 ApacheClientHttpRequest 继承自 RibbonHttpRequest，核心的点在于要注入 RibbonLoadBalancingHttpClient，如果要支持重试，需注入 RetryableRibbonLoadBalancingHttpClient。RetryableRibbonLoadBalancingHttpClient 在引入 spring-retry 后才会创建，这个后面分析重试时再看。
然后在 executeInternal 根据 retryable 判断，如果要重试，就调用 execute 方法，看 RetryableRibbonLoadBalancingHttpClient 的源码可以发现，它本身是支持负载均衡的，会自动选择 Server。
如果不需要重试，就需要调用 executeWithLoadBalancer，它是利用 LoadBalancerCommand 来提交请求，就跟 RestClient 是一样的了。但是不一样的地方是 RibbonLoadBalancingHttpClient 的 executeWithLoadBalancer 是不会进行重试的，这个也放到后面分析。
1 package com.lyyzoo.sunny.register.ribbon.apache;
2
3 import java.io.IOException;
4 import java.net.URI;
5 import java.util.ArrayList;
6
7 import com.netflix.client.config.IClientConfig;
8 import com.netflix.client.http.HttpResponse;
9 import org.springframework.cloud.netflix.ribbon.RibbonHttpRequest;
10 import org.springframework.cloud.netflix.ribbon.RibbonHttpResponse;
11 import org.springframework.cloud.netflix.ribbon.apache.RetryableRibbonLoadBalancingHttpClient;
12 import org.springframework.cloud.netflix.ribbon.apache.RibbonApacheHttpRequest;
13 import org.springframework.cloud.netflix.ribbon.apache.RibbonLoadBalancingHttpClient;
14 import org.springframework.cloud.netflix.ribbon.support.RibbonCommandContext;
15 import org.springframework.http.HttpHeaders;
16 import org.springframework.http.HttpMethod;
17 import org.springframework.http.client.ClientHttpResponse;
18 import org.springframework.util.LinkedMultiValueMap;
19
20 /**
21 * Apache ClientHttpRequest
22 *
23 * @author bojiangzhou
24 */
25 public class ApacheClientHttpRequest extends RibbonHttpRequest {
26
27 private final URI uri;
28
29 private final HttpMethod httpMethod;
30
31 private final String serviceId;
32
33 private final RibbonLoadBalancingHttpClient client;
34
35 private final IClientConfig config;
36 /**
37 * 是否重试
38 */
39 private final boolean retryable;
40
41 public ApacheClientHttpRequest(URI uri,
42 HttpMethod httpMethod,
43 String serviceId,
44 RibbonLoadBalancingHttpClient client,
45 IClientConfig config,
46 boolean retryable) {
47 super(uri, null, null, config);
48 this.uri = uri;
49 this.httpMethod = httpMethod;
50 this.serviceId = serviceId;
51 this.client = client;
52 this.config = config;
53 this.retryable = retryable;
54 if (retryable && !(client instanceof RetryableRibbonLoadBalancingHttpClient)) {
55 throw new IllegalArgumentException("Retryable client must be RetryableRibbonLoadBalancingHttpClient");
56 }
57 }
58
59 @Override
60 protected ClientHttpResponse executeInternal(HttpHeaders headers) throws IOException {
61 try {
62 RibbonCommandContext ribbonCommandContext = new RibbonCommandContext(serviceId, httpMethod.name(),
63 uri.toString(), retryable, headers, new LinkedMultiValueMap<>(), null, new ArrayList<>());
64
65 RibbonApacheHttpRequest request = new RibbonApacheHttpRequest(ribbonCommandContext);
66
67 HttpResponse response;
68 if (retryable) {
69 // RetryableRibbonLoadBalancingHttpClient 本身具备负载均衡的能力
70 response = client.execute(request, config);
71 } else {
72 // RibbonLoadBalancingHttpClient 需调用 executeWithLoadBalancer 才具备负载均衡的能力
73 response = client.executeWithLoadBalancer(request, config);
74 }
75
76 return new RibbonHttpResponse(response);
77 } catch (Exception e) {
78 throw new IOException(e);
79 }
80 }
81 }
2）定制 apache ClientHttpRequestFactory
创建 ApacheClientHttpRequestFactory 继承自 HttpComponentsClientHttpRequestFactory，主要是在 createRequest 方法中创建自定义的 ApacheClientHttpRequest。RibbonLoadBalancingHttpClient 可以从 SpringClientFactory 中获取。
1 package com.lyyzoo.sunny.register.ribbon.apache;
2
3 import java.io.IOException;
4 import java.net.URI;
5
6 import com.netflix.client.config.IClientConfig;
7 import org.springframework.cloud.netflix.ribbon.SpringClientFactory;
8 import org.springframework.cloud.netflix.ribbon.apache.RibbonLoadBalancingHttpClient;
9 import org.springframework.http.HttpMethod;
10 import org.springframework.http.client.ClientHttpRequest;
11 import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
12 import org.springframework.lang.NonNull;
13
14 /**
15 * Apache HttpComponents ClientHttpRequest factory
16 *
17 * @author bojiangzhou
18 */
19 public class ApacheClientHttpRequestFactory extends HttpComponentsClientHttpRequestFactory {
20
21 private final SpringClientFactory clientFactory;
22 private final boolean retryable;
23
24 public ApacheClientHttpRequestFactory(SpringClientFactory clientFactory, boolean retryable) {
25 this.clientFactory = clientFactory;
26 this.retryable = retryable;
27 }
28
29 @Override
30 @NonNull
31 public ClientHttpRequest createRequest(URI originalUri, HttpMethod httpMethod) throws IOException {
32 String serviceId = originalUri.getHost();
33 if (serviceId == null) {
34 throw new IOException(
35 "Invalid hostname in the URI [" + originalUri.toASCIIString() + "]");
36 }
37 IClientConfig clientConfig = this.clientFactory.getClientConfig(serviceId);
38 RibbonLoadBalancingHttpClient httpClient = this.clientFactory.getClient(serviceId, RibbonLoadBalancingHttpClient.class);
39
40 return new ApacheClientHttpRequest(originalUri, httpMethod, serviceId, httpClient, clientConfig, retryable);
41 }
42 }
3）定制 apache ClientHttpRequestFactory 配置类
跟 RestClient 的配置类类似，定制 ApacheClientHttpRequestFactory 的配置类，同样的，默认启用 httpclient。在存在 RetryTemplate 时，就设置 ApacheClientHttpRequestFactory 的 retryable 参数为 true，否则为 false。
然后自定义 RestTemplateCustomizer，将 ApacheClientHttpRequestFactory 设置到 RestTemplate 中，注意这时 LoadBalancerInterceptor 就不会添加到 RestTemplate 中了。
1 package com.lyyzoo.sunny.register.ribbon.apache;
2
3 import org.apache.http.client.HttpClient;
4 import org.springframework.beans.factory.annotation.Autowired;
5 import org.springframework.boot.autoconfigure.AutoConfigureAfter;
6 import org.springframework.boot.autoconfigure.AutoConfigureBefore;
7 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
8 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
9 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingClass;
10 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
11 import org.springframework.cloud.client.loadbalancer.AsyncLoadBalancerAutoConfiguration;
12 import org.springframework.cloud.client.loadbalancer.LoadBalancerAutoConfiguration;
13 import org.springframework.cloud.client.loadbalancer.RestTemplateCustomizer;
14 import org.springframework.cloud.netflix.ribbon.SpringClientFactory;
15 import org.springframework.context.annotation.Bean;
16 import org.springframework.context.annotation.Configuration;
17 import org.springframework.web.client.RestTemplate;
18
19 /**
20 *
21 * @author bojiangzhou
22 */
23 @Configuration
24 @ConditionalOnClass(RestTemplate.class)
25 @AutoConfigureAfter(name = "org.springframework.cloud.netflix.eureka.EurekaClientAutoConfiguration")
26 @AutoConfigureBefore({LoadBalancerAutoConfiguration.class, AsyncLoadBalancerAutoConfiguration.class})
27 @ConditionalOnProperty(name = "ribbon.httpclient.restTemplate.enabled", matchIfMissing = true)
28 public class ApacheClientHttpRequestFactoryConfiguration {
29
30 @Configuration(proxyBeanMethods = false)
31 @ConditionalOnClass(HttpClient.class)
32 @ConditionalOnProperty(name = "ribbon.httpclient.enabled", matchIfMissing = true)
33 static class HttpComponentsClientHttpRequestFactoryConfiguration {
34
35 @Autowired
36 private SpringClientFactory springClientFactory;
37
38 @Bean
39 @ConditionalOnMissingBean
40 public RestTemplateCustomizer restTemplateCustomizer(
41 final ApacheClientHttpRequestFactory apacheClientHttpRequestFactory) {
42 return restTemplate -> restTemplate
43 .setRequestFactory(apacheClientHttpRequestFactory);
44 }
45
46 @Bean
47 @ConditionalOnMissingClass("org.springframework.retry.support.RetryTemplate")
48 public ApacheClientHttpRequestFactory apacheClientHttpRequestFactory() {
49 return new ApacheClientHttpRequestFactory(springClientFactory, false);
50 }
51
52 @Bean
53 @ConditionalOnClass(name = "org.springframework.retry.support.RetryTemplate")
54 public ApacheClientHttpRequestFactory retryableApacheClientHttpRequestFactory() {
55 return new ApacheClientHttpRequestFactory(springClientFactory, true);
56 }
57 }
58 }
4）简单调试下
配置好之后，把 demo-consumer 服务启动起来，简单测试下。
a) 首先请求会进入到 RestTemplate 的 doExecute 中，然后通过 createRequest，调用 ApacheClientHttpRequestFactory 创建 ApacheClientHttpRequest。
b) 接着调用 ApacheClientHttpRequest 的 execute 方法，在 ApacheClientHttpRequest 的 executeInternal 中，就会调用 RibbonLoadBalancingHttpClient 的 executeWithLoadBalancer 方法。
c) 最后，进入 RibbonLoadBalancingHttpClient 的 execute 方法中，它又将请求转给了代理对象 delegate 来执行，delegate 就是在 HttpClientRibbonConfiguration 中配置的 CloseableHttpClient 对象，实际类型是 InternalHttpClient。
经过验证，通过自定义的配置，最终使得 RestTemplate 可以使用 apache httpcomponents 组件来执行 HTTP 请求。重试那块后面再来研究。
③ 还是用一张图来总结下 RestTemplate 基于 apache HttpClient 后的执行流程
6、定制 RestTemplate 使用 OkHttp
① 设置 OkHttp3ClientHttpRequestFactory
类似的，可以给 RestTemplate 直接设置 OkHttp3ClientHttpRequestFactory，但它同样也不具备重试的能力。
1 @Bean
2 @LoadBalanced
3 public RestTemplate restTemplate() {
4 OkHttp3ClientHttpRequestFactory requestFactory = new OkHttp3ClientHttpRequestFactory();
5 RestTemplate restTemplate = new RestTemplate();
6 restTemplate.setRequestFactory(requestFactory);
7 return restTemplate;
8 }
② 定制 OkHttp ClientHttpRequestFactory
与定制 apache httpcomponents 类似，我这里就直接把三个类的代码放出来了。
a) OkHttpClientHttpRequest：
1 package com.lyyzoo.sunny.register.ribbon.okhttp;
2
3 import java.io.IOException;
4 import java.net.URI;
5 import java.util.ArrayList;
6
7 import com.netflix.client.config.IClientConfig;
8 import com.netflix.client.http.HttpResponse;
9 import org.springframework.cloud.netflix.ribbon.RibbonHttpRequest;
10 import org.springframework.cloud.netflix.ribbon.RibbonHttpResponse;
11 import org.springframework.cloud.netflix.ribbon.okhttp.OkHttpLoadBalancingClient;
12 import org.springframework.cloud.netflix.ribbon.okhttp.OkHttpRibbonRequest;
13 import org.springframework.cloud.netflix.ribbon.okhttp.RetryableOkHttpLoadBalancingClient;
14 import org.springframework.cloud.netflix.ribbon.support.RibbonCommandContext;
15 import org.springframework.http.HttpHeaders;
16 import org.springframework.http.HttpMethod;
17 import org.springframework.http.client.ClientHttpResponse;
18 import org.springframework.util.LinkedMultiValueMap;
19
20 /**
21 * OkHttp ClientHttpRequest
22 *
23 * @author bojiangzhou
24 */
25 public class OkHttpClientHttpRequest extends RibbonHttpRequest {
26
27 private final URI uri;
28
29 private final HttpMethod httpMethod;
30
31 private final String serviceId;
32
33 private final OkHttpLoadBalancingClient client;
34
35 private final IClientConfig config;
36 /**
37 * 是否重试
38 */
39 private final boolean retryable;
40
41 public OkHttpClientHttpRequest(URI uri,
42 HttpMethod httpMethod,
43 String serviceId,
44 OkHttpLoadBalancingClient client,
45 IClientConfig config,
46 boolean retryable) {
47 super(uri, null, null, config);
48 this.uri = uri;
49 this.httpMethod = httpMethod;
50 this.serviceId = serviceId;
51 this.client = client;
52 this.config = config;
53 this.retryable = retryable;
54 if (retryable && !(client instanceof RetryableOkHttpLoadBalancingClient)) {
55 throw new IllegalArgumentException("Retryable client must be RetryableOkHttpLoadBalancingClient");
56 }
57 }
58
59 @Override
60 protected ClientHttpResponse executeInternal(HttpHeaders headers) throws IOException {
61 try {
62 RibbonCommandContext ribbonCommandContext = new RibbonCommandContext(serviceId, httpMethod.name(),
63 uri.toString(), retryable, headers, new LinkedMultiValueMap<>(), null, new ArrayList<>());
64
65 OkHttpRibbonRequest request = new OkHttpRibbonRequest(ribbonCommandContext);
66
67 HttpResponse response;
68 if (retryable) {
69 // RetryableRibbonLoadBalancingHttpClient 本身具备负载均衡的能力
70 response = client.execute(request, config);
71 } else {
72 // RibbonLoadBalancingHttpClient 需调用 executeWithLoadBalancer 才具备负载均衡的能力
73 response = client.executeWithLoadBalancer(request, config);
74 }
75
76 return new RibbonHttpResponse(response);
77 } catch (Exception e) {
78 throw new IOException(e);
79 }
80 }
81 }
b) OkHttpClientHttpRequestFactory
1 package com.lyyzoo.sunny.register.ribbon.okhttp;
2
3 import java.io.IOException;
4 import java.net.URI;
5
6 import com.netflix.client.config.IClientConfig;
7 import org.springframework.cloud.netflix.ribbon.SpringClientFactory;
8 import org.springframework.cloud.netflix.ribbon.okhttp.OkHttpLoadBalancingClient;
9 import org.springframework.http.HttpMethod;
10 import org.springframework.http.client.ClientHttpRequest;
11 import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
12 import org.springframework.lang.NonNull;
13
14 /**
15 * OkHttp ClientHttpRequest factory
16 *
17 * @author bojiangzhou
18 */
19 public class OkHttpClientHttpRequestFactory extends HttpComponentsClientHttpRequestFactory {
20
21 private final SpringClientFactory clientFactory;
22 private final boolean retryable;
23
24 public OkHttpClientHttpRequestFactory(SpringClientFactory clientFactory, boolean retryable) {
25 this.clientFactory = clientFactory;
26 this.retryable = retryable;
27 }
28
29 @Override
30 @NonNull
31 public ClientHttpRequest createRequest(URI originalUri, HttpMethod httpMethod) throws IOException {
32 String serviceId = originalUri.getHost();
33 if (serviceId == null) {
34 throw new IOException(
35 "Invalid hostname in the URI [" + originalUri.toASCIIString() + "]");
36 }
37 IClientConfig clientConfig = this.clientFactory.getClientConfig(serviceId);
38 OkHttpLoadBalancingClient httpClient = this.clientFactory.getClient(serviceId, OkHttpLoadBalancingClient.class);
39
40 return new OkHttpClientHttpRequest(originalUri, httpMethod, serviceId, httpClient, clientConfig, retryable);
41 }
42 }
c) OkHttpClientHttpRequestFactoryConfiguration
1 package com.lyyzoo.sunny.register.ribbon.okhttp;
2
3 import org.springframework.beans.factory.annotation.Autowired;
4 import org.springframework.boot.autoconfigure.AutoConfigureAfter;
5 import org.springframework.boot.autoconfigure.AutoConfigureBefore;
6 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
7 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
8 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingClass;
9 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
10 import org.springframework.cloud.client.loadbalancer.AsyncLoadBalancerAutoConfiguration;
11 import org.springframework.cloud.client.loadbalancer.LoadBalancerAutoConfiguration;
12 import org.springframework.cloud.client.loadbalancer.RestTemplateCustomizer;
13 import org.springframework.cloud.netflix.ribbon.SpringClientFactory;
14 import org.springframework.context.annotation.Bean;
15 import org.springframework.context.annotation.Configuration;
16 import org.springframework.web.client.RestTemplate;
17
18 /**
19 *
20 * @author bojiangzhou
21 */
22 @Configuration
23 @ConditionalOnClass(RestTemplate.class)
24 @AutoConfigureAfter(name = "org.springframework.cloud.netflix.eureka.EurekaClientAutoConfiguration")
25 @AutoConfigureBefore({LoadBalancerAutoConfiguration.class, AsyncLoadBalancerAutoConfiguration.class})
26 @ConditionalOnProperty(name = "ribbon.okhttp.restTemplate.enabled", matchIfMissing = true)
27 public class OkHttpClientHttpRequestFactoryConfiguration {
28
29 @Configuration(proxyBeanMethods = false)
30 @ConditionalOnProperty("ribbon.okhttp.enabled")
31 @ConditionalOnClass(name = "okhttp3.OkHttpClient")
32 static class ClientHttpRequestFactoryConfiguration {
33
34 @Autowired
35 private SpringClientFactory springClientFactory;
36
37 @Bean
38 @ConditionalOnMissingBean
39 public RestTemplateCustomizer restTemplateCustomizer(
40 final OkHttpClientHttpRequestFactory okHttpClientHttpRequestFactory) {
41 return restTemplate -> restTemplate
42 .setRequestFactory(okHttpClientHttpRequestFactory);
43 }
44
45 @Bean
46 @ConditionalOnMissingClass("org.springframework.retry.support.RetryTemplate")
47 public OkHttpClientHttpRequestFactory okHttpClientHttpRequestFactory() {
48 return new OkHttpClientHttpRequestFactory(springClientFactory, false);
49 }
50
51 @Bean
52 @ConditionalOnClass(name = "org.springframework.retry.support.RetryTemplate")
53 public OkHttpClientHttpRequestFactory retryableOkHttpClientHttpRequestFactory() {
54 return new OkHttpClientHttpRequestFactory(springClientFactory, true);
55 }
56 }
57 }
七、RestTemplate 超时重试
1、AbstractLoadBalancerAwareClient
① AbstractLoadBalancerAwareClient
通过上一节的分析，可以知道有重试功能的其实有两个组件，一个是 Ribbon 的 LoadBalancerCommand，一个是 spring-retry 的 RetryTemplate。RetryableRibbonLoadBalancingHttpClient 和 RetryableOkHttpLoadBalancingClient 都要依赖 RetryTemplate，所以必须先引入 spring-retry 依赖，它们最终都是使用 RetryTemplate 实现请求重试的能力的。除了 RetryTemplate，其它客户端想要获取重试的功能，就要用 ribbon 中的 AbstractLoadBalancerAwareClient 相关的组件，并调用 executeWithLoadBalancer 方法。
再看下 AbstractLoadBalancerAwareClient 的体系，通过源码可以了解到：
- RetryableFeignLoadBalancer、RetryableRibbonLoadBalancingHttpClient、RetryableOkHttpLoadBalancingClient 都是使用 RetryTemplate 实现重试功能的，也就是 spring-retry 的重试。
- RestClient、FeignLoadBalancer、RibbonLoadBalancingHttpClient、OkHttpLoadBalancingClient 是在 AbstractLoadBalancerAwareClient 中使用 LoadBalancerCommand 实现重试功能的，就是是 Ribbon 的重试。
② executeWithLoadBalancer
具体的 AbstractLoadBalancerAwareClient 客户端想要负载均衡调用以及能进行重试，需调用 AbstractLoadBalancerAwareClient 的 executeWithLoadBalancer 方法。
在这个方法里面，它先构建了 LoadBalancerCommand，然后用 command 提交了一个 ServerOperation，这个 ServerOperation 中对 URI 进行了 重构，转到具体的 LoadBalancerContext 去执行请求。
1 public T executeWithLoadBalancer(final S request, final IClientConfig requestConfig) throws ClientException {
2 // 负载均衡命令
3 LoadBalancerCommand<T> command = buildLoadBalancerCommand(request, requestConfig);
4
5 try {
6 return command.submit(
7 new ServerOperation<T>() {
8 @Override
9 public Observable<T> call(Server server) {
10 // 重构URI
11 URI finalUri = reconstructURIWithServer(server, request.getUri());
12 S requestForServer = (S) request.replaceUri(finalUri);
13 try {
14 // 使用具体的 AbstractLoadBalancerAwareClient 客户端执行请求
15 return Observable.just(AbstractLoadBalancerAwareClient.this.execute(requestForServer, requestConfig));
16 }
17 catch (Exception e) {
18 return Observable.error(e);
19 }
20 }
21 })
22 .toBlocking()
23 .single();
24 }
25 }
再看 buildLoadBalancerCommand 方法，它首先会通过 getRequestSpecificRetryHandler 方法获取请求重试处理器 RequestSpecificRetryHandler，而 getRequestSpecificRetryHandler 是一个抽象方法。这里就要重点注意了。
1 // 抽象方法，获取请求重试处理器
2 public abstract RequestSpecificRetryHandler getRequestSpecificRetryHandler(S request, IClientConfig requestConfig);
3
4 protected LoadBalancerCommand<T> buildLoadBalancerCommand(final S request, final IClientConfig config) {
5 // 获取请求重试处理器
6 RequestSpecificRetryHandler handler = getRequestSpecificRetryHandler(request, config);
7 LoadBalancerCommand.Builder<T> builder = LoadBalancerCommand.<T>builder()
8 .withLoadBalancerContext(this)
9 .withRetryHandler(handler)
10 .withLoadBalancerURI(request.getUri());
11 customizeLoadBalancerCommandBuilder(request, config, builder);
12 return builder.build();
13 }
2、请求重试处理器 RequestSpecificRetryHandler
① 先了解下 RequestSpecificRetryHandler：
- 首先看它的构造方法，注意第一个参数和第二个参数，因为不同的 getRequestSpecificRetryHandler 方法实现，主要差异就在于这两个参数。
- 然后看 isRetriableException，这个方法就是 LoadBalancerCommand 用来判断异常后是否需要重试的方法，可以了解到 okToRetryOnAllErrors=true 时就可以重试，否则 okToRetryOnConnectErrors=true 才可能重试。需要注意的是就算这个方法返回 true 也不一定会重试，这跟重试次数也是有一定关系的。
1 public RequestSpecificRetryHandler(boolean okToRetryOnConnectErrors, boolean okToRetryOnAllErrors, RetryHandler baseRetryHandler, @Nullable IClientConfig requestConfig) {
2 Preconditions.checkNotNull(baseRetryHandler);
3 this.okToRetryOnConnectErrors = okToRetryOnConnectErrors;
4 this.okToRetryOnAllErrors = okToRetryOnAllErrors;
5 this.fallback = baseRetryHandler;
6 if (requestConfig != null) {
7 // 在同一个Server上重试的次数
8 if (requestConfig.containsProperty(CommonClientConfigKey.MaxAutoRetries)) {
9 retrySameServer = requestConfig.get(CommonClientConfigKey.MaxAutoRetries);
10 }
11 // 重试下一个Server的次数
12 if (requestConfig.containsProperty(CommonClientConfigKey.MaxAutoRetriesNextServer)) {
13 retryNextServer = requestConfig.get(CommonClientConfigKey.MaxAutoRetriesNextServer);
14 }
15 }
16 }
17
18 @Override
19 public boolean isRetriableException(Throwable e, boolean sameServer) {
20 // 所有错误都重试
21 if (okToRetryOnAllErrors) {
22 return true;
23 }
24 // ClientException 才可能重试
25 else if (e instanceof ClientException) {
26 ClientException ce = (ClientException) e;
27 if (ce.getErrorType() == ClientException.ErrorType.SERVER_THROTTLED) {
28 return !sameServer;
29 } else {
30 return false;
31 }
32 }
33 else {
34 // 连接错误才重试，就是抛出 SocketException 异常时才重试
35 return okToRetryOnConnectErrors && isConnectionException(e);
36 }
37 }
② 不同 LoadBalancerCommand 的 getRequestSpecificRetryHandler 实现
a）RestClient
默认配置下，RestClient 的 getRequestSpecificRetryHandler 会走到最后一步，okToRetryOnConnectErrors、okToRetryOnAllErrors 都为 true，也就是说 isRetriableException 始终返回 true，也就是说抛出异常都会重试。
1 @Override
2 public RequestSpecificRetryHandler getRequestSpecificRetryHandler(
3 HttpRequest request, IClientConfig requestConfig) {
4 if (!request.isRetriable()) {
5 return new RequestSpecificRetryHandler(false, false, this.getRetryHandler(), requestConfig);
6 }
7 if (this.ncc.get(CommonClientConfigKey.OkToRetryOnAllOperations, false)) {
8 return new RequestSpecificRetryHandler(true, true, this.getRetryHandler(), requestConfig);
9 }
10 if (request.getVerb() != HttpRequest.Verb.GET) {
11 return new RequestSpecificRetryHandler(true, false, this.getRetryHandler(), requestConfig);
12 } else {
13 // okToRetryOnConnectErrors、okToRetryOnAllErrors 都为 true
14 return new RequestSpecificRetryHandler(true, true, this.getRetryHandler(), requestConfig);
15 }
16 }
b）AbstractLoadBalancingClient
AbstractLoadBalancingClient 中的 getRequestSpecificRetryHandler 相当于一个默认实现，默认情况下 okToRetryOnAllOperations 为 false，最后也会到最后一步，即 okToRetryOnConnectErrors、okToRetryOnAllErrors 都为 true，isRetriableException 始终返回 true。
1 @Override
2 public RequestSpecificRetryHandler getRequestSpecificRetryHandler(final S request, final IClientConfig requestConfig) {
3 // okToRetryOnAllOperations：是否所有操作都重试，默认 false
4 if (this.okToRetryOnAllOperations) {
5 return new RequestSpecificRetryHandler(true, true, this.getRetryHandler(), requestConfig);
6 }
7 if (!request.getContext().getMethod().equals("GET")) {
8 return new RequestSpecificRetryHandler(true, false, this.getRetryHandler(), requestConfig);
9 }
10 else {
11 return new RequestSpecificRetryHandler(true, true, this.getRetryHandler(), requestConfig);
12 }
13 }
c）RibbonLoadBalancingHttpClient
RibbonLoadBalancingHttpClient 也重载了 getRequestSpecificRetryHandler，但是它设置了 okToRetryOnConnectErrors、okToRetryOnAllErrors 都为 false，isRetriableException 始终返回 false。
至此我们应该就知道为什么调用 RibbonLoadBalancingHttpClient 的 executeWithLoadBalancer 不具备重试的功能的原因了。所以启用 apache httpclient 时，RibbonLoadBalancingHttpClient 调用是不支持重试的。
1 @Override
2 public RequestSpecificRetryHandler getRequestSpecificRetryHandler(RibbonApacheHttpRequest request, IClientConfig requestConfig) {
3 // okToRetryOnConnectErrors、okToRetryOnAllErrors 都为 false
4 return new RequestSpecificRetryHandler(false, false, RetryHandler.DEFAULT, requestConfig);
5 }
RetryableRibbonLoadBalancingHttpClient 中也重写了 getRequestSpecificRetryHandler，同样也是设置 okToRetryOnConnectErrors、okToRetryOnAllErrors 都为 false。但是在引入 spring-retry 后，它会使用 RetryTemplate 实现重试的功能。
1 @Override
2 public RequestSpecificRetryHandler getRequestSpecificRetryHandler(RibbonApacheHttpRequest request, IClientConfig requestConfig) {
3 // okToRetryOnConnectErrors、okToRetryOnAllErrors 都为 false
4 return new RequestSpecificRetryHandler(false, false, RetryHandler.DEFAULT, null);
5 }
d）OkHttpLoadBalancingClient
OkHttpLoadBalancingClient 并没有重写 getRequestSpecificRetryHandler，所以它是使用父类 AbstractLoadBalancingClient 中的方法，也就是 okToRetryOnConnectErrors、okToRetryOnAllErrors 都为 true。所以，启用 okhttp 时，OkHttpLoadBalancingClient 是支持重试的，这里需要注意。
而 RetryableOkHttpLoadBalancingClient 跟 RetryableRibbonLoadBalancingHttpClient 一样的重写方式，使用 RetryTemplate 实现重试。
1 @Override
2 public RequestSpecificRetryHandler getRequestSpecificRetryHandler(RibbonApacheHttpRequest request, IClientConfig requestConfig) {
3 // okToRetryOnConnectErrors、okToRetryOnAllErrors 都为 false
4 return new RequestSpecificRetryHandler(false, false, RetryHandler.DEFAULT, null);
5 }
3、LoadBalancerCommand
看 LoadBalancerCommand 的 submit 方法，这个方法是重试的核心代码。
- 首先获取了同一个Server重试次数 maxRetrysSame 和 重试下一个Server的次数 maxRetrysNext，其实就是前面配置的 ribbon.MaxAutoRetries 和 ribbon.MaxAutoRetriesNextServer，我设置的是 1。
- 然后创建了一个 Observable，它的第一层会先通过 loadBalancerContext 获取 Server。在重试下一个 Server 时，这里就会获取下一个 Server。
- 在第二层，又创建了一个 Observable，这个 Observable 就是调用 ServerOperation 的，就是重构 URI，调用具体的 AbstractLoadBalancerAwareClient 执行请求。
- 在第二层里，会根据 maxRetrysSame 重试同一个 Server，从 retryPolicy 中可以了解到，当重试次数大于 maxRetrysSame 后，同一个 Server 重试就结束了，否则就用 retryHandler.isRetriableException 判断是否重试，这个前面已经分析过了。
- 在外层，则根据 maxRetrysNext 重试不同的 Server，从 retryPolicy 中可以了解到，当不同Server重试次数大于 maxRetrysNext 后，就重试结束了，整个重试也就结束了，如果还是失败，就会进入 onErrorResumeNext 进行最后的失败处理。
最后来总结一下 LoadBalancerCommand 重试：
- 重试分为同一个 Server 重试和重试下一个Server，当重试次数大于设置的重试值时，就停止重试。否则通过 retryHandler.isRetriableException 判断是否重试。
- 那这里一共请求了多少次呢？可以总结出如下公式：请求次数 = （maxRetrysSame + 1） * （maxRetrysNext + 1），所以按 ribbon.MaxAutoRetries = 1、ribbon.MaxAutoRetriesNextServer = 1 的配置，如果每次请求都超时，就会发起 4 次请求。
1 public Observable<T> submit(final ServerOperation<T> operation) {
2 final ExecutionInfoContext context = new ExecutionInfoContext();
3
4 // 同一个Server重试次数
5 final int maxRetrysSame = retryHandler.getMaxRetriesOnSameServer();
6 // 重试下一个Server的次数
7 final int maxRetrysNext = retryHandler.getMaxRetriesOnNextServer();
8
9 // 创建一个 Observable
10 Observable<T> o =
11 // 使用 loadBalancerContext 获取 Server
12 (server == null ? selectServer() : Observable.just(server))
13 .concatMap(new Func1<Server, Observable<T>>() {
14 @Override
15 public Observable<T> call(Server server) {
16 // 设置Server
17 context.setServer(server);
18 final ServerStats stats = loadBalancerContext.getServerStats(server);
19
20 // 创建 Observable
21 Observable<T> o = Observable
22 .just(server)
23 .concatMap(new Func1<Server, Observable<T>>() {
24 @Override
25 public Observable<T> call(final Server server) {
26 // 增加尝试次数
27 context.incAttemptCount();
28 // ...
29 // 调用 ServerOperation
30 return operation.call(server).doOnEach(new Observer<T>() {
31 // 一些回调方法
32 });
33 }
34 });
35 // 重试同一个Server
36 if (maxRetrysSame > 0)
37 o = o.retry(retryPolicy(maxRetrysSame, true));
38 return o;
39 }
40 });
41
42 if (maxRetrysNext > 0 && server == null)
43 // 重试不同Server
44 o = o.retry(retryPolicy(maxRetrysNext, false));
45
46 return o.onErrorResumeNext(new Func1<Throwable, Observable<T>>() {
47 @Override
48 public Observable<T> call(Throwable e) {
49 // 异常处理
50 return Observable.error(e);
51 }
52 });
53 }
54
55 // retryPolicy 返回一个是否重试的断言
56 private Func2<Integer, Throwable, Boolean> retryPolicy(final int maxRetrys, final boolean same) {
57 return new Func2<Integer, Throwable, Boolean>() {
58 @Override
59 public Boolean call(Integer tryCount, Throwable e) {
60 // 请求拒绝异常就不允许重试
61 if (e instanceof AbortExecutionException) {
62 return false;
63 }
64 // 尝试次数是否大于最大重试次数
65 if (tryCount > maxRetrys) {
66 return false;
67 }
68 // 使用 RequestSpecificRetryHandler 判断是否重试
69 return retryHandler.isRetriableException(e, same);
70 }
71 };
72 }
4、RetryTemplate
① spring-retry
要启用 RetryTemplate 需先引入 spring-retry：
1 <dependency>
2 <groupId>org.springframework.retry</groupId>
3 <artifactId>spring-retry</artifactId>
4 </dependency>
以 RetryableRibbonLoadBalancingHttpClient 为例，先看看它的 execute 方法，它先创建了负载均衡重试策略类 LoadBalancedRetryPolicy，然后将请求调用的逻辑封装到 RetryCallback 中，最后其实就是用 RetryTemplate 执行这个 RetryCallback，也就是说请求重试的逻辑都在 RetryTemplate 中。
1 public RibbonApacheHttpResponse execute(final RibbonApacheHttpRequest request, final IClientConfig configOverride) throws Exception {
2 //...
3
4 // 负载均衡重试策略 RibbonLoadBalancedRetryPolicy
5 final LoadBalancedRetryPolicy retryPolicy = loadBalancedRetryFactory.createRetryPolicy(this.getClientName(), this);
6
7 RetryCallback<RibbonApacheHttpResponse, Exception> retryCallback = context -> {
8 // ...
9 // delegate => CloseableHttpClient
10 final HttpResponse httpResponse = RetryableRibbonLoadBalancingHttpClient.this.delegate.execute(httpUriRequest);
11 // ...
12 // 成功 返回结果
13 return new RibbonApacheHttpResponse(httpResponse, httpUriRequest.getURI());
14 };
15
16 LoadBalancedRecoveryCallback<RibbonApacheHttpResponse, HttpResponse> recoveryCallback = new LoadBalancedRecoveryCallback<RibbonApacheHttpResponse, HttpResponse>()//...
17
18 return this.executeWithRetry(request, retryPolicy, retryCallback, recoveryCallback);
19 }
20
21 private RibbonApacheHttpResponse executeWithRetry(RibbonApacheHttpRequest request,
22 LoadBalancedRetryPolicy retryPolicy,
23 RetryCallback<RibbonApacheHttpResponse, Exception> callback,
24 RecoveryCallback<RibbonApacheHttpResponse> recoveryCallback)
25 throws Exception {
26 RetryTemplate retryTemplate = new RetryTemplate();
27
28 // retryable => 取自 RibbonCommandContext 设置的 retryable 参数
29 boolean retryable = isRequestRetryable(request);
30 // 设置重试策略
31 retryTemplate.setRetryPolicy(retryPolicy == null || !retryable
32 ? new NeverRetryPolicy() : new RetryPolicy(request, retryPolicy, this, this.getClientName()));
33
34 BackOffPolicy backOffPolicy = loadBalancedRetryFactory.createBackOffPolicy(this.getClientName());
35 retryTemplate.setBackOffPolicy(backOffPolicy == null ? new NoBackOffPolicy() : backOffPolicy);
36
37 // 利用 retryTemplate 执行请求 callback
38 return retryTemplate.execute(callback, recoveryCallback);
39 }
需要注意的是，在 executeWithRetry 中，会判断是否要重试，判断的逻辑中 getRetryable 其实就是取的 ApacheClientHttpRequest 中 executeInternal 方法里创建的 RibbonCommandContext 设置的 retryable 参数，这就和前面定制化的逻辑衔接上了。
1 private boolean isRequestRetryable(ContextAwareRequest request) {
2 if (request.getContext() == null || request.getContext().getRetryable() == null) {
3 return true;
4 }
5 return request.getContext().getRetryable();
6 }
② RetryTemplate
进入 RetryTemplate 的 execute 方法，核心的逻辑我精简成如下代码，主要就是一个 while 循环判断是否可以重试，然后调用 retryCallback 执行请求。请求失败后，比如超时，抛出异常，就会 registerThrowable 来注册异常。
1 protected <T, E extends Throwable> T doExecute(RetryCallback<T, E> retryCallback,
2 RecoveryCallback<T> recoveryCallback, RetryState state) throws E, ExhaustedRetryException {
3
4 // retryPolicy => InterceptorRetryPolicy
5 RetryPolicy retryPolicy = this.retryPolicy;
6 BackOffPolicy backOffPolicy = this.backOffPolicy;
7 //....
8 try {
9 // ...
10 // canRetry 判断是否重试
11 while (canRetry(retryPolicy, context) && !context.isExhaustedOnly()) {
12 try {
13 // retryCallback 调用
14 return retryCallback.doWithRetry(context);
15 }
16 catch (Throwable e) {
17 // ...
18 // 注册异常
19 registerThrowable(retryPolicy, state, context, e);
20 // ...
21 }
22 }
23 exhausted = true;
24 return handleRetryExhausted(recoveryCallback, context, state);
25 }
26 //...
27 }
看 canRetry 方法，它实际是调用了 InterceptorRetryPolicy 的 canRetry。第一次调用时，会去获取 Server；否则就用 RibbonLoadBalancedRetryPolicy 判断是否重试下一个 Server，注意它判断的逻辑是 GET 请求或者允许所有操作操作重试，且 Server 重试次数 nextServerCount 小于等于配置的 MaxAutoRetriesNextServer 。也就是说，while 循环判断的 canRetry 是重试下一个 Server 的。
1 protected boolean canRetry(RetryPolicy retryPolicy, RetryContext context) {
2 return retryPolicy.canRetry(context);
3 }
4
5 //////////// InterceptorRetryPolicy
6 public boolean canRetry(RetryContext context) {
7 LoadBalancedRetryContext lbContext = (LoadBalancedRetryContext) context;
8 if (lbContext.getRetryCount() == 0 && lbContext.getServiceInstance() == null) {
9 // 获取 Server
10 lbContext.setServiceInstance(this.serviceInstanceChooser.choose(this.serviceName));
11 return true;
12 }
13 // RibbonLoadBalancedRetryPolicy => 重试下一个Server
14 return this.policy.canRetryNextServer(lbContext);
15 }
16
17 ///////// RibbonLoadBalancedRetryPolicy
18 public boolean canRetryNextServer(LoadBalancedRetryContext context) {
19 // 判断重试下一个Server
20 return nextServerCount <= lbContext.getRetryHandler().getMaxRetriesOnNextServer()
21 && canRetry(context);
22 }
23
24 public boolean canRetry(LoadBalancedRetryContext context) {
25 // GET 请求或者允许所有操作重试时，就允许重试
26 HttpMethod method = context.getRequest().getMethod();
27 return HttpMethod.GET == method || lbContext.isOkToRetryOnAllOperations();
28 }
接着看请求失败后的注册异常 registerThrowable，它最后会向 RibbonLoadBalancedRetryPolicy 注册异常。在 RibbonLoadBalancedRetryPolicy 的 registerThrowable 方法中，如果不重试同一个Server且可以重试下一个Server，就会轮询获取下一个Server。如果可以在同一个Server上重试，sameServerCount 计数器就+1，否则重置 sameServerCount，然后 nextServerCount +1。
1 protected void registerThrowable(RetryPolicy retryPolicy, RetryState state,
2 RetryContext context, Throwable e) {
3 retryPolicy.registerThrowable(context, e);
4 registerContext(context, state);
5 }
6
7 ///////// InterceptorRetryPolicy /////////
8 public void registerThrowable(RetryContext context, Throwable throwable) {
9 LoadBalancedRetryContext lbContext = (LoadBalancedRetryContext) context;
10 lbContext.registerThrowable(throwable);
11 // RibbonLoadBalancedRetryPolicy
12 this.policy.registerThrowable(lbContext, throwable);
13 }
14
15 ///////// RibbonLoadBalancedRetryPolicy /////////
16 public void registerThrowable(LoadBalancedRetryContext context, Throwable throwable) {
17 //...
18 // 如果不在在同一个Server 上重试且可以重试下一个Server，则重新选择一个 Server
19 if (!canRetrySameServer(context) && canRetryNextServer(context)) {
20 context.setServiceInstance(loadBalanceChooser.choose(serviceId));
21 }
22
23 // 同一个Server重试超过设置的值后，就重置 sameServerCount
24 if (sameServerCount >= lbContext.getRetryHandler().getMaxRetriesOnSameServer()
25 && canRetry(context)) {
26 // 重置 nextServerCount
27 sameServerCount = 0;
28 // 下一个Server重试次数+1
29 nextServerCount++;
30 if (!canRetryNextServer(context)) {
31 // 不能重试下一个Server了
32 context.setExhaustedOnly();
33 }
34 }
35 else {
36 // 同一个Server重试次数+1
37 sameServerCount++;
38 }
39 }
40
41 // 判断是否重试同一个Server
42 public boolean canRetrySameServer(LoadBalancedRetryContext context) {
43 return sameServerCount < lbContext.getRetryHandler().getMaxRetriesOnSameServer()
44 && canRetry(context);
45 }
46
47 public boolean canRetry(LoadBalancedRetryContext context) {
48 // GET 请求或者允许所有操作重试时，就允许重试
49 HttpMethod method = context.getRequest().getMethod();
50 return HttpMethod.GET == method || lbContext.isOkToRetryOnAllOperations();
51 }
5、Ribbon 重试总结
① 首先，Ribbon 关于超时和重试的配置参数如下，这些参数也可以针对某个客户端配置：
1 ribbon:
2 # 客户端读取超时时间
3 ReadTimeout: 1000
4 # 客户端连接超时时间
5 ConnectTimeout: 1000
6 # 默认只重试 GET，设置为 true 时将重试所有类型，如 POST、PUT、DELETE
7 OkToRetryOnAllOperations: false
8 # 同一个Server重试次数
9 MaxAutoRetries: 1
10 # 最多重试几个Server
11 MaxAutoRetriesNextServer: 1
② RetryTemplate 是 spring-retry 的重试组件，LoadBalancerCommand 是 Ribbon 的重试组件。它们重试的请求次数是一样的，重试逻辑也是类似，都是先重试当前 Server，再重试下一个Server，总的请求次数 = （MaxAutoRetries + 1） * （MaxAutoRetriesNextServer + 1）。
③ 但是有点差别的是，RetryTemplate 会判断请求方法为 GET 或者 OkToRetryOnAllOperations=true 时才允许重试，而 LoadBalancerCommand 是所有 http 方法都可以重试。这个其实是有问题的，一般只有GET才允许重试，因为GET是查询操作，接口是幂等的，而POST、PUT、DELETE一般是非幂等的。所以一般更建议使用 RetryTemplate，并且配置 OkToRetryOnAllOperations=false。
④ 为了提升服务间通信性能，一般可以启用 apache httpclient 或者 OkHttp，如果要启用重试功能，还需要引入 spring-retry 依赖。重试时，当前Server就不要重试了（MaxAutoRetries=0），直接重试下一个Server。
1 ribbon:
2 # 客户端读取超时时间
3 ReadTimeout: 1000
4 # 客户端连接超时时间
5 ConnectTimeout: 1000
6 # 默认只重试 GET，设置为 true 时将重试所有类型，如 POST、PUT、DELETE
7 OkToRetryOnAllOperations: false
8 # 同一个Server重试次数
9 MaxAutoRetries: 0
10 # 最多重试几个Server
11 MaxAutoRetriesNextServer: 1
12 # 启用 httpclient
13 httpclient:
14 enabled: false
15 # 启用 RestClient
16 restclient:
17 enabled: false
18 # 启用 okhttp
19 okhttp:
20 enabled: true
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