Gateway的限流重试机制详解

前言

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前面给大家介绍了Spring Cloud Gateway的入门教程，这篇给大家探讨下Spring Cloud Gateway的一些其他功能。

Spring Cloud Gateway中的重试

我们知道Spring Cloud Gateway中的大多数操作都是使用过滤器模式实现的，该模式是Spring Framework的一种实现GatewayFilter。在这里，我们可以在发送下游请求之前或之后修改传入请求和传出响应。与我之前关于Spring Cloud Gateway的前两篇文章中描述的示例相同，我们将构建JUnit测试类。它利用TestcontainersMockServer运行模拟暴露的REST端点。在运行测试之前，我们需要准备一个包含名为Retry过滤器的示例路由。在定义此类类型时，GatewayFilter我们可以设置多个参数。通常，您将使用以下三个：

retries 单个传入请求应尝试的重试次数。该属性的默认值为3
statuses–应该重试的HTTP状态代码列表，使用org.springframework.http.HttpStatus枚举名称表示。
backoff–用于在后续重试尝试之间计算Spring Cloud Gateway超时的策略。默认情况下，此属性是禁用的。

让我们从最简单的场景开始-使用参数的默认值。在这种情况下，我们只需要GatewayFilter为路线设置一个名称Retry的filter就可以。

@ClassRule

public static MockServerContainer mockServer = new MockServerContainer();

@BeforeClass

public static void init() {

  // 设置系统参数

   System.setProperty("spring.cloud.gateway.routes[0].id", "account-service");

   System.setProperty("spring.cloud.gateway.routes[0].uri", "http://192.168.99.100:" + mockServer.getServerPort());

   System.setProperty("spring.cloud.gateway.routes[0].predicates[0]", "Path=/account/**");

   System.setProperty("spring.cloud.gateway.routes[0].filters[0]", "RewritePath=/account/(?<path>.*), /$\\{path}");

   System.setProperty("spring.cloud.gateway.routes[0].filters[1].name", "Retry");

  // 使用mockServer容器

   MockServerClient client = new MockServerClient(mockServer.getContainerIpAddress(), mockServer.getServerPort());

   // 请求url:/1 生效次数：Times.exactly(3)

   client.when(HttpRequest.request()

      .withPath("/1"), Times.exactly(3))

      .respond(response()

         .withStatusCode(500)

         .withBody("{\"errorCode\":\"5.01\"}")

         .withHeader("Content-Type", "application/json"));

  // 请求第4次后走这边配置的/1

   client.when(HttpRequest.request()

      .withPath("/1"))

      .respond(response()

         .withBody("{\"id\":1,\"number\":\"1234567891\"}")

         .withHeader("Content-Type", "application/json"));

}

我们的测试方法非常简单。它只是使用Spring FrameworkTestRestTemplate来执行对测试端点的单个调用。

@Autowired

TestRestTemplate template;

@Test

public void testAccountService() {

   LOGGER.info("Sending /1...");

   ResponseEntity r = template.exchange("/account/{id}", HttpMethod.GET, null, Account.class, 1);

   LOGGER.info("Received: status->{}, payload->{}", r.getStatusCodeValue(), r.getBody());

   Assert.assertEquals(200, r.getStatusCodeValue());

}

在运行测试之前，我们要设置一下Spring Cloud Gateway日志的日志记录级别，方便我们可以查看有关重试过程的信息。

logging.level.org.springframework.cloud.gateway.filter.factory: TRACE

由于我们未设置任何退避策略，因此立即尝试了后续尝试。如下图所示，默认重试次数为3，并且过滤器尝试重试所有返回500的请求）。

15:00:49.049 --- [           main] : Started GatewayRetryTest in 3.18 seconds (JVM running for 10.757)

15:00:49.252 --- [           main] : Sending /1...

15:00:49.382 --- [ctor-http-nio-2] : Entering retry-filter

15:00:49.520 --- [ctor-http-nio-3] : setting new iteration in attr 0

15:00:49.522 --- [ctor-http-nio-3] : exceedsMaxIterations false, iteration 0, configured retries 3

15:00:49.523 --- [ctor-http-nio-3] : retryableStatusCode: true, statusCode 500 INTERNAL_SERVER_ERROR, configured statuses [500 INTERNAL_SERVER_ERROR], configured series [SERVER_ERROR]

15:00:49.523 --- [ctor-http-nio-3] : retryableMethod: true, httpMethod GET, configured methods [GET]

15:00:49.571 --- [ctor-http-nio-3] : setting new iteration in attr 1

15:00:49.571 --- [ctor-http-nio-3] : exceedsMaxIterations false, iteration 1, configured retries 3

15:00:49.571 --- [ctor-http-nio-3] : retryableStatusCode: true, statusCode 500 INTERNAL_SERVER_ERROR, configured statuses [500 INTERNAL_SERVER_ERROR], configured series [SERVER_ERROR]

15:00:49.571 --- [ctor-http-nio-3] : retryableMethod: true, httpMethod GET, configured methods [GET]

15:00:49.584 --- [ctor-http-nio-3] : setting new iteration in attr 2

15:00:49.584 --- [ctor-http-nio-3] : exceedsMaxIterations false, iteration 2, configured retries 3

15:00:49.584 --- [ctor-http-nio-3] : retryableStatusCode: true, statusCode 500 INTERNAL_SERVER_ERROR, configured statuses [500 INTERNAL_SERVER_ERROR], configured series [SERVER_ERROR]

15:00:49.584 --- [ctor-http-nio-3] : retryableMethod: true, httpMethod GET, configured methods [GET]

15:00:49.633 --- [ctor-http-nio-3] : setting new iteration in attr 3

15:00:49.634 --- [ctor-http-nio-3] : exceedsMaxIterations true, iteration 3, configured retries 3

15:00:49.646 --- [           main] : Received: status->404, payload->null

java.lang.AssertionError:

Expected :200

Actual   :404

<Click to see difference>

现在，让我们设置一些更高级的配置。我们可以更改重试次数，并设置要重试的确切HTTP状态代码，而不是一系列代码。在我们的例子中，重试的状态代码是HTTP 500，因为它是由我们的模拟端点返回的。

默认触发重试的计算公式为：

backoff.firstBackoff <= prevBackoff * factor < =backoff.maxBackoff

backoff.firstBackoff 开始重试的时间
backoff.maxBackoff 最大重试的时间
backoff.factor 重试因子
basedOnPreviousValue
- 当设置为false时候计算重试值变成： firstBackoff * (factor ^ n)
- 当设置为true时候计算重试值变成： prevBackoff * factor

@ClassRule

public static MockServerContainer mockServer = new MockServerContainer();

@BeforeClass

public static void init() {

   System.setProperty("spring.cloud.gateway.routes[0].id", "account-service");

   System.setProperty("spring.cloud.gateway.routes[0].uri", "http://192.168.99.100:" + mockServer.getServerPort());

   System.setProperty("spring.cloud.gateway.routes[0].predicates[0]", "Path=/account/**");

   System.setProperty("spring.cloud.gateway.routes[0].filters[0]", "RewritePath=/account/(?<path>.*), /$\\{path}");

   System.setProperty("spring.cloud.gateway.routes[0].filters[1].name", "Retry");

   System.setProperty("spring.cloud.gateway.routes[0].filters[1].args.retries", "10");

   System.setProperty("spring.cloud.gateway.routes[0].filters[1].args.statuses", "INTERNAL_SERVER_ERROR");

   System.setProperty("spring.cloud.gateway.routes[0].filters[1].args.backoff.firstBackoff", "50ms");

   System.setProperty("spring.cloud.gateway.routes[0].filters[1].args.backoff.maxBackoff", "500ms");

   System.setProperty("spring.cloud.gateway.routes[0].filters[1].args.backoff.factor", "2");

   System.setProperty("spring.cloud.gateway.routes[0].filters[1].args.backoff.basedOnPreviousValue", "true");

   MockServerClient client = new MockServerClient(mockServer.getContainerIpAddress(), mockServer.getServerPort());

   client.when(HttpRequest.request()

      .withPath("/1"), Times.exactly(3))

      .respond(response()

         .withStatusCode(500)

         .withBody("{\"errorCode\":\"5.01\"}")

         .withHeader("Content-Type", "application/json"));

   client.when(HttpRequest.request()

      .withPath("/1"))

      .respond(response()

         .withBody("{\"id\":1,\"number\":\"1234567891\"}")

         .withHeader("Content-Type", "application/json"));

   // OTHER RULES

}

如果使用新配置再运行一次相同的测试，则日志看起来会有些不同。我在下面的图片中强调了最重要的区别。如您所见，仅HTTP 500状态的当前重试次数为10。设置重试策略后，第一次重试尝试在50毫秒后执行，第二次重试在100毫秒后进行，第三次重试在200毫秒后进行，依此类推。（日志记录时间会有一点延迟，大家可以改变factor进行验证）

15:24:01.133 --- [           main] : Sending /1...

15:24:01.288 --- [ctor-http-nio-2] : Entering retry-filter

## 第一次请求时间 419

15:24:01.419 --- [ctor-http-nio-3] : setting new iteration in attr 0

15:24:01.421 --- [ctor-http-nio-3] : exceedsMaxIterations false, iteration 0, configured retries 3

15:24:01.422 --- [ctor-http-nio-3] : retryableStatusCode: true, statusCode 500 INTERNAL_SERVER_ERROR, configured statuses [500 INTERNAL_SERVER_ERROR], configured series [SERVER_ERROR]

15:24:01.423 --- [ctor-http-nio-3] : retryableMethod: true, httpMethod GET, configured methods [GET]

## 第一次重试时间 494  重试时间大概在 494 -419 = 75

15:24:01.494 --- [ctor-http-nio-3] : setting new iteration in attr 1

15:24:01.494 --- [ctor-http-nio-3] : exceedsMaxIterations false, iteration 1, configured retries 3

15:24:01.494 --- [ctor-http-nio-3] : retryableStatusCode: true, statusCode 500 INTERNAL_SERVER_ERROR, configured statuses [500 INTERNAL_SERVER_ERROR], configured series [SERVER_ERROR]

15:24:01.494 --- [ctor-http-nio-3] : retryableMethod: true, httpMethod GET, configured methods [GET]

## 第二次重试时间 623  重试时间大概在 623 -494 = 129

15:24:01.623 --- [ctor-http-nio-3] : setting new iteration in attr 2

15:24:01.623 --- [ctor-http-nio-3] : exceedsMaxIterations false, iteration 2, configured retries 3

15:24:01.623 --- [ctor-http-nio-3] : retryableStatusCode: true, statusCode 500 INTERNAL_SERVER_ERROR, configured statuses [500 INTERNAL_SERVER_ERROR], configured series [SERVER_ERROR]

15:24:01.623 --- [ctor-http-nio-3] : retryableMethod: true, httpMethod GET, configured methods [GET]

## 第二次重试时间 623  重试时间大概在 852 -623 = 230

15:24:01.852 --- [ctor-http-nio-3] : setting new iteration in attr 3

15:24:01.852 --- [ctor-http-nio-3] : exceedsMaxIterations true, iteration 3, configured retries 3

15:24:01.878 --- [           main] : Received: status->200, payload->Account(id=1, number=1234567891)

Spring Cloud Gateway中的超时

超时是请求路由的另一个重要方面。使用Spring Cloud Gateway，我们可以轻松设置全局读取和连接超时。另外，我们也可以为每个路线分别定义它们。让我们在测试路由定义中添加以下属性全局超时设置为100ms。现在，我们的测试路由包含一个测试Retry过滤器，其新添加的全局读取超时为100ms。

System.setProperty("spring.cloud.gateway.httpclient.response-timeout", "100ms");

另外，我们可以设置每条路由的超时时间。如果我们在这里更喜欢这样的解决方案，则应该在示例测试中添加一行。

System.setProperty("spring.cloud.gateway.routes[1].metadata.response-timeout", "100");

然后，我们定义一个请求路径为/2具有200ms延迟的另一个测试端点。我们当前的测试方法与前一种方法非常相似，不同之处在于，我们期望使用HTTP 504作为结果。

@Test

public void testAccountServiceFail() {

   LOGGER.info("Sending /2...");

   ResponseEntity<Account> r = template.exchange("/account/{id}", HttpMethod.GET, null, Account.class, 2);

   LOGGER.info("Received: status->{}, payload->{}", r.getStatusCodeValue(), r.getBody());

   Assert.assertEquals(504, r.getStatusCodeValue());

}

让我们进行测试。结果在下面的图片中可见。日志中请求在几次失败重试后，由于设置最大的重试时间为500ms。Retry过滤器会打印出IOException和TimeoutException。

15:41:15.814 --- [           main] : Sending /2...

15:41:15.940 --- [ctor-http-nio-2] : Entering retry-filter

15:41:16.077 --- [     parallel-1] : setting new iteration in attr 0

15:41:16.078 --- [     parallel-1] : exceedsMaxIterations false, iteration 0, configured retries 3

15:41:16.079 --- [     parallel-1] : exception or its cause is retryable org.springframework.web.server.ResponseStatusException{cause=org.springframework.cloud.gateway.support.TimeoutException}, configured exceptions [class java.io.IOException, class org.springframework.cloud.gateway.support.TimeoutException]

15:41:16.239 --- [     parallel-3] : setting new iteration in attr 1

15:41:16.240 --- [     parallel-3] : exceedsMaxIterations false, iteration 1, configured retries 3

15:41:16.240 --- [     parallel-3] : exception or its cause is retryable org.springframework.web.server.ResponseStatusException{cause=org.springframework.cloud.gateway.support.TimeoutException}, configured exceptions [class java.io.IOException, class org.springframework.cloud.gateway.support.TimeoutException]

15:41:16.500 --- [     parallel-5] : setting new iteration in attr 2

15:41:16.500 --- [     parallel-5] : exceedsMaxIterations false, iteration 2, configured retries 3

15:41:16.500 --- [     parallel-5] : exception or its cause is retryable org.springframework.web.server.ResponseStatusException{cause=org.springframework.cloud.gateway.support.TimeoutException}, configured exceptions [class java.io.IOException, class org.springframework.cloud.gateway.support.TimeoutException]

15:41:17.058 --- [     parallel-7] : setting new iteration in attr 3

15:41:17.059 --- [     parallel-7] : exceedsMaxIterations true, iteration 3, configured retries 3

15:41:17.128 --- [           main] : Received: status->504, payload->Account(id=null, number=null)

END

下篇给大家介绍Spring Cloud Gateway的限流

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