Kafka（二）CentOS7.5搭建Kafka2.11-1.1.0集群与简单测试

一、下载

下载地址：

http://kafka.apache.org/downloads.html 我这里下载的是Scala 2.11对应的 kafka_2.11-1.1.0.tgz

二、kafka安装

集群规划

IP	节点名称	Kafka	Zookeeper	Jdk	Scala
192.168.100.21	node21	Kafka	Zookeeper	Jdk	Scala
192.168.100.22	node22	Kafka	Zookeeper	Jdk	Scala
192.168.100.23	node23	Kafka	Zookeeper	Jdk	Scala

Zookeeper集群安装参考： CentOS7.5搭建Zookeeper3.4.12集群与命令行操作

2.1 上传解压缩

[admin@node21 software]$ tar zxvf kafka_2.11-1.1.0.tgz -C /opt/module/

2.2 创建日志目录

[admin@node21 software]$ cd /opt/module/kafka_2.11-1.1.0

[admin@node21 kafka_2.11-1.1.0]$ mkdir logs

2.3 修改配置文件

进入kafka的安装配置目录

[admin@node21 kafka_2.11-1.1.0]$ cd config/

[admin@node21 config]$ vi server.properties

主要关注：server.properties 这个文件即可，发现在配置目录下也有Zookeeper文件，我们可以根据Kafka内置的zk集群来启动，但是建议使用独立的zk集群。

server.properties（broker.id和listeners每个节点都不相同）

#是否允许删除topic，默认false不能手动删除

delete.topic.enable=true

#当前机器在集群中的唯一标识，和zookeeper的myid性质一样

broker.id=

#当前kafka服务侦听的地址和端口，端口默认是9092

listeners = PLAINTEXT://192.168.100.21:9092

#这个是borker进行网络处理的线程数

num.network.threads=3

#这个是borker进行I/O处理的线程数

num.io.threads=8

#发送缓冲区buffer大小，数据不是一下子就发送的，先会存储到缓冲区到达一定的大小后在发送，能提高性能

socket.send.buffer.bytes=102400

#kafka接收缓冲区大小，当数据到达一定大小后在序列化到磁盘

socket.receive.buffer.bytes=102400

#这个参数是向kafka请求消息或者向kafka发送消息的请请求的最大数，这个值不能超过java的堆栈大小

socket.request.max.bytes=104857600

#消息日志存放的路径

log.dirs=/opt/module/kafka_2.11-1.1.0/logs

#默认的分区数，一个topic默认1个分区数

num.partitions=1

#每个数据目录用来日志恢复的线程数目

num.recovery.threads.per.data.dir=1

#默认消息的最大持久化时间，168小时，7天

log.retention.hours=168

#这个参数是：因为kafka的消息是以追加的形式落地到文件，当超过这个值的时候，kafka会新起一个文件

log.segment.bytes=1073741824

#每隔300000毫秒去检查上面配置的log失效时间

log.retention.check.interval.ms=300000

#是否启用log压缩，一般不用启用，启用的话可以提高性能

log.cleaner.enable=false

#设置zookeeper的连接端口

zookeeper.connect=node21:2181,node22:2181,node23:2181

#设置zookeeper的连接超时时间

zookeeper.connection.timeout.ms=6000

2.4分发安装包到其他节点

[admin@node21 module]$ scp -r kafka_2.11-1.1.0 admin@node22:/opt/module/

[admin@node21 module]$ scp -r kafka_2.11-1.1.0 admin@node23:/opt/module/

修改node22，node23节点kafka配置文件conf/server.properties里面的broker.id和listeners的值。

2.5 添加环境变量

[admin@node21 module]$ vi /etc/profile

#KAFKA_HOME

export KAFKA_HOME=/opt/module/kafka_2.11-1.1.0
export PATH=$PATH:$KAFKA_HOME/bin

保存使其立即生效

[admin@node21 module]$  source /etc/profile

三、kafka集群启动

3.1 首先启动zookeeper集群

所有zookeeper节点都需要执行

[admin@node21 ~]$ zkServer.sh start

3.2 后台启动Kafka集群服务

所有Kafka节点都需要执行

[admin@node21 kafka_2.11-1.1.0]$ bin/kafka-server-start.sh config/server.properties &

四、kafka命令行操作

kafka-broker-list：node21:9092,node22:9092,node23:9092

zookeeper.connect-list： node21:2181,node22:2181,node23:2181

4.1 创建新topic

[admin@node22 kafka_2.11-1.1.0]$ bin/kafka-topics.sh

Create, delete, describe, or change a topic.

Option                                   Description

------                                   -----------

--alter                                  Alter the number of partitions,

                                           replica assignment, and/or

                                           configuration for the topic.

--config <String: name=value>            A topic configuration override for the

                                           topic being created or altered.The

                                           following is a list of valid

                                           configurations:

                                             cleanup.policy

                                             compression.type

                                             delete.retention.ms

                                             file.delete.delay.ms

                                             flush.messages

                                             flush.ms

                                             follower.replication.throttled.

                                           replicas

                                             index.interval.bytes

                                             leader.replication.throttled.replicas

                                             max.message.bytes

                                             message.format.version

                                             message.timestamp.difference.max.ms

                                             message.timestamp.type

                                             min.cleanable.dirty.ratio

                                             min.compaction.lag.ms

                                             min.insync.replicas

                                             preallocate

                                             retention.bytes

                                             retention.ms

                                             segment.bytes

                                             segment.index.bytes

                                             segment.jitter.ms

                                             segment.ms

                                             unclean.leader.election.enable

                                         See the Kafka documentation for full

                                           details on the topic configs.

--create                                 Create a new topic.

--delete                                 Delete a topic

--delete-config <String: name>           A topic configuration override to be

                                           removed for an existing topic (see

                                           the list of configurations under the

                                           --config option).

--describe                               List details for the given topics.

--disable-rack-aware                     Disable rack aware replica assignment

--force                                  Suppress console prompts

--help                                   Print usage information.

--if-exists                              if set when altering or deleting

                                           topics, the action will only execute

                                           if the topic exists

--if-not-exists                          if set when creating topics, the

                                           action will only execute if the

                                           topic does not already exist

--list                                   List all available topics.

--partitions <Integer: # of partitions>  The number of partitions for the topic

                                           being created or altered (WARNING:

                                           If partitions are increased for a

                                           topic that has a key, the partition

                                           logic or ordering of the messages

                                           will be affected

--replica-assignment <String:            A list of manual partition-to-broker

  broker_id_for_part1_replica1 :           assignments for the topic being

  broker_id_for_part1_replica2 ,           created or altered.

  broker_id_for_part2_replica1 :

  broker_id_for_part2_replica2 , ...>

--replication-factor <Integer:           The replication factor for each

  replication factor>                      partition in the topic being created.

--topic <String: topic>                  The topic to be create, alter or

                                           describe. Can also accept a regular

                                           expression except for --create option

--topics-with-overrides                  if set when describing topics, only

                                           show topics that have overridden

                                           configs

--unavailable-partitions                 if set when describing topics, only

                                           show partitions whose leader is not

                                           available

--under-replicated-partitions            if set when describing topics, only

                                           show under replicated partitions

--zookeeper <String: hosts>              REQUIRED: The connection string for

                                           the zookeeper connection in the form

                                           host:port. Multiple hosts can be

                                           given to allow fail-over.

在node21节点上创建一个新的Topic

[admin@node21 kafka_2.11-1.1.0]$ bin/kafka-topics.sh --create --zookeeper node21:2181,node22:2181,node23:2181 --replication-factor 3 --partitions 3 --topic TestTopic

选项说明：

--topic 定义topic名

--replication-factor 定义副本数

--partitions 定义分区数

4.2 查看topic副本信息

[admin@node21 kafka_2.11-1.1.0]$ bin/kafka-topics.sh --describe --zookeeper node21:2181,node22:2181,node23:2181 --topic TestTopic

4.3 查看已经创建的topic信息

[admin@node21 kafka_2.11-1.1.0]$ kafka-topics.sh --list --zookeeper node21:2181,node22:2181,node23:2181

4.4 测试生产者发送消息

[admin@node22 kafka_2.11-1.1.0]$ bin/kafka-console-producer.sh

Read data from standard input and publish it to Kafka.

Option                                   Description

------                                   -----------

--batch-size <Integer: size>             Number of messages to send in a single

                                           batch if they are not being sent

                                           synchronously. (default: 200)

--broker-list <String: broker-list>      REQUIRED: The broker list string in

                                           the form HOST1:PORT1,HOST2:PORT2.

--compression-codec [String:             The compression codec: either 'none',

  compression-codec]                       'gzip', 'snappy', or 'lz4'.If

                                           specified without value, then it

                                           defaults to 'gzip'

--key-serializer <String:                The class name of the message encoder

  encoder_class>                           implementation to use for

                                           serializing keys. (default: kafka.

                                           serializer.DefaultEncoder)

--line-reader <String: reader_class>     The class name of the class to use for

                                           reading lines from standard in. By

                                           default each line is read as a

                                           separate message. (default: kafka.

                                           tools.

                                           ConsoleProducer$LineMessageReader)

--max-block-ms <Long: max block on       The max time that the producer will

  send>                                    block for during a send request

                                           (default: 60000)

--max-memory-bytes <Long: total memory   The total memory used by the producer

  in bytes>                                to buffer records waiting to be sent

                                           to the server. (default: 33554432)

--max-partition-memory-bytes <Long:      The buffer size allocated for a

  memory in bytes per partition>           partition. When records are received

                                           which are smaller than this size the

                                           producer will attempt to

                                           optimistically group them together

                                           until this size is reached.

                                           (default: 16384)

--message-send-max-retries <Integer>     Brokers can fail receiving the message

                                           for multiple reasons, and being

                                           unavailable transiently is just one

                                           of them. This property specifies the

                                           number of retires before the

                                           producer give up and drop this

                                           message. (default: 3)

--metadata-expiry-ms <Long: metadata     The period of time in milliseconds

  expiration interval>                     after which we force a refresh of

                                           metadata even if we haven't seen any

                                           leadership changes. (default: 300000)

--old-producer                           Use the old producer implementation.

--producer-property <String:             A mechanism to pass user-defined

  producer_prop>                           properties in the form key=value to

                                           the producer.

--producer.config <String: config file>  Producer config properties file. Note

                                           that [producer-property] takes

                                           precedence over this config.

--property <String: prop>                A mechanism to pass user-defined

                                           properties in the form key=value to

                                           the message reader. This allows

                                           custom configuration for a user-

                                           defined message reader.

--queue-enqueuetimeout-ms <Integer:      Timeout for event enqueue (default:

  queue enqueuetimeout ms>                 2147483647)

--queue-size <Integer: queue_size>       If set and the producer is running in

                                           asynchronous mode, this gives the

                                           maximum amount of  messages will

                                           queue awaiting sufficient batch

                                           size. (default: 10000)

--request-required-acks <String:         The required acks of the producer

  request required acks>                   requests (default: 1)

--request-timeout-ms <Integer: request   The ack timeout of the producer

  timeout ms>                              requests. Value must be non-negative

                                           and non-zero (default: 1500)

--retry-backoff-ms <Integer>             Before each retry, the producer

                                           refreshes the metadata of relevant

                                           topics. Since leader election takes

                                           a bit of time, this property

                                           specifies the amount of time that

                                           the producer waits before refreshing

                                           the metadata. (default: 100)

--socket-buffer-size <Integer: size>     The size of the tcp RECV size.

                                           (default: 102400)

--sync                                   If set message send requests to the

                                           brokers are synchronously, one at a

                                           time as they arrive.

--timeout <Integer: timeout_ms>          If set and the producer is running in

                                           asynchronous mode, this gives the

                                           maximum amount of time a message

                                           will queue awaiting sufficient batch

                                           size. The value is given in ms.

                                           (default: 1000)

--topic <String: topic>                  REQUIRED: The topic id to produce

                                           messages to.

--value-serializer <String:              The class name of the message encoder

  encoder_class>                           implementation to use for

                                           serializing values. (default: kafka.

                                           serializer.DefaultEncoder)

在node21上生产消息

[admin@node21 kafka_2.11-1.1.0]$ bin/kafka-console-producer.sh --broker-list node21:9092,node22:9092,node23:9092 --topic TestTopic

4.5 测试消费者消费消息

[admin@node22 kafka_2.11-1.1.0]$ bin/kafka-console-consumer.sh

The console consumer is a tool that reads data from Kafka and outputs it to standard output.

Option                                   Description

------                                   -----------

--blacklist <String: blacklist>          Blacklist of topics to exclude from

                                           consumption.

--bootstrap-server <String: server to    REQUIRED (unless old consumer is

  connect to>                              used): The server to connect to.

--consumer-property <String:             A mechanism to pass user-defined

  consumer_prop>                           properties in the form key=value to

                                           the consumer.

--consumer.config <String: config file>  Consumer config properties file. Note

                                           that [consumer-property] takes

                                           precedence over this config.

--csv-reporter-enabled                   If set, the CSV metrics reporter will

                                           be enabled

--delete-consumer-offsets                If specified, the consumer path in

                                           zookeeper is deleted when starting up

--enable-systest-events                  Log lifecycle events of the consumer

                                           in addition to logging consumed

                                           messages. (This is specific for

                                           system tests.)

--formatter <String: class>              The name of a class to use for

                                           formatting kafka messages for

                                           display. (default: kafka.tools.

                                           DefaultMessageFormatter)

--from-beginning                         If the consumer does not already have

                                           an established offset to consume

                                           from, start with the earliest

                                           message present in the log rather

                                           than the latest message.

--group <String: consumer group id>      The consumer group id of the consumer.

--isolation-level <String>               Set to read_committed in order to

                                           filter out transactional messages

                                           which are not committed. Set to

                                           read_uncommittedto read all

                                           messages. (default: read_uncommitted)

--key-deserializer <String:

  deserializer for key>

--max-messages <Integer: num_messages>   The maximum number of messages to

                                           consume before exiting. If not set,

                                           consumption is continual.

--metrics-dir <String: metrics           If csv-reporter-enable is set, and

  directory>                               this parameter isset, the csv

                                           metrics will be output here

--new-consumer                           Use the new consumer implementation.

                                           This is the default, so this option

                                           is deprecated and will be removed in

                                           a future release.

--offset <String: consume offset>        The offset id to consume from (a non-

                                           negative number), or 'earliest'

                                           which means from beginning, or

                                           'latest' which means from end

                                           (default: latest)

--partition <Integer: partition>         The partition to consume from.

                                           Consumption starts from the end of

                                           the partition unless '--offset' is

                                           specified.

--property <String: prop>                The properties to initialize the

                                           message formatter.

--skip-message-on-error                  If there is an error when processing a

                                           message, skip it instead of halt.

--timeout-ms <Integer: timeout_ms>       If specified, exit if no message is

                                           available for consumption for the

                                           specified interval.

--topic <String: topic>                  The topic id to consume on.

--value-deserializer <String:

  deserializer for values>

--whitelist <String: whitelist>          Whitelist of topics to include for

                                           consumption.

--zookeeper <String: urls>               REQUIRED (only when using old

                                           consumer): The connection string for

                                           the zookeeper connection in the form

                                           host:port. Multiple URLS can be

                                           given to allow fail-over.

在node22上消费消息(旧命令操作）

[admin@node22 kafka_2.11-1.1.0]$ kafka-console-consumer.sh --zookeeper node21:2181,node22:2181,node23:2181  --from-beginning --topic TestTopic

--from-beginning：会把TestTopic主题中以往所有的数据都读取出来。根据业务场景选择是否增加该配置。

新消费者命令

[admin@node22 kafka_2.11-1.1.0]$ kafka-console-consumer.sh --bootstrap-server node21:9092,node22:9092,node23:9092  --from-beginning --topic TestTopic

4.6删除topic

[admin@node22 kafka_2.11-1.1.0]$ bin/kafka-topics.sh --zookeeper node21:2181,node22:2181,node23:2181  --delete --topic TestTopic

需要server.properties中设置delete.topic.enable=true否则只是标记删除或者直接重启。

4.7 停止Kafka服务

[admin@node21 kafka_2.11-1.1.0]$ bin/kafka-server-stop.sh stop

4.8 编写kafka启动脚本

[admin@node21 kafka_2.11-1.1.0]$ cd bin

[admin@node21 bin]$ vi start-kafka.sh

#!/bin/bash

nohup /opt/module/kafka_2.11-1.1.0/bin/kafka-server-start.sh  /opt/module/kafka_2.11-1.1.0/config/server.properties >/opt/module/kafka_2.11-1.1.0/logs/kafka.log 2>&1 &

赋权限给脚本：chmod +x start-kafka.sh

五、Kafka配置信息详解

5.1 Broker配置信息

属性	默认值	描述
broker.id		必填参数，broker的唯一标识
log.dirs	/tmp/kafka-logs	Kafka数据存放的目录。可以指定多个目录，中间用逗号分隔，当新partition被创建的时会被存放到当前存放partition最少的目录。
port	9092	BrokerServer接受客户端连接的端口号
zookeeper.connect	null	Zookeeper的连接串，格式为：hostname1:port1,hostname2:port2,hostname3:port3。可以填一个或多个，为了提高可靠性，建议都填上。注意，此配置允许我们指定一个zookeeper路径来存放此kafka集群的所有数据，为了与其他应用集群区分开，建议在此配置中指定本集群存放目录，格式为：hostname1:port1,hostname2:port2,hostname3:port3/chroot/path 。需要注意的是，消费者的参数要和此参数一致。
message.max.bytes	1000000	服务器可以接收到的最大的消息大小。注意此参数要和consumer的maximum.message.size大小一致，否则会因为生产者生产的消息太大导致消费者无法消费。
num.io.threads	8	服务器用来执行读写请求的IO线程数，此参数的数量至少要等于服务器上磁盘的数量。
queued.max.requests	500	I/O线程可以处理请求的队列大小，若实际请求数超过此大小，网络线程将停止接收新的请求。
socket.send.buffer.bytes	100 * 1024	The SO_SNDBUFF buffer the server prefers for socket connections.
socket.receive.buffer.bytes	100 * 1024	The SO_RCVBUFF buffer the server prefers for socket connections.
socket.request.max.bytes	100 * 1024 * 1024	服务器允许请求的最大值，用来防止内存溢出，其值应该小于 Java heap size.
num.partitions	1	默认partition数量，如果topic在创建时没有指定partition数量，默认使用此值，建议改为5
log.segment.bytes	1024 * 1024 * 1024	Segment文件的大小，超过此值将会自动新建一个segment，此值可以被topic级别的参数覆盖。
log.roll.{ms,hours}	24 * 7 hours	新建segment文件的时间，此值可以被topic级别的参数覆盖。
log.retention.{ms,minutes,hours}	7 days	Kafka segment log的保存周期，保存周期超过此时间日志就会被删除。此参数可以被topic级别参数覆盖。数据量大时，建议减小此值。
log.retention.bytes	-1	每个partition的最大容量，若数据量超过此值，partition数据将会被删除。注意这个参数控制的是每个partition而不是topic。此参数可以被log级别参数覆盖。
log.retention.check.interval.ms	5 minutes	删除策略的检查周期
auto.create.topics.enable	true	自动创建topic参数，建议此值设置为false，严格控制topic管理，防止生产者错写topic。
default.replication.factor	1	默认副本数量，建议改为2。
replica.lag.time.max.ms	10000	在此窗口时间内没有收到follower的fetch请求，leader会将其从ISR(in-sync replicas)中移除。
replica.lag.max.messages	4000	如果replica节点落后leader节点此值大小的消息数量，leader节点就会将其从ISR中移除。
replica.socket.timeout.ms	30 * 1000	replica向leader发送请求的超时时间。
replica.socket.receive.buffer.bytes	64 * 1024	The socket receive buffer for network requests to the leader for replicating data.
replica.fetch.max.bytes	1024 * 1024	The number of byes of messages to attempt to fetch for each partition in the fetch requests the replicas send to the leader.
replica.fetch.wait.max.ms	500	The maximum amount of time to wait time for data to arrive on the leader in the fetch requests sent by the replicas to the leader.
num.replica.fetchers	1	Number of threads used to replicate messages from leaders. Increasing this value can increase the degree of I/O parallelism in the follower broker.
fetch.purgatory.purge.interval.requests	1000	The purge interval (in number of requests) of the fetch request purgatory.
zookeeper.session.timeout.ms	6000	ZooKeeper session 超时时间。如果在此时间内server没有向zookeeper发送心跳，zookeeper就会认为此节点已挂掉。此值太低导致节点容易被标记死亡；若太高，.会导致太迟发现节点死亡。
zookeeper.connection.timeout.ms	6000	客户端连接zookeeper的超时时间。
zookeeper.sync.time.ms	2000	H ZK follower落后 ZK leader的时间。
controlled.shutdown.enable	true	允许broker shutdown。如果启用，broker在关闭自己之前会把它上面的所有leaders转移到其它brokers上，建议启用，增加集群稳定性。
auto.leader.rebalance.enable	true	If this is enabled the controller will automatically try to balance leadership for partitions among the brokers by periodically returning leadership to the “preferred” replica for each partition if it is available.
leader.imbalance.per.broker.percentage	10	The percentage of leader imbalance allowed per broker. The controller will rebalance leadership if this ratio goes above the configured value per broker.
leader.imbalance.check.interval.seconds	300	The frequency with which to check for leader imbalance.
offset.metadata.max.bytes	4096	The maximum amount of metadata to allow clients to save with their offsets.
connections.max.idle.ms	600000	Idle connections timeout: the server socket processor threads close the connections that idle more than this.
num.recovery.threads.per.data.dir	1	The number of threads per data directory to be used for log recovery at startup and flushing at shutdown.
unclean.leader.election.enable	true	Indicates whether to enable replicas not in the ISR set to be elected as leader as a last resort, even though doing so may result in data loss.
delete.topic.enable	false	启用deletetopic参数，建议设置为true。
offsets.topic.num.partitions	50	The number of partitions for the offset commit topic. Since changing this after deployment is currently unsupported, we recommend using a higher setting for production (e.g., 100-200).
offsets.topic.retention.minutes	1440	Offsets that are older than this age will be marked for deletion. The actual purge will occur when the log cleaner compacts the offsets topic.
offsets.retention.check.interval.ms	600000	The frequency at which the offset manager checks for stale offsets.
offsets.topic.replication.factor	3	The replication factor for the offset commit topic. A higher setting (e.g., three or four) is recommended in order to ensure higher availability. If the offsets topic is created when fewer brokers than the replication factor then the offsets topic will be created with fewer replicas.
offsets.topic.segment.bytes	104857600	Segment size for the offsets topic. Since it uses a compacted topic, this should be kept relatively low in order to facilitate faster log compaction and loads.
offsets.load.buffer.size	5242880	An offset load occurs when a broker becomes the offset manager for a set of consumer groups (i.e., when it becomes a leader for an offsets topic partition). This setting corresponds to the batch size (in bytes) to use when reading from the offsets segments when loading offsets into the offset manager’s cache.
offsets.commit.required.acks	-1	The number of acknowledgements that are required before the offset commit can be accepted. This is similar to the producer’s acknowledgement setting. In general, the default should not be overridden.
offsets.commit.timeout.ms	5000	The offset commit will be delayed until this timeout or the required number of replicas have received the offset commit. This is similar to the producer request timeout.

5.2 Producer配置信息

属性	默认值	描述
metadata.broker.list		启动时producer查询brokers的列表，可以是集群中所有brokers的一个子集。注意，这个参数只是用来获取topic的元信息用，producer会从元信息中挑选合适的broker并与之建立socket连接。格式是：host1:port1,host2:port2。
request.required.acks	0	参见3.2节介绍
request.timeout.ms	10000	Broker等待ack的超时时间，若等待时间超过此值，会返回客户端错误信息。
producer.type	sync	同步异步模式。async表示异步，sync表示同步。如果设置成异步模式，可以允许生产者以batch的形式push数据，这样会极大的提高broker性能，推荐设置为异步。
serializer.class	kafka.serializer.DefaultEncoder	序列号类，.默认序列化成 byte[] 。
key.serializer.class		Key的序列化类，默认同上。
partitioner.class	kafka.producer.DefaultPartitioner	Partition类，默认对key进行hash。
compression.codec	none	指定producer消息的压缩格式，可选参数为： “none”, “gzip” and “snappy”。关于压缩参见4.1节
compressed.topics	null	启用压缩的topic名称。若上面参数选择了一个压缩格式，那么压缩仅对本参数指定的topic有效，若本参数为空，则对所有topic有效。
message.send.max.retries	3	Producer发送失败时重试次数。若网络出现问题，可能会导致不断重试。
retry.backoff.ms	100	Before each retry, the producer refreshes the metadata of relevant topics to see if a new leader has been elected. Since leader election takes a bit of time, this property specifies the amount of time that the producer waits before refreshing the metadata.
topic.metadata.refresh.interval.ms	600 * 1000	The producer generally refreshes the topic metadata from brokers when there is a failure (partition missing, leader not available…). It will also poll regularly (default: every 10min so 600000ms). If you set this to a negative value, metadata will only get refreshed on failure. If you set this to zero, the metadata will get refreshed after each message sent (not recommended). Important note: the refresh happen only AFTER the message is sent, so if the producer never sends a message the metadata is never refreshed
queue.buffering.max.ms	5000	启用异步模式时，producer缓存消息的时间。比如我们设置成1000时，它会缓存1秒的数据再一次发送出去，这样可以极大的增加broker吞吐量，但也会造成时效性的降低。
queue.buffering.max.messages	10000	采用异步模式时producer buffer 队列里最大缓存的消息数量，如果超过这个数值，producer就会阻塞或者丢掉消息。
queue.enqueue.timeout.ms	-1	当达到上面参数值时producer阻塞等待的时间。如果值设置为0，buffer队列满时producer不会阻塞，消息直接被丢掉。若值设置为-1，producer会被阻塞，不会丢消息。
batch.num.messages	200	采用异步模式时，一个batch缓存的消息数量。达到这个数量值时producer才会发送消息。
send.buffer.bytes	100 * 1024	Socket write buffer size
client.id	“”	The client id is a user-specified string sent in each request to help trace calls. It should logically identify the application making the request.

5.3 Consumer配置信息

属性	默认值	描述
group.id		Consumer的组ID，相同goup.id的consumer属于同一个组。
zookeeper.connect		Consumer的zookeeper连接串，要和broker的配置一致。
consumer.id	null	如果不设置会自动生成。
socket.timeout.ms	30 * 1000	网络请求的socket超时时间。实际超时时间由max.fetch.wait + socket.timeout.ms 确定。
socket.receive.buffer.bytes	64 * 1024	The socket receive buffer for network requests.
fetch.message.max.bytes	1024 * 1024	查询topic-partition时允许的最大消息大小。consumer会为每个partition缓存此大小的消息到内存，因此，这个参数可以控制consumer的内存使用量。这个值应该至少比server允许的最大消息大小大，以免producer发送的消息大于consumer允许的消息。
num.consumer.fetchers	1	The number fetcher threads used to fetch data.
auto.commit.enable	true	如果此值设置为true，consumer会周期性的把当前消费的offset值保存到zookeeper。当consumer失败重启之后将会使用此值作为新开始消费的值。
auto.commit.interval.ms	60 * 1000	Consumer提交offset值到zookeeper的周期。
queued.max.message.chunks	2	用来被consumer消费的message chunks 数量，每个chunk可以缓存fetch.message.max.bytes大小的数据量。
auto.commit.interval.ms	60 * 1000	Consumer提交offset值到zookeeper的周期。
queued.max.message.chunks	2	用来被consumer消费的message chunks 数量，每个chunk可以缓存fetch.message.max.bytes大小的数据量。
fetch.min.bytes	1	The minimum amount of data the server should return for a fetch request. If insufficient data is available the request will wait for that much data to accumulate before answering the request.
fetch.wait.max.ms	100	The maximum amount of time the server will block before answering the fetch request if there isn’t sufficient data to immediately satisfy fetch.min.bytes.
rebalance.backoff.ms	2000	Backoff time between retries during rebalance.
refresh.leader.backoff.ms	200	Backoff time to wait before trying to determine the leader of a partition that has just lost its leader.
auto.offset.reset	largest	What to do when there is no initial offset in ZooKeeper or if an offset is out of range ;smallest : automatically reset the offset to the smallest offset; largest : automatically reset the offset to the largest offset;anything else: throw exception to the consumer
consumer.timeout.ms	-1	若在指定时间内没有消息消费，consumer将会抛出异常。
exclude.internal.topics	true	Whether messages from internal topics (such as offsets) should be exposed to the consumer.
zookeeper.session.timeout.ms	6000	ZooKeeper session timeout. If the consumer fails to heartbeat to ZooKeeper for this period of time it is considered dead and a rebalance will occur.
zookeeper.connection.timeout.ms	6000	The max time that the client waits while establishing a connection to zookeeper.
zookeeper.sync.time.ms	2000	How far a ZK follower can be behind a ZK leader