kafka 入門筆記（#1）
單機測試
下載版本，解壓
tar -xzf kafka_2.11-0.10.1.1.tgz
cd kafka_2.11-0.10.1.1
啟動服務
Kafka用到了Zookeeper ，所以首先要啟動zookeeper，先啟動一個單實例的zk服務。
bin/zookeeper-server-start.sh config/zookeeper.properties &
啟動Kafka 服務
bin/kafka-server-start.sh config/server.properties
創建 topic
創建一個 名叫“test”的topic ，只有一個分區，一個副本
bin/kafka-topics.sh --create --zookeeper 127.0.0.1:2181 --replication-factor 1 --partitions 1 --topic test
可以通過list 命令查看已創建的topic：
bin/kafka-topics.sh --list --zookeeper 127.0.0.1:2181
test
發送消息
Kafka 使用一個簡單的命令行producer，從文件中或者從標准輸入中讀取消息並發送到服務端。默認的每條命令將發送一條消息
運行producer並在控制台中輸一些消息，這些消息將被發送到服務端：
bin/kafka-console-producer.sh --broker-list 127.0.0.1:9092 --topic test
This is a message /:Enter
This is another message /:Enter
Enter 鍵為push 一條記錄，Ctrl + c 退出發送
啟動consumer
Kafka也有一個命令行consumer可以讀取消息並輸出到標准輸出
bin/kafka-console-consumer.sh --zookeeper 127.0.0.1:2181 --topic test --from-beginning
This is a message
This is another message
如果開兩個命令終端，通過producer 輸入message，consumer 立刻就可以讀取出消息
搭建 多broker 集群
上面啟動了單broker，現在啟動3個broker 組成的集群(機器A,B,C)
機器A:192.168.56.129 ;機器B:192.168.56.131 ;機器C:192.168.56.132
配置
ABC 均照前面安裝好kafka
zookeeper單例：放到機器A(192.168.56.129:2181)
機器A 配置：
broker.id=0
advertised.host.name=192.168.56.129
zookeeper.connect=localhost:2181
修改機器B 中kafka 的配置文件
broker.id=1
advertised.host.name=192.168.56.131
zookeeper.connect=192.168.56.129:2181
修改機器C 中kafka 的配置文件
broker.id=1
advertised.host.name=192.168.56.132
zookeeper.connect=192.168.56.129:2181
為了避免出現 Should not set log end offset on partition 異常，需要將各個broker 的server.properties 中設置
advertised.host.name=192.168.xxx
啟動
機器A上，啟動zookeeper
bin/zookeeper-server-start.sh config/zookeeper.properties &
依次啟動A，B，C上的 kafka broker
bin/kafka-server-start.sh config/server.properties &
創建一個擁有 3個副本的topic
bin/kafka-topics.sh --create --zookeeper 192.168.56.129:2181 --replication-factor 3 --partitions 1 --topic my-replicated-topic
檢測節點信息
bin/kafka-topics.sh --describe --zookeeper 192.168.56.129:2181 --topic my-replicated-topic
Topic:my-replicated-topic PartitionCount:1 ReplicationFactor:3 Configs:
Topic: my-replicated-topic Partition: 0 Leader: 0 Replicas: 0,1,2 Isr: 0,1,2
Leader：負責處理消息的讀寫，leader 是從所有節點中隨機選擇的
Replicas：列出所有的副本節點，不管節點是否在服務中
Isr：是正在服務的節點
注意：broker 運行了3台，但是Isr檢測到 一直只有一台，而且無法寫入消息，結果發現是防火牆的問題
如 : Replicas: 0,1,2 Isr: 0
如producer 寫消息時：Error while fetching metadata with correlation id 11 : {my-replicated-topic2=LEADER_NOT_AVAILABLE}
這時需要把各台機器的 9092 端口打開
vi /etc/sysconfig/iptables
service iptables restart
消息讀寫
同單例；隨意挑選機器，做為producer 向my-replicated-topic 寫入消息，挑另外一台機器做consumer ，消費這些消息
bin/kafka-console-producer.sh --broker-list 127.0.0.1:9092 --topic my-replicated-topic
bin/kafka-console-consumer.sh --zookeeper 192.168.56.129:2181 --from-beginning --topic my-replicated-topic
容錯能力
上面檢測節點信息時，broker.id=0 是作為Leader，現在kill Leader node
在幾秒后，就恢復正常，見其他broker 的日志：
[2017-04-06 16:52:07,601] WARN [ReplicaFetcherThread-0-0], Error in fetch kafka.server.ReplicaFetcherThread$FetchRequest@11acd8a (kafka.server.ReplicaFetcherThread)
java.io.IOException: Connection to 192.168.56.129:9092 (id: 0 rack: null) failed
at kafka.utils.NetworkClientBlockingOps$.awaitReady$1(NetworkClientBlockingOps.scala:83)
at kafka.utils.NetworkClientBlockingOps$.blockingReady$extension(NetworkClientBlockingOps.scala:93)
at kafka.server.ReplicaFetcherThread.sendRequest(ReplicaFetcherThread.scala:248)
at kafka.server.ReplicaFetcherThread.fetch(ReplicaFetcherThread.scala:238)
at kafka.server.ReplicaFetcherThread.fetch(ReplicaFetcherThread.scala:42)
at kafka.server.AbstractFetcherThread.processFetchRequest(AbstractFetcherThread.scala:118)
at kafka.server.AbstractFetcherThread.doWork(AbstractFetcherThread.scala:103)
at kafka.utils.ShutdownableThread.run(ShutdownableThread.scala:63)
[2017-04-06 16:52:08,091] INFO Creating /controller (is it secure? false) (kafka.utils.ZKCheckedEphemeral)
[2017-04-06 16:52:08,093] INFO Result of znode creation is: OK (kafka.utils.ZKCheckedEphemeral)
[2017-04-06 16:52:08,094] INFO 1 successfully elected as leader (kafka.server.ZookeeperLeaderElector)
[2017-04-06 16:52:08,312] INFO [ReplicaFetcherManager on broker 1] Removed fetcher for partitions my-replicated-topic2-0 (kafka.server.ReplicaFetcherManager)
[2017-04-06 16:52:08,314] INFO [ReplicaFetcherThread-0-0], Shutting down (kafka.server.ReplicaFetcherThread)
[2017-04-06 16:52:08,315] INFO [ReplicaFetcherThread-0-0], Stopped (kafka.server.ReplicaFetcherThread)
[2017-04-06 16:52:08,316] INFO [ReplicaFetcherThread-0-0], Shutdown completed (kafka.server.ReplicaFetcherThread)
[2017-04-06 16:52:08,363] INFO New leader is 1 (kafka.server.ZookeeperLeaderElector$LeaderChangeListener)
[2017-04-06 16:52:14,877] INFO Partition [my-replicated-topic,0] on broker 1: Shrinking ISR for partition [my-replicated-topic,0] from 0,1,2 to 1,2 (kafka.cluster.Partition)
再次檢測 節點信息：
[root@localhost kafka_2.11-0.10.1.1]# bin/kafka-topics.sh --describe --zookeeper 192.168.56.129:2181 --topic my-replicated-topic2
Topic:my-replicated-topic2 PartitionCount:1 ReplicationFactor:3 Configs:
Topic: my-replicated-topic2 Partition: 0 Leader: 1 Replicas: 0,1,2 Isr: 1,2
剩下兩台機器，一個生產消息，一個消費消息，都沒有問題
按照 http://www.aboutyun.com/thread-12882-1-1.html 思路進行操作。集群從單機多端口，改用多機器演示