假如Kafka集群中一个broker宕机无法恢复, 应该如何处理?
今天面试时遇到这个问题, 网上资料说添加新的broker, 是不会自动同步旧数据的.
笨办法
环境介绍
三个broker的集群, zk,kafka装在一起
| broker | IP | broker.id |
|---------|---------------|-----------|
| broker1 | 172.18.12.211 | 211 |
| broker2 | 172.18.12.212 | 212 |
| broker3 | 172.18.12.213 | 213 |
创建测试topic
#./bin/kafka-topics.sh --zookeeper 172.18.12.212:2181 --create --topic test1 --replication-factor 3 --partitions 1
Created topic "test1".
查看
#./bin/kafka-topics.sh --zookeeper 172.18.12.212:2181 --describe --topic test1
Topic:test1 PartitionCount:1 ReplicationFactor:3 Configs:
Topic: test1 Partition: 0 Leader: 213 Replicas: 213,212,211 Isr: 213,212,211
注意当前
Replicas: 213,212,211
Isr: 213,212,211
造一些消息
#./bin/kafka-console-producer.sh --broker-list 172.18.12.212:9092 --topic test1
>1
>2
>3
kill broker2
[root@node024212 ~]# ps -ef| grep kafka
root 17633 1 1 Feb17 ? 00:55:18 /usr/local/java/bin/java -server -Xmx2g - ...
[root@node024212 ~]# kill -9 17633
[root@node024212 ~]# ps -ef| grep kafka
root 21875 21651 0 11:27 pts/2 00:00:00 grep --color=auto kafka
稍等一会, 再次describe test1
#./bin/kafka-topics.sh --zookeeper 172.18.12.212:2181 --describe --topic test1
Topic:test1 PartitionCount:1 ReplicationFactor:3 Configs:
Topic: test1 Partition: 0 Leader: 213 Replicas: 213,212,211 Isr: 213,211
可看到副本仍然是Replicas: 213,212,211
ISR已经变为Isr: 213,211
在212启动新broker
创建一份新的配置文件, 自动一个新的broker
# cp server.properties server2.properties
# vim server2.properties
只修改这两个参数
broker.id=218
log.dirs=/DATA21/kafka/kafka-logs,/DATA22/kafka/kafka-logs,/DATA23/kafka/kafka-logs,/DATA24/kafka/kafka-logs
创建相应目录
mkdir -p /DATA21/kafka/kafka-logs
mkdir -p /DATA22/kafka/kafka-logs
mkdir -p /DATA23/kafka/kafka-logs
mkdir -p /DATA24/kafka/kafka-logs
启动新broker
./bin/kafka-server-start.sh -daemon config/server2.properties
稍等, 查看 test1 状态
#./bin/kafka-topics.sh --zookeeper 172.18.12.212:2181 --describe --topic test1
Topic:test1 PartitionCount:1 ReplicationFactor:3 Configs:
Topic: test2 Partition: 0 Leader: 213 Replicas: 213,212,211 Isr: 213,218,211
可以看到 test1 副本仍然是Replicas: 213,212,211
ISR为Isr: 213,218,211. 也就是说缺失的副本不会自动迁移到新broker上.
使用kafka-reassign-partitions.sh重分配分区
将212删除,添加218
[root@node024211 12:04:48 /usr/local/kafka]
#echo '{"version":1,"partitions":[{"topic":"test1","partition":0,"replicas":[211,213,218]}]}' > increase-replication-factor.json
[root@node024211 12:58:30 /usr/local/kafka]
#./bin/kafka-reassign-partitions.sh --zookeeper 172.18.12.211:2181 --reassignment-json-file increase-replication-factor.json --execute
Current partition replica assignment
{"version":1,"partitions":[{"topic":"test1","partition":0,"replicas":[213,212,211],"log_dirs":["any","any","any"]}]}
Save this to use as the --reassignment-json-file option during rollback
Successfully started reassignment of partitions.
[root@node024211 12:58:49 /usr/local/kafka]
#./bin/kafka-reassign-partitions.sh --zookeeper 172.18.12.211:2181 --reassignment-json-file increase-replication-factor.json --verify
Status of partition reassignment:
Reassignment of partition test1-0 completed successfully
查看topic信息
#./bin/kafka-topics.sh --zookeeper 172.18.12.212:2181 --describe --topic test1
Topic:test1 PartitionCount:1 ReplicationFactor:3 Configs:
Topic: test1 Partition: 0 Leader: 213 Replicas: 211,213,218 Isr: 213,211,218
验证218是否有全部数据
虽然看副本信息中已经有了218, 但是218是否包含旧消息呢?
我的办法是, kill 211,213, 然后–from-beginning 消费218数据, 实际测试也是可以的
#./bin/kafka-console-consumer.sh --bootstrap-server 172.18.12.212:9092 --topic test1 --from-beginning
1
2
3
4
5
6
7
8
9
10
11
11
看了下211 218的log文件大小也是一样的
[2019-02-21 13:29:19]#ls -l /DATA22/kafka/kafka-logs/test1-0/
[2019-02-21 13:29:19]total 8
[2019-02-21 13:29:19]-rw-r--r--. 1 root root 10485760 Feb 21 12:58 00000000000000000000.index
[2019-02-21 13:29:19]-rw-r--r--. 1 root root 381 Feb 21 13:00 00000000000000000000.log
[2019-02-21 13:29:19]-rw-r--r--. 1 root root 10485756 Feb 21 12:58 00000000000000000000.timeindex
[2019-02-21 13:29:19]-rw-r--r--. 1 root root 16 Feb 21 13:00 leader-epoch-checkpoint
更简单的办法
通过阅读文档发现
https://cwiki.apache.org/confluence/display/KAFKA/FAQ#FAQ-Howtoreplaceafailedbroker
这上面说的,如果服务器真的坏了, 只需要新启动一个broker, 把broker.id设置为 损坏的那个broker的id, 就会自动复制过去丢失的数据。
实际测试了一下, 确实可以恢复。