因为没法读取database，zookeeper启动失败

最近咱们的集群状态异常，发现启动zk的时候一直失败，看了日志是真的心酸，5s挂机，这要是在开黑，分分钟被举报了，一开始真的没想懂启动zk为何这么难，并且很稳定的在5s左右失败，经过时间能够判断这个进程尚未彻底启动，在这个时间段内，顶多就是在init状态

[root@ZYC3-AQGK-LJCL-SRV05 deployer]# systemctl status zookeeper
● zookeeper.service - ZooKeeper Service
   Loaded: loaded (/etc/systemd/system/zookeeper.service; enabled; vendor preset: disabled)
   Active: active (running) since Mon 2020-03-23 11:29:21 CST; 4s ago
     Docs: http://zookeeper.apache.org
  Process: 31011 ExecStop=/opt/zookeeper/zookeeper-prod/bin/zkServer.sh stop /opt/zookeeper/zookeeper-prod/conf/zoo.cfg (code=exited, status=0/SUCCESS)
  Process: 31129 ExecStart=/opt/zookeeper/zookeeper-prod/bin/zkServer.sh start /opt/zookeeper/zookeeper-prod/conf/zoo.cfg (code=exited, status=0/SUCCESS)
 Main PID: 31138 (java)
   CGroup: /system.slice/zookeeper.service
           └─31138 java -Dzookeeper.log.dir=. -Dzookeeper.root.logger=INFO,CONSOLE -cp /opt/zookeeper/zookeeper-prod/bin/../build/classes:/opt/zookeeper/zookeeper-prod/bin/../build/lib/*.jar:/opt/zookeeper/zoo...

Mar 23 11:29:20 ZYC3-AQGK-LJCL-SRV05 systemd[1]: Starting ZooKeeper Service...
Mar 23 11:29:20 ZYC3-AQGK-LJCL-SRV05 zkServer.sh[31129]: ZooKeeper JMX enabled by default
Mar 23 11:29:20 ZYC3-AQGK-LJCL-SRV05 zkServer.sh[31129]: Using config: /opt/zookeeper/zookeeper-prod/conf/zoo.cfg
Mar 23 11:29:21 ZYC3-AQGK-LJCL-SRV05 zkServer.sh[31129]: Starting zookeeper ... STARTED
Mar 23 11:29:21 ZYC3-AQGK-LJCL-SRV05 systemd[1]: Started ZooKeeper Service.
[root@ZYC3-AQGK-LJCL-SRV05 deployer]# systemctl status zookeeper
● zookeeper.service - ZooKeeper Service
   Loaded: loaded (/etc/systemd/system/zookeeper.service; enabled; vendor preset: disabled)
   Active: active (running) since Mon 2020-03-23 11:29:21 CST; 5s ago
     Docs: http://zookeeper.apache.org
  Process: 31011 ExecStop=/opt/zookeeper/zookeeper-prod/bin/zkServer.sh stop /opt/zookeeper/zookeeper-prod/conf/zoo.cfg (code=exited, status=0/SUCCESS)
  Process: 31129 ExecStart=/opt/zookeeper/zookeeper-prod/bin/zkServer.sh start /opt/zookeeper/zookeeper-prod/conf/zoo.cfg (code=exited, status=0/SUCCESS)
 Main PID: 31138 (java)
   CGroup: /system.slice/zookeeper.service
           └─31138 java -Dzookeeper.log.dir=. -Dzookeeper.root.logger=INFO,CONSOLE -cp /opt/zookeeper/zookeeper-prod/bin/../build/classes:/opt/zookeeper/zookeeper-prod/bin/../build/lib/*.jar:/opt/zookeeper/zoo...

Mar 23 11:29:20 ZYC3-AQGK-LJCL-SRV05 systemd[1]: Starting ZooKeeper Service...
Mar 23 11:29:20 ZYC3-AQGK-LJCL-SRV05 zkServer.sh[31129]: ZooKeeper JMX enabled by default
Mar 23 11:29:20 ZYC3-AQGK-LJCL-SRV05 zkServer.sh[31129]: Using config: /opt/zookeeper/zookeeper-prod/conf/zoo.cfg
Mar 23 11:29:21 ZYC3-AQGK-LJCL-SRV05 zkServer.sh[31129]: Starting zookeeper ... STARTED
Mar 23 11:29:21 ZYC3-AQGK-LJCL-SRV05 systemd[1]: Started ZooKeeper Service.
[root@ZYC3-AQGK-LJCL-SRV05 deployer]# systemctl status zookeeper
● zookeeper.service - ZooKeeper Service
   Loaded: loaded (/etc/systemd/system/zookeeper.service; enabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since Mon 2020-03-23 11:29:26 CST; 706ms ago
     Docs: http://zookeeper.apache.org
  Process: 31225 ExecStop=/opt/zookeeper/zookeeper-prod/bin/zkServer.sh stop /opt/zookeeper/zookeeper-prod/conf/zoo.cfg (code=exited, status=0/SUCCESS)
  Process: 31129 ExecStart=/opt/zookeeper/zookeeper-prod/bin/zkServer.sh start /opt/zookeeper/zookeeper-prod/conf/zoo.cfg (code=exited, status=0/SUCCESS)
 Main PID: 31138 (code=exited, status=1/FAILURE)

Mar 23 11:29:20 ZYC3-AQGK-LJCL-SRV05 zkServer.sh[31129]: Using config: /opt/zookeeper/zookeeper-prod/conf/zoo.cfg
Mar 23 11:29:21 ZYC3-AQGK-LJCL-SRV05 zkServer.sh[31129]: Starting zookeeper ... STARTED
Mar 23 11:29:21 ZYC3-AQGK-LJCL-SRV05 systemd[1]: Started ZooKeeper Service.
Mar 23 11:29:26 ZYC3-AQGK-LJCL-SRV05 systemd[1]: zookeeper.service: main process exited, code=exited, status=1/FAILURE
Mar 23 11:29:26 ZYC3-AQGK-LJCL-SRV05 zkServer.sh[31225]: ZooKeeper JMX enabled by default
Mar 23 11:29:26 ZYC3-AQGK-LJCL-SRV05 zkServer.sh[31225]: Using config: /opt/zookeeper/zookeeper-prod/conf/zoo.cfg
Mar 23 11:29:26 ZYC3-AQGK-LJCL-SRV05 zkServer.sh[31225]: Stopping zookeeper ... /opt/zookeeper/zookeeper-prod/bin/zkServer.sh: 第 182 行:kill: (31138) - 没有那个进程
Mar 23 11:29:26 ZYC3-AQGK-LJCL-SRV05 zkServer.sh[31225]: STOPPED
Mar 23 11:29:26 ZYC3-AQGK-LJCL-SRV05 systemd[1]: Unit zookeeper.service entered failed state.
Mar 23 11:29:26 ZYC3-AQGK-LJCL-SRV05 systemd[1]: zookeeper.service failed.

看到日志中提到/opt/zookeeper/zookeeper-prod/conf/zoo.cfg因此就去这个目录下看看有没有什么值得挖掘的内容。毕竟conf能够猜想是一个配置文件夹，讲道理应该是有log或者output之类的文件夹，里面存放着运行日志，特别是error日志，按照这个思路就能够进行相关的排查了。
以后发现/opt/zookeeper/zookeeper-prod/bin目录中有个zookeeper.out文件，这个是执行的细节，能够看下内容，而后cat一下，问题就很明朗了

2020-03-23 11:36:58,799 [myid:] - INFO  [main:QuorumPeerConfig@136] - Reading configuration from: /opt/zookeeper/zookeeper-prod/bin/../conf/zoo.cfg
2020-03-23 11:36:58,814 [myid:] - INFO  [main:QuorumPeer$QuorumServer@184] - Resolved hostname: 10.153.115.26 to address: /10.153.115.26
2020-03-23 11:36:58,815 [myid:] - INFO  [main:QuorumPeer$QuorumServer@184] - Resolved hostname: 10.153.115.25 to address: /10.153.115.25
2020-03-23 11:36:58,816 [myid:] - INFO  [main:QuorumPeer$QuorumServer@184] - Resolved hostname: 10.153.115.24 to address: /10.153.115.24
2020-03-23 11:36:58,816 [myid:] - INFO  [main:QuorumPeer$QuorumServer@184] - Resolved hostname: 10.153.115.29 to address: /10.153.115.29
2020-03-23 11:36:58,816 [myid:] - INFO  [main:QuorumPeer$QuorumServer@184] - Resolved hostname: 10.153.115.28 to address: /10.153.115.28
2020-03-23 11:36:58,816 [myid:] - INFO  [main:QuorumPeer$QuorumServer@184] - Resolved hostname: 10.153.115.27 to address: /10.153.115.27
2020-03-23 11:36:58,816 [myid:] - WARN  [main:QuorumPeerConfig@354] - Non-optimial configuration, consider an odd number of servers.
2020-03-23 11:36:58,816 [myid:] - INFO  [main:QuorumPeerConfig@398] - Defaulting to majority quorums
2020-03-23 11:36:58,821 [myid:5] - INFO  [main:DatadirCleanupManager@78] - autopurge.snapRetainCount set to 3
2020-03-23 11:36:58,821 [myid:5] - INFO  [main:DatadirCleanupManager@79] - autopurge.purgeInterval set to 24
2020-03-23 11:36:58,822 [myid:5] - INFO  [PurgeTask:DatadirCleanupManager$PurgeTask@138] - Purge task started.
2020-03-23 11:36:58,837 [myid:5] - INFO  [PurgeTask:DatadirCleanupManager$PurgeTask@144] - Purge task completed.
2020-03-23 11:36:58,839 [myid:5] - INFO  [main:QuorumPeerMain@130] - Starting quorum peer
2020-03-23 11:36:58,849 [myid:5] - INFO  [main:ServerCnxnFactory@117] - Using org.apache.zookeeper.server.NIOServerCnxnFactory as server connection factory
2020-03-23 11:36:58,856 [myid:5] - INFO  [main:NIOServerCnxnFactory@89] - binding to port 0.0.0.0/0.0.0.0:2181
2020-03-23 11:36:58,861 [myid:5] - INFO  [main:QuorumPeer@1158] - tickTime set to 2000
2020-03-23 11:36:58,861 [myid:5] - INFO  [main:QuorumPeer@1204] - initLimit set to 10
2020-03-23 11:36:58,861 [myid:5] - INFO  [main:QuorumPeer@1178] - minSessionTimeout set to -1
2020-03-23 11:36:58,862 [myid:5] - INFO  [main:QuorumPeer@1189] - maxSessionTimeout set to -1
2020-03-23 11:36:58,871 [myid:5] - INFO  [main:QuorumPeer@1467] - QuorumPeer communication is not secured!
2020-03-23 11:36:58,871 [myid:5] - INFO  [main:QuorumPeer@1496] - quorum.cnxn.threads.size set to 20
2020-03-23 11:36:58,872 [myid:5] - INFO  [main:FileSnap@86] - Reading snapshot /data/zookeeper/data/version-2/snapshot.b91d0000003c
2020-03-23 11:36:59,290 [myid:5] - ERROR [main:QuorumPeer@692] - Unable to load database on disk
java.io.IOException: The accepted epoch, ba86 is less than the current epoch, ba87
    at org.apache.zookeeper.server.quorum.QuorumPeer.loadDataBase(QuorumPeer.java:689)
    at org.apache.zookeeper.server.quorum.QuorumPeer.start(QuorumPeer.java:635)
    at org.apache.zookeeper.server.quorum.QuorumPeerMain.runFromConfig(QuorumPeerMain.java:170)
    at org.apache.zookeeper.server.quorum.QuorumPeerMain.initializeAndRun(QuorumPeerMain.java:114)
    at org.apache.zookeeper.server.quorum.QuorumPeerMain.main(QuorumPeerMain.java:81)
2020-03-23 11:36:59,292 [myid:5] - ERROR [main:QuorumPeerMain@92] - Unexpected exception, exiting abnormally
java.lang.RuntimeException: Unable to run quorum server 
    at org.apache.zookeeper.server.quorum.QuorumPeer.loadDataBase(QuorumPeer.java:693)
    at org.apache.zookeeper.server.quorum.QuorumPeer.start(QuorumPeer.java:635)
    at org.apache.zookeeper.server.quorum.QuorumPeerMain.runFromConfig(QuorumPeerMain.java:170)
    at org.apache.zookeeper.server.quorum.QuorumPeerMain.initializeAndRun(QuorumPeerMain.java:114)
    at org.apache.zookeeper.server.quorum.QuorumPeerMain.main(QuorumPeerMain.java:81)
Caused by: java.io.IOException: The accepted epoch, ba86 is less than the current epoch, ba87
    at org.apache.zookeeper.server.quorum.QuorumPeer.loadDataBase(QuorumPeer.java:689)
    ... 4 more

日志中写着，正在读取zk的快照，而后就报错了，没法载入磁盘上的数据库，那么！我就把快照删了snapshot.b91d0000003c，让其本身从新生成快照文件，完事了。

2020-03-23 11:36:58,872 [myid:5] - INFO  [main:FileSnap@86] - Reading snapshot /data/zookeeper/data/version-2/snapshot.b91d0000003c
2020-03-23 11:36:59,290 [myid:5] - ERROR [main:QuorumPeer@692] - Unable to load database on disk

酸爽

[root@ZYC3-AQGK-LJCL-SRV05 deployer]# systemctl status zookeeper
● zookeeper.service - ZooKeeper Service
   Loaded: loaded (/etc/systemd/system/zookeeper.service; enabled; vendor preset: disabled)
   Active: active (running) since Mon 2020-03-23 12:12:08 CST; 5min ago
     Docs: http://zookeeper.apache.org
  Process: 25348 ExecStop=/opt/zookeeper/zookeeper-prod/bin/zkServer.sh stop /opt/zookeeper/zookeeper-prod/conf/zoo.cfg (code=exited, status=0/SUCCESS)
  Process: 25658 ExecStart=/opt/zookeeper/zookeeper-prod/bin/zkServer.sh start /opt/zookeeper/zookeeper-prod/conf/zoo.cfg (code=exited, status=0/SUCCESS)
 Main PID: 25667 (java)
   CGroup: /system.slice/zookeeper.service
           └─25667 java -Dzookeeper.log.dir=. -Dzookeeper.root.logger=INFO,CONSOLE -cp /opt/zookeeper/zookeeper-prod/bin/../build/classes:/opt/zookeeper/zookeeper-prod/bin/../build/lib/*.jar:/opt/zookeeper/zoo...

Mar 23 12:12:07 ZYC3-AQGK-LJCL-SRV05 systemd[1]: Starting ZooKeeper Service...
Mar 23 12:12:07 ZYC3-AQGK-LJCL-SRV05 zkServer.sh[25658]: ZooKeeper JMX enabled by default
Mar 23 12:12:07 ZYC3-AQGK-LJCL-SRV05 zkServer.sh[25658]: Using config: /opt/zookeeper/zookeeper-prod/conf/zoo.cfg
Mar 23 12:12:08 ZYC3-AQGK-LJCL-SRV05 zkServer.sh[25658]: Starting zookeeper ... STARTED
Mar 23 12:12:08 ZYC3-AQGK-LJCL-SRV05 systemd[1]: Started ZooKeeper Service.

由于zk每次运行的时候都会有个一快照文件，这个是状态恢复用的，因为这台主机以前磁盘满了，导入zk没法及时写入消息，以后咱们将设备进行重启，应该就是这个时候，快照文件写入失败致使的。不过这个也不是万能解法，也是要具体问题具体分析，由于在集群中，把快照文件删了，后续想恢复数据库状态就难了，不过幸好咱们的zk是6节点的，另外五个节点正常，因此这么操做是容许的。
至此收工：）