pxc 集群节点被kill -9 了拿什么拯救?

集群关机或者异常宕机,重启后想要以IST的方式加入集群,需要考虑集群中是否存在满足的节点,该节点的gcache还存放着停机期间所产生的事物。

重新初始化节点加入集群应该是最后的救命稻草。

这里模拟某个节点意外宕机或者被kill -9 了。

1、查看一下grastate.dat的状态

cat /data/database/pxc3306/grastate.dat网址:yii666.com

# GALERA saved state
version: 2.1
uuid: b1ac3465-05a1-11e8-9776-77ea0d01e209
seqno: -1
safe_to_bootstrap: 0

解释:

  • uuid: 节点所属集群的wsrep_cluster_state_uuid
  • seqno: 整个集群的状态,也就是wsrep_last_committed,也是下次做IST的起始点。如果集群非正常关闭或者正在运行状态,seqno的值为-1
  • safe_to_bootstrap:

正常情况下,节点启动后会从grastate.dat中的seqno开始做IST。如果是非正常关闭,或者某些原因启动失败,这个值会被改为-1,这时候需要借助wsrep_recovery日志进行恢复。

2、wsrep_recovery

启动失败:文章来源地址https://www.yii666.com/article/754307.html

/usr/bin/mysqld_safe --defaults-file=/etc/pxc3306.cnf &

2018-04-03T08:18:47.310804Z mysqld_safe Logging to '/data/database/pxc3306/pxc3306.log'.
2018-04-03T08:18:47.315813Z mysqld_safe Logging to '/data/database/pxc3306/pxc3306.log'.
2018-04-03T08:18:47.371770Z mysqld_safe Starting mysqld daemon with databases from /data/database/pxc3306
2018-04-03T08:18:47.404646Z mysqld_safe WSREP: Running position recovery with --log_error='/data/database/pxc3306/wsrep_recovery.5Dl9fN' --pid-file='/data/database/pxc3306/node-1-recover.pid'

可以看到有个wsrep_recovery.xxxx的日志文件,可以从里面找到Recovered position

或者:

/usr/bin/mysqld_safe --defaults-file=/etc/pxc3306.cnf --wsrep-recover &

3、找到Recovered position

grep Recovered /data/database/pxc3306/wsrep_recovery.5Dl9fN

2018-04-03T08:18:54.534461Z 0 [Note] WSREP: Recovered position: bf26341f-43cb-11e8-a863-62c0eb4d9e79:634

可以看到uuid为:bf26341f-43cb-11e8-a863-62c0eb4d9e79,seqno为:634文章地址https://www.yii666.com/article/754307.html

4、修改grastate.dat

将找到的seqno重新写入:

vim /data/database/pxc3306/grastate.dat

# GALERA saved state
version: 2.1
uuid: bf26341f-43cb-11e8-a863-62c0eb4d9e79
seqno: 634
safe_to_bootstrap: 0

5、寻找合适的donor的节点

这一步很重要,意味着刚宕机的节点能否以IST的方式加入集群

在节点1上执行:

(root@localhost) [mydb_1]>  show status  like 'wsrep_local_cached_downto';
+---------------------------+-------+
| Variable_name | Value |
+---------------------------+-------+
| wsrep_local_cached_downto | 625 |
+---------------------------+-------+
1 row in set (0.00 sec)

在节点2上执行:

(root@localhost) [(none)]> show status  like 'wsrep_local_cached_downto';
+---------------------------+-------+
| Variable_name | Value |
+---------------------------+-------+
| wsrep_local_cached_downto | 678 |
+---------------------------+-------+
1 row in set (0.01 sec)

可以看出:节点1的gcache中缓存的seqno为625,比宕机节点所需要的634要小,意味着节点1的gcache中缓存在宕机节点宕机期间集群所产生的所有事物,因此节点1可以作为donor节点。相反节点2不行。

6、重新启动

指定节点1作为donor:

/usr/bin/mysqld_safe --defaults-file=/etc/pxc3306.cnf --wsrep_sst_donor=pxc-node-0 &网址:yii666.com<

 2018-04-03T08:26:05.689594Z mysqld_safe Logging to '/data/database/pxc3306/pxc3306.log'.
2018-04-03T08:26:05.694919Z mysqld_safe Logging to '/data/database/pxc3306/pxc3306.log'.
2018-04-03T08:26:05.741478Z mysqld_safe Starting mysqld daemon with databases from /data/database/pxc3306
2018-04-03T08:26:05.757902Z mysqld_safe Skipping wsrep-recover forbf26341f-43cb-11e8-a863-62c0eb4d9e79:634 pair
2018-04-03T08:26:05.760692Z mysqld_safe Assigning bf26341f-43cb-11e8-a863-62c0eb4d9e79:634 to wsrep_start_position

恢复正常,查看一下端口,都ok

netstat -ltnpa | grep mysqld文章来源地址:https://www.yii666.com/article/754307.html

tcp        0      0 0.0.0.0:4567                0.0.0.0:*                   LISTEN      4473/mysqld
tcp 0 0 30.0.0.199:33819 30.0.0.198:4567 ESTABLISHED 4473/mysqld
tcp 73021 0 30.0.0.199:4568 30.0.0.198:56028 ESTABLISHED 4473/mysqld
tcp 0 0 30.0.0.199:54614 30.0.0.196:4567 ESTABLISHED 4473/mysqld
tcp 0 0 :::3306 :::* LISTEN 4473/mysqld

可以看到启用了4568端口,IST专用。

6、查看一下状态

登录该节点,查看状态:

mysql> show status like 'wsrep_cluster_status';
+----------------------+---------+
| Variable_name | Value |
+----------------------+---------+
| wsrep_cluster_status | Primary |
+----------------------+---------+
1 row in set (0.01 sec)

随便select一下会发现如下报错:

ERROR 1047 (08S01): WSREP has not yet prepared node for application use

因为目前数据还没同步完,

mysql>  show status like 'wsrep_last_committed';
+----------------------+-------+
| Variable_name | Value |
+----------------------+-------+
| wsrep_last_committed | 655 |
+----------------------+-------+
1 row in set (0.00 sec)

wsrep_last_committed 的值和集群其他节点的一致了,这个节点就恢复ok了。

可以看看节点1的日志:

2018-04-20T07:57:24.655491Z 0 [Note] WSREP: Member 0.0 (pxc-node-2) requested state transfer from '*any*'. Selected 1.0 (pxc-node-0)(SYNCED) as donor.
2018-04-20T07:57:24.655541Z 0 [Note] WSREP: Shifting SYNCED -> DONOR/DESYNCED (TO: 677)
2018-04-20T07:57:24.655702Z 13 [Note] WSREP: IST request: bf26341f-43cb-11e8-a863-62c0eb4d9e79:634-677|tcp://30.0.0.226:4568
2018-04-20T07:57:24.655758Z 13 [Note] WSREP: wsrep_notify_cmd is not defined, skipping notification.
2018-04-20T07:57:24.657885Z 0 [Note] WSREP: Initiating SST/IST transfer on DONOR side (wsrep_sst_xtrabackup-v2 --role 'donor' --address '30.0.0.226:4444/xtrabackup_sst//1' --socket '/tmp/pxc3306.sock' --datadir '/data/database/pxc3306/' --defaults-file '/etc/pxc3306.cnf' --defaults-group-suffix '' --binlog 'host-30-0-0-225-bin' --gtid 'bf26341f-43cb-11e8-a863-62c0eb4d9e79:654' --bypass)
2018-04-20T07:57:24.665844Z 13 [Note] WSREP: DONOR thread signaled with 0
2018-04-20T07:57:24.696526Z 0 [Note] WSREP: async IST sender starting to serve tcp://30.0.0.226:4568 sending 655-677
2018-04-20T07:57:25.632154Z WSREP_SST: [INFO] Bypassing SST. Can work it through IST
2018-04-20T07:57:25.675074Z 0 [Note] WSREP: 1.0 (pxc-node-0): State transfer to 0.0 (pxc-node-1) complete.

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