问题背景

部门的测试环境，Mogdb的一主一备集群，版本是2.1.1。双机在断电之前，Mogdb集群正常，断电重启后，操作系统启动正常，启动mogdb集群，启动失败。
主机ip：192.168.137.110
备机ip：192.168.137.111

问题现象

$ gs_om -t start
Starting cluster.
=========================================
=========================================
[GAUSS-53600]: Can not start the database, the cmd is . /home/omm/.bashrc; python3 '/dbdata/app/tools/script/local/StartInstance.py' -U omm -R /dbdata/app/mogdb -t 300 --security-mode=off,  Error:
[FAILURE] master:
[GAUSS-51607] : Failed to start instance. Error: Please check the gs_ctl log for failure details.
[2022-09-08 17:47:43.905][1718][][gs_ctl]: gs_ctl started,datadir is /dbdata/data/db1 
[2022-09-08 17:47:51.180][1718][][gs_ctl]: waiting for server to start...
.0 LOG:  [Alarm Module]can not read GAUSS_WARNING_TYPE env.
	
0 LOG:  [Alarm Module]Host Name: master 
	
0 LOG:  [Alarm Module]Host IP: 192.168.137.110 
	
0 LOG:  [Alarm Module]Cluster Name: dbCluster 
	
..2022-09-08 17:47:53.433 6319ba47.1 [unknown] 140561613260352 [unknown] 0 dn_6001_6002 DB010  0 [REDO] LOG:  Recovery parallelism, cpu count = 2, max = 4, actual = 2
2022-09-08 17:47:53.433 6319ba47.1 [unknown] 140561613260352 [unknown] 0 dn_6001_6002 DB010  0 [REDO] LOG:  ConfigRecoveryParallelism, true_max_recovery_parallelism:4, max_recovery_parallelism:4
Failed to read gaussdb.state: 0Failed to set gaussdb.state with UNKNOWN_STATE[2022-09-08 17:47:54.185][1718][][gs_ctl]: waitpid 1722 failed, exitstatus is 256, ret is 2

[2022-09-08 17:47:54.185][1718][][gs_ctl]: stopped waiting
[2022-09-08 17:47:54.185][1718][][gs_ctl]: could not start server
Examine the log output.[FAILURE] standby:
[GAUSS-51607] : Failed to start instance. Error: Please check the gs_ctl log for failure details.
[2022-09-08 17:48:00.805][1344][][gs_ctl]: gs_ctl started,datadir is /dbdata/data/db1 
[2022-09-08 17:48:02.935][1344][][gs_ctl]: waiting for server to start...
.0 LOG:  [Alarm Module]can not read GAUSS_WARNING_TYPE env.
	
0 LOG:  [Alarm Module]Host Name: standby 
	
0 LOG:  [Alarm Module]Host IP: 192.168.137.111 
	
0 LOG:  [Alarm Module]Cluster Name: dbCluster 
	
2022-09-08 17:48:03.632 6319ba53.1 [unknown] 139726745114176 [unknown] 0 dn_6001_6002 DB010  0 [REDO] LOG:  Recovery parallelism, cpu count = 2, max = 4, actual = 2
2022-09-08 17:48:03.632 6319ba53.1 [unknown] 139726745114176 [unknown] 0 dn_6001_6002 DB010  0 [REDO] LOG:  ConfigRecoveryParallelism, true_max_recovery_parallelism:4, max_recovery_parallelism:4
Failed to read gaussdb.state: 0Failed to set gaussdb.state with UNKNOWN_STATE[2022-09-08 17:48:03.937][1344][][gs_ctl]: waitpid 1347 failed, exitstatus is 256, ret is 2

[2022-09-08 17:48:03.937][1344][][gs_ctl]: stopped waiting
[2022-09-08 17:48:03.937][1344][][gs_ctl]: could not start server
Examine the log output.
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问题分析

1.查看集群状况

  #su - omm
$ gs_om -t status --detail
[   Cluster State   ]

cluster_state   : Unavailable
redistributing  : No
current_az      : AZ_ALL

[  Datanode State   ]

    node   node_ip         port      instance                 state
-----------------------------------------------------------------------------------
1  master  192.168.137.110 26000      6001 /dbdata/data/db1   P Down    Manually stopped
2  standby 192.168.137.111 26000      6002 /dbdata/data/db1   S Down    Manually stopped
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2.查看数据库版本

$ gs_ctl --V
gs_ctl (openGauss) 9.2.4
$ mogdb -V
gaussdb (MogDB 2.1.1 build b5f25b20) compiled at 2022-03-21 14:42:30 commit 0 last mr 
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3.查看日志

#查询日志目录

cat /dbdata/data/db1/postgresql.conf |grep -i log_dir
log_directory = '/dbdata/log/omm/pg_log/dn_6001'		# directory where log files are written,
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查看日志列表

  cd /dbdata/log/omm/pg_log/dn_6001
ls -l
-rw-------  1 omm dbgrp 100076 Sep  8 15:47 postgresql-2022-09-08_144356.log
-rw-------  1 omm dbgrp      0 Sep  8 17:04 postgresql-2022-09-08_170442.log
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最新日志已经不打印。

4.查看官方手册

根据错误码查看官方手册，[GAUSS-53600]和[GAUSS-51607]

GAUSS-53600: "CA password must contain at least eight characters."

SQLSTATE: 无

错误原因: 系统内部错误。

解决办法: 请联系技术支持工程师提供技术支持。

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GAUSS-51607: "Failed to start %s."

错误原因: 启动集群/节点/实例失败。

解决办法: 1.检查网络连接是否正常；2.检查配置文件是否正确。

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5.查看源码

报错里面提到文件gaussdb.state，在官方手册搜gaussdb.state，没有发现主题。
根据报错“Failed to read gaussdb.state”语句，查看官方源码，找到相关代码
postmaster.cpp

  /*
 * Only update gaussdb.state file's state field.
 *
 * PARAMETERS:
 *      state: INPUT new state
 * RETURN:
 *      true if success, otherwise false.
 *
 * NOTE: unsafe function is not expected here since it is referred in signal handler.
 */

bool SetDBStateFileState(DbState state, bool optional)
{
    /* do nothing while core dump be appeared so early. */
    if (strlen(gaussdb_state_file) > 0) {
        char temppath[MAXPGPATH] = {0};
        GaussState s;
        int len = 0;

        /* zero it in case gaussdb.state doesn't exist. */
        int rc = memset_s(&s, sizeof(GaussState), 0, sizeof(GaussState));
        securec_check_c(rc, "\0", "\0");

        rc = snprintf_s(temppath, MAXPGPATH, MAXPGPATH - 1, "%s.temp", gaussdb_state_file);
        securec_check_intval(rc, , false);

        /* Write the new content into a temp file and rename it at last. */
        int fd = open(gaussdb_state_file, O_RDONLY);
        if (fd == -1) {
            if (errno == ENOENT && optional) {
                write_stderr("gaussdb.state does not exist, and skipt setting since it is optional.");
                return true;
            } else {
                write_stderr("Failed to open gaussdb.state.temp: %d", errno);
                return false;
            }
        }

        /* Read old content from file. */
        len = read(fd, &s, sizeof(GaussState));
        /* sizeof(int) is for current_connect_idx of GaussState */
        if ((len != sizeof(GaussState)) && (len != sizeof(GaussState) - sizeof(int))) {
            write_stderr("Failed to read gaussdb.state: %d", errno);
            (void)close(fd);
            return false;
        }
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在源码文件postmaster.cpp里面发现代码函数SetDBStateFileState。在启动Mogdb的时候，会通过读取gaussdb.state来设置数据库运行状态，而在读取gaussdb.state的字节长度大小比较失败，输出错误，返回false，终止启动。

问题解决

1.查看gaussdb.state

cd /dbdata/data/db1/
ll gaussdb.state
-rw-------  1 omm dbgrp       0 Sep  8 17:04 gaussdb.state
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权限和属组正常，但是文件大小0异常。

  cat gaussdb.state
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返回空

  vi gaussdb.state
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返回空

2.替换gaussdb.state

  rm -f gaussdb.state
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从另外的mogdb正常环境复制一个gaussdb.state到主机和备机

  cp gaussdb.state
ll gaussdb.state
-rw-r--r-- 1 root root      72 Sep  9 15:14 gaussdb.state
chown omm.dbgrp gaussdb.state
ll gaussdb.state
-rw-r--r-- 1 omm dbgrp      72 Sep  9 15:24 gaussdb.state
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查看正常的gaussdb.state

  cat gaussdb.state
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返回空

  vi gaussdb.state
^B^@^@^@^A^@^@^@^A^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@
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3.启动集群，并查看集群状态

  gs_om -t start
Starting cluster.
=========================================
[SUCCESS] master

[SUCCESS] standby

=========================================
Successfully started.

gs_om -t status --detail
[   Cluster State   ]

cluster_state   : Normal
redistributing  : No
current_az      : AZ_ALL

[  Datanode State   ]

    node   node_ip         port      instance                 state
-----------------------------------------------------------------------------------
1  master  192.168.137.110 26000      6001 /dbdata/data/db1   P Primary Normal
2  standby 192.168.137.111 26000      6002 /dbdata/data/db1   S Standby Normal
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发散思维验证

1.误删gaussdb.state是否可以正常启动？

删除文件gaussdb.state

  rm -f gaussdb.state
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启动数据库

gs_ctl -D /dbdata/data/db1/ start
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启动成功，新生成一个gaussdb.state

2.修改gaussdb.state里面内容是否可以正常启动？

vi gaussdb.state
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清空已有内容，随便插入几个数字，保存
启动数据库

gs_ctl -D /dbdata/data/db1/ start
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重现上面故障

清除非法内容，插回字符长串，保存

^B^@^@^@^A^@^@^@^A^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@
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启动数据库成功

总结

1.数据库要保障正常启动和关停，保障供电正常，忌突然断电，容易造成数据文件损坏，数据库异常。
2.数据库无法启动，通过报错或者错误日志分析原因，可以查询官方手册，可以官方源码搜关键字词等

参考文档

Mogdb官方手册https://docs.mogdb.io/zh/mogdb/v3.0/overview
openGauss源码地址：https://gitee.com/opengauss/openGauss-server/blob/master/src/gausskernel/process/postmaster/postmaster.cpp#L877