MySQL自动停机的问题处理实战记录

最近帮别人做的一个项目机器上面跑mysql老是隔一段时间就自动停了。刚开始以为是以外停止，也没注意，就手动再启动。可是过了没两天又停止了。

后来仔细查了查mysqld的日志：

2020-05-27t10:15:12.569342z 0 [system] [my-010116] [server] /usr/libexec/mysqld (mysqld 8.0.17) starting as process 19493
2020-05-27t10:15:14.448256z 0 [system] [my-010229] [server] starting crash recovery...
2020-05-27t10:15:14.475411z 0 [system] [my-010232] [server] crash recovery finished.
2020-05-27t10:15:14.691345z 0 [warning] [my-010068] [server] ca certificate ca.pem is self signed.
2020-05-27t10:15:15.677386z 0 [system] [my-010931] [server] /usr/libexec/mysqld: ready for connections. version: '8.0.17'  socket: '/var/lib/mysql/mysql.sock'  port: 3306  source distribution.
2020-05-27t10:15:15.951210z 0 [system] [my-011323] [server] x plugin ready for connections. socket: '/var/lib/mysql/mysqlx.sock' bind-address: '::' port: 33060
2020-05-27t11:26:19.955004z 0 [system] [my-010116] [server] /usr/libexec/mysqld (mysqld 8.0.17) starting as process 19757
2020-05-27t11:26:20.181302z 0 [error] [my-012681] [innodb] mmap(137363456 bytes) failed; errno 12
2020-05-27t11:26:20.181360z 1 [error] [my-012956] [innodb] cannot allocate memory for the buffer pool
2020-05-27t11:26:20.181379z 1 [error] [my-012930] [innodb] plugin initialization aborted with error generic error.
2020-05-27t11:26:20.181401z 1 [error] [my-010334] [server] failed to initialize dd storage engine
2020-05-27t11:26:20.181543z 0 [error] [my-010020] [server] data dictionary initialization failed.
2020-05-27t11:26:20.183642z 0 [error] [my-010119] [server] aborting
2020-05-27t11:26:20.184163z 0 [system] [my-010910] [server] /usr/libexec/mysqld: shutdown complete (mysqld 8.0.17)  source distribution.

上面显示是cannot allocate memory for the buffer pool，无法分配内存给缓存池。马上想到是内存不足，这台机器是1gb的内存，还跑着 nginx 和 php-fpm 。

使用 top 看了看 mysqld 占用的内存达到了48% 。内存占用还是蛮高的。

当然了升级机器配置是比较好的办法，但是毕竟经费有限。所以我们先给它加个swap交换空间：

dd if=/dev/zero of=/swapfile bs=1m count=2048
mkswap /swapfile
swapon /swapfile
systemctl restart mysqld

上面我们加了2gb的交换空间给机器。然后重启 mysqld。再使用top看了看，发现交换空间渐渐被使用了。

睡了一觉起来一看，mysqld服务没有再自动停止，内存占用已经下降到22%，看了看错误日志，也是空的。

嗯，看来还不错嘛。再观察个几天看看，没问题的话应该就好了????????????。

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