部署的error和排查，注意服务器内存占用！

mysqladmin: connect to server at 'localhost' failed error: 'Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)' Check that mysqld is running and that the socket: '/var/run/mysqld/mysqld.sock' exists!

 

开始能登陆，后来就断开了

We're sorry, but something went wrong.
If you are the application owner check the logs for more information.

 

重新启动service nginx restart后有时可以进入网址，但🔗http://39.98.75.113/addresses/new：有2种情况：

1. 正常链接。这时我打开的是chrome或者safari。
2. 同时打开chrome, safari用不同的账号登陆网址。
   1. 成功同步更新
   2. 报告❌。

？？猜测是和内存有关，512的服务器内存太小了。

 

通过命令/etc/init.d/mysql status查看mysql的状态：

/etc/init.d/mysql status
或者：
service mysql status

 正常情况：

<E2><97><8F> mysql.service - MySQL Community Server
   Loaded: loaded (/lib/systemd/system/mysql.service; enabled; vendor preset: enabled)
   Active: active (running) since Sat 2018-11-10 18:33:42 CST; 52min ago
  Process: 803 ExecStartPost=/usr/share/mysql/mysql-systemd-start post (code=exited, status=0/SUCCESS)
  Process: 691 ExecStartPre=/usr/share/mysql/mysql-systemd-start pre (code=exited, status=0/SUCCESS)
 Main PID: 802 (mysqld)
   CGroup: /system.slice/mysql.service
           <E2><94><94><E2><94><80>802 /usr/sbin/mysqld

Nov 10 18:33:39 iZ8vbcqz91cgdxkf2tcrsvZ systemd[1]: Starting MySQL Community Server...
Nov 10 18:33:42 iZ8vbcqz91cgdxkf2tcrsvZ systemd[1]: Started MySQL Community Server.

 

失败情况: 显示正激活activing, 有failure.

<E2><97><8F> mysql.service - MySQL Community Server
   Loaded: loaded (/lib/systemd/system/mysql.service; enabled; vendor preset: enabled)
   Active: activing since Sat 2018-11-10 18:33:42 CST; 52min ago
  Process: 803 ExecStartPost=/usr/share/mysql/mysql-systemd-start post 
(code=exited, status=failure)
  Process: 691 ExecStartPre=/usr/share/mysql/mysql-systemd-start pre (code=exited, status=0/SUCCESS)
 Main PID: 802 (mysqld)
   CGroup: /system.slice/mysql.service
           <E2><94><94><E2><94><80>802 /usr/sbin/mysqld

Nov 10 18:33:39 iZ8vbcqz91cgdxkf2tcrsvZ systemd[1]: Starting MySQL Community Server...
Nov 10 18:33:42 iZ8vbcqz91cgdxkf2tcrsvZ systemd[1]: Started MySQL Community Server.

 

其他问题：

在远端进 rails console后， 有时候能链接上mysql, 有时候就显示Mysql2::Error::ConnectionError

这是因为mysql没有正常开启。

用deploy身份：

cd ~/.your_project/current

执行 bundle exec rails c -e production

 

服务器端输入：mysql -u root -p 

Enter password:
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)

 

 

最后重启动服务器，一切暂时ok.