Recently encountered a problem "too many connections". too many links.
Solution:
1> Restarting mysql can solve it, but it is not a fundamental solution. Because the problem is caused by too small value of max_connections setting. If wait_timeout is set too small, it will cause sql exception, and there will be an exception related to the link being closed,
2> Modify the configuration file /etc/my.cnf and adjust the connection parameters. max_connections: 1000 (the default seems to be 100), the wait_timeout unit seems to be milliseconds.
When the sql prompt is null error.
The result of the query is empty, but it has been used normally before and no related changes have been made. After the query, it is found that the Linux root directory resources have been used and exploded, so that the query cannot be performed. The above is also speculation. However, the system replacement directory situation disappeared.