在 PHP 中获取“MySQL 服务器已经消失”，即使我正在关闭我的数据库连接

Question

I have a PHP Socket Server that I can connect to via Telnet. Once connected, I am able to send messages in a certain format and they're saved in the database.

What happens is that when the PHP Socket receives a message, it opens a Database connection, executes the query, then closes the connection. When it receives another message, it opens the connection again, executes the query, then closes the connection.

So far, this works when I'm sending messages in an interval of 5-10 minutes. However, when the interval increases for over an hour or so, I get a MySQL Server has gone away error.

Upon doing some research, the common solution seems to be increasing the wait time, which is not an option for me. The PHP Socket server is supposed to be open 24/7, and I doubt there's a way to increase the wait time to infinity.

The other option is to check in PHP itself if the MySQL Server has gone away or not, and depending on the result, reset the MySQL Server, and try to establish the connection again.

Does anyone know how to do this in PHP? Or if anyone has other methods in keeping a MySQL Server constantly alive in a PHP Socket server, I would also be open to that idea.

Answer 1

You'll get this error if the database connection has timed out (perhaps from a long-running process since the last time the connection was used).

You can easily check the connection and restore it if necessary with a single command:

$mysqli->ping()

Answer 2

This error means that the connection has been established to the DBMS but has subsequently been lost. I've run sites with hundreds of concurrent connections to the same database instance handling thousands of queries per minute and have only seen this error when a query has been deliberately killed by an admin. You should check your config for the interactive timeout and read your server logs.

Given your description of the error (you really need to gather more data and characterized the circumstances of the error) the only explanation which springs to mind is that there is a deadlock somewhere.

I would question whether there is any benefit to closing the connection after each message (depending on the usage of the system). Artistic phoenix's comment is somewhat confused. But if there are capacity issues then I'd suggest using persistent connections with your existing open/close model, but I doubt that is relevant to the problem you describe here.