来自node.js websocket服务器的间歇性500错误

Question

I have a websocket node.js app (game server) that runs a multiplayer html5 game.

The game has a website also. The game server and the website are on the same Apache VPS.

The game server uses mysql to store and retrieve data using mysql pooling from the node.js mysql package.

It works fine 99% of the time, but intermittently, at a random point, it will all of a sudden stop being able to get a mysql connection.

When this happens the website stops working and shows a 500 http error. I believe that this is whats causing the problem in the game server. Because of the 500 http error, mysql can no longer be connected to and thus pool.getConnection no longer works in the game server.

I find it strange that even though Apache is throwing up a 500 error, the game server can still be accessed successfully through a websocket as usual. The only thing that appears to have stopped working inside the game server is mysql. The game client connects to the game server via websocket and the functions work correctly, except for being able to connect to mysql.

If I ctrl+c the game server to stop the node.js app (game server) then the 500 error goes away. The website instantly serves up again, and then if I restarting the game server, mysql is now working again.

Obviously something in the game server is causing this to happen. So far i cannot find what it is. I am stuck now, i've spent a full week trying everything i could think of to debug this.

After running debug mode on mysql, im seeing this;

<-- ErrorPacket
ErrorPacket {
fieldCount: 255,
errno: 1203,
sqlStateMarker: '#',
sqlState: '42000',
message: 'User (i've hidden this) already has more than 
\'max_user_connections\' 
active connections' }

But I have it set to 100000 connections. No way is there that many being used. Every time I finish with a connection I use connection.release() to put it back into the pool. What do I need to do to fix this?

Please, any suggestion you have to debug this is greatly appreciated!

Thanks in advance.

here is the way i'm using mysql in the game server

const mysql = require('mysql');

const pool = mysql.createPool({
        connectionLimit : 100000,
        host     : '***********',
        user     : '***********',
        password : "'***********",
        database : '***********',
        debug    :  true
});


pool.getConnection(function(err,connection){

    if (err) {
        console.log(err);
        return false;
    }   

    connection.query("select * from aTable  ",function(err,rows){

        if(err) {
            console.log(err);
            connection.release();
            return false;

        }

        // dos stuff here

        connection.release();
    })

})

1 thing i am wondering, if there is an error in the top error catch block here ->

 pool.getConnection(function(err,connection){

        if (err) {
            console.log(err);
            return false;
        }

Then the connection is not released right? So that would keep a connection alive and this is whats causing the problem? over time an error happens here and there, after a random amount of time, enough of these happen and that's what is causing it? it's like a build up of open connections???

Answer 1

This was the mistake i was making;

pool.getConnection(function(err,connection){

    if (err) {
        console.log(err);
        return false;
    }   

    connection.query("select * from aTable  ",function(err,rows){

        if(err) {
            console.log(err);
            connection.release();
            return false;

        }

        if(somethingrelevant){

            // do stuff

            connection.release();

        }

    })

})

And that meant that if somethingrelevant didn't happen, then the connection would stay open. My pool would continue to open new connections but they weren't always being put back.