ECONNRESET error crashing NodeJS application

Question

I am kind of new to coding and I needed some help with one error that I'm getting.

I'm running a NodeJS application (a Discord.js bot), my bot has the function to register a user's ID to a MySQL database when the user types a certain command. Sometimes it works just fine, but other times it crashes with an ECONNRESET error:

events.js:292
      throw er; // Unhandled 'error' event
      ^

Error: read ECONNRESET
    at TCP.onStreamRead (internal/stream_base_commons.js:205:27)
Emitted 'error' event on Connection instance at:
    at Connection._handleProtocolError (C:\Users\Celeron\Desktop\DiscordBot\node_modules\mysql\lib\Connection.js:423:8)
    at Protocol.emit (events.js:315:20)
    at Protocol._delegateError (C:\Users\Celeron\Desktop\DiscordBot\node_modules\mysql\lib\protocol\Protocol.js:398:10)
    at Protocol.handleNetworkError (C:\Users\Celeron\Desktop\DiscordBot\node_modules\mysql\lib\protocol\Protocol.js:371:10)
    at Connection._handleNetworkError (C:\Users\Celeron\Desktop\DiscordBot\node_modules\mysql\lib\Connection.js:418:18)
    at Socket.emit (events.js:315:20)
    at emitErrorNT (internal/streams/destroy.js:92:8)
    at emitErrorAndCloseNT (internal/streams/destroy.js:60:3)
    at processTicksAndRejections (internal/process/task_queues.js:84:21) {
  errno: 'ECONNRESET',
  code: 'ECONNRESET',
  syscall: 'read',
  fatal: true
}

Answer 1

First of all, you should catch the error, so you app can handle it properly and doesn't crash when mysql connection is closed for any odd reason. Try either with connection.on('error', ...) or with try-catch blocks.

For keeping an open connection, you should either reconnect on close. Or simply use mysql's pooling connection, which handles automatic reconnection very well, with a single code change.

PS: Pooling multiple connections is a generally good idea for async apps, like servers, but it's safe to maintain a single connection via pooling (connectionLimit : 1) just for automatic reconnection itself.

PPS: Mysql's inactivity timeout can be configured in server's my.cnf

Answer 2

I fixed the problem. The crash happened because of the application inactivity on the database, and when the con. becomes inactive for a couple seconds the mysql server closes de connection making the bot to crash when the code requires some database resource.

The solution was to create a function to keep constant activity in the DB connection.

Here is the code:

    con.query('SELECT 1', (err) => {
        if (err) throw err

        console.log('Tum tum')  \\ Heartbeat noises to know if it worked xD
    })
}
setInterval(keepAlive, 15000)```