Connection lost: The server closed the connection - vanilla

Hi Doug!
I have the following code:

var mysql = require('mysql');
var con = mysql.createConnection({
  host: "192.168.0.46",
  user: "SHARED",
  password: "Pjh",
  database: "SHARED"
});

con.connect(function(err) {
  if (err) return err;
  con.query("SELECT USERID FROM TBL_USER_LOCAL WHERE USERNAME = 'someuser'", function (err, result, fields) {
    if (err) return err;
    console.log(result);
  });
});

The connection gets closed if the server is offline - I am calling this from a different server than the db is running on. The node server crashes if the above is true. Any ideas how I can keep the node server running (this node server just listens for connections to several mysql servers) and if one is down, this code causes the crash of node.

I hope I have been clear? Thank you!

Just to be clear, this file is called from app.js dynamically and is otherwise standalone.

[dougwilson]

So I ran your Node.js code above connected to a MySQL server. After shutting down the MySQL server your script exits, but thr reason it exits is because the only thing in yiur code above that was preventing it frlm exiting was the open TCP connections. Onve that was closed, there is no longer anything keeping the event loop running.

I'm not sure why you would want to keep that code running after it completed, though, because it will never do anythinf after the query result is logged.

I hope this helps explain why your script above stops running when the MySQL server goes offline!

[dougwilson]

I sse you responded with additional information while I was running your code and responding. I can help with something else, but I only have the provided information to help with. It sounds like you have some more things going on in your code. I can help with more, but without knowing what the code is I'm not sure what would be happening.

[dougwilson]

If it helps as well, here is the documentation which explains error handing in this module: https://github.com/mysqljs/mysql/blob/master/Readme.md#error-handling

this code above gets called when and only when a server is down.

app.post('/cs',function(req,res){
	var status;
	if(req.session_state.user){
		var resArray = {};
		var hosts = req.body.server;
		var node;
		//~ node = require('./chk46.js');
		//~ console.log(node);
		hosts.forEach(function(item) {
			if(fs.existsSync('chk'+item[0].split('.')[3]+'.js')){

//'chk'+item[0].split('.')[3]+'.js'
//here the file in question gets called


				node = require('./chk'+item[0].split('.')[3]+'.js');
			}
			//~ console.log('chk'+item[0].split('.')[3]+'.js');
			console.log(node);
			var sock = new net.Socket();
			sock.setTimeout(2500);
			sock.on('connect', function() {
				resArray['status'+item[0]] = item[0]+':'+item[1]+' is up.';
				console.log(item[0]+':'+item[1]+' is up.');
				resArray[item[0]] = 'green';
				sock.destroy();
			}).on('error', function(e) {
				setTimeout(function(){
					resArray[item[0]] = 'red';
					resArray['status'+item[0]] = item[0]+':'+item[1]+' is down: ' + e.message;
					console.log(item[0]+':'+item[1]+' is down: ' + e.message);
				},1200);
			}).on('timeout', function(e) {
				setTimeout(function(){
					resArray[item[0]] = 'black';
					console.log(item[0]+':'+item[1]+' is down: timeout');
				},1200);
			}).connect(item[1], item[0]);
		});
	    setTimeout(function(){
			res.send(resArray);
		},2500);
	}
});

[dougwilson]

Hi @phpmydev thanks for that! There is a lot going on in the code, and just trying to run it has a lot of things undefined for me. Would it be possible to get the following information:

1. Version of Node.js
2. Version of this module
3. Complete code that I can copy and paste and run
4. Complete steps to reproduce your issue

Thanks! I'd love to help out, but I'm not sure what is happening without ideally being able to see. You're always welcome to debug through it and send over a pull request as well :) !

it looks like what I need to use is err.code? I'm not sure where to use it. before the call back or as the callback?

[dougwilson]

Hi @phpmydev there are a lot of callbacks between the code pasted so far. Which callback are you referring to?

oh! maybe I'm posting my err code in the wrong place?! should it be in app.js there somewhere? and not in chk46.js? Thank you, btw, for your answers!

[dougwilson]

Is chk46.js the file with the app.post in it or the one with MySQL code (sorry, trying to follow along). In the one with the MySQL call, your return statements just go nowhere, since nothing is using the return value from those functions. That wouldn't be an issue directly, though. Maybe if that is the complete file, you should probably be calling con.end() in there to close down the connection, since you're not going to be using it again.

chk46 is the file I first posted with
I am used to using a pool instead of a single connection
app.js holds the second, complicated code
What I meant in the last post is maybe I should be handling the error in app.js and not chk46?

I can't really post the whole shebang, but I appreciate your responsiveness!