Error: EMFILE, Too many open files

[CrabDude]

Connections often became stale and so as a result I was recreating / restarting connections before timeout to ensure freshness, over time the following error occurred:

20 Nov 20:15:01 - Error: EMFILE, Too many open files
at net:907:19
at Object.lookup (dns:138:5)
at Stream.connect (net:902:9)
at connect (/usr/local/lib/node/.npm/mysql/0.8.0/package/lib/mysql/client.js:79:16)
at Client._prequeue (/usr/local/lib/node/.npm/mysql/0.8.0/package/lib/mysql/client.js:245:3)
at Stream. (/usr/local/lib/node/.npm/mysql/0.8.0/package/lib/mysql/client.js:77:14)
at Stream.emit (events:27:15)
at IOWatcher.callback (net:471:53)
at node.js:772:9

Here is the code that was resetting the connection:

var sphinx = new Client(),
    client = new Client(),
    mysqlReset = 300000;

sphinx.user = 'XXXXX';
sphinx.port = '9306';
sphinx.host = '127.0.0.1';
sphinx.connect();

client.user = 'xxxxxxx';
client.password = 'XXXXXX;
client.database = 'XXXXXX';
client.host = '127.0.0.1';
client.connect();

setInterval(function() {
    resetMysql(client,function(newClient) {
        client = newClient;
    });
    resetMysql(sphinx,function(newClient) {
        sphinx = newClient;
    });
}, mysqlReset);

function resetMysql(old, cb) {
    var temp = new Client();
    for (var i in old) {
        if (old.hasOwnProperty(i) && typeof old[i] != 'undefined' && old[i] !== null && old[i].constructor != Function) {
            temp[i] = old[i];   
        }
    };
    temp.connect(function() {
        cb(temp);
        old.end();
    });
}

[Sannis]

I fix similar error with replacing conn.end() by conn.destroy(), but I think this isn't good way. Also I try to use reverse callback order, but it doesn't matter.
old.end(function () {
temp.connect(function (err) {
cb(temp);
});
});

I specially disable DNS lookups in MySQL server to increase performance and switch to IP when connect to DB with node-mysql (for benchmarking node MySQL bindings). So it is interesting for me, is it a bug in node-mysql or in Node itself.

[CrabDude]

I know it used to be a bug in Node itself, but it appears to have been resolved, though maybe this is proving to be an edge case.

[felixge]

CrabDude: Are you sure that your mysql connections are going stale? If that's the case then it is a bug. I've explicitly added support for automatic re-connection in these scenarios.

[CrabDude]

@felixge: I never verified, and unfortunately I am no longer on the project. It was something that would come up eventually every time which I resolved by merely letting the process die and be restarted by multi-node. Hopefully it was just something on my end. ;)

[felixge]

Alright, I'll close this for now until I have a way to reproduce the problem.