[FIXED] How do I debug error ECONNRESET in Node.js?

Issue

I'm running an Express.js application using Socket.io for a chat webapp and I get the following error randomly around 5 times during 24h. The node process is wrapped in forever and it restarts itself immediately.

The problem is that restarting Express kicks my users out of their rooms and nobody wants that.

The web server is proxied by HAProxy. There are no socket stability issues, just using websockets and flashsockets transports. I cannot reproduce this on purpose.

This is the error with Node v0.10.11:

    events.js:72
            throw er; // Unhandled 'error' event
                  ^
    Error: read ECONNRESET     //alternatively it s a 'write'
        at errnoException (net.js:900:11)
        at TCP.onread (net.js:555:19)
    error: Forever detected script exited with code: 8
    error: Forever restarting script for 2 time

EDIT (2013-07-22)

Added both socket.io client error handler and the uncaught exception handler. Seems that this one catches the error:

    process.on('uncaughtException', function (err) {
      console.error(err.stack);
      console.log("Node NOT Exiting...");
    });

So I suspect it's not a Socket.io issue but an HTTP request to another server that I do or a MySQL/Redis connection. The problem is that the error stack doesn't help me identify my code issue. Here is the log output:

    Error: read ECONNRESET
        at errnoException (net.js:900:11)
        at TCP.onread (net.js:555:19)

How do I know what causes this? How do I get more out of the error?

Ok, not very verbose but here's the stacktrace with Longjohn:

    Exception caught: Error ECONNRESET
    { [Error: read ECONNRESET]
      code: 'ECONNRESET',
      errno: 'ECONNRESET',
      syscall: 'read',
      __cached_trace__:
       [ { receiver: [Object],
           fun: [Function: errnoException],
           pos: 22930 },
         { receiver: [Object], fun: [Function: onread], pos: 14545 },
         {},
         { receiver: [Object],
           fun: [Function: fireErrorCallbacks],
           pos: 11672 },
         { receiver: [Object], fun: [Function], pos: 12329 },
         { receiver: [Object], fun: [Function: onread], pos: 14536 } ],
      __previous__:
       { [Error]
         id: 1061835,
         location: 'fireErrorCallbacks (net.js:439)',
         __location__: 'process.nextTick',
         __previous__: null,
         __trace_count__: 1,
         __cached_trace__: [ [Object], [Object], [Object] ] } }

Here I serve the flash socket policy file:

    net = require("net")
    net.createServer( (socket) =>
      socket.write("<?xml version=\"1.0\"?>\n")
      socket.write("<!DOCTYPE cross-domain-policy SYSTEM \"http://www.macromedia.com/xml/dtds/cross-domain-policy.dtd\">\n")
      socket.write("<cross-domain-policy>\n")
      socket.write("<allow-access-from domain=\"*\" to-ports=\"*\"/>\n")
      socket.write("</cross-domain-policy>\n")
      socket.end()
    ).listen(843)

Can this be the cause?

Solution

A simple tcp server I had for serving the flash policy file was causing this. I can now catch the error using a handler:

# serving the flash policy file
net = require("net")

net.createServer((socket) =>
  //just added
  socket.on("error", (err) =>
    console.log("Caught flash policy server socket error: ")
    console.log(err.stack)
  )

  socket.write("<?xml version=\"1.0\"?>\n")
  socket.write("<!DOCTYPE cross-domain-policy SYSTEM \"http://www.macromedia.com/xml/dtds/cross-domain-policy.dtd\">\n")
  socket.write("<cross-domain-policy>\n")
  socket.write("<allow-access-from domain=\"*\" to-ports=\"*\"/>\n")
  socket.write("</cross-domain-policy>\n")
  socket.end()
).listen(843)

Answered By - Samson

Answer Checked By - Mary Flores (PHPFixing Volunteer)