Type error on error closing connection

[grimkirill]

• I've searched for any related issues and avoided creating a duplicate
  issue.

Description

Type error:

node_modules/ws/lib/websocket.js:900
websocket.readyState = WebSocket.CLOSING;
^

TypeError: Cannot set property 'readyState' of undefined

Reproducible in:

• version: ^7.0.0
• Node.js version(s): 8
• OS version(s): ubuntu 18

Steps to reproduce:

1. Connect

2. Disconnect by broken connection

Expected result:

Actual result:

Attachments:

[lpinca]

Are you able to create a reproducible test case? This can only happen if the 'error' event is emitted after the 'close' event on the net.Socket but it would be a bug in Node.js.

[grimkirill]

It was easy reproduced on production load.
v6.1.4 has additional check, that allow pass this error

if (websocket) {
    websocket.readyState = WebSocket.CLOSING;
    this.destroy();
  }

[lpinca]

Yes, it was originally needed due to this issue: #1226.

We fixed it in #1464 and #1471, and removed the check in 297f56d.

We can add it back but it would be nice to know how this can happen so we can also add a regression test.

[grimkirill]

It was happening at the high load. nodejs use near of 90% cpu usage, socket with tls and part of connections was broken by network issues.
Maybe some of combination of: termination + timeout + error

[grimkirill]

i think that found problem: missed remove error handler, that produced race

function socketOnClose() {
  ...
  this.removeListener('data', socketOnData);
  this.removeListener('error', socketOnError); // missed
  this[kWebSocket] = undefined;

[lpinca]

No, if we do that and an 'error' event emitted after the 'close' event, it will crash the process.

[grimkirill]

Yep you are right.
So only one way is the return of websocket check undefined, because error event can be fire after socketOnClose execution

[lpinca]

Yes I will revert 297f56d.

[lpinca]

@grimkirill if you can reproduce this, can you try with Node.js 10+? I would like to see if the issue is limited to Node.js 8.

Thank you.

[lpinca]

@grimkirill any update?

[chuahcheeshian]

@lpinca I'm using Node.js 12, also having this issue as well.

[lpinca]

@chuahcheeshian same stack trace? Can you post it? Thank you.

[chuahcheeshian]

@lpinca

On my staging servers with little to no load, this error never happened at all.
On my production servers, this error only happened randomly under high load.
With 2k concurrent WebSocket connections, this error happened at least 8 times/hour.

And when it happened, the server crashed and got restarted by Docker intentionally.
And then all the previously connected clients reconnected at once.
Maybe under high load, this error might stand a better chance to be triggered?
Or should there be any bug in my code that led to this error?

I had then downgraded ws to 6.2.0 in which the if (websocket) clause is present.
My production servers have never been restarted since then.

For more information, the version of Node.js I'm using is 12.6.0, the version of ws is 7.0.1.

[lpinca]

Ok I've reverted 297f56d. Will cut a new release soon.