Receiving unexpected tsserver messages in server logs

[benjreinhart]

I have noticed a lot of tsserver messages in the logs recently that indicate we are still connected to a tsserver instance after we should have shut it down. I'm not exactly sure why this is happening but I didn't use to see these.

Received a response for command 'open' and request_seq '0' but no resolver was found. This may be a bug in the code.

Response:
{
  "seq": 0,
  "type": "response",
  "command": "open",
  "request_seq": 0,
  "success": true,
  "performanceData": {
    "updateGraphDurationMs": 379.10445799999997
  }
}

Received a response for command 'open' and request_seq '1' but no resolver was found. This may be a bug in the code.

Response:
{
  "seq": 0,
  "type": "response",
  "command": "open",
  "request_seq": 1,
  "success": true
}

Received a response for command 'open' and request_seq '2' but no resolver was found. This may be a bug in the code.

Response:
{
  "seq": 0,
  "type": "response",
  "command": "open",
  "request_seq": 2,
  "success": true
}

[Sanjoy-droid]

hey @benjreinhart can you please elaborate how to reproduce this issue?

[benjreinhart]

@Sanjoy-droid I'm not sure the exact cause, but it happens very regularly for me. If you navigate between a srcbook, the home page, another srcbook, add/delete them, etc, I would expect you to come across this unless there's something unique going on in my environment.

[BeRecursive22]

@benjreinhart it's not your environment. I was able to reproduce it and the cult is "React's StrictMode". Once you disable it, the ts server will stop normally and you won't see those logs.

I am still not confident why it's happening. Maybe double invoking messes up with the lifecycle and hence the cleanup effect not running properly.

Anyways even with StrictMode enabled, we can just stop the ts server in a separate useEffect.

@Sanjoy-droid let me know if this worked.

[BeRecursive22]

@benjreinhart or you can assign the issue to me for a deeper look.

[BeRecursive22]

@benjreinhart @nichochar
NOTE: Potential Resource Leak

• There was a risk of CPU/Memory leak if a user opened a Srcbook,
• navigated to other routes, and remained there indefinitely.
• The tsserver processes would continue running in the background,
• potentially consuming system resources unnecessarily.

I haven't dive deeper into the backend code but I hope we have a server-side timeout mechanism to stop inactive tsserver processes.