Feature Request: Event loop introspection

[fresheneesz]

Every once in a while I have a hanging process, and I have no idea why it hangs. It could take me hours to figure it out. It would be great if there were ways to ask the program things like:

• How many open file descriptors are there? What kinds of things are they: (type [network, file system file, input descriptor], name ["http connection to <some IP address>"], etc)?
• How many waiting timers are there? What callback(s) are associated with them (so you could print out the text of the functions)?

This would go a very long way in making hanging scripts easier to debug.

[Qard]

👍 I'd like to see this myself, at some point.

There's already process._getActiveHandles() and process._getActiveRequests() for that sort of thing. They're not currently part of the public API though, so they could change at any time. The necessary components to start on this are there though.

The timers one is a little harder, due to the weird batch processing of them. Still probably doable though.

[fresheneesz]

Ah, those functions might come in useful at some point. Thanks!

[Fishrock123]

There was definitely a previous issues about this, but I can't seem to find it... @Qard's answer is correct though.

[fresheneesz]

@Fishrock123 Was it this: nodejs/node-v0.x-archive#1025 ?

[Fishrock123]

@fresheneesz nope, there was one on this issue tracker.

[Qard]

You're thinking of #1128.

[thlorenz]

active-handles handles (npi) part of these features and walks timers as well.

[Fishrock123]

Ah yes. Closing in favor of #1128, please make any additional comments there! :)