Impossible to debug multi-threaded processes on headless server.

[conartist6]

See closed issue #9435
and
#5025

While it is possible now to run node --inspect-brk=0, this only waits for a GUI to connect to the debugger. In my case a restrictive network configuration means that I can't actually connect a GUI debugger to a completely random port.

Thus my circumstances dictate that I need to use the CLI debugger with a random port. I would assume that the command to run would be

Expected: node inspect --inspect-port 0 launches the CLI debugger in the main thread, and the background thread does not crash with port 9229 in use errors.

Actual:

scripts/ads/interfaces/ice_routing/generate
< Debugger listening on ws://127.0.0.1:39163/7bc855ba-cd5e-4ad0-9c17-e3b04d94aae3
< For help see https://nodejs.org/en/docs/inspector
connecting to 127.0.0.1:9229 ............ failed to connect, please retry

In other news I'd love to know where we could track progress towards being able to debug multiple child processes over a single port.

[bnoordhuis]

Can you fill out the issue template? We ask it for a reason.

In other news I'd love to know where we could track progress towards being able to debug multiple child processes over a single port.

Follow inspector development in upstream Chromium. We're a downstream consumer.

[conartist6]

v8.7.0,
Darwin cbuck-mbp 16.7.0 Darwin Kernel Version 16.7.0: Thu Jun 15 17:36:27 PDT 2017; root:xnu-3789.70.16~2/RELEASE_X86_64 x86_64

[bnoordhuis]

Thanks. That MacBook probably isn't the machine you're having trouble with though, is it?

Can you post the exact steps you use to start node.js + connect to it? The snippet you posted seems to be a script executing. It hides the actual invocations.

[conartist6]

No, though I verified that I can cause the problem on my mac. It's not platform-specific. I forgot I posted the script. The actual invokation inside the script is the one I posted: `node inspect --inspect-port 0 ./script.js

Bizarrely just twice, in circumstances I don't really understand node inspect ./script did exactly what I wanted, which is not die of port in use errors and give me a debugger right there.

I also just figured out that it is possible to debug it. Node inspect can be used as a client when given a host and port combination, which works when I background the result of --inspect-brk=0.

Perhaps the easiest fix would be simply updating the documentation, but it would be nice if there was a way to run inspect and get the debugger on that process, without port conflicts, as I've suggested here.

[bnoordhuis]

node inspect --inspect-port 0 ./script.js

Couple of things:

1. It's --inspect-port=0, note the = sign. --inspect-port 0 are two arguments and probably prints a warning or error.

2. Write node --inspect-port=0 inspect ./script.js - the argument should go before inspect. Maybe you were thinking of node inspect --port=<port> ./script.js.

I opened nodejs/node-inspect#51 to make binding to port zero work more smoothly.

[conartist6]

You're right of course about =, that was a typo here.

I just tried putting the argument before inspect. You're quite correct that it does do something different than putting the argument after:

< Debugger listening on ws://127.0.0.1:44035/2b529c08-fc5d-467b-942f-1cd8e19c6a57
< For help see https://nodejs.org/en/docs/inspector
connecting to 127.0.0.1:0 ............ failed to connect, please retry

vs

< Debugger listening on ws://127.0.0.1:44081/fa5a4ce3-61e8-405b-a3ea-47c57a3f8fc9
< For help see https://nodejs.org/en/docs/inspector
connecting to 127.0.0.1:9229 ............ failed to connect, please retry

[conartist6]

Ah, but I see your diff fixes that, awesome!