node debug -p fails

[julien51]

Hello,

We have a stuck node.js process. We suspect it may be due to some kind of infinite loop somwhere. Since we have no idea where to look it up, we tried using node debug -p . No luck:

# node debug -p 13974
connecting.............There was an internal error in Node's debugger. Please report this bug.
connect ECONNREFUSED
Error: connect ECONNREFUSED
    at errnoException (net.js:901:11)
    at Object.afterConnect [as oncomplete] (net.js:892:19)

The output makes me think that the node debug process can't connect to our process precisely because our event loop is stuck. Could that be the case?
In another thread, @davepacheco indicates that this should not be a problem:

That's not a problem. We modified Node back in the 0.4 days to support opening the debugger port even if the Node program itself is stuck in an infinite loop, and V8 is able to evaluate expressions in this context.

Can someone clarify things? Why are we unable to connect to our "stuck" node.js process? Any idea on how to debug that? (we're on debian... so all tools requiring us to use Solaris won't do :()

[bnoordhuis]

Did you start process 13974 in debug mode? If not, what happens when you send it a SIGUSR1 to activate the debugger?

[trevnorris]

What version of Node are you using? Can you explain the general purpose of what the process is supposed to be working on? What's the CPU usage on that PID?

[faridnsh]

Just a simple infinite loop is enough to replicate this:

while (true) {}

[jasnell]

@trevnorris @bnoordhuis ... any reason to keep this one open?

[bnoordhuis]

I'm fairly sure this is fixed in io.js. Don't know about joyent/node.

[jasnell]

An initial quick test on v0.12 doesn't show any connection error but things are still less than useful. It's worth investigating further.