[dancer-users] Get backtrace for stuck Dancer process

[John McDermott, CPLP]

Can you modify the code in the program or at least add a statement to 
the invocation? If so, here are some hints from an older perlmonks post: 
https://www.perlmonks.org/?node_id=640319 Maybe you could catch a signal 
and invoke one of the methods described in the post.

There is Devel::STrace if you can handle the volume of information.

Since it doesn't die, I'm not sure Carp::Always would be of much help 
except in a signal handler you set up.

Does that help any?

-john


On 9/28/2018 12:39 PM, Warren Young wrote:
> On Sep 28, 2018, at 1:13 AM, Stefan Hornburg (Racke) <racke at linuxia.de> wrote:
>> At any rate, you can strace the Dancer process(es) and see what system calls it does.
> I’m quite familiar with strace, but I rejected that out of hand at the time, since most Perl code is running way above the OS’s syscall interface.
>
> There are only a couple of cases I can think of where what it says might help.  E.g. stuck on accept(2).
>
> No, I really do want to be able to produce a Perl-level stack trace, on demand, without killing the program, as via Carp::confess().
>
> It looks like “perl -d” can’t attach to a running program, either, which would let me use some of these fine Perl modules to produce a backtrace.
>
> I found a partial solution, though:
>
>      https://metacpan.org/pod/App%3a%3aStacktrace
>
> Unfortunately for me, it requires Perl 5.10, and this problem happened on a box that’s still running 5.8.  (Don’t ask, can’t avoid that.)
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John J. McDermott, CPLP
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