Net::SSH::Perl kills perl from within an eval

jahrens has asked for the wisdom of the Perl Monks concerning the following question:

I didn't think this was possible.

So I'm using Net::SSH::Perl. Randomly it seems a connection that is in use will manage to kill perl while within an eval.

The code is very simple. $ssh is a Net::Perl::SSH object that is connected and authenticated.

eval {($out, $err, $status) = $ssh->cmd("ls -l")};

It manages to kill perl. Like, total exit, no errors printed. I'm hoping someone might have some idea about what's going on, or how I might track it down. It's seems random, which makes it even worse. The exact same sequence of commands can work one time, but not another.

If nothing else, how about an explanation about how it's managing to die within an 'eval' without getting back to the main program?

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Re: Net::SSH::Perl kills perl from within an eval (exit) by tye (Sage) on Oct 28, 2008 at 01:05 UTC
If nothing else, how about an explanation about how it's managing to die within an 'eval' without getting back to the main program? exit is the easiest way. exec also works. There are also less pedestrian ways including bugs in perl, POSIX::_exit(), XS code, ... (update) I tested and the following is another way: $ perl -e'eval { alarm(1); sleep(3); }; print "Done\n"' Alarm clock $ [download] In other words, the module (Net::SSH::Perl) could set a handler for a time-out but then remove the handler before canceling the time-out. But I don't see where the module calls exit(), exec(), or even alarm(). - tye	[reply] [d/l]
719885 by jahrens (Acolyte) on Oct 28, 2008 at 01:51 UTC
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Re: Net::SSH::Perl kills perl from within an eval by salva (Canon) on Oct 28, 2008 at 08:19 UTC
Instead of Net::SSH::Perl that's an almost dead project, if you can, use Net::SSH2. It is based on the libssh2 library that is actively developed and bugs are solved quickly.	[reply]
Re: Net::SSH::Perl kills perl from within an eval by almut (Canon) on Oct 28, 2008 at 01:35 UTC
Maybe running your program under `strace` (or equivalent) would help to shed some light on what's going on... (from the system call perspective, that is). This would easily detect stuff like trying to write to a broken socket/pipe, etc.	[reply] [d/l]
Re: Net::SSH::Perl kills perl from within an eval by Krambambuli (Curate) on Oct 28, 2008 at 07:27 UTC
Maybe you can turn on some extra params to the connection to see more of what's going on, like `my $ssh = Net::SSH::Perl->new( "host", debug => 1, options => [ "ConnectTimeout 30", "LogLevel Debug3", "ServerAliveInterval +10", "ServerAliveCountMax +5", ], );` [download] With a bit of luck, you might get ssh behaving in a way that would not make Perl show the unwanted behavior even with a flaky connection or over a link that faces packet loss. Hth, Krambambuli ---	[reply] [d/l]
Re: Net::SSH::Perl kills perl from within an eval by jahrens (Acolyte) on Oct 28, 2008 at 01:54 UTC
I found http://www.perlmonks.org/?node_id=580411 after deeper digging. It sounds possible. I also got 141 for $? after the silent exit. I'll have to throw in a suite of signal handlers to call out when they get called to see if it explains anything.	[reply]
Re^2: Net::SSH::Perl kills perl from within an eval by ikegami (Patriarch) on Oct 28, 2008 at 02:21 UTC
That means it died from signal 13 (141 & 127). See `man kill` for a list. On my linux system, that's SIGPIPE, a very likely signal in the situation you presented.	[reply] [d/l]