スクリプトを修正することなく外部から稼働中のperlプロセスの状態を観測する方法について、既存の手法をおさらいした上で、導入コストが小さい手法でパッケージ毎のメモリ使用状況や%INCのダンプをする方法を提案します。

1. How to inspect
RUNNING perl process
@hirose31
ひろせ まさあき
YAPC::Asia Tokyo 2013
LT Day 1

2. Who am I
•PAUSE ID: HIROSE / @hirose31
•Recognize as NON-human on CPAN
テキスト
https://metacpan.org/module/Acme::CPANAuthors::Nonhuman

3. Agenda
How to inspect a RUNNING perl process
•Motivation
•Revisit existing ideas
•Introduce a my idea

4. Motivation
•WHY: shooting trouble of RUNNING perl
process
•examine where perl process is running
•where does process hang up?
•where does process loop forever?
•which pacage leaks memory?
•want to examine from OUTER without
editing target process/script

5. Revisit existing ideas
‘strace’
• strace -fF -Tttt -s 512 -p PID
• current system call
• show the time spent in system calls
• peep into an ASCII string
• no requires☺, just attach process
• show just name of system call not perl symbol☹
1379392067.757575 accept(5,
1379392038.406593 write(5, "220003 select
sleep(8) ", 22) = 22 <0.000083>
1379392038.406791 read(5,

6. Revisit existing ideas
‘gdb’
• Attach and trace code by gdb
• Generate a core file by gcore PID
• “Introduction gdb to perl programmers”, @stanaka,
Shibuya.pm #9
http://blog.stanaka.org/entry/20080630/1214780557
• show stacktrace with perl symbol
#0 0x00007fb086990c20 in __accept_nocancel () from /lib/
libpthread.so.0
#1 0x00000000004f19e8 in Perl_pp_accept (my_perl=0xd69010) at
pp_sys.c:2554
...
#5 0x0000000000420eef in main (argc=8, argv=0x7fff34899828,
env=0x7fff34899870) at perlmain.c:99

7. Revisit existing ideas
‘bulkdbg’
•https://github.com/ahiguti/bulkdbg
•bulkdbg PID
•show stackstrace with perl symbol
•convinient by batch
3183
__accept_nocancel:Perl_pp_accept:Perl_pop_scope:Perl_peep:_dl_r
tld_di_serinfo:PerlIO_debug:_dl_rtld_di_serinfo:PerlIO_debug:ca
lloc:calloc:__libc_malloc:calloc:_dl_rtld_di_serinfo:S_hv_fetch
_common

8. Revisit existing ideas
‘gdbperl’
• https://github.com/ahiguti/gdbperl
• examine state of perl interpreter using gdb
• “debugging Perl script with gdb”, Akira Higuchi, YAPC::Asia Tokyo
2011
http://www.slideshare.net/akirahiguchi/gdbperl
• show stacktrace with perl code☺, package name, line number!!
• depend heavily on perl version/internal structure☹
perl_backtrace:
[8] IO::Socket::accept() <- /.../perl-5.8.8-threads/lib/
site_perl/5.8.8/Starlet/Server.pm:106(Starlet::Server)
[7] (loop) <- /.../perl-5.8.8-threads/lib/site_perl/5.8.8/
Starlet/Server.pm:105(Starlet::Server)
...
[1] Plack::Runner::run() <- /.../perl-5.8.8-threads/bin/
plackup:10(main)

9. Introduce a my idea
‘inspect-perl-proc’
• https://github.com/hirose31/inspect-perl-proc
• Attach by gdb and run arbitrary Perl code
using Perl_eval_pv
• less requires: gdb, perl with debug symbol (-
DDEBUGGING=-g)
• not depend on perl version / perl internal
structure
• save output to file, not output STDOUT/
STDERR of target process

10. dump-perl-stacktrace
• dump-perl-stacktrace
= inspect-perl-proc --mode 'dump-stacktrace'
• Carp::longmess(‘Dump stacktrace’)
Dump stacktrace at /.../perl-5.8.8-threads/lib/5.8.8/x86_64-
linux-thread-multi/IO/Socket.pm line 237
IO::Socket::accept('IO::Socket::INET=GLOB()')
called at /.../Starlet/Server.pm line 106
Starlet::Server::accept_loop('Plack::Handler::
Starlet=HASH()', 'CODE()', 100) called
at /.../Starlet.pm line 67
Plack::Handler::Starlet::run('Plack::Handler::
Starlet=HASH()', 'CODE()') called
at /.../Plack/Loader.pm line 84
...
Plack::Runner::run('Plack::Runner=HASH()') called
at /.../bin/plackup line 10

11. dump-perl-memusage
• dump-perl-memusage
= inspect-perl-proc --mode 'dump-memusage'
• Dump memory usage with B::Size2::Terse::package_size
for each packages (Devel::Symdump)
• save as as hashref so you can filter or sort easily
{
'main' => '95589',
...
'PerlIO::scalar' => '1025',
'Plack' => '3056',
'Plack::App' => '200',
'Plack::App::URLMap' => '26681',
'Plack::Builder' => '31972',
...
};

12. dump-perl-inc
• dump-perl-inc
= inspect-perl-proc --mode 'dump-inc'
• Dump %INC
• list up loaded modules for preloading (CoW)
• save as as hashref so you can filter or sort easily
{
'parent.pm' => '/.../parent.pm',
'HTTP/Status.pm' => '/.../HTTP/Status.pm',
'POSIX.pm' => '/.../POSIX.pm',
'List/Util.pm' => '/.../List/Util.pm',
'Plack/Loader.pm' => '/.../Plack/Loader.pm',
'Cwd.pm' => '/.../Cwd.pm',
'Fcntl.pm' => '/.../Fcntl.pm',
...
};

13. Introduce a my idea
‘inspect-perl-proc’
• https://github.com/hirose31/inspect-perl-proc
• Attach by gdb and run arbitrary code using
Perl_eval_pv
• less requires: gdb, perl with debug symbol (-
DDEBUGGING=-g)
• not depend on perl version / perl internal
structure
• save output to file, not output STDOUT/
STDERR of target process

14. Thanks :D