Package: libapache2-mod-php4
Version: 4:4.3.10-8
Severity: important
Sudenly, and unfortunately quite frequently these days, our web server
(http://www.cidades.gov.br/) simply stops responding to requests. It
accepts the connection and then does not respond.
We've tracked the problem down to session file locking. This is the
research we've made:
# strace -p 8527
Process 8527 attached - interrupt to quit
flock(20, LOCK_EX <unfinished ...>
Process 8527 detached
I ran an strace on an apache2 process while everything was working
to understand what it was trying to flock(), before the research
which involved the process above start and found out it was the php4
session file:
# grep -B 1 flock /var/log/strace-do-apache.log
open("/var/lib/php4/sess_9afb343331c4e160529bb01a007ed702",
O_RDWR|O_CREAT, 0600) = 20
flock(20, LOCK_EX)
[several repeats of that with different session ids]
Then I tried to find out who had the file opened, in order to maybe
figure out who was holding the lock without releasing it:
# lsof | grep var/lib/php4
apache2 7231 www-data 20uW REG 8,9 67
114761 /var/lib/php4/sess_79a7c4312a40cb016b663c2107388394
apache2 7481 www-data 20u REG 8,9 636
160680 /var/lib/php4/sess_c8a8e2ac3bc4d109f5a98f497f20cd3c
apache2 7560 www-data 20u REG 8,9 636
160680 /var/lib/php4/sess_c8a8e2ac3bc4d109f5a98f497f20cd3c
apache2 7592 www-data 20u REG 8,9 67
114761 /var/lib/php4/sess_79a7c4312a40cb016b663c2107388394
apache2 7593 www-data 20u REG 8,9 636
160680 /var/lib/php4/sess_c8a8e2ac3bc4d109f5a98f497f20cd3c
apache2 7594 www-data 20u REG 8,9 636
160680 /var/lib/php4/sess_c8a8e2ac3bc4d109f5a98f497f20cd3c
[...]
apache2 8464 www-data 20u REG 8,9 636
160680 /var/lib/php4/sess_c8a8e2ac3bc4d109f5a98f497f20cd3c
apache2 8465 www-data 20u REG 8,9 636
160680 /var/lib/php4/sess_c8a8e2ac3bc4d109f5a98f497f20cd3c
apache2 8468 www-data 20u REG 8,9 636
160680 /var/lib/php4/sess_c8a8e2ac3bc4d109f5a98f497f20cd3c
apache2 8469 www-data 20u REG 8,9 636
160680 /var/lib/php4/sess_c8a8e2ac3bc4d109f5a98f497f20cd3c
apache2 8470 www-data 20u REG 8,9 636
160680 /var/lib/php4/sess_c8a8e2ac3bc4d109f5a98f497f20cd3c
apache2 8471 www-data 20u REG 8,9 636
160680 /var/lib/php4/sess_c8a8e2ac3bc4d109f5a98f497f20cd3c
apache2 8473 www-data 20uW REG 8,9 0
356396 /var/lib/php4/sess_e815444a415e1b977660141441b58a7b
apache2 8504 www-data 20u REG 8,9 636
160680 /var/lib/php4/sess_c8a8e2ac3bc4d109f5a98f497f20cd3c
[...]
apache2 8528 www-data 20u REG 8,9 636
160680 /var/lib/php4/sess_c8a8e2ac3bc4d109f5a98f497f20cd3c
apache2 8560 www-data 20uW REG 8,9 67
102433 /var/lib/php4/sess_0d152bfbaedf7f0d4843af5746e95bed
apache2 8565 www-data 20u REG 8,9 636
160680 /var/lib/php4/sess_c8a8e2ac3bc4d109f5a98f497f20cd3c
apache2 8598 www-data 20u REG 8,9 636
160680 /var/lib/php4/sess_c8a8e2ac3bc4d109f5a98f497f20cd3c
apache2 8601 www-data 20uW REG 8,9 636
160680 /var/lib/php4/sess_c8a8e2ac3bc4d109f5a98f497f20cd3c
apache2 8607 www-data 20u REG 8,9 636
160680 /var/lib/php4/sess_c8a8e2ac3bc4d109f5a98f497f20cd3c
apache2 8610 www-data 20u REG 8,9 636
160680 /var/lib/php4/sess_c8a8e2ac3bc4d109f5a98f497f20cd3c
apache2 8611 www-data 20u REG 8,9 636
160680 /var/lib/php4/sess_c8a8e2ac3bc4d109f5a98f497f20cd3c
# strace -p 7481
Process 7481 attached - interrupt to quit
flock(20, LOCK_EX <unfinished ...>
Process 7481 detached
I just did not figure out who was the one really holding the
lock. Searchs on google didn't seem to produce useful results.
Thanks,
-- System Information:
Debian Release: 3.1
APT prefers testing
APT policy: (990, 'testing'), (500, 'unstable')
Architecture: i386 (i686)
Kernel: Linux 2.6.1001052005
Locale: LANG=C, LC_CTYPE=C (charmap=ANSI_X3.4-1968)
Versions of packages libapache2-mod-php4 depends on:
ii apache2-mpm-prefork [apach 2.0.53-5 traditional model for Apache2
ii libbz2-1.0 1.0.2-5 high-quality block-sorting file co
ii libc6 2.3.2.ds1-20 GNU C Library: Shared libraries an
ii libcomerr2 1.36release-1 common error description library
ii libdb4.2 4.2.52-18 Berkeley v4.2 Database Libraries [
ii libexpat1 1.95.8-1 XML parsing C library - runtime li
ii libkrb53 1.3.6-1 MIT Kerberos runtime libraries
ii libmagic1 4.12-1 File type determination library us
ii libpcre3 5.0-1 Perl 5 Compatible Regular Expressi
ii libssl0.9.7 0.9.7e-3 SSL shared libraries
ii libzzip-0-12 0.12.83-4 library providing read access on Z
ii mime-support 3.31-1 MIME files 'mime.types' & 'mailcap
ii php4-common 4:4.3.10-8 Common files for packages built fr
ii zlib1g 1:1.2.2-4 compression library - runtime
-- no debconf information
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