On my Ubuntu 10.04.4 server, apache2 2.2.14 eats up all the memory until there is no more left because it isn't shutting down old instances.
The server serves a small webpage which gets about one request each 3 seconds or so (from clients, google bot, scripts, etc).
If I look into the process list, there are a lot of apache2 instances:
ps aux | grep apache2
www-data 1324 0.0 6.4 580688 135600 ? Sl 07:44 0:00 /usr/sbin/apache2 -k start
www-data 1407 0.0 6.2 518800 131748 ? Sl 07:49 0:00 /usr/sbin/apache2 -k start
www-data 1464 0.0 6.0 518800 127740 ? S 07:52 0:00 /usr/sbin/apache2 -k start
www-data 1492 0.0 6.1 580688 129852 ? S 07:56 0:00 /usr/sbin/apache2 -k start
www-data 2043 0.0 6.2 501384 130864 ? Sl 08:46 0:00 /usr/sbin/apache2 -k start
www-data 3207 0.0 6.1 501384 128260 ? S 08:57 0:00 /usr/sbin/apache2 -k start
www-data 5711 0.0 6.2 509580 130888 ? Sl 10:48 0:00 /usr/sbin/apache2 -k start
www-data 5779 0.0 6.0 509580 126120 ? S 10:52 0:00 /usr/sbin/apache2 -k start
www-data 5796 0.0 6.1 491140 128660 ? Sl 10:54 0:00 /usr/sbin/apache2 -k start
www-data 5878 0.0 6.2 510604 130144 ? Sl 10:59 0:00 /usr/sbin/apache2 -k start
www-data 7854 0.0 6.1 492556 129712 ? Sl 11:55 0:00 /usr/sbin/apache2 -k start
www-data 7925 0.0 5.9 492556 125592 ? S 12:00 0:00 /usr/sbin/apache2 -k start
www-data 8018 0.0 6.3 519204 132132 ? Sl 12:07 0:00 /usr/sbin/apache2 -k start
www-data 8019 0.0 6.5 512448 136388 ? Sl 12:07 0:00 /usr/sbin/apache2 -k start
www-data 8020 0.0 5.8 484340 122532 ? S 12:07 0:00 /usr/sbin/apache2 -k start
root 8159 0.0 0.0 7644 908 ttyp0 R+ 12:16 0:00 grep --color=auto apache2
root 23949 0.0 6.3 483316 132176 ? Ss 00:16 0:15 /usr/sbin/apache2 -k start
root 23951 0.0 0.0 16956 512 ? Ss 00:16 0:00 /usr/sbin/htcacheclean -n -d120 -i -p/var/cache/apache2/mod_disk_cache -l300M
www-data 24064 0.0 6.6 590932 138868 ? Sl 00:20 0:01 /usr/sbin/apache2 -k start
www-data 24065 0.0 6.5 533592 137812 ? Sl 00:20 0:00 /usr/sbin/apache2 -k start
www-data 24068 0.0 6.3 500408 132372 ? Sl 00:20 0:00 /usr/sbin/apache2 -k start
www-data 24357 0.0 6.5 525444 138352 ? Sl 00:47 0:00 /usr/sbin/apache2 -k start
www-data 24389 0.0 6.3 533592 133604 ? S 00:50 0:00 /usr/sbin/apache2 -k start
www-data 24527 0.0 6.5 525396 137028 ? Sl 01:06 0:00 /usr/sbin/apache2 -k start
www-data 26006 0.0 6.3 525396 132996 ? S 01:48 0:00 /usr/sbin/apache2 -k start
www-data 26023 0.0 6.3 525396 133952 ? S 01:50 0:00 /usr/sbin/apache2 -k start
www-data 26304 0.0 6.6 528468 140504 ? Sl 02:18 0:00 /usr/sbin/apache2 -k start
www-data 26305 0.0 6.4 523348 135396 ? Sl 02:18 0:00 /usr/sbin/apache2 -k start
www-data 27902 0.0 6.4 590932 134240 ? S 02:49 0:00 /usr/sbin/apache2 -k start
www-data 27912 0.0 6.2 523348 130988 ? S 02:51 0:00 /usr/sbin/apache2 -k start
www-data 27942 0.0 6.4 523348 134744 ? Sl 02:54 0:00 /usr/sbin/apache2 -k start
www-data 28508 0.0 6.3 523348 132292 ? S 03:51 0:00 /usr/sbin/apache2 -k start
www-data 28518 0.0 6.4 528468 134736 ? S 03:52 0:00 /usr/sbin/apache2 -k start
www-data 29919 0.0 6.3 518800 132240 ? Sl 04:28 0:00 /usr/sbin/apache2 -k start
www-data 30164 0.0 6.1 518800 128652 ? S 04:52 0:00 /usr/sbin/apache2 -k start
www-data 30168 0.0 6.1 518800 129576 ? S 04:53 0:00 /usr/sbin/apache2 -k start
www-data 30418 0.0 6.7 528468 140668 ? Sl 05:17 0:00 /usr/sbin/apache2 -k start
www-data 30463 0.0 6.3 518800 132128 ? Sl 05:21 0:00 /usr/sbin/apache2 -k start
www-data 31799 0.0 6.1 518800 129268 ? S 05:52 0:00 /usr/sbin/apache2 -k start
www-data 31813 0.0 6.4 528468 134808 ? S 05:54 0:00 /usr/sbin/apache2 -k start
www-data 31881 0.0 6.4 515152 135252 ? Sl 06:00 0:00 /usr/sbin/apache2 -k start
www-data 32005 0.0 6.2 517776 131220 ? Sl 06:12 0:00 /usr/sbin/apache2 -k start
www-data 32405 0.0 6.0 517776 127832 ? S 06:52 0:00 /usr/sbin/apache2 -k start
www-data 32435 0.0 6.1 515152 129456 ? S 06:55 0:00 /usr/sbin/apache2 -k start
Apache server status (ExtendedStatus OFF) gives:
Server Version: Apache/2.2.14 (Ubuntu) mod_ssl/2.2.14 OpenSSL/0.9.8k mod_perl/2.0.4 Perl/v5.10.1
Server Built: Mar 8 2013 16:46:35
Current Time: Wednesday, 05-Jun-2013 12:17:22 CEST
Restart Time: Wednesday, 05-Jun-2013 00:16:19 CEST
Parent Server Generation: 2
Server uptime: 12 hours 1 minute 3 seconds
19 requests currently being processed, 2 idle workers
GGGGGGGGGGGGGG.GWG_G_..W........................................
................................................................
................................................................
................................................................
Scoreboard Key:
"_" Waiting for Connection, "S" Starting up, "R" Reading Request,
"W" Sending Reply, "K" Keepalive (read), "D" DNS Lookup,
"C" Closing connection, "L" Logging, "G" Gracefully finishing,
"I" Idle cleanup of worker, "." Open slot with no current process
PID Key:
24527 in state: G , 27942 in state: G , 5796 in state: G
26304 in state: G , 26305 in state: G , 30418 in state: G
24064 in state: G , 24065 in state: G , 31881 in state: G
32005 in state: G , 24068 in state: G , 29919 in state: G
1324 in state: G , 30463 in state: G , 5711 in state: G
8018 in state: W , 1407 in state: G , 8019 in state: _
2043 in state: G , 8020 in state: _ , 7854 in state: W
To obtain a full report with current status information you need to use the ExtendedStatus On directive.
SSL/TLS Session Cache Status:
cache type: SHMCB, shared memory: 512000 bytes, current sessions: 0
subcaches: 32, indexes per subcache: 133
index usage: 0%, cache usage: 0%
total sessions stored since starting: 4
total sessions expired since starting: 4
total (pre-expiry) sessions scrolled out of the cache: 0
total retrieves since starting: 0 hit, 0 miss
total removes since starting: 0 hit, 0 miss
So you can see that most of the processes hang in the G status (Gracefully finishing).
Update 1:
Using apache server status with "ExtendedStatus On" we see that the processes are stuck in the W status (Sending reply): (I replaced the true IPs with ipX.domain.com)
Server Version: Apache/2.2.14 (Ubuntu) mod_ssl/2.2.14 OpenSSL/0.9.8k mod_perl/2.0.4 Perl/v5.10.1
Server Built: Mar 8 2013 16:46:35
Current Time: Wednesday, 05-Jun-2013 18:49:48 CEST
Restart Time: Wednesday, 05-Jun-2013 14:31:17 CEST
Parent Server Generation: 0
Server uptime: 4 hours 18 minutes 31 seconds
Total accesses: 3129 - Total Traffic: 111.9 MB
CPU Usage: u2.29 s.18 cu0 cs0 - .0159% CPU load
.202 requests/sec - 7.4 kB/second - 36.6 kB/request
6 requests currently being processed, 2 idle workers
WWW.W._WW..._...................................................
................................................................
................................................................
................................................................
Scoreboard Key:
"_" Waiting for Connection, "S" Starting up, "R" Reading Request,
"W" Sending Reply, "K" Keepalive (read), "D" DNS Lookup,
"C" Closing connection, "L" Logging, "G" Gracefully finishing,
"I" Idle cleanup of worker, "." Open slot with no current process
Srv PID Acc M CPU SS Req Conn Child Slot Client VHost Request
0-0 7926 1/28/390 W 0.00 2913 0 0.2 1.15 11.63 ip1.domain.com www.domain.com GET /de HTTP/1.1
1-0 5432 0/10/183 W 0.00 10005 0 0.0 0.59 7.51 ip6.domain.com def.domain.com HEAD / HTTP/1.1
2-0 7878 1/44/403 W 0.00 2710 0 0.2 2.29 13.22 ip1.domain.com www.domain.com GET /de HTTP/1.1
3-0 - 0/0/467 . 0.00 203 0 0.0 0.00 19.51 ip2.domain.com def.domain.com NULL
4-0 5854 1/58/223 W 0.01 6137 0 0.2 1.74 12.29 ip1.domain.com www.domain.com GET /de HTTP/1.1
5-0 - 0/0/359 . 1.40 204 0 0.0 0.00 10.42 ip2.domain.com def.domain.com NULL
6-0 9534 0/60/244 _ 0.63 69 0 0.0 1.60 6.70 ip1.domain.com def.domain.com NULL
7-0 5861 1/32/84 W 0.00 6746 0 0.2 1.55 3.18 ip1.domain.com www.domain.com GET /de HTTP/1.1
8-0 11401 98/106/440 W 0.17 0 0 189.2 0.38 15.68 ip5.domain.com def.domain.com GET /server-status HTTP/1.1
9-0 - 0/0/152 . 0.00 207 1608 0.0 0.00 8.06 ip2.domain.com def.domain.com NULL
10-0 - 0/0/31 . 0.00 206 1639 0.0 0.00 0.79 ip2.domain.com def.domain.com NULL
11-0 - 0/0/99 . 0.24 205 0 0.0 0.00 1.83 ip2.domain.com def.domain.com NULL
12-0 11404 0/4/24 _ 0.02 104 18 0.0 0.00 0.38 ip3.domain.com www.domain.com GET /robots.txt HTTP/1.1
13-0 - 0/0/8 . 0.00 208 0 0.0 0.00 0.06 ip1.domain.com www.domain.com GET /de HTTP/1.1
14-0 - 0/0/16 . 0.00 920 47 0.0 0.00 0.59 ip4.domain.com def.domain.com NULL
15-0 - 0/0/2 . 0.00 5661 3905 0.0 0.00 0.08 ip2.domain.com def.domain.com NULL
16-0 - 0/0/3 . 0.00 5686 0 0.0 0.00 0.00 ip2.domain.com def.domain.com NULL
17-0 - 0/0/1 . 0.00 5694 1 0.0 0.00 0.00 127.0.0.1 def.domain.com GET / HTTP/1.0
Srv Child Server number - generation
PID OS process ID
Acc Number of accesses this connection / this child / this slot
M Mode of operation
CPU CPU usage, number of seconds
SS Seconds since beginning of most recent request
Req Milliseconds required to process most recent request
Conn Kilobytes transferred this connection
Child Megabytes transferred this child
Slot Total megabytes transferred this slot
SSL/TLS Session Cache Status:
cache type: SHMCB, shared memory: 512000 bytes, current sessions: 0
subcaches: 32, indexes per subcache: 133
index usage: 0%, cache usage: 0%
total sessions stored since starting: 37
total sessions expired since starting: 37
total (pre-expiry) sessions scrolled out of the cache: 0
total retrieves since starting: 8 hit, 0 miss
total removes since starting: 0 hit, 0 miss
As you can see here, there are a few processes with a very high SS (Time since last request) value which means they are stuck. The requests were for different VHosts and also from different clients.
If I look into the acces.log files and search for the entries for such a process (I added the PID to log), the last request they served was most of the times a simple image file directly elaborated by apache.
The important parts of the apache2 config are:
<IfModule mpm_prefork_module>
StartServers 1
MinSpareServers 1
MaxSpareServers 3
MaxClients 30
MaxRequestsPerChild 0
</IfModule>
KeepAlive On
MaxKeepAliveRequests 100
KeepAliveTimeout 15
Update 3: All the enabled apache2 modules:
root@ser:~# apache2ctl -M
Loaded Modules:
core_module (static)
log_config_module (static)
logio_module (static)
mpm_prefork_module (static)
http_module (static)
so_module (static)
alias_module (shared)
auth_basic_module (shared)
authn_file_module (shared)
authz_default_module (shared)
authz_groupfile_module (shared)
authz_host_module (shared)
authz_user_module (shared)
autoindex_module (shared)
cache_module (shared)
cgi_module (shared)
deflate_module (shared)
dir_module (shared)
disk_cache_module (shared)
env_module (shared)
expires_module (shared)
filter_module (shared)
headers_module (shared)
mem_cache_module (shared)
mime_module (shared)
negotiation_module (shared)
version_module (shared)
pagespeed_module (shared)
perl_module (shared)
php5_module (shared)
proxy_module (shared)
proxy_http_module (shared)
reqtimeout_module (shared)
rewrite_module (shared)
setenvif_module (shared)
ssl_module (shared)
status_module (shared)
unique_id_module (shared)
Syntax OK
Update 2: Here is the stacktrace of a hanging process. All of the stacktraces of the stuck ones are exactly the same:
5861:/usr/sbin/apache2-kstart
#0 0x00002ad420a4448d in /lib/libpthread-2.11.1.so: waitpid
#1 0x00002ad4258dc507 in /usr/lib/libperl.so.5.10.1: Perl_wait4pid
#2 0x00002ad4258dc760 in /usr/lib/libperl.so.5.10.1: Perl_my_pclose
#3 0x00002ad425949b1d in /usr/lib/libperl.so.5.10.1: Perl_io_close
#4 0x00002ad425949c89 in /usr/lib/libperl.so.5.10.1: Perl_do_close
#5 0x00002ad42593d922 in /usr/lib/libperl.so.5.10.1: Perl_pp_close
#6 0x00002ad4258f3346 in /usr/lib/libperl.so.5.10.1: Perl_runops_standard
#7 0x00002ad42589a8cf in /usr/lib/libperl.so.5.10.1: Perl_call_sv
#8 0x00002ad4256202f6 in /usr/lib/apache2/modules/mod_perl.so: modperl_callback
#9 0x00002ad425620a3a in /usr/lib/apache2/modules/mod_perl.so: modperl_callback_run_handlers
#10 0x00002ad42562101f in /usr/lib/apache2/modules/mod_perl.so: modperl_callback_per_dir
#11 0x00002ad42561a99f in /usr/lib/apache2/modules/mod_perl.so: -
#12 0x00002ad42561ad06 in /usr/lib/apache2/modules/mod_perl.so: modperl_response_handler
#13 0x00002ad41ff58320 in /usr/lib/apache2/mpm-prefork/apache2: ap_run_handler (/build/buildd/apache2-2.2.14/server/config.c:159)
#14 0x00002ad41ff5bc88 in /usr/lib/apache2/mpm-prefork/apache2: ap_invoke_handler (/build/buildd/apache2-2.2.14/server/config.c:377)
#15 0x00002ad41ff69878 in /usr/lib/apache2/mpm-prefork/apache2: ap_process_request (/build/buildd/apache2-2.2.14/modules/http/http_request.c:282)
#16 0x00002ad41ff66728 in /usr/lib/apache2/mpm-prefork/apache2: ap_process_http_connection (/build/buildd/apache2-2.2.14/modules/http/http_core.c:190)
#17 0x00002ad41ff5fed8 in /usr/lib/apache2/mpm-prefork/apache2: ap_run_process_connection (/build/buildd/apache2-2.2.14/server/connection.c:43)
#18 0x00002ad41ff6e847 in /usr/lib/apache2/mpm-prefork/apache2: child_main (/build/buildd/apache2-2.2.14/server/mpm/prefork/prefork.c:663)
#19 0x00002ad41ff6eb5a in /usr/lib/apache2/mpm-prefork/apache2: make_child (/build/buildd/apache2-2.2.14/server/mpm/prefork/prefork.c:758)
#20 0x00002ad41ff6f7e4 in /usr/lib/apache2/mpm-prefork/apache2: perform_idle_server_maintenance (/build/buildd/apache2-2.2.14/server/mpm/prefork/prefork.c:883)
#21 0x00002ad41ff44350 in /usr/lib/apache2/mpm-prefork/apache2: main (/build/buildd/apache2-2.2.14/server/main.c:742)
#22 0x00002ad420c70c4d in /lib/libc-2.11.1.so: __libc_start_main@@GLIBC_2.2.5
#23 0x00002ad41ff432e9 in /usr/lib/apache2/mpm-prefork/apache2: _start
For comaprison the stacktrace of a process which doesn't hang:
9741:/usr/sbin/apache2-kstart
#0 0x00002ad420d3d7d7 in /lib/libc-2.11.1.so: semop@@GLIBC_2.2.5
#1 0x00002ad42081a0c3 in /usr/lib/libapr-1.so.0.3.8: -
#2 0x00002ad42081ae47 in /usr/lib/libapr-1.so.0.3.8: apr_proc_mutex_lock
#3 0x00002ad41ff6e754 in /usr/lib/apache2/mpm-prefork/apache2: accept_mutex_on (/build/buildd/apache2-2.2.14/server/mpm/prefork/prefork.c:206)
#4 0x00002ad41ff6eb5a in /usr/lib/apache2/mpm-prefork/apache2: make_child (/build/buildd/apache2-2.2.14/server/mpm/prefork/prefork.c:758)
#5 0x00002ad41ff6f7e4 in /usr/lib/apache2/mpm-prefork/apache2: perform_idle_server_maintenance (/build/buildd/apache2-2.2.14/server/mpm/prefork/prefork.c:883)
#6 0x00002ad41ff44350 in /usr/lib/apache2/mpm-prefork/apache2: main (/build/buildd/apache2-2.2.14/server/main.c:742)
#7 0x00002ad420c70c4d in /lib/libc-2.11.1.so: __libc_start_main@@GLIBC_2.2.5
#8 0x00002ad41ff432e9 in /usr/lib/apache2/mpm-prefork/apache2: _start
Here my Question:
How can I find out what blocks the apache instances from shutting down successfully?
Update 4 Googling for 'apache sending reply hung' results in a few posts where people had problems with buggy scripts/mysql connections. As it can be seen in the stacktrace, the processes which got stuck did use mod_perl, maybe there's a problem... Will dig into it
