Three Apache2 web servers running a PHP 5.2.3 web site. We’re using Memcache to cache rendered pages but also as the storage engine of the PHP Sessions.
At peak traffic times we’re getting Apache segmentation faults on all three web servers and all HTTPD child processes segfault.
My gut tells me that the increased Memcache traffic is stopping PHP sessions from being created or cleaned up and thus the processes die. Is it possible for someone to confirm that from the following? :
#0 _zend_mm_free_int (heap=0x7fb67a075820, p=0x7fb67a011538) at /usr/src/debug/php-5.3.3/Zend/zend_alloc.c:2018
#1 0x00007fb665d02e82 in mmc_buffer_free (request=0x7fb67a011548) at /usr/src/debug/php-pecl-memcache-3.0.4/memcache-3.0.4/memcache_pool.c:50
#2 mmc_request_free (request=0x7fb67a011548) at /usr/src/debug/php-pecl-memcache-3.0.4/memcache-3.0.4/memcache_pool.c:169
#3 0x00007fb665d031ea in mmc_pool_free (pool=0x7fb67a00e458) at /usr/src/debug/php-pecl-memcache-3.0.4/memcache-3.0.4/memcache_pool.c:917
#4 0x00007fb665d0a2f1 in ps_close_memcache (mod_data=0x7fb66d625440) at /usr/src/debug/php-pecl-memcache-3.0.4/memcache-3.0.4/memcache_session.c:185
#5 0x00007fb66d1b0935 in php_session_save_current_state () at /usr/src/debug/php-5.3.3/ext/session/session.c:625
#6 php_session_flush () at /usr/src/debug/php-5.3.3/ext/session/session.c:1517
#7 0x00007fb66d1b0c1b in zm_deactivate_session (type=<value optimized out>, module_number=<value optimized out>) at /usr/src/debug/php-5.3.3/ext/session/session.c:2171
#8 0x00007fb66d2a719c in module_registry_cleanup (module=<value optimized out>) at /usr/src/debug/php-5.3.3/Zend/zend_API.c:2150
#9 0x00007fb66d2b1994 in zend_hash_reverse_apply (ht=0x7fb66d629d60, apply_func=0x7fb66d2a7180 <module_registry_cleanup>) at /usr/src/debug/php-5.3.3/Zend/zend_hash.c:755
#10 0x00007fb66d2a5c0d in zend_deactivate_modules () at /usr/src/debug/php-5.3.3/Zend/zend.c:866
#11 0x00007fb66d2541b5 in php_request_shutdown (dummy=<value optimized out>) at /usr/src/debug/php-5.3.3/main/main.c:1607
#12 0x00007fb66d32e037 in php_apache_request_dtor (r=0x7fb67a229658) at /usr/src/debug/php-5.3.3/sapi/apache2handler/sapi_apache2.c:509
#13 php_handler (r=0x7fb67a229658) at /usr/src/debug/php-5.3.3/sapi/apache2handler/sapi_apache2.c:681
#14 0x00007fb6784166f0 in ap_run_handler (r=0x7fb67a229658) at /usr/src/debug/httpd-2.2.15/server/config.c:158
#15 0x00007fb678419f58 in ap_invoke_handler (r=0x7fb67a229658) at /usr/src/debug/httpd-2.2.15/server/config.c:372
#16 0x00007fb6784254f0 in ap_process_request (r=0x7fb67a229658) at /usr/src/debug/httpd-2.2.15/modules/http/http_request.c:282
#17 0x00007fb678422418 in ap_process_http_connection (c=0x7fb67a2193a8) at /usr/src/debug/httpd-2.2.15/modules/http/http_core.c:190
#18 0x00007fb67841e1b8 in ap_run_process_connection (c=0x7fb67a2193a8) at /usr/src/debug/httpd-2.2.15/server/connection.c:43
#19 0x00007fb678429f4b in child_main (child_num_arg=<value optimized out>) at /usr/src/debug/httpd-2.2.15/server/mpm/prefork/prefork.c:662
#20 0x00007fb67842a21a in make_child (s=0x7fb679cd7860, slot=153) at /usr/src/debug/httpd-2.2.15/server/mpm/prefork/prefork.c:758
#21 0x00007fb67842aea4 in perform_idle_server_maintenance (_pconf=<value optimized out>, plog=<value optimized out>, s=<value optimized out>) at /usr/src/debug/httpd-2.2.15/server/mpm/prefork/prefork.c:893
#22 ap_mpm_run (_pconf=<value optimized out>, plog=<value optimized out>, s=<value optimized out>) at /usr/src/debug/httpd-2.2.15/server/mpm/prefork/prefork.c:1097
#23 0x00007fb678402890 in main (argc=1, argv=0x7fff6fecacb8) at /usr/src/debug/httpd-2.2.15/server/main.c:740
The exact same thing happened to us. Using the stable version of the Memcache client code (2.2.6) fixed it for us.