Php – How to debug/fix a php/apache segmentation fault while using memcache (redundant) for session storage

• os: debian squeeze (up2date)
• 2 apache mod php webserver
• 2 memcache server

i have to apache mod_php nodes which use two memcache server for redundant session storage (used variant 3 from https://serverfault.com/a/165584).

memcache.ini

extension=memcache.so

[memcache]
memcache.dbpath="/var/lib/memcache"
memcache.maxreclevel=0
memcache.maxfiles=0
memcache.archivememlim=0
memcache.maxfilesize=0
memcache.maxratio=0

memcache.allow_failover=1
memcache.hash_strategy=consistent
memcache.session_redundancy=3

php.ini

session.save_handler = memcache
session.save_path="tcp://192.168.0.11:11211?persistent=1&weight=1&timeout=1&retry_interval=15,tcp://192.168.0.19:11211?persistent=1&weight=1&timeout=1&retry_interval=15"

everything works fine using only one memcache server, it also works quite nice with two or two redundant server. the sessions are written to both servers (i can verify it with phpmemcache admin), but as soon as i kill one node (stop one memcache server) i get into trouble.

the memcache servers look like the are having one "master" server and one "2nd" server. there are less problems when i kill the 2nd server, but as soon as shut down the 1st memcache server (having the 2nd one up), apache error log gets filled with segmentation faults on each connection try.

i also tried memcache.session_redundancy=3 but i have the value 3 because of the bug https://bugs.php.net/bug.php?id=58585

ps. if you use firefox use: https://addons.mozilla.org/en-US/firefox/addon/its-all-text i just lost my question on pressing back after running into the "are you human" stuff of serverfault….