[squid-users] Restarts without any apparent reason

Squid 3.1.5 is stopping (and being restarted by runit) for no apparent
reason. From the cache.log:

2010/07/29 14:55:39| could not parse headers from on disk structure!
2010/07/29 14:55:39| could not parse headers from on disk structure!
2010/07/29 14:57:39| could not parse headers from on disk structure!
2010/07/29 14:58:29| could not parse headers from on disk structure!
2010/07/29 14:58:52| could not parse headers from on disk structure!
2010/07/29 15:00:22| could not parse headers from on disk structure!
2010/07/29 15:00:22| could not parse headers from on disk structure!
2010/07/29 15:00:30| could not parse headers from on disk structure!
2010/07/29 15:00:57| could not parse headers from on disk structure!
2010/07/29 15:02:34| could not parse headers from on disk structure!
2010/07/29 15:02:52| could not parse headers from on disk structure!

2010/07/29 15:02:57| Starting Squid Cache version 3.1.5 for i686-pc-linux-gnu...
2010/07/29 15:02:57| Process ID 8888
2010/07/29 15:02:57| With 4096 file descriptors available
2010/07/29 15:02:57| Initializing IP Cache...
2010/07/29 15:02:57| DNS Socket created at [::], FD 5
2010/07/29 15:02:57| Adding domain charite.de from /etc/resolv.conf
2010/07/29 15:02:57| Adding nameserver 127.0.0.1 from /etc/resolv.conf
2010/07/29 15:02:57| Adding nameserver 141.42.2.22 from /etc/resolv.conf
2010/07/29 15:02:57| Adding nameserver 141.42.3.33 from /etc/resolv.conf
2010/07/29 15:02:57| Unlinkd pipe opened on FD 10
2010/07/29 15:02:57| Local cache digest enabled; rebuild/rewrite every 3600/3600 sec
2010/07/29 15:02:57| Store logging disabled
2010/07/29 15:02:57| Swap maxSize 15360000 + 8192 KB, estimated 1921024 objects
2010/07/29 15:02:57| Target number of buckets: 96051
2010/07/29 15:02:57| Using 131072 Store buckets
2010/07/29 15:02:57| Max Mem size: 8192 KB
2010/07/29 15:02:57| Max Swap size: 15360000 KB
2010/07/29 15:02:57| Version 1 of swap file with LFS support detected...
2010/07/29 15:02:57| Rebuilding storage in /squid-cache (DIRTY)
2010/07/29 15:02:57| Using Least Load store dir selection
2010/07/29 15:02:57| Set Current Directory to /tmp
2010/07/29 15:02:57| Loaded Icons.
2010/07/29 15:02:57| Accepting HTTP connections at [::]:8080, FD 15.
2010/07/29 15:02:57| Accepting ICP messages at [::]:3130, FD 16.
2010/07/29 15:02:57| Accepting HTCP messages on port 4827, FD 17.
2010/07/29 15:02:57| Accepting SNMP messages on [::]:3401, FD 18.
2010/07/29 15:02:57| WARNING: Peer looks like this host
2010/07/29 15:02:57| Ignoring Sibling proxy-cvk-1.charite.de/8080/3130
2010/07/29 15:02:57| Squid modules loaded: 0
2010/07/29 15:02:57| Adaptation support is on
2010/07/29 15:02:57| Ready to serve requests.
2010/07/29 15:02:57| Store rebuilding is 0.87% complete
2010/07/29 15:03:01| Done reading /squid-cache swaplog (472746 entries)
2010/07/29 15:03:01| Finished rebuilding storage from disk.
2010/07/29 15:03:01| 468209 Entries scanned
2010/07/29 15:03:01| 0 Invalid entries.
2010/07/29 15:03:01| 0 With invalid flags.
2010/07/29 15:03:01| 463707 Objects loaded.
2010/07/29 15:03:01| 0 Objects expired.
2010/07/29 15:03:01| 4502 Objects cancelled.
2010/07/29 15:03:01| 0 Duplicate URLs purged.
2010/07/29 15:03:01| 0 Swapfile clashes avoided.
2010/07/29 15:03:01| Took 4.46 seconds (103937.58 objects/sec).
2010/07/29 15:03:01| Beginning Validation Procedure
2010/07/29 15:03:02| Completed Validation Procedure
2010/07/29 15:03:02| Validated 927437 Entries
2010/07/29 15:03:02| store_swap_size = 9418360
2010/07/29 15:03:02| storeLateRelease: released 0 objects
2010/07/29 15:03:02| Configuring Sibling proxy-cbf-1.charite.de/8080/3130
2010/07/29 15:03:02| Configuring Sibling proxy-cbf-2.charite.de/8080/3130
2010/07/29 15:03:02| Configuring Sibling proxy-cvk-2.charite.de/8080/3130

Where can I find the reason?
Squid3 runs as the user "proxy":

proxy 8888 38.9 5.2 126356 108980 ? S 15:02 1:26 /usr/sbin/squid3 -N

The runit script is this:

cd /etc/service/squid3
echo 128 > /proc/sys/kernel/msgmni
ulimit -n 4096 -c unlimited
exec 2>&1
exec /usr/sbin/squid3 -N

The config file specifies:

coredump_dir /tmp
cache_effective_user proxy
cache_effective_group proxy
cache_dir diskd /squid-cache 15000 32 32

Yet I don't see a corefile in /tmp or /squid-cache

# ls -ld /squid-cache/
drwx------ 35 proxy proxy 4096 2010-07-29 15:03 /squid-cache/

Right now I'm running it in the debugger

-- 
Ralf Hildebrandt
  Geschäftsbereich IT | Abteilung Netzwerk
  Charité - Universitätsmedizin Berlin
  Campus Benjamin Franklin
  Hindenburgdamm 30 | D-12203 Berlin
  Tel. +49 30 450 570 155 | Fax: +49 30 450 570 962
  ralf.hildebrandt@charite.de | http://www.charite.de