[squid-users] Too many ERROR: Collapsed forwarding queue overflow for kid2 at 1024 items

[Loučanský Lukáš]

Hi,
recently I'm facing too many ERROR: Collapsed forwarding queue overflow for kid2 at 1024 items lines in my Squid 5.2 log files. So far I was able to find it in the CollapsedForwarding.cc func Broadcast as a result of a full queue which limits beeing defined by the QueueCapacity const at 1024 items.
 
Now I have squid in VM with 6 CPU cores, 16GB RAM and 2 workers and 4 diskers with rock (various slot sizes). /var/run/shm squid-cf*.shm files exist. Mounted with
shm        /dev/shm    tmpfs    nodev,nosuid,noexec,size=8G    0    0 (is 8GB enough or too much?)

I have collapsed_forwarding on

Could someone elaborate how the queue is filled - what is clogging it? What can be done to work it out? I don't mind too much if I have to turn collapsed forwarding off - as I don’t see any significant gain. On the other hand I don't see any slowdown (because of non-cacheable object being forwarded individually) either.

Thanks!
LL