Hello Alex,
Thanks for the analysis.
Squid only allows alphanumeric characters in the service name, so it refuses to use the original service name in the -n option (-n squid.user.service).
I added -n squiduser option to the ExecStart string of the second instance.
Now it looks good:
# the first instance
lsof -p 3746105 | grep shm
squid 3746105 root mem REG 0,23 525572 1213614834 /dev/shm/squid-cf__queues.shm
squid 3746105 root mem REG 0,23 136 1213614835 /dev/shm/squid-cf__readers.shm
squid 3746105 root mem REG 0,23 8 1213614833 /dev/shm/squid-cf__metadata.shm
squid 3746105 root 7u REG 0,23 8 1213614833 /dev/shm/squid-cf__metadata.shm
squid 3746105 root 8u REG 0,23 525572 1213614834 /dev/shm/squid-cf__queues.shm
squid 3746105 root 9u REG 0,23 136 1213614835 /dev/shm/squid-cf__readers.shm
squid 3746105 root mem REG 0,23 525572 1213614834 /dev/shm/squid-cf__queues.shm
squid 3746105 root mem REG 0,23 136 1213614835 /dev/shm/squid-cf__readers.shm
squid 3746105 root mem REG 0,23 8 1213614833 /dev/shm/squid-cf__metadata.shm
squid 3746105 root 7u REG 0,23 8 1213614833 /dev/shm/squid-cf__metadata.shm
squid 3746105 root 8u REG 0,23 525572 1213614834 /dev/shm/squid-cf__queues.shm
squid 3746105 root 9u REG 0,23 136 1213614835 /dev/shm/squid-cf__readers.shm
# the second instance
lsof -p 3685356 | grep shm
squid.use 3685356 root mem REG 0,23 2093368 1212704041 /dev/shm/squiduser-tls_session_cache.shm
squid.use 3685356 root mem REG 0,23 525572 1212704039 /dev/shm/squiduser-cf__queues.shm
squid.use 3685356 root mem REG 0,23 136 1212704040 /dev/shm/squiduser-cf__readers.shm
squid.use 3685356 root mem REG 0,23 8 1212704038 /dev/shm/squiduser-cf__metadata.shm
squid.use 3685356 root 6u REG 0,23 8 1212704038 /dev/shm/squiduser-cf__metadata.shm
squid.use 3685356 root 7u REG 0,23 525572 1212704039 /dev/shm/squiduser-cf__queues.shm
squid.use 3685356 root 8u REG 0,23 136 1212704040 /dev/shm/squiduser-cf__readers.shm
squid.use 3685356 root 9u REG 0,23 2093368 1212704041 /dev/shm/squiduser-tls_session_cache.shm
lsof -p 3685356 | grep shm
squid.use 3685356 root mem REG 0,23 2093368 1212704041 /dev/shm/squiduser-tls_session_cache.shm
squid.use 3685356 root mem REG 0,23 525572 1212704039 /dev/shm/squiduser-cf__queues.shm
squid.use 3685356 root mem REG 0,23 136 1212704040 /dev/shm/squiduser-cf__readers.shm
squid.use 3685356 root mem REG 0,23 8 1212704038 /dev/shm/squiduser-cf__metadata.shm
squid.use 3685356 root 6u REG 0,23 8 1212704038 /dev/shm/squiduser-cf__metadata.shm
squid.use 3685356 root 7u REG 0,23 525572 1212704039 /dev/shm/squiduser-cf__queues.shm
squid.use 3685356 root 8u REG 0,23 136 1212704040 /dev/shm/squiduser-cf__readers.shm
squid.use 3685356 root 9u REG 0,23 2093368 1212704041 /dev/shm/squiduser-tls_session_cache.shm
Kind regards,
Ankor.
пт, 7 мар. 2025 г. в 17:48, Alex Rousskov <rousskov@xxxxxxxxxxxxxxxxxxxxxxx>:
On 2025-03-07 06:50, Andrey K wrote:
> Squid Cache: Version 6.13
> Service Name: squid
> Squid Cache: Version 6.10
> Service Name: squid
> # the first instance
> 1318 DEL ... 30205 /dev/shm/squid-cf__queues.shm
> 1318 DEL ... 30206 /dev/shm/squid-cf__readers.shm
> 1318 DEL ... 30204 /dev/shm/squid-cf__metadata.shm
> 1318 8u ... 8 30204 /dev/shm/squid-cf__metadata.shm (deleted)
> 1318 9u ... 525572 30205 /dev/shm/squid-cf__queues.shm (deleted)
> 1318 10u ... 136 30206 /dev/shm/squid-cf__readers.shm (deleted)
>
> # the second instance
> 1514 mem ... 2093368 31497 /dev/shm/squid-tls_session_cache.shm
> 1514 mem ... 525572 31495 /dev/shm/squid-cf__queues.shm
> 1514 mem ... 136 31496 /dev/shm/squid-cf__readers.shm
> 1514 mem ... 8 31494 /dev/shm/squid-cf__metadata.shm
> 1514 6u ... 8 31494 /dev/shm/squid-cf__metadata.shm
> 1514 7u ... 525572 31495 /dev/shm/squid-cf__queues.shm
> 1514 8u ... 136 31496 /dev/shm/squid-cf__readers.shm
> 1514 9u ... 2093368 31497 /dev/shm/squid-tls_session_cache.shm
As suspected, these two Squid instances use the same shared memory
segments (e.g., /dev/shm/squid-cf*). Such shared use violates critical
code assumptions and results in undefined behavior.
> Maybe I'm not experiencing any difficulties because I have caching turned off on
> both instances?
Well, you _are_ experiencing at least one difficulty -- the assertion
that started this email thread. If you have fully disabled caching, the
difficulties you experience should not include cache corruption.
However, it looks like at least one of the two instances does cache TLS
sessions (in /dev/shm/squid-tls_session_cache.shm). If both instances do
that, then all bets are off!
FWIW, related future Squid improvements may include:
* Detecting such shared memory segments clashes; refusing to start.
* Disabling shared memory use when caching is completely disabled.
Quality pull requests welcome.
Cheers,
Alex.
> чт, 6 мар. 2025 г. в 17:11, Alex Rousskov:
>
> On 2025-03-06 08:59, Amos Jeffries wrote:
> > On 6/03/25 19:17, Andrey K wrote:
> >> Hello,
> >>
> >> I have a similar configuration: two SMP squids running on the
> same OEL
> >> host.
> >>
> >> They were built with different configurations: with different
> >> installation path prefixes and different names of binary files:
> squid
> >> and squid.user and they listen to different ports.
> >> They are launched from two different services:squid.service and
> >> squid.user.service with the service Type=forking:
> >>
> >> ExecStart=/usr/sbin/squid -sYC
> >> ExecStart=/sbin/squid.user -f /etc/squid.user/squid.conf
> >>
> >> I have not experienced any troubles with this configuration yet.
> >>
> >> /> Please be aware that "squid -n ..." is a REQUIREMENT for running/
> >> /multiple Squid instances on the same machine regardless of what
> features
> >> are used./
> >>
> >> Could you please tell me if I should use the -n option in the
> >> ExecStart strings?
> >> The arguments of the options should be the service names?
> >>
> >> ExecStart=/usr/sbin/squid -sYC -n squid.service
> >> ExecStart=/sbin/squid.user -f /etc/squid.user/squid.conf -n
> >> squid.user.service
> >>
> > Yes you should. The different ./configure options has helped you
> avoid
> > major issues, but some may still appear.
>
> I agree. Moreover, I do not understand how your two SMP Squids could
> work correctly without distinct service names because (on OEL) I would
> expect them to share the same shared memory segments (which they must
> not do to remain distinct instances).
>
> What is your Squid version? Can you tell how your Squids name their
> shared memory segment "files"? For example, on some Linux OSes, those
> segments could be in /var/run/shm/ with names like
> squid-tr_map_anchors.shm and squid-tr_spaces.shm.
>
>
> Thank you,
>
> Alex.
>
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