Help:: Listen queue overflow killing servers
Paul Macdonald
paul at ifdnrg.com
Fri Jul 26 13:08:29 UTC 2019
On 26/07/2019 13:52, Robert Schulze wrote:
> Hi,
>
> Am 26.07.19 um 13:58 schrieb Paul Macdonald via freebsd-questions:
> I think, these processes waiting for disk i/o are actually your problem.
> Since they cannot answer further requests, they run into the listen
> queue overflow.
>
> You should check the processes with procstat:
>
> list kernel threads:
> # procstat -kk <PID>
>
> list open files:
> # procstat -f <PID>
One of the things we do (whihc may be bad) is to log to a single file (
e.g all.sites.log, this doesn;t seem to cause problems in general , but
i can see how if there's X child processes then they may all need write
locks)
Is that a really bad idea? ( Often handy to have one file for differnet
vhosts, but maybe that needs a rethink)
In this case the drive is NVMe, and there's actually only a handful of
sites, (Other servers have several hundreds of sites, much busy but
don;t display the issue)
In answer to some of the other suggestions, its not actually under high
load ( 5000 lines in the apache log for the whole day), and system has
16C/32T, 128GB RAM
ZFS is using a bunch of RAM as i've not limited the ARC, but there's
27GB free currently.
I guess i actually have 2 questions
1) why are the queues filling up (i'll revert to seperate logs to see
if that helps, although the issue is sporadic, and first time on this box)
2) Once the queues are over limit, is this actually unresolvable other
than a hard reboot?
I've increased the queue size via
sysctl kern.ipc.somaxconn
to 1024 for now
but netstat -Lan still shows
tcp4 0/0/128 x.x.x.x.443
tcp4 0/0/128 x.x.x.x.80
thanks for assiestence
Paul
> with kind regards,
> Robert Schulze
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