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Postfix Archives: Re: 451 queue errors due to max open files on

Re: 451 queue errors due to max open files on Linux

Subject: Re: 451 queue errors due to max open files on Linux
From: Wietse Venema (wietseporcupine.org)
Date: Fri Jan 21 2000 - 02:38:57 CST

Rich Graves:
> Jan 20 17:49:07 moe postfix/smtpd[19436]: fatal: accept connection: Too
> many open files in system

Your kernel can't handle more open files. Beef up your kernel. Or
run an O/S that scales better. Or reduce the number of processes
in main.cf (default_process_limit) or in master.cf.

> Which isn't too surprising given that Linux 2.2 defaults to 4096 open files
> and the growing numbers of IMAP users eat nearly 3000 descriptors around
> the clock.
>
> We never hit open file limits with sendmail because load would spike and
> we'd go queue-only (if not refuse connections entirely) much earlier no
> matter how I tuned the config.
>
> Here's what I've done. Let me know if this is clearly stupid.
>
> * Quadruple the kernel open file limit (echo 16384 > /proc/sys/fs/file-max)
>
> * Reduce maxproc for smtpd from 50 to 40 (necessary after the above?)
>
> * Reduce maxproc for local from 50 to 40 (necessary?)
>
> What exactly does "throttling" mean? It didn't stop accepting connections.

If a service fails consistently, the Postfix master will stop
spawning new processes for that service for 60 seconds, in order
to allow the host to recover from overload.

This is so much nicer than running the system into the ground.

Meanwhile, the master can't close the service socket because other
servers still have it open, so the kernel still accepts connections
for the service. Nothing I can do about that.

        Wietse

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