Message: 1
Date: Sun, 6 May 2018 13:21:57 +1000
From: Andy Weal <a...@bizemail.com.au>
To: dovecot@dovecot.org
Subject: 2.3.1 Replication is throwing scary errors
Message-ID: <f4274128-350b-9a74-a344-8e6caeffa...@bizemail.com.au>
Content-Type: text/plain; charset="utf-8"; Format="flowed"
Hi all,
New to the mailing lists but have joined up because of above */2.3.1
Replication is throwing scary errors
/*Brief system configuration
??? MX1 - Main
??? ??? Freebsd 11.1-Release-p9
??? ??? Hosted on a Vultr VM in Sydney AU
??? ??? MTA = Postfix 3.4-20180401
??? ??? Dovecot = 2.3.1
??? ??? File system = ufs
??? MX2 - Backup
??? ??? Freebsd 11.1-Release-p9
??? ???? Running on bare metal - no VM or jails
??? ??? MTA = Postfix 3.4-20180401
??? ??? Dovecot = 2.3.1
??? ??? File system = ufs ( on SSD)
*/
/*Brief sequence of events
1. ??? apx 10 days back upgraded both mx1 and mx2 to dovecot 2.3.1_2
from 2.3.0 ? (service dovecot stop, portmaster upgrade, service
dovecot start)
2. ??? both systems ran ok with no errors for 10 days.
3. ??? Last night I shutdown mx2 and restarted it a few hours later
4. ??? within minutes i was getting the following types of errors on mx2
???????? May 06 12:56:29 doveadm: Error: Couldn't lock
/var/mail/vhosts/example.net/user1/.dovecot-sync.lock:
fcntl(/var/mail/vhosts/example.net/user1/.dovecot-sync.lock, write-lock,
F_SETLKW) locking failed: Timed out after 30 seconds (WRITE lock held by
pid 1960)
? Before i venture down the rabbit hole of fault finding and excess
coffee consumption I was wondering if any of you had any updates on the
problems discussed below.
Cheers for now,
Andy
Hi,
[Formatting is a bit rough, replying from a trimmed digest email]
/Message: 1 />/Date: Fri, 6 Apr 2018 15:04:35 +0200 />/From: Michael Grimm
<trashcan at ellael.org
<https://dovecot.org/mailman/listinfo/dovecot>> />/To: Dovecot Mailing List
<dovecot at dovecot.org
<https://dovecot.org/mailman/listinfo/dovecot>> />/Subject: Re: 2.3.1 Replication is
throwing scary errors />/Message-ID: <E7E7A927-68F8-443F-BA59-E66CED8FE878 at ellael.org
<https://dovecot.org/mailman/listinfo/dovecot>> />/Content-Type: text/plain; charset=utf-8
/>//>/Reuben Farrelly wrote: />>/From: Michael Grimm <trashcan at ellael.org
<https://dovecot.org/mailman/listinfo/dovecot>> />//>>>/[This is Dovecot 2.3.1
at FreeBSD STABLE-11.1 running in two jails at
distinct servers.] />>>/I did upgrade from 2.2.35 to 2.3.1 today, and I do
become pounded by
error messages at server1 (and vice versa at server2) as follows: />>>/| Apr 2
17:12:18 <mail.err> server1.lan dovecot: doveadm: Error:
dsync(server2.lan): I/O has stalled, \ />>>/no activity for 600 seconds (last
sent=mail_change, last
recv=mail_change (EOL)) />>>/| Apr 2 17:12:18 <mail.err> server1.lan dovecot:
doveadm: Error: Timeout
during state=sync_mails \ />>>/(send=changes recv=mail_requests) />>>/[?] />>>/| Apr
2 18:59:03 <mail.err> server1.lan dovecot: doveadm: Error:
dsync(server2.lan): I/O has stalled, \ />>>/no activity for 600 seconds (last sent=mail, last
recv=mail (EOL)) />>>/| Apr 2 18:59:03 <mail.err> server1.lan dovecot: doveadm: Error:
Timeout
during state=sync_mails \ />>>/(send=mails recv=recv_last_common) />>>/I cannot
see in my personal account any missing replications, *but* I
haven't tested this thoroughly enough. I do have customers being
serviced at these productive servers, *thus* I'm back to 2.2.35 until I
do understand or have learned what is going on. />//>/In my reply to this
statement of mine I mentioned that I have seen those
timeouts quite some times during the past year. Thus, I upgraded to
2.3.1 again, and boom: after some hours I ended up in hanging processes
[1] like (see Remko's mail in addition) ... />//>/doveadm-server: [IP4/6 <USER1>
SOME/MAILBOX import:0/0] (doveadm-server) />//>/? at server2 paired with a file like ?
/>//>/-rw------- 1 vmail dovecot uarch 0 Apr 3 16:52
/home/to/USER1/.dovecot-sync.lock />//>/Corresponding logfile entries at server2 are like ?
/>//>/Apr 3 17:10:49 <mail.err> server2.lan dovecot: doveadm: Error: Couldn't
lock /home/to/USER1/.dovecot-sync.lock: \
/>/fcntl(/home/to/USER1/.dovecot-sync.lock, write-lock, F_SETLKW) locking
failed: Timed out after 30 seconds \ />/(WRITE lock held by pid 51110)
/>//>/[1] Even stopping dovecot will not end those processes. One has to
manually kill those before restarting dovecot. />//>/After one day of testing
2.3.1 with a couple of those episodes of
locking/timeout, and now missing mails depending with server your MUA
will connect to, I went back to 2.2.35. After two days at that version I
never had such an episode again. />//>>/It's not just you. This issue hit me recently, and it was impacting />>/replication noticeably. I am following git
master-2.3 . />/[...] />>/There is also a second issue of a long standing race with replication />>/occurring somewhere whereby if a mail comes in, is
written to disk, is />>/replicated and then deleted in short succession, it will reappear />>/again to the MUA. I suspect the mail is being replicated back
from />>/the remote. A few people have reported it over the years but it's not />>/reliable or consistent, so it has never been fixed. />>/And lastly
there has been an ongoing but seemingly minor issue />>/relating to locking timing out after 30s particularly on the remote />>/host that is being replicated
to. I rarely see the problem on my />>/local disk where almost all of the mail comes in, it's almost always />>/occurring on the replicate/remote system.
/>//>/It might be time to describe our setups in order to possibly find co
mmon
grounds that might trigger this issue you describe and Rimko and myself
ran into as well. />//>/Servers: Cloud Instances (both identical), around 25ms latency apart.
/>/Intel Core Processor (Haswell, no TSX) (3092.91-MHz K8-class CPU) />/Both servers are
connected via IPsec/racoon tunnels />/OS: FreeBSD 11.1-STABLE (both servers) />/Filesystem: ZFS
/>/MTA: postfix 3.4-20180401 (postfix delivers via dovecot's LMTP) />/IMAP: dovecot running in
FreeBSD jails (issues with 2.3.1, fine with
2.2.35) />/Replication: unsecured tcp / master-master />/MUA: mainly iOS or
macOS mail.app, rarely roundcube /
For me:
Servers: Main: VM on a VMWare ESXi local system (light
load), local SSD disks (no NFS)
Redundant: Linode VM in Singapore, around 250ms away
Also no NFS. Linode use SSDs for IO.
There is native IPv6 connectivity between both VMs.
As I am using TCPs I don't have a VPN between them -
just raw IPv6 end to end.
OS: Gentoo Linux x86_64 kept well up to date
Filesystem: EXT4 for both
MTA: Postfix 3.4-x (same as you)
IMAP: Dovecot running natively on the machine (no jail/chroot)
Replication: Secured TCP / master-master (but only one master is
actively used for SMTP and MUA access)
MUA: Thunderbird, Maildroid, MS Mail, Gmail client,
Roundcube, LG Mail client on handset etc
/I believe it is worthwhile to mention here that I run a poor man's
fail-over approach (round-robin DNS) as follows: />//>/DNS: mail.server.tld
resolves to one IP4 and one IP6 address of each
server, thus 4 IP addresses in total /
For me I have a simple pair of servers that replicate mail to each
other. Clients connect to the main server only, which is where mail
comes in. The second one that experiences the problem with locking is
only a redundant server which is a secondary MX, that only gets
occasional SMTP deliveries from time to time. So the amount of
replication back from the "secondary" is very minimal; the vast bulk of
the replication is the primary replicating changes out.
Reuben
