Replication issues master <-> master nfs backend

[William L. Thomson Jr.]

I keep having some replication issues and not sure what can be done to resolve or correct. It 
does not seem to happen all the time, though for the last ~30 or so minutes and many 
messages seems to be happening consistent for me.

I have 2 mail servers, basically clones, and thus master master replication. Most of the time 
things work fine. But many times an email or several will arrive on one, and never replicate 
to the other. I am not as concerned on the never replicating, as I am that the user never gets 
notified.

Mail arrives on say server 1, users are checking mail on server 2, and they never see the email 
on server 2. This is not always the case, but its happening enough daily. I then log into one 
and run sync manually. Which usually syncs the mail on both servers, and then it arrives in 
the inbox.

Here is an example, mail is on mail2, but not mail1. I am checking email on mail1 so I am not 
seeing the 1 email.

Mail1
/home/wlt-ml/.maildir/new:
total 0

Mail2
/home/wlt-ml/.maildir/new:
total 12
-rw------- 1 wlt-ml site1 8502 Mar 22 14:57 1458673024.7643.mail2

Then I manually log into mail2 and run this command, though usually I can run it from either 
side, and just change the name to the other server.

doveadm sync -u "*" remote:mail1

And then I end up with the missing email on mail1, and it arrives in my email client shortly 
there after

Mail1
/home/wlt-ml/.maildir/new:
total 12
-rw------- 1 wlt-ml site1 8502 Mar 22 14:57 
1458673051.M838843P26735.mail1,S=8502,W=8678:2,T

I have no idea why it does this. It seems to happen when when a full sync has taken place 
per doveadm replicator status wlt-ml. There does not seem to be any settings to force a full 
vs fast sync more often. No clue if this is even a full vs fast issue or other.

I think it tends to happen more when people stay connected to the imap server. I had a 
theory that closing the email client and opening it again will get dovecot to sync. I believe 
this is still the case, but not able to confirm 100%. Also users are reporting closing 
Thunderbird. I can see them logging out and back in in the logs, but email does not replicate 
or show till I run doveadm sync manually.

Tempted to have cron invoke that on the regular, but seems very hackish and likely will have 
its own issues doing that. Since its not the right way or how things were designed. Not sure 
if this is a bug or what. Hopefully miss-configuration on my end.

Open to any feedback, advice, etc. I can provide replicator configuration but its pretty 
straight forward and mostly copy/paste from the replication page. Replication works, just 
seems it is not triggered to replicate at times or something.

dovecot --version 
2.2.22 (fe789d2)


-- 
William L. Thomson Jr.
Obsidian-Studios, Inc.
http://www.obsidian-studios.com