Host ... is being updated before previous update had finished

[Mark Moseley]

Timo/Aki/Docecot guys, any hints here? Is this a bug? Design issue?

On Fri, Apr 7, 2017 at 10:10 AM Mark Moseley <moseleymark at gmail.com> wrote:

> On Mon, Apr 3, 2017 at 6:04 PM, Mark Moseley <moseleymark at gmail.com>
> wrote:
>
>> We just had a bunch of backend boxes go down due to a DDoS in our
>> director cluster. When the DDoS died down, our director ring was a mess.
>>
>> Each box had thousands (and hundreds per second, which is a bit much) of
>> log lines like the following:
>>
>> Apr 03 19:59:29 director: Warning: director(10.1.20.10:9090/left): Host
>> 10.1.17.15 is being updated before previous update had finished (up ->
>> down) - setting to state=down vhosts=100
>> Apr 03 19:59:29 director: Warning: director(10.1.20.10:9090/left): Host
>> 10.1.17.15 is being updated before previous update had finished (down ->
>> up) - setting to state=up vhosts=100
>> Apr 03 19:59:29 director: Warning: director(10.1.20.10:9090/left): Host
>> 10.1.17.15 is being updated before previous update had finished (up ->
>> down) - setting to state=down vhosts=100
>> Apr 03 19:59:29 director: Warning: director(10.1.20.10:9090/left): Host
>> 10.1.17.15 is being updated before previous update had finished (down ->
>> up) - setting to state=up vhosts=100
>> Apr 03 19:59:29 director: Warning: director(10.1.20.10:9090/left): Host
>> 10.1.17.15 is being updated before previous update had finished (up ->
>> down) - setting to state=down vhosts=100
>> Apr 03 19:59:29 director: Warning: director(10.1.20.2:9090/right): Host
>> 10.1.17.15 is being updated before previous update had finished (down ->
>> up) - setting to state=up vhosts=100
>> Apr 03 19:59:29 director: Warning: director(10.1.20.2:9090/right): Host
>> 10.1.17.15 is being updated before previous update had finished (up ->
>> down) - setting to state=down vhosts=100
>> Apr 03 19:59:29 director: Warning: director(10.1.20.2:9090/right): Host
>> 10.1.17.15 is being updated before previous update had finished (down ->
>> up) - setting to state=up vhosts=100
>> Apr 03 19:59:29 director: Warning: director(10.1.20.2:9090/right): Host
>> 10.1.17.15 is being updated before previous update had finished (up ->
>> down) - setting to state=down vhosts=100
>> Apr 03 19:59:29 director: Warning: director(10.1.20.2:9090/right): Host
>> 10.1.17.15 is being updated before previous update had finished (down ->
>> up) - setting to state=up vhosts=100
>>
>> This was on every director box and the status of all of the directors in
>> 'doveadm director ring status' was 'handshaking'.
>>
>> Here's a sample packet between directors:
>>
>> 19:51:23.552280 IP 10.1.20.10.56670 > 10.1.20.1.9090: Flags [P.], seq
>> 4147:5128, ack 0, win 0, options [nop,nop,TS val 1373505883 ecr
>> 1721203906], length 981
>>
>> Q.      [f.|.HOST       10.1.20.10      9090    1006732 10.1.17.15
>>  100             D1491260800
>> HOST    10.1.20.10      9090    1006733 10.1.17.15      100
>> U1491260800
>> HOST    10.1.20.10      9090    1006734 10.1.17.15      100
>> D1491260800
>> HOST    10.1.20.10      9090    1006735 10.1.17.15      100
>> U1491260800
>> HOST    10.1.20.10      9090    1006736 10.1.17.15      100
>> D1491260800
>> HOST    10.1.20.10      9090    1006737 10.1.17.15      100
>> U1491260800
>> HOST    10.1.20.10      9090    1006738 10.1.17.15      100
>> D1491260800
>> HOST    10.1.20.10      9090    1006739 10.1.17.15      100
>> U1491260800
>> HOST    10.1.20.10      9090    1006740 10.1.17.15      100
>> D1491260800
>> HOST    10.1.20.10      9090    1006741 10.1.17.15      100
>> U1491260800
>> HOST    10.1.20.10      9090    1006742 10.1.17.15      100
>> D1491260800
>> HOST    10.1.20.10      9090    1006743 10.1.17.15      100
>> U1491260800
>> HOST    10.1.20.10      9090    1006744 10.1.17.15      100
>> D1491260800
>> HOST    10.1.20.10      9090    1006745 10.1.17.15      100
>> U1491260800
>> HOST    10.1.20.10      9090    1006746 10.1.17.15      100
>> D1491260800
>> HOST    10.1.20.10      9090    1006747 10.1.17.15      100
>> U1491260800
>> SYNC    10.1.20.10      9090    1011840 7       1491263483      3377546382
>>
>> I'm guessing that D1491260800 is the user hash (with D for down), and the
>> U version is for 'up'.
>>
>> I'm happy to provide the full tcpdump (and/or doveconf -a), though the
>> tcpdump is basically all identical the one I pasted (same hash, same host).
>>
>> This seems pretty fragile. There should be some sort of tie break for
>> that, instead of bringing the entire cluster to its knees. Or just drop the
>> backend host completely. Or something, anything besides hosing things
>> pretty badly.
>>
>> This is 2.2.27, on both the directors and backend. If the answer is
>> upgrade to 2.2.28, then I'll upgrade immediately. I see
>> commit a9ade104616bbb81c34cc6f8bfde5dab0571afac mentions the same error but
>> the commit predates 2.2.27 by a month and a half.
>>
>> In the meantime, is there any doveadm command I could've done to fix
>> this? I tried removing the host (doveadm director remove 10.1.17.15) but
>> that didn't do anything. I didn't think to try to flush the mapping for
>> that user till just now. I suspect that with the ring unsync'd, flushing
>> the user wouldn't have helped.
>>
>> The only remedy was to kill dovecot on every box in the director cluster
>> and then (with dovecot down on *all* of them) start dovecot back up.
>> Restarting each director's dovecot (with other directors' dovecots still
>> running) did nothing. Only by brining the entire cluster down did dovecot
>> stop furiously logging "Host ... is being updated before previous update
>> had finished" on every director host.
>>
>> Any advice is most welcome.
>>
>
>
> Dovecot guys,
>
> Any thing I can do to fix this? Any thoughts on that error in general?
>
>