[EXT] doveadm backup from gmail with imapc

[Ben Mulvihill]

On Fri, 2020-04-10 at 15:13 +0300, Sami Ketola wrote:
> 
> > 
> > On 10 Apr 2020, at 14.07, Ben Mulvihill <ben.mulvihill at gmail.com>
> > wrote:
> > 
> > 
> last answer from gmail:
> 
> > 
> > 1586513176.126970 1944 OK Success
> 
> last commands send by dovecot:
> 
> > 
> > 1586513175.951965 1944 UID FETCH
> > 99624,99627,99628,99629,99631,99632,99633,99634,99635,99636,99637,9
> > 9639
> > ,99640,99641,99642,99643,99644,99645,99646,99647,99648 (X-GM-MSGID)
> > 1586513176.127109 1945 LIST "" "*"
> 
> So gmail hangs and never gives response to the last LIST command.
> 
> Fetcing  X-GM-MSGID is related to POP3 UIDLs. If you don't care about
> POP3 and gmail labels you can remove gmail-migration from
> imapc_features.
> 
> also you can try to set imapc_cmd_timeout to some low value like 10s
> to make dovecot to reconnect in case gmail hangs. Default is to wait
> for 5 mins.
> 
> Sami
> 
> 

Thanks again! 

I tried setting imapc_cmd_timeout = 10s and that was enough to take the
download process past the ID stage and on to downloading messages. 
doveadm still failed the same ASSERT and core dumps, just not so soon.
In four attempts  I downloaded 4200, 1800, 0 and 4200 
messages respectively. That was yesterday. I tried today and have
successfully downloaded a further 20000 messages without any core
dumps. I ended up interrupting the process myself because I was 
concerned at exceeding my ISPs fair usage limits. But by repeating
the command from time to time I should gradually be able to synchronise
the whole mailbox.

Ben