Update to Murder docs (D69) and question on style.

[Michael Menge]

Hi,

Quoting Nic Bernstein <nic at onlight.com>:

> On 08/21/2015 02:58 AM, Michael Menge wrote:
>> Hi,
>>
>>
>> Quoting Nic Bernstein <nic at onlight.com>:
>> <snip>
>>> I can write this up, I just wasn't sure if it was still needed.  I  
>>> put a big ol' Note: in the replication page saying:
>>>
>>>   Important
>>>
>>>   Within a Cyrus /Murder/
>>> <https://docs.cyrus.foundation/imap/developer/architecture.html#architecture-murder>
>>>   environment, replicas must *not* be configured to invoke
>>>   ctl_mboxlist(8)
>>> <http://docs.cyrus.foundation/imap/admin/commands/ctl_mboxlist.html>
>>>   on startup (pushing the local mailbox list to the *Mupdate Master*).
>>>   This may only be done on the Master instance.
>>>
>>> That's the only real gotcha I know of, but, having said that, I  
>>> did write up a brief set of instructions about this very topic not  
>>> that long ago (IIRC) for user mailing list.  I figured I could  
>>> start with that.
>>>
>>
>>
>> For the initial configuration I second this. But there are IHMO things
>> to consider on failover.
>>
>>
>> 1. ctl_mboxlist must be used with -m and -a Option on failover
>> 2. on big installations updating all entries in mailbox.db on the
>>   mupdate server can take some time, on our setup we switch the IP address
>>   of master and replic on failover
>
> And on 21 August at 06:12AM CDT, Ken Murchison wrote:
>> Right.  We don't even have our replicas as part of our Murder.   
>> They replicate their backend as if it were a standalone server.
>
>
> So the replica has no clue about the Murder.  We switch DNS between  
> the two hosts during failover, so no IP address change [the servers  
> are in different data centers, so that wouldn't be practical in any  
> event].  I doubt we actually need that last blob of stuff on the  
> replica, but it doesn't seem to have hurt.
>
> As for /etc/cyrus.conf, we do something similar, in regards to  
> commenting/uncommenting START entries for ctl_mboxlist and  
> sync_client, versus an SERVICES entry for sync_server.
>
> It's not the cleanest process in failover, but a damn sight better  
> than nothing.

I should have been more clearer in the fist place.

We change the IP and servername: in imapd.conf on the new master to  
the  value of the old master
so that there is no changes in the mailbox.db.

The advantage of changing the dns is you don't have to worry about  
duplicate IPs after a split brain,
but you have to make sure that the dns lookup is not cached.


@main devs

how do you plan to integrate mupdate and replication? I hope that it  
will not need to rewrite all
entries in mailbox.db on failover.

Regards

     Michael





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