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From:Marcus Bointon Date:May 14 2009 8:37am
Subject:Re: advice on master-master replication failover support
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Carl wrote:

>> 1) multiple app servers sharing the same
>> MySQL master-master backend


This is exactly the situation I'm using mmm in. I have a master-master  
pair (no slaves) and 8 app servers.

On 13 May 2009, at 21:25, Rick James wrote:

> * "Automatic" is not possible.

Well, it's working with mmm for me.

> * Need to monitor for failure, then be able to double check that it  
> is not a false alarm.

mmm monitors by connecting to back-ends and running queries. This  
works, but we've had some problems with false alarms when queries are  
held up by long-running (> 1 hour) transactions, or if a server is  
iowait saturated.

> * DNS for redirecting traffic --> can take many minutes (TTL +  
> caching)

I agree, this is not much use for DBs.

> * Port (3306) forwarding -- a significant possibility

This is effectively what mmm does - it accepts connections on a  
floating IP and forwards to the appropriate back-end.

> * Software or hardware load balancing, such that the passive master  
> appears to be "not available" -- a significant possibility.  Change  
> the health check after establishing it as the read-write master.

The monitoring needs to be pretty intimate with the back-ends if it's  
not going to give false alarms - simple ping or connect tests are not  
enough; you need to select databases and run queries.

> * Different port or different logical host name -- helpful in  
> segregating readonly connects versus read-write connects.


Again, mmm does this - you can use a separate IP for each role, and  
have any number of back-ends supporting each.

I can't comment on the redundant networking aspect as I've not tried  
that, but I would expect that this to be dealt with separately at a  
lower level.

Marcus
-- 
Marcus Bointon
Synchromedia Limited: Creators of http://www.smartmessages.net/
UK resellers of info@hand CRM solutions
marcus@stripped | http://www.synchromedia.co.uk/


Thread
advice on master-master replication failover supportCarl Marcinik13 May
  • RE: advice on master-master replication failover supportRick James13 May
    • Re: advice on master-master replication failover supportMarcus Bointon14 May
      • RE: advice on master-master replication failover supportRick James15 May
Re: advice on master-master replication failover supportCM14 May
Re: advice on master-master replication failover supportCM14 May
Re: advice on master-master replication failover supportCM14 May
Re: advice on master-master replication failover supportCM14 May
Re: advice on master-master replication failover supportCM14 May
Re: advice on master-master replication failover supportCM14 May