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From Oleg Kiorsak <kior...@gmail.com>
Subject Re: what about Slave failing in "Pure-Master Slave" setup?
Date Fri, 18 Jun 2010 13:48:49 GMT


Thanks Garry

RE:
>should just ignore the slave if any replication attempt fails.

exactly!


the current way it works is that it provides "continuity" only when MASTER
fails in the pair, but not when
SLAVE fails (from what you describe it is the case when SYNC(ACKed) send is
used, but this is most common one)

I will look into creating a JIRA...

(my "use case" would be that SLAVE can just as equaly be the first one to
fail as MASTER! ;)


as far as the more sophisticated clustering with "shared storage" vs "pure
(aka shared nothing)"

I encountered a problem just yesterday that upon googling turned out to be a
known bug
https://issues.apache.org/activemq/browse/AMQ-2672

and the concern that it raises is whether a "storage" can get corrupted (is
it whats causein the "AMQ-2672"?)
so I thought a benefit of "pure" M/S would be that there is a redundancy
(two copies of persisted data)
??


cheers,
O.K.





Gary Tully wrote:
> 
> This is true, pure master slave is asymmetrical and it requires manual
> intervention to restore the paring once the master fails. There is an
> option
> on the broker to have the master shutdown if the slave fails, but this is
> off by default. The problem is that there is currently no way to have a
> slave connect and play catch up with an already running and active master.
> 
> Most folk use the shared data store fault tolerant strategy. where N
> brokers
> can share a data store (shared file system or jdbc) and one broker gains
> an
> exclusive lock and becomes active. the rest become passive slaves.
> 
> (That said, from looking at the code, the master will carry on (without
> the
> slave) if it fails to replicate an async command but does not stop
> replication on the failure of a  sync command, which is a little bogus. It
> should just ignore the slave if any replication attempt fails. If you have
> a
> use case for pure master slave, please open a jira issue so we can ensure
> a
> master can carry on in the event of a slave failure)
> 
> 
> On 18 June 2010 14:10, Oleg Kiorsak <kiorsak@gmail.com> wrote:
> 
>>
>>
>> One of the benefits of Pure Master Slave are that supposedly it provides
>> some "HA" -
>> namely books, tutorials, wiki site describe that "when MASTER fails
>> SLAVE"
>> becomes a MASTER
>> and clients are smoothly reconnected to it via the virtue of "failover
>> transport"...
>>
>> That is all nice and good, and TRUE (I tested it)
>>
>> But the question arises - what if its the SLAVE one that fails (as it is
>> a
>> 50/50 chance)...
>>
>> In my testing (when I "kill -KILL") the SLAVE's process the end result is
>> that MASTER just stops accepting any connections and even the queues even
>> disappear from JMX jConsole....
>>
>> only the restart of both restores "status quo"... but restart is
>> something
>> that has to be done manually...
>>
>>
>> so as far as "HA" the solution seems to be asymmetrical - is is only an
>> "HA"
>> when it is the MASTER that fails first...
>>
>> Am I missing something?
>>
>> ???
>>
>> Is there maybe some way to configure it so that MASTER continues to
>> work...
>> alone (just as the SLAVE would if MASTER failed)...
>> ??
>>
>>
>> cheers,
>> O.K.
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> --
>> View this message in context:
>> http://old.nabble.com/what-about-Slave-failing-in-%22Pure-Master-Slave%22-setup--tp28925866p28925866.html
>> Sent from the ActiveMQ - User mailing list archive at Nabble.com.
>>
>>
> 
> 
> -- 
> http://blog.garytully.com
> 
> Open Source Integration
> http://fusesource.com
> 
> 

-- 
View this message in context: http://old.nabble.com/what-about-Slave-failing-in-%22Pure-Master-Slave%22-setup--tp28925866p28926308.html
Sent from the ActiveMQ - User mailing list archive at Nabble.com.


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