You are viewing a plain text version of this content. The canonical link for it is here.
Posted to users@activemq.apache.org by colonelx <za...@zacburke.com> on 2009/06/29 11:43:19 UTC
JDBC Master Slave Question
Hi,
I have 2 brokers setup in a JDBC Master Slave Configuration.
Each broker is on a different machine. BoxA and BoxB
The database is also on a different machine BoxC. (mysql 5.1)
The failover is working fine when I manually kill any instance of ActiveMQ
on BoxA or BoxB. (Ctrl-C)
However, can anyone tell me what will happen if the if the Master instance
looses its network connection ?
Will its lock on the database get dropped immediately ? or will it still
hold a (now invalid) lock on the database ?
I ask this, because if this happens , there could possibly be a condition
where the slave won't ever be able to get a lock on the database because the
master has lock which did not get correctly released and manual intervention
would be needed in order to fix up the problem.
I know that I could test this by plugging in and out the physical network
connections, but I'm not really in a position to do this on any of the above
boxes.
Thanks.
--
View this message in context: http://www.nabble.com/JDBC-Master-Slave-Question-tp24251198p24251198.html
Sent from the ActiveMQ - User mailing list archive at Nabble.com.
Re: JDBC Master Slave Question
Posted by colonelx <za...@zacburke.com>.
I got to try out the scenario I described above (ie) physically remove the
network cable from the Master.
Basically the database did not realize that the client had disconnected
abruptly,
and there was still a lock on the database table, (which was now an invalid
stale lock), and would
never get released.
After some further digging I realised that there was an issue raised about
this,
and also explains the exact behaviour I experienced.
https://issues.apache.org/activemq/browse/AMQ-1958
https://issues.apache.org/activemq/browse/AMQ-1958
I know that there's nothing that can be done really at the ActiveMQ level,
its more of a DB issue really.
I did look into maybe setting the tcp_keepalive to a low value which might
force the (invalid)connection
to close quicker at a TCP level, but I didn't want to mess around with stuff
like that at such a low level.
Any lock options at the DB level were specific to the amount of time you
wait until you get a lock,
not the amount of time you can hold onto it.
In the end I wrote a DB specific script which basically kills any sessions
for a particular IP, which in
turn releases the lock and the slave can kick in.
If anyone knows of a different (perhaps better) way of implementing this
please let us know.
Gary Tully wrote:
>
> You have got to ask the JDBC driver or database documentation. I imagine
> there is a lock expiry option that can be tweaked.
>
> 2009/6/29 colonelx <za...@zacburke.com>
>
>>
>> Hi,
>>
>> I have 2 brokers setup in a JDBC Master Slave Configuration.
>>
>> Each broker is on a different machine. BoxA and BoxB
>> The database is also on a different machine BoxC. (mysql 5.1)
>>
>> The failover is working fine when I manually kill any instance of
>> ActiveMQ
>> on BoxA or BoxB. (Ctrl-C)
>>
>> However, can anyone tell me what will happen if the if the Master
>> instance
>> looses its network connection ?
>> Will its lock on the database get dropped immediately ? or will it still
>> hold a (now invalid) lock on the database ?
>> I ask this, because if this happens , there could possibly be a condition
>> where the slave won't ever be able to get a lock on the database because
>> the
>> master has lock which did not get correctly released and manual
>> intervention
>> would be needed in order to fix up the problem.
>>
>> I know that I could test this by plugging in and out the physical network
>> connections, but I'm not really in a position to do this on any of the
>> above
>> boxes.
>>
>> Thanks.
>>
>> --
>> View this message in context:
>> http://www.nabble.com/JDBC-Master-Slave-Question-tp24251198p24251198.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://www.nabble.com/JDBC-Master-Slave-Question-tp24251198p24273534.html
Sent from the ActiveMQ - User mailing list archive at Nabble.com.
Re: JDBC Master Slave Question
Posted by Gary Tully <ga...@gmail.com>.
You have got to ask the JDBC driver or database documentation. I imagine
there is a lock expiry option that can be tweaked.
2009/6/29 colonelx <za...@zacburke.com>
>
> Hi,
>
> I have 2 brokers setup in a JDBC Master Slave Configuration.
>
> Each broker is on a different machine. BoxA and BoxB
> The database is also on a different machine BoxC. (mysql 5.1)
>
> The failover is working fine when I manually kill any instance of ActiveMQ
> on BoxA or BoxB. (Ctrl-C)
>
> However, can anyone tell me what will happen if the if the Master instance
> looses its network connection ?
> Will its lock on the database get dropped immediately ? or will it still
> hold a (now invalid) lock on the database ?
> I ask this, because if this happens , there could possibly be a condition
> where the slave won't ever be able to get a lock on the database because
> the
> master has lock which did not get correctly released and manual
> intervention
> would be needed in order to fix up the problem.
>
> I know that I could test this by plugging in and out the physical network
> connections, but I'm not really in a position to do this on any of the
> above
> boxes.
>
> Thanks.
>
> --
> View this message in context:
> http://www.nabble.com/JDBC-Master-Slave-Question-tp24251198p24251198.html
> Sent from the ActiveMQ - User mailing list archive at Nabble.com.
>
>
--
http://blog.garytully.com
Open Source Integration
http://fusesource.com
Re: JDBC Master Slave Question
Posted by Johan Stuyts <j....@zybber.nl>.
> I know that I could test this by plugging in and out the physical network
> connections, but I'm not really in a position to do this on any of the
> above
> boxes.
If you are on Windows you can use TCPView to kill connections without
having to physically disconnect the network:
<http://technet.microsoft.com/en-us/sysinternals/bb897437.aspx>
I'm sure there are similar tools for other platforms.
Regards,
Johan Stuyts