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From Norbert Pfistner <>
Subject Re: Master/Slave: Slave Failed, async error occurred
Date Wed, 29 Jul 2009 15:27:05 GMT
We also plan to use master/slave.

The 'waitForSlave' seems a bit strange for me, since our main reason for 
adding some slaves is to avoid a single point of failure (i.e. the 
master). But what if the slave fails? Does the required 'waitForSlave' 
mean that we can't run a master without his slaves? Doesn't this even 
increase the risk of failure?

In an ideal world i would expect that using master slave would meen 
simply start a borker (first will be the master), add any slaves you 
want (which should be configured by the clients) any time later and 
beeing able to indipendly start/stop/crash one of them: The whole 
messaging system should remain stable as long at least one broker is up.

Is this possible with activeMQ? Which version should we use (currently 
we use 5.2, not yet in Master/Slave, JDBC persistance).

Are there any special settings we need to set to achieve the goal 
discribed above?


brendanr schrieb:
> Thank you for your reply.
> I know about the 'waitForSlave' attribute, but it is not really what I need.
> I would like to be able to add a backup machine (and hence a slave broker)
> at some later time, without having to restart the master broker and all the
> producer/consumer connections to it. I would have expected that when a slave
> connected that it could learn about all messages/producers/consumers
> connected to the master, and continue operating correctly.
> But from what you are saying, this is not possible? Will it be available
> when the Kaha DB feature is available?
> Many thanks again. 
> Gary Tully wrote:
>> the brokers need to be in sync from the start. there is a waitForSlave
>> attribute that can force the master to stall till the slave connects. see:
>> 2009/7/29 brendanr <>
>>> Hi,
>>> I am having an issue with a simple master/slave setup. My master is
>>> running
>>> on one machine (, and my slave is running on a separate
>>> machine ( Attached are the config files for both master and
>>> slave, and the log files for master and slave. I am running broker
>>> version
>>> 5.2.0 and using activemq CPP library 3.0.1. My producer and consumers are
>>> using the supplied sample code.
>>> On the master broker I get an exception saying the following:
>>> ERROR MasterBroker                   - Slave Failed: ...
>>> On the slave broker I get an exception daying teh following:
>>> ERROR Service                        - Async error occurred: ...
>>> Please see attached log files for complete exceptions.
>>> I can easily reproduce the errors under the following conditions:
>>> 1. Start the master broker
>>> 2. Start a producer that connects to the master broker and sends 10
>>> messages
>>> to queue TEST.FOO. Producer disconnects.
>>> 3. Start the slave broker. It connects to teh master broker successfully.
>>> 3. Start a consumer that connects to the master broker. It will retrieve
>>> the
>>> messages successfuly, but will cause the exceptions on both brokers.
>>> It doesn't matter if the producer and consumer connect to the broker
>>> using
>>> the failover mechanism (using 2 addresses) or not.
>>> If I start both brokers first, before connecting any producers/consumers
>>> then I do not get the exceptions, but in the application I would like to
>>> use
>>> activemq in, it is not unreasonable that the master broker will have some
>>> activity before the slave broker is ready to connect.
>>> Should activemq work the way I would like it to work, and if so what am I
>>> doing wrong? Any help would be much appreciated.
>>> Thanks
>>> Brendan
>>> activemq-slave.log
>>> activemq-slave.xml
>>> --
>>> View this message in context:
>>> Sent from the ActiveMQ - User mailing list archive at
>> -- 
>> Open Source Integration


Dipl.-Ing. Norbert Pfistner

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