On 5/16/06, William Blackburn <[EMAIL PROTECTED]> wrote:
Guillaume,
Thank you for your quick reply. Sorry to be so dense, but I just want
to confirm my understanding of what you've said:
If I configure jms flow only with activemq journaled db persistence,
I would get recovery of message-exchanges that were 'in-flight' at
the time of a server crash, but I would NOT get exchanges that had
already hit a particular component, correct?
Exactly.
If I configure jca flow, I will, in addition to above, be able to get
exchanges that were in the middle being processed by a component at
the time of the crash, yes? Is this automatic, or must my components
commit or rollback the transaction? Given that I am using extensions
of servicemix' ComponentSupport, how would I get access to the
transaction to do so?
The JCA flow uses jca ;)
So each time a jms message is received, a transaction is started and
the message consumption is part of the xa transaction. The
transaction will be automatically commited, unless the setRollbackOnly
has been called on the transaction.
You can do that by using the
((TransactionManager) ComponentContext.getTransactionManager).getTransaction()
or
(Transaction)
exchange.getProperty(MessageExchange.JTA_TRANSACTION_PROPERTY_NAME)
Remarks:
* the jca flow does not handle sendSync because the message has to
be enlisted in a transaction so you may experience problems with
components using sendSync (note that you can also configure multiple
flows)
* you can set the autoEnlistInTransaction attribute on the jbi
container to true so that all jbi exchanges will automatically be part
of a transaction
* you should also set the persistent attribute on the jbi container
to true else jms messages will be sent using jms
DeliveryMode.NON_PERSISTENT
Cheers,
Guillaume Nodet
Thanks again for all your help.
BJ
On May 16, 2006, at 11:47 AM, Guillaume Nodet wrote:
> On 5/16/06, William Blackburn <[EMAIL PROTECTED]> wrote:
>> I will be moving from a single deployment, SEDA flow to a cluster
>> using the JMSflow. I've run the cluster example and studied up on
>> ActiveMQ, My goal is as much fault tolerance as load handling,
>> Configuring ActiveMQ's journaled db persistence will get me most of
>> the way (I think), but I still have two remaining questions.
>>
>> First, in the MQ sense, when is an message-exchange considered
>> 'delivered' ? For example, if I have a bunch of servicemix components
>> running on a node configured as above, and I yank the power while a
>> component is in the middle of an 'onMessageExchange()' what happens
>> to that message? Will ActiveMQ redeliver it when the node comes back
>> up? Can components influence what ActiveMQ considers 'delivered' in
>> any way.
>
> To be able to use redelivery, the flow should be able to use
> acknowledgements, jms transactions or xa transactions. Currenly there
> is no callback to be able to use client acks or jms transaction, so
> you will have to use xa transactions. Note that there is no real
> overhead if the jms resource is the only one enlisted in the xa
> transactions. The JCA flow provides high performance concurrent
> delivery using. The configuration is the same than for the jms flow.
>
>>
>> My second question is probably more an ActiveMQ one, but I hope you
>> can comment anyway. We will be using a redundant database-server as
>> well. Should the ActiveMQ brokers be configured to use the same
>> database? Or should each have its own database?
>
> You should either use master / slave, or have a shared database if you
> want high availability, else messages kept by a broker are not
> available to other brokers, so if this one fails, the message will be
> lost.
>
> Cheers,
> Guillaume Nodet
>>
>> Thanks very much in advance for any help.
>>
>> B.J.
>>
>
>
> --
> Cheers,
> Guillaume Nodet
--
Cheers,
Guillaume Nodet
