i have a network of 2 brokers, let's call them "Remote" and "Central", running
on ActiveMQ 5.0.3, in a store-and-forward configuration. i inherited this
setup, i did not design it, but it seems like a generally solid configuration.
On the Remote broker, there are topics (e.g. "org.nwea.topics.license") that
have durable subscriptions to topics of the same name on the Central broker.
Messages that are published to topics on the Central broker find their way to
Remote really fast - as long as the Remote is online when the message is
published. Messages that are published when Remote is offline are never picked
up by the remote.
i have a j2ee application that contains MDBs that are annotated to have durable
subscriptions to the topics on the Remote broker.
The NetworkConnector configuration in the Remote broker's activemq.xml looks
like this:
<networkConnectors>
<networkConnector name="${ApplianceID}"
userName="${networkConnectorUserName}"
password="${networkConnectorPassword}"
uri="static://(ssl://${Central.ServerHostname}:${central_sslPortNumber})"
duplex="true"
dynamicOnly="true">
<dynamicallyIncludedDestinations>
<queue physicalName="org.nwea.queues.central.>"/>
<topic physicalName="org.nwea.topics.>"/>
</dynamicallyIncludedDestinations>
<staticallyIncludedDestinations>
<queue physicalName="org.nwea.queues.central.>"/>
<topic physicalName="org.nwea.topics.>"/>
</staticallyIncludedDestinations>
</networkConnector>
</networkConnectors>
In reading through the book "ActiveMQ in Action" and reviewing the online docs
at http://activemq.apache.org/networks-of-brokers.html, it seems that we should
use the default setting for "dynamicOnly", "false" (the docs say "if true, only
forward messages if a consumer is active on the connected broker").
However, when i set "dynamicOnly" to false, i see numerous startup errors and
NullPointerExceptions in the Remote activemq.log, and connection errors in
Central's logs. The Remote log simply reads:
[DemandForwardingBridge.serviceLocalException]: Network connection between
vm://remotebroker.msg02.nweacolo.pvt#24 and
ssl://msg01.se.nweacolo.pvt/192.168.1.94:51617 shutdown due to a local error:
java.lang.NullPointerException
With "dynamicOnly" set to true, the log shows that existing durable
subscriptions are reconnecting during startup.
Playing with the "prefetchSize" and "networkTTL" attributes for
<networkConnector> on Remote (vaguely recommended in the docs) doesn't seem to
have any effect.
This seems very similar to this issue from February 2009:
http://old.nabble.com/Confusion-about-dynamicOnly-NetworkConnector-property-td22211600.html,
which didn't seem to get resolved.
Any insight, recommendations, or help are most appreciated.
--
Joe Niski
IS Development | NWEA
NWEA.ORG<3D%22http://www.nwea.org/%22> | Partnering to Help All Kids Learn
