将消息从本地经纪人传递到不连贯的中央经纪人

Question

I have a specific requirement where i need to send message to a server which won't always be available.

For this i used a network of brokers, specific to ActiveMQ.

The goal is to have a local application A (producer only) which will push message to another central application B (consumer only). However network won't always be available. So application's A broker have to store messages and wait for connection before it can send message to application B. SO basically A is a proxy which need to forward message to B when it is available

Broker's B configuration includes a durable topic which is listening on in order to consume message.

As said in ActiveMQ's documentation i have to use a static network bridge to do that, which is what i did.

Note : i can't have B subscribe to A, because there will be multiple instance of A and i can't configure all of them in B.

So here is my configuration (raw spring) for local application :

<!--As said in http://activemq.apache.org/spring-support.html use 
    a pooled conntection along with JMSTemplate -->
 <amq:connectionFactory id="jmsFactory" brokerURL="${jms.broker.local.url}" />
<!--SpringJMSTemplate -->
<bean id="myJmsTemplate" class="org.springframework.jms.core.JmsTemplate">
    <property name="connectionFactory" ref="jmsFactory" />
</bean>
<!-- local broker with embedded -->
<bean id="localbroker" class="org.apache.activemq.broker.BrokerService"
    init-method="start" destroy-method="stop">
    <property name="brokerName" value="localBroker" />
    <property name="transportConnectorURIs">
        <list>
            <value>${jms.broker.local.url}</value>
        </list>
    </property>
    <property name="networkConnectors">
        <list>
            <ref bean="networkConnector" />
        </list>
    </property>
</bean>

<amq:connectionFactory id="remoteJmsFactory"
    brokerURL="${jms.broker.remote.url}" clientIDPrefix="BRIDGED-TEST" />

<bean id="networkConnector" class="org.apache.activemq.network.DiscoveryNetworkConnector">
    <property name="uri" value="static:(${jms.broker.remote.url})"></property>
    <property name="staticallyIncludedDestinations">
        <list>
            <bean class="org.apache.activemq.command.ActiveMQTopic">
                <constructor-arg type="java.lang.String" value="${jms.topic.sample}"/>
            </bean>
        </list>
    </property>
    <property name="staticBridge" value="true"></property><!-- will deliver content even if no consumer, usefull for durable topic only -->
</bean>

The localbroker is an embedded broker connecting to a remote broker (the application you can download from apacheMQ page).

Here is the central configuration

<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="locations">
        <value>file:${activemq.conf}/credentials.properties</value>
    </property>
</bean>


<bean id="logQuery" class="io.fabric8.insight.log.log4j.Log4jLogQuery"
      lazy-init="false" scope="singleton"
      init-method="start" destroy-method="stop">
</bean>

<broker xmlns="http://activemq.apache.org/schema/core" brokerName="localhost" dataDirectory="${activemq.data}" useVirtualDestSubs="true">

    <destinationPolicy>
        <policyMap>
          <policyEntries>
            <policyEntry topic=">" >
              <pendingMessageLimitStrategy>
                <constantPendingMessageLimitStrategy limit="1000"/>
              </pendingMessageLimitStrategy>
            </policyEntry>
          </policyEntries>
        </policyMap>
    </destinationPolicy>
    <managementContext>
        <managementContext createConnector="false"/>
    </managementContext>
    <persistenceAdapter>
        <kahaDB directory="${activemq.data}/kahadb"/>
    </persistenceAdapter>
      <systemUsage>
        <systemUsage>
            <memoryUsage>
                <memoryUsage percentOfJvmHeap="70" />
            </memoryUsage>
            <storeUsage>
                <storeUsage limit="100 gb"/>
            </storeUsage>
            <tempUsage>
                <tempUsage limit="50 gb"/>
            </tempUsage>
        </systemUsage>
    </systemUsage>
    <transportConnectors>
        <transportConnector name="http" uri="http://0.0.0.0:61612?maximumConnections=1000&amp;wireFormat.maxFrameSize=10485760"/>
    </transportConnectors>
    <shutdownHooks>
        <bean xmlns="http://www.springframework.org/schema/beans" class="org.apache.activemq.hooks.SpringContextHook" />
    </shutdownHooks>

</broker>
<import resource="jetty.xml"/>

So what is happening when i try to send/receive messages :

• If the producer (A) is connected and consumer (B) is connected to their respective broker, and the broker are connected together it works fine.
• If the consumer (B) is connected to his broker and there is message pending, while producer A's broker is disconnected, it works fine.
• If the producer (A) is disconnected from network, A's broker won't deliver the message to B's broker when B is available again.

Before network connectors i tried jmsbridgeConnector using outboundTopicBridge in local broker configuration without any luck.

Here is the question : how do i get local's broker A send message to central's broker B on reconnect. And while it is not available, be sure that he won't lost any message.

Note :

• The network which i work on is not alaways available (can be for days !), and i can rely only on http port, this is why it is the only one openned. This means that no multicast discovery is possible.
• Message must be deliver only once.
• The reason why i use local broker is to not manage what i have to send myself. They're only, at the moment, used to store and forward to the central.

EDIT : i have been able to make it working using a JMS Bridge, however i have a last problem, if the connection os lost at application booting or during application lifecycle, i need to restart my broker to be able to send messages.

Answer 1

I've been using this "store and forward" pattern with success using bridge.

I can not comment for network connector but for bridge, you have to :

• use a recent version of jmeter due to Bug AMQ-5859
• add a org.apache.activemq.network.jms.ReconnectionPolicy on the bridge
• make sure you set the reconnectOnException on the remote broker connection factory

Answer 2

I have try all the way around and can't get it works using only configuration so i end up doing that myself :

<jms:listener-container container-type="default" factory-id="proxyFactory"
    acknowledge="transacted" destination-type="topic" connection-factory="jmsFactory">

<bean id="remoteJmsTemplate" class="org.springframework.jms.core.JmsTemplate">
    <property name="connectionFactory" ref="remoteJmsFactory" />
    <property name="pubSubDomain" value="true"/>
</bean>
<bean id="simpleMessageProxyListener"
    class="com.xxx.jms.test.SimpleMessageProxyListener">
    <property name="jmsTemplate" ref="remoteJmsTemplate" />
    <property name="queueName" value="${jms.topic.sample}" />
</bean>

Basically i just have a class that subscribe to the local broker with a durable subscription, and send message to the remote, if it fails, session is rollbacked.

That simple proxy rely on Spring Listener's container, so it may be ably to work even if he listen on a remote broker, in my case, it's listening on a local embedded broker, so i won't have any problem.

If someone else have a only-configuration answer that works when stopping/starting the remote broker while local application live and don't need a restart to send the messages, feel free to post it, i will upvote and check.

Note : you must set jms.redeliveryPolicy.maximumDeliveries to -1 to have it working.