Versions Compared

Old Version 13

changes.mady.by.user Unknown User (acoburn)

Saved on

compared with

New Version 14

changes.mady.by.user Unknown User (acoburn)

Saved on

Key

  • This line was added.
  • This line was removed.
  • Formatting was changed.

...

Some additional processing must be done to transform an application/n-triples response into a valid application/sparql-update payload before sending to Fuseki or Sesame. The fcrepo component contains some processors in org.fcrepo.camel.processor to handle this case.

Code Block
languagejava
titlePopulate an external triplestore
linenumberstrue
from("activemq:topic:fedora")
  .to("fcrepo:localhost:8080/fedora/rest?accept=application/n-triples")
  .process(new SparqlUpdateProcessor())
  .setHeader(Exchange.CONTENT_TYPE).constant("application/sparql-update")
  .to("http4:localhost:3030/fcrepo/update");

...

ActiveMQ supports “virtual destinations”, allowing your broker to automatically forward messages from one location to another. If fedora4 is deployed in Tomcat, the ActiveMQ configuration will be located in WEB-INF/classes/config/activemq.xml. That file can be edited to include the following block:
Code Block
languagexml
titleactivemq.xml customization: supporting a queue/fedora endpoint
linenumberstrue
<destinationInterceptors>
  <virtualDestinationInterceptor>
    <virtualDestinations>
      <compositeTopic name="fedora">
        <forwardTo>
          <queue physicalName="fedora"/>
        </forwardTo>
      </compositeTopic>
    </virtualDestinations>
  </virtualDestinationInterceptor>
</destinationInterceptors>

Now a consumer can pull messages from a queue without risk of losing messages.

This configuration, however, will not allow any other applications to read from the original topic. If it is necessary to have /topic/fedora available to consumers, this configuration will be useful:

Code Block
languagexml
titleactivemq.xml customization: supporting topic and queue endpoints
linenumberstrue
<destinationInterceptors>
  <virtualDestinationInterceptor>
    <virtualDestinations>
      <compositeTopic name="fedora" forwardOnly="false">
        <forwardTo>
          <queue physicalName="fedora"/>
        </forwardTo>
      </compositeTopic>
    </virtualDestinations>
  </virtualDestinationInterceptor>
</destinationInterceptors>

Now, both /topic/fedora and /queue/fedora will be available to consumers.

Distributed Brokers

The above example will allow you to distribute the message consumers across multiple machines without missing messages, but it can also be useful to distribute the message broker across multiple machines. This can be especially useful if you want to further decouple the message producers and consumers. It can also be useful for high-availability and failover support.

ActiveMQ supports a variety of distributed broker topologies. To push messages from both the message queue and topic to a remote broker, this configuration can be used:

Code Block
languagexml
titleactivemq.xml customization: distributed brokers
linenumberstrue
<networkConnectors>
  <networkConnector name="fedora_bridge" dynamicOnly="true" uri="static:(tcp://remote-host:61616)">
    <dynamicallyIncludedDestinations>
      <topic physicalName="fedora"/>
      <queue physicalName="fedora"/>
    </dynamicallyIncludedDestinations>
  </networkConnector>
</networkConnectors>

Protocol Support

ActiveMQ brokers support a wide variety of protocols. If Fedora's internal broker is bridged to an external broker, please remember to enable the proper protocols on the remote broker. This can be done like so:

Code Block
languagexml
titleactivemq.xml customization: protocol support
linenumberstrue
<transportConnectors>
  <transportConnector name="openwire" uri="tcp://0.0.0.0:61616"/>
  <transportConnector name="stomp" uri="stomp://0.0.0.0:61613"/>
</transportConnectors>

...