Last updated on
17 May 2021
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Also applies to CQ 5.6
Issue
How do I create an OSGi service that is aware of whether it is running on a AEM 5.6.1 cluster as leader node or not?
Solution
In AEM 5.6.1 and later, use a new topology API. For details, see http://sling.apache.org/documentation/bundles/discovery-api-and-impl.html
In earlier versions of AEM, identify a master in a Cluster environment using either Repository descriptor "crx.cluster.master" or ClusterAware interface.
Sample
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.sling.discovery.TopologyEvent;
import org.apache.sling.discovery.TopologyEventListener;
import org.apache.felix.scr.annotations.Component;
import org.apache.felix.scr.annotations.Service;
@Component(metatype = true)
@Service(value = { TopologyEventListener.class })
public class MyClusterAwareService implements Runnable,TopologyEventListener {
private final Logger log = LoggerFactory.getLogger(MyClusterAwareService.class);
private Boolean isLeaderInstance = Boolean.FALSE;
/**
* @see org.apache.sling.discovery.TopologyEventListener#handleTopologyEvent(org.apache.sling.discovery.TopologyEvent)
*/
public void handleTopologyEvent(final TopologyEvent event) {
if ( event.getType() == TopologyEvent.Type.TOPOLOGY_CHANGED
|| event.getType() == TopologyEvent.Type.TOPOLOGY_INIT) {
this.isLeaderInstance = event.getNewView().getLocalInstance().isLeader();
log.info("isLeader confirmed @@@@@@@@@@@@@@@@@@@"+ this.isLeaderInstance);
}
}
/* (non-Javadoc)
* @see java.lang.Runnable#run()
*/
public void run() {
if (isLeaderInstance) {
//TODO: your code here
log.info("isLeader run @@@@@@@@@@@@@@@@@@@"+ this.isLeaderInstance);
}
}
}
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