@Override
public void providersChanged(Set<Node> nodes) {
if (this.elected(nodes)) {
if (!this.master.get()) {
ClusteringServerLogger.ROOT_LOGGER.electedMaster(
this.singletonServiceName.getCanonicalName());
this.singletonDispatcher.stopOldMaster();
this.startNewMaster();
}
} else if (this.master.get()) {
ClusteringServerLogger.ROOT_LOGGER.electedSlave(this.singletonServiceName.getCanonicalName());
this.stopOldMaster();
}
}
private boolean elected(Set<Node> candidates) {
int size = candidates.size();
if (size < this.quorum) {
ClusteringServerLogger.ROOT_LOGGER.quorumNotReached(
this.singletonServiceName.getCanonicalName(), this.quorum);
return false;
} else if (size == this.quorum) {
ClusteringServerLogger.ROOT_LOGGER.quorumJustReached(
this.singletonServiceName.getCanonicalName(), this.quorum);
}
Node elected = this.election(candidates);
if (elected != null) {
ClusteringServerLogger.ROOT_LOGGER.elected(
elected.getName(), this.singletonServiceName.getCanonicalName());
}
return (elected != null) ? elected.equals(this.group.getValue().getLocalNode()) : false;
}
@Override
public AtomicReference<T> getValueRef() {
try {
Map<Node, CommandResponse<AtomicReference<T>>> results = Collections.emptyMap();
while (results.isEmpty()) {
if (!SingletonService.this.started) {
throw new IllegalStateException(
ClusteringServerLogger.ROOT_LOGGER.notStarted(
SingletonService.this.singletonServiceName.getCanonicalName()));
}
results =
SingletonService.this.dispatcher.executeOnCluster(new SingletonValueCommand<T>());
Iterator<CommandResponse<AtomicReference<T>>> responses = results.values().iterator();
while (responses.hasNext()) {
if (responses.next().get() == null) {
// Prune non-master results
responses.remove();
}
}
// We expect only 1 result
int count = results.size();
if (count > 1) {
// This would mean there are multiple masters!
throw ClusteringServerLogger.ROOT_LOGGER.unexpectedResponseCount(
SingletonService.this.singletonServiceName.getCanonicalName(), count);
}
if (count == 0) {
ClusteringServerLogger.ROOT_LOGGER.noResponseFromMaster(
SingletonService.this.singletonServiceName.getCanonicalName());
// Verify whether there is no master because a quorum was not reached during the last
// election
if (SingletonService.this.registration.getProviders().size()
< SingletonService.this.quorum) {
return new AtomicReference<>();
}
// Otherwise, we're in the midst of a new master election, so just try again
Thread.yield();
}
}
return results.values().iterator().next().get();
} catch (Exception e) {
throw new IllegalStateException(e);
}
}
private void startNewMaster() {
this.master.set(true);
ServiceController<?> service = this.container.getRequiredService(this.targetServiceName);
try {
ServiceContainerHelper.start(service);
} catch (StartException e) {
ClusteringServerLogger.ROOT_LOGGER.serviceStartFailed(
e, this.targetServiceName.getCanonicalName());
ServiceContainerHelper.stop(service);
}
}