Github user aledsage commented on a diff in the pull request: https://github.com/apache/brooklyn-server/pull/832#discussion_r139803014 --- Diff: core/src/main/java/org/apache/brooklyn/core/mgmt/internal/ManagementNodeStateListenerManager.java --- @@ -0,0 +1,175 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, + * software distributed under the License is distributed on an + * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + * KIND, either express or implied. See the License for the + * specific language governing permissions and limitations + * under the License. + */ +package org.apache.brooklyn.core.mgmt.internal; + +import static com.google.common.base.Preconditions.checkNotNull; + +import java.io.Closeable; +import java.io.IOException; +import java.util.Collection; +import java.util.List; +import java.util.concurrent.Executors; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.atomic.AtomicInteger; + +import org.apache.brooklyn.api.mgmt.ha.ManagementNodeState; +import org.apache.brooklyn.core.mgmt.ManagementContextInjectable; +import org.apache.brooklyn.core.mgmt.usage.ManagementNodeStateListener; +import org.apache.brooklyn.core.server.BrooklynServerConfig; +import org.apache.brooklyn.util.core.ClassLoaderUtils; +import org.apache.brooklyn.util.core.flags.TypeCoercions; +import org.apache.brooklyn.util.exceptions.Exceptions; +import org.apache.brooklyn.util.time.Duration; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import com.google.common.base.Function; +import com.google.common.collect.Lists; +import com.google.common.util.concurrent.Futures; +import com.google.common.util.concurrent.ListenableFuture; +import com.google.common.util.concurrent.ListeningExecutorService; +import com.google.common.util.concurrent.MoreExecutors; +import com.google.common.util.concurrent.ThreadFactoryBuilder; + +/** + * Handles the notification of {@link ManagementNodeStateListener}s. + * + * @see {@link BrooklynServerConfig#MANAGEMENT_NODE_STATE_LISTENERS} for configuring this. + * @see {@link org.apache.brooklyn.core.mgmt.ha.HighAvailabilityManagerImpl#HighAvailabilityManagerImpl(ManagementContextInternal, ManagementNodeStateListener)} + * for how we get notified of the state-change. + */ +public class ManagementNodeStateListenerManager implements ManagementNodeStateListener { + + private static final Logger LOG = LoggerFactory.getLogger(ManagementNodeStateListenerManager.class); + + private final ManagementContextInternal mgmt; + + private final Object mutex = new Object(); + + private final List<ManagementNodeStateListener> listeners = Lists.newCopyOnWriteArrayList(); + private ManagementNodeState lastPublishedVal; + + private final AtomicInteger listenerQueueSize = new AtomicInteger(); + + private ListeningExecutorService listenerExecutor = MoreExecutors.listeningDecorator(Executors.newSingleThreadExecutor(new ThreadFactoryBuilder() + .setNameFormat("brooklyn-managementnodestate-listener-%d") + .build())); + + public ManagementNodeStateListenerManager(ManagementContextInternal managementContext) { + this.mgmt = checkNotNull(managementContext, "managementContext"); + + // Register a coercion from String->ManagementNodeStateListener, so that MANAGEMENT_NODE_STATE_LISTENERS defined in brooklyn.cfg + // will be instantiated, given their class names. + TypeCoercions.BrooklynCommonAdaptorTypeCoercions.registerInstanceForClassnameAdapter( + new ClassLoaderUtils(this.getClass(), managementContext), + ManagementNodeStateListener.class); + + // Although changing listeners to Collection<ManagementNodeStateListener> is valid at compile time + // the collection will contain any objects that could not be coerced by the function + // declared above. Generally this means any string declared in brooklyn.properties + // that is not a ManagementNodeStateListener. + Collection<?> rawListeners = managementContext.getBrooklynProperties().getConfig(BrooklynServerConfig.MANAGEMENT_NODE_STATE_LISTENERS); + if (rawListeners != null) { + for (Object obj : rawListeners) { + if (obj == null) { + throw new NullPointerException("null listener in config " + BrooklynServerConfig.MANAGEMENT_NODE_STATE_LISTENERS); + } else if (!(obj instanceof ManagementNodeStateListener)) { + throw new ClassCastException("Configured object is not a "+ManagementNodeStateListener.class.getSimpleName()+". This probably means coercion failed: " + obj); + } else { + ManagementNodeStateListener listener = (ManagementNodeStateListener) obj; + if (listener instanceof ManagementContextInjectable) { + ((ManagementContextInjectable) listener).setManagementContext(managementContext); + } + listeners.add((ManagementNodeStateListener)listener); + } + } + } + } + + @Override + public void onStateChange(ManagementNodeState state) { --- End diff -- Agreed it's a bit strange. But I didn't want to complicate the `HighAvailabilityManagerImpl` more. It would only be a few lines in there (a new field to store the last value, etc) - I could move it there if you think it's better @Graeme-Miller?
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