CAMEL-11362: create a LeaderElectionservice

camel-core/src/main/java/org/apache/camel/ha/AbstractCamelClusterView.java

@@ -0,0 +1,121 @@
+/**
+ * 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.camel.ha;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.locks.StampedLock;
+import java.util.function.BiConsumer;
+import java.util.function.Predicate;
+
+public abstract class AbstractCamelClusterView implements CamelClusterView {
+    private final CamelCluster cluster;
+    private final String namespace;
+    private final List<FilteringConsumer> consumers;
+    private final StampedLock lock;
+
+    protected AbstractCamelClusterView(CamelCluster cluster, String namespace) {
+        this.cluster = cluster;
+        this.namespace = namespace;
+        this.consumers = new ArrayList<>();
+        this.lock = new StampedLock();
+    }
+
+    @Override
+    public CamelCluster getCluster() {
+        return  this.cluster;
+    }
+
+    @Override
+    public String getNamespace() {
+        return this.namespace;
+    }
+
+    @Override
+    public void addEventListener(BiConsumer<Event, Object> consumer) {
+        long stamp = lock.writeLock();
+
+        try {
+            consumers.add(new FilteringConsumer(e -> true, consumer));
+        } finally {
+            lock.unlockWrite(stamp);
+        }
+    }
+
+    @Override
+    public void addEventListener(Predicate<Event> predicate, BiConsumer<Event, Object> consumer) {
+        long stamp = lock.writeLock();
+
+        try {
+            this.consumers.add(new FilteringConsumer(predicate, consumer));
+        } finally {
+            lock.unlockWrite(stamp);
+        }
+    }
+
+    @Override
+    public void removeEventListener(BiConsumer<Event, Object> consumer) {
+        long stamp = lock.writeLock();
+
+        try {
+            consumers.removeIf(c -> c.getConsumer().equals(consumer));
+        } finally {
+            lock.unlockWrite(stamp);
+        }
+    }
+
+    // **************************************
+    // Events
+    // **************************************
+
+    protected void fireEvent(CamelClusterView.Event event, Object payload) {
+        long stamp = lock.readLock();
+
+        try {
+            for (int i = 0; i < consumers.size(); i++) {
+                consumers.get(0).accept(event, payload);
+            }
+        } finally {
+            lock.unlockRead(stamp);
+        }
+    }
+
+    // **************************************
+    // Helpers
+    // **************************************
+
+    private final class FilteringConsumer implements BiConsumer<Event, Object> {
+        private final Predicate<Event> predicate;
+        private final BiConsumer<Event, Object> consumer;
+
+        FilteringConsumer(Predicate<Event> predicate,  BiConsumer<Event, Object> consumer) {
+            this.predicate = predicate;
+            this.consumer = consumer;
+        }
+
+        @Override
+        public void accept(CamelClusterView.Event event, Object payload) {
+            if (predicate.test(event)) {
+                consumer.accept(event, payload);
+            }
+        }
+
+        public BiConsumer<Event, Object> getConsumer() {
+            return this.consumer;
+        }
+    }
+}

camel-core/src/main/java/org/apache/camel/ha/CamelCluster.java

@@ -0,0 +1,30 @@
+/**
+ * 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.camel.ha;
+
+import org.apache.camel.spi.HasId;
+
+public interface CamelCluster extends HasId {
+    /**
+     * Creates a view of the cluster bound to a namespace.
+     *
+     * @param namespace the namespace the view refer to.
+     * @return the cluster view.
+     * @throws Exception if the view can't be created.
+     */
+    CamelClusterView createView(String namespace) throws Exception;
+}

camel-core/src/main/java/org/apache/camel/ha/CamelClusterMember.java

@@ -0,0 +1,26 @@
+/**
+ * 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.camel.ha;
+
+import org.apache.camel.spi.HasId;
+
+public interface CamelClusterMember extends HasId {
+    /**
+     * @return true if this member is the master.
+     */
+    boolean isMaster();
+}

camel-core/src/main/java/org/apache/camel/ha/CamelClusterView.java

@@ -0,0 +1,85 @@
+/**
+ * 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.camel.ha;
+
+import java.util.List;
+import java.util.function.BiConsumer;
+import java.util.function.Predicate;
+
+/**
+ * Represents the View of the cluster at some given period of time.
+ */
+public interface CamelClusterView {
+
+    enum Event {
+        KEEP_ALIVE,
+        LEADERSHIP_CHANGED;
+    }
+
+    /**
+     * @return the cluster.
+     */
+    CamelCluster getCluster();
+
+    /**
+     * @return the namespace for this view.
+     */
+    String getNamespace();
+
+    /**
+     * Provides the master member.
+     *
+     * @return the master member.
+     */
+    CamelClusterMember getMaster();
+
+    /**
+     * Provides the local member.
+     *
+     * @return the local member.
+     */
+    CamelClusterMember getLocalMember();
+
+    /**
+     * Provides the list of members of the cluster.
+     *
+     * @return the list of members.
+     */
+    List<CamelClusterMember> getMembers();
+
+    /**
+     * Add an event consumer.
+     *
+     * @param consumer the event consumer.
+     */
+    void addEventListener(BiConsumer<Event, Object> consumer);
+
+    /**
+     * Add an event consumer for events matching the given predicate.
+     *
+     * @param predicate the predicate to filter events.
+     * @param consumer the event consumer.
+     */
+    void addEventListener(Predicate<Event> predicate, BiConsumer<Event, Object> consumer);
+
+    /**
+     * Remove the event consumer.
+     *
+     * @param event the event consumer.
+     */
+    void removeEventListener(BiConsumer<Event, Object> event);
+}