Added ChannelPool to SendOptions with one implementation - LazyChannelPool

Author: flooq

src/main/java/reactor/rabbitmq/ChannelPool.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2018-2019 Pivotal Software Inc, All Rights Reserved.
+ *
+ * Licensed 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 reactor.rabbitmq;
+
+import com.rabbitmq.client.Channel;
+import reactor.core.publisher.Mono;
+import reactor.core.publisher.SignalType;
+
+import java.util.function.BiConsumer;
+
+public interface ChannelPool {
+
+    Mono<? extends Channel> getChannelMono();
+
+    BiConsumer<SignalType, Channel> getChannelCloseHandler();
+
+    void close();
+
+}

src/main/java/reactor/rabbitmq/ChannelPoolFactory.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2018-2019 Pivotal Software Inc, All Rights Reserved.
+ *
+ * Licensed 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 reactor.rabbitmq;
+
+import com.rabbitmq.client.Connection;
+import reactor.core.publisher.Mono;
+
+public class ChannelPoolFactory {
+
+    public static ChannelPool createChannelPool(Mono<? extends Connection> connectionMono) {
+        return createChannelPool(connectionMono, new ChannelPoolOptions());
+    }
+
+    public static ChannelPool createChannelPool(Mono<? extends Connection> connectionMono, ChannelPoolOptions channelPoolOptions) {
+        return new LazyChannelPool(connectionMono, channelPoolOptions);
+    }
+
+}

src/main/java/reactor/rabbitmq/ChannelPoolOptions.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2018-2019 Pivotal Software Inc, All Rights Reserved.
+ *
+ * Licensed 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 reactor.rabbitmq;
+
+import reactor.core.scheduler.Scheduler;
+import reactor.core.scheduler.Schedulers;
+
+public class ChannelPoolOptions {
+
+    private int maxSize = 5;
+
+    private Scheduler subscriptionScheduler = Schedulers.newElastic("sender-channel-pool");
+
+    public ChannelPoolOptions maxSize(int maxSize) {
+        this.maxSize = maxSize;
+        return this;
+    }
+
+    public int getMaxSize() {
+        return maxSize;
+    }
+
+    public ChannelPoolOptions subscriptionScheduler(Scheduler subscriptionScheduler) {
+        this.subscriptionScheduler = subscriptionScheduler;
+        return this;
+    }
+
+    public Scheduler getSubscriptionScheduler() {
+        return subscriptionScheduler;
+    }
+}

src/main/java/reactor/rabbitmq/LazyChannelPool.java

@@ -0,0 +1,100 @@
+/*
+ * Copyright (c) 2018-2019 Pivotal Software Inc, All Rights Reserved.
+ *
+ * Licensed 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 reactor.rabbitmq;
+
+import com.rabbitmq.client.Channel;
+import com.rabbitmq.client.Connection;
+import reactor.core.publisher.Mono;
+import reactor.core.publisher.SignalType;
+import reactor.core.scheduler.Scheduler;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.function.BiConsumer;
+
+import static reactor.rabbitmq.ChannelCloseHandlers.SENDER_CHANNEL_CLOSE_HANDLER_INSTANCE;
+
+/**
+ * This channel pool is lazy initialized. It might even not reach its maximum size {@link ChannelPoolOptions#getMaxSize()} in low-traffic environments.
+ * It always tries to obtain channel from the pool. However, in case of high-traffic number of channels might exceeds channel pool maximum size.
+ *
+ * Channels are added to the pool after their use {@link ChannelPool#getChannelCloseHandler()} and obtained from the pool when channel is requested {@link ChannelPool#getChannelMono()}.
+ *
+ * If pool is empty, new channel is created.
+ * If channel is no longer needed and the channel pool is full (high-traffic), then channel is being closed.
+ * If channel is no longer needed and the channel pool has not reached its capacity, then channel is added to the pool.
+ *
+ * It uses {@link BlockingQueue} internally in a non-blocking way.
+ *
+ */
+class LazyChannelPool implements ChannelPool {
+
+    private final Mono<? extends Connection> connectionMono;
+    private final BlockingQueue<Channel> channelsQueue;
+    private final Scheduler subscriptionScheduler;
+
+    LazyChannelPool(Mono<? extends Connection> connectionMono, ChannelPoolOptions channelPoolOptions) {
+        this.channelsQueue = new LinkedBlockingQueue<>(channelPoolOptions.getMaxSize());
+        this.connectionMono = connectionMono;
+        this.subscriptionScheduler = channelPoolOptions.getSubscriptionScheduler();
+    }
+
+    public Mono<? extends Channel> getChannelMono() {
+        return connectionMono.map(connection -> {
+            Channel channel = channelsQueue.poll();
+            if (channel == null) {
+                channel = createChannel(connection);
+            }
+            return channel;
+        }).subscribeOn(subscriptionScheduler);
+    }
+
+    @Override
+    public BiConsumer<SignalType, Channel> getChannelCloseHandler() {
+        return (signalType, channel) -> {
+            if (!channel.isOpen()) {
+                return;
+            }
+            // maybe also close channel if signalType == SignalType.ON_ERROR ?
+            boolean offer = channelsQueue.offer(channel);
+            if (!offer) {
+                SENDER_CHANNEL_CLOSE_HANDLER_INSTANCE.accept(signalType, channel);
+            }
+        };
+    }
+
+    @Override
+    public void close() {
+        List<Channel> channels = new ArrayList<>();
+        channelsQueue.drainTo(channels);
+        channels.forEach(channel -> {
+            SENDER_CHANNEL_CLOSE_HANDLER_INSTANCE.accept(SignalType.ON_COMPLETE, channel);
+        });
+    }
+
+    private Channel createChannel(Connection connection) {
+        try {
+            return connection.createChannel();
+        } catch (IOException e) {
+            throw new RabbitFluxException("Error while creating channel", e);
+        }
+    }
+
+}

src/main/java/reactor/rabbitmq/SendOptions.java

@@ -98,4 +98,17 @@ public SendOptions channelCloseHandler(BiConsumer<SignalType, Channel> channelCl
         this.channelCloseHandler = channelCloseHandler;
         return this;
     }
+
+    /**
+     * Set the channel pool to use to send messages.
+     *
+     * @param channelPool
+     * @return this {@link SendOptions} instance
+     * @since 1.1.0
+     */
+    public SendOptions channelPool(ChannelPool channelPool) {
+        this.channelMono = channelPool.getChannelMono();
+        this.channelCloseHandler = channelPool.getChannelCloseHandler();
+        return this;
+    }
 }