Reuse rocketmq producer in 2021.x (#2949)

*Reuse rocketmq producer

spring-cloud-alibaba-starters/spring-cloud-starter-stream-rocketmq/src/main/java/com/alibaba/cloud/stream/binder/rocketmq/integration/outbound/RocketMQProduceFactory.java

@@ -17,6 +17,9 @@
 package com.alibaba.cloud.stream.binder.rocketmq.integration.outbound;
 
 import java.lang.reflect.Field;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicInteger;
 
 import com.alibaba.cloud.stream.binder.rocketmq.constant.RocketMQConst;
 import com.alibaba.cloud.stream.binder.rocketmq.custom.RocketMQBeanContainerCache;
@@ -24,6 +27,7 @@ import com.alibaba.cloud.stream.binder.rocketmq.properties.RocketMQProducerPrope
 import com.alibaba.cloud.stream.binder.rocketmq.utils.RocketMQUtils;
 import org.apache.rocketmq.acl.common.AclClientRPCHook;
 import org.apache.rocketmq.acl.common.SessionCredentials;
+import org.apache.rocketmq.client.exception.MQClientException;
 import org.apache.rocketmq.client.hook.CheckForbiddenHook;
 import org.apache.rocketmq.client.hook.SendMessageHook;
 import org.apache.rocketmq.client.producer.DefaultMQProducer;
@@ -46,12 +50,14 @@ import org.springframework.util.StringUtils;
  */
 public final class RocketMQProduceFactory {
 
-	private RocketMQProduceFactory() {
-	}
-
 	private final static Logger log = LoggerFactory
 			.getLogger(RocketMQProduceFactory.class);
 
+	private static final Map<String, DefaultMQProducer> PRODUCER_REUSABLE_MAP = new ConcurrentHashMap<>();
+
+	private RocketMQProduceFactory() {
+	}
+
 	/**
 	 * init for the producer,including convert producer params.
 	 * @param topic topic
@@ -63,7 +69,6 @@ public final class RocketMQProduceFactory {
 		if (!StringUtils.hasLength(producerProperties.getGroup())) {
 			producerProperties.setGroup(RocketMQConst.DEFAULT_GROUP);
 		}
-
 		Assert.notNull(producerProperties.getNameServer(),
 				"Property 'nameServer' is required");
 
@@ -99,10 +104,15 @@ public final class RocketMQProduceFactory {
 			}
 		}
 		else {
-			producer = new DefaultMQProducer(producerProperties.getNamespace(),
+			String key = getKey(producerProperties);
+			if (PRODUCER_REUSABLE_MAP.containsKey(key)) {
+				return PRODUCER_REUSABLE_MAP.get(key);
+			}
+			producer = new ReusableMQProducer(producerProperties.getNamespace(),
 					producerProperties.getGroup(), rpcHook,
 					producerProperties.getEnableMsgTrace(),
-					producerProperties.getCustomizedTraceTopic());
+					producerProperties.getCustomizedTraceTopic(), key);
+			PRODUCER_REUSABLE_MAP.put(key, producer);
 		}
 
 		producer.setVipChannelEnabled(
@@ -137,4 +147,48 @@ public final class RocketMQProduceFactory {
 		return producer;
 	}
 
+	/**
+	 * get the key from producerProperties.
+	 * @param producerProperties producer properties
+	 * @return key
+	 */
+	private static String getKey(RocketMQProducerProperties producerProperties) {
+		return producerProperties.getNameServer() + "," + producerProperties.getGroup()
+				+ producerProperties.getSendCallBack();
+	}
+
+	/**
+	 * This is a special kind of MQProducer that can be reused among different threads.
+	 * The start and shutdown method can be invoked multiple times, but the real start and
+	 * shutdown logics will only be executed once.
+	 */
+	protected static class ReusableMQProducer extends DefaultMQProducer {
+
+		private final AtomicInteger atomicInteger = new AtomicInteger();
+
+		private final String key;
+
+		public ReusableMQProducer(String namespace, String group, RPCHook rpcHook,
+				boolean enableMsgTrace, String customizedTraceTopic, String key) {
+			super(namespace, group, rpcHook, enableMsgTrace, customizedTraceTopic);
+			this.key = key;
+		}
+
+		@Override
+		public void start() throws MQClientException {
+			if (atomicInteger.getAndIncrement() == 0) {
+				super.start();
+			}
+		}
+
+		@Override
+		public void shutdown() {
+			if (atomicInteger.decrementAndGet() == 0) {
+				PRODUCER_REUSABLE_MAP.remove(key);
+				super.shutdown();
+			}
+		}
+
+	}
+
 }

spring-cloud-alibaba-starters/spring-cloud-starter-stream-rocketmq/src/main/java/com/alibaba/cloud/stream/binder/rocketmq/properties/RocketMQCommonProperties.java

@@ -46,11 +46,15 @@ public class RocketMQCommonProperties implements Serializable {
 	/**
 	 * Consumers of the same role is required to have exactly same subscriptions and
 	 * consumerGroup to correctly achieve load balance. It's required and needs to be
-	 * globally unique. Producer group conceptually aggregates all producer instances of
+	 * globally unique.
+	 * <br>
+	 * Producer group conceptually aggregates all producer instances of
 	 * exactly same role, which is particularly important when transactional messages are
 	 * involved. For non-transactional messages, it does not matter as long as it's unique
 	 * per process. See <a href="http://rocketmq.apache.org/docs/core-concept/">here</a>
-	 * for further discussion.
+	 * for further discussion. However, group for non-transactional messages can indicate
+	 * whether the internal RocketMQProducer should be reused (Only the bindings that use
+	 * the same group can be reused).
 	 */
 	private String group;