INT-2285 Implement max-subscribers on Channels

Add a subscriber limit on both unicast and publish-subscribe
channels. This permits detection of inadvertent channel wiring
during context initialization.

Also add a mechanism to globally set these defaults.

Two properties are added to ChannelInitializer. If the
'channelInitializer' bean is declared before a channel, and
these properties are set, it will globally override the
default (Integer.MAX_VALUE) for these properties.

For example:

    <bean id="channelInitializer" class="org.springframework.integration.config.xml.ChannelInitializer">
        <property name="autoCreate" value="true" />
        <property name="defaultMaxUnicastSubscribers" value="1" />
        <property name="defaultMaxMulticastSubscribers" value="2" />
    </bean>

will make the default max-subscribers 1 and 2 for <channel/> and
<publish-subscribe/> channels respectively.

Also applies to module channels (jms, amqp, redis).

spring-integration-jms/src/main/java/org/springframework/integration/jms/SubscribableJmsChannel.java

@@ -20,7 +20,6 @@ import javax.jms.MessageListener;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
-
 import org.springframework.beans.factory.DisposableBean;
 import org.springframework.context.SmartLifecycle;
 import org.springframework.integration.Message;
@@ -29,6 +28,7 @@ import org.springframework.integration.MessageDispatchingException;
 import org.springframework.integration.MessagingException;
 import org.springframework.integration.core.MessageHandler;
 import org.springframework.integration.core.SubscribableChannel;
+import org.springframework.integration.dispatcher.AbstractDispatcher;
 import org.springframework.integration.dispatcher.BroadcastingDispatcher;
 import org.springframework.integration.dispatcher.MessageDispatcher;
 import org.springframework.integration.dispatcher.RoundRobinLoadBalancingStrategy;
@@ -48,16 +48,26 @@ public class SubscribableJmsChannel extends AbstractJmsChannel implements Subscr
 
 	private final AbstractMessageListenerContainer container;
 
-	private volatile MessageDispatcher dispatcher;
-	
+	private volatile AbstractDispatcher dispatcher;
+
 	private volatile boolean initialized;
-	
+
+	private volatile int maxSubscribers = Integer.MAX_VALUE;
+
 	public SubscribableJmsChannel(AbstractMessageListenerContainer container, JmsTemplate jmsTemplate) {
 		super(jmsTemplate);
 		Assert.notNull(container, "container must not be null");
 		this.container = container;
 	}
 
+	/**
+	 * Specify the maximum number of subscribers supported by the
+	 * channel's dispatcher.
+	 * @param maxSubscribers
+	 */
+	public void setMaxSubscribers(int maxSubscribers) {
+		this.maxSubscribers = maxSubscribers;
+	}
 
 	public boolean subscribe(MessageHandler handler) {
 		Assert.state(this.dispatcher != null, "'MessageDispatcher' must not be null. This channel might not have been initialized");
@@ -96,6 +106,7 @@ public class SubscribableJmsChannel extends AbstractJmsChannel implements Subscr
 			unicastingDispatcher.setLoadBalancingStrategy(new RoundRobinLoadBalancingStrategy());
 			this.dispatcher = unicastingDispatcher;
 		}
+		this.dispatcher.setMaxSubscribers(this.maxSubscribers);
 	}
 
 

spring-integration-jms/src/main/java/org/springframework/integration/jms/config/JmsChannelFactoryBean.java

@@ -74,7 +74,7 @@ public class JmsChannelFactoryBean extends AbstractFactoryBean<AbstractJmsChanne
 	private volatile String clientId;
 
 	private volatile String concurrency;
-	
+
 	private volatile Integer concurrentConsumers;
 
 	private volatile ConnectionFactory connectionFactory;
@@ -110,7 +110,7 @@ public class JmsChannelFactoryBean extends AbstractFactoryBean<AbstractJmsChanne
 	private volatile Long receiveTimeout;
 
 	private volatile Long recoveryInterval;
-	
+
 	private volatile String beanName;
 
 	/**
@@ -133,6 +133,8 @@ public class JmsChannelFactoryBean extends AbstractFactoryBean<AbstractJmsChanne
 
 	private volatile Integer transactionTimeout;
 
+	private volatile int maxSubscribers = Integer.MAX_VALUE;
+
 
 	public JmsChannelFactoryBean() {
 		this(true);
@@ -202,7 +204,7 @@ public class JmsChannelFactoryBean extends AbstractFactoryBean<AbstractJmsChanne
 	public void setConcurrency(String concurrency) {
 		this.concurrency = concurrency;
 	}
-	
+
 	public void setConcurrentConsumers(int concurrentConsumers) {
 		this.concurrentConsumers = concurrentConsumers;
 	}
@@ -314,6 +316,10 @@ public class JmsChannelFactoryBean extends AbstractFactoryBean<AbstractJmsChanne
 		this.transactionTimeout = transactionTimeout;
 	}
 
+	public void setMaxSubscribers(int maxSubscribers) {
+		this.maxSubscribers = maxSubscribers;
+	}
+
 	public void setBeanName(String name) {
 		this.beanName = name;
 	}
@@ -328,7 +334,9 @@ public class JmsChannelFactoryBean extends AbstractFactoryBean<AbstractJmsChanne
 		this.initializeJmsTemplate();
 		if (this.messageDriven) {
 			this.container = this.createContainer();
-			this.channel = new SubscribableJmsChannel(this.container, this.jmsTemplate);
+			SubscribableJmsChannel subscribableJmsChannel = new SubscribableJmsChannel(this.container, this.jmsTemplate);
+			subscribableJmsChannel.setMaxSubscribers(this.maxSubscribers);
+			this.channel = subscribableJmsChannel;
 		}
 		else {
 			Assert.isTrue(!Boolean.TRUE.equals(this.pubSubDomain),
@@ -388,27 +396,27 @@ public class JmsChannelFactoryBean extends AbstractFactoryBean<AbstractJmsChanne
 		container.setSessionAcknowledgeMode(this.sessionAcknowledgeMode);
 		container.setSessionTransacted(this.sessionTransacted);
 		container.setSubscriptionDurable(this.subscriptionDurable);
-		
-		
-		
+
+
+
 		if (container instanceof DefaultMessageListenerContainer) {
 			DefaultMessageListenerContainer dmlc = (DefaultMessageListenerContainer) container;
 			if (this.cacheLevelName != null) {
 				dmlc.setCacheLevelName(this.cacheLevelName);
 			}
-		
+
 			if (StringUtils.hasText(this.concurrency)){
 				dmlc.setConcurrency(this.concurrency);
 			}
-			
+
 			if (this.concurrentConsumers != null){
 				dmlc.setConcurrentConsumers(this.concurrentConsumers);
 			}
-			
+
 			if (this.maxConcurrentConsumers != null){
 				dmlc.setMaxConcurrentConsumers(this.maxConcurrentConsumers);
 			}
-				
+
 			if (this.idleTaskExecutionLimit != null) {
 				dmlc.setIdleTaskExecutionLimit(this.idleTaskExecutionLimit);
 			}
@@ -437,11 +445,11 @@ public class JmsChannelFactoryBean extends AbstractFactoryBean<AbstractJmsChanne
 			if (StringUtils.hasText(this.concurrency)){
 				smlc.setConcurrency(this.concurrency);
 			}
-			
+
 			if (this.concurrentConsumers != null){
 				smlc.setConcurrentConsumers(this.concurrentConsumers);
 			}
-			
+
 			smlc.setPubSubNoLocal(this.pubSubNoLocal);
 			smlc.setTaskExecutor(this.taskExecutor);
 		}
@@ -485,6 +493,7 @@ public class JmsChannelFactoryBean extends AbstractFactoryBean<AbstractJmsChanne
 		}
 	}
 
+	@Override
 	protected void destroyInstance(AbstractJmsChannel instance) throws Exception {
 		if (instance instanceof SubscribableJmsChannel) {
 			((SubscribableJmsChannel) this.channel).destroy();

spring-integration-jms/src/main/java/org/springframework/integration/jms/config/JmsChannelParser.java

@@ -58,9 +58,11 @@ public class JmsChannelParser extends AbstractChannelParser {
 		builder.addPropertyReference("connectionFactory", connectionFactory);
 		if ("channel".equals(element.getLocalName())) {
 			this.parseDestination(element, parserContext, builder, "queue");
+			this.setMaxSubscribersProperty(parserContext, builder, element, IntegrationNamespaceUtils.DEFAULT_MAX_UNICAST_SUBSCRIBERS_PROPERTY_NAME);
 		}
 		else if ("publish-subscribe-channel".equals(element.getLocalName())) {
 			this.parseDestination(element, parserContext, builder, "topic");
+			this.setMaxSubscribersProperty(parserContext, builder, element, IntegrationNamespaceUtils.DEFAULT_MAX_BROADCAST_SUBSCRIBERS_PROPERTY_NAME);
 		}
 		String containerType = element.getAttribute(CONTAINER_TYPE_ATTRIBUTE);
 		String containerClass = element.getAttribute(CONTAINER_CLASS_ATTRIBUTE);

spring-integration-jms/src/main/resources/org/springframework/integration/jms/config/spring-integration-jms-2.2.xsd

@@ -376,6 +376,7 @@
 				]]></xsd:documentation>
 			</xsd:annotation>
 		</xsd:attribute>
+		<xsd:attributeGroup ref="integration:subscribersAttributeGroup" />
 	</xsd:complexType>
 
 	<xsd:element name="message-driven-channel-adapter">

spring-integration-jms/src/test/java/org/springframework/integration/jms/config/JmsChannelParserTests-context.xml

@@ -16,7 +16,7 @@
 		time-to-live="123"
 		priority="12"/>
 
-	<jms:channel id="queueNameChannel" queue-name="test.queue"/>
+	<jms:channel id="queueNameChannel" queue-name="test.queue" max-subscribers="1" />
 
 	<jms:channel id="queueNameWithResolverChannel" queue-name="foo"
 			     destination-resolver="destinationResolver" connection-factory="connFact"/>

spring-integration-jms/src/test/java/org/springframework/integration/jms/config/JmsChannelParserTests.java

@@ -131,6 +131,8 @@ public class JmsChannelParserTests {
 		assertEquals(DeliveryMode.PERSISTENT, TestUtils.getPropertyValue(jmsTemplate, "deliveryMode"));
 		assertEquals(123L, TestUtils.getPropertyValue(jmsTemplate, "timeToLive"));
 		assertEquals(12, TestUtils.getPropertyValue(jmsTemplate, "priority"));
+		assertEquals(Integer.MAX_VALUE, TestUtils.getPropertyValue(
+				TestUtils.getPropertyValue(channel, "dispatcher"), "maxSubscribers", Integer.class).intValue());
 	}
 
 	@Test
@@ -142,6 +144,8 @@ public class JmsChannelParserTests {
 		AbstractMessageListenerContainer container = (AbstractMessageListenerContainer) accessor.getPropertyValue("container");
 		assertEquals("test.queue", jmsTemplate.getDefaultDestinationName());
 		assertEquals("test.queue", container.getDestinationName());
+		assertEquals(1, TestUtils.getPropertyValue(
+				TestUtils.getPropertyValue(channel, "dispatcher"), "maxSubscribers", Integer.class).intValue());
 	}
 
 	@Test