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-redis/src/main/java/org/springframework/integration/redis/channel/SubscribableRedisChannel.java

@@ -36,8 +36,8 @@ import org.springframework.integration.channel.AbstractMessageChannel;
 import org.springframework.integration.channel.MessagePublishingErrorHandler;
 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.support.channel.BeanFactoryChannelResolver;
 import org.springframework.integration.support.converter.MessageConverter;
 import org.springframework.integration.support.converter.SimpleMessageConverter;
@@ -58,16 +58,16 @@ public class SubscribableRedisChannel extends AbstractMessageChannel implements
 	private final RedisConnectionFactory connectionFactory;
 	private final RedisTemplate redisTemplate;
 	private final String topicName;
-	
-	private final MessageDispatcher dispatcher = new BroadcastingDispatcher(true);
-	
+
+	private final AbstractDispatcher dispatcher = new BroadcastingDispatcher(true);
+
 	private volatile boolean initialized;
-	
+
 	// defaults
 	private volatile Executor taskExecutor = new SimpleAsyncTaskExecutor();
 	private volatile RedisSerializer<?> serializer = new StringRedisSerializer();
 	private volatile MessageConverter messageConverter = new SimpleMessageConverter();
-	
+
 	public SubscribableRedisChannel(RedisConnectionFactory connectionFactory, String topicName) {
 		Assert.notNull(connectionFactory, "'connectionFactory' must not be null");
 		Assert.hasText(topicName, "'topicName' must not be empty");
@@ -80,17 +80,26 @@ public class SubscribableRedisChannel extends AbstractMessageChannel implements
 		Assert.notNull(taskExecutor, "'taskExecutor' must not be null");
 		this.taskExecutor = taskExecutor;
 	}
-	
+
 	public void setMessageConverter(MessageConverter messageConverter) {
 		Assert.notNull(messageConverter, "'messageConverter' must not be null");
 		this.messageConverter = messageConverter;
 	}
-	
+
 	public void setSerializer(RedisSerializer<?> serializer) {
 		Assert.notNull(serializer, "'serializer' must not be null");
 		this.serializer = serializer;
 	}
 
+	/**
+	 * Specify the maximum number of subscribers supported by the
+	 * channel's dispatcher.
+	 * @param maxSubscribers
+	 */
+	public void setMaxSubscribers(int maxSubscribers) {
+		this.dispatcher.setMaxSubscribers(maxSubscribers);
+	}
+
 	public boolean subscribe(MessageHandler handler) {
 		return this.dispatcher.addHandler(handler);
 	}
@@ -98,7 +107,7 @@ public class SubscribableRedisChannel extends AbstractMessageChannel implements
 	public boolean unsubscribe(MessageHandler handler) {
 		return this.dispatcher.removeHandler(handler);
 	}
-	
+
 	@Override
 	protected boolean doSend(Message<?> message, long arg1) {
 		this.redisTemplate.convertAndSend(this.topicName, this.messageConverter.fromMessage(message));
@@ -169,7 +178,7 @@ public class SubscribableRedisChannel extends AbstractMessageChannel implements
 			this.container.destroy();
 		}
 	}
-	
+
 	private class MessageListenerDelegate {
 
 		@SuppressWarnings("unused")

spring-integration-redis/src/main/java/org/springframework/integration/redis/config/RedisChannelParser.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2011 the original author or authors.
+ * Copyright 2002-2012 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,21 +16,21 @@
 
 package org.springframework.integration.redis.config;
 
-import org.w3c.dom.Element;
-
 import org.springframework.beans.factory.support.BeanDefinitionBuilder;
 import org.springframework.beans.factory.xml.ParserContext;
 import org.springframework.integration.config.xml.AbstractChannelParser;
 import org.springframework.integration.config.xml.IntegrationNamespaceUtils;
 import org.springframework.integration.redis.channel.SubscribableRedisChannel;
 import org.springframework.util.StringUtils;
+import org.w3c.dom.Element;
 
 /**
  * Parser for the 'channel' and 'publish-subscribe-channel' elements of the
  * Spring Integration Redis namespace.
- * 
+ *
  * @author Oleg Zhurakusky
  * @author Artem Bilan
+ * @author Gary Russell
  * @since 2.1
  */
 public class RedisChannelParser extends AbstractChannelParser {
@@ -45,13 +45,14 @@ public class RedisChannelParser extends AbstractChannelParser {
 		builder.addConstructorArgReference(connectionFactory);
 		String topicName = element.getAttribute("topic-name");
 		builder.addConstructorArgValue(topicName);
-		
+
 		IntegrationNamespaceUtils.setReferenceIfAttributeDefined(builder, element, "task-executor");
 		IntegrationNamespaceUtils.setReferenceIfAttributeDefined(builder, element, "message-converter");
 		IntegrationNamespaceUtils.setReferenceIfAttributeDefined(builder, element, "serializer");
 		// The following 2 attributes should be added once configurable on the RedisMessageListenerContainer
 		// IntegrationNamespaceUtils.setValueIfAttributeDefined(builder, element, "phase");
 		// IntegrationNamespaceUtils.setValueIfAttributeDefined(builder, element, "auto-startup");
+		this.setMaxSubscribersProperty(parserContext, builder, element, IntegrationNamespaceUtils.DEFAULT_MAX_BROADCAST_SUBSCRIBERS_PROPERTY_NAME);
 		return builder;
 	}
 

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

@@ -137,6 +137,7 @@
 <!-- 				]]></xsd:documentation> -->
 <!-- 			</xsd:annotation> -->
 <!-- 		</xsd:attribute> -->
+		<xsd:attributeGroup ref="integration:subscribersAttributeGroup" />
 	</xsd:complexType>
 
 	<xsd:element name="inbound-channel-adapter">

spring-integration-redis/src/test/java/org/springframework/integration/redis/config/RedisChannelParserTests-context.xml

@@ -18,4 +18,7 @@
 
 	<bean id="redisSerializer" class="org.springframework.data.redis.serializer.StringRedisSerializer"/>
 
+	<int-redis:publish-subscribe-channel id="redisChannelWithSubLimit" topic-name="si.test.topic"
+			serializer="redisSerializer" max-subscribers="1" />
+
 </beans>

spring-integration-redis/src/test/java/org/springframework/integration/redis/config/RedisChannelParserTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2011 the original author or authors.
+ * Copyright 2002-2012 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,9 +16,10 @@
 
 package org.springframework.integration.redis.config;
 
+import static junit.framework.Assert.assertEquals;
+
 import org.junit.Test;
 import org.mockito.Mockito;
-
 import org.springframework.context.support.ClassPathXmlApplicationContext;
 import org.springframework.data.redis.connection.jedis.JedisConnectionFactory;
 import org.springframework.data.redis.serializer.RedisSerializer;
@@ -31,24 +32,28 @@ import org.springframework.integration.redis.rules.RedisAvailable;
 import org.springframework.integration.redis.rules.RedisAvailableTests;
 import org.springframework.integration.test.util.TestUtils;
 
-import static junit.framework.Assert.assertEquals;
-
 /**
  * @author Oleg Zhurakousky
+ * @author Gary Russell
  */
 public class RedisChannelParserTests extends RedisAvailableTests{
-	
-	@Test 
+
+	@Test
 	@RedisAvailable
 	public void testPubSubChannelConfig(){
 		ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("RedisChannelParserTests-context.xml", this.getClass());
 		SubscribableChannel redisChannel = context.getBean("redisChannel", SubscribableChannel.class);
-		JedisConnectionFactory connectionFactory = 
+		JedisConnectionFactory connectionFactory =
 			TestUtils.getPropertyValue(redisChannel, "connectionFactory", JedisConnectionFactory.class);
 		RedisSerializer<?> redisSerializer = TestUtils.getPropertyValue(redisChannel, "serializer", RedisSerializer.class);
 		assertEquals(connectionFactory, context.getBean("redisConnectionFactory"));
 		assertEquals(redisSerializer, context.getBean("redisSerializer"));
 		assertEquals("si.test.topic", TestUtils.getPropertyValue(redisChannel, "topicName"));
+		assertEquals(Integer.MAX_VALUE, TestUtils.getPropertyValue(
+				TestUtils.getPropertyValue(redisChannel, "dispatcher"), "maxSubscribers", Integer.class).intValue());
+		redisChannel = context.getBean("redisChannelWithSubLimit", SubscribableChannel.class);
+		assertEquals(1, TestUtils.getPropertyValue(
+				TestUtils.getPropertyValue(redisChannel, "dispatcher"), "maxSubscribers", Integer.class).intValue());
 		context.stop();
 	}
 
@@ -58,9 +63,9 @@ public class RedisChannelParserTests extends RedisAvailableTests{
 		ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("RedisChannelParserTests-context.xml", this.getClass());
 		SubscribableChannel redisChannel = context.getBean("redisChannel", SubscribableChannel.class);
 		final Message<?> m = new GenericMessage<String>("Hello Redis");
-		
+
 		final Marker marker = Mockito.mock(Marker.class);
-		redisChannel.subscribe(new MessageHandler() {		
+		redisChannel.subscribe(new MessageHandler() {
 			public void handleMessage(Message<?> message) throws MessagingException {
 				assertEquals(m.getPayload(), message.getPayload());
 				marker.mark();
@@ -71,7 +76,7 @@ public class RedisChannelParserTests extends RedisAvailableTests{
 		Mockito.verify(marker, Mockito.times(1)).mark();
 		context.stop();
 	}
-	
+
 	interface Marker {
 		void mark();
 	}