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INT-3132 Add minSubscribers to Pub/SubChannel

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Send is deemed to be successful if sent to at least this
number of subscribers (default 0).

Note: when using a task executor, if there is at least one
subscriber, a send is always good, regardless of success
or failure of invoking the handler.

Polishing - Docs - PR Comments
This commit is contained in:
Gary Russell
2013-09-04 13:34:31 -04:00
parent e24d683478
commit 4abeebdb3a
9 changed files with 152 additions and 11 deletions
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17
spring-integration-core/src/main/java/org/springframework/integration/channel/PublishSubscribeChannel.java
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@@ -1,5 +1,5 @@
/*
* Copyright 2002-2012 the original author or authors.
* Copyright 2002-2013 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.
@@ -42,6 +42,8 @@ public class PublishSubscribeChannel extends AbstractSubscribableChannel {
private volatile boolean applySequence;
private volatile int minSubscribers;
private volatile int maxSubscribers = Integer.MAX_VALUE;
@Override
@@ -116,6 +118,18 @@ public class PublishSubscribeChannel extends AbstractSubscribableChannel {
this.maxSubscribers = maxSubscribers;
this.getDispatcher().setMaxSubscribers(maxSubscribers);
}
/**
* If at least this number of subscribers receive the message,
* {@link #send(org.springframework.integration.Message)}
* will return true. Default: 0.
* @param minSubscribers The minimum number of subscribers.
*/
public void setMinSubscribers(int minSubscribers) {
this.minSubscribers = minSubscribers;
this.getDispatcher().setMinSubscribers(minSubscribers);
}
/**
* Callback method for initialization.
*/
@@ -132,6 +146,7 @@ public class PublishSubscribeChannel extends AbstractSubscribableChannel {
this.dispatcher = new BroadcastingDispatcher(this.executor);
this.dispatcher.setIgnoreFailures(this.ignoreFailures);
this.dispatcher.setApplySequence(this.applySequence);
this.dispatcher.setMinSubscribers(this.minSubscribers);
this.dispatcher.setMaxSubscribers(this.maxSubscribers);
}
}

6
spring-integration-core/src/main/java/org/springframework/integration/config/xml/PublishSubscribeChannelParser.java
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@@ -1,5 +1,5 @@
/*
* Copyright 2002-2012 the original author or authors.
* Copyright 2002-2013 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.
@@ -16,11 +16,12 @@
package org.springframework.integration.config.xml;
import org.w3c.dom.Element;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.xml.ParserContext;
import org.springframework.integration.channel.PublishSubscribeChannel;
import org.springframework.util.StringUtils;
import org.w3c.dom.Element;
/**
* Parser for the <publish-subscribe-channel> element.
@@ -43,6 +44,7 @@ public class PublishSubscribeChannelParser extends AbstractChannelParser {
IntegrationNamespaceUtils.setValueIfAttributeDefined(builder, element, "apply-sequence");
this.setMaxSubscribersProperty(parserContext, builder, element,
IntegrationNamespaceUtils.DEFAULT_MAX_BROADCAST_SUBSCRIBERS_PROPERTY_NAME);
IntegrationNamespaceUtils.setValueIfAttributeDefined(builder, element, "min-subscribers");
return builder;
}

33
spring-integration-core/src/main/java/org/springframework/integration/dispatcher/BroadcastingDispatcher.java
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@@ -1,5 +1,5 @@
/*
* Copyright 2002-2012 the original author or authors.
* Copyright 2002-2013 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.
@@ -50,6 +50,8 @@ public class BroadcastingDispatcher extends AbstractDispatcher {
private final Executor executor;
private volatile int minSubscribers;
public BroadcastingDispatcher() {
this(null, false);
}
@@ -89,8 +91,17 @@ public class BroadcastingDispatcher extends AbstractDispatcher {
this.applySequence = applySequence;
}
/**
* If at least this number of subscribers receive the message, {@link #dispatch(Message)}
* will return true. Default: 0.
* @param minSubscribers The minimum number of subscribers.
*/
public void setMinSubscribers(int minSubscribers) {
this.minSubscribers = minSubscribers;
}
public boolean dispatch(Message<?> message) {
boolean dispatched = false;
int dispatched = 0;
int sequenceNumber = 1;
Collection<MessageHandler> handlers = this.getHandlers();
if (this.requireSubscribers && handlers.size() == 0) {
@@ -106,14 +117,23 @@ public class BroadcastingDispatcher extends AbstractDispatcher {
invokeHandler(handler, messageToSend);
}
});
dispatched = true;
dispatched++;
}
else {
boolean success = this.invokeHandler(handler, messageToSend);
dispatched = (success || dispatched);
if (this.invokeHandler(handler, messageToSend)) {
dispatched++;
}
}
}
return dispatched;
if (dispatched == 0 && this.minSubscribers == 0 && logger.isDebugEnabled()) {
if (sequenceSize > 0) {
logger.debug("No subscribers received message, default behavior is ignore");
}
else {
logger.debug("No subscribers, default behavior is ignore");
}
}
return dispatched >= minSubscribers;
}
private boolean invokeHandler(MessageHandler handler, Message<?> message) {
@@ -135,4 +155,5 @@ public class BroadcastingDispatcher extends AbstractDispatcher {
}
}
}

9
spring-integration-core/src/main/resources/org/springframework/integration/config/xml/spring-integration-3.0.xsd
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@@ -449,6 +449,15 @@
</xsd:documentation>
</xsd:annotation>
</xsd:attribute>
<xsd:attribute name="min-subscribers" type="xsd:string">
<xsd:annotation>
<xsd:documentation><![CDATA[
Specifies the minimum subscribers required to be subscribed to this channel; if the minimum number
of subscribers receive the message, the send is deemed to be successful (returns true).
Defaults to 0.
]]></xsd:documentation>
</xsd:annotation>
</xsd:attribute>
<xsd:attributeGroup ref="subscribersAttributeGroup" />
</xsd:extension>
</xsd:complexContent>

2
spring-integration-core/src/test/java/org/springframework/integration/config/xml/DispatcherMaxSubscribersDefaultConfigurationTests-context.xml
View File

@@ -29,6 +29,6 @@
<int:publish-subscribe-channel id="pubSubDefaultChannel" />
<int:publish-subscribe-channel id="pubSubExplicitChannel" max-subscribers="2 "/>
<int:publish-subscribe-channel id="pubSubExplicitChannel" max-subscribers="2 " min-subscribers="1"/>
</beans>

4
spring-integration-core/src/test/java/org/springframework/integration/config/xml/DispatcherMaxSubscribersTests.java
View File

@@ -1,5 +1,5 @@
/*
* Copyright 2002-2012 the original author or authors.
* Copyright 2002-2013 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.
@@ -78,5 +78,7 @@ public abstract class DispatcherMaxSubscribersTests {
Integer explicitMax = TestUtils.getPropertyValue(
TestUtils.getPropertyValue(pubSubExplicitChannel, "dispatcher"), "maxSubscribers", Integer.class);
assertEquals(val2, explicitMax.intValue());
Integer explicitMin = TestUtils.getPropertyValue(pubSubExplicitChannel, "dispatcher.minSubscribers", Integer.class);
assertEquals(1, explicitMin.intValue());
}
}

65
spring-integration-core/src/test/java/org/springframework/integration/core/MessagingTemplateTests.java
View File

@@ -36,9 +36,11 @@ import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.context.support.StaticApplicationContext;
import org.springframework.integration.Message;
import org.springframework.integration.MessageChannel;
import org.springframework.integration.MessageDeliveryException;
import org.springframework.integration.MessagingException;
import org.springframework.integration.channel.AbstractMessageChannel;
import org.springframework.integration.channel.DirectChannel;
import org.springframework.integration.channel.PublishSubscribeChannel;
import org.springframework.integration.channel.QueueChannel;
import org.springframework.integration.endpoint.PollingConsumer;
import org.springframework.integration.handler.AbstractReplyProducingMessageHandler;
@@ -547,6 +549,69 @@ public class MessagingTemplateTests {
}
}
@Test
public void testNoSubs() {
MessagingTemplate template = new MessagingTemplate();
PublishSubscribeChannel channel = new PublishSubscribeChannel();
template.setDefaultChannel(channel);
template.convertAndSend("foo");
}
@Test
public void testSubsAllFail() {
MessagingTemplate template = new MessagingTemplate();
PublishSubscribeChannel channel = new PublishSubscribeChannel();
channel.subscribe(new MessageHandler() {
@Override
public void handleMessage(Message<?> message) throws MessagingException {
throw new RuntimeException();
}
});
channel.setIgnoreFailures(true);
template.setDefaultChannel(channel);
template.convertAndSend("foo");
}
@Test
public void testEnoughSubs() {
MessagingTemplate template = new MessagingTemplate();
PublishSubscribeChannel channel = new PublishSubscribeChannel();
channel.setMinSubscribers(1);
channel.subscribe(new MessageHandler() {
@Override
public void handleMessage(Message<?> message) throws MessagingException {
}
});
template.setDefaultChannel(channel);
template.convertAndSend("foo");
}
@Test(expected=MessageDeliveryException.class)
public void testNoSubsFatal() {
MessagingTemplate template = new MessagingTemplate();
PublishSubscribeChannel channel = new PublishSubscribeChannel();
channel.setMinSubscribers(1);
template.setDefaultChannel(channel);
template.convertAndSend("foo");
}
@Test(expected=MessageDeliveryException.class)
public void testNotEnoughSubsFatal() {
MessagingTemplate template = new MessagingTemplate();
PublishSubscribeChannel channel = new PublishSubscribeChannel();
channel.setMinSubscribers(2);
channel.subscribe(new MessageHandler() {
@Override
public void handleMessage(Message<?> message) throws MessagingException {
}
});
template.setDefaultChannel(channel);
template.convertAndSend("foo");
}
@Test
public void testNeverReceive() {
MessagingTemplate template = new MessagingTemplate();

14
src/reference/docbook/channel.xml
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@@ -81,6 +81,20 @@
must be a <interfacename>MessageHandler</interfacename> itself, and the subscriber's
<methodname>handleMessage(Message)</methodname> method will be invoked in turn.
</para>
<para>
Prior to version 3.0, invoking the send method on a <classname>PublishSubscribeChannel</classname> that
had no subscribers returned <code>false</code>. When used in conjunction with a
<classname>MessagingTemplate</classname>, a <classname>MessageDeliveryException</classname>
was thrown. Starting with version 3.0, the behavior has changed such that a send is
always considered successful if at least the minimum subscribers are present (and successfully
handle the message). This behavior can be modified by setting the <code>minSubscribers</code>
property, which defaults to <code>0</code>.
</para>
<note>
If a <classname>TaskExecutor</classname> is used, only the presence of the correct number
of subscribers is used for this determination, because the actual handling of the message
is performed asynchronously.
</note>
</section>
<section id="channel-implementations-queuechannel">
<title>QueueChannel</title>

13
src/reference/docbook/whats-new.xml
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@@ -363,5 +363,18 @@
For more information see <xref linkend="http"/>.
</para>
</section>
<section id="3.0-pub-sub">
<title>PublishSubscribeChannel Behavior</title>
<para>
Previously, sending to a &lt;publish-subscribe-channel/&gt; that had
no subscribers would return a <code>false</code> result. If used in conjunction with
a <classname>MessagingTemplate</classname>, this would result in an exception being thrown.
Now, the <classname>PublishSubscribeChannel</classname> has a property
<code>minSubscribers</code> (default 0). If the message is sent to at least the minimum
number of subscribers, the send is deemed to be successful (even if zero). If an application
is expecting to get an exception under these conditions, set the minimum subscribers to at
least 1.
</para>
</section>
</section>
</chapter>