Idempotent Consumer

来源：互联网发布：windows 10重装系统编辑：程序博客网时间：2024/05/20 18:02

一、Idempotent Consumer

The Idempotent Consumer from the EIP patterns is used to filter out duplicate messages.

This pattern is implemented using the IdempotentConsumer class. This uses an Expression to calculate a unique message ID string for a given message exchange; this ID can then be looked up in the IdempotentRepository to see if it has been seen before; if it has the message is consumed; if its not then the message is processed and the ID is added to the repository.

The Idempotent Consumer essentially acts like a Message Filter to filter out duplicates.

Camel will add the message id eagerly to the repository to detect duplication also for Exchanges currently in progress.
On completion Camel will remove the message id from the repository if the Exchange failed, otherwise it stays there.

Options

The Idempotent Consumer has the following options:

Option Default Description eager true Camel 2.0: Eager controls whether Camel adds the message to the repository before or after the exchange has been processed. If enabled before then Camel will be able to detect duplicate messages even when messages are currently in progress. By disabling Camel will only detect duplicates when a message has successfully been processed. messageIdRepositoryRef null A reference to a IdempotentRepository to lookup in the registry. This option is mandatory when using XML DSL.

Using the Fluent Builders

The following example will use the header myMessageId to filter out duplicates

RouteBuilder builder = new










 RouteBuilder() {





    public




 void configure() {





        errorHandler(deadLetterChannel("mock:error"




));











        from("seda:a"




)   .idempotentConsumer(header("myMessageId"




),





                    MemoryIdempotentRepository.memoryIdempotentRepository(200))





            .to("seda:b"




);





    }





};

The above example will use an in-memory based MessageIdRepository which can easily run out of memory and doesn't work in a clustered environment. So you might prefer to use the JPA based implementation which uses a database to store the message IDs which have been processed

from("direct:start"










).idempotentConsumer(











        header("messageId"










),











        jpaMessageIdRepository(lookup(JpaTemplate.class), PROCESSOR_NAME)











).to("mock:result"










);

In the above example we are using the header messageId to filter out duplicates and using the collection myProcessorName to indicate the Message ID Repository to use. This name is important as you could process the same message by many different processors; so each may require its own logical Message ID Repository.

For further examples of this pattern in use you could look at the junit test case

Spring XML example

The following example will use the header myMessageId to filter out duplicates

<camelContext xmlns="http://camel.apache.org/schema/spring"




 >










    <route>










        <from uri="direct:start"




 />










        <idempotentConsumer messageIdRepositoryRef="myRepo"




 >










            <!-- use the messageId header as key for identifying duplicate messages -->















            <header>










messageId</header>










            <!-- if not a duplicate send it to this mock endpoint -->















            <to uri="mock:result"




 />










        </idempotentConsumer>










    </route>










</camelContext>

Using This Pattern

If you would like to use this EIP Pattern then please read the Getting Started, you may also find the Architecture useful particularly the description of Endpoint and URIs. Then you could try out some of the Examples first before trying this pattern out.

-------------------------------------------------------------------------------------------------------------------------------------------

二、

Contents of /camel/trunk/camel-core/src/test/java/org/apache/camel/processor/IdempotentConsumerTest.java

Parent Directory| Revision Log

Revision 927722 -(show annotations)(download)
Fri Mar 26 08:03:00 2010 UTC(10 months ago)by davsclaus
File size: 6938 byte(s)

CAMEL-2576: Renamed redeliverDelay to redeliveryDelay.

1/**2 * Licensed to the Apache Software Foundation (ASF) under one or more3 * contributor license agreements. See the NOTICE file distributed with4 * this work for additional information regarding copyright ownership.5 * The ASF licenses this file to You under the Apache License, Version 2.06 * (the "License"); you may not use this file except in compliance with7 * the License. You may obtain a copy of the License at8 *9 * http://www.apache.org/licenses/LICENSE-2.010 *11 * Unless required by applicable law or agreed to in writing, software12 * distributed under the License is distributed on an "AS IS" BASIS,13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.14 * See the License for the specific language governing permissions and15 * limitations under the License.16 */17package org.apache.camel.processor;1819import org.apache.camel.ContextTestSupport;20import org.apache.camel.Endpoint;21import org.apache.camel.Exchange;22import org.apache.camel.Message;23import org.apache.camel.Processor;24import org.apache.camel.builder.RouteBuilder;25import org.apache.camel.component.mock.MockEndpoint;26import org.apache.camel.processor.idempotent.MemoryIdempotentRepository;2728/**29 * @version $Revision$30 */31public class IdempotentConsumerTest extends ContextTestSupport {32 protected Endpoint startEndpoint;33 protected MockEndpoint resultEndpoint;3435 @Override36 public boolean isUseRouteBuilder() {37 return false;38 }3940 public void testDuplicateMessagesAreFilteredOut() throws Exception {41 context.addRoutes(new RouteBuilder() {42 @Override43 public void configure() throws Exception {44 from("direct:start").idempotentConsumer(45 header("messageId"), MemoryIdempotentRepository.memoryIdempotentRepository(200)46 ).to("mock:result");47 }48 });49 context.start();5051 resultEndpoint.expectedBodiesReceived("one", "two", "three");5253 sendMessage("1", "one");54 sendMessage("2", "two");55 sendMessage("1", "one");56 sendMessage("2", "two");57 sendMessage("1", "one");58 sendMessage("3", "three");5960 assertMockEndpointsSatisfied();61 }6263 public void testFailedExchangesNotAddedDeadLetterChannel() throws Exception {64 context.addRoutes(new RouteBuilder() {65 @Override66 public void configure() throws Exception {67 errorHandler(deadLetterChannel("mock:error").maximumRedeliveries(2).redeliveryDelay(0).logStackTrace(false));6869 from("direct:start").idempotentConsumer(70 header("messageId"), MemoryIdempotentRepository.memoryIdempotentRepository(200)71 ).process(new Processor() {72 public void process(Exchange exchange) throws Exception {73 String id = exchange.getIn().getHeader("messageId", String.class);74 if (id.equals("2")) {75 throw new IllegalArgumentException("Damm I cannot handle id 2");76 }77 }78 }).to("mock:result");79 }80 });81 context.start();8283 // we send in 2 messages with id 2 that fails84 getMockEndpoint("mock:error").expectedMessageCount(2);85 resultEndpoint.expectedBodiesReceived("one", "three");8687 sendMessage("1", "one");88 sendMessage("2", "two");89 sendMessage("1", "one");90 sendMessage("2", "two");91 sendMessage("1", "one");92 sendMessage("3", "three");9394 assertMockEndpointsSatisfied();95 }9697 public void testFailedExchangesNotAddedDeadLetterChannelNotHandled() throws Exception {98 context.addRoutes(new RouteBuilder() {99 @Override100 public void configure() throws Exception {101 errorHandler(deadLetterChannel("mock:error").handled(false).maximumRedeliveries(2).redeliveryDelay(0).logStackTrace(false));102103 from("direct:start").idempotentConsumer(104 header("messageId"), MemoryIdempotentRepository.memoryIdempotentRepository(200)105 ).process(new Processor() {106 public void process(Exchange exchange) throws Exception {107 String id = exchange.getIn().getHeader("messageId", String.class);108 if (id.equals("2")) {109 throw new IllegalArgumentException("Damm I cannot handle id 2");110 }111 }112 }).to("mock:result");113 }114 });115 context.start();116117 // we send in 2 messages with id 2 that fails118 getMockEndpoint("mock:error").expectedMessageCount(2);119 resultEndpoint.expectedBodiesReceived("one", "three");120121 sendMessage("1", "one");122 sendMessage("2", "two");123 sendMessage("1", "one");124 sendMessage("2", "two");125 sendMessage("1", "one");126 sendMessage("3", "three");127128 assertMockEndpointsSatisfied();129 }130131 public void testFailedExchangesNotAdded() throws Exception {132 context.addRoutes(new RouteBuilder() {133 @Override134 public void configure() throws Exception {135 // use default error handler136 errorHandler(defaultErrorHandler());137138 from("direct:start").idempotentConsumer(139 header("messageId"), MemoryIdempotentRepository.memoryIdempotentRepository(200)140 ).process(new Processor() {141 public void process(Exchange exchange) throws Exception {142 String id = exchange.getIn().getHeader("messageId", String.class);143 if (id.equals("2")) {144 throw new IllegalArgumentException("Damm I cannot handle id 2");145 }146 }147 }).to("mock:result");148 }149 });150 context.start();151152 resultEndpoint.expectedBodiesReceived("one", "three");153154 sendMessage("1", "one");155 sendMessage("2", "two");156 sendMessage("1", "one");157 sendMessage("2", "two");158 sendMessage("1", "one");159 sendMessage("3", "three");160161 assertMockEndpointsSatisfied();162 }163164 protected void sendMessage(final Object messageId, final Object body) {165 template.send(startEndpoint, new Processor() {166 public void process(Exchange exchange) {167 // now lets fire in a message168 Message in = exchange.getIn();169 in.setBody(body);170 in.setHeader("messageId", messageId);171 }172 });173 }174175 @Override176 protected void setUp() throws Exception {177 super.setUp();178179 startEndpoint = resolveMandatoryEndpoint("direct:start");180 resultEndpoint = getMockEndpoint("mock:result");181 }182183}

二、

org.apache.camel.processor.idempotent
Class IdempotentConsumer

java.lang.Object




  

org.apache.camel.impl.ServiceSupport




      

org.apache.camel.processor.idempotent.IdempotentConsumer

All Implemented Interfaces:: Navigate<Processor>, Processor, Service

public class IdempotentConsumer

extends ServiceSupport

implements Processor

, Navigate

<Processor

>
extends ServiceSupport
implements Processor , Navigate <Processor >

An implementation of the Idempotent Consumer pattern.

Version:: $Revision: 835732 $

Constructor Summary

IdempotentConsumer(Expression messageIdExpression,                                     IdempotentRepository<String> idempotentRepository,                                     boolean eager,                                     Processor processor)

Method Summaryprotected voiddoStart()
           protected voiddoStop()
            IdempotentRepository<String>getIdempotentRepository()
            ExpressiongetMessageIdExpression()
            ProcessorgetProcessor()
            booleanhasNext()
          Are there more outputs? List<Processor>next()
          Next group of outputsprotected voidonDuplicateMessage(Exchange exchange, String messageId)
          A strategy method to allow derived classes to overload the behaviour of processing a duplicate message voidprocess(Exchange exchange)
          Processes the message exchange StringtoString()

Methods inherited from class org.apache.camel.impl.ServiceSupport

addChildService, getStatus, getVersion, isRunAllowed, isStarted, isStarting, isStopped, isStopping, removeChildService, start, stop

Methods inherited from class java.lang.Objectclone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

IdempotentConsumer

public IdempotentConsumer



(Expression

 messageIdExpression,


                          IdempotentRepository

<String

> idempotentRepository,


                          boolean eager,


                          Processor

 processor)

Method Detail

toString

public String

 toString



()

Overrides:: toString in class Object

process

public void process



(Exchange

 exchange)


             throws Exception

Description copied from interface: Processor

Processes the message exchange

Specified by:: process in interface Processor

Parameters:: exchange - the message exchange
Throws:: Exception - if an internal processing error has occurred.

public List

<Processor

> next



()

Description copied from interface: Navigate

Next group of outputs

Specified by:: next in interface Navigate<Processor>

Returns:: next group or null if no more outputs

hasNext

public boolean hasNext



()

Description copied from interface: Navigate

Are there more outputs?

Specified by:: hasNext in interface Navigate<Processor>

Returns:: true if more outputs

getMessageIdExpression

public Expression

 getMessageIdExpression



()

getIdempotentRepository

public IdempotentRepository

<String

> getIdempotentRepository



()

getProcessor

public Processor

 getProcessor



()

doStart

protected void doStart



()


                throws Exception

Specified by:: doStart in class ServiceSupport

Throws:: Exception

doStop

protected void doStop



()


               throws Exception

Specified by:: doStop in class ServiceSupport

Throws:: Exception

onDuplicateMessage

protected void onDuplicateMessage



(Exchange

 exchange,


                                  String

 messageId)

A strategy method to allow derived classes to overload the behaviour of processing a duplicate message

Parameters:: exchange - the exchange; messageId - the message ID of this exchange

-------------------------------------------------------------------------------------------------------------------------------------------

三、rg.apache.camel.spi

Interface IdempotentRepository<E>

All Known Implementing Classes:: FileIdempotentRepository, MemoryIdempotentRepository

public interface IdempotentRepository<E>

Access to a repository of Message IDs to implement the Idempotent Consumer pattern.

The add and contains methods is operating according to the Set contract.

Version:: $Revision: 782534 $

Method Summary booleanadd(E key)
          Adds the key to the repository. booleanconfirm(E key)
          Confirms the key, after the exchange has been processed sucesfully. booleancontains(E key)
          Returns true if this repository contains the specified element. booleanremove(E key)
          Removes the key from the repository.

Method Detail

add

boolean add









(E




 key)

Adds the key to the repository.

Parameters:: key - the key of the message for duplicate test
Returns:: true if this repository did not already contain the specified element

contains

boolean contains









(E




 key)

Returns true if this repository contains the specified element.

Parameters:: key - the key of the message
Returns:: true if this repository contains the specified element

remove

boolean remove









(E




 key)

Removes the key from the repository.

Is usually invoked if the exchange failed.

Parameters:: key - the key of the message for duplicate test
Returns:: true if the key was removed

confirm

boolean confirm

(E
 key)  Confirms the key, after the exchange has been processed sucesfully.

Parameters:
key
- the key of the message for duplicate test

Returns:
true
 if the key was confirmed


------------------------------------------------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------------------------------------------

四、Fluent Builders

Camel provides fluent builders for creating routing and mediation rules using a type-safe IDE friendly way which provides smart completion and is refactoring safe.