Enterprise Integration PatternsMessaging Patterns
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Wire TapWire Tap

Messaging Patterns

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Point-to-Point Channels are often used for Document Messages because they ensure that exactly one consumer will consume each message. However, for testing, monitoring or troubleshooting, it may be useful to be able to inspect all messages that travel across the channel.

How do you inspect messages that travel on a point-to-point channel?

Insert a simple Recipient List into the channel that publishes each incoming message to the main channel and a secondary channel.

The Wire Tap is a fixed Recipient List with two output channels. It consumes messages off the input channel and publishes the unmodified message to both output channels. To insert the Wire Tap into a channel, you need to create an additional channel and change the destination receiver to consume of the second channel. Because the analysis logic is located inside a second component, we can insert a generic Wire Tap into any channel without any danger of modifying the primary channel behavior. This improves reuse and reduces the risk of instrumenting an existing solution.

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Related patterns: Competing Consumers, Control Bus, Detour, Document Message, Message Broker, Message Store, Point-to-Point Channel, Publish-Subscribe Channel, Recipient List, Loan Broker System Management


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Enterprise Integration Patterns Find the full description of this pattern in:
Enterprise Integration Patterns
Gregor Hohpe and Bobby Woolf
ISBN 0321200683
650 pages
Addison-Wesley
Creative Commons Attribution License Parts of this page are made available under the Creative Commons Attribution license. You can reuse the pattern icon, the pattern name, the problem and solution statements (in bold), and the sketch under this license. Other portions of the text, such as text chapters or the full pattern text, are protected by copyright.


Table of Contents
Preface
Introduction
Solving Integration Problems using Patterns
Integration Styles
File Transfer
Shared Database
Remote Procedure Invocation
Messaging
Messaging Systems
Message Channel
Message
Pipes and Filters
Message Router
Message Translator
Message Endpoint
Messaging Channels
Point-to-Point Channel
Publish-Subscribe Channel
Datatype Channel
Invalid Message Channel
Dead Letter Channel
Guaranteed Delivery
Channel Adapter
Messaging Bridge
Message Bus
Message Construction
Command Message
Document Message
Event Message
Request-Reply
Return Address
Correlation Identifier
Message Sequence
Message Expiration
Format Indicator
Interlude: Simple Messaging
JMS Request/Reply Example
.NET Request/Reply Example
JMS Publish/Subscribe Example
Message Routing
Content-Based Router
Message Filter
Dynamic Router
Recipient List
Splitter
Aggregator
Resequencer
Composed Msg. Processor
Scatter-Gather
Routing Slip
Process Manager
Message Broker
Message Transformation
Envelope Wrapper
Content Enricher
Content Filter
Claim Check
Normalizer
Canonical Data Model
Interlude: Composed Messaging
Synchronous (Web Services)
Asynchronous (MSMQ)
Asynchronous (TIBCO)
Messaging Endpoints
Messaging Gateway
Messaging Mapper
Transactional Client
Polling Consumer
Event-Driven Consumer
Competing Consumers
Message Dispatcher
Selective Consumer
Durable Subscriber
Idempotent Receiver
Service Activator
System Management
Control Bus
Detour
Wire Tap
Message History
Message Store
Smart Proxy
Test Message
Channel Purger
Interlude: Systems Management Example
Instrumenting Loan Broker
Integration Patterns in Practice
Case Study: Bond Trading System
Concluding Remarks
Emerging Standards
Appendices
Bibliography
Revision History