Enterprise Integration Patterns
Messaging Patterns
Transactional ClientTransactional ClientMessaging Patterns » Messaging Endpoints

A messaging system, by necessity, uses transactional behavior internally. It may be useful for an external client to be able to control the scope of the transactions that impact its behavior.

How can a client control its transactions with the messaging system?

Use a Transactional Client—make the client’s session with the messaging system transactional so that the client can specify transaction boundaries.

Both a sender and a receiver can be transactional. With a sender, the message isn’t “really” added to the channel until the sender commits the transaction. With a receiver, the message isn’t “really” removed from the channel until the receiver commits the transaction. A sender that uses explicit transactions can be used with a receiver that uses implicit transactions, and vise versa. A single channel might have a combination of implicitly and explicitly transactional senders; it could also have a combination of receivers.


Example: (Not quite) Transactional Client in Amazon SQSNEW

Transactional Client semantics can cause serious performance degradation in widely distributed systems. Many cloud-based messaging systems therefore don't implement Transactional Clients. However, these systems still aim to provide protection against client s crashing after they consume but before they process a message. The Amazon Simple Queuing Service (SQS) provides this protection via so-called Visibility Timeout. In this configuration, message consumers don't actually remove messages from the queue - the message simply becomes invisible to other consumers. After successfully processing the message, a message consumer must explicitly delete the message from the queue. If a message is not deleted, it becomes visible again to other consumers after the set timeout interval expires.

The book Cloud Computing Patterns documents this behavior as a distinct pattern called Time-out Based Delivery.

Related patterns: Channel Adapter, Competing Consumers, Document Message, Event-Driven Consumer, Event Message, Guaranteed Delivery, Message, Message Channel, Message Dispatcher, Message Endpoint, Message Router, Message Sequence, Message Translator, Messaging Bridge, Pipes and Filters, Point-to-Point Channel, Polling Consumer, Publish-Subscribe Channel, Request-Reply, Resequencer

Table of Contents
Solving Integration Problems using Patterns
Integration Styles
File Transfer
Shared Database
Remote Procedure Invocation
Messaging Systems
Message Channel
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
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
Composed Msg. Processor
Routing Slip
Process Manager
Message Broker
Message Transformation
Envelope Wrapper
Content Enricher
Content Filter
Claim Check
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
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
Revision History

Enterprise Integration Patterns

Find the full description of this pattern in:
Enterprise Integration Patterns
Gregor Hohpe and Bobby Woolf
ISBN 0321200683
650 pages

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