Select a Pattern Agnostic Capability Agnostic Context Agnostic Sub-Controller Asynchronous Queuing Atomic Service Transaction Brokered Authentication Canonical Expression Canonical Protocol Canonical Resources Canonical Schema Canonical Schema Bus Canonical Versioning Capability Composition Capability Recomposition Compatible Change Compensating Service Transaction Composition Autonomy Concurrent Contracts Contract Centralization Contract Denormalization Cross-Domain Utility Layer Data Confidentiality Data Format Transformation Data Model Transformation Data Origin Authentication Decomposed Capability Decoupled Contract Direct Authentication Distributed Capability Domain Inventory Dual Protocols Enterprise Inventory Enterprise Service Bus Entity Abstraction Event-Driven Messaging Exception Shielding Federated Endpoint Layer File Gateway Functional Decomposition Intermediate Routing Inventory Endpoint Legacy Wrapper Logic Centralization Message Screening Messaging Metadata Metadata Centralization Multi-Channel Endpoint Non-Agnostic Context Official Endpoint Orchestration Partial State Deferral Partial Validation Policy Centralization Process Abstraction Process Centralization Protocol Bridging Proxy Capability Redundant Implementation Reliable Messaging Rules Centralization Schema Centralization Service Agent Service Broker Service Callback Service Data Replication Service Decomposition Service Encapsulation Service Facade Service Grid Service Instance Routing Service Layers Service Messaging Service Normalization Service Perimeter Guard Service Refactoring State Messaging State Repository Stateful Services Termination Notification Three-Layer Inventory Trusted Subsystem UI Mediator Utility Abstraction Validation Abstraction Version Identification Overview     History     Acknowledgements     Podcasts     Notification Form     Feedback Form     Press Release #1     Press Release #2     Press Release #3 Master SOA Design Pattern Catalog     Master Pattern List (alphabetical)     Master Pattern List (by category)     Master Pattern List with Page Numbers (PDF)     Master Pattern List (Text)     Pattern Notation     Pattern Profiles     Symbol Legend     Pattern Contribution Form SOA Candidate Patterns     SOA Patterns Review Committee     Candidate Patterns Overview     Candidate Patterns List     Candidate Pattern Contribution Form     Candidate Pattern Feedback Form     SOA Pattern Template Design Pattern Basics     What's a Design Pattern?     What's a Design Pattern Language?     What's a Compound Pattern? Supplemental     SOA Patterns and Application Technologies     SOA Design Patterns Historical Influences     SOA Design Patterns and Design Principles     SOA Design Patterns and Design Granularity     Legal Resources     Design Patterns Publications     Reference Posters     SOAPrinciples.com     WhatIsSOA.com     SOA Visio Stencil Service Callback (Karmarkar) Home > Service Messaging Patterns > Service Callback How can a service communicate asynchronously with its consumers?   Problem When a service needs to respond to a consumer request through the issuance of multiple messages or when service message processing requires a large amount of time, it is often not possible to communicate synchronously. Solution A service can require that consumers communicate with it asynchronously and provide a callback address to which the service can send response messages. Application A callback address generation and message correlation mechanism needs to be incorporated into the messaging framework and the overall inventory architecture. Impacts Asynchronous communication can introduce reliability concerns and can further require that surrounding infrastructure be upgraded to fully support the necessary callback correlation. Principles Standardized Service Contract, Service Loose Coupling, Service Composability Architecture Inventory, Service, Composition Service A sends a message containing the callback address and correlation information to Service B (1). While Service B is processing the message, Service A is unblocked (2). Service B, at some later point in time, sends a response containing the correlation information to the callback address to Service A (3). While Service B retains this callback address, it can continue to issue subsequent response messages to Service A. Related Patterns in This Catalog Asynchronous Queuing (Little, Rischbeck, Simon), Atomic Service Transaction (Erl), Event-Driven Messaging (Little, Rischbeck, Simon), File Gateway (Roy), Message Metadata (Erl), Reliable Messaging (Little, Rischbeck, Simon), Service Agent (Erl) Related Patterns in Other Catalogs Correlation Identifier (Hohpe, Woolfe), Return Address (Hohpe, Woolfe) Related Service-Oriented Computing Goals Increased Intrinsic Interoperability, Reduced IT Burden This page contains excerpts from: SOA Design Patterns by Thomas Erl Foreword by Grady Booch With contributions from David Chappell, Jason Hogg, Anish Karmarkar, Mark Little, David Orchard, Satadru Roy, Thomas Rischbeck, Arnaud Simon, Clemens Utschig, Dennis Wisnosky, and others. (ISBN: 0136135161, Hardcover, Full-Color, 400+ Illustrations, 865 pages) For more information about this book, visit www.soabooks.com.

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