Transactions in an SOA World

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Transactions in an SOA World
Christian Stiller
Applied Architect
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Agenda

• Definition
• Through the ages
• Distributed Database Transactions
• SOA Transactions
• Compensation
• Coordinator
• Managed vs. Un-Managed
• Summary

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Definition Transaction
A transaction is a set of related changes to the
database that the database either completes in
its entirety or discards, leaving no modification
to the database.
OpenEdge Development ABL Handbook
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ACID Properties

• Atomic All or nothing
• Consistent Start End in a Consistent state
• Isolated transactions appear isolated from all
  other operations
• Durable once notified, the transaction will
  persist

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Agenda

• Definition
• Through the ages
• Distributed Database Transactions
• SOA Transactions
• Compensation
• Coordinator
• Managed vs. Un-Managed
• Summary

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Host Based
Application
DO Transaction..
FOR EACH..
REPEAT..
DO ON ERROR..
Update or Read EXCLUSIVE-LOCK..
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Host Based
Client-Server
Application
Client
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Client-Server
n-Tier / Stateless
Client
DO Transaction..
DO ON ERROR..
REPEAT..
FOR EACH..
AppServer
Server
Update or Read EXCLUSIVE-LOCK..
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n-Tier / Stateless
OERA
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OERA Transactions
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Agenda

• Definition
• Through the ages
• Distributed Database Transactions
• SOA Transactions
• Compensation
• Coordinator
• Managed vs. Un-Managed
• Summary

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Definition Distributed Transaction
A distributed transaction is a single
transaction that updates two or more databases.
OpenEdge Data Management Database Admin
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Distributed Transaction
Banking Application
Withdrawal
Deposit
X
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Distributed Transaction 2 Phase Commit

• Ensures transaction consistency across all
  databases
• All commit or none
• Commit in 2 Phases
• Complete or Roll Back

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Distributed Transaction (2PC)
Banking Application
Withdrawal
Deposit
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Distributed Transaction Limbo Transaction
X
Banking Application
Withdrawal
Deposit
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Agenda

• Definition
• Through the ages
• Distributed Database Transactions
• SOA Transactions
• Compensation
• Coordinator
• Managed vs. Un-Managed
• Summary

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SOA Transactions

• Functionality separated into Services
• Application comprises many Services
• Services as a separate platform
• System Independent Entities

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SOA Transaction Issues

• Multiple services resulting in multiple endpoints
• Loosely coupled systems
• Maintaining Txns only possible in closely
  coupled systems
• Services based on any platform
• Resources cant be kept in a locked state
• Alternate Recover methods

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Whats needed

• Uniquely identify transaction across services
• Guarantee that data is delivered and
  notifications sent
• Some form of compensation for when it goes wrong
• Handle errors in asynchronous services

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Possible Solutions

• Compensation
• Transaction Coordinator

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Agenda

• Definition
• Through the ages
• Distributed Database Transactions
• SOA Transactions
• Compensation
• Coordinator
• Managed vs. Un-Managed
• Summary

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Definition Compensation
Compensation is an action taken when something
goes wrong or when there is a change of plan.
IBM Systems Journal April 2002
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Compensation
(5) Error/Exception thrown
(7) Call Compensation
(1) Calls
(3) Calls
Service 1
Service 2
Service 3
(6) Return error
(9) Return Failure
(2) Change DB
(4) Fails
(8) Apply Compensation
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Compensation Issues

• Asynchronous services
• Where to store state details

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Agenda

• Definition
• Through the ages
• Distributed Database Transactions
• SOA Transactions
• Compensation
• Coordinator
• Managed vs. Un-Managed
• Conclusion

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Definition Transaction Coordination
Orchestration of transactions through a
transaction manager or process coordinator.
SOA Systems Feb 2007
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Coordination Service
Coordinator Service
(1) Call
(2) Call
(4) Return
(5) Call
(7) Return Fail
(11) Return Failure
(8) Call Compensation
(10) Return
Service 3
Service 1
Service 2
(3) Change DB
(6) Fails
(9) Apply Compensation
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Coordination Advantages

• Fixes Asynchronous issues of Compensation
• Manages state service information
• Central management of transaction compensation

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Money Transfer
Log
Coordinator Service (generates transaction id and
maintains ACID properties)
(5) Call
(2) Call
(8) Return status
(12) Return status
(9) Call
(3) Return id
(1) request
Client
Initiation Service
Credit Service
Debit Service
(7) Return status
(4) Return id
(11) Return status
(10) Update DB
(6) Update DB
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Agenda

• Definition
• Through the ages
• Distributed Database Transactions
• SOA Transactions
• Compensation
• Coordinator
• Managed vs. Un-Managed
• Summary

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OpenEdge Reference Architecture
Data Sources
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Definition Managed Transaction
A Managed Transaction is managed by the
transaction manager that is built into the
OpenEdge platform. A Managed Transaction can
only access Managed Data Sources
OERA Quick Reference Guide
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Definition Un-Managed Transaction
An Un-Managed Transaction is a transaction that
updates information in an Un-Managed Data Source
or Enterprise Service. An Un-Managed transaction
is not managed by the transaction manager of the
OpenEdge platform.
OERA Quick Reference Guide
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Managed or Un-Managed Transaction?
Managed
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Managed or Un-Managed Transaction?
Managed
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Managed or Un-Managed Transaction?
Un-Managed
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Managed or Un-Managed Transaction?
Managed
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Managed or Un-Managed Transaction?
Un-Managed
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Enterprise Services
Un-Managed
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Money Transfer
Log
Coordinator Service (generates transaction id and
maintains ACID properties)
(5) Call
(2) Call
(8) Return status
(12) Return status
(9) Call
(3) Return id
(1) request
Credit Service
Client
Initiation Service
Debit Service
(7) Return status
(4) Return id
(11) Return status
(10) Update DB
(6) Update DB
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Money Transfer ESB
Log
Dynamic Process Launcher
Coordinator Service (generates transaction id and
maintains ACID properties)
(5) Call
(2) Call
(8) Return status
(12) Return status
(9) Call
(3) Return id
(1) request
Credit Service
Client
Initiation Service
Debit Service
(7) Return status
(4) Return id
(11) Return status
(10) Update DB
(6) Update DB
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Money Transfer BPEL
Log
BPEL Service
Coordinator Service (generates transaction id and
maintains ACID properties)
(5) Call
(2) Call
(8) Return status
(12) Return status
(9) Call
(3) Return id
(1) request
Client
(4) Return id
(7) Return status
(11) Return status
(10) Update DB
(6) Update DB
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BPEL Compensation Handler
Fault Handler
Process (Scope 1)
Compensation Handler S2
Scope 2 Snapshot of Scope 2
Compensation Handler S3
Scope 3 Snapshot of Scope 3
Time
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Agenda

• Definition
• Through the ages
• Distributed Database Transactions
• SOA Transactions
• Compensation
• Coordinator
• Managed vs. Un-Managed
• Summary

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In Summary

• ACID is good, taken in short doses!
• Plan, Design Architect for target
  implementation
• Choose the appropriate transaction model for you
• Consider ESB BPEL

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For More Information, go to

• PSDN
• Service-oriented Architecture (SOA)
  (http//www.psdn.com/library/kbcategory.jspa?categ
  oryID55)
• Forums http//www.psdn.com/library/forumindex.jspa
  
• Web Sites
• Sonic Software www.sonicsoftware.com

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Questions?
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Thank you foryour time
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