real-world soa in .net
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Real-World SOA in .Net
Matt Terski
©Copyright 2005 Serlio Software
Too muchSOA hype?
Now WithSOA!
Order Now!!
©Copyright 2005 Serlio Software
Service-Oriented Architecture
Why? What? How?
©Copyright 2005 Serlio Software
leg·a·cy
a gift by will especially of money or other personal property
sys·tem
brittle but important
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Why SOA Matters
• As developers, we need to:– Leverage what we have
• Don’t apply new tools to old problems• Extend existing software assets• Solve a new problem
– Build new systems to last• Be resilient to change• Evolve gracefully
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What is SOA?
• Not a technology but, an architectural style
`
`
`
`
Mainframe Client/ Server
N- tier
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N-Tier Application Silos
Application A Application B Application C
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Solving the Silo Problem
1. Do nothing– Let the users deal with it
2. Build a monolithic application– Efficient (maybe), but unmanageable– Not realistic
3. Make the applications talk– The only real choice– How?
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• Tight coupling– At both design-time and run-time
Application B
Why Not Distributed Objects?
Application A
Application DApplication C
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Terski’s 2am Theorem of Distributed Objects
1. Distributed objects lead to tight coupling.2. Tightly coupled applications must be
deployed together.3. Vital applications cannot be deployed
during peak times. 2am is better.4. Terski prefers to be in bed sleeping at
2am.5. Ergo, Terski avoids distributed objects.
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What is a Service?
Service
DataApplication
Logic
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SOA: The Four Tenets
• Services are autonomous• Services share schema, not type• Service boundaries are explicit• Services negotiate via policy
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Tiers Are Not Layers
Pre
sent
atio
n
Bus
ines
s Lo
gic
Dat
a A
cces
s
DB
This isn’t a service
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New Application Metatypes
InventoryService
CustomerWeb App
DMZ
Partner Web Service
Customers
BusinessPartners
Trusted Network
Order ManagementService
Distribution CenterWeb App
Accounting Service
Credit Bureau
Intranet App
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Healthy Skepticism
• “It’ll never perform.”– Crossing boundaries is expensive– XML serialization is expensive– HTTP is expensive
• My response– Performance: just one of many constraints– SOA brings:
• Scalability, robustness, resilience• And maybe performance
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Demo Background
Mobile Meter Reader App
CustomerWeb App
DMZ
Accounts
Gas Company Customers
Trusted Network
Account Service
Accounts
Meter Reader Web App
Meter Reader
Serlio Gas Company
Billing Service
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Building a Service
1. Ponder the seven fallacies of D.C.2. Design the messages3. Set up the solution4. For each message
a. Model the collaborationb. Implement the message processing
i. service layerii. types layeriii. business layeriv. data access layerv. service agent layer
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The Seven Fallacies of Distributed Computing*
1. The network is reliable.2. Latency is zero.3. Bandwidth is infinite.4. The network is secure.5. Topology doesn’t change.6. There is one administrator.7. Transport cost is zero.
*Peter Deutsch
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Message Patterns
Client Service
Request/Response
One Way
Dialog
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Choosing a Message Pattern
Request/Response
Dialog orOne-way
Dialog One-way
Data is:
More
vola
tile
Read-only
More
sta
ble
Read-write
Processing the message is:
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Message Design
• Avoid CRUD– Leads to concurrency conflicts– Provides no business meaning– Think of “business actions” instead
• Design idempotent messages
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Create the Solution
• It is the unit of deployment• Challenges:
– Manage class dependencies– Make it easy to build
• Shift+Ctrl+B and you’re done
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Create the Solution
Service Business Data
Project References
Types
ServiceAgentProjects/Assemblies
UnitTest
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Model the Collaboration
• Challenges:– How do I separate transport logic from
business logic?– How do I abstract-away data and service
details?
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Implement the Message Processing
• Challenges– How do I make this version-able?– How do I handle exceptions?– How do I manage transactions?– How do I instrument my service?– How do I monitor my service?– How do I authorize users?
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Handling Exceptions
• Exceptions don’t make it to the caller, SOAP faults do
• Client faults– e.g. Business rule violations
• Server faults– e.g. The database is down.
• We share details about client faults, but not server faults
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Messages and Transactions
• Transaction Scope– Receive a message– Update any service data– Generate outgoing messages– Send a response
Service
Data
Transaction Boundary
ApplicationLogic
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Getting Ready for Indigo
• Think “messages”• Use .asmx web services• Use EnterpriseServices, Remoting, or
MSMQ inside of your services• Avoid/abstract-away HttpContext• Use WSE 2.0 for security, policy, etc.
if you need it
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Selected Resources
• Microsoft– http://www.microsoft.com/resources/practices– http://msdn.microsoft.com/webservices/– http://msdn.microsoft.com/architecture/
• Shadowfax– Enterprise Development Reference Architecture– http://workspaces.gotdotnet.com/shadowfx
• Clemens Vasters– http://staff.newtelligence.net/clemensv/
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A Word From our Sponsor
• Serlio Software– http://www.serlio.com
• My blog– http://www.terski.com
©Copyright 2005 Serlio Software
Parting Thoughts
• Embrace and extend existing assets• Build new apps to last• Think
– Resilience– Robustness– Scalability
• Think services and messages
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