windows communication foundation (wcf) best practices

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Voicu Matei28 July, 2011

Windows Communication Foundation (WCF) Best Practices

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mailto:[email protected]

mailto:[email protected]

Don't build a WCF service !

Unless you have a good reason for it:

Security reasons (business Logic in perimeter network)

Shared business logic (multiple apps or non .NET apps)

Heavy resource consumption (long-running?)

Separate maintainable

Separate scalable

28 July, 2011Windows Communication Foundation (WCF) Best Practices 2

Windows Communication Foundation (WCF) Best Practices 3

Know the tools!

Svcutil.exeSvcConfigEditor.exe SvcTraceViewer.exe REST starter kitAppFabricWeb Services Software Factory (WSSF)

http://servicefactory.codeplex.com/Enterprise Library (EntLib)

Exception Handling Application BlockLogging Application BlockValidation Application Block

28 July, 2011

http://servicefactory.codeplex.com/




Additional tools on CodePlex

http://wcfloadtest.codeplex.comtakes a WCF trace file and a WCF client proxy, or a WCF interface contract, and generates a C# unit test that replays the same sequence of calls found in the trace file. The unit test can then be used to load-test the target

http://wcfcontrib.codeplex.com/library with infrastructure implementations for client and service communications

http://wcfsecurity.codeplex.com/

http://wcfextensions.codeplex.com/WCF Compression Channel

28 July, 2011

http://wcfloadtest.codeplex.com/

http://wcfloadtest.codeplex.com/

http://wcfcontrib.codeplex.com/






http://wcfextensions.codeplex.com/




Service best practices

Separate contract from implementationContract (interface) first (http://wscfblue.codeplex.com/)

Define services in a class library, not directly in a host projectLayering

Separate Service Layer Instance model

Change to Per Call as defaultSession / Singleton – use only when needed

28 July, 2011

http://wscfblue.codeplex.com/

http://wscfblue.codeplex.com/


Exception Handling (I)

For operation specific exceptionsTry/catch, throw FaultException<T>

Favor using FaultException<T>FaultException can be ambiguous to the client because unhandled exceptions arrive as a FaultException

Include FaultContract in service contract definition

28 July, 2011


Exception Handling (II)

If you throw FaultExceptionsPart of the API you are exposing

For global exception handling from servicesUse an error handler

Include exception details in debug builds only !!

28 July, 2011


Hosting

Favor WAS Hosting when on Windows Server 2008Multiple protocol supportIIS Hosting model and tools

Use IIS hosting for external HTTP only

Favor self-hosting for stateful services, callbacks, .NET Service Bus, debugging

Have a console-based debug self-host for development timeCan be a Windows Service project that is used for production self-hosting with a mode switch for debugging

28 July, 2011


When you self host …

Do not put ServiceHost in a using statement in production code

Dispose can throw an exception that masks the real exception thrown from Open call

Explicitly call Close in try/catch and log/ deal with exception in catch

28 July, 2011


Client Proxy Classes (I)

Use static proxy class when possible instead of ChannelFactoryConnection caching in the base class in 3.5Place for encapsulation of common patterns

Hand-code or generate proxy classes for internal servicesLess bloated codeShare service contract and data contracts through librariesExplicit control over config file

28 July, 2011


Client Proxy Classes (II)

Add Service Reference for external services or when you want an async API on the client

Clean up config after it messes it up

Make sure to add references to data contract libraries before adding the service reference to avoid duplicate definitions

Live with the duplicate service contract definition instead of needing to repeatedly clean up the proxy code

28 July, 2011


Client Proxy Management

Cache client proxies if frequent calls to avoid session establishment cost

If secure / reliable session enabledHave to deal more cautiously with faulted proxies

•Check proxy state before using•Get rid of proxy after exception

Don’t put proxies in a using statementDispose call might throw exception and mask real exceptionExplicitly close in a try/catch block, and if Close throws an exception, Abort the proxy to ensure resource clean up

28 July, 2011


Client Exception Management

All exceptions thrown from a service call derive from CommunicationException

FaultException<T> always an explicit error returned from the service

Simple approach:Any exception from a proxy call, safe close the proxy

Advanced approach:FaultException<T> - proxy is reusable

28 July, 2011


Data Contracts

Avoid XmlSerializer and MessageContracts except for interoperable scenarios and REST services

Favor data contracts over serializable typesMore explicit model, better control over what the client sees

Implement IExtensibleDataObjectAvoids dropping data that the service / client does not understand

Avoid passing complex .NET specific types for interoperable servicesDataSets and Exception types

28 July, 2011


SOAP vs REST

Favor SOAP services when you are writing a service that only your code will consume

Favor REST services for publicly exposed, data oriented services

28 July, 2011


Don't forget XmlNamespace settings

By default WCF puts the “http://tempuri.org/” namespace in your wsdl and contracts. Normally you don’t want this. You can control this from three places:

In your config file in the services/service/endpoint/bindingNamespace attribute

In your servicecontract: [ServiceContract(Namespace="http://myuri.net/")]

In your servicebehavior: [ServiceBehavior(Namespace="http://myuri.net/")]

28 July, 2011

http://myuri.net/

http://myuri.net/


More subtle things with WCF

One-way !?•One-way is not always really one-way

•even when doing oneway, closing a client can block until the service side is done

•this is happening in quite some cases where bindings are configured to maintain sessions.

•it happens for example with Message security and or reliable session support (WS-ReliableMessaging).

28 July, 2011


The limits of reliable Messaging with WCF (I)

Messages still can get lost with this mechanism if for example the service is shutdown IIS reset

If you need end-to-end durable reliable messaging with full support for transactional I/O you need an infrastructure that's in control of both ends of the communication

NetMsmqBinding. MSMQ messages are limited to 4 MB

28 July, 2011


The limits of reliable Messaging with WCF (II)

If you are mostly worried about not losing messages under less-than-optimal networking conditions or require session support

the reliable session support in WCF is the right choice

isn’t very handy with load balancers•Sticky session/session affinity

28 July, 2011

20 Windows Communication Foundation (WCF) Best Practices

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28 July, 2011


windows communication foundation (wcf) best practices

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