WCF Tips and Tricks

WCF Tips and Tricks[a selection] from the field

Christian Weyer, thinktecture

christian.weyer@thinktecture.com

andChristian Weyer

•Support & consulting for Windows and .NET software developers and architects

•Developer coaching and mentoring

•Architecture consulting and prototyping

•Architecture and code reviews

•Applicationoptimization, troubleshooting, debugging

•Focus on distributed applications, service orientation, workflows, cloud computing, interoperability, security, end-to-end solutions

•Windows Server, WCF, WF, MSMQ, Azure Services, Windows Azure

•http://www.thinktecture.com

•christian.weyer@thinktecture.com

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For starters: Super-duper TIP

•WCF is not just Web Services !

•WCF is not always about SOA !

•WCF does not stand for

•Web Services Consumption Foundation

•Windows Cool-SOA Foundation

•It is the Windows CommunicationFoundation!

3

Agenda –Dealing with...

•Consuming

•Hosting

•Bindings

•Quotas & throttles

•Metadata/WSDL

•Performance & throughput

•Large data

•Tracing

Problems èSolutions/Tips è

Samples4

Notcovered, some...

•Contract modelling

•REST

•Security

•Asynchronous processing

•Fault handling

•Deep extensibility

•WF integration

•NATs & firewalls

•... and surely more ...

5

Consuming–Problems

•Do I always need to create a proxy class from WSDL/MEX?

•How can I make consuming services more robust?

•Is there a way to improve performance when calling services?

•How can I call in-process ‘services’ and WCF services in the same way?

6

Consuming–Solutions I

•For non-interopno need to use svcutil.exeor ‘Add Service Reference’

•shared contracts approach works good in WCF-to-WCF scenarios

•ChannelFactory<T>and DuplexChannelFactory<T> are powerful means

•use custom interface extending service contract & IClientChannel

•Avoid usingstatement when dealing with proxies (ICommunicationObject-derivedobjects)

•can still throw at end of using block, e.g. for network errors

•explicit exception handling; can be dealt withe.g. in extension method

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Consuming–Solutions II

•Try to cache proxy or ChannelFactoryin high-throughput applications

•creating them can mean significant overhead

•ASP.NET client applications should not create ChannelFactoryon each page call

•Abstract away channel/proxy creation details with Activator.CreateInstance& ChannelFactory<T>

•Service Agent pattern

•for local and remote services

•no WCF-isms available, like sessions etc.

•WCF 4.0 will offer in-process, intra-AppDomainchannel

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Consuming–Samplesinterface IMyContractChannel: IMyContract, System.ServiceModel.IClientChannel{}

ChannelFactory<IMyContractChannel> cf= new ChannelFactory<IMyContractChannel>(binding, address);

IMyContractChannelclient = cf.CreateChannel();

client.DoIt(…);

client.Close();try{… client.Close();}catch (CommunicationExceptione){… client.Abort();}catch (TimeoutExceptione){… client.Abort();}catch (Exception e){… client.Abort();throw;}

IMyContractChannelchannel=

ChannelFactoryManager<IMyContractChannel>

.GetChannel("BasicHttpBinding");

Client sideClient side

Client side

Client side9

Hosting-Problems

•Which host to use? IIS/WAS or a self-host?

•How do I inject logic in IIS/WAS hosting?

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Hosting–Solutions

•Use IIS/WAS for robust, highly scalable services

•beware of the process & AppDomainlifecycle features

•when using non-HTTP (TCP, Named Pipes, MSMQ) with WAS hosting AppDomainrecycling still comes into your way

•Use self-hosting in Windows Service to have full control and light-weight hosting environment

•Custom ServiceHost& ServiceHostFactoryimplementations to provide custom initialization code

•hook up factory in .svcfile for IIS/WAS

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Hosting–Samplesclass MyServiceHost: System.ServiceModel.ServiceHost{public MyServiceHost(Type serviceType, paramsUri[] baseAddresses): base(serviceType, baseAddresses){...}protected override void ApplyConfiguration(){...}}

class MyServiceHostFactory: System.ServiceModel.Activation.ServiceHostFactory

{

protected override ServiceHostCreateServiceHost(Type serviceType, Uri[] baseAddresses)

{

return new MyServiceHost(serviceType, baseAddresses);

}

}

<%@ ServiceHostLanguage="C#" Debug="true" Service="MediaService" Factory="MyServiceHostFactory" %>Custom ServiceHost

Custom ServiceHostFactory

.svc file12

Bindings-Problems

•MyWCF serviceisslow, whatishappening?

•I wanttouseHTTP but not necessarilyangle brackets(aka‚XML‘)

•HowcanI choosefromthebestcommunicationoptions?

13

Bindings–Solutions I

•Beware of using the wrong bindings

•e.g. Visual Studio WCF wizards use WsHttpBinding(heavy with message security & session-based)

•only use features you really need

•Think about the real need for session-bound channels/bindings

•sessions change the game of fault and error handling

•use sessions when you need session semantics in your service

•But: sessions cangive performance improvements

•e.g. security token hand-shake happens only once with SecureConversation

14

Bindings–Solutions II

•Custom bindings will save your day

•e.g. binary over HTTP often a good trade-off for WCF-to-WCF communication scenarios

•build custom binding in configor code

•Create user-defined binding for easier re-usage

•bake common custom binding setups into re-usable code and configimplementations

•Use a custom encoder for providing encoding-level tweaks & optimizations

•e.g. enhanced text encoder in SDK or FastInfoSetencoder from 3rdparty

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Bindings-Samples

<extensions>

<bindingExtensions>

<add name="netHttpBinding"

type="NetHttpBindingCollectionElement, Thinktecture.ServiceModel, Version=…" />

</bindingExtensions>

</extensions>

<bindings>

<netHttpBinding>

<binding name="unsecureNetHttp" securityMode="None" />

</netHttpBinding>

<customBinding>

<binding name="binaryHttp">

<binaryMessageEncoding/>

<httpTransport/>

</binding>

</customBinding>

</bindings>

public class NetHttpBinding:

System.ServiceModels.Channels.Binding,

ISecurityCapabilities

{

HttpTransportBindingElementhttpTransport;

HttpsTransportBindingElementhttpsTransport;

BinaryMessageEncodingBindingElementbinaryEncoding;

NetHttpSecurityModesecurityMode;

...

}app/web.config

User-defined binding16

Quotas & Throttles -Problems

•Beyond Hello World, all my services and consumers fail with strange exceptions

•My services do not perform the way they are supposed to

•How can I teach WCF to be less ‘conservative’ in Intranet environments?

17

Quotas & Throttles -Solutions

•Bindings

•adjust buffers, connection limits, timeouts

•Behaviors

•configure throttling service behavior

•Serializers

•check maximum items in object graph value

•Custom ChannelFactoryand ServiceHostcan automate all this

•e.g. through profiles

Defaultsnot true!

SvcConfigEditor18

Quotas & Throttles -Samples

<bindings>

<webHttpBinding>

<binding name="rawStreamingWeb" transferMode="StreamedResponse">

<readerQuotasmaxArrayLength="999999999"/>

</binding>

</webHttpBinding>

<customBinding>

<binding name="httpStreaming" sendTimeout="Infinite">

<binaryMessageEncoding/>

<httpTransporttransferMode="Streamed" />

</binding>

</customBinding>

<bindings><behaviors><serviceBehaviors><behavior name="MyServiceBehavior"><serviceThrottlingmaxConcurrentCalls="1500" maxConcurrentInstances="1500" maxConcurrentSessions="1500" /> </behavior></serviceBehaviors></behaviors>

app/web.configapp/web.config

Consuming code

19

WSDL & Metadata -Problems

•Some non-WCF consumers cannot understand the WSDL WCF produces

•My WSDL contains the wrong host name

•I cannot use multiple IIS web site bindings with my WCF services

20

WSDL & Metadata –Solutions I

•Use custom extension to flatten WSDL into one file

•need to use same namespace values forServiceContract, ServiceBehavior, BindingNamespace

•eliminates wsdl:importand xsd:import

•Register hostheadersin IIS toreflectnamesintoWSDL

•forHTTP andHTTPS

•Specifydifferent URIs forlisteningandexposingin WSDL

<endpointaddress="https://www.tt.com/TheUriIWantInWSDL" listenUri="http://localhost/TheActualUriServiceListensToOnThisBox" ...>

•Considerexposinga staticWSDL whichdocumentsyourpublishedinterfaceversion

21

WSDL & Metadata –Solutions II

•Multiple IIS site bindings result in multiple base addresses

•WCF only supports a single base address in this scenario

•fix yourself in .NET 3.0 with custom ServiceHostFactory

•.NET 3.5 supports <baseAddressPrefixFilters>

•pass-through filter which provides a mechanism to pick the appropriate IIS bindings

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WSDL & Metadata -Samples<bindings><binding protocol="http”bindingInformation="*:80:www.thinktecture.com" /><binding protocol="https" bindingInformation="*:443:www.thinktecture.com" /></bindings>

<serviceHostingEnvironment>

<baseAddressPrefixFilters>

<add prefix="http://thinktecture.de/"/>

<add prefix="http://thinktecture.com"/>

</baseAddressPrefixFilters>

</serviceHostingEnvironment>

<%@ ServiceHostLanguage= "C#" Service="ProductCatalog" Factory="Thinktecture.ServiceModel.Activation.FlatWsdlServiceHostFactory" %>

.svc fileapp/web config

applicationHost.config(IIS7)

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Large Data -Problems

•Myserviceeatsa lotofmemoryandchokestheCPU whensending/receivinglarge data

•Biggermessagesaremakingmycommunicationreallyslow

•I havearbitrary, non-structureddatatotransfer

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Large Data –Solutions I

•WCF supportsMTOM forencodingbinarydata

•MTOM especiallyusefulforinterop

•ChunkingchannelsavailableasSDK & communitysamples

•enablessendingchunksofdatainsteadofonesinglepiece

•transparentlyworkswithdifferent transportsasa bindingelement

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Large Data –Solutions II

•Considerusingstreamingfortransferingabitrarydata

•requirescertaincontractshape

•Stream

•Message

•Streamassinglebodyin MessageContract

•worksoveranytransportbesidesMSMQ

•workswithtransportandmixed-modesecurity

•still watchout forquotas

•powerful withweb programmingmodel

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Large Data -Samples

[ServiceContract]

public interface IVideoPlayer

{

[OperationContract]

[WebGet(UriTemplate= "videos/{videoID}")]

[WebContentType(MimeType= "video/x-ms-wmv")]

StreamPlay(string videoID);

}WebServiceHostwebHost= new WebServiceHost(typeof(VideoPlayerService));WebHttpBindingbinding = new WebHttpBinding();binding.TransferMode= TransferMode.Streamed;webHost.AddServiceEndpoint(typeof(IVideoPlayer),binding,"http://localhost:7777/Services/player");

Service contract

HostClient

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Performance/Throughput-Problems

•SomehowmyentireWCF-basedapplicationis‚slow‘

•Hosting myWCF servicein IIS seemsnot toperformwell underhighload

•I cannotseemtogeta highthroughputwhenclientstalk tomyservicevia HTTP

•All thatdataisbeingtransferredagainandagain, itmakesmysystemslow

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Performance/Throughput–Solutions

•Configuring throttling can heal a lot (look there!)

•.NET 3.5 SP1 provides asynchronous HTTP module & handler for hosting WCF in IIS for better behavior

•Client-side HTTP communication is limited to 2 concurrent connections to a server

•configurable through System.Net

•Cache, cache, cache!

•try to use caching intensively (but wisely) to save unnecessary round-trips

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Performance/Throughput-Samples<system.net><connectionManagement><add address="*" maxconnection="20"/></connectionManagement></system.net>

public List<Episode> ListEpisodes()

{IDataCachecache = DataCacheFactory.CreateInstance();

List<Episode> episodes = cache.Get<List<Episode>>(CacheConstants.AllEpisodes);

if (episodes == null)

{

varepisodeList= mediaLogic.ListAllEpisodes();

episodes = EpisodeDataMapper.MapAllEpisodes(episodeList);

cache.Add(CacheConstants.AllEpisodes, episodes);

}

return episodes;

}

public interface IDataCache

{

void Add(string key, object cacheItem);

TCacheItemGet<TCacheItem>(string key);

void Remove(string key);

}

app/web.configE.g. service facade

Caching lib

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Performance/Throughput–Cache Solution

•Cache shouldbeabstractedfromactualcacheproduct/implementation

•Genericinterfacewithdifferent implementations

•local, in-proccache

•distributedcache

•ASP.NET‘sweb cachecanalso beusedoutside ofASP.NET

•Distributed cachesnecessaryforfarmandscale-out scenarios

•MemcacheD

•SharedCache

•‚Velocity‘

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Special Case: Tracing

•Useit!Itcansave your… J

•Ifthingsgowrongandyouhavenocluewhy: trace!

•But do not overuseitwhenin production

•wrongusagecanmeansevereoverhead

•Configuredvia configfile

•canbemanipulatedvia code, but onlythroughWMI

•DidI alreadysaytracingcansave your…?

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Tracing-Sample<system.diagnostics><sources><sourcename="System.ServiceModel" switchValue="Warning" propagateActivity="true"><listeners><addtype="System.Diagnostics.DefaultTraceListener" name="Default" /><addname="ServiceModelTraceListener" /></listeners></source></sources><sharedListeners><addinitializeData=„MyService_Trace.svclog"type="System.Diagnostics.XmlWriterTraceListener, …"name="ServiceModelTraceListener" traceOutputOptions="Timestamp" /></sharedListeners><traceautoflush="true" /></system.diagnostics>

$ms= get-wmiobject-class "AppDomainInfo" -namespace "root\servicemodel" -computername"." | where{$_.Name -eq"MyWCFHost.exe"}

$ms.TraceLevel= "Warning, ActivityTracing"

$ms.Put()

<system.serviceModel>

<diagnosticswmiProviderEnabled="true"/>

…

app/web.configPS script

app/web.config

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Resources

•Avoiding problems with the using statement

•http://msdn.microsoft.com/en-us/library/aa355056.aspx

•Custom encoders

•http://msdn.microsoft.com/en-us/library/ms751486.aspx

•http://blogs.msdn.com/drnick/archive/2006/05/16/598420.aspx

•Tracing

•http://msdn2.microsoft.com/en-us/library/ms732023.aspx

•http://msdn2.microsoft.com/en-us/library/aa751795.aspx

•http://msdn2.microsoft.com/en-us/library/ms733025.aspx

•http://msdn2.microsoft.com/en-us/library/aa751917.aspx

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Resources

•Setting upIIS SSL hostheaders

•http://www.microsoft.com/technet/prodtechnol/WindowsServer2003/Library/IIS/596b9108-b1a7-494d-885d-f8941b07554c.mspx

•http://blogs.iis.net/thomad/archive/2008/01/25/ssl-certificates-on-sites-with-host-headers.aspx

•baseAddressPrefixFilter

•http://msdn.microsoft.com/en-us/library/bb924492.aspx

•Chunkingchannel

•http://code.msdn.microsoft.com/WCFResources/Release/ProjectReleases.aspx?ReleaseId=1546

35

Resources

•AsynchronousWCF HTTP Module/Handler forIIS7 forBetterServer Scalability

•http://blogs.msdn.com/wenlong/archive/2008/08/13/orcas-sp1-improvement-asynchronous-wcf-http-module-handler-for-iis7-for-better-server-scalability.aspx

•WCF bindings& more

•http://www.noemax.com

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Resources

•We have code solutions for some WCF problems, for free of course

•Thinktecture.ServiceModel

•èEmail Christian Weyer

•christian.weyer@thinktecture.com

•Weblog Christian Weyer

•http://blogs.thinktecture.com/cweyer

•thinktecture

•http://www.thinktecture.com

37

http://www.thinktecture.com/

christian.weyer@thinktecture.com

http://blogs.thinktecture.com/cweyer/

In-depth support and consulting for software architects and developers

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