Copyright © 2003, developerLabs Extending.NET Distributed Applications Stephen Fulcher...

Copyright © 2003, developerLabs

Extending .NET Distributed Applications

Stephen FulcherdeveloperLabs


Topics

General Extensibility Remoting Extensibility


General Extensibility

Custom configuration The .NET configuration hierarchy can be extended arbitrarily New configuration sections can be defined and we can supply handlers for those

sections Programmatic type activation

Configuration metadata can be used to describe types to the satisfaction of the loader

Assembly loading might be required Types activated in this manner must already be compiled into assembly form

Programmatic type generation The CodeDOM namespace includes support for programmatically generating

and compiling types The reflection namespace also includes a technique for creating a type

programmatically


Remoting Extensibility - Overview

Crossing a context, application domain, process or machine boundary requires marshaling

Objects can be marshaled by value of by reference MBROs can be activated by the server or the client

Server activated objects include single-call and singleton Object life-cycle varies by activation type

Singletons use a lease-based lifecycle Client activated objects use a lease-based lifecycle Single-call objects live through a single call


Infrastructure

Object activation requests return an ObjRef instance

The ObjRef is unpacked/unmarshaled into a transparent proxyThe transparent proxy leverages unmanaged

memory to model the server side objectA transparent proxy holds a reference to a

real proxy


Infrastructure

The RealProxy type is abstract, and has a RemotingProxy implementation

The RealProxy type instances take the unmanaged memory block managed by the transparent proxy and turn it into a Message

Messages implement the IMessage interface and basically encapsulate a collection of key-value pairs, an IDictionary reference


Infrastructure

The message is passed from the real proxy to the envoy sink chain

A sink object can operate on the message as part of a chain

Each sink object implements the IMessageSink interface: NextSink AsyncProcessMessage SyncProcessMessage

An envoy sink operates in the context of the client holding the reference to the transparent proxy

The envoy sink chain has a terminator sink at the end that passes off to the client context sink chain


Infrastructure

The message is passed from the real proxy to the context sink chain

Each context sink in the chain gets to operates on a message

The last sink in the context chain is the terminator context sink If the call is simply a cross-context call, the terminator sink passes

the message to the cross-context channel, a lightweight channel If the call target is in a different application domain, process or

machine, the terminator sink passes the message out of the client object context to the channel sink chain

The channel sink chain prepares the message for transport to the remote process/machine


Infrastructure

The first sink in the channel sink chain is the formatter, which implements IFormatter

This sink serializes the message to the initial wire format The platform includes two formatters, SoapFormatter

and BinaryFormatter The message is passed fro the formatter sink to a set of

channel sinks These channel sinks can operate on the serialized

message format before transport The terminator channel sink is the transport sink, which

passes the message off to transport


Infrastructure

On the server side, a reasonably symmetric set of sink chains exist going from the transport wire to the remote object

The transport sink passes to the channel sink chain, which passes to the server context sink chain, which passes to the server object sink chain

The last sink is the Stackbuilder sink, which preps the stack for the call to the remote object

After the call, the server object sinks take the result from the call, pack it into a message, and send it back through the infrastructure to the client


Extensibility Points

Custom ObjRef types Custom proxies

These are classes that derive from RealProxy and replace RemotingProxy

These work for client-side only logic in contrast with something that has part on the client and a part on the server, like encryption/decryption



Custom message types: IMessage In particular, message headers

Custom message sinks: IMessageSinkEnvoy sinksContext sinks



Custom channel sinksFormatter sink: IFormatterChannel sink:

BaseChannelSinkWithProperties, IXXXChannelSink


Resources

BooksAdvanced .NET Remoting, APressMicrosoft .NET Remoting, MSPress

Free stuffSDK docshttp://www.ingorammer.comhttp://www.gotdotnet.comhttp://msdn.microsoft.com

Copyright © 2003, developerLabs Extending.NET Distributed Applications Stephen Fulcher...

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