Routing service

The Routing Service is a generic SOAP broker that acts as a message router. The main functionality of the routing service is the ability to route messages according to their content, which allows a message to be forwarded to a client connection point based on a value within the message itself, in the message header or body.

The services router is implemented as a Windows Communication Foundation (WCF) service in the System.ServiceModel.Routing namespace. The routing service exposes one or more service ends that receive messages and then routes each message to one or more client ends depending on the content of the message. The service provides the following features:

·         Content based routing

o    Service aggregation

o    Service version control

o    Priority Routing

o    Dynamic configuration

·         Protocol bridge

·         SOAP processing

·         Advanced Error Control

·         backup connection points

Although it is possible to create an intermediate service that achieves one or more of these objectives, this type of implementation is often linked to a specific solution or scenario and cannot be applied directly to new applications.

The routing service provides a generic, dynamically configurable and connectable SOAP broker that is compatible with WCF channel and service models and allows you to perform content-based routing of SOAP-based messages.

Content based routing

Content-based routing is the ability to route a message based on one or more values contained within the message. The routing service inspects each message and routes it to the destination connection point based on the content of the message and the routing logic created. Content-based routing provides a basis for service aggregation, service version control and priority routing.

To implement content-based routing, the routing service relies on the MessageFilter implementations that are used to match specific values within the messages to be routed. If a MessageFilter matches a message, the message is routed to the destination endpoint associated with the MessageFilter . Message filters are grouped together in filter tables ( FilterTableCollection ) to build complex routing logic. For example, a filter table could contain five filters of mutually exclusive messages that cause messages to be routed to only one of the five destination connection points.

The routing service allows you to configure the logic used to perform content-based routing, as well as dynamically update the routing logic at runtime.

Through the grouping of message filters into filter tables, a routing logic can be created that allows you to manage various routing scenarios, such as:

Service aggregation

Service version control

Priority Routing

Dynamic configuration

For more information about message filters and filter tables, see Introduction routing and message filters .

Service aggregation

Using content-based routing, you can expose a connection point that receives messages from external client applications, and then routes each message to the appropriate internal connection point based on a message value. This is useful for providing a specific connection point for various back-end applications and also presenting an application connection point to customers while factoring their application into various services.

Service version control

When you migrate to a new version of the solution, you may have to keep the old version in parallel to serve existing customers. Often, this requires that clients connecting to the latest version use a different address when communicating with the solution. The routing service allows you to expose a service connection point that serves both versions of the solution by routing the messages to the appropriate solution based on the specific information of the version contained in the message. For an example of this type of implementation, see How To: Service Version .

Priority Routing

By providing a service for several customers, you can have a service level contract with some partners that requires that all data from these partners be processed separately from that of other customers. Using a filter that searches for specific customer information included in the message, you can easily route messages from specific partners to a connection point created to meet the requirements of your service level contract.

Dynamic configuration

To support vital systems for a mission, where messages must be processed without any service interruption, it is vital that you can modify the configuration of components within the system during runtime. To enable this need, the routing service provides an IExtension <T> implementation , RoutingExtension , which allows you to perform a dynamic update of the routing service configuration during runtime.

For more information about the dynamic configuration of the routing service, see Introduction routing .

Protocol bridge

One of the challenges in intermediate scenarios is that internal endpoints may have different SOAP or transport version requirements than the endpoint at which messages are received. To support this scenario, the routing service can shorten the protocols, including the processing of the SOAP message to MessageVersion required by the destination endpoints. In this way, one protocol can be used for internal communication, while the other is used for external communication.

To support the routing of messages between endpoints with different transports, the routing service uses links provided by the system that allow the service to shorten protocols that are not equal. This occurs automatically when the service connection point exposed by the routing service uses a different protocol than that of the client connection points to which messages are routed.

SOAP processing

A common routing requirement is the ability to route messages between endpoints with different SOAP requirements. To support this requirement, the routing service provides a SoapProcessingBehavior that automatically creates a new MessageVersion that meets the requirements of the destination connection point before the message is routed to it. This behavior also creates a new MessageVersion for any response message before returning it to the requesting client application, to ensure that the MessageVersion of the response matches that of the original request.

For more information about SOAP processing, see Introduction routing .

Error control

In a system composed of distributed services that rely on network communications, it is important to ensure that communications within the system are resistant to transient network errors. The routing service implements an error control that allows you to manage many cases of communication failures that might otherwise cause a disruption of the service provision.

If the routing service finds a CommunicationException class while trying to send a message, error handling will be activated. These exceptions usually indicate that a problem was encountered while trying to establish communication with the defined client endpoint, such as EndpointNotFoundException , ServerTooBusyException or CommunicationObjectFaultedException . The error control code will also detect and attempt to re-send when a TimeoutException occurs, which is another common type of exception that CommunicationException is not derived .

For more information about error control, see Introduction routing .

backup connection points

In addition to the destination client endpoints associated with each filter definition in the filter table, you can also create a list of reserve endpoints to which the message will be routed in the event of a transmission error. If an error occurs and a reserve list is defined for the filter entry, the routing service will attempt to send the message to the first end defined in the list. If this transmission attempt is not successful, the service will test the next connection point, and continue this process until the transmission attempt is correct, return an error not related to the transmission or all connection points in the list reserve have returned a transmission error.

For more information about backup endpoints, see Introduction routing and message filters .

Streaming

The routing service can transmit messages correctly if you establish the link to support streaming. However, there are some conditions under which it is necessary to buffer messages:

Multicast (use the buffer to create additional copies of the messages)

Failover (use the buffer in case it is necessary to send the message to a reservation)

System.ServiceModel.Routing.RoutingConfiguration.RouteOnHeadersOnly is false (use the buffer to present MessageFilterTable with a MessageBuffer so that filters can inspect the body)

Dynamic configuration