WebSphere brand IBM WebSphere Telecom Web Services Server, Version 7.1

Access Gateway fault flow

When errors are detected during the default message processing flow, the Access Gateway invokes certain mediation primitives in a set sequence.

Upon completion of the default message flow, the response object is returned through the SCA export invocation, as the Web service response. If a failure occurs during the execution of the request portion of the flow, then fault handling segment of the flow is invoked.

When handling a Web service response, the response is always returned to the requester despite faults within the flow. This ensures consistency with the backend system. Errors during a request flow are signified by the output of the mediation primitive being placed on its fault terminal. This fault terminal will be wired to the fault processing segment of the flow, which returns the error response to the requester.

The Access Gateway performs a transformation step, in order to convert a fault to a WSDL defined error type in a fault situation. This step is performed just prior to returning the error response to the Web service client, and it matches the client expected output from the WSDL interface.
Figure 1. Access Gateway Fault FlowFault flow
The default handling flow segment executes the following mediation primitives in sequence for a request flow. In a response flow, only the highlighted mediation primitives are included.
  1. The Network Statistics mediation primitive is called to log statistics about the fault event.
  2. If message capture is enabled by policy, the Message Interceptor mediation primitive logs the actual fault object being returned to the requester.
  3. The JMX Notification mediation primitive emits a JMX notification, which contains information about the fault.
  4. If there is a policy specifying that a common base event should be emitted, the CEI event emitter mediation primitive emits the common base event. This enables the fault information to be picked up by external security or monitoring systems, such as Tivoli products.
  5. An XSLT transformation is performed to create an appropriate WSDL-default fault from the SMO. This provides an appropriate fault response for the caller. The XSLT transformation mediation primitive is provided with the WebSphere® ESB platform.
    Note: The XSLT transform file has changed in WebSphere ESB, which allows necessary porting to account for the change in the runtime.

    Any outgoing requests that originate from within a service implementation–for example, Web service notifications– must also pass through the TWSS Access Gateway. The request is subject to standard message processing logic. This allows for logging, calculation of network statistics, and other policy-driven actions. You can also choose to create a custom flow, which is slimmed down for outbound requests. The requests should indicate, within the SOAP header, that the Access Gateway is to perform as a Web service intermediary but not as a final destination for the request.




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