Abort processing policy

Aborting the processing

The ability to terminate a response gracefully is of importance in a number of cases such as error handling or business logic. Using the return-response policies short-circuits the request and yields a response that often does not originate from the backend. Consider what general situations may make sense without shifting too much business logic into APIM.

  • Open the Finds Pets by tags operation in the Swagger Petstore API. This is a deprecated operation, making it ideal for demonstrating how to return a custom error response.
  • Feel free to test it first, use a tag of ‘photo’ or similar - you should get an empty response back.
  • Open the Code View.
  • Add the inbound policy to test for a condition (just true for our example) and return an error.
  • Invoke the API.

  • Observe the 500 error.

    <inbound>
    <base />
    <choose>
        <when condition="@(true)">
            <return-response response-variable-name="existing response variable">
                <set-status code="500" reason="Internal Server Error" />
                <set-header name="failure" exists-action="override">
                    <value>failure</value>
                </set-header>
                <set-body>Internal Server Error</set-body>
            </return-response>
        </when>
    </choose>
</inbound>

    APIM Policy Abort Response

    Clean Up

    Now that you have seen how to gracefully terminate a request with a response, it is time to clean up the code to prevent a downstream impact in subsequent labs. Please remove the <choose> logic above to let all requests flow again, then save the changes.