SAP API Management - Fault Rules

 Scenario: You want to send custom message using fault rules in case of Quota error

Steps:

1. Add an instance of Quota in Preflow for incoming request.

2. Modify the code as per requirement.

Code (Allow 2 calls/1 min.)

<Quota async="false" continueOnError="false" enabled="true" xmlns="http://www.sap.com/apimgmt">

  <Allow count="2"/>

  <Interval>1</Interval>

<Distributed>true</Distributed>

<Synchronous>true</Synchronous>

  <TimeUnit>minute</TimeUnit>

</Quota>

3. Add a policy for Assign Message and delete it from flow. Though it is deleted from flow, it will remain under Created Policies.

4. Modify the code as per requirement for Assign Message. 

<!-- This policy can be used to create or modify the standard HTTP request and response messages -->

<AssignMessage async="false" continueOnError="false" enabled="true" xmlns='http://www.sap.com/apimgmt'>

 

<!-- Sets a new value to the existing parameter -->

<Set>

             <Payload contentType="application/json">
                  {
                       "errorCode": "500",
                        "errorMessage": "Quota exceeded. Try again later"}
            </Payload>

</Set>

<IgnoreUnresolvedVariables>false</IgnoreUnresolvedVariables>

<AssignTo createNew="false" type="response"/>

</AssignMessage>

5. Now export the API and Edit APIProxy -> APIProxyEndPoint -> default.xml and add the fault rules as below.

<faultRules>

        <faultRule>

            <name>Quota Error</name>

            <condition>(fault.name = "QuotaViolation")</condition>

            <steps>

                <step>

                    <policy_name>AssignMessage</policy_name>

                      #condition is specified as fault variable - ratelimit.policy_name.failed

                    <condition>ratelimit.QuotaPolicy.failed=true</condition>

                    <sequence>1</sequence>

                </step>

            </steps>

        </faultRule>

    </faultRules>

6. Now zip the APIProxy folder structure and Import in SAP APIM.

7. Test the API.