SAP API Management - Quota Policy - Message Weight

 Scenario: You want to limit API calls/time interval based on message weight. 

Steps:

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

2. Create a Java Script to set Message weight based on call type. As GET call will consume less resources than POST, we will assign a message weight of 1 for GET and 2 for POST. 

Code:

var callType = context.proxyRequest.method;

context.setVariable("messageWeight","1");

if(callType == 'POST')

{

    context.setVariable("messageWeight","2");

}

3. Modify the code for JS policy.

Code:

<!-- this policy allows us to execute java script code during execution of an API Proxy -->

<Javascript async="false" continueOnError="false" enabled="true" timeLimit="200" xmlns='http://www.sap.com/apimgmt'>

<!-- contains the name of the main code file -->

<ResourceURL>jsc://setMessageWeight.js</ResourceURL>

</Javascript> 

4. Modify the code for Quota policy

Code (Allow 4 calls/min.  So, it will allow 4 calls/min for GET, 2 calls/min for POST.)

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

    <Identifier ref="request.queryparam.app"></Identifier>

    <MessageWeight ref="messageWeight"></MessageWeight>

  <Allow count="4"/>

  <Interval>1</Interval>

<Distributed>true</Distributed>

<Synchronous>true</Synchronous>

  <TimeUnit>minute</TimeUnit>

</Quota>

5. Test the API 

In this case, during 5th GET call within a minute for the same client application, the below response is received.

Now,  during 3rd POST call within a minute for the same client application, the below response is received.