Engage a new Throttling Policy at Runtime

The steps below show how to engage a throttling policy to an API at runtime.

1. Write a new throttling policy. For example, the following sample throttling policy points to a backend service and allows 1000 concurrent requests to a service.

   <wsp:Policy xmlns:wsp="http://schemas.xmlsoap.org/ws/2004/09/policy"
   xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd"
   xmlns:throttle="http://www.wso2.org/products/wso2commons/throttle"
               wsu:Id="WSO2MediatorThrottlingPolicy">
       <throttle:MediatorThrottleAssertion>
           <throttle:MaximumConcurrentAccess>1000</throttle:MaximumConcurrentAccess>
           <wsp:Policy>
               <throttle:ID throttle:type="IP">other</throttle:ID>           
           </wsp:Policy>
       </throttle:MediatorThrottleAssertion>
   </wsp:Policy>

2. Log in to the API Manager's management console ( https://localhost:9443/carbon ) and click the Resource > Browse menu to view the registry.
   
3. Click the /_system/goverence/apimgt/applicationdata path to go to its detailed view.
   
   

4. In the detail view, click the Add Resource link.
   

5. Upload the policy file to the server as a registry resource.

6. In the management console, select the Service Bus > Source View menu.
   

7. The configurations of all APIs created in the API Manager instance opens. To engage the policy to a selected API, add it to your API definition. In this example, we add it to the login API.

   <api xmlns="http://ws.apache.org/ns/synapse" name="_WSO2AMLoginAPI_" context="/login">
       <resource methods="POST" url-mapping="/*">
           <inSequence>
               <send>
                   <endpoint>
                       <address uri="https://localhost:9493/oauth2/token"/>
                   </endpoint>
               </send>
           </inSequence>
           <outSequence>
               <send/>
           </outSequence>
       </resource>
       <handlers>
    <handler class="org.wso2.carbon.apimgt.gateway.handlers.throttling.APIThrottleHandler">
          <property name="id" value="A"/>
          <property name="policyKey" value="gov:/apimgt/applicationdata/throttle.xml"/>
          </handler> 
   <handler class="org.wso2.carbon.apimgt.gateway.handlers.ext.APIManagerExtensionHandler"/>
       </handlers>
   </api>

   Note: Be sure to specify the same path used in step 5 in the policy key of your API definition. Also, use the same tier name you selected when creating the API as the throttle id in the policy (example <throttle:ID throttle:type ="ROLE">Gold</throttle:ID>).

You have successfully engaged a throttling policy to an API at runtime, without restarting the server.