Enforce Throttling and Resource Access Policies

Throttling allows you to limit the number of hits to an API during a given period of time, typically to protect your APIs from security attacks and your backend services from overuse, regulate traffic according to infrastructure limitations and to regulate usage for monetization. For information on different levels of throttling in WSO2 API Manager (WSO2 API-M), see Throttling tiers.

After you created, published, and subscribed to the API, let's see how the API Gateway enforces throttling and resource access policies to the API. 

1. Sign in to the API Store and select the PhoneVerification API.

   

2. Go to the Default Application, click the Production Keys tab and generate an access token. If you already have an access token for the application, you have to regenerate it after 1 hour. 
   
   Let's invoke this API. 

3. Click on the API, then go to its API Console tab and expand the GET method.
   

4. Give values to the parameters and click Try it out to invoke the API.
   

   Note the response that appears in the API Console. As we used a valid phone number in this example, the response returns as valid.
   
   Note that you subscribed to the API on the Bronze throttling tier. The Bronze tier allows you to make a 1000 calls to the API per minute. If you exceed your quota, you get a throttling error as shown below.
   
   Let's try to invoke the API using an unavailable resource name.

5. Go to the API's Overview page in the API Store and get the API's URL.
   

6. Install cURL or any other REST client.

7. Go to the command-line invoke the API using the following cURL command. 

   curl -k -H "Authorization :Bearer <access token in step 3>" '<API's URL in step 9>/CheckPhoneNum?PhoneNumber=18006785432&LicenseKey=0'

   Note that the PhoneVerification API's resource name is CheckPhoneNumber, but we use an undefined resource name as CheckPhoneNum. Here's an example:

   curl -k -H "Authorization :Bearer 63cc9779d6557f4346a9a28b5cfd8b53" 'https://localhost:8243/phoneverify/1.0.0/CheckPhoneNum?PhoneNumber=18006785432&LicenseKey=0'

8. Note that the call gets blocked by the API Gateway with a 'no matching resource' message. It doesn't reach your backend services as you are trying to access a REST resource that is not defined for the API.
   

You have seen how the API Gateway enforces throttling and resource access policies for APIs.