Adding an API Subscription Workflow

This section explains how to attach a custom workflow to the API subscription operation in the API Manager. First, see Workflow Extensions for information on different types of workflows executors.

Attaching a custom workflow to API subscription enables you to add throttling tiers to an API that consumers cannot choose at the time of subscribing. Only admins can set these tiers to APIs. When a consumer subscribes to an API, he/she has to subscribe to an application in order to get access to the API. However, when API subscription workflow is enabled, when the consumer subscribes to an application, it initially is in the On Hold state, and he/she can not use the API, using its production or sandbox keys, until their subscription is approved.

Configuring the API Manager

Open the <API-M_HOME>/repository/deployment/server/jaggeryapps/admin/site/conf/site.json file and configure "workFlowServerURL" under "workflows" to point to the BPS server (e.g. "workFlowServerURL": "https://localhost:9445/services/")

Engaging the WS Workflow Executor in the API Manager

First, enable the API subscription workflow.

Sign in to API Manager Management Console (https://<Server Host>:9443/carbon) and select Browse under Resources.
Go to the /_system/governance/apimgt/applicationdata/workflow-extensions.xml resource, disable the Simple Workflow Executor and enable WS Workflow Executor. Also specify the service endpoint where the workflow engine is hosted and the credentials required to access the said service via basic authentication (i.e., username/password based authentication).
```
<WorkFlowExtensions>
 
...
    <SubscriptionCreation executor="org.wso2.carbon.apimgt.impl.workflow.SubscriptionCreationWSWorkflowExecutor">
         <Property name="serviceEndpoint">http://localhost:9765/services/SubscriptionApprovalWorkFlowProcess/</Property>
         <Property name="username">admin</Property>
         <Property name="password">admin</Property>
         <Property name="callbackURL">https://localhost:8243/services/WorkflowCallbackService</Property>
    </SubscriptionCreation>
...

</WorkFlowExtensions>
```
Note that all workflow process services of the BPS run on port 9765 because you changed its default port (9763) with an offset of 2.
The application creation WS Workflow Executor is now engaged.
Go to the API Store Web interface and subscribe to an API.
It invokes the API subscription process and creates a Human Task instance that holds the execution of the BPEL until some action is performed on it.
Note the message that appears if the BPEL is invoked correctly, saying that the request is successfully submitted.
Sign in to the Admin Portal (https://<Server Host>:9443/admin ), list all the tasks for API subscription and approve the task. It resumes the BPEL process and completes the API subscription.

Go back to the API Store and see that the user is now subscribed to the API.

Whenever a user tries to subscribe to an API, a request of the following format is sent to the workflow endpoint:

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"xmlns:wor="http://workflow.subscription.apimgt.carbon.wso2.org">
   <soapenv:Header/>
   <soapenv:Body>
      <wor:createSubscription>
         <wor:apiName>sampleAPI</wor:apiName>
         <wor:apiVersion>1.0.0</wor:apiVersion>
         <wor:apiContext>/sample</wor:apiContext>
         <wor:apiProvider>admin</wor:apiProvider>
         <wor:subscriber>subscriber1</wor:subscriber>
         <wor:applicationName>application1</wor:applicationName>
         <wor:tierName>gold</wor:tierName>
         <wor:workflowExternalRef></wor:workflowExternalRef>
         <wor:callBackURL>?</wor:callBackURL>
      </wor:createSubscription>
   </soapenv:Body>
</soapenv:Envelope>

Elements of the above configuration are described below:

Element	Description
apiName	Name of the API to which subscription is requested.
apiVersion	Version of the API the user subscribes to.
apiContext	Context in which the requested API is to be accessed.
apiProvider	Provider of the API.
subscriber	Name of the user requesting subscription.
applicationName	Name of the application through which the user subscribes to the API.
tierName	Throttling tiers specified for the application.
`workflowExternalRef`	The unique reference against which a workflow is tracked. This needs to be sent back from the workflow engine to the API Manager at the time of workflow completion.
callBackURL	The URL to which the Workflow completion request is sent to by the workflow engine, at the time of workflow completion. This property is configured in the `<callBackURL>` element in the `workflow-extensions.xml` registry file