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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 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. It also allows you to restrict restrict API consumers to only subscribe to sandbox, and then go through an approval process to go to the next level of subscription.

Configuring the Business Process Server

1. Download WSO2 Business Process Server.  

2. Set an offset of 2 to the default BPS port in <BPS_HOME>/repository/conf/carbon.xml file. This prevents port conflicts that occur when you start more than one WSO2 product on the same server. Also see Changing the Default Ports with Offset.

   Code Block
   language xml
   <Offset>2</Offset>

   Tip

   Tip: If you change the BPS port offset to a value other than 2 or run the API Manager and BPS on different machines (therefore, want to set the hostname to a different value than localhost), you do the following: Search and replace the value 9765 in all the files (.epr, .wsdl files inside the ZIP archives) inside <APIM_HOME>/business-processes folder with the new port. Zip the files you unzipped earlier and deploy the newly created zip file in BPS as explained in the steps below. Search and replace port 9445 in <AM<APIM_HOME>/repository/deployment/server/jaggeryapps/admin-dashboard/site/conf/site.json file.

   Tip

   Tip: Did you change the default port of the API Manager rather than the BPS? If so, be sure to do the following: Search and replace the value 8243 in all the files (.epr, .wsd wsdl etc.) inside the ZIP archives inside <APIM_HOME>/business-processes folder with the new port. Change the port in the following property in the <APIM_HOME>/repository/deployment/server/synapse-configs/default/proxy-services/workflowcallbackService.xml file. Code Block <address uri="https://localhost:9444/store/site/blocks/workflow/workflow-listener/ajax/workflow-listener.jag" format="rest"/>

3. Copy the following file from <APIM_HOME>/business-processes/epr to <BPS_HOME>/repository/conf/epr folder. If the <BPS_HOME>/repository/conf/epr folder isn't there, please create it.

   • SubscriptionService.epr
   • SubscriptionCallbackService.epr

4. Start the BPS server and log in to its management console (https://<Server Host>:9443+<port offset>/carbon).  

5. Select Add under the Processes menu and upload t he the <APIM_HOME> /business-processes/subscription-creation/BPEL/SubscriptionApprovalWorkFlowProcess_1.0.0.zip file to BPS. This is the business process archive file.
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6. Similarly, upload Select Add under the Human Tasks menu and upload <APIM_HOME>/business-processes/subscription-creation/HumanTask/SubscriptionsApprovalTask-1.0.0.zip to BPS. This is the human task archived file.

Engaging the WS Workflow Executor in the API Manager

First, enable the API subscription workflow.

1. Log in to APIM admin console (https://<Server Host>:9443/carbon) and select Browse under Resources.
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2. Go to /_system/governance/apimgt/applicationdata/workflow-extensions.xml resource, disable 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).  

   Code Block
   language html/xml
   <WorkFlowExtensions> <!--SubscriptionCreation executor="org.wso2.carbon.apimgt.impl.workflow.SubscriptionCreationSimpleWorkflowExecutor"/--> <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>

   The application creation WS Workflow Executor is now engaged.

3. 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.

4. Note the message that appears if the BPEL is invoked correctly, saying that the request is successfully submitted. 

5. Log in to the Admin Dashboard Web application (https://<Server Host>:9443/admin-dashboard), list all the tasks for API subscription and approve the task. It resumes the BPEL process and completes the API subscription.

6. Go 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:

   Code Block
   language html/xml
   <soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:wor="http://workfloww orkflow.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 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 under the callBackURL property in the api-manager.xml.