Example 4: Using a Function to Invoke a Subfunction

Scenario

This section uses Python as an example to describe how to invoke a subfunction by using a function.

For details about how to call APIs, see Calling APIs.

Prerequisites

An agency with the FunctionGraph Administrator or Tenant Administrator permission has been created.

Constraints

Ensure that the function and the subfunction are created in the same region.

Overall Procedure

1. Create a subfunction.
2. Create a function.
3. Use the function to invoke the subfunction.

Step 1: Create a Subfunction

Create a subfunction on the FunctionGraph console. Set parameters by referring to Figure 1 and retain the default values for other parameters.

Figure 1 Setting parameters

Step 2: Create a Function

1. Create a function on the FunctionGraph console. Select an agency with the FunctionGraph Administrator or Tenant Administrator permission. Select the region as required. In addition, set parameters as shown in Figure 2 and retain the default values for other parameters.
   Figure 2 Setting parameters
   
2. On the Code tab page, copy the following sample code to the code editing area, replace the fields, and click Deploy. For details about the fields, see Table 1.

   import json
   import requests
   def handler (event, context):
       token = context.getToken()
       project_id = context.getProjectID()
       urn = 'urn:fss:xx-xxxxx-x:xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx:function:xxx:subfunction:latest'  # Subfunction URN, which can be queried on the right of the topology on the subfunction details page.
       url = 'https://functiongraph.{region_id}.{external_global_domain_name}/v2/%s/fgs/functions/%s/invocations' % (project_id,urn) 
       headers = {
           "x-auth-token": token,
           "content-type": 'application/json'
       }
       body = {"k":"v"}
       resp = requests.post(url, json=body, headers=headers, verify=False)
       print(resp.text)
       return {
           "statusCode": 200,
           "isBase64Encoded": False,
           "body": json.dumps(event),
           "headers": {
               "Content-Type": "application/json"
           }
       }

   Table 1 Sample code field description

   Field	Description
   region_id	Region ID. For details, set this field based on the region where the function is located. For details, see the Region ID column in Regions and Endpoints. For example, if the region is CN East-Shanghai1, enter cn-east-3.
   external_global_domain_name	Global domain name. Enter myhuaweicloud.com.

Step 3: Use the Function to Invoke the Subfunction

1. On the details page of the function, click Test. The Configure Test Event box is displayed. Create a test event using the default blank template and click Create.
2. Click Test in the code editing area to invoke the function.
3. View the execution result.
   • The execution result of the function is Execution successful and 200 is returned.
     Figure 3 Function execution record
     
   • The Logs tab page shows details about subfunction invocation.
     Figure 4 Subfunction execution record