Google Cloud Functions Extension

Invoke Node.js function

The following example features an ExtensionCallout policy calling a Google Cloud Functions extension. The extension calls the default "hello world" function included when you enable the Cloud Functions API.

The following Node.js JavaScript is deployed in Cloud Functions for a GCP account. If the request includes a message property, the code returns that. Otherwise, it returns "Hello World!" as its response.

/**
 * Responds to any HTTP request.
 *
 * @param {!express:Request} req HTTP request context.
 * @param {!express:Response} res HTTP response context.
 */
exports.helloWorld = (req, res) => {
  let message = req.query.message || req.body.message || 'Hello World!';
  res.status(200).send(message);
};

This example includes a Google Cloud Functions extension configured with credentials needed to authenticate and get authorized to invoke code on Cloud Functions.

The preceding function code is saved in Cloud Functions as simply helloWorld. The following ExtensionCallout policy configuration code uses this name, along with region and project ID values matching the particulars of the Cloud Functions environment where the function is deployed.

<Action>invoke</Action>
<Input><![CDATA[
  {
    "region" : "us-central1",
    "projectId" : "my-project",
    "functionName" : "hello-world",
    "method" : "POST",
    "payload" : { "message" : "Hello yourself!" }
  }
]]></Input>
<Output parsed="false">function.response</Output>

The following AssignMessage policy captures the response value for debugging purposes.

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<AssignMessage async="false" continueOnError="false" enabled="true" name="Get-Function-Response">
    <DisplayName>Get Function Response</DisplayName>
    <AssignTo type="response" createNew="false"/>
    <Set>
        <Payload contentType="application/json">{function.response}</Payload>
    </Set>
</AssignMessage>

The response to the request above would be like the following:

Hello yourself!

The default value of parsed is true. This example sets parsed="false" in the <Output> tag of the policy, which prevents the policy from parsing the JSON response. For most situations when using the Cloud Functions extension you set parsed="false". See <Output> element for more.

If the Cloud Function returns a JSON response and you set parsed="true", then the response from the extension is an object reference. In order to extract the response from the reference, use the following syntax: {objectName}.{jsonKey}. For example:

function.response.message

Syntax

<Action>invoke</Action>
<Input><![CDATA[
  {
    "region" : "deployment-region",
    "projectId" : "project-id",
    "functionName" : "function-name",
    "method" : "http-method",
    "payload" : { json-payload }
  }
]]></Input>
<Output>function.response</Output>

Example

<Action>invoke</Action>
<Input><![CDATA[
  {
    "region" : "us-central1",
    "projectId" : "my-project",
    "functionName" : "hello-world",
    "method" : "POST",
    "payload" : { "message" : "Hello yourself!" }
  }
]]></Input>
<Output>function.response</Output>