invokeFunction-Link IoT Edge(IoT Edge)-阿里云帮助中心

Use this API to invoke a specified function.

Description

Both function invocation and publishing a message can be used to pass messages between processes (functions). The differences are as follows:

Function invocation is bi-directional. The caller sends a message to the callee and receives a return message after the callee processes it.
Publishing a message is one-way. The sender does not need a return message from the callee.

invokeFunction(params, callback)

Parameter	Type	Description
params	object	The parameter object. For the required parameters, see Table params parameter description.
callback(err, data)	function	The callback function. It follows standard JavaScript practices. For details, see Table callback parameter description.

Table 1. params parameter
Parameter	Type	Description
serviceName	String	The service name. This is the name of the service to which the function belongs in Alibaba Cloud Function Compute.
functionName	String	The function name. This is the name of the function set in Alibaba Cloud Function Compute.
invocationType	String	The invocation type. Sync: Synchronous invocation. Async: Asynchronous invocation. The default is synchronous invocation.
payload	String\|Buffer	The input for the function.

Table 2. callback parameter
Parameter	Type	Description
err	Error	If the invocation is successful, `err` is `null`. If the invocation fails, `err` contains the error message.
data	object	The return value of the invoked function.

Invocation examples

Caller function example

This example shows how to call the helloworld function in the EdgeFC service.

'use strict';

const leSdk = require('linkedge-core-sdk');
const fc = new leSdk.FCClient();

module.exports.handler = function (event, context, callback) {
  var ctx = {
    custom: {
      data: 'Custom context from Invoker',
    },
  };
  var invokerContext = Buffer.from(JSON.stringify(ctx)).toString('base64');
  var invokeParams = {
    serviceName: 'EdgeFC',
    functionName: 'helloworld',
    invocationType: 'Sync',
    invokerContext: invokerContext,
    payload: 'String message from Invoker.',
  };
  fc.invokeFunction(invokeParams, (err, data) => {
    if (err) {
      console.log(err);
    } else {
      console.log(data.payload); // Message from helloworld
    }
    callback(null);
  });
};

Callee function example

The following helloworld function code shows how the callee function parses the parameters from the caller and returns a result to the caller.

module.exports.handler = function(event, context, callback) {
  console.log(event);   // String message from Invoker.
  console.log(context); // { requestId: '4', invokerContext: {custom: { data: 'Custom data from Invoker' }}}
  console.log(context.invokerContext.custom.data); // Custom data from Invoker
  console.log('-- hello world');
  callback(null, 'Message from helloworld'); // Return the result to Invoker.
};