Lambda Function 如何呼叫另一個 Lambda Function

Lambda Function 如何呼叫另一個 Lambda Function?

實務上有些情況我們會需要從某個Lambda function去呼叫另一個Lambda function起來做事

例如, 處理客戶訂單的OrderLambdaFunction 處理完客戶訂購的請求後, 需要喚起處理付款的PaymentLambdaFunction

要達到這個目的有兩個方法

Lambda Invoke

這個方法最簡單, 使用aws-sdk就能呼叫另一個Lambda Function,
但我們需要添加合適的Policy到OrderLambdaFunction使用的Role中

   {
        "Sid": "Stmt1234567890",
        "Effect": "Allow",
        "Action": [
            "lambda:InvokeFunction"
        ],
        "Resource": "*"
    }

步驟1: IAM > Policies > Create Policy > JSON(建立Customized Policy)
步驟2: IAM > Roles > Your_Lambda_Role > Attach Policy

OrderLambdaFunction

exports.handler = (event, context, callback) => {
    // TODO implement
    
    lambda.invoke({
      FunctionName: 'PaymentLambdaFunction',
      Payload: JSON.stringify({}, null, 2) // pass params
    }, function(error, data) {
        if (error) {
          console.log(error);
        }
        if(data.Payload){
          console.log(data.Payload);
        }
    });

    callback(null, 'Hello from Lambda');
};

var aws = require('aws-sdk');
var lambda = new aws.Lambda({
  region: 'us-east-1' //change to your region
});

PaymentLambdaFunction

exports.handler = (event, context, callback) => {
    // TODO implement
    console.log("Hello from Lambda ");
    callback(null, { Payload: { "data": "123"}});
};

SNS

這個作法是讓SNS作為兩個Lambda之間的溝同橋梁
定義好溝通的Topic之後, 只要其中一方發布訊息, SNS就能夠觸發訂閱的那方起來做事


RequestPayTopic

首先, 在Simple Notification Service需要建立一條Topic, 讓兩方可以做溝通

OrderLambdaFunction

發布訊息到指定的Topic: RequestPayTopic

Source code

exports.handler = (event, context, callback) => {
    // TODO implement
    var sns = new aws.SNS();
    console.log('start sns function')
    sns.publish({
        Message: 'Process the bill',
        TopicArn: process.env.TopicArn
    }, function(err, data) {
        if (err) {
            console.log(err.stack);
            return;
        }
        console.log('push sent');
        console.log(data);

    });
    
    callback(null, 'Hello from Lambda');
};

var aws = require('aws-sdk');

Policy

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "sns:Publish"
      ],
      "Resource": [
        "*"
      ]
    }
  ]
}

PaymentLambdaFunction

訂閱 RequestPayTopic, 作為Lambda的觸發條件, SNS會在收到訊息後去觸發PaymentLambdaFunction