爲什麼我在使用Callback時無法啓動實例？

Question

我對lambda函數很陌生，如果這個問題很愚蠢，請道歉。下面的代碼工作 第一部分，它啓動EC2實例，但如果我把它鏈接到Alexa的

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

exports.handler = (event, context, callback) => { 


    try{ 

     if (event.session.new) { 
    //New Session 
    console.log("NEW SESSION") 
    } 

    switch (event.request.type){ 
    case "IntentRequest": 
    // > Intent Request 
    console.log(`INTENT REQUEST`) 
    switch(event.request.intent.name){ 

    case "StartecInsatnce": 
     console.log(`Test msg`) 
          var ec2=new aws.EC2({region: 'us-east-1'}); 
     var endpoint= ec2.startInstances({InstanceIds: ['i-0a20b89becb6fcb7e']}, function(err,data) { 
              if (err) console.log(err,err.stack); 
              else console.log(data); 
              context.done(err,data); 
              }); 
           callback(null, "some success message");           


              } 
              break; 
     default: 
      context.fail(`INVALID REQUEST TYPE: ${event.request.type}`) 
    } 
} 
catch(error) { context.fail(`EXCEPTION: ${error}`) } 

} 

所以我用下面的代碼，這雖然發送響應，但無法啓動EC2實例不起作用。請幫助

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

exports.handler = (event, context, callback) => { 


    try{ 

     if (event.session.new) { 
    //New Session 
    console.log("NEW SESSION") 
    } 

    switch (event.request.type){ 

    case "IntentRequest": 
    // > Intent Request 
    console.log(`INTENT REQUEST`) 
    switch(event.request.intent.name){ 

    case "StartecInsatnce": 
    onIntent(event.request, 
     event.session, 
     function callback(sessionAttributes, speechletResponse) { 
      context.succeed(buildResponse(sessionAttributes, speechletResponse)); 
     }); 


     //  callback(null, "some success message");                    

       }//end of inner switch 
              break; 

    default: 
      context.fail(`INVALID REQUEST TYPE: ${event.request.type}`)   
    } 
} 
catch(error) { context.fail(`EXCEPTION: ${error}`) } 
//Helpers 
generateResponse = (sessionAttributes, speechletResponse) => { 
return{ 
    version: "1.0", 
    sessionAttributes: "sessionAttributes", 
    response: "speechletResponse" 
    } 
    } 
} 
function onIntent(intentRequest, session, callback) { 
    var intent = intentRequest.intent, 
    intentName = intentRequest.intent.name; 
    var cardTitle = intent.name; 
    console.log(`Test msg`) 
    var sessionAttributes={} 
     var shouldEndSession = false; 
    speechOutput = "instance started."; 
     var ec2=new aws.EC2({region: 'us-east-1'}); 
     var endpoint= ec2.startInstances({InstanceIds: ['i-0a20b89becb6fcb7e']}, function(err,data) { 
              if (err) console.log(err,err.stack); 
              else console.log(data); 
              context.done(err,data); 

              }); 
              console.log("end="+endpoint) 
    callback(sessionAttributes, 
    buildSpeechletResponse(cardTitle, speechOutput, shouldEndSession)); 

    } 

    function buildSpeechletResponse(title, output, shouldEndSession) { 
    return { 
     outputSpeech: { 
     type: "PlainText", 
     text: output 
     }, 
     card: { 
     type: "Simple", 
     title: "SessionSpeechlet - " + title, 
     content: "SessionSpeechlet - " + output 
     }, 

     shouldEndSession: shouldEndSession 
    }; 
    } 
function buildResponse(sessionAttributes, speechletResponse) { 
    return { 
     version: "1.0", 
     sessionAttributes: sessionAttributes, 
     response: speechletResponse 
    }; 
    } 

Answer 1

您正在對待異步代碼，就像它是同步代碼一樣。

var endpoint= ec2.startInstances({InstanceIds: ['i-0a20b89becb6fcb7e']}, function(err,data) { 
             if (err) console.log(err,err.stack); 
             else console.log(data); 
             context.done(err,data); 
             }); 
          callback(null, "some success message");           

這段代碼做了什麼？

爲了：

• 建立並啓動異步請求ec2.startInstances
• 立即調用callback()
• 也許允許API請求以完成
• 也許達到context.done()。目前還不清楚你爲什麼同時使用和callback()，但也許我忽略了一些東西。

但好像你需要從ec2.startInstances調用後續函數裏面回調，因此它被延遲，而不是外面，在那裏將前ec2.startInstances完成執行，因爲你還沒有返回控制到事件循環。