Aws lambda

Serverless

Function as a service
I want to shut down my services at 6 pm.
Integrated with Database.

Build in fault tolerance.
Pricing: only when it is executed.

Create thumbnail function

Amazon ECS

ECS supports docker

Eliminate need to install operate your cluster.

Fleet of docker container

Fargate : managed ECS .
Next step to ECS.

Container as a Service

Aws Technical Professional Bootcamp

Edge location :
Route 53 : navigate to a certain site via edge location.
Regional Cache:
Amazon Elastic Container services
Virtualization to container
Lambda : serverless

Types of EC2
Memory Optimised
Compute optimised
Storage Optimised
GPU optimised
General Optimised

Size : large small xtra large

AMI : bootable operation system and additional software.You can take snapshot.

Families : types .

AWS Auto Scaling

• AWS Auto Scaling

  Before getting start , lets revisit the following topics .

s

EC2

  Create an Elastic Cloud Compute instance . This is like linux server where you are going to deploy your application code . For Example , if you want to host a Web Application which runs on Node.js , you need to install Node.js and run you Web Application .

 a

VPC

Create an Amazon Machine Image of an EC2 instance .

a

AMI 

Create an Amazon Machine Image of an EC2 instance .

a

s

Load Balancer

Application Load Balancer : used for Http and Https

Network Load Balancer : used for TCP,UDP and TLS .

a

s

Auto Scaling Group

 a

a

s

Scaling Policy

 a

a

s

CloudWatch

 a

s

CloudWatch Alarms

 a

 a

S3

Simple storage service . Static files of the application can be placed in S3 to reduce the load on the application .

 a

CloudFront

Simple storage service . Static files of the application can be placed in S3 to reduce the load on the application .

a

Error: Objects are not valid as a React child

Error Blog 

This blog is about the error Error: Objects are not valid as a React child 

Problem Statement

error on start of reactjs application

Error Details 

error Log

ERROR DETAILS 

Error: Objects are not valid as a React child (found: object with keys {TASK_ID, TASK_DESC, TASK_REF, TASK_STATUS, UPDATED_ON}). If you meant to render a collection of children, use an array instead. in div (at task-list.js:22) in TaskList (at App.js:10) in div (at App.js:9) in App (at src/index.js:9) in StrictMode (at src/index.js:8)

Error Code 

You will face this error if you try to convert an array response to json .

router.get('/', function (req, res) { Task.getAllTask(function (err, task) { console.log('controller') if (err) res.send(err); console.log('res', task); res.send( task); }); });

Solution

change the code so that the array is handled .

Code Changes 

wrap the array inside a json .

  

        

    

router.get('/', function (req, res) { Task.getAllTask(function (err, task) { console.log('controller') if (err) res.send(err); console.log('res', task); res.send({'resp':task}); }); });

         

OUTPUT

works 

Thanks for reading . Let me know your thoughts in the comments below    .

TypeError: Class extends value undefined is not a constructor or null

Error Blog 

This blog is about the error TypeError: Class extends value undefined is not a constructor or null

Problem Statement

unable to start reactjs application

Error Details 

error Log

ERROR DETAILS 

Uncaught TypeError: Class extends value undefined is not a constructor or null
    at Module../src/task/task-list.js (task-list.js:5)
    at __webpack_require__ (bootstrap:784)
    at fn (bootstrap:150)
    at Module../src/App.js (App.css?4433:45)
    at __webpack_require__ (bootstrap:784)
    at fn (bootstrap:150)
    at Module../src/index.js (index.css?f3f6:45)
    at __webpack_require__ (bootstrap:784)
    at fn (bootstrap:150)
    at Object.1 (task.js:11)
    at __webpack_require__ (bootstrap:784)
    at checkDeferredModules (bootstrap:45)
    at Array.webpackJsonpCallback [as push] (bootstrap:32)
    at main.chunk.js:1

Error Code 

You will face this error if you have improper syntax in extends React.Component.

import React from 'react';

class TaskList extends React.Component() {

  constructor() {

    super();

    this.state = {

      name: 'React',assetName:"asset name"

    };

  }

 

  render() {

     return (

    <div  >

       Task List

    </div>

  );

  }

}

export default TaskList;

Solution

change the code so that the syntax is proper for extends  . .

Code Changes 

add the following import in your component.ts file .

  

        

     class TaskList extends React.Component  {

         

OUTPUT

works 

Thanks for reading . Let me know your thoughts in the comments below    .

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client

Error Blog 

This blog is about the error Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client

Problem Statement

unable to start node js express application

Error Details 

error Log

ERROR DETAILS 

\node_modules\mysql\lib\protocol\Parser.js:437
      throw err; // Rethrow non-MySQL errors
      ^

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at ServerResponse.setHeader (_http_outgoing.js:470:11)
    at ServerResponse.header (F:\ \study\gitRepo\new\learn\nodejs\expressjs\node_modules\express\lib\response.js:771:10)
    at ServerResponse.send (F:\ \study\gitRepo\new\learn\nodejs\expressjs\node_modules\express\lib\response.js:170:12)
    at ServerResponse.json (F:\ \study\gitRepo\new\learn\nodejs\expressjs\node_modules\express\lib\response.js:267:15)
    at F:\ \study\gitRepo\new\learn\nodejs\expressjs\service\users.js:24:11
    at Query.<anonymous> (F:\ \study\gitRepo\new\learn\nodejs\expressjs\service\task.service.js:20:21)
    at Query.<anonymous> (F:\ \study\gitRepo\new\learn\nodejs\expressjs\node_modules\mysql\lib\Connection.js:526:10)
    at Query._callback (F:\ \study\gitRepo\new\learn\nodejs\expressjs\node_modules\mysql\lib\Connection.js:488:16)
    at Query.Sequence.end (F:\ \study\gitRepo\new\learn\nodejs\expressjs\node_modules\mysql\lib\protocol\sequences\Sequence.js:83:24)
    at Query._handleFinalResultPacket (F:\ \study\gitRepo\new\learn\nodejs\expressjs\node_modules\mysql\lib\protocol\sequences\Query.js:149:8)

Error Code 

You will face this error if you res.send twice in an express js application.

var express = require('express');

var router = express.Router();

var Task = require('./task.service.js');

router.get('/', function(req, res){

   Task.getAllTask(function(err, task) {

      console.log('controller')

      if (err)

        res.send(err);

        console.log('res', task);

      res.send(task);

    });

});

router.post('/create', function(req, res){

   console.log(req.body);

   var new_task = new Task(req.body);

   console.log(new_task);

   Task.createTask(new_task, function(err, task) {

    

      if (err)

        res.send(err);

      res.json(task);

    });

   res.send('success.');

});

//export this router to use in our index.js

module.exports = router;

Solution

change the code so that res.send is not called twice . .

Code Changes 

add the following import in your component.ts file .

  

        

      if (err)

        res.send(err);

      res.json(task);

    });

  // res.send('success.');

         

OUTPUT

works 

Thanks for reading . Let me know your thoughts in the comments below    .