# Auto Scaling in AWS

# Auto Scaling 
> AWS provides multiple services that you can use to scale your application. Auto scaling is enabled by Amazon CloudWatch and is available at no additional charge beyond the service fees for CloudWatch and the other AWS resources that you use.

1. What is Auto Scaling?
2. Befits of Auto Scaling
3. Experience Auto Scaling
       Step 1: Create load balancer.
       Step 2: Create Launch configuration  
       Step 3: Create Topic in SNS ( Simple Notification Service )
       Step 4: Create Auto scaling group.
       Step 5: Create Alarm in CloudWatch
       Step 6: Add Policy in Auto Scaling



### 1. What is Auto Scaling?
> AWS Auto Scaling is a service that helps the user to monitor applications and automatically adjusts the capacity to maintain steady, predictable performance at the lowest possible cost.

> Auto Scaling helps you ensure that you have the correct number of EC2 instances available to handle the load for your application.

### 2. Befits of Auto Scaling
- Better fault tolerance
- High availability of resources
- Better cost management
- High reliability of resources
- The high flexibility of resources

### 3. Understanding Launch Configuration  .

**Step 1: Create load balancer**

     Select Mumbai location
     EC 2 dashboard =>  load balancer =>  create load balancer
     Load balancer Name => LB
     Next => Create new Security group 
     Security group name => LB_Sg
     Description => LB_Sg
     => in Security group open two ports   SSH  and HTTP
     =>Next => Configure health check
    Response timeout => 2
    Interval => 5
    Unhealthy  threshold => 2
    Healthy threshold  => 2
    Next => Next => Review and create => Create => Close

**Step 2: Creating launch configuration**

Under Auto Scaling
Select Launch configurations  => Create launch configuration
Name: ASG =>AMI => ami-08e0ca9924195beba => t2 micro 

In advanced Details     User data
     #!/bin/bash
     sudo su
     yum update -y
     yum install httpd -y
    cd /var/www/html
    echo "MyGoogle_page2" > index.html
    service httpd start
    chkconfig httpd on

Next => Select existing security group  : LB_Sg
Create new key pair => Key Pair name =>  KP  => download key pair => create launch configuration.

**Step 3: Create Topic in SNS**

     Services => Application Integration => Simple Notification Service 
     Create Topic = >Type - Standard => Name - My_Topic
     Display Name - My_Topic =>Create topic.

Add subscriptions to the topic

     Create Subscription  => Protocol - Email  =>Endpoint =>  Your Email => Create 
     Subscription => Confirm the subscription.

**Step 4: Create Auto Scaling Group**

     Select the Launch Configuration => Actions => Create Auto Scaling Group
      - Auto Scaling group name=> ASG
      - Subnet => ap-south-1a
      - Attach Existing Load Balancer => Choose from Classic Load Balancers 
          => Select Load Balancer
      - Configure Group size ( Take Defaults ) =>Next => Next => Provide Name Tag => 
         Review and Create

**Step 5: Create Alarm in CloudWatch**

Services => Management & Governance => CloudWatch

      Alarm =>  Create Alarm => Select Metric => EC2 => By Auto Scaling Group 
       => Select Auto Scaling Group Name  , Metric Name - CPU Utilization => Select Metric 
       => Conditions 
       => Static => Greater than > 80 => Next => Select  existing 
           SNS topic ( My_Topic ) =>Next =>Alarm Name(My_Alarm) => Next => Create Alarm.

      Alarm =>  Create Alarm => Select Metric => EC2 => By Auto Scaling Group 
      => Select Auto Scaling Group Name  , Metric Name - CPU Utilization 
      => Select Metric => Conditions 
      => Static => less than < 30 => Next => Select  existing SNS 
           topic ( My_Topic) =>Next =>Alarm Name(My_Alarm2) => Next => Create Alarm.

**Step 6: Add Policy in Auto Scaling**

    Select Auto Scaling groups => Automatic Scaling Tab => Creating Dynamic scaling Policy
    Policy Type => Simple Scaling
    Scaling policy name => Increase_Policy 
    CloudWatch Alarm=> My_alarm
    Take the Action => Add => 1  Unit ( EC2 Machine ) =>Create

    Select Auto Scaling groups => Automatic Scaling Tab => Creating Dynamic scaling Policy
    Policy Type => Simple Scaling
    Scaling policy name => Decrease_Policy
    CloudWatch Alarm => My_alarm2
    Take the Action => Remove => 1  Unit ( EC2 Machine ) => Create


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