How to Auto scaling a application
1. Create Elastic Load Balancer - It perform healthy check and make decision where to send traffic.
2. Go to Ec2 instance, under network and security click on load balancer then click button create load balancer
3. Give Name to your load balancer then enable advanced vpc configuration then click on continue. In ping path we keep / as our defult channel.
4. In every 30 second it will check the instance. It has 5 min to responed the request. 2 consecutive unhealthy check put EC2 out of service. To
become healthy again it must pass 10 healty checks to again active.
5. Add subnets to our webservices. We can only add one subnet per availbilty zone.
6. Select ELB in security group then continue.
7. Add EC2 instance if you want otherwise click on create.
8. After following the above steps our load balancers are successfully created.
9. Now we needs to create Launch Configurations. clcik on launch configuration group, select a AMI we have alredy created then go next. In configure details
give any name (auto-scaling-launch). Keep storage as it is, Our security group excatly same as the load balancer. After that create launch configuration.
10. create a Auto scaling group give name to group(auto scaling group). Select The VPC add subnet the same subnet we have added in load balancer. The key here is go to advance details
check revice traffic from load balancer, select your load balancer then click on next.
11. Now come to configuration scaling policy this will boot the server inside load balancer. Later we will cover custome policy
to increase and decrease the size of group based on cloud watch alarm.
12. We will scale between 1 to 3 instances. In next step give any name to key value(auto-scaling).
13. In the end we can add cloud watch alarm. Select ElB matrics then just select HealthyHostCount then Next.
14. Give it a name Like Healthy Host Count Low. then select a condition if healthy host count is less then 2 then it should boot more server. Then click on create alarm.
15.Now we are going to attach this to custome scaling policy inside our autocaling group. To back to auto sacling group
click on scaling policy attach policy give it a name, then select alram in it. Inside take action add 2 instances write in to the load balancer whenever this alarm hit. click create.
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