Auto Scaling

• Lets create an Auto Scaling Group with an AMI (apache2, php and stress)
• Create a Launch Configuration by selecting
  • AMI
  • Instance type
  • Storage
  • Security Group
  • KeyPair
• Create AutoScaling Group linked with Launch Configuration
  • Configure Increase Scenario (eg average cpu utilization > 75 for period of 5 minutes)
  • Configure Decrease Scenario (eg average cpu utilization <= 50 for period of 5 minutes)
• Then you should see the machine running
• Login into one machine to create artificial load using stress

stress --cpu 8 --io 4 --vm 2 --vm-bytes 128M -v --timeout 10m

• To have a closer look, create one more ssh login session and execute htop and observe cpu

Load Balancers

• With Auto scaling group, you will have multiple servers where your application is running, we need to give unique ip/dns to the user
• For this we go with load Balancers
• In AWS, we have three kinds of Load balancers
  • Classic Load Balancer : Layer 4 and Layer 7
  • Application Load Balancer: Layer 7
  • Network Load Balancer: Layer 4
• Load Balancer needs to know which machines are healthy, to do this we have health checks
• Generally there are two kinds of LBs
  • Layer-4 Loadbalancers: LBs which are aware of ip and port
  • Layer-7 Loadbalancers: LB which are aware of http,url, ip and port
• Refer here
• Create a Classic Load balancer by configuring health checks
• Access the appplication using classic loadbalancers dns name.