AWS Auto Scaling and Load Balancing

Amazon EC2 Auto Scaling lifecycle hooks

Lifecycle hooks enable you to perform custom actions by pausing instances as an Auto Scaling group launches or terminates them.

Each Auto Scaling group can have multiple lifecycle hooks. However, there is a limit on the number of hooks per Auto Scaling group.

Lifecycle hooks per Auto Scaling group: 50

Amazon Event Bridge

Amazon EventBridge is a serverless event bus service that makes it easy to connect your applications with data from a variety of sources. EventBridge delivers a stream of real-time data from your own applications, Software-as-a-Service (SaaS) applications, and AWS services and routes that data to targets like AWS Lambda.

Scaling Policies, Scheduled Actions

Scaling policies per Auto Scaling group: 50
Scheduled actions per Auto Scaling group: 125

These two can co-exist.

EC2 and ELB Health Check

Amazon EC2 Auto Scaling can determine the health status of an instance using one or more of the following:

• Status checks provided by Amazon EC2 to identify hardware and software issues that may impair an instance. The default health checks for an Auto Scaling group are EC2 status checks only.
• Health checks provided by Elastic Load Balancing (ELB). These health checks are disabled by default but can be enabled.
• Your custom health checks.

Health checks provided by Elastic Load Balancing (ELB)

ELB health check verifies if the instance responds to a certain request as expected (e.g. 200 status). Healthy indicates that an instance has passed the Load Balancer’s health check. This means that the Load Balancer will send traffic to the instance.

ALB Health Check

Protocols:

• HTTP
• HTTPS

Examines the response code.

NLB Health CHeck

Protocols:

• TCP
• HTTP
• HTTPS