ALB Listeners, Rules, and ECS

Listeners and rules

Listeners

• Each ALB needs at least one listener and can have up to 10.
• Listeners define the port and protocol to listen on.
• You can add one or more listeners.
• You cannot have the same port in multiple listeners.

Listener rules

• Rules determine how the load balancer routes requests to the targets in one or more target groups.
• Each rule consists of a priority, one or more actions, an optional host condition, and an optional path condition.
• Only one action can be configured per rule.
• One or more rules are required.
• Each listener has a default rule and you can optionally define up to 100 additional rules per ALB.
• Rules determine what action is taken when the rule matches the client’s request.
• Rules are defined on listeners.
• You can add rules that specify different target groups based on the content of the request (content-based routing).
• If no rules are found, the default rule will be followed, which directs traffic to the default target groups.

The image below shows a ruleset with a host-based and path-based entry and a default rule at the end: