AutoScalingGroup

Source: src/AWS/AutoScaling/AutoScalingGroup.ts

An EC2 Auto Scaling Group that manages a fleet of instances from a launch template and can register that fleet with one or more load balancer target groups.

Pair with ScalingPolicy for target-tracking scaling, ScheduledAction for time-based capacity changes, and consumeLifecycleActions to run a Lambda handler while instances pause during launch/terminate transitions.

Creating an Auto Scaling Group

Fleet from a Launch Template

import { AutoScalingGroup, LaunchTemplate } from "alchemy/AWS/AutoScaling";
import { Subnet, Vpc } from "alchemy/AWS/EC2";

const vpc = yield* Vpc("Vpc", { cidrBlock: "10.0.0.0/16" });
const subnet = yield* Subnet("Subnet", {
  vpcId: vpc.vpcId,
  cidrBlock: "10.0.1.0/24",
});

const template = yield* LaunchTemplate("Template", {
  imageId: "ami-0abcdef1234567890",
  instanceType: "t3.micro",
});

const group = yield* AutoScalingGroup("Fleet", {
  launchTemplate: template,
  subnetIds: [subnet.subnetId],
  minSize: 1,
  maxSize: 3,
});

Reference an existing Launch Template by name

const group = yield* AutoScalingGroup("Fleet", {
  launchTemplate: { launchTemplateName: "my-template", version: 2 },
  subnetIds: [subnet.subnetId],
  minSize: 0,
  maxSize: 0,
  desiredCapacity: 0,
});

Load Balancing

const group = yield* AutoScalingGroup("WebFleet", {
  launchTemplate: template,
  subnetIds: [subnetA.subnetId, subnetB.subnetId],
  minSize: 2,
  maxSize: 6,
  targetGroupArns: [targetGroup.targetGroupArn],
  // healthCheckType defaults to "ELB" when target groups are attached
  healthCheckGracePeriod: "5 minutes",
});

Scaling

import { ScalingPolicy } from "alchemy/AWS/AutoScaling";

yield* ScalingPolicy("CpuPolicy", {
  autoScalingGroup: group,
  predefinedMetricType: "ASGAverageCPUUtilization",
  targetValue: 60,
});