Service

Source: src/AWS/ECS/Service.ts

An ECS service for running long-lived tasks.

Service keeps a registered task definition running with awsvpc networking. Load balancing is explicit: pass user-supplied loadBalancers target groups, or set public: true to have Alchemy provision a public ALB + listener + target group as a convenience. Launch behavior is controlled via launchType (default FARGATE) or a capacityProviderStrategy.

Most configuration is updated in place via updateService (desiredCount, task definition, network, deployment config, placement, exec, load balancers, tags). Only truly-immutable aspects — serviceName, cluster, launchType↔capacityProviderStrategy switch, deploymentController type, schedulingStrategy, enableECSManagedTags, role — replace the service.

Creating Services

Internal Service

const service = yield* Service("WorkerService", {
  cluster,
  task: workerTask,
  vpcId: vpc.vpcId,
  subnets: [privateSubnet1.subnetId, privateSubnet2.subnetId],
  securityGroups: [workerSecurityGroup.groupId],
  desiredCount: 2,
});

Public HTTP Service (Alchemy-managed ALB)

const service = yield* Service("ApiService", {
  cluster,
  task: apiTask,
  vpcId: vpc.vpcId,
  subnets: [publicSubnet1.subnetId, publicSubnet2.subnetId],
  securityGroups: [serviceSecurityGroup.groupId],
  public: true,
});

Load Balancing

const service = yield* Service("ApiService", {
  cluster,
  task: apiTask,
  vpcId: vpc.vpcId,
  subnets: [subnet1.subnetId, subnet2.subnetId],
  loadBalancers: [
    {
      targetGroupArn,
      containerName: apiTask.containerName,
      containerPort: apiTask.port,
    },
  ],
});

Capacity & Placement

const service = yield* Service("WorkerService", {
  cluster,
  task: workerTask,
  vpcId: vpc.vpcId,
  subnets: [subnet.subnetId],
  capacityProviderStrategy: [
    { capacityProvider: "FARGATE_SPOT", weight: 4 },
    { capacityProvider: "FARGATE", weight: 1, base: 1 },
  ],
  placementStrategy: [{ type: "spread", field: "attribute:ecs.availability-zone" }],
});

Deployment

const service = yield* Service("ApiService", {
  cluster,
  task: apiTask,
  vpcId: vpc.vpcId,
  subnets: [subnet1.subnetId, subnet2.subnetId],
  desiredCount: 3,
  enableExecuteCommand: true,
  deploymentConfiguration: {
    minimumHealthyPercent: 100,
    maximumPercent: 200,
    deploymentCircuitBreaker: { enable: true, rollback: true },
  },
  healthCheckGracePeriodSeconds: 30,
});