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Spring Boot Workers

Java/Spring Boot application with Redis-backed task queue, demonstrating two services from one Docker image.

Overview
Tech Stack Java 21 / Spring Boot + Redis
Services 2 (api + worker)
Database PostgreSQL
Cache The managed Redis cache
Pattern Background workers, conditional activation

The appmecca.yaml

containers:
  - name: app
    dockerfile: Dockerfile
    context: .

deploy:
  - name: api
    container: app
    port: 8080
    health_check:
      path: /health
      startup_timeout: 300
    resources:
      memory: "512m"

  - name: worker
    container: app
    command: "java -jar app.jar --app.worker.enabled=true --server.port=0"
    resources:
      memory: "512m"

database:
  enabled: true

redis:
  enabled: true

JVM services need resources.memory

Both services run a JVM, so both declare 512m. The platform default is 128 MB, which a Spring Boot process exhausts during startup — the container is killed with exit code 137 before it ever serves a request. Validation warns you about this when it can see a JVM-shaped command:, but it cannot see inside your Dockerfile's CMD, so set it explicitly on every JVM service.

The unit suffix is required. 512m and 1g are valid; a bare 512 means 512 bytes and 512mb is not a recognised form.

Key Concepts

Conditional Worker Activation

The worker uses Spring's @ConditionalOnProperty annotation. The TaskWorker bean only starts when app.worker.enabled=true is passed via the command override. This means the API service never accidentally processes tasks.

Redis as a Simple Queue

Instead of a dedicated message broker, this app uses a Redis list as a task queue. The API pushes task IDs with LPUSH, and the worker pops them with BRPOP. This is simpler than using a full message broker for basic use cases.

Step-by-Step Deployment

1. Register the app

mecca register git@gitlab.com:appmecca-sample-apps/spring-boot-workers.git \
  -e dev

2. Build

mecca build trigger \
  -e dev \
  -g git@gitlab.com:appmecca-sample-apps/spring-boot-workers.git

3. Deploy

mecca app deploy -e dev spring-boot-workers

4. Verify

mecca app show -e dev spring-boot-workers

curl https://spring-boot-workers-api.dev.yourdomain.io/health

The worker is portless, so it has no URL. Check it with its logs instead:

mecca logs spring-boot-workers --service worker -e dev

What's Next