Docker, Profiles and Release

Layered jars, 12-factor config, graceful shutdown and health for orchestrators.

• Advanced
• 16 min read
• 3 objectives

Before this lessonLesson 14: Tests with Testcontainers

Spring Boot 3 builds a layered jar that Docker can cache. Config stays in the environment; the process shuts down on SIGTERM.

Image

FROM eclipse-temurin:21-jre
WORKDIR /app
COPY build/libs/app.jar app.jar
EXPOSE 8080
ENTRYPOINT ["java","-XX:MaxRAMPercentage=75","-jar","app.jar"]

Profiles and shutdown

spring:
  profiles:
    active: ${APP_ENV:prod}
  lifecycle:
    timeout-per-shutdown-phase: 20s
server:
  shutdown: graceful

The load balancer should call /actuator/health/readiness. On SIGTERM, Boot stops taking new work, waits in-flight requests, then exits.

• Secrets and URLs from env, not application.yml committed to git.
• Flyway/Liquibase migrate on startup or as a release job.
• Pin the Java and base image versions.