This document discusses how Spring Boot applications can be optimized to run well on Kubernetes. It describes building a Docker image for a Spring Boot application using multi-stage builds and custom layers to create a slim image. It then covers configuring health checks, graceful shutdown, and other features to prepare the application for deployment on Kubernetes. The document suggests using the spring-boot-maven-plugin to build images and provides an overview of the journey to production for Spring Boot applications on Kubernetes.

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Madhura Bhave
The New Center of the Universe
Spring Boot ♥ Kubernetes

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Center of the Universe

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Unit of DeploymentCenter of the JVM Universe

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👩💻 🧑💻
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
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$ mvn package

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$ java -jar application.jar

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The only constant is change

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👩💻 🧑💻
🤔

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FROM openjdk:8-jdk-alpine
EXPOSE 8080
ARG JAR_FILE=target/my-application.jar
ADD ${JAR_FILE} app.jar
ENTRYPOINT ["java","-jar","/app.jar"]
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$ docker build .
FROM openjdk:8-jdk-alpine
EXPOSE 8080
ARG JAR_FILE=target/my-application.jar
ADD ${JAR_FILE} app.jar
ENTRYPOINT ["java","-jar","/app.jar"]
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my-application.jar
JDK
OS

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my-application.jar
JDK
OS
Fat jar overhead
Single layer for jar
Not optimal

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Application
Snapshot Dependencies
OS
Spring Boot Loader
Dependencies
JDK

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FROM adoptopenjdk:11-jre-hotspot as builder
WORKDIR application
ARG JAR_FILE=target/*.jar
COPY ${JAR_FILE} application.jar
RUN java -Djarmode=layertools -jar application.jar extract
FROM adoptopenjdk:11-jre-hotspot
WORKDIR application
COPY --from=builder application/dependencies/ ./
COPY --from=builder application/spring-boot-loader/ ./
COPY --from=builder application/snapshot-dependencies/ ./
COPY --from=builder application/application/ ./
ENTRYPOINT ["java", "org.springframework.boot.loader.JarLauncher"]
2.3
layertools

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FROM adoptopenjdk:11-jre-hotspot as builder
WORKDIR application
ARG JAR_FILE=target/*.jar
COPY ${JAR_FILE} application.jar
RUN java -Djarmode=layertools -jar application.jar extract
FROM adoptopenjdk:11-jre-hotspot
WORKDIR application
COPY --from=builder application/dependencies/ ./
COPY --from=builder application/spring-boot-loader/ ./
COPY --from=builder application/snapshot-dependencies/ ./
COPY --from=builder application/application/ ./
ENTRYPOINT ["java", "org.springframework.boot.loader.JarLauncher"]
2.3
layertools
layers.idx
custom layers

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👩💻 🧑💻 Is this another tool I need to learn about?
Not really 😃

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♥
2.3
layers.idx
custom layers
$ mvn spring-boot:build-image

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Journey to Production
2.3
Graceful Shutdown
Health Checks
/actuator/liveness 🔮
ConfigMaps and Secrets
🚀
/actuator/readiness
2.4

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2.3

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Spring Boot loves K8s
👩💻 🧑💻
🤔
Stephane Nicoll
Brian Clozel