I'm trying to create a multistage ONBUILD image for a Java project, see the example below. First iteration only seems to see the ONBUILD command in the last stage while inspecting the build result.
FROM maven:3.6.3-jdk-11-slim AS build
RUN mkdir /project
WORKDIR /project
ONBUILD COPY pom.xml /project
ONBUILD RUN mvn dependency:go-offline --batch-mode
ONBUILD COPY . /project
ONBUILD RUN mvn package
FROM adoptopenjdk/openjdk11:jre-11.0.6_10-alpine
RUN mkdir /app
WORKDIR /app
ONBUILD COPY --from=build /project/target/*.jar /app/application.jar
CMD ["java", "-jar", "application.jar"]
I decided to split the stages in 2 images and then combining these in the application image.
FROM maven:3.6.3-jdk-11-slim AS build
RUN mkdir /project
WORKDIR /project
ONBUILD COPY pom.xml /project
ONBUILD RUN mvn dependency:go-offline --batch-mode
ONBUILD COPY . /project
ONBUILD RUN mvn package
FROM adoptopenjdk/openjdk11:jre-11.0.6_10-alpine
RUN mkdir /app
WORKDIR /app
ONBUILD COPY --from=build /project/target/*.jar /app/application.jar
CMD ["java", "-jar", "application.jar"]
Inspecting both images show the correct ONBUILD commands, after combining these 2 images in the following way:
FROM maven-jdk-11-onbuild:latest as build
FROM jre-11-onbuild:latest
The result, it only executes the ONBUILD COPY command from the second image.
[+] Building 0.2s (6/6) FINISHED
=> [internal] load build definition from Dockerfile 0.0s
=> => transferring dockerfile: 120B 0.0s
=> [internal] load .dockerignore 0.0s
=> => transferring context: 34B 0.0s
=> [internal] load metadata for docker.io/library/jre-11:onbuild 0.0s
=> CACHED [build 1/1] FROM docker.io/library/maven-jdk-11:onbuild 0.0s
=> CACHED [stage-1 1/1] FROM docker.io/library/jre-11:onbuild 0.0s
=> ERROR [stage-1 2/1] COPY --from=build /app/target/*.jar /app/application.jar 0.1s
------
> [stage-1 2/1] COPY --from=build /app/target/*.jar /app/application.jar:
------
lstat /var/lib/docker/overlay2/daced0019dbfe2605e586b5607160adb3358c22054ae2762a0338b3681eddd33/merged/app/target: no such file or directory
It looks like the first stage is cached for some reason. Is it possible to combine multistage builds with ONBUILD logic?