Docker sometimes cannot see jar file - spring-boot

Question

I have a weird problem, that sometimes a docker container cannot see a .jar file, while most of the time it does not have any problem with it.
Before i show you the docker image, a little bit of background. Normally i build a jar archive before running my container, a pretty simple container to run a spring boot application. However at some seemingly random point in the daily routine it does not boot up with the container reporting "Unable to access jarfile".
I thought it must be some weird permission stuff, so i took snapshot of my "target" directory when working and when it stopped working via ls -alR target and later comparing those snapshot with git diff. It does not show any difference. I am still pretty convinced it must be related to file-permissions, locking or something of that sort but i do not know where to start.
I am on Mac 12.0.1 btw. Any ideas appreciated.
The docker file
FROM openjdk:8-oraclelinux8
RUN mkdir /app
WORKDIR /app
CMD "java" "-jar" "app.war"
And docker-compose.yml
version: "3.9"
services:
app:
build: .
depends_on:
- sql1
volumes:
- ./target:/app
ports:
- "8080:8080"
links:
- "sql1:sqlserver"
...

Answer 1

I'm not sure if this helps, but I don't see your Dockerfile as robust enough to produce consistent results regardless of the state of your localhost workspace. I may ask, are you building your war file manually and then creating your Docker container?
Please try to follow this approach if it fits your needs :
make sure you delete jar/war files before building the container.
Have a multistage Dockerfile with a "build" phase for your spring boot app where you generate the jar/war file from a builder image (ant, gradle, maven), and then have a second stage where the jar/war file gets copied over to it's final location and the application gets executed, this way you ensure consistency and that the file will be there at all times :
This is an example for my spring boot templates that I use very often, it's quite generic (as I handle the renaming of the jar file without having to worry about how pom.xml is configured individually) and I guess could be implemented in a variety of scenarios
FROM maven:3.8.6-openjdk-18 as builder
WORKDIR /usr/app/
COPY . /usr/app
RUN mvn package -Dmaven.test.skip
RUN JAR_FILE="target/*.jar"; cp ${JAR_FILE} /app.jar
FROM openjdk:18
WORKDIR /usr/app
COPY --from=builder /app.jar /usr/app
EXPOSE 8080
CMD ["java","-jar","app.jar"]
docker compose :
services:
app:
build: .
depends_on:
- sql1
ports:
- 8080:8080
networks:
- spring-boot-api-network
volumes:
- ./target:/app
...
NOTE : I would also remove the "links" option as it is a legacy feature you should avoid using and use networks instead :
You can try this network implementation added at the bottom of your compose file, just make sure you don't forget to add the network: to the sql1 portion as well
networks:
spring-boot-api-network:
driver: bridge
ipam:
driver: default
config:
- subnet: 182.16.0.1/24
gateway: 182.16.0.1
name: spring-boot-api-network