How to enable maven artifact caching for gitlab ci runner?

Question

We use gitlab ci with shared runners to do our continuous integration. For each build, the runner downloads tons of maven artifacts.

Is there a way to configure gitl

Answer 1

According to the conversation over on GitLab's issue tracker, I managed to change the Maven local repository path and put it into ./.m2/repository/ directory, which is we will then persist between runs by adding this global block to the CI config:

cache:
  paths:
    - ./.m2/repository
  # keep cache across branch
  key: "$CI_BUILD_REF_NAME"

Unfortunately, according to this StackOverflow answer the maven local repository path can only be set on every run with -Dmaven.repo.local or by editing your settings.xml, which is a tedious task to do in a gitlab-ci configuration script. An option would be to set a variable with the default Maven options and pass it to every run.

Also, it is crucial that the local Maven repository is a child of the current directory. For some reason, putting it in /cache or /builds didn't work for me, even though someone from GitLab claimed it should.

Example of a working gitlab-ci.yml configuration file for Maven + Java:

image: maven:3-jdk-8

variables:
  MAVEN_OPTS: "-Djava.awt.headless=true -Dmaven.repo.local=./.m2/repository"
  MAVEN_CLI_OPTS: "--batch-mode --errors --fail-at-end --show-version"

cache:
  paths:
    - ./.m2/repository
  # keep cache across branch
  key: "$CI_BUILD_REF_NAME"

stages:
  - build
  - test
  - deploy

build-job:
  stage: build
  script:
    - "mvn clean compile $MAVEN_CLI_OPTS"
  artifacts:
    paths:
      - target/

unittest-job:
  stage: test
  dependencies:
    - build-job
  script:
    - "mvn package $MAVEN_CLI_OPTS"
  artifacts:
    paths:
      - target/

integrationtest-job:
  stage: test
  dependencies:
    - build-job
  script:
    - "mvn verify $MAVEN_CLI_OPTS"
  artifacts:
    paths:
      - target/

deploy-job:
  stage: deploy
  artifacts:
    paths:
      - "target/*.jar"