Stash and gitlab-ci

It is possible to use the stash workflow to avoid recompiling sources multiple times in a single gitlab-ci pipeline. For instance if you have different jobs in the your pipeline which run different variations of sbt test.

sbt-hoarder works largely out of the box. For convenience if you have a multi-project build, you may wish to change the default stash directory to be at the top level of your project like this:

globalStashLocation := (baseDirectory in ThisBuild).value / "sbt-stash"

Then you should use artifacts: and dependencies: as in the following example gitlab-ci.yaml:

stages:
  - quick
  - slow

unit-test:
  stage: quick
  artifacts:
    paths:
      - sbt-stash
    expire_in: 1 day
  script:
    - sbt clean test:compile stash Common/test

slow-integration-test-one:
  stage: slow
  dependencies:
    - unit-test
  script:
    - sbt stashApply 'IntegrationTestOne/test'

slow-integration-test-two:
  stage: slow
  dependencies:
    - unit-test
  script:
    - sbt stashApply 'IntegrationTestTwo/test'

Use artifacts: not cache:

Gitlab cache at best provided on a “best effort” basis, and in any case is only cached per-runner, so in the presence of multiple runners it will be unlikely to be available for later jobs. When using cache also beware that the runner logs say cache was found even when no files were actually provided (for instance because the cache is on a different runner)

Even in a single runner setup, “best effort” combines badly with sbt-hoarder’s stash workflow: sbt stashApply will fail if a stash is not found rather than silently succeeding without using a stash. This would generally cause your pipeline to fail.

None of this is an issue if you use artifacts: as in the example above.

(A valid related use of cache is to avoid re-downloading external dependencies. You could cache your ~/.ivy directory.)

Alternatives

You may not need sbt-hoarder at all:

• Simplest is to combine all your sbt tasks into one gitlab-ci job. Then no caching is required.

• You can also avoid recompilation by having your compilation job publish its jar to a repository such as Nexus.