In GitLab silver and premium, there is the
$CI_JOB_TOKEN available, which allows the following .gitlab-ci.yaml snippet:
build_submodule:
image: debian
stage: test
script:
- apt update && apt install -y unzip
- curl --location --output artifacts.zip "https://gitlab.example.com/api/v4/projects/1/jobs/artifacts/master/download?job=test&job_token=$CI_JOB_TOKEN"
- unzip artifacts.zip
only:
- tags
However, if you do not have silver or higher gitlab subscriptions, but rely on free tiers, it is also possible to use the API and pipeline triggers.
Let's assume we have project A building app.jar which is needed by project B.
First, you will need an API Token.
Go to Profile settings/Access Tokens page to create one, then store it as a variable in project B. In my example it's GITLAB_API_TOKEN.
In the CI / CD settings of project B add a new trigger, for example "Project A built". This will give you a token which you can copy.
Open project A's .gitlab-ci.yaml and copy the trigger_build: section from project B's CI / CD settings trigger section.
Project A:
trigger_build:
stage: deploy
script:
- "curl -X POST -F token=TOKEN -F ref=REF_NAME https://gitlab.example.com/api/v4/projects/${PROJECT_B_ID}/trigger/pipeline"
Replace TOKEN with that token (better, store it as a variable in project A -- then you will need to make it token=${TRIGGER_TOKEN_PROJECT_B} or something), and replace REF_NAME with your branch (e.g. master).
Then, in project B, we can write a section which only builds on triggers and retrieves the artifacts.
Project B:
download:
stage: deploy
only:
- triggers
script:
- "curl -O --header 'PRIVATE-TOKEN: ${GITLAB_API_TOKEN}' https://gitlab.example.com/api/v4/projects/${PROJECT_A_ID}/jobs/${REMOTE_JOB_ID}/artifacts/${REMOTE_FILENAME}"
If you know the artifact path, then you can replace ${REMOTE_FILENAME} with it, for example build/app.jar. The project ID can be found in the CI / CD settings.
I extended the script in project A to pass the remaining information as documented in the trigger settings section:
Add variables[VARIABLE]=VALUE to an API request. Variable values can be used to distinguish between triggered pipelines and normal pipelines.
So the trigger passes the REMOTE_JOB_ID and the REMOTE_FILENAME, but of course you can modify this as you need it:
curl -X POST \
-F token=TOKEN \
-F ref=REF_NAME \
-F "variables[REMOTE_FILENAME]=build/app.jar" \
-F "variables[REMOTE_JOB_ID]=${CI_JOB_ID}" \
https://gitlab.example.com/api/v4/projects/${PROJECT_B_ID}/trigger/pipeline
