You can control when your jobs run using the only/except keywords, or the more advanced rules keyword along with the pipeline source variable.
Example with only:
scheduled_test:
stage: tests
image: my_image:latest
only:
- schedules
script:
- ./run_some_things.sh
The only keyword lets you define some conditions that mean "this job only runs if these conditions are true", and offers a shorthand to check the source of the pipeline. schedules means that the pipeline was started from a schedule rather than a push, trigger, etc. The except keyword is just the opposite. If it had except: schedules the job would always run except if it was scheduled. You can see the full documentation for the only/except keywords here: https://docs.gitlab.com/ee/ci/yaml/#onlyexcept-basic
As of Gitlab version 12.3, the rules keyword extends the possibilities of the only/except options. We could get the same result from the example above like this:
scheduled_test:
stage: tests
image: my_image:latest
rules:
- if: '$CI_PIPELINE_SOURCE == "schedule"'
when: always
- if: '$CI_PIPELINE_SOURCE == "push"'
when: never
In this example, we check the predefined variable $CI_PIPELINE_SOURCE to see what started this pipeline. If it's "schedule", we always run this job. As an example, if the source is "push" (so the pipeline was started by a git push command), this job will never run. With the rules keyword, all if statements are OR'ed together, so the example above reads, if the source is schedule, always run OR if the source is a push, never run. However, you can AND multiple conditionals together in the same if:
rules:
- if: '$CI_PIPELINE_SOURCE == "push" && $MY_CUSTOM_VARIABLE == true'
when: manual
You can read the full documentation for the rules keyword here: https://docs.gitlab.com/ee/ci/yaml/#rules