How can you configure the distribution of pipeline stages across multiple agents in GitLab CI?

In GitLab CI, tagging and defining tags in the .gitlab-ci.yml configuration are used to distribute pipeline stages across different agents (runners).

Each GitLab Runner can be configured with specific tags, such as linux, docker, windows, etc. In the job description within the pipeline, the corresponding tags are specified so that GitLab knows on which runners to execute this task.

Example:

build_job:
  stage: build
  tags:
    - docker
  script:
    - echo "Build step"
test_job:
  stage: test
  tags:
    - linux
  script:
    - echo "Test step"

In this example, build_job will only run on runners with the docker tag, and test_job on runners with the linux tag.

Thus, to distribute stages across different agents, you need to:

1. Configure GitLab Runner with the required tags.
2. Specify the appropriate tags for jobs in .gitlab-ci.yml.

This allows flexible management of where different pipeline stages will be executed.