Why does `git fetch` take a long time to run in GitHub Actions?

ghz 8months ago ⋅ 89 views

I am using GitHub Actions for CI/CD and using actions/checkout@v4 to check out current branch code in the action job. During development, I create a feature branch from develop branch then create a PR to merge to develop branch.

In my build job, I need to compare the changes between feature branch and develop branch, so I need to fetch develop branch as shown in below workflow file:

steps:
      - uses: actions/checkout@v4
      - name: Fetch base branch
        run: |
          git fetch origin ${{ github.base_ref }}
...

The interesting part is that the actions/checkout@v4 took 3 seconds to finish but the git fetch origin develop command took 30 seconds to finish. The two branches are basically similar with only a few changed files. I wonder why it has a lot different when checking out the code. Does GitHub Actions do some optimisation on current branch?

Answers

The difference in execution time between actions/checkout@v4 and git fetch origin develop could be attributed to several factors:

  1. Caching: The actions/checkout action may leverage caching mechanisms to speed up the checkout process. If the repository has been checked out previously in the workflow run or if caching is enabled for the action, it can significantly reduce the checkout time.

  2. Network Latency: The git fetch command involves fetching data from a remote repository, which can be affected by network latency. The time taken for the git fetch command depends on factors such as the size of the repository, network speed, and server responsiveness.

  3. Differences in Implementation: The actions/checkout action is optimized for checking out code in GitHub Actions workflows and may use more efficient methods compared to the git fetch command. It may also perform additional optimizations or parallelize operations to improve performance.

  4. GitHub Actions Infrastructure: The execution time of actions in GitHub Actions workflows can vary based on the current load on GitHub's infrastructure and other factors related to the workflow execution environment.

To improve the performance of the git fetch command, you can consider the following optimizations:

  • Reduce the Scope: If you only need to compare changes between the feature branch and the develop branch, you can fetch only the necessary data instead of fetching the entire repository. For example, you can use git fetch origin develop:<local-branch-name> to fetch the develop branch into a local branch without updating the current branch.

  • Optimize Git Configuration: Ensure that your Git configuration is optimized for performance, such as setting appropriate values for fetch.prune, fetch.depth, and fetch.recurseSubmodules.

  • Use Shallow Clone: If fetching the entire history is not necessary, you can perform a shallow clone (--depth) to fetch a limited history, which can significantly reduce fetch time.

  • Parallel Fetching: You can use Git's --jobs option to fetch multiple branches or objects in parallel, which can improve fetch performance, especially for repositories with large histories.

By optimizing your Git commands and workflow configuration, you can reduce the fetch time and improve the overall performance of your GitHub Actions workflows.

#git