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GitHub Actions Importer を使った Jenkins からの移行

GitHub Actions Importer を使って、Jenkins パイプラインの GitHub Actions への移行を自動化する方法について説明します。

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About migrating from Jenkins with GitHub Actions Importer

The instructions below will guide you through configuring your environment to use GitHub Actions Importer to migrate Jenkins pipelines to GitHub Actions.

Prerequisites

  • A Jenkins account or organization with pipelines and jobs that you want to convert to GitHub Actions workflows.

  • Access to create a Jenkins personal API token for your account or organization.

  • An environment where you can run Linux-based containers, and can install the necessary tools.

    Note: The GitHub Actions Importer container and CLI do not need to be installed on the same server as your CI platform.

Limitations

There are some limitations when migrating from Jenkins to GitHub Actions with GitHub Actions Importer. For example, you must migrate the following constructs manually:

  • Mandatory build tools
  • Scripted pipelines
  • Secrets
  • Self-hosted runners
  • Unknown plugins

For more information on manual migrations, see "Migrating from Jenkins to GitHub Actions."

Installing the GitHub Actions Importer CLI extension

  1. Install the GitHub Actions Importer CLI extension:

    Bash
    gh extension install github/gh-actions-importer
    
  2. Verify that the extension is installed:

    $ gh actions-importer -h
    Options:
      -?, -h, --help  Show help and usage information
    
    Commands:
      update     Update to the latest version of GitHub Actions Importer.
      version    Display the version of GitHub Actions Importer.
      configure  Start an interactive prompt to configure credentials used to authenticate with your CI server(s).
      audit      Plan your CI/CD migration by analyzing your current CI/CD footprint.
      forecast   Forecast GitHub Actions usage from historical pipeline utilization.
      dry-run    Convert a pipeline to a GitHub Actions workflow and output its yaml file.
      migrate    Convert a pipeline to a GitHub Actions workflow and open a pull request with the changes.
    

Configuring credentials

The configure CLI command is used to set required credentials and options for GitHub Actions Importer when working with Jenkins and GitHub.

  1. Create a GitHub personal access token. For more information, see "Managing your personal access tokens."

    Your token must have the workflow scope.

    After creating the token, copy it and save it in a safe location for later use.

  2. Create a Jenkins API token. For more information, see Authenticating scripted clients in the Jenkins documentation.

    After creating the token, copy it and save it in a safe location for later use.

  3. In your terminal, run the GitHub Actions Importer configure CLI command:

    gh actions-importer configure
    

    The configure command will prompt you for the following information:

    • For "Which CI providers are you configuring?", use the arrow keys to select Jenkins, press Space to select it, then press Enter.
    • For "Personal access token for GitHub", enter the value of the personal access token that you created earlier, and press Enter.
    • For "Base url of the GitHub instance", enter the URL for your GitHub Enterprise Server instance, and press Enter.
    • For "Personal access token for Jenkins", enter the value for the Jenkins personal API token that you created earlier, and press Enter.
    • For "Username of Jenkins user", enter your Jenkins username and press Enter.
    • For "Base url of the Jenkins instance", enter the URL of your Jenkins instance, and press Enter.

    An example of the configure command is shown below:

    $ gh actions-importer configure
    ✔ Which CI providers are you configuring?: Jenkins
    Enter the following values (leave empty to omit):
    ✔ Personal access token for GitHub: ***************
    ✔ Base url of the GitHub instance: https://github.com
    ✔ Personal access token for Jenkins: ***************
    ✔ Username of Jenkins user: admin
    ✔ Base url of the Jenkins instance: https://localhost
    Environment variables successfully updated.
    
  4. In your terminal, run the GitHub Actions Importer update CLI command to connect to GitHub Packages Container registry and ensure that the container image is updated to the latest version:

    gh actions-importer update
    

    The output of the command should be similar to below:

    Updating ghcr.io/actions-importer/cli:latest...
    ghcr.io/actions-importer/cli:latest up-to-date
    

Perform an audit of Jenkins

You can use the audit command to get a high-level view of all pipelines in a Jenkins server.

The audit command performs the following steps:

  1. Fetches all of the projects defined in a Jenkins server.
  2. Converts each pipeline to its equivalent GitHub Actions workflow.
  3. Generates a report that summarizes how complete and complex of a migration is possible with GitHub Actions Importer.

Running the audit command

To perform an audit of a Jenkins server, run the following command in your terminal:

gh actions-importer audit jenkins --output-dir tmp/audit

Inspecting the audit results

The files in the specified output directory contain the results of the audit. See the audit_summary.md file for a summary of the audit results.

The audit summary has the following sections.

Pipelines

The "Pipelines" section contains a high-level statistics regarding the conversion rate done by GitHub Actions Importer.

Listed below are some key terms that can appear in the "Pipelines" section:

  • Successful pipelines had 100% of the pipeline constructs and individual items converted automatically to their GitHub Actions equivalent.
  • Partially successful pipelines had all of the pipeline constructs converted, however, there were some individual items that were not converted automatically to their GitHub Actions equivalent.
  • Unsupported pipelines are definition types that are not supported by GitHub Actions Importer.
  • Failed pipelines encountered a fatal error when being converted. This can occur for one of three reasons:
    • The pipeline was misconfigured and not valid in Bamboo.
    • GitHub Actions Importer encountered an internal error when converting it.
    • There was an unsuccessful network response that caused the pipeline to be inaccessible, which is often due to invalid credentials.

Build steps

The "Build steps" section contains an overview of individual build steps that are used across all pipelines, and how many were automatically converted by GitHub Actions Importer.

Listed below are some key terms that can appear in the "Build steps" section:

  • A known build step is a step that was automatically converted to an equivalent action.
  • An unknown build step is a step that was not automatically converted to an equivalent action.
  • An unsupported build step is a step that is either:
    • Fundamentally not supported by GitHub Actions.
    • Configured in a way that is incompatible with GitHub Actions.
  • An action is a list of the actions that were used in the converted workflows. This can be important for:
    • If you use GitHub Enterprise Server, gathering the list of actions to sync to your instance.
    • Defining an organization-level allowlist of actions that are used. This list of actions is a comprehensive list of actions that your security or compliance teams may need to review.

Manual tasks

The "Manual tasks" section contains an overview of tasks that GitHub Actions Importer is not able to complete automatically, and that you must complete manually.

Listed below are some key terms that can appear in the "Manual tasks" section:

  • A secret is a repository or organization-level secret that is used in the converted pipelines. These secrets must be created manually in GitHub Actions for these pipelines to function properly. For more information, see "Using secrets in GitHub Actions."
  • A self-hosted runner refers to a label of a runner that is referenced in a converted pipeline that is not a GitHub-hosted runner. You will need to manually define these runners for these pipelines to function properly.

Files

The final section of the audit report provides a manifest of all the files that were written to disk during the audit.

Each pipeline file has a variety of files included in the audit, including:

  • The original pipeline as it was defined in GitHub.
  • Any network responses used to convert the pipeline.
  • The converted workflow file.
  • Stack traces that can be used to troubleshoot a failed pipeline conversion.

Additionally, the workflow_usage.csv file contains a comma-separated list of all actions, secrets, and runners that are used by each successfully converted pipeline. This can be useful for determining which workflows use which actions, secrets, or runners, and can be useful for performing security reviews.

Forecast potential build runner usage

You can use the forecast command to forecast potential GitHub Actions usage by computing metrics from completed pipeline runs in your Jenkins server.

Prerequisites for running the forecast command

In order to run the forecast command against a Jenkins instance, you must install the paginated-builds plugin on your Jenkins server. This plugin allows GitHub Actions Importer to efficiently retrieve historical build data for jobs that have a large number of builds. Because Jenkins does not provide a method to retrieve paginated build data, using this plugin prevents timeouts from the Jenkins server that can occur when fetching a large amount of historical data. The paginated-builds plugin is open source, and exposes a REST API endpoint to fetch build data in pages, rather than all at once.

To install the paginated-builds plugin:

  1. On your Jenkins instance, navigate to https://<your-jenkins-instance>/pluginManager/available.
  2. Search for the paginated-builds plugin.
  3. Check the box on the left and select Install without restart.

Running the forecast command

To perform a forecast of potential GitHub Actions, run the following command in your terminal. By default, GitHub Actions Importer includes the previous seven days in the forecast report.

gh actions-importer forecast jenkins --output-dir tmp/forecast

Inspecting the forecast report

The forecast_report.md file in the specified output directory contains the results of the forecast.

Listed below are some key terms that can appear in the forecast report:

  • The job count is the total number of completed jobs.
  • The pipeline count is the number of unique pipelines used.
  • Execution time describes the amount of time a runner spent on a job. This metric can be used to help plan for the cost of GitHub-hosted runners.
    • This metric is correlated to how much you should expect to spend in GitHub Actions. This will vary depending on the hardware used for these minutes. You can use the GitHub Actions pricing calculator to estimate the costs.
  • Queue time metrics describe the amount of time a job spent waiting for a runner to be available to execute it.
  • Concurrent jobs metrics describe the amount of jobs running at any given time. This metric can be used to define the number of runners you should configure.

Additionally, these metrics are defined for each queue of runners in Jenkins. This is especially useful if there is a mix of hosted or self-hosted runners, or high or low spec machines, so you can see metrics specific to different types of runners.

Perform a dry-run migration of a Jenkins pipeline

You can use the dry-run command to convert a Jenkins pipeline to its equivalent GitHub Actions workflow.

Running the dry-run command

You can use the dry-run command to convert a Jenkins pipeline to an equivalent GitHub Actions workflow. A dry-run creates the output files in a specified directory, but does not open a pull request to migrate the pipeline.

To perform a dry run of migrating your Jenkins pipelines to GitHub Actions, run the following command in your terminal, replacing my-jenkins-project with the URL of your Jenkins job.

gh actions-importer dry-run jenkins --source-url my-jenkins-project --output-dir tmp/dry-run

Inspecting the converted workflows

You can view the logs of the dry run and the converted workflow files in the specified output directory.

If there is anything that GitHub Actions Importer was not able to convert automatically, such as unknown build steps or a partially successful pipeline, you might want to create custom transformers to further customize the conversion process. For more information, see "Extending GitHub Actions Importer with custom transformers."

Perform a production migration of a Jenkins pipeline

You can use the migrate command to convert a Jenkins pipeline and open a pull request with the equivalent GitHub Actions workflow.

Running the migrate command

To migrate a Jenkins pipeline to GitHub Actions, run the following command in your terminal, replacing the target-url value with the URL for your GitHub Enterprise Server repository, and my-jenkins-project with the URL for your Jenkins job.

gh actions-importer migrate jenkins --target-url https://github.com/:owner/:repo --output-dir tmp/migrate --source-url my-jenkins-project

The command's output includes the URL to the pull request that adds the converted workflow to your repository. An example of a successful output is similar to the following:

$ gh actions-importer migrate jenkins --target-url https://github.com/octo-org/octo-repo --output-dir tmp/migrate --source-url http://localhost:8080/job/monas_dev_work/job/monas_freestyle
[2022-08-20 22:08:20] Logs: 'tmp/migrate/log/actions-importer-20220916-014033.log'
[2022-08-20 22:08:20] Pull request: 'https://github.com/octo-org/octo-repo/pull/1'

Inspecting the pull request

The output from a successful run of the migrate command contains a link to the new pull request that adds the converted workflow to your repository.

Some important elements of the pull request include:

  • In the pull request description, a section called Manual steps, which lists steps that you must manually complete before you can finish migrating your pipelines to GitHub Actions. For example, this section might tell you to create any secrets used in your workflows.
  • The converted workflows file. Select the Files changed tab in the pull request to view the workflow file that will be added to your GitHub Enterprise Server repository.

When you are finished inspecting the pull request, you can merge it to add the workflow to your GitHub Enterprise Server repository.

Reference

This section contains reference information on environment variables, optional arguments, and supported syntax when using GitHub Actions Importer to migrate from Jenkins.

Using environment variables

GitHub Actions Importer uses environment variables for its authentication configuration. These variables are set when following the configuration process using the configure command. For more information, see the "Configure credentials for GitHub Actions Importer" section.

GitHub Actions Importer uses the following environment variables to connect to your Jenkins instance:

  • GITHUB_ACCESS_TOKEN: The personal access token used to create pull requests with a converted workflow (requires repo and workflow scopes).

  • GITHUB_INSTANCE_URL: The URL to the target GitHub instance (for example, https://github.com).

  • JENKINS_ACCESS_TOKEN: The Jenkins API token used to view Jenkins resources.

    Note: This token requires access to all jobs that you want to migrate or audit. In cases where a folder or job does not inherit access control lists from their parent, you must grant explicit permissions or full admin privileges.

  • JENKINS_USERNAME: The username of the user account that created the Jenkins API token.

  • JENKINS_INSTANCE_URL: The URL of the Jenkins instance.

  • JENKINSFILE_ACCESS_TOKEN (Optional) The API token used to retrieve the contents of a Jenkinsfile stored in the build repository. This requires the repo scope. If this is not provided, the GITHUB_ACCESS_TOKEN will be used instead.

These environment variables can be specified in a .env.local file that is loaded by GitHub Actions Importer when it is run.

Using optional arguments

There are optional arguments you can use with the GitHub Actions Importer subcommands to customize your migration.

--source-file-path

You can use the --source-file-path argument with the forecast, dry-run, or migration subcommands.

By default, GitHub Actions Importer fetches pipeline contents from source control. The --source-file-path argument tells GitHub Actions Importer to use the specified source file path instead. You can use this option for Jenkinsfile and multibranch pipelines.

If you would like to supply multiple source files when running the forecast subcommand, you can use pattern matching in the file path value. For example, gh forecast --source-file-path ./tmp/previous_forecast/jobs/*.json supplies GitHub Actions Importer with any source files that match the ./tmp/previous_forecast/jobs/*.json file path.

Jenkinsfile pipeline example

In this example, GitHub Actions Importer uses the specified Jenkinsfile as the source file to perform a dry run.

gh actions-importer dry-run jenkins --output-dir path/to/output/ --source-file-path path/to/Jenkinsfile --source-url :url_to_jenkins_job

--config-file-path

You can use the --config-file-path argument with the audit, dry-run, and migrate subcommands.

By default, GitHub Actions Importer fetches pipeline contents from source control. The --config-file-path argument tells GitHub Actions Importer to use the specified source files instead.

When you use the --config-file-path option with the dry-run or migrate subcommands, GitHub Actions Importer matches the repository slug to the job represented by the --source-url option to select the pipeline. It uses the config-file-path to pull the specified source file.

Audit example

In this example, GitHub Actions Importer uses the specified YAML configuration file to perform an audit.

gh actions-importer audit jenkins --output-dir path/to/output/ --config-file-path path/to/jenkins/config.yml

To audit a Jenkins instance using a config file, the config file must be in the following format, and each repository_slug value must be unique:

source_files:
  - repository_slug: pipeline-name
    path: path/to/Jenkinsfile
  - repository_slug: multi-branch-pipeline-name
    branches:
      - branch: main
        path: path/to/Jenkinsfile
      - branch: node
        path: path/to/Jenkinsfile

Supported syntax for Jenkins pipelines

The following tables show the type of properties GitHub Actions Importer is currently able to convert. For more details about how Jenkins pipeline syntax aligns with GitHub Actions, see "Migrating from Jenkins to GitHub Actions".

For information about supported Jenkins plugins, see the github/gh-actions-importer repository.

Supported syntax for Freestyle pipelines

JenkinsGitHub ActionsStatus
docker templatejobs.<job_id>.containerSupported
buildjobsPartially supported
build environmentenvPartially supported
build triggersonPartially supported
generalrunnersPartially supported

Supported syntax for Jenkinsfile pipelines

JenkinsGitHub ActionsStatus
dockerjobs.<job_id>.containerSupported
stagejobs.<job_id>Supported
agentrunnersPartially supported
environmentenvPartially supported
stagesjobsPartially supported
stepsjobs.<job_id>.stepsPartially supported
triggersonPartially supported
whenjobs.<job_id>.ifPartially supported
inputsinputsUnsupported
matrixjobs.<job_id>.strategy.matrixUnsupported
optionsjobs.<job_id>.strategyUnsupported
parametersinputsUnsupported

Environment variables syntax

GitHub Actions Importer uses the mapping in the table below to convert default Jenkins environment variables to the closest equivalent in GitHub Actions.

JenkinsGitHub Actions
${BUILD_ID}${{ github.run_id }}
${BUILD_NUMBER}${{ github.run_id }}
${BUILD_TAG}${{ github.workflow }}-${{ github.run_id }}
${BUILD_URL}${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}
${JENKINS_URL}${{ github.server_url }}
${JOB_NAME}${{ github.workflow }}
${WORKSPACE}${{ github.workspace }}

Portions have been adapted from https://github.com/github/gh-actions-importer/ under the MIT license:

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