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V4/Pull-Request CI

Name: V4/Pull-Request CI
Author: tkrizek
Incomplete.png Pending review
Last updated: 2017-10-6 by Tkrizek

Overview

During FreeIPA development, existing test cases are often broken by seemingly unrelated changes in the code. Manual testing of all use cases isn't feasible. Running the integration test suite manually is not simple and very time consuming, and thus often skipped. This causes frequent regressions and malfunctioning code in the master branch.

A proposed solution is to implement on pull-request (PR) continuous integration (CI) that will run a large portion of the existing test suite. Currently, we are running single host test on every pull request. The goal of this effort is to extend our on-PR CI to also execute multi-host tests. Running the extended test suite should help us to discover broken test cases early on and stabilize our master branch.

Use Cases

  • As a FreeIPA contributor,
    • I open a pull request on GitHub against the project. FreeIPA core developer verifies no malicious code will be executed during the test runs and approves it for testing and PR is automatically queued for test execution.
    • I update the pull-request. The changes have to be approved by a core developer once again before the code is queued for test execution.
  • As a white-listed FreeIPA contributor,
    • I open a pull request on GitHub against the project. This PR is automatically queued for test execution.
    • I update the pull request's code. This PR is automatically queued for test execution.

Once the test execution finishes, I can see the test results directly in the PR along with links to publicly accessible logs I can inspect to debug failures.

Design

The main goal of this feature is to enable execution of multi-host tests on GitHub PRs. The following has to be addressed in this design:

  • Multi-host environment provisioning
  • GitHub integration
  • Task execution
  • Publishing test results and artifcats
  • Deployment of test runners

Requirements

  • Test results and logs are easily accessible to developers and community
    • It is crucial to be able to track down which test case has failed and why
    • The results must be publicly accessible
  • All test results are available under 1.5 hours
    • Rapid feedback is a priority, even if that results in a smaller test-suite
    • Up to 3 PRs can be tested simultaneously. Additional PRs may increase the time.

Overview

Collection of machines called test runners are monitoring GitHub PRs. Test runners can be running anywhere, they just need to have credentials for GitHub, access to the internet and must support virtualization. If the test runner itself is a virtual machine, it has to support nested virtualization.

A prioritized queue of tasks is constructed from the PRs. These tasks are builds and individual test suites that are executed atomically. Test runner picks up a task with the highest priority and starts executing it. This is announced through GitHub commit status update to avoid collisions with other test runners.

Once the task is finished, a publicly accessible URL with links to the artifacts (rpms, logs) is announced along with the task result in a commit status.

Multi-host environment provisioning

Hosts are provisioned as virtual machines (VM). To speed up the provisioning and to alleviate issues with broken dependencies, VM templates will be created and kept up-to-date. libvirt was chosen as the provider and the templates themselves will be vargant boxes. The boxes are published and accessible on HashiCorp Atlas.

GitHub integration

Test runners communicate through with GitHub through its API. Each pull request has a collection of GitHub commit statuses associated with it. These are used for all communication. This was inspired by the Cockpit project.

Task execution

For each PR, a build and a series of test suites have to be executed. The test runners use a common algorithm to determine the priority of all waiting tasks for all pull requests. Idle test runner picks the top-priority task, starts executing it, and marks it in progress.

Publishing test results and artifacts

Once the task finishes, the artifacts (rpms, logs) are uploaded and a URL is created. Currently, the artifacts are uploaded and stored on fedorapeople.org, although any publicly accessible storage can be used.

The produced URL and the test result is announced by the test runner in the GitHub commit status.

Implementation

For implementation details, see the Developer Documentation.