[CI] Avoid Inter-run Dependencies

by ADMIN 34 views

Introduction

In the context of Continuous Integration (CI), maintaining state between runs can lead to unintended consequences. This article discusses the issue of inter-run dependencies in CI and proposes a solution to avoid them.

The Problem

Inter-run dependencies occur when the state of a CI run is carried forward to the next run, potentially interfering with each other. This can happen when the CI workflow relies on the state of a previous run to determine the configuration of the next run.

Example: Release Flag

One specific example of inter-run dependency is the release flag passed to the build script (./build.sh --release). The build script only re-configures CMake if either the ./build/CMakeCache.txt file is missing or the --force flag is specified. However, due to the way the runner maintains state, the CMakeCache.txt file is always present, and CMake configure is never called.

As a result, the CI jobs only run in release mode because the previous CI job ran in release mode, which in turn only ran in release mode because the previous CI job ran in release mode, and so on. If a PR were to add a flag that forces the CI to a debug build, all future CI runs would be in debug mode.

Subtle Issues

Inter-run dependencies can lead to subtle and hard-to-track-down issues. For instance, if we want to test the XLS integration in CI, which requires a different build config, we would need to either force a reconfigure, leading to a recompile, or maintain separate build folders for separate build configs. Otherwise, if we ever run a single CI job with XLS enabled, it will stay enabled for all other CI jobs.

Solution: Remove Inter-Run State

To avoid inter-run dependencies, we can consider an approach that completely removes inter-CI-run state and relies on CMake's/ninja's dependency analysis to decide if the build files from the previous run are still valid or need to be re-built.

CI Management

Part of the issue here is the CI management, but also part of the issue is the limitations introduced by the ./build.sh script. With a "normal" CMake workflow, configuring and building are different commands. With the uniform ./build.sh script, there is no clear separation.

Best Practices

To avoid inter-run dependencies, we can follow these best practices:

  • Use a clean build folder: Each CI run should use a clean build folder to avoid carrying over state from previous runs.
  • Use a separate build config: Use a separate build config for each CI run to avoid interfering with each other.
  • Use CMake's/ninja's dependency analysis: Rely on CMake's/ninja's dependency analysis to decide if the build files from the previous run are still valid or need to be re-built.

Conclusion

Inter-run dependencies can lead to subtle and hard-to-track-down issues in CI. By removing inter-CI-run state and relying on CMake's/ninja's dependency analysis, we can avoid these issues and ensure that each CI run is independent and self-contained.

Future Work

To further improve CI, we can consider the following:

  • Implement a clean build folder: Implement a clean build folder for each CI run to avoid carrying over state from previous runs.
  • Use a separate build config: Use a separate build config for each CI run to avoid interfering with each other.
  • Investigate CMake's/ninja's dependency analysis: Investigate CMake's/ninja's dependency analysis to determine if it can be used to improve CI.

References

Appendix

  • CI Workflow: The CI workflow should be designed to avoid inter-run dependencies.
  • Build Script: The build script should be designed to avoid carrying over state from previous runs.
  • CMake/ninja: CMake's/ninja's dependency analysis can be used to decide if the build files from the previous run are still valid or need to be re-built.
    [CI] Avoid Inter-Run Dependencies: Q&A =====================================

Introduction

In our previous article, we discussed the issue of inter-run dependencies in Continuous Integration (CI) and proposed a solution to avoid them. In this article, we will answer some frequently asked questions (FAQs) related to inter-run dependencies in CI.

Q: What are inter-run dependencies in CI?

A: Inter-run dependencies occur when the state of a CI run is carried forward to the next run, potentially interfering with each other. This can happen when the CI workflow relies on the state of a previous run to determine the configuration of the next run.

Q: Why are inter-run dependencies a problem in CI?

A: Inter-run dependencies can lead to subtle and hard-to-track-down issues in CI. They can cause unexpected behavior, incorrect results, and even crashes. Moreover, they can make it difficult to debug and troubleshoot issues in CI.

Q: How can I identify inter-run dependencies in my CI workflow?

A: To identify inter-run dependencies in your CI workflow, you can follow these steps:

  1. Review your CI workflow: Review your CI workflow to see if it relies on the state of a previous run.
  2. Check for shared build folders: Check if your CI workflow uses shared build folders, which can lead to inter-run dependencies.
  3. Look for conditional builds: Look for conditional builds that depend on the state of a previous run.
  4. Use a CI tool with built-in dependency analysis: Use a CI tool that has built-in dependency analysis to help identify inter-run dependencies.

Q: How can I avoid inter-run dependencies in my CI workflow?

A: To avoid inter-run dependencies in your CI workflow, you can follow these best practices:

  1. Use a clean build folder: Use a clean build folder for each CI run to avoid carrying over state from previous runs.
  2. Use a separate build config: Use a separate build config for each CI run to avoid interfering with each other.
  3. Use CMake's/ninja's dependency analysis: Rely on CMake's/ninja's dependency analysis to decide if the build files from the previous run are still valid or need to be re-built.
  4. Implement a CI workflow with built-in dependency analysis: Implement a CI workflow with built-in dependency analysis to help identify and avoid inter-run dependencies.

Q: What are some common pitfalls to avoid when trying to avoid inter-run dependencies?

A: Some common pitfalls to avoid when trying to avoid inter-run dependencies include:

  1. Not using a clean build folder: Not using a clean build folder can lead to inter-run dependencies.
  2. Not using a separate build config: Not using a separate build config can lead to inter-run dependencies.
  3. Not relying on CMake's/ninja's dependency analysis: Not relying on CMake's/ninja's dependency analysis can lead to inter-run dependencies.
  4. Not implementing a CI workflow with built-in dependency analysis: Not implementing a CI workflow with built-in dependency analysis can lead to inter-run dependencies.

Q: How can I troubleshoot inter-run dependencies in my CI workflow?

A: To troubleshoot inter-run dependencies in your CI workflow, you can follow these steps:

  1. Review your CI workflow: Review your CI workflow to see if it relies on the state of a previous run.
  2. Check for shared build folders: Check if your CI workflow uses shared build folders, which can lead to inter-run dependencies.
  3. Look for conditional builds: Look for conditional builds that depend on the state of a previous run.
  4. Use a CI tool with built-in dependency analysis: Use a CI tool that has built-in dependency analysis to help identify inter-run dependencies.
  5. Implement a CI workflow with built-in dependency analysis: Implement a CI workflow with built-in dependency analysis to help identify and troubleshoot inter-run dependencies.

Conclusion

Inter-run dependencies can lead to subtle and hard-to-track-down issues in CI. By following the best practices outlined in this article, you can avoid inter-run dependencies and ensure that your CI workflow is reliable and efficient. Remember to review your CI workflow, check for shared build folders, look for conditional builds, and use a CI tool with built-in dependency analysis to help identify and troubleshoot inter-run dependencies.