Reland "[luci_context] Move writing of LUCI_CONTEXT files to the engine core."

This is a reland of 6126bc2f1092567bb3b0d96f0381330ba01ead75

Original change's description:
> [luci_context] Move writing of LUCI_CONTEXT files to the engine core.
>
> This removes an odd file-write from 'userspace' recipe code, but also
> enables compuation of 'timeout' for the step much closer to the actual
> step execution. Specifically, this avoids having 'timeout' also cover
> the time that we block for resource contention when running multiple
> greenlets in the recipe.
>
> R=vadimsh, yiwzhang
>
> Bug: 1127089
> Change-Id: Iff59e7698e9556737a6144508c00cb3342811641
> Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/recipes-py/+/2441885
> Reviewed-by: Yiwei Zhang <yiwzhang@google.com>
> Commit-Queue: Robbie Iannucci <iannucci@chromium.org>

Bug: 1127089
Change-Id: I93cb131f174b07260641a20b5476f7a0943794d3
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/recipes-py/+/2453596
Reviewed-by: Vadim Shtayura <vadimsh@chromium.org>
Commit-Queue: Yiwei Zhang <yiwzhang@google.com>
7 files changed
tree: 3d8255439a1c41408fc74167a30930c1875ac341
  1. doc/
  2. infra/
  3. misc/
  4. recipe_engine/
  5. recipe_modules/
  6. recipe_proto/
  7. recipes/
  8. unittests/
  9. .gitattributes
  10. .gitignore
  11. .style.yapf
  12. .vpython
  13. AUTHORS
  14. codereview.settings
  15. CONTRIBUTORS
  16. LICENSE
  17. OWNERS
  18. PRESUBMIT.py
  19. README.md
  20. README.recipes.md
  21. recipes.py
README.md

Recipes

Recipes are a domain-specific language (embedded in python) for specifying sequences of subprocess calls in a cross-platform and testable way.

They allow writing build flows which integrate with the rest of LUCI.

Documentation for the recipe engine (including this file!). Take a look at the user guide for some hints on how to get started. See the implementation details doc for more detailed implementation information about the recipe engine.

Contributing

  • Sign the Google CLA.
  • Make sure your user.email and user.name are configured in git config.

Run the following to setup the code review tool and create your first review:

# Get `depot_tools` in $PATH if you don't have it
git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git $HOME/src/depot_tools
export PATH="$PATH:$HOME/src/depot_tools"

# Check out the recipe engine repo
git clone https://chromium.googlesource.com/infra/luci/recipes-py $HOME/src/recipes-py

# make your change
cd $HOME/src/recipes-py
git new-branch cool_feature
# hack hack
git commit -a -m "This is awesome"

# This will ask for your Google Account credentials.
git cl upload -s -r joe@example.com
# Wait for approval over email.
# Click "Submit to CQ" button or ask reviewer to do it for you.
# Wait for the change to be tested and landed automatically.

Use git cl help and git cl help <cmd> for more details.