docs/contributing/infrastructure.md - devtools/devtools-frontend - Git at Google

 # Infrastructure

 Chromium DevTools has an infrastructure component that consists of
 recipes that define how to build and test the frontend in CQ and CI
 plus a set of rollers to automate dependency updates.

 ## Overview of the code

 The configuration for the DevTools infrastructure is in the
 [`infra/config`](https://chromium.googlesource.com/devtools/devtools-frontend/+/refs/heads/infra/config)
 branch. The recipes are located in the
 [`chromium/tools/build`](https://chromium.googlesource.com/chromium/tools/build/+/refs/heads/main)
 repository.

 [Luci-config app](https://config.luci.app) is consuming the configuration from infra/config. You can force refresh from the app. DevTools configuration is located [here](https://chrome-internal.googlesource.com/infradata/config/+/master/configs/luci-config/projects.cfg).

 ## Checking out the infra config branch

 ```bash
 mkdir devtools-infra
 cd devtools-infra
 fetch devtools-frontend
 cd devtools-frontend
 git checkout infra/config
 ```

 Run `git clean -fd` and remove the rest of the remaining files from the `main`
 branch.

 ## Submitting an infra config change

 First, create a branch for the change and set upstream to the `infra/config`:

 ```bash
 git new-branch branch-name --upstream_current
 ```

 - `buckets/try.star`: configurations for default try-jobs for a CL.
 - `buckets/try-misc.star`: configurations for additional builders that
   can be manually added to CLs in Gerrit or via `git cl try`.
 - `buckets/cpp_debugging_extension.star`: configurations for the C++
   debugging extension tests.
 - `buckets/serving_app.star`: configurations for the DevTools server
   app.
 - `buckets/ci.star`: configurations to run on the main branch after a CL
   is submitted also known as CI or Waterfall builders.
 - `buckets/ci-hp.star`: configurations for the highly privileged
   builders that rolls dependencies.

 After you update a `.star` file, re-generate generated files using
 `lucicfg main.star`.

 These `.star` definitions roughly correspond to the CI console view
 https://ci.chromium.org/ui/p/devtools-frontend.

 Run `git cl upload`. Infra changes are submitted similar to the regular
 frontend CLs using `git cl upload`. After a review on Gerrit, the change
 will be merged into the infra branch.

 Note that the changes made in the CL are not picked up by the bots before the
 change is merged. After the CL is merged, the change will be deployed to the
 bots.

 ## Submitting a recipe change

 Follow the instructions at
 https://chromium.googlesource.com/chromium/tools/build/+/refs/heads/main/recipes/README.md
 and upload a CL for
 [`chromium/tools/build`](https://chromium.googlesource.com/chromium/tools/build/+/refs/heads/main).

 It's good practice to also manually test your recipes. You can test your recipe
 changes against a build that was performed with the same recipes. To do so
 follow these steps:
 - authenticate with `led auth-login`
 - select a particular build that ran with your target recipe ([example](https://ci.chromium.org/ui/p/devtools-frontend/builders/try/dtf_linux_dbg/14161))
 - got to Infra tab and collect the Buildbucket id (8700153319150087425 for the example above)
 - run `led get-build --real-build 8700153319150087425 | led edit-recipe-bundle | led edit-system -p 25 | led launch` while in your local recipe checkout
 - collect the output link to your test build and verify that you got the expected result

 ## Pin older version of DevTools recipes to a branch

 Updating a recipe that depends on DevTools repo recent changes can break the
 build in beta/stable/extended branches. If those changes cannot be back-merged
 into the branches you can pin the older version of the recipe to the branches in
 infra/config.

 To do so update the `legacy_recipe` config in `definitions.star` with the number
 of the last branch you need the old version of the recipe to run on and with the
 revision hash of that version. Branches with number higher than the one you
 configured will run ToT recipe version. [Example](https://crrev.com/c/7003685)

 ## Updating test commands in the infrastructure

 The DevTools recipes are defined in
 [`chromium/tools/build`](https://chromium.googlesource.com/chromium/tools/build/+/refs/heads/main)
 repository. Once a change is made there, the recipes are packaged
 as a cipd package and the `infra/config` data defines how to fetch that
 cipd package. The recipes are bundled by
 https://ci.chromium.org/ui/p/chrome/builders/official.infra/recipe-bundler.

 DevTools recipes live at
 https://chromium.googlesource.com/chromium/tools/build/+/refs/heads/main/recipes/recipes/devtools/.

 ## Determining if a change needs to run tests

 The
 [`try.star`](https://chromium.googlesource.com/devtools/devtools-frontend/+/refs/heads/infra/config/buckets/try.star)
 file in the `infra/config` branch contains the logic that determines
 which builders are needed to verify a CQ. See `custom_locationsfilters`
 for the current logic.

 Some of the filters currently in use are:

 - `cpp_debug_extension` builders only trigger on changes related to the extension
 - `dtf_check_no_bundle` builder only trigger on GN changes
 - all other builders will not trigger if only documentation files are updated

 ## Branch cutting process

 At the end of every release cycle Chromium will cut a new branch for the current release.

 The branch cut process for DevTools is as simple as updating the beta, stable
 and extended branch numbers in infra/config (example [CL](https://crrev.com/c/6850649)):

 - checkout infra/config branch
 - pull and create a new branch ([see](#Submitting an infra config change))
 - update the definitions.star file:
   - extended number gets updated every second release:
     - if the extended number is equal to the stable number, then update
       extended to the current beta number
     - otherwise update it to the current stable number
   - stable number updates to the current beta number
   - beta number updates to the Chromium beta brunch number ([see](https://chromiumdash.appspot.com/branches))
 - regenerate the cfg files (`lucicfg main.star`), commit, upload and add
   liviurau@chromium.org as reviewer (or another infra team member)

 Changing these numbers will reconfigure the CI and CQ for [beta](https://ci.chromium.org/p/devtools-frontend/g/beta/console),
 [stable](https://ci.chromium.org/p/devtools-frontend/g/stable/console) and
 [extended](https://ci.chromium.org/p/devtools-frontend/g/extended/console) branches.
 After landing the change the three branch consoles will get reset.

 ## Toggle tree closing behaviour on CI builders

 Sometimes we might need to avoid a misbehaving builder closing the tree. Or maybe
 we need to make a FYI builder a tree closer.

 To do so find your builder buckets/ci.star file and toggle the
 `notification_muted` property (defaults to False if not present). Setting the
 property to True/False will remove/add the tree closer notifier for this builder.
 Make sure you regenerated the cfg files and upload your changes. [Example](https://crrev.com/c/6903184).

 ## Toggle blocking behaviour of CQ builders

 CQ builders come in 3 flavors:

 - regular try builder: will always prevent a CL from landing when the builder
   fails
 - includable builder: will run only if explicitly added to a CQ run and will
   prevent a CL from landing if the builder fails
 - experimental builder: will run a percentage of the times it gets an
   opportunity run and will not block the CL from landing if the builder fails

 To toggle this behaviour you need to edit `buckets/try.star` file ([example](https://crrev.com/c/6903181)):

 - all builders must be enumerated in `cq_builders.devtools_builders` list
 - to make a builder includable add it's name `cq_builders.includable_only_builders`
   list; remove it from the list to make it a regular builder
 - to make a builder experimental add it's name `cq_builders.experiment_builders`
   dictionary together with the desired experiment rate percentage; remove it
   from the list to make it a regular builder

 ## Adding a new builder in CQ

 To add a new try-builder edit the [try.start](https://chromium.googlesource.com/devtools/devtools-frontend/+/refs/heads/infra/config/buckets/try.star) file to call one of the
 existing functions that generate builder definitions:

 - `try_builder` used for builder with recipes that do not orchestrate other
   builders:
   - build only builders (`dtf_check_no_bundle`)
   - chromium builders (`devtools_frontend_linux_blink_light_rel_fastbuild`)
 - `try_pair` used for builders with orchestrating recipes (delegates to a
   compilator builder before delegating testing to swarming)

 Alternatively define your own builder function and call it for the instances you
 need (see `presubmit_builder` and `cpp_debug_extension_try`).

 You will need add your new builder to the `cq_builders.devtools_builders` list.

 To control the CL blocking behaviour of your builder see above.

 To control if the builder should be not present in the CQ for branches, add your
 builder to `cq_builders.chromium_builders` list.

 ## Adding a new builder in CI

 To add a new try-builder edit the [ci.start](https://chromium.googlesource.com/devtools/devtools-frontend/+/refs/heads/infra/config/buckets/ci.star) file to add a new
 `builder_descriptor` to the `builders` of `generate_ci_configs` function call.

 In your descriptor decide for the name of builder, the recipe, any other custom
 properties you might need and for which configurations (consoles) to include
 your builder (`ci` stands for the main waterfall console). [Example](https://chromium.googlesource.com/devtools/devtools-frontend/+/refs/heads/infra/config/buckets/ci.star#:~:text=name%20%3D%20%22-,Linux,-Compile%20Debug%22%2C).

 ## Anatomy of a CQ build

 In CQ the builders that get most attention are `dtf_*_rel` builders. These builders
 run the devtools/trybot_tester recipe and are responsible with building DevTools
 Frontend and running our tests.

 Below is a detailed description of what happens in such a build:

 - The recipe will perform the `bot_update` and `gclient runhooks` step where
   the tip-of-tree for devtools-frontend gets checked out, your changes get
   patched on top of it and dependencies get updated.
 - The compilator bot get triggered (`initialization` step)
 - We wait for the compilator bot to finish. This bot is responsible for
   the actual build of devtools-frontend.
   - It does a `bot_update` of its own
   - Generates the GN files (`gn` step)
   - Compiles (`compile`) the project
   - Reads the e2e test lists
   - Creates a CAS archive with project and the compilation output
   - Outputs the `compilator_properties`
 - Once the compilator is done we read the `compilator_properties` to find
   - the `cas_digest` to be used when triggering tests on swarming
   - the `e2e_test_list` for sharding the e2e tests execution
 - Write the e2e test list at the location where building would have written it
 - The default test run phase starts at `Run tests` step:
   - We trigger all tests on swarming in parallel (`Trigger Tests`) substep.
     - For all types of tests we calculate the command we want to run on swarming
       and trigger a task with that command and the collected CAS digest
     - Before calculating the command for e2e test we read the test list and
       and split it in a number of shards. Each shard will have the allocated
       tests specified in the command.
   - We wait for all swarming task to complete
 - Next we re-run the failed tests in attempt to exonerate their initial
   failures (`Flake exoneration attempt` step):
   - We query ResultDB for any tests that might have failed
   - We collect the failed test names and construct new commands to re-run
     them on new swarming tasks
   - We wait for all swarming task to complete
 - Finally we will stress test the tests that were added/modified by the
   current CL in the `Detect flakes in new tests` step
   - Run `git diff` to determine which tests were added/modified
   - Construct the command to be run on swarming
   - Trigger and wait for the swarming tasks to finish
 - Calculate the outcome of the builder:
   - fail the builder if tests failed in the default run and the exoneration
     run was unsuccessful
   - fail the builder if tests failed in the deflaking phase
   - otherwise report build as passing

 ## Skip flake detection

 Test that are already flaky can end up being updated in CLs that do not deal
 with the original flakiness nor can be blamed for introducing or increasing the
 flakiness of the test. However CQ builder will fail in Flake Detection steps
 because they picked up the test as it was being touched.

 You can skip Flake Detection for your tests by adding the `Skip-Flake-Detection`
 CL footer (see example [CL](https://crrev.com/c/6994031)). Make sure you use the
 full path to your test.

 ### Common build failures

 The first place where a build usually fails is on `bot_update` and this usually
 happens because your changes cannot be applied on top of the current tip-of-tree.
 Rebase your CL and solve any merge conflicts and this failure will go away.

 Another common failure is a compilation failure. You can inspect the compilator
 builder (`dtf_*_compiler_rel`) separately by following the link next to the
 `compilator steps` step.

 If you have too many tests failing in the default phase the exoneration phase
 gets skipped.

 A test might not get exonerated in your build even if your CL does not touch
 anything related to it. The exoneration phase will re-run previously failing
 tests a number of times and at any point the test passes the tests gets
 exonerated. Therefore a test can have a recent history of getting exonerated
 even if it consistently failed 4 times out of 5 runs for some time. Try to
 correlate your failure with a luci-analysis report on this test and skip it
 until the flakiness gets resolved.

 ### Clobber a builder's cache

 Builder bots utilize caching for project checkouts to speed up updates. This
 cache includes the build output directory (`/out`). Occasionally, stale files
 within these directories can interfere with the build process or test execution.

 If you suspect a cache issue, you can clear (clobber) the cache for a specific
 builder. This requires a local Chromium checkout to access the necessary utility
 script.

 Run the following command from the root of your Chromium checkout:

 ```bash
 ./tools/infra/builder-cache-clobber.py -S https://chromium-swarm.appspot.com/ --builder "Stand-alone Mac-arm64" --bucket ci --project devtools-frontend
 ```

 #### Note about caches on try bots:

 Try bots (CQ) operate in tester/compilator pairs. When clearing caches, ensure
 you target both builders in the pair. For example, if you clear the cache for
 `dtf_mac_arm64_rel`, you must also clear it for `dtf_mac_arm64_compile_rel`.

 ## Luci Analysis configuration

 [Luci Analysis](go/luci-analysis) is a tool that helps you understand the
 impact of test failures.

 You can find the DevTools configuration in [luci-analysis.cfg](https://chromium.googlesource.com/devtools/devtools-frontend/+/refs/heads/infra/config/luci-analysis.cfg).

 We configure the rules for test failure clustering based on _file_/_suite_ and
 _testcase_ names.

 A policy named `too-many-failures` is defined in the configuration with
 activation/deactivation thresholds and a bug template to be used when creating
 a new bug. The bugs will be automatically created in Buganizer on the configured
 default component (or on the component specified in a `DIR_METADATA` file on the
 ancestor path of the failing test file).

 After updating the `luci-analysis.cfg` file make sure you run `lucicfg main.star` to
 refresh the copy of this file in the `generated/` folder.

 ## Autorollers

 ### Rolling DevTools to Chromium

 A [Skia autoroller](https://skia.googlesource.com/buildbot/+/main/autoroll/README.md)
 is responsible for rolling DevTools to Chromium. Follow the links to inspect the
 [status](https://autoroll.skia.org/r/devtools-frontend-chromium?tab=status) of
 the roller.

 To update the configuration you will need to clone the skia [repo](sso://skia/skia-autoroll-internal-config)
 and modify the `skia-infra-public/devtools-frontend-chromium.cfg` file ([example](https://review.skia.org/1014616)).

 ### Rolling dependencies to DevTools

 To roll all DevTool's dependencies we rely on the [Roll deps and chromium pin
 into devtools-frontend](https://ci.chromium.org/ui/p/devtools-frontend/builders/ci-hp/Roll%20deps%20and%20chromium%20pin%20into%20devtools-frontend)
 builder that runs on the [infra](https://ci.chromium.org/ui/p/devtools-frontend/g/infra/builders)
 console.

 The builder is scheduled to run every day at 05 and 14 hours. In the [recipe](https://source.chromium.org/chromium/infra/infra_superproject/+/main:build/recipes/recipes/devtools/auto_roll_incoming.py?q=file:recipes%2Fdevtools%2Fauto_roll_incoming.py)
 that runs on this builder you can configure dependencies that you need excluded
 from the rolls and reviewer emails. The recipe uses the V8's autorolling rolling
 [module](https://source.chromium.org/chromium/infra/infra_superproject/+/main:build/recipes/recipe_modules/v8_auto_roller/api.py),
 that offers support for trusted and untrusted dependencies ([regular](https://source.chromium.org/chromium/infra/infra_superproject/+/main:build/recipes/recipe_modules/v8_auto_roller/deps_handlers.py)), [CfT](https://source.chromium.org/chromium/infra/infra_superproject/+/main:build/recipes/recipe_modules/v8_auto_roller/chrome_handler.py) pin rolling, and [script based](https://source.chromium.org/chromium/infra/infra_superproject/+/main:build/recipes/recipe_modules/v8_auto_roller/script_handlers.py) special rolls.
	# Infrastructure

	Chromium DevTools has an infrastructure component that consists of
	recipes that define how to build and test the frontend in CQ and CI
	plus a set of rollers to automate dependency updates.

	## Overview of the code

	The configuration for the DevTools infrastructure is in the
	[`infra/config`](https://chromium.googlesource.com/devtools/devtools-frontend/+/refs/heads/infra/config)
	branch. The recipes are located in the
	[`chromium/tools/build`](https://chromium.googlesource.com/chromium/tools/build/+/refs/heads/main)
	repository.

	[Luci-config app](https://config.luci.app) is consuming the configuration from infra/config. You can force refresh from the app. DevTools configuration is located [here](https://chrome-internal.googlesource.com/infradata/config/+/master/configs/luci-config/projects.cfg).

	## Checking out the infra config branch

	```bash
	mkdir devtools-infra
	cd devtools-infra
	fetch devtools-frontend
	cd devtools-frontend
	git checkout infra/config
	```

	Run `git clean -fd` and remove the rest of the remaining files from the `main`
	branch.

	## Submitting an infra config change

	First, create a branch for the change and set upstream to the `infra/config`:

	```bash
	git new-branch branch-name --upstream_current
	```

	- `buckets/try.star`: configurations for default try-jobs for a CL.
	- `buckets/try-misc.star`: configurations for additional builders that
	can be manually added to CLs in Gerrit or via `git cl try`.
	- `buckets/cpp_debugging_extension.star`: configurations for the C++
	debugging extension tests.
	- `buckets/serving_app.star`: configurations for the DevTools server
	app.
	- `buckets/ci.star`: configurations to run on the main branch after a CL
	is submitted also known as CI or Waterfall builders.
	- `buckets/ci-hp.star`: configurations for the highly privileged
	builders that rolls dependencies.

	After you update a `.star` file, re-generate generated files using
	`lucicfg main.star`.

	These `.star` definitions roughly correspond to the CI console view
	https://ci.chromium.org/ui/p/devtools-frontend.

	Run `git cl upload`. Infra changes are submitted similar to the regular
	frontend CLs using `git cl upload`. After a review on Gerrit, the change
	will be merged into the infra branch.

	Note that the changes made in the CL are not picked up by the bots before the
	change is merged. After the CL is merged, the change will be deployed to the
	bots.

	## Submitting a recipe change

	Follow the instructions at
	https://chromium.googlesource.com/chromium/tools/build/+/refs/heads/main/recipes/README.md
	and upload a CL for
	[`chromium/tools/build`](https://chromium.googlesource.com/chromium/tools/build/+/refs/heads/main).

	It's good practice to also manually test your recipes. You can test your recipe
	changes against a build that was performed with the same recipes. To do so
	follow these steps:
	- authenticate with `led auth-login`
	- select a particular build that ran with your target recipe ([example](https://ci.chromium.org/ui/p/devtools-frontend/builders/try/dtf_linux_dbg/14161))
	- got to Infra tab and collect the Buildbucket id (8700153319150087425 for the example above)
	- run `led get-build --real-build 8700153319150087425 \| led edit-recipe-bundle \| led edit-system -p 25 \| led launch` while in your local recipe checkout
	- collect the output link to your test build and verify that you got the expected result

	## Pin older version of DevTools recipes to a branch

	Updating a recipe that depends on DevTools repo recent changes can break the
	build in beta/stable/extended branches. If those changes cannot be back-merged
	into the branches you can pin the older version of the recipe to the branches in
	infra/config.

	To do so update the `legacy_recipe` config in `definitions.star` with the number
	of the last branch you need the old version of the recipe to run on and with the
	revision hash of that version. Branches with number higher than the one you
	configured will run ToT recipe version. [Example](https://crrev.com/c/7003685)

	## Updating test commands in the infrastructure

	The DevTools recipes are defined in
	[`chromium/tools/build`](https://chromium.googlesource.com/chromium/tools/build/+/refs/heads/main)
	repository. Once a change is made there, the recipes are packaged
	as a cipd package and the `infra/config` data defines how to fetch that
	cipd package. The recipes are bundled by
	https://ci.chromium.org/ui/p/chrome/builders/official.infra/recipe-bundler.

	DevTools recipes live at
	https://chromium.googlesource.com/chromium/tools/build/+/refs/heads/main/recipes/recipes/devtools/.

	## Determining if a change needs to run tests

	The
	[`try.star`](https://chromium.googlesource.com/devtools/devtools-frontend/+/refs/heads/infra/config/buckets/try.star)
	file in the `infra/config` branch contains the logic that determines
	which builders are needed to verify a CQ. See `custom_locationsfilters`
	for the current logic.

	Some of the filters currently in use are:

	- `cpp_debug_extension` builders only trigger on changes related to the extension
	- `dtf_check_no_bundle` builder only trigger on GN changes
	- all other builders will not trigger if only documentation files are updated

	## Branch cutting process

	At the end of every release cycle Chromium will cut a new branch for the current release.

	The branch cut process for DevTools is as simple as updating the beta, stable
	and extended branch numbers in infra/config (example [CL](https://crrev.com/c/6850649)):

	- checkout infra/config branch
	- pull and create a new branch ([see](#Submitting an infra config change))
	- update the definitions.star file:
	- extended number gets updated every second release:
	- if the extended number is equal to the stable number, then update
	extended to the current beta number
	- otherwise update it to the current stable number
	- stable number updates to the current beta number
	- beta number updates to the Chromium beta brunch number ([see](https://chromiumdash.appspot.com/branches))
	- regenerate the cfg files (`lucicfg main.star`), commit, upload and add
	liviurau@chromium.org as reviewer (or another infra team member)

	Changing these numbers will reconfigure the CI and CQ for [beta](https://ci.chromium.org/p/devtools-frontend/g/beta/console),
	[stable](https://ci.chromium.org/p/devtools-frontend/g/stable/console) and
	[extended](https://ci.chromium.org/p/devtools-frontend/g/extended/console) branches.
	After landing the change the three branch consoles will get reset.

	## Toggle tree closing behaviour on CI builders

	Sometimes we might need to avoid a misbehaving builder closing the tree. Or maybe
	we need to make a FYI builder a tree closer.

	To do so find your builder buckets/ci.star file and toggle the
	`notification_muted` property (defaults to False if not present). Setting the
	property to True/False will remove/add the tree closer notifier for this builder.
	Make sure you regenerated the cfg files and upload your changes. [Example](https://crrev.com/c/6903184).

	## Toggle blocking behaviour of CQ builders

	CQ builders come in 3 flavors:

	- regular try builder: will always prevent a CL from landing when the builder
	fails
	- includable builder: will run only if explicitly added to a CQ run and will
	prevent a CL from landing if the builder fails
	- experimental builder: will run a percentage of the times it gets an
	opportunity run and will not block the CL from landing if the builder fails

	To toggle this behaviour you need to edit `buckets/try.star` file ([example](https://crrev.com/c/6903181)):

	- all builders must be enumerated in `cq_builders.devtools_builders` list
	- to make a builder includable add it's name `cq_builders.includable_only_builders`
	list; remove it from the list to make it a regular builder
	- to make a builder experimental add it's name `cq_builders.experiment_builders`
	dictionary together with the desired experiment rate percentage; remove it
	from the list to make it a regular builder

	## Adding a new builder in CQ

	To add a new try-builder edit the [try.start](https://chromium.googlesource.com/devtools/devtools-frontend/+/refs/heads/infra/config/buckets/try.star) file to call one of the
	existing functions that generate builder definitions:

	- `try_builder` used for builder with recipes that do not orchestrate other
	builders:
	- build only builders (`dtf_check_no_bundle`)
	- chromium builders (`devtools_frontend_linux_blink_light_rel_fastbuild`)
	- `try_pair` used for builders with orchestrating recipes (delegates to a
	compilator builder before delegating testing to swarming)

	Alternatively define your own builder function and call it for the instances you
	need (see `presubmit_builder` and `cpp_debug_extension_try`).

	You will need add your new builder to the `cq_builders.devtools_builders` list.

	To control the CL blocking behaviour of your builder see above.

	To control if the builder should be not present in the CQ for branches, add your
	builder to `cq_builders.chromium_builders` list.

	## Adding a new builder in CI

	To add a new try-builder edit the [ci.start](https://chromium.googlesource.com/devtools/devtools-frontend/+/refs/heads/infra/config/buckets/ci.star) file to add a new
	`builder_descriptor` to the `builders` of `generate_ci_configs` function call.

	In your descriptor decide for the name of builder, the recipe, any other custom
	properties you might need and for which configurations (consoles) to include
	your builder (`ci` stands for the main waterfall console). [Example](https://chromium.googlesource.com/devtools/devtools-frontend/+/refs/heads/infra/config/buckets/ci.star#:~:text=name%20%3D%20%22-,Linux,-Compile%20Debug%22%2C).

	## Anatomy of a CQ build

	In CQ the builders that get most attention are `dtf_*_rel` builders. These builders
	run the devtools/trybot_tester recipe and are responsible with building DevTools
	Frontend and running our tests.

	Below is a detailed description of what happens in such a build:

	- The recipe will perform the `bot_update` and `gclient runhooks` step where
	the tip-of-tree for devtools-frontend gets checked out, your changes get
	patched on top of it and dependencies get updated.
	- The compilator bot get triggered (`initialization` step)
	- We wait for the compilator bot to finish. This bot is responsible for
	the actual build of devtools-frontend.
	- It does a `bot_update` of its own
	- Generates the GN files (`gn` step)
	- Compiles (`compile`) the project
	- Reads the e2e test lists
	- Creates a CAS archive with project and the compilation output
	- Outputs the `compilator_properties`
	- Once the compilator is done we read the `compilator_properties` to find
	- the `cas_digest` to be used when triggering tests on swarming
	- the `e2e_test_list` for sharding the e2e tests execution
	- Write the e2e test list at the location where building would have written it
	- The default test run phase starts at `Run tests` step:
	- We trigger all tests on swarming in parallel (`Trigger Tests`) substep.
	- For all types of tests we calculate the command we want to run on swarming
	and trigger a task with that command and the collected CAS digest
	- Before calculating the command for e2e test we read the test list and
	and split it in a number of shards. Each shard will have the allocated
	tests specified in the command.
	- We wait for all swarming task to complete
	- Next we re-run the failed tests in attempt to exonerate their initial
	failures (`Flake exoneration attempt` step):
	- We query ResultDB for any tests that might have failed
	- We collect the failed test names and construct new commands to re-run
	them on new swarming tasks
	- We wait for all swarming task to complete
	- Finally we will stress test the tests that were added/modified by the
	current CL in the `Detect flakes in new tests` step
	- Run `git diff` to determine which tests were added/modified
	- Construct the command to be run on swarming
	- Trigger and wait for the swarming tasks to finish
	- Calculate the outcome of the builder:
	- fail the builder if tests failed in the default run and the exoneration
	run was unsuccessful
	- fail the builder if tests failed in the deflaking phase
	- otherwise report build as passing

	## Skip flake detection

	Test that are already flaky can end up being updated in CLs that do not deal
	with the original flakiness nor can be blamed for introducing or increasing the
	flakiness of the test. However CQ builder will fail in Flake Detection steps
	because they picked up the test as it was being touched.

	You can skip Flake Detection for your tests by adding the `Skip-Flake-Detection`
	CL footer (see example [CL](https://crrev.com/c/6994031)). Make sure you use the
	full path to your test.

	### Common build failures

	The first place where a build usually fails is on `bot_update` and this usually
	happens because your changes cannot be applied on top of the current tip-of-tree.
	Rebase your CL and solve any merge conflicts and this failure will go away.

	Another common failure is a compilation failure. You can inspect the compilator
	builder (`dtf_*_compiler_rel`) separately by following the link next to the
	`compilator steps` step.

	If you have too many tests failing in the default phase the exoneration phase
	gets skipped.

	A test might not get exonerated in your build even if your CL does not touch
	anything related to it. The exoneration phase will re-run previously failing
	tests a number of times and at any point the test passes the tests gets
	exonerated. Therefore a test can have a recent history of getting exonerated
	even if it consistently failed 4 times out of 5 runs for some time. Try to
	correlate your failure with a luci-analysis report on this test and skip it
	until the flakiness gets resolved.

	### Clobber a builder's cache

	Builder bots utilize caching for project checkouts to speed up updates. This
	cache includes the build output directory (`/out`). Occasionally, stale files
	within these directories can interfere with the build process or test execution.

	If you suspect a cache issue, you can clear (clobber) the cache for a specific
	builder. This requires a local Chromium checkout to access the necessary utility
	script.

	Run the following command from the root of your Chromium checkout:

	```bash
	./tools/infra/builder-cache-clobber.py -S https://chromium-swarm.appspot.com/ --builder "Stand-alone Mac-arm64" --bucket ci --project devtools-frontend
	```

	#### Note about caches on try bots:

	Try bots (CQ) operate in tester/compilator pairs. When clearing caches, ensure
	you target both builders in the pair. For example, if you clear the cache for
	`dtf_mac_arm64_rel`, you must also clear it for `dtf_mac_arm64_compile_rel`.

	## Luci Analysis configuration

	[Luci Analysis](go/luci-analysis) is a tool that helps you understand the
	impact of test failures.

	You can find the DevTools configuration in [luci-analysis.cfg](https://chromium.googlesource.com/devtools/devtools-frontend/+/refs/heads/infra/config/luci-analysis.cfg).

	We configure the rules for test failure clustering based on _file_/_suite_ and
	_testcase_ names.

	A policy named `too-many-failures` is defined in the configuration with
	activation/deactivation thresholds and a bug template to be used when creating
	a new bug. The bugs will be automatically created in Buganizer on the configured
	default component (or on the component specified in a `DIR_METADATA` file on the
	ancestor path of the failing test file).

	After updating the `luci-analysis.cfg` file make sure you run `lucicfg main.star` to
	refresh the copy of this file in the `generated/` folder.

	## Autorollers

	### Rolling DevTools to Chromium

	A [Skia autoroller](https://skia.googlesource.com/buildbot/+/main/autoroll/README.md)
	is responsible for rolling DevTools to Chromium. Follow the links to inspect the
	[status](https://autoroll.skia.org/r/devtools-frontend-chromium?tab=status) of
	the roller.

	To update the configuration you will need to clone the skia [repo](sso://skia/skia-autoroll-internal-config)
	and modify the `skia-infra-public/devtools-frontend-chromium.cfg` file ([example](https://review.skia.org/1014616)).

	### Rolling dependencies to DevTools

	To roll all DevTool's dependencies we rely on the [Roll deps and chromium pin
	into devtools-frontend](https://ci.chromium.org/ui/p/devtools-frontend/builders/ci-hp/Roll%20deps%20and%20chromium%20pin%20into%20devtools-frontend)
	builder that runs on the [infra](https://ci.chromium.org/ui/p/devtools-frontend/g/infra/builders)
	console.

	The builder is scheduled to run every day at 05 and 14 hours. In the [recipe](https://source.chromium.org/chromium/infra/infra_superproject/+/main:build/recipes/recipes/devtools/auto_roll_incoming.py?q=file:recipes%2Fdevtools%2Fauto_roll_incoming.py)
	that runs on this builder you can configure dependencies that you need excluded
	from the rolls and reviewer emails. The recipe uses the V8's autorolling rolling
	[module](https://source.chromium.org/chromium/infra/infra_superproject/+/main:build/recipes/recipe_modules/v8_auto_roller/api.py),
	that offers support for trusted and untrusted dependencies ([regular](https://source.chromium.org/chromium/infra/infra_superproject/+/main:build/recipes/recipe_modules/v8_auto_roller/deps_handlers.py)), [CfT](https://source.chromium.org/chromium/infra/infra_superproject/+/main:build/recipes/recipe_modules/v8_auto_roller/chrome_handler.py) pin rolling, and [script based](https://source.chromium.org/chromium/infra/infra_superproject/+/main:build/recipes/recipe_modules/v8_auto_roller/script_handlers.py) special rolls.