Flutter LUCI Service Configurations

Contains configuration and tools related to Flutter's build infrastructure.

Configuration is generated by lucicfg, which is part of depot_tools. Rather than updating the individual .cfg files, updates should be made to config/main.star. That file can then be run to regenerate the configuration.

Updating the configuration

• Edit the desired .star files (do not edit .cfg files; those are generated).
• Execute ./config/main.star.
• Observe that the .cfg files have been updated (e.g. via git status).
• Create a pull request containing changes both to the .star files and .cfg files.
• Review and submit the pull request as normal.
• Changes propagate to LUCI automatically. Go to LUCI config UI to check that new changes have been applied.

Adding new framework test shards

This section talks about test shards defined in dev/bots/test.dart used to split framework tests into smaller chunks that can be tested in parallel. This does not refer to LUCI/Swarming shards.

When you add a new shard it does not automatically run in LUCI. To add it to LUCI you need to add a new builder in the framework_config.star. Typically, you'll add two builders, one “try” builder that tests PRs, and one “prod” builder that tests submitted PRs on the master branch.

Here's an example of a “try” builder:

    common.linux_try_builder(
        name = "Linux web_tests|web_tests",
        recipe = "flutter/flutter",
        repo = repos.FLUTTER,
        list_view_name = list_view_name,
        properties = {
            "shard": "web_tests",
            "subshards": ["0", "1", "2", "3", "4", "5", "6", "7_last"],
            "dependencies": [{"dependency": "android_sdk"}, {"dependency": "chrome_and_driver"}, {"dependency": "goldctl"}],
        },
        caches = [
            swarming.cache(name = "pub_cache", path = ".pub_cache"),
            swarming.cache(name = "android_sdk", path = "android29"),
        ],
    )

The easiest way to add a new one is to copy an existing builder and tweak the parameters.

Testing new shards

As of today, it is not possible to test configuration changes until after they propagated to LUCI. One way to mitigate the risk of breakage is to run your test shard using an existing builder. To do that, find a builder in one of the .star files (e.g. framework_config.star) that satisfies the dependencies of the new test shard, then use the led tool (bundled with depot_tools) to run it.

For example, let‘s say you are adding an integration test shard for web, and the new shard needs a Linux builder with Chrome and ChromeDriver in order to run. Luckily, there’s already the Linux web_tests builder that satisfies these dependencies. To test the new shard, use the Linux web_tests builder, but ask it to run a different shards and/or subshard. Let‘s say the new test shard is called “foo”, it has 3 subshards (0, 1, 2_last) and it’s currently staged in pull request 99999. You can run it using the following led command:

led get-builder "luci.flutter.try:Linux web_tests" \
  | led edit -pa git_ref='refs/pull/99999/head' \
  | led edit -pa git_url='https://github.com/flutter/flutter' \
  | led edit -pa shard='foo' \
  | led edit -pa subshard='1' \
  | led launch

Forcing the propagation of these configurations

One may speed up the propagation of the new configuration files by visiting the luci-config web ui, logging in, and searching for projects/flutter. from there, one may click on the projects/flutter search result and click the download icon to force an update.