Flutter's Build Infrastructure

This directory exists to support building Flutter on our build infrastructure.

The results of such builds are viewable at:

The external master pages for the Chromium infra bots do not allow forcing new builds. Contact @eseidelGoogle or another member of Google's Flutter team if you need to do that.

The Cirrus-based bots run the test.dart script for each PR and submission. It does testing for the tools, for the framework, and (for submitted changes only) rebuilds and updates the master branch API docs staging site. For tagged dev and beta builds, it also builds and deploys the gallery app to the app stores.

The rest of this document discusses only the Chromium infra bots.

This infrastructure is broken into two parts. A buildbot master specified by our builders.pyl file, and a set of recipes which we run on that master. Both of these technologies are highly specific to Google‘s Chromium project. We’re just borrowing some of their infrastructure.


  • install depot_tools
  • Python package installer: sudo apt-get install python-pip
  • Python coverage package (only needed for training_simulation): sudo pip install coverage

Getting the code

The following will get way more than just recipe code, but it will get the recipe code:

mkdir chrome_infra
cd chrome_infra
fetch infra

More detailed instructions can be found here.

Most of the functionality for recipes comes from recipe_modules, which are unfortunately spread to many separate repositories. After checking out the code search for files named api.py or example.py under infra/build.

Editing a recipe

Flutter has one recipe per repository. Currently flutter/flutter and flutter/engine:

  • build/scripts/slave/recipes/flutter/flutter.py
  • build/scripts/slave/recipes/flutter/engine.py

Recipes are just Python. They are documented by the luci/recipes-py github project.

The typical cycle for editing a recipe is:

  1. Make your edits (probably to files in //chrome_infra/build/scripts/slave/recipes/flutter).
  2. Run build/scripts/slave/recipes.py --use-bootstrap test train to update expected files
  3. Run build/scripts/slave/recipes.py run flutter/<repo> slavename=<slavename> mastername=client.flutter buildername=<buildername> buildnumber=1234 where <repo> is one of flutter or engine, and slavename and buildername can be looked up from the Build Properties section of a recent build.
  4. Upload the patch (git commit, git cl upload) and send it to someone in the recipes/flutter/OWNERS file for review.

Editing the client.flutter buildbot master

Flutter uses Chromium's fancy builders.pyl master generation system. Chromium hosts 100s (if not 1000s) of buildbot masters and thus has lots of infrastructure for turning them up and down. Eventually all of buildbot is planned to be replaced by other infrastructure, but for now flutter has its own client.flutter master.

You would need to edit client.flutter's master in order to add slaves (talk to @eseidelGoogle), add builder groups, or to change the html layout of https://build.chromium.org/p/client.flutter. Carefully follow the builders.pyl docs to do so.

Future Directions

We would like to host our own recipes instead of storing them in build. Support for cross-repository recipes is in-progress. If you view the git log of this directory, you‘ll see we initially tried, but it’s not quite ready.

Android Tools

The Android SDK and NDK used by Flutter's Chrome infra bots are stored in Google Cloud. During the build a bot runs the download_android_tools.py script that downloads the required version of the Android SDK into dev/bots/android_tools.

To check which components are currently installed, download the current SDK stored in Google Cloud using the download_android_tools.py script, then dev/bots/android_tools/sdk/tools/bin/sdkmanager --list. If you find that some components need to be updated or installed, follow the steps below:

How to update Android SDK on Google Cloud Storage

  1. Run Android SDK Manager and update packages $ dev/bots/android_tools/sdk/tools/android update sdk Use android.bat on Windows.

  2. Use the UI to choose the packages you want to install and/or update.

  3. Run dev/bots/android_tools/sdk/tools/bin/sdkmanager --update. On Windows, run sdkmanager.bat instead. If the process fails with an error saying that it is unable to move files (Windows makes files and directories read-only when another process is holding them open), make a copy of the dev/bots/android_tools/sdk/tools directory, run the sdkmanager.bat from the copy, and use the --sdk_root option pointing at dev/bots/android_tools/sdk.

  4. Run dev/bots/android_tools/sdk/tools/bin/sdkmanager --licenses and accept the licenses for the newly installed components. It also helps to run this command a second time and make sure that it prints “All SDK package licenses accepted”.

  5. Run upload_android_tools.py -t sdk $ dev/bots/upload_android_tools.py -t sdk

How to update Android NDK on Google Cloud Storage

  1. Download a new NDK binary (e.g. android-ndk-r10e-linux-x86_64.bin)

  2. cd dev/bots/android_tools $ cd dev/bots/android_tools

  3. Remove the old ndk directory $ rm -rf ndk

  4. Run the new NDK binary file $ ./android-ndk-r10e-linux-x86_64.bin

  5. Rename the extracted directory to ndk $ mv android-ndk-r10e ndk

  6. Run upload_android_tools.py -t ndk $ cd ../.. $ dev/bots/upload_android_tools.py -t ndk