tree: b7fd6a3a5f63c3dfc09fcb114cefb668e35b666e [path history] [tgz]
  1. contrib/
  2. controller/
  3. gen/
  4. gen_sdk/
  5. gen_test/
  6. references/
  7. tutorials/
  8. .gitignore

Build API

Welcome to the Build API.

Getting Started


The Build API is a CLI-only, proto based API to execute build steps. It was created to provide a stable interface for the CI builders. The proto files (in infra/proto_branched) define the services/RPCs provided by the API. The modules in controller/ are the entry points for the RPCs defined in the proto files.

Manually Calling/Testing an Endpoint

To manually call an endpoint, the gen_call_scripts process is strongly recommended, it makes calling a specific endpoint quick and easy. Please contribute new example input files when you add new endpoints!

Just in case, the general info for invoking the Build API follows, however, if you do find a use case that the gen call scripts doesn't cover for local uses, please file a bug for the CrOS Build team with the info.

The Build API is invoked via the build_api script, which takes 4 arguments; the name of the endpoint being called (e.g. chromite.api.SdkService/Create), and the request, response, and optional config protos, which are provided as paths to files containing the respective JSON or protobuf-binary encoded messages. e.g.

build_api chromite.api.SdkService/Create \
    --input-json /tmp/input.json \
    --output-json /tmp/output.json \
    --config-json /tmp/config.json

Recreating Build API Calls from Builders

It is relatively simple to duplicate calls made on a builder. This does NOT handle fetching the same version of the source, prerequisites, placing files in expected locations, etc. However, if you can satisfy the prerequisites, either by also calling the prerequisite endpoints, or just manually setting it up, you can locally duplicate the endpoint invocation.

Each endpoint call will be its own step in the Milo UI for the builder. The endpoint call steps may be top level steps, or nested arbitrarily. The step text will be something like 1. call chromite.api.SdkService/Update. All context for calling the endpoint is nested under that step. Most importantly, the request is the first link listed before the sub-steps.

  1. Follow instructions to set up the gen_call_scripts workflow for your build target.
  2. Find the Build API call you want to duplicate.
  3. Open the request, copy its contents, and paste it into the relevant service__method_input.json.
  4. Make minor edits.
    1. All endpoints
      1. Drop (or fix) the chroot's path field, if present.
        • Drop if using the default location, otherwise fix to your custom path.
        • If you‘re not sure, it’s in the default location.
    2. SysrootService/InstallPackages endpoint
      1. Unless you've manually set them up locally, drop the:
        1. chrome_dir in the chroot message.
  5. Ensure prerequisites are satisfied.
    • If in doubt, you can run every endpoint the builder ran up through the endpoint you want to run, though this may be time-consuming.
  6. Run the method__service script.
    • It'll use the input you took from the builder to run the endpoint.

Tutorials and References

See the Build API Tutorials for code lab style instructions on how to make an endpoint.

See the Build API References for a quick, detailed reference on specific topics.

Directory Reference


Make sure you've consulted the Build and CI teams when considering making breaking changes that affect the Build API.

This directory is a separate repo that contains all the raw .proto files. You will find message, service, and method definitions, and their configurations. You will need to commit and upload the proto changes separately from the chromite changes.

  • chromite/api/ contains the Build API services.
    • Except chromite/api/build_api.proto, which contains service and method option definitions.
    • And build_api_test.proto which is used only for testing the Build API itself.
  • chromiumos/ generally contains more shareable proto.
    • chromiumos/common.proto contains well shared messages.
    • chromiumos/metrics.proto contains message declarations related to build api event monitoring.
  • test_platform/ contains the APIs of components of the Test Platform recipe.
    • test_platform/request.proto and test_platform/response.proto contain the API of the overall recipe.
  • device/ contains the proto for hardware related configuration.

When making changes to the proto, you must:

  1. Change the proto.
    1. Make your changes.
      • Edit the proto in infra/proto_branched.
      • You can make and submit changes in infra/proto instead, but they will need to be in infra/proto_branched to generate the chromite bindings.
    2. Run
    3. Commit those changes as a single CL.
  2. Update the chromite proto.
    • Run chromite/api/compile_build_api_proto.
    • When no breaking changes are made (should be most changes)
      1. Create a CL with just the generated proto to submit with the raw proto CL.
      2. Submit the proto CLs together.
      3. The implementation may be submitted after the proto CLs.
    • When breaking changes are made (should be very rare)
      1. Make sure you've consulted the Build and CI teams first.
      2. Submit the proto changes along with the implementation.
      3. May be done as a single CL or as a stack of CLs with Cq-Depend.

Use Cq-Depend: to declare the CL dependencies between the infra/proto and chromite changes.

The infra/proto_branched repo is branched and reflects the Build API for the branch in question. The infra/proto repo is unbranched, and is what is used by recipes.


When deprecations are made, be sure to leave a comment that has the ToT milestone to document when the field can be removed, e.g. Deprecated in M95.

gen/ & gen_sdk/

The generated protobuf messages.

Do not edit files in these folders directly!

The proto can be compiled using the compile_build_api_proto script in the api directory. For gen/, the protoc version is locked and fetched from CIPD to ensure compatibility with the client library in third_party/. For gen_sdk/, the proto is compiled with the version of protobuf in the SDK, i.e. the one installed via the protobuf ebuild.


This directory contains the entry point for all of the implemented services. The protobuf service module option (defined in build_api.proto) references the module in this package. The functions in this package should all operate as one would expect a controller to operate in an MVC application - translating the request into the internal representation that's passed along to the relevant service(s), then translates their output to a specified response format.


This directory contains scripts that may not be 100% supported yet. See contrib/ for information about the scripts.