Configuring Bazel CI to Test Bazel Rules for Remote Execution


This document is for owners and maintainers of Bazel rule repositories. It describes how to configure the Bazel Continuous Integration (CI) system for your repository to test your rules for compatibility against a remote execution scenario. The instructions in this document apply to projects stored in GitHub repositories.


Before completing the steps in this document, ensure the following:

Setting up the Bazel CI for testing

  1. In your .bazelci/presubmit.yml file, do the following:

    a. Add a config named rbe_ubuntu1604.

    b. In the rbe_ubuntu1604 config, add the build and test targets you want to test against remote execution.

  2. Add thebazel-toolchains GitHub repository to your WORKSPACE file, pinned to the latest release. Also add an rbe_autoconfig target with name buildkite_config:

load("@bazel_toolchains//rules:rbe_repo.bzl", "rbe_autoconfig")

# Creates toolchain configuration for remote execution with BuildKite CI
# for rbe_ubuntu1604.
rbe_autoconfig(name = "buildkite_config")
  1. Send a pull request with your changes to the presubmit.yml file. (See example pull request.)

  2. To view build results, click Details for the RBE (Ubuntu 16.04) pull request check in GItHub, as shown in the figure below. This link becomes available after the pull request has been merged and the CI tests have run. (See example results.)


  3. (Optional) Set the bazel test (RBE (Ubuntu 16.04)) check as a test required to pass before merging in your branch protection rule. The setting is located in GitHub in Settings > Branches > Branch protection rules, as shown in the following figure.


Troubleshooting failed builds and tests

If your build or tests fail, it’s likely due to the following:

  • Required build or test tools are not installed in the default container. Builds using the rbe_ubuntu1604 config run by default inside an rbe-ubuntu16-04 container, which includes tools common to many Bazel builds. However, if your rules require tools not present in the default container, you must create a custom container based on the rbe-ubuntu16-04 container and include those tools as described later in this document.

  • Build or test targets are using rules that are incompatible with remote execution. See Adapting Bazel Rules for Remote Execution for details about compatibility with remote execution.

Using a custom container in the rbe_ubuntu1604 CI config

The rbe-ubuntu16-04 container is publicly available at the following URL:

You can pull it directly from Container Registry or build it from source. The next sections describe both options.

Before you begin, make sure you have installed gcloud, docker, and git. If you are building the container from source, you must also install the latest version of Bazel.

Pulling the rbe-ubuntu16-04 from Container Registry

To pull the Pull the rbe-ubuntu16-04 container from Container Registry, run the following command:

gcloud docker -- pull<sha256-checksum>

Replace <sha256-checksum> with the SHA256 checksum value for the latest container.

Building the rbe-ubuntu16-04 container from source

To build the rbe-ubuntu16-04 container from source, do the following:

  1. Clone the bazel-toolchains repository:

    git clone
  2. Set up toolchain container targets and build the container as explained in Toolchain Containers.

  3. Pull the freshly built container:

    gcloud docker -- pull<project-id>/<custom-container-name>@sha256:<sha256-checksum>

Running the custom container

To run the custom container, do one of the following:

  • If you pulled the container from Container Registry, run the following command:

    docker run -it<sha256-checksum> /bin/bash

    Replace sha256-checksum with the SHA256 checksum value for the latest container.

  • If you built the container from source, run the following command:

    docker run -it<project-id>/<custom-container-name>@sha256:<sha256sum> /bin/bash

Adding resources to the custom container

Use a Dockerfile or rules_docker to add resources or alternate versions of the original resources to the rbe-ubuntu16-04 container. If you are new to Docker, read the following:

For example, the following Dockerfile snippet installs <my_tool_package>:

RUN apt-get update && yes | apt-get install -y <my_tool_package>

Pushing the custom container to Container Registry

Once you have customized the container, build the container image and push it to Container Registry as follows:

  1. Build the container image:

     docker build -t <custom-container-name> .docker tag <custom-container-name><project-id>/<custom-container-name>
  2. Push the container image to Container Registry:

    gcloud docker -- push<project-id>/<custom-container-name>
  3. Navigate to the following URL to verify the container has been pushed:<project-id>/GLOBAL/<custom-container-name>
  4. Take note of the SHA256 checksum of your custom container. You will need to provide it in your build platform definition later in this document.

  5. Configure the container for public access as described in publicly accessible as explained in Serving images publicly.

    For more information, see Pushing and Pulling Images.

Specifying the build platform definition

You must include a Bazel platform configuration in your custom toolchain configuration, which allows Bazel to select a toolchain appropriate to the desired hardware/software platform. To generate automatically a valid platform, you can add to your WORKSPACE an rbe_autoconfig target with name buildkite_config which includes additional attrs to select your custom container. For details on this setup please read the up-to-date documentation for rbe_autoconfig