Building Ray from source#

To contribute to the Ray repository, follow the instructions below to build from the latest master branch.

Depending on your goal, you may not need all sections on this page:

  • Python-only development (fast loop, no C++) - edit Python files without compiling C++ (see Building Ray (Python only)).

  • Build Ray with C++ - choose one:

    • Distributable manylinux wheel - uses a manylinux build container to produce a .whl file for installation on a cluster, for testing the packaged artifact locally, or for sharing (see Building distributable manylinux wheels).

    • Ray image - build a nightly-style rayproject/ray or rayproject/ray-llm image (see Building Ray images).

    • Full source build (editable install) - make C++ changes or build all of Ray (see Full source build).

Setup#

Fork the Ray repository#

Forking an open source repository is a best practice when looking to contribute, as it allows you to make and test changes without affecting the original project, ensuring a clean and organized collaboration process. You can propose changes to the main project by submitting a pull request to the main project’s repository.

  1. Navigate to the Ray GitHub repository.

  2. Follow these GitHub instructions, and do the following:

    1. Fork the repo using your preferred method.

    2. Clone to your local machine.

    3. Connect your repo to the upstream (main project) Ray repo to sync changes.

Prepare a Python virtual environment#

Skip this section if you’re building a distributable wheel or a Ray image.

Create a virtual environment to prevent version conflicts and to develop with an isolated, project-specific Python setup.

Set up a conda environment named myenv:

conda create -c conda-forge python=3.10 -n myenv

Activate your virtual environment to tell the shell/terminal to use this particular Python:

conda activate myenv

You need to activate the virtual environment every time you start a new shell/terminal to work on Ray.

Use Python’s integrated venv module to create a virtual environment called myenv in the current directory:

python -m venv myenv

This contains a directory with all the packages used by the local Python of your project. You only need to do this step once.

Activate your virtual environment to tell the shell/terminal to use this particular Python:

source myenv/bin/activate

You need to activate the virtual environment every time you start a new shell/terminal to work on Ray.

Creating a new virtual environment can come with older versions of pip and wheel. To avoid problems when you install packages, use the module pip to install the latest version of pip (itself) and wheel:

python -m pip install --upgrade pip wheel

Building Ray (Python only)#

Note

Unless otherwise stated, directory and file paths are relative to the project root directory.

RLlib, Tune, Autoscaler, and most Python files don’t require you to build and compile Ray. Follow these instructions to develop Ray’s Python files locally without building Ray.

  1. Make sure you have a clone of Ray’s git repository (see Fork the Ray repository).

  2. Make sure you activate the Python (virtual) environment (see Prepare a Python virtual environment).

  3. Pip install the latest Ray wheels. See Daily Releases (Nightlies) for instructions.

# For example, for Python 3.10:
pip install -U https://s3-us-west-2.amazonaws.com/ray-wheels/latest/ray-3.0.0.dev0-cp310-cp310-manylinux2014_x86_64.whl

  1. Replace Python files in the installed package with your local editable copy. Use the script python python/ray/setup-dev.py to do this. The script removes the ray/tune, ray/rllib, ray/autoscaler directories (among others) bundled with the ray pip package, replacing them with links to your local code. This way, changing files in your git clone directly affects the behavior of your installed Ray.

# This replaces `<package path>/site-packages/ray/<package>`
# with your local `ray/python/ray/<package>`.
python python/ray/setup-dev.py

You can optionally skip creating symbolic links for specific directories:

# This links all folders except "_private" and "dashboard" without user prompt.
python python/ray/setup-dev.py -y --skip _private dashboard

Warning

Don’t run pip uninstall ray or pip install -U (for Ray or Ray wheels) if setting up your environment this way. To uninstall or upgrade, first rm -rf the pip-installation site (usually a directory at the site-packages/ray location), then do a pip reinstall (see the command above), and finally run the setup-dev.py script again.

# To uninstall, delete the symlinks first.
rm -rf <package path>/site-packages/ray # Path will be in the output of `setup-dev.py`.
pip uninstall ray # or `pip install -U <wheel>`

Building distributable manylinux wheels#

Setup

Before you begin, make sure you have:

To build a distributable manylinux .whl, use the build-wheel.sh script at the repository root.

# Build a manylinux wheel for the host architecture:
./build-wheel.sh 3.12

# Specify a custom output directory:
./build-wheel.sh 3.12 ./dist

Run ./build-wheel.sh without arguments to see supported Python versions and options. Regardless of host OS, the output is always a manylinux wheel (the same format used by CI and PyPI). Supported build hosts are Linux x86_64, Linux aarch64, and macOS ARM64.

See python/README-building-wheels.md for additional options, including building manylinux wheels directly with Docker.

Building Ray images#

Setup

Before you begin, make sure you have:

To build a Ray image, use the build-image.sh script at the repository root.

# Build the default Ray image:
./build-image.sh ray

# Build with a specific Python version:
./build-image.sh ray -p 3.12

# Build a GPU image:
./build-image.sh ray --platform cu12.8.1-cudnn

Run ./build-image.sh --help to see available image types, Python versions, and platform variants.

Full source build#

Tip

If you already followed the instructions in Building Ray (Python only) and want to switch to the Full build, you need to first uninstall Ray (see uninstallation steps).

Preparing to build Ray on Linux#

Tip

If you’re only editing Tune/RLlib/Autoscaler files, follow Building Ray (Python only) instead to avoid long build times.

To build Ray on Ubuntu, run the following commands:

sudo apt-get update
sudo apt-get install -y build-essential curl clang-12 pkg-config psmisc unzip

# Install Bazelisk.
ci/env/install-bazel.sh

# Install node version manager and node 14
curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.1/install.sh | bash
nvm install 14
nvm use 14

The install-bazel.sh script installs bazelisk. Note that bazel is installed at $HOME/bin/bazel; make sure it’s on your PATH. If you prefer to use bazel directly, only version 6.5.0 is currently supported.

For RHELv8 (Redhat EL 8.0-64 Minimal), run the following commands:

sudo yum groupinstall 'Development Tools'
sudo yum install psmisc

In RedHat, install Bazel manually from this link: https://bazel.build/versions/6.5.0/install/redhat

Preparing to build Ray on macOS#

If you have grpc or protobuf installed, remove them first for a smooth build: brew uninstall grpc, brew uninstall protobuf. If the build fails with No such file or directory errors, clean previous builds with brew uninstall binutils and bazel clean --expunge.

To build Ray on macOS, first install these dependencies:

brew update
brew install wget

# Install Bazel.
ci/env/install-bazel.sh

Building Ray on Linux & macOS (full)#

Make sure you have a local clone of Ray’s git repository (see Fork the Ray repository). You also need to install NodeJS to build the dashboard.

Enter into the project directory, for example:

cd ray

Build the dashboard. From inside your local Ray project directory, enter the dashboard client directory:

cd python/ray/dashboard/client

Install the dependencies and build the dashboard:

npm ci
npm run build

Move back to the top-level Ray directory:

cd -

Now let’s build Ray for Python. Make sure you activate any Python virtual (or conda) environment (see Prepare a Python virtual environment).

Enter into the python/ directory inside of the Ray project directory and install the project with pip:

# Install Ray.
cd python/
# Install required dependencies.
pip install -r requirements.txt
# You may need to set the following two env vars if you have a macOS ARM64(M1) platform.
# See https://github.com/grpc/grpc/issues/25082 for more details.
# export GRPC_PYTHON_BUILD_SYSTEM_OPENSSL=1
# export GRPC_PYTHON_BUILD_SYSTEM_ZLIB=1
pip install -e . --verbose  # Add --user if you see a permission denied error.

The -e means “editable”, so changes you make to files in the Ray directory take effect without reinstalling the package.

Warning

Don’t run python setup.py install — Python copies files from the Ray directory to a packages directory (/lib/python3.6/site-packages/ray), so changes you make to files in the Ray directory won’t have any effect.

If your machine runs out of memory during the build, add the following to ~/.bazelrc:

build --local_ram_resources=HOST_RAM*.5 --local_cpu_resources=4

The build --disk_cache=~/bazel-cache option can also speed up repeated builds.

If you run into an error building protobuf, switching from miniforge to anaconda might help.

Building Ray on Windows (full)#

Requirements

The following links were accurate at the time of writing. If a URL has changed, search the organization’s site.

You can also use the included script to install Bazel:

# Install Bazel.
ray/ci/env/install-bazel.sh
# (Windows users: please manually place Bazel in your PATH, and point
# BAZEL_SH to MSYS2's Bash: ``set BAZEL_SH=C:\Program Files\Git\bin\bash.exe``)

Steps

  1. Enable Developer mode on Windows 10 systems. This is necessary so git can create symlinks.

    1. Open Settings app;

    2. Go to “Update & Security”;

    3. Go to “For Developers” on the left pane;

    4. Turn on “Developer mode”.

  2. Add the following Miniforge subdirectories to PATH. If Miniforge was installed for all users, the following paths are correct. If Miniforge is installed for a single user, adjust the paths accordingly.

    • C:\ProgramData\miniforge3

    • C:\ProgramData\miniforge3\Scripts

    • C:\ProgramData\miniforge3\Library\bin

  3. Define an environment variable BAZEL_SH to point to bash.exe. If git for Windows was installed for all users, bash’s path should be C:\Program Files\Git\bin\bash.exe. If git was installed for a single user, adjust the path accordingly.

4. Install Bazel 6.5.0. Go to the Bazel 6.5.0 release page and download bazel-6.5.0-windows-x86_64.exe. Copy the exe into the directory of your choice. Define an environment variable BAZEL_PATH to the full exe path (example: set BAZEL_PATH=C:\bazel\bazel.exe). Also add the Bazel directory to PATH (example: set PATH=%PATH%;C:\bazel)

  1. Download ray source code and build it.

# cd to the directory under which the ray source tree will be downloaded.
git clone -c core.symlinks=true https://github.com/ray-project/ray.git
cd ray\python
pip install -e . --verbose

Advanced build options#

Environment variables that influence builds#

You can tweak the build with the following environment variables (when running pip install -e . or python setup.py install):

  • RAY_BUILD_CORE: If set and equal to 1, Ray builds the core parts. Defaults to 1.

  • RAY_INSTALL_JAVA: If set and equal to 1, Ray runs extra build steps to build Java portions of the codebase

  • RAY_INSTALL_CPP: If set and equal to 1, Ray installs ray-cpp

  • RAY_BUILD_REDIS: If set and equal to 1, Ray builds or fetches Redis binaries. These binaries are only used for testing. Defaults to 1.

  • RAY_DISABLE_EXTRA_CPP: If set and equal to 1, a regular (non-cpp) build won’t provide some cpp interfaces

  • SKIP_BAZEL_BUILD: If set and equal to 1, Ray skips all Bazel build steps

  • SKIP_THIRDPARTY_INSTALL_CONDA_FORGE: If set, setup skips installation of third-party packages required for build. This is active on conda-forge where pip isn’t used to create a build environment.

  • RAY_DEBUG_BUILD: Can be set to debug, asan, or tsan. Ray ignores any other value

  • BAZEL_ARGS: If set, pass a space-separated set of arguments to Bazel. This can be useful for restricting resource usage during builds, for example. See https://bazel.build/docs/user-manual for more information about valid arguments.

  • IS_AUTOMATED_BUILD: Used in conda-forge CI to tweak the build for the managed CI machines

  • SRC_DIR: Can be set to the root of the source checkout, defaults to None which is cwd()

  • BAZEL_SH: used on Windows to find a bash.exe, see below

  • BAZEL_PATH: used on Windows to find bazel.exe, see below

  • MINGW_DIR: used on Windows to find bazel.exe if not found in BAZEL_PATH

Fast, debug, and optimized builds#

By default, Ray builds with optimizations, which can take a long time and interfere with debugging. To perform fast, debug, or optimized builds, run the following (via -c fastbuild/dbg/opt, respectively):

bazel run -c fastbuild //:gen_ray_pkg

This rebuilds Ray with the appropriate options (which might take a while). If you need to build all targets, use bazel build //:all instead of bazel run //:gen_ray_pkg.

To make this change permanent, you can add an option such as the following line to your user-level ~/.bazelrc file (not to be confused with the workspace-level .bazelrc file):

build --compilation_mode=fastbuild

If you do so, remember to revert this change, unless you want it to affect all of your development in the future.

Using dbg instead of fastbuild generates more debug information, which can make it easier to debug with a debugger like gdb.

Using a local repository for dependencies#

If you’d like to build Ray with custom dependencies (for example, with a different version of Cython), you can modify your .bzl file as follows:

http_archive(
  name = "cython",
  ...,
) if False else native.new_local_repository(
  name = "cython",
  build_file = "bazel/BUILD.cython",
  path = "../cython",
)

This replaces the existing http_archive rule with one that references a sibling of your Ray directory (named cython) using the build file provided in the Ray repository (bazel/BUILD.cython). If the dependency already has a Bazel build file in it, you can use native.local_repository instead, and omit build_file.

To test switching back to the original rule, change False to True.

Development tooling#

Installing additional dependencies for development#

Install dependencies for the linter (pre-commit):

pip install -c python/requirements_compiled.txt pre-commit
pre-commit install

Install dependencies for running Ray unit tests under python/ray/tests:

pip install -c python/requirements_compiled.txt -r python/requirements/test-requirements.txt

Requirement files for running Ray Data / ML library tests are under python/requirements/.

Pre-commit hooks#

Ray uses pre-commit hooks with the pre-commit python package. The .pre-commit-config.yaml file configures all the linting and formatting checks. To start using pre-commit:

pip install pre-commit
pre-commit install

This installs pre-commit into the current environment and enables pre-commit checks every time you commit new code changes with git. To temporarily skip pre-commit checks, use the -n or --no-verify flag when committing:

git commit -n

If you encounter any issues with pre-commit, please report an issue here.

Building the docs#

To learn more about building the docs refer to Contributing to the Ray Documentation.

Troubleshooting#

If importing Ray (python3 -c "import ray") in your development clone results in this error:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File ".../ray/python/ray/__init__.py", line 63, in <module>
    import ray._raylet  # noqa: E402
  File "python/ray/_raylet.pyx", line 98, in init ray._raylet
    import ray.memory_monitor as memory_monitor
  File ".../ray/python/ray/memory_monitor.py", line 9, in <module>
    import psutil  # noqa E402
  File ".../ray/python/ray/thirdparty_files/psutil/__init__.py", line 159, in <module>
    from . import _psosx as _psplatform
  File ".../ray/python/ray/thirdparty_files/psutil/_psosx.py", line 15, in <module>
    from . import _psutil_osx as cext
ImportError: cannot import name '_psutil_osx' from partially initialized module 'psutil' (most likely due to a circular import) (.../ray/python/ray/thirdparty_files/psutil/__init__.py)

Run the following commands:

rm -rf python/ray/thirdparty_files/
python3 -m pip install psutil