Building Ray from Source¶
For a majority of Ray users, installing Ray via the latest wheels or pip package is usually enough. However, you may want to build the latest master branch.
If you are only editing Python files, follow instructions for Building Ray (Python Only) to avoid long build times.
Unless otherwise stated, directory and file paths are relative to the project root directory.
RLlib, Tune, Autoscaler, and most Python files do not require you to build and compile Ray. Follow these instructions to develop Ray’s Python files locally without building Ray.
(Optional) To setup an isolated Anaconda environment, see Installing Ray with Anaconda.
Pip install the latest Ray wheels. See Daily Releases (Nightlies) for instructions.
pip install -U https://s3-us-west-2.amazonaws.com/ray-wheels/latest/ray-2.0.0.dev0-cp38-cp38-manylinux2014_x86_64.whl
Fork and clone the project to your machine. Connect your repository to the upstream (main project) ray repository.
git clone https://github.com/[your username]/ray.git cd ray git remote add upstream https://github.com/ray-project/ray.git # Make sure you are up-to-date on master.
3. Replace Python files in the installed package with your local editable copy. We provide a simple script to help you do this:
Running the script will remove the
ray/autoscaler dir (among other directories) bundled with the
ray pip package, and replace them with links to your local code. This way, changing files in your git clone will directly affect 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
Do not run
pip uninstall ray or
pip install -U (for Ray or Ray wheels) if setting up your environment this way. To uninstall or upgrade, you must first
rm -rf the pip-installation site (usually a
site-packages/ray location), then do a pip reinstall (see 1. above), and finally run the above 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>`
If you are only editing Tune/RLlib/Autoscaler files, follow instructions for Building Ray (Python Only) to avoid long build times.
To build Ray, first install the following dependencies.
For Ubuntu, run the following commands:
sudo apt-get update sudo apt-get install -y build-essential curl unzip psmisc pip install cython==0.29.0 pytest
For RHELv8 (Redhat EL 8.0-64 Minimal), run the following commands:
sudo yum groupinstall 'Development Tools' sudo yum install psmisc pip install cython==0.29.0 pytest
Install bazel manually from link: https://docs.bazel.build/versions/main/install-redhat.html
For MacOS, run the following commands:
Assuming you already have brew and bazel installed on your mac and you also have grpc and protobuf installed on your mac consider removing those (grpc and protobuf) for smooth build through commands
brew uninstall grpc,
brew uninstall protobuf. If you have built the source code earlier and it still fails with error as
No such file or directory:, try cleaning previous builds on your host by running commands
brew uninstall binutils and
bazel clean --expunge.
brew update brew install wget pip install cython==0.29.0 pytest
Ray can be built from the repository as follows.
git clone https://github.com/ray-project/ray.git # Install Bazel. ray/ci/travis/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``) # Build the dashboard # (requires Node.js, see https://nodejs.org/ for more information). pushd ray/dashboard/client npm install npm run build popd # Install Ray. cd ray/python pip install -e . --verbose # Add --user if you see a permission denied error.
-e means “editable”, so changes you make to files in the Ray
directory will take effect without reinstalling the package.
if you run
python setup.py install, files will be copied from the Ray directory to a directory of Python packages (
/lib/python3.6/site-packages/ray). This means that changes you make to files in the Ray directory will not have any effect.
The following links were correct during the writing of this section. In case the URLs changed, search at the organizations’ sites.
Microsoft Visual Studio 2019 (or Microsoft Build Tools 2019 - https://visualstudio.microsoft.com/downloads/#build-tools-for-visual-studio-2019)
Miniconda 3 (https://docs.conda.io/en/latest/miniconda.html)
git for Windows, version 2.31.1 or later (https://git-scm.com/download/win)
Enable Developer mode on Windows 10 systems. This is necessary so git can create symlinks.
Open Settings app;
Go to “Update & Security”;
Go to “For Developers” on the left pane;
Turn on “Developer mode”.
Add the following Miniconda subdirectories to PATH. If Miniconda was installed for all users, the following paths are correct. If Miniconda is installed for a single user, adjust the paths accordingly.
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. Bazel 4.2 installation. Go to bazel 4.2 release web page and download
bazel-4.2.1-windows-x86_64.exe. Copy the exe into the directory of your choice.
Define an environment variable BAZEL_PATH to full exe path (example:
set BAZEL_PATH=C:\bazel\bazel.exe). Also add the bazel directory to the
Install cython and pytest:
pip install cython==0.29.0 pytest
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
Currently, Ray is built with optimizations, which can take a long time and
interfere with debugging. To perform fast, debug, or optimized builds, you can
run the following (via
bazel build -c fastbuild //:ray_pkg
This will rebuild Ray with the appropriate options (which may take a while).
If you need to build all targets, you can use
"//:*" instead of
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
If you do so, remember to revert this change, unless you want it to affect all of your development in the future.
dbg instead of
fastbuild generates more debug information,
which can make it easier to debug with a debugger like
If you make changes that require documentation changes, don’t forget to update the documentation!
When you make documentation changes, build them locally to verify they render correctly. Sphinx is used to generate the documentation.
cd doc pip install -r requirements-doc.txt pip install -U -r requirements-rtd.txt # important for reproducing the deployment environment make html
Once done, the docs will be in
doc/_build/html. For example, on Mac
OSX, you can open the docs (assuming you are still in the
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 (
If the dependency already has a Bazel build file in it, you can use
native.local_repository instead, and omit
To test switching back to the original rule, change