This page explains how to set up your environment for using ClusterFuzz.


Many features of ClusterFuzz depend on Google Cloud Platform services, but it’s possible to run it locally without these dependencies for testing purposes. See the Architecture page for more details.

Note: Local development is only supported on Linux platform.

Getting the code

Clone the ClusterFuzz repository to your machine by running the following command:

git clone
cd clusterfuzz
git pull

We recommend that you use the latest release version of our code (rather than master branch) for stability reasons. You can check out a particular release using:

git checkout tags/vX.Y.Z

where X.Y.Z is the release version (for example, 1.0.1).

Installing prerequisites

Google Cloud SDK

This step is only necessary on the macOS platform. For Linux user, Google Cloud SDK will be installed later by the script under the “Other dependencies” section.

Install the Google Cloud SDK by following the online instructions.

Python programming language

Download Python 3.7, then install it (see this guide for instructions). If you have Python installed already, you can verify its version by running python --version. You’ll want to install Python 3.7 if your local version is different.

We recommend building using python source from the official repo, as it installs the needed python headers and pip. Otherwise, make sure to explicitly install the specific version of pip for Python 3.7 (e.g. configuring the build with the --with-ensurepip=install flag).

You shouldn’t need pyenv to manage python versions for ClusterFuzz. Instead, set the Python version in the pipenv shell.

Go programming language

Install the Go programming language.

Other dependencies

We provide a script for installing all other development dependencies on Linux and macOS.

Our supported systems include:

  • Ubuntu (16.04, 17.10, 18.04, 18.10, 20.04)
  • Debian 8 (jessie) or later
  • Recent versions of macOS with homebrew (experimental)
  • Note: Only x86 architectures are currently supported

To install the dependencies, run the script:


Log in to your Google Cloud account

Note: This is not necessary if you’re running ClusterFuzz locally.

If you’re planning to set up ClusterFuzz in production, you should authenticate your account with the gcloud tool:

gcloud auth application-default login
gcloud auth login

Loading pipenv

After you run the local/install_deps.bash script, activate pipenv by running the following command:

pipenv shell

This loads all the Python dependencies in the current environment.

You can verify that everything works by running:

python --help

Debugging Common Dependency Issues

If you are having trouble installing dependencies due to Python versioning, try:

$ PYTHON=python3.7 ./local/install_deps.bash

Then run:

$ pipenv shell
$ python --version

The version should be the one you built from source and used to build your dependencies. If it is not, set the pipenv shell version of Python:

$ pipenv install --python 3.7

Assuming your shell has the expected version of Python assigned, the following command should run all appengine tests:

python3.7 py_unittest -t appengine

If, at this point, you see an error to the effect that the config.yaml is missing, sync the pipenv environment’s dependencies with the outer environment’s dependencies:

$ cd src; pipenv sync

Refreshing the Python Environment

You might get stuck in a mode where the python version is the global value, rather than the version you set for the pipenv environment - even when apparently leaving the virtual environment through the exitcommand. If this happens, you may still be in a virtual environment (especially if you see (clusterfuzz)before the command prompt). To escape this virtual environment, use the command deactivate, then run python3.7 -m pipenv shell again to start the pipenv shell with the correct python version.

ClusterFuzz Development Tips

  • Before committing, run python format to clean up formatting
  • Make sure you lint all updated files with python lint. (It’s also possible, though not recommended, to lint individual files with pylint --score=no --jobs=0 <name of directory>.)