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Contributing guide#

Making a contribution#

Signing your work#

Each commit you contribute to Cog must be signed off (not to be confused with signing). It certifies that you wrote the patch, or have the right to contribute it. It is called the Developer Certificate of Origin and was originally developed for the Linux kernel.

If you can certify the following:

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I
    have the right to submit it under the open source license
    indicated in the file; or

(b) The contribution is based upon previous work that, to the best
    of my knowledge, is covered under an appropriate open source
    license and I have the right under that license to submit that
    work with modifications, whether created in whole or in part
    by me, under the same open source license (unless I am
    permitted to submit under a different license), as indicated
    in the file; or

(c) The contribution was provided directly to me by some other
    person who certified (a), (b) or (c) and I have not modified

(d) I understand and agree that this project and the contribution
    are public and that a record of the contribution (including all
    personal information I submit with it, including my sign-off) is
    maintained indefinitely and may be redistributed consistent with
    this project or the open source license(s) involved.

Then add this line to each of your Git commit messages, with your name and email:

Signed-off-by: Sam Smith <[email protected]>

How to sign off your commits#

If you're using the git CLI, you can sign a commit by passing the -s option: git commit -s -m "Reticulate splines"

You can also create a git hook which will sign off all your commits automatically. Using hooks also allows you to sign off commits when using non-command-line tools like GitHub Desktop or VS Code.

First, create the hook file and make it executable:

cd your/checkout/of/cog
touch .git/hooks/prepare-commit-msg
chmod +x .git/hooks/prepare-commit-msg

Then paste the following into the file:


NAME=$(git config
EMAIL=$(git config

if [ -z "$NAME" ]; then
    echo "empty git config"
    exit 1

if [ -z "$EMAIL" ]; then
    echo "empty git config"
    exit 1

git interpret-trailers --if-exists doNothing --trailer \
    "Signed-off-by: $NAME <$EMAIL>" \
    --in-place "$1"

Acknowledging contributions#

We welcome contributions from everyone, and consider all forms of contribution equally valuable. This includes code, bug reports, feature requests, and documentation. We use All Contributors to maintain a list of all the people who have contributed to Cog.

To acknowledge a contribution, add a comment to an issue or pull request in the following format:

@allcontributors please add @username for doc,code,ideas

A bot will automatically open a pull requests to add the contributor to the project README.

Common contribution types include: doc, code, bug, and ideas. See the full list at

Development environment#

You'll need to install Go 1.21. If you're using a newer Mac with an M1 chip, be sure to download the darwin-arm64 installer package. Alternatively you can run brew install go which will automatically detect and use the appropriate installer for your system architecture.

Install the Python dependencies:

python -m pip install '.[dev]'

Once you have Go installed, run:

make install PREFIX=$(go env GOPATH)

This installs the cog binary to $GOPATH/bin/cog.

To run the tests:

make test

The project is formatted by goimports. To format the source code, run:

make fmt

If you encounter any errors, see the troubleshooting section below?

Project structure#

As much as possible, this is attempting to follow the Standard Go Project Layout.

  • cmd/ - The root cog command.
  • pkg/cli/ - CLI commands.
  • pkg/config - Everything cog.yaml related.
  • pkg/docker/ - Low-level interface for Docker commands.
  • pkg/dockerfile/ - Creates Dockerfiles.
  • pkg/image/ - Creates and manipulates Cog Docker images.
  • pkg/predict/ - Runs predictions on models.
  • pkg/util/ - Various packages that aren't part of Cog. They could reasonably be separate re-usable projects.
  • python/ - The Cog Python library.
  • test-integration/ - High-level integration tests for Cog.


There are a few concepts used throughout Cog that might be helpful to understand.

  • Config: The cog.yaml file.
  • Image: Represents a built Docker image that serves the Cog API, containing a model.
  • Input: Input from a prediction, as key/value JSON object.
  • Model: A user's machine learning model, consisting of code and weights.
  • Output: Output from a prediction, as arbitrarily complex JSON object.
  • Prediction: A single run of the model, that takes input and produces output.
  • Predictor: Defines how Cog runs predictions on a model.

Running tests#

To run the entire test suite:

make test

To run just the Golang tests:

make test-go

To run just the Python tests:

make test-python

To stand up a server for one of the integration tests:

make install
pip install -r requirements-dev.txt
make test
cd test-integration/test_integration/fixtures/file-project
cog build
docker run -p 5001:5000 --init --platform=linux/amd64 cog-file-project

Then visit localhost:5001 in your browser.

Running the docs server#

To run the docs website server locally:

make run-docs-server

Publishing a release#

This project has a GitHub Actions workflow that uses goreleaser to facilitate the process of publishing new releases. The release process is triggered by manually creating and pushing a new git tag.

To publish a new release, run the following in your local checkout of cog:

git checkout main
git fetch --all --tags
git tag v0.0.11
git push --tags

Then visit to monitor the release process.

Publishing a prerelease#

Prereleases are a useful way to give testers a way to try out new versions of Cog without affecting the documented latest download URL which people normally use to install Cog.

To publish a prerelease version, append a SemVer prerelease identifer like -alpha or -beta to the git tag name. Goreleaser will detect this and mark it as a prerelease in GitHub Releases.

git checkout some-prerelease-branch
git fetch --all --tags
git tag -a v0.1.0-alpha -m "Prerelease v0.1.0"
git push --tags


cog command not found#

The compiled cog binary will be installed in $GOPATH/bin/cog, e.g. ~/go/bin/cog. Make sure that Golang's bin directory is present on your system PATH by adding it to your shell config (.bashrc, .zshrc, etc):

export PATH=~/go/bin:$PATH

Still having trouble? Please open an issue on GitHub.