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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
    it.

(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:

#!/bin/sh

NAME=$(git config user.name)
EMAIL=$(git config user.email)

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

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

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 request to add the contributor to the project README.

Common contribution types include: doc, code, bug, and ideas. See the full list at allcontributors.org/docs/en/emoji-key

Development environment#

We use the "scripts to rule them all" philosophy to manage common tasks across the project. These are mostly backed by a Makefile that contains the implementation.

You'll need the following dependencies installed to build Cog locally: - mise: Manages Go and uv (which in turn manages Python) - Docker or OrbStack

Set up your development environment:

script/setup

Once you have Go installed you can install the cog binary by running:

make install PREFIX=$(go env GOPATH)

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

To run ALL the tests:

script/test-all

To run per-language tests (forwards arguments to test runner):

script/test-python --no-cov python/tests/cog/test_files.py -k test_put_file_to_signed_endpoint_with_location

script/test-go ./pkg/config

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

script/format

To run code linting across all files:

script/lint

For more information check the Makefile targets for more specific commands.

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.
  • integration-tests/ - Go-based integration tests using testscript.
  • tools/compatgen/ - Tool for generating CUDA/PyTorch/TensorFlow compatibility matrices.

For deeper architectural understanding, see the architecture documentation.

Updating compatibility matrices#

The CUDA base images and framework compatibility matrices in pkg/config/ are checked into source control and only need to be regenerated when adding support for new versions of CUDA, PyTorch, or TensorFlow.

To regenerate the compatibility matrices, run:

# Regenerate all matrices
script/generate-compat

# Or regenerate specific matrices
script/generate-compat cuda
script/generate-compat torch
script/generate-compat tensorflow

The generated files are: - pkg/config/cuda_base_images.json - Available NVIDIA CUDA base images - pkg/config/torch_compatibility_matrix.json - PyTorch/CUDA/Python compatibility - pkg/config/tf_compatibility_matrix.json - TensorFlow/CUDA/Python compatibility

Concepts#

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:

script/test # see also: make test

To run just the Go unit tests:

script/test-go # see also: make test-go

To run just the Python tests:

script/test-python # see also: make test-python

[!INFO] This runs the Python test suite using the default Python version. To run a more comprehensive test across multiple Python versions, use make test-python.

Integration Tests#

Integration tests are in integration-tests/ using testscript. Each test is a self-contained .txtar file in integration-tests/tests/, with some specialized tests as Go test functions in subpackages.

# Run all integration tests
make test-integration

# Run fast tests only (skip slow GPU/framework tests)
cd integration-tests && go test -short -v

# Run a specific test
cd integration-tests && go test -v -run TestIntegration/string_predictor

# Run with a custom cog binary
COG_BINARY=/path/to/cog make test-integration

Writing Integration Tests#

When adding new functionality, add integration tests in integration-tests/tests/. They are: - Self-contained (embedded fixtures in .txtar files) - Faster to run (parallel execution with automatic cleanup) - Easier to read and write (simple command script format)

Example test structure:

# Test string predictor
cog build -t $TEST_IMAGE
cog predict $TEST_IMAGE -i s=world
stdout 'hello world'

-- cog.yaml --
build:
  python_version: "3.12"
predict: "predict.py:Predictor"

-- predict.py --
from cog import BasePredictor

class Predictor(BasePredictor):
    def predict(self, s: str) -> str:
        return "hello " + s

For testing cog serve, use cog serve and the curl command:

cog build -t $TEST_IMAGE
cog serve
curl POST /predictions '{"input":{"s":"test"}}'
stdout '"output":"hello test"'

Advanced Test Commands#

For tests that require subprocess initialization or async operations, use retry-curl:

retry-curl - HTTP request with automatic retries:

# Make HTTP request with retry logic (useful for subprocess initialization delays)
# retry-curl [method] [path] [body] [max-attempts] [retry-delay]
retry-curl POST /predictions '{"input":{"s":"test"}}' 30 1s
stdout '"output":"hello test"'

Example: Testing predictor with subprocess in setup

cog build -t $TEST_IMAGE
cog serve

# Use generous retries since setup spawns a background process
retry-curl POST /predictions '{"input":{"s":"test"}}' 30 1s
stdout '"output":"hello test"'

-- predict.py --
class Predictor(BasePredictor):
    def setup(self):
        self.process = subprocess.Popen(["./background.sh"])

    def predict(self, s: str) -> str:
        return "hello " + s

Test Conditions#

Use conditions to control when tests run based on environment:

[short] - Skip slow tests in short mode:

[short] skip 'requires GPU or long build time'

cog build -t $TEST_IMAGE
# ... rest of test

Run with go test -short to skip these tests.

[linux] / [!linux] - Platform-specific tests:

[!linux] skip 'requires Linux'

# Linux-specific test
cog build -t $TEST_IMAGE

[amd64] / [!amd64] - Architecture-specific tests:

[!amd64] skip 'requires amd64 architecture'

# amd64-specific test
cog build -t $TEST_IMAGE

[linux_amd64] - Combined platform and architecture:

[!linux_amd64] skip 'requires Linux on amd64'

# Test that requires both Linux and amd64
cog build -t $TEST_IMAGE

Combining conditions:

Conditions can be negated with !. Examples: - [short] - True when go test -short is used (skip this test in short mode) - [!short] - True when NOT running with -short flag (only run this in full test mode) - [!linux] - True when NOT on Linux - [linux_amd64] - True when on Linux AND amd64

See existing tests in integration-tests/tests/, especially setup_subprocess_*.txtar, for more examples.

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 annotated git tag.

Choose a version number#

Deciding what the annotated git tag should be requires some interpretation. Cog generally follows SemVer 2.0.0, and since the major version is 0, the rules get a bit more loose. Broadly speaking, the rules for when to increment the patch version still hold, but backward-incompatible changes will not require incrementing the major version. In this way, the minor version may be incremented whether the changes are additive or subtractive. This all changes once the major version is incremented to 1.

Set up GPG signing (macOS)#

Before creating a signed tag, you'll need to set up GPG signing. On macOS, install GPG using Homebrew:

brew install gnupg

Generate a GPG key for signing:

gpg --quick-generate-key "Your Name <[email protected]>" ed25519 default 0

Configure Git to use your GPG key:

# Get your key ID
gpg --list-secret-keys --keyid-format=long

This will show output like: 

sec   ed25519/ABC123DEF456 2024-01-15 [SC]
      ABC123DEF4567890ABCDEF1234567890ABCDEF12
uid                 [ultimate] Your Name <[email protected]>

The key ID is the part after ed25519/ (in this example, ABC123DEF456).

# Configure Git (replace YOUR_KEY_ID with your actual key ID)
git config --global user.signingkey YOUR_KEY_ID
git config --global commit.gpgsign true

Create a prerelease (optional)#

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

Create a release#

Run these commands to publish a new release v0.13.12 referencing commit fabdadbead:

git checkout main
git fetch --all --tags
git tag --sign --annotate --message 'Release v0.13.12' v0.13.12 fabdadbead
git push origin v0.13.12

Then visit github.com/replicate/cog/actions to monitor the release process.

Get team approval for the PyPI package#

The release workflow will halt until another member of the team approves the release.

Ping someone on the team to review and approve the release.

Convert your git tag to a GitHub release#

Once the release is published, convert your git tag to a proper GitHub release:

  1. Visit github.com/replicate/cog/tags
  2. Click on your tag
  3. Click "Create release from tag"
  4. Add release notes and publish the release

Troubleshooting#

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.