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What is CML? Continuous Machine Learning (CML) is an open-source CLI tool for implementing continuous integration & delivery (CI/CD) with a focus on MLOps. Use it to automate development workflows — including machine provisioning, model training and evaluation, comparing ML experiments across project history, and monitoring changing datasets.

CML can help train and evaluate models — and then generate a visual report with results and metrics — automatically on every pull request.

An example report for a neural style transfer model.

CML principles:

  • GitFlow for data science. Use GitLab or GitHub to manage ML experiments, track who trained ML models or modified data and when. Codify data and models with DVC instead of pushing to a Git repo.
  • Auto reports for ML experiments. Auto-generate reports with metrics and plots in each Git pull request. Rigorous engineering practices help your team make informed, data-driven decisions.
  • No additional services. Build your own ML platform using GitLab, Bitbucket, or GitHub. Optionally, use cloud storage as well as either self-hosted or cloud runners (such as AWS EC2 or Azure). No databases, services or complex setup needed.

❓ Need help? Just want to chat about continuous integration for ML? Visit our Discord channel!

⏯ Check out our YouTube video series for hands-on MLOps tutorials using CML!

Table of Contents

  1. Setup (GitLab, GitHub, Bitbucket)
  2. Usage
  3. Getting started (tutorial)
  4. Using CML with DVC
  5. Advanced Setup (Self-hosted, local package)
  6. Example projects


You'll need a GitLab, GitHub, or Bitbucket account to begin. Users may wish to familiarize themselves with Github Actions or GitLab CI/CD. Here, will discuss the GitHub use case.


Please see our docs on CML with GitLab CI/CD and in particular the personal access token requirement.


Please see our docs on CML with Bitbucket Cloud.


The key file in any CML project is .github/workflows/cml.yaml:

name: your-workflow-name
on: [push]
    runs-on: ubuntu-latest
    # optionally use a convenient Ubuntu LTS + DVC + CML image
    # container: docker://
      - uses: actions/[email protected]
      # may need to setup NodeJS & Python3 on e.g. self-hosted
      # - uses: actions/[email protected]
      #   with:
      #     node-version: '16'
      # - uses: actions/[email protected]
      #   with:
      #     python-version: '3.x'
      - uses: iterative/[email protected]
      - name: Train model
        run: |
          # Your ML workflow goes here
          pip install -r requirements.txt
      - name: Write CML report
          REPO_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        run: |
          # Post reports as comments in GitHub PRs
          cat results.txt >>
          cml send-comment


We helpfully provide CML and other useful libraries pre-installed on our custom Docker images. In the above example, uncommenting the field container: docker:// will make the runner pull the CML Docker image. The image already has NodeJS, Python 3, DVC and CML set up on an Ubuntu LTS base for convenience.

CML Functions

CML provides a number of functions to help package the outputs of ML workflows (including numeric data and visualizations about model performance) into a CML report.

Below is a table of CML functions for writing markdown reports and delivering those reports to your CI system.

Function Description Example Inputs
cml runner Launch a runner locally or hosted by a cloud provider See Arguments
cml publish Publicly host an image for displaying in a CML report <path to image> --title <image title> --md
cml send-comment Return CML report as a comment in your GitLab/GitHub workflow <path to report> --head-sha <sha>
cml send-github-check Return CML report as a check in GitHub <path to report> --head-sha <sha>
cml pr Commit the given files to a new branch and create a pull request <path>...
cml tensorboard-dev Return a link to a page --logdir <path to logs> --title <experiment title> --md

CML Reports

The cml send-comment command can be used to post reports. CML reports are written in markdown (GitHub, GitLab, or Bitbucket flavors). That means they can contain images, tables, formatted text, HTML blocks, code snippets and more — really, what you put in a CML report is up to you. Some examples:

🗒 Text Write to your report using whatever method you prefer. For example, copy the contents of a text file containing the results of ML model training:

cat results.txt >>

🖼 Images Display images using the markdown or HTML. Note that if an image is an output of your ML workflow (i.e., it is produced by your workflow), you will need to use the cml publish function to include it a CML report. For example, if graph.png is output by python, run:

cml publish graph.png --md >>

Getting Started

  1. Fork our example project repository.

⚠️ Note that if you are using GitLab, you will need to create a Personal Access Token for this example to work.

⚠️ The following steps can all be done in the GitHub browser interface. However, to follow along with the commands, we recommend cloning your fork to your local workstation:

git clone<your-username>/example_cml
  1. To create a CML workflow, copy the following into a new file, .github/workflows/cml.yaml:
name: model-training
on: [push]
    runs-on: ubuntu-latest
      - uses: actions/[email protected]
      - uses: actions/[email protected]
      - uses: iterative/[email protected]
      - name: Train model
          REPO_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        run: |
          pip install -r requirements.txt

          cat metrics.txt >>
          cml publish plot.png --md >>
          cml send-comment
  1. In your text editor of choice, edit line 16 of to depth = 5.

  2. Commit and push the changes:

git checkout -b experiment
git add . && git commit -m "modify forest depth"
git push origin experiment
  1. In GitHub, open up a pull request to compare the experiment branch to master.

Shortly, you should see a comment from github-actions appear in the pull request with your CML report. This is a result of the cml send-comment function in your workflow.

This is the outline of the CML workflow:

  • you push changes to your GitHub repository,
  • the workflow in your .github/workflows/cml.yaml file gets run, and
  • a report is generated and posted to GitHub.

CML functions let you display relevant results from the workflow — such as model performance metrics and visualizations — in GitHub checks and comments. What kind of workflow you want to run, and want to put in your CML report, is up to you.

Using CML with DVC

In many ML projects, data isn't stored in a Git repository, but needs to be downloaded from external sources. DVC is a common way to bring data to your CML runner. DVC also lets you visualize how metrics differ between commits to make reports like this:

The .github/workflows/cml.yaml file used to create this report is:

name: model-training
on: [push]
    runs-on: ubuntu-latest
    container: docker://
      - uses: actions/[email protected]
      - name: Train model
          REPO_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          AWS_ACCESS_KEY_ID: ${{ secrets.AWS_ACCESS_KEY_ID }}
        run: |
          # Install requirements
          pip install -r requirements.txt

          # Pull data & run-cache from S3 and reproduce pipeline
          dvc pull data --run-cache
          dvc repro

          # Report metrics
          echo "## Metrics" >>
          git fetch --prune
          dvc metrics diff master --show-md >>

          # Publish confusion matrix diff
          echo "## Plots" >>
          echo "### Class confusions" >>
          dvc plots diff --target classes.csv --template confusion -x actual -y predicted --show-vega master > vega.json
          vl2png vega.json -s 1.5 > plot.png
          cml publish --md plot.png >>

          # Publish regularization function diff
          echo "### Effects of regularization" >>
          dvc plots diff --target estimators.csv -x Regularization --show-vega master > vega.json
          vl2png vega.json -s 1.5 > plot.png
          cml publish --md plot.png >>

          cml send-comment

⚠️ If you're using DVC with cloud storage, take note of environment variables for your storage format.

Configuring Cloud Storage Providers

There are many supported could storage providers. Here are a few examples for some of the most frequently used providers:

S3 and S3-compatible storage (Minio, DigitalOcean Spaces, IBM Cloud Object Storage...)
# Github

👉 AWS_SESSION_TOKEN is optional.

👉 AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY can also be used by cml runner to launch EC2 instances. See [Environment Variables].

  OSS_BUCKET: ${{ secrets.OSS_BUCKET }}
Google Storage

⚠️ Normally, GOOGLE_APPLICATION_CREDENTIALS is the path of the json file containing the credentials. However in the action this secret variable is the contents of the file. Copy the json contents and add it as a secret.

Google Drive

⚠️ After configuring your Google Drive credentials you will find a json file at your_project_path/.dvc/tmp/gdrive-user-credentials.json. Copy its contents and add it as a secret variable.


Advanced Setup

Self-hosted (On-premise or Cloud) Runners

GitHub Actions are run on GitHub-hosted runners by default. However, there are many great reasons to use your own runners: to take advantage of GPUs, orchestrate your team's shared computing resources, or train in the cloud.

☝️ Tip! Check out the official GitHub documentation to get started setting up your own self-hosted runner.

Allocating Cloud Compute Resources with CML

When a workflow requires computational resources (such as GPUs), CML can automatically allocate cloud instances using cml runner. You can spin up instances on AWS, Azure, GCP, or Kubernetes.

For example, the following workflow deploys a g4dn.xlarge instance on AWS EC2 and trains a model on the instance. After the job runs, the instance automatically shuts down.

You might notice that this workflow is quite similar to the basic use case above. The only addition is cml runner and a few environment variables for passing your cloud service credentials to the workflow.

Note that cml runner will also automatically restart your jobs (whether from a GitHub Actions 35-day workflow timeout or a AWS EC2 spot instance interruption).

name: Train-in-the-cloud
on: [push]
    runs-on: ubuntu-latest
      - uses: iterative/[email protected]
      - uses: actions/[email protected]
      - name: Deploy runner on EC2
          REPO_TOKEN: ${{ secrets.PERSONAL_ACCESS_TOKEN }}
          AWS_ACCESS_KEY_ID: ${{ secrets.AWS_ACCESS_KEY_ID }}
        run: |
          cml runner \
            --cloud=aws \
            --cloud-region=us-west \
            --cloud-type=g4dn.xlarge \
    needs: deploy-runner
    runs-on: [self-hosted, cml-gpu]
    timeout-minutes: 50400 # 35 days
      image: docker://iterativeai/cml:0-dvc2-base1-gpu
      options: --gpus all
      - uses: actions/[email protected]
      - name: Train model
          REPO_TOKEN: ${{ secrets.PERSONAL_ACCESS_TOKEN }}
        run: |
          pip install -r requirements.txt

          cat metrics.txt >
          cml send-comment

In the workflow above, the deploy-runner step launches an EC2 g4dn.xlarge instance in the us-west region. The model-training step then runs on the newly-launched instance. See [Environment Variables] below for details on the secrets required.

🎉 Note that jobs can use any Docker container! To use functions such as cml send-comment from a job, the only requirement is to have CML installed.

Docker Images

The CML Docker image (docker://iterativeai/cml) comes loaded with Python, CUDA, git, node and other essentials for full-stack data science. Different versions of these essentials are available from different iterativeai/cml image tags. The tag convention is {CML_VER}-dvc{DVC_VER}-base{BASE_VER}{-gpu}:

{BASE_VER} Software included (-gpu)
0 Ubuntu 18.04, Python 2.7 (CUDA 10.1, CuDNN 7)
1 Ubuntu 20.04, Python 3.8 (CUDA 11.2, CuDNN 8)

For example, docker://iterativeai/cml:0-dvc2-base1-gpu, or docker://


The cml runner function accepts the following arguments:

--help                      Show help                                [boolean]
--version                   Show version number                      [boolean]
--log                       Maximum log level
                 [choices: "error", "warn", "info", "debug"] [default: "info"]
--labels                    One or more user-defined labels for this runner
                            (delimited with commas)           [default: "cml"]
--idle-timeout              Seconds to wait for jobs before shutting down. Set
                            to -1 to disable timeout            [default: 300]
--name                      Name displayed in the repository once registered
--no-retry                  Do not restart workflow terminated due to instance
                            disposal or GitHub Actions timeout
                                                    [boolean] [default: false]
--single                    Exit after running a single job
                                                    [boolean] [default: false]
--reuse                     Don't launch a new runner if an existing one has
                            the same name or overlapping labels
                                                    [boolean] [default: false]
--driver                    Platform where the repository is hosted. If not
                            specified, it will be inferred from the
                            environment          [choices: "github", "gitlab"]
--repo                      Repository to be used for registering the runner.
                            If not specified, it will be inferred from the
--token                     Personal access token to register a self-hosted
                            runner on the repository. If not specified, it
                            will be inferred from the environment
                                                            [default: "infer"]
--cloud                     Cloud to deploy the runner
                                [choices: "aws", "azure", "gcp", "kubernetes"]
--cloud-region              Region where the instance is deployed. Choices:
                            [us-east, us-west, eu-west, eu-north]. Also
                            accepts native cloud regions  [default: "us-west"]
--cloud-type                Instance type. Choices: [m, l, xl]. Also supports
                            native types like i.e. t2.micro
--cloud-gpu                 GPU type.
                                    [choices: "nogpu", "k80", "v100", "tesla"]
--cloud-hdd-size            HDD size in GB
--cloud-ssh-private         Custom private RSA SSH key. If not provided an
                            automatically generated throwaway key will be used
                                                                 [default: ""]
--cloud-spot                Request a spot instance                  [boolean]
--cloud-spot-price          Maximum spot instance bidding price in USD.
                            Defaults to the current spot bidding price
                                                               [default: "-1"]
--cloud-startup-script      Run the provided Base64-encoded Linux shell script
                            during the instance initialization   [default: ""]
--cloud-aws-security-group  Specifies the security group in AWS  [default: ""]

Environment Variables

⚠️ You will need to create a personal access token (PAT) with repository read/write access and workflow privileges. In the example workflow, this token is stored as PERSONAL_ACCESS_TOKEN.

ℹ️ If using the --cloud option, you will also need to provide access credentials of your cloud compute resources as secrets. In the above example, AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY (with privileges to create & destroy EC2 instances) are required.

For AWS, the same credentials can also be used for configuring cloud storage.

Proxy support

CML support proxy via known environment variables http_proxy and https_proxy.

On-premise (Local) Runners

This means using on-premise machines as self-hosted runners. The cml runner function is used to set up a local self-hosted runner. On a local machine or on-premise GPU cluster, install CML as a package and then run:

cml runner \
  --repo=$your_project_repository_url \
  --labels="local,runner" \

The machine will listen for workflows from your project repository.

Local Package

In the examples above, CML is installed by the setup-cml action, or comes pre-installed in a custom Docker image pulled by a CI runner. You can also install CML as a package:

npm i -g @dvcorg/cml

You may need to install additional dependencies to use DVC plots and Vega-Lite CLI commands:

sudo apt-get install -y libcairo2-dev libpango1.0-dev libjpeg-dev libgif-dev \
                        librsvg2-dev libfontconfig-dev
npm install -g vega-cli vega-lite

CML and Vega-Lite package installation require the NodeJS package manager (npm) which ships with NodeJS. Installation instructions are below.

Install NodeJS

  • GitHub: This is probably not necessary when using GitHub's default containers or one of CML's Docker containers. Self-hosted runners may need to use a set up action to install NodeJS:
uses: actions/[email protected]
    node-version: '16'
  • GitLab: Requires direct installation.
curl -sL | bash
apt-get update
apt-get install -y nodejs

See Also

These are some example projects using CML.

🔑 needs a PAT.

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