CI/CD#

Commit and PR Workflow#

  • Never commit directly to main — always create a feature branch.

  • Always sign commits: git commit -s -m "message".

  • PR title format: [{areas}] {type}: {description} (e.g., [model] feat: Add Qwen3 model bridge). See @CONTRIBUTING.md for the full PR workflow, area/type labels, and DCO requirements.

How CI Is Triggered#

The workflow is defined in @.github/workflows/cicd-main.yml and is triggered on push — not on pull_request. This is intentional: a bot called copy-pr-bot controls when CI runs.

Mechanism:

  1. When a PR is opened, copy-pr-bot watches for a trust signal.

  2. Trust is established in one of two ways:

    • All commits on the PR branch are GPG-signed by a verified NVIDIA contributor → bot triggers automatically.

    • An NVIDIAN posts /ok to test <commit-sha> as a PR comment → bot triggers manually for that SHA.

  3. Once trusted, copy-pr-bot copies the PR’s code into the remote branch pull-request/<number> and pushes it.

  4. That push fires the workflow’s push trigger on refs/heads/pull-request/<number>, launching CI.

Consequences:

  • CI never runs on untrusted pushes — external contributors always need /ok to test.

  • The running workflow branch is pull-request/<number>, not the author’s feature branch.

  • Pushing a new commit to a PR does not automatically re-trigger CI unless the commit is signed or /ok to test <new-sha> is posted.

  • Concurrent runs for the same PR are cancelled automatically (concurrency group per PR number).

Pipeline Structure#

pre-flight
  └── lint-check
        └── cicd-wait-in-queue       # queues workflows to avoid runner interleaving across PRs
              └── cicd-container-build
                    ├── unit-tests-core
                    ├── unit-tests-diffusion
                    └── functional-tests (L0 always; L1 with needs-more-tests label; L2 on schedule or full-test-suite label)

  • Slack notifications are sent on completion for scheduled and nightly runs.

For functional test tier semantics and job-to-directory mapping, see the testing skill.

CI Failure Investigation#

Locating the PR from a CI Branch#

# Extract PR number from branch name (e.g. pull-request/1234)
PR_NUMBER=$(git rev-parse --abbrev-ref HEAD | grep -oP '(?<=pull-request/)\d+')

gh pr view "$PR_NUMBER" --repo NVIDIA-NeMo/Megatron-Bridge
gh pr diff "$PR_NUMBER" --repo NVIDIA-NeMo/Megatron-Bridge --name-only
gh pr checks "$PR_NUMBER" --repo NVIDIA-NeMo/Megatron-Bridge

Investigating a Failing Job#

  1. Get the PR number from the branch name (see above).

  2. Review the changeset:

    gh pr diff "$PR_NUMBER" --repo NVIDIA-NeMo/Megatron-Bridge

  3. Identify the failing job from gh pr checks output.

  4. Fetch job logs:

    gh run list --repo NVIDIA-NeMo/Megatron-Bridge --branch "pull-request/$PR_NUMBER"
gh run view <run_id> --repo NVIDIA-NeMo/Megatron-Bridge --log-failed > run.log

  5. Scan logs in chunks — log files can exceed 10,000 lines, never load them whole:

    wc -l run.log
tail -200 run.log          # start from the end
sed -n '1,200p' run.log    # or scan forward in 200-line chunks

  6. Cross-reference the changeset against the failing step.

Common Failure Patterns#

Symptom

Likely Cause

Action

CI never started on a PR

Commits not GPG-signed and no /ok to test comment

Post /ok to test <full-sha> on the PR

Lint job fails

ruff or pre-commit violation

Run ruff check --fix + ruff format locally

Container build fails

Dependency conflict or stale uv.lock

Re-run uv lock inside Docker and commit updated lock

Unit tests fail

Code regression or missing import

Run failing test locally; check the PR diff

Functional test (L0) fails

Integration breakage

Check GPU runner logs; reproduce with L0_Launch_*.sh

cicd-wait-in-queue running long

Many PRs queued; automation serializes runners to avoid interleaving

Wait; or check queue depth in the Actions tab

MCore submodule mismatch

Pinned commit out of sync

Update 3rdparty/Megatron-LM submodule and re-lock

Stale checkpoint auto-resume

nemo_experiments/ from a previous run exists

rm -rf nemo_experiments before starting fresh

Port collision on Slurm (EADDRINUSE)

ntasks-per-node=8 with torchrun

Drop torchrun; use ntasks-per-node=8 with uv run python script.py