Lightning Trainer for MA OSS#1213
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Imports the LightningTrainer + supporting code from the internal
Michelangelo SDK (uber/ai/michelangelo/sdk/trainer/torch/*) as a
one-time snapshot. Goal is to keep CanvasFlex (internal) and OSS on a
common trainer surface, per discussion in #ml-platform.
New files:
- python/michelangelo/lib/trainer/torch/_numpy_utils.py
Inlined pad_ragged_tensor / sentinel_for_numpy_dtype / infer_dtype +
sentinel constants (ported from shared/utils/numpy_utils).
- python/michelangelo/lib/trainer/torch/data_collate_functions.py
LiteralEvalFloat32Collate + collate helpers used by Ray Data.
- python/michelangelo/lib/trainer/torch/utils.py
Training-memory estimators (transformers and nn.Module).
- python/michelangelo/lib/trainer/torch/pytorch_lightning/schema.py
TransferLearningSpec / IncrementalTrainingSpec dataclasses + enums.
- python/michelangelo/lib/trainer/torch/pytorch_lightning/_private/__init__.py
- python/michelangelo/lib/trainer/torch/pytorch_lightning/_private/callbacks.py
RayTrainReportCallback + RayTrainReportPerNodeCallback.
- python/michelangelo/lib/trainer/torch/pytorch_lightning/_private/util.py
_train_loop_per_worker, strategy/plugin/logger/callbacks resolvers,
Comet logger, init-weights loader, layer-freeze re-application.
Replaced:
- python/michelangelo/lib/trainer/torch/pytorch_lightning/lightning_trainer.py
The previous OSS skeleton (LightningTrainer composing TorchTrainer
with create_run_config/create_scaling_config helpers) is replaced
with the internal LightningTrainer + LightningTrainerWithStateDict
that subclass ray.train.torch.TorchTrainer directly. Callers now
construct ray.train.RunConfig / ScalingConfig themselves.
Stripped from the internal source (no OSS equivalent):
- ArtifactStoreTrainUtils / epoch-resume bookkeeping
- M3 metric counters (MichelangeloStatsLogger, m3_gauge_time, ...)
- CFS fsspec registration (uber.core.fsspec_cfs)
- workflow.framework.exceptions.UserException -> local class
- model_manager reflection_utils.get_module_attr -> inlined
Packaging:
- pyproject.toml: adds comet_ml + deepspeed as optional deps and a
new `trainer` extras group covering the full runtime needed to
import the lib/trainer/torch tree.
Out of scope (separate PR per ownership split):
- sdk/native_transform/ray/* (separate owner)
- Tests under sdk/trainer/torch/**/tests/
A minimal end-to-end smoke test for the LightningTrainer snapshot just
added in the prior commit. Trains a small Neural Collaborative Filtering
model (user + item embeddings -> 2-layer MLP -> sigmoid, MSE loss) on
MovieLens-100k with a single Ray Train worker on CPU.
Files:
- python/examples/movielens/__init__.py
- python/examples/movielens/data.py
Downloads ml-100k from grouplens; falls back to a github mirror if
the canonical host is unreachable. Builds dense user/item indices,
normalizes ratings to [0, 1], splits 80/20 train/val, returns Ray
datasets.
- python/examples/movielens/model.py
NCFLightningModule + create_ncf_model factory used as
LightningTrainerParam.create_model_fn.
- python/examples/movielens/train.py
Wires LightningTrainerParam + LightningTrainer +
ray.train.{RunConfig, ScalingConfig} for a 3-epoch CPU run.
- python/examples/movielens/README.md
Install + run instructions.
Verified locally: ml-100k downloads, model builds (92.4K params), Ray
Train worker spins up, 3 epochs complete in ~5s on CPU, three
checkpoints saved to /tmp/movielens_runs/, final result returned with
checkpoint_path / path / metrics keys matching internal API.
`LightningTrainer` only attaches a `CometLogger` when `comet_param` is provided on `LightningTrainerParam`. Until now the MovieLens demo never set it, so the Comet code path in lib/trainer/torch was untested by the example. Adds `_build_comet_param()` in train.py that constructs a `CometParam` from COMET_API_KEY + COMET_WORKSPACE (required), with optional COMET_PROJECT_NAME / COMET_EXPERIMENT_NAME / COMET_TAGS overrides. When the required vars are unset the function returns None and the trainer falls back to Lightning's default local logger (prior behavior). README documents the env-var contract. Verified locally: - With no env vars set: logs "Comet logging disabled (...)" and completes training using Lightning's default logger.
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Comet was the only tracking backend the demo exposed. Adds MLflow as a second opt-in path. Users pick at most one per run — Comet wins if both env-sets are present, otherwise MLflow if MLFLOW_TRACKING_URI is set, otherwise Lightning's default local logger. `_build_mlflow_logger()` constructs `pytorch_lightning.loggers.MLFlowLogger` directly from env vars (lazy-imported so MLflow isn't required when only Comet or neither is in use). The logger instance is passed through `lightning_trainer_kwargs["logger"]` — `_resolve_logger` already forwards a pre-built Logger instance unchanged, so no trainer changes are needed. Env contract for MLflow: - MLFLOW_TRACKING_URI required (e.g. file:///tmp/mlflow_run, http://...) - MLFLOW_EXPERIMENT_NAME optional, default ncf-movielens100k - MLFLOW_RUN_NAME optional - MLFLOW_TAGS optional, comma-separated key=value pairs README documents both Comet and MLflow paths with copy-paste env-var recipes and notes that Comet wins precedence. Verified locally: - No env vars: "Experiment tracking disabled (no COMET_* or MLFLOW_TRACKING_URI env vars set)" - MLFLOW_TRACKING_URI=file:///tmp/mlflow_movielens: experiment created, run FINISHED, val_loss/train_loss/epoch + all 5 hyperparameters logged, custom tags applied. Verified via mlflow.search_runs() against the file store. mlflow is already in OSS pyproject's `example` extras; no pyproject change.
| pytorch_lightning = { version = "2.2.0", optional = true } | ||
| einops = { version = "0.8.0", optional = true } | ||
| transformers = { version = "4.48.2", optional = true } | ||
| comet_ml = { version = "^3.49.0", optional = true } |
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we don't have comet, can we not use it here?
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Uber uses comet, how would you recommend to have backward compatibility?
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good questions, i think we need to refactor the trainer for different observability. Stamp for now to refactor later
The previous commit (5abd603) added comet_ml + deepspeed as optional deps and a trainer extras group to pyproject.toml but did not refresh the lock. CI's poetry install steps (Coverage, Ruff, python-build, build-and-push) all fail with 'pyproject.toml changed significantly since poetry.lock was last generated'. Regenerated with Poetry 2.2.1 to match CI's pinned version.
🛠 Ruff Check & Format Results
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- Rewrite test_lightning_trainer.py to match the snapshot API:
CometParam, LightningTrainerParam, LightningTrainer init/train,
LightningTrainerWithStateDict strategy detection, and the
_torch_weights_only_disabled env-var context (24 tests, all pass).
- Trainer source cleanups:
- Lazy comet_ml import inside _get_comet_logger() so the package can
be installed without comet_ml.
- Replace all print() calls with module loggers.
- Add full Google-style docstrings and type hints across public API.
- Rename UserException -> UserInputError (ruff N818).
- Snapshot disclosure on top-level package docstring; package
__init__ now re-exports CometParam, LightningTrainer,
LightningTrainerParam, LightningTrainerWithStateDict, and the
schema dataclasses.
- pyproject:
- Split trainer extras into trainer / trainer-comet / trainer-deepspeed
so users pull only what they need.
- Add per-file-ignore for E501 on the snapshot trainer package to
preserve upstream line shape.
- Docs:
- Mention the trainer package and MovieLens example in the top-level
README.
- Drop internal Slack URL and personal owner tags from PR/example docs.
🛠 Ruff Check & Format Results
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Coverage reportClick to see where and how coverage changed
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- examples/movielens: drop Optional[X] for X | None, line-wrap long strings/calls, add docstrings, replace `import nn as F` alias. - pyproject coverage.run: omit lib/trainer/**/_private/* — those modules run inside Ray Train worker processes and are exercised by integration tests, not unit tests; the _private/ convention already marks them as not-for-direct-import. - Add DDP and DeepSpeed path tests for LightningTrainerWithStateDict.update_model_state_dict so the public lightning_trainer.py clears the 90% diff-coverage threshold.
🛠 Ruff Check & Format Results🚨 Lint Issues DetectedShow details🛠 Run |
The per-file-ignore for E501 covers the trainer source but not the tests directory, so trim the two new docstrings under 88 chars and drop the now-unneeded `# noqa: PLC0415` markers.
Closes the test-coverage gaps the OSS review team called out: - tests/.../test_numpy_utils.py — 25 tests for sentinel_for_numpy_dtype (floats/ints/unicode/object/bytes/bool + unsupported raises), infer_dtype recursion, and pad_ragged_tensor across 1-D/2-D rags and float/int sentinel injection. - tests/.../test_data_collate_functions.py — 33 tests for the structural helpers, pad_ragged_lists (1-D / 2-D / 3-D / explicit sentinel), the per-column collate functions, the batch path, and the LiteralEvalFloat32Collate OO wrapper. - tests/.../test_resolve_helpers.py — 38 tests for _resolve_strategy / _resolve_plugins / _resolve_logger / _resolve_callbacks covering string + instance + None inputs, type-check error paths, the default Ray report callback append, and DeepSpeed/FSDP per-node callback routing. DeepSpeed strategy + Ray report callbacks are patched at the resolver-module level so the tests do not need a GPU driver or an active Ray Train session. - examples/movielens/README.md — document the new trainer extras split: trainer / trainer-comet / trainer-deepspeed; add the trainer-comet install hint to the Comet section. 122 trainer tests now pass locally.
PyTorch Lightning trainer + MovieLens demo
Summary
One-time snapshot of the internal Uber Michelangelo
sdk/trainer/torch/pytorch_lightning/package into OSS, plus a runnable MovieLens-100k NCF example that exercises it end-to-end. Per the original Slack thread: snapshot only, no upstream sync.Goal: give external users a thin Ray Train wrapper around PyTorch Lightning that the Michelangelo team uses internally, without the closed-source orchestration layer (
workflow/,model_manager/,artifact/, CFS filesystem, M3 metrics) it normally sits behind.What's in the snapshot
8 files, ~1,400 LOC under
python/michelangelo/lib/trainer/torch/:pytorch_lightning/lightning_trainer.pyLightningTrainer(RayTorchTrainersubclass),LightningTrainerParam,CometParam,LightningTrainerWithStateDictpytorch_lightning/_private/util.py_train_loop_per_worker— the per-Ray-worker training loop. Builds model, applies warm-start, resolves strategy/logger/callbacks, wraps Ray dataset shards, fits viapl.Trainerpytorch_lightning/_private/callbacks.pyRayTrainReportCallback+ per-node variant — bridges Lightning's epoch-end hooks toray.train.report(...)for checkpointingpytorch_lightning/schema.pyTransferLearningSpec,IncrementalTrainingSpec,ModelSpec,TrainingType/LearningModeenumsdata_collate_functions.pyliteral_eval_data_collate_function+ ragged-list padding_numpy_utils.pypad_ragged_tensor+ sentinel-dtype helpers (replaces internaluber.shared.utils.numpy_utils.*)utils.pynn.Module(used by callers to size batches)Execution flow (one Ray worker)
What's intentionally stripped from the internal version
To make the snapshot standalone:
MichelangeloStatsLogger,CANVAS_V2_TRAINING_JOB_RESULT_METRIC,CHECKPOINT_UPLOAD_METRICall removed.register_cfs_into_fsspec— Uber-internal filesystem; OSS users use local / S3 / GCS via standard fsspec.UserException— replaced with a minimal local class.numpy_utils/sentinelpackages — relevant helpers inlined into_numpy_utils.py.Result: zero
uber.*imports in the snapshot.MovieLens-100k demo (
python/examples/movielens/)Smallest viable smoke test for the trainer. Trains a tiny NCF (~92K params) on CPU with one Ray Train worker, 3 epochs, ~5s wall time on the validation run.
data.pymodel.pyNCFLightningModule: user + item embeddings → 2-layer MLP → sigmoid, MSE on[0,1]-normalized ratings.train.pyLightningTrainerParam,LightningTrainer,RunConfig,ScalingConfig. Optionally enables Comet or MLflow tracking via env vars (Comet wins if both set).README.mdWhat the demo exercises end-to-end:
LightningTrainer+LightningTrainerParamfrom the snapshot._train_loop_per_workerfor a non-trivial Lightning fit, includingRayTrainReportCallbackepoch checkpointing.data_collate_fn).RayDDPStrategyeven with a single worker._resolve_loggerComet path (when Comet env vars are set)._resolve_loggerpre-built-pl.Loggerpath (when MLflow env vars are set).pyproject changes
Added two optional dependencies + a
trainerextras group:How to run
First run downloads MovieLens-100k to
/tmp/movielens_data/; checkpoints land in/tmp/movielens_runs/ncf_movielens100k/.Opt-in tracking:
Test plan
python -m examples.movielens.traincompletes in ~5s, 3 epochs, train loss 0.063 → 0.054, val checkpoints written.poetry install --extras "trainer example"resolves cleanly on a fresh checkout.Commits
Snapshot internal Lightning trainer into lib/trainer/torch— the core port + pyproject deps.Add MovieLens-100k NCF example exercising lib/trainer/torch—examples/movielens/{data,model,train,README}.py.examples/movielens: wire optional Comet logging via env vars.examples/movielens: add MLflow as an alternate optional tracker.Out of scope (deliberately)
comet/,custom/,huggingface/).