Overhaul cudf-polars docs for new streaming multi-GPU engines

dependencies.yaml

@@ -161,6 +161,7 @@ files:
       - depends_on_pylibcudf
       - depends_on_libcudf
       - depends_on_cudf_polars
+      - depends_on_ray
       - docs
       - py_version
   py_build_cudf:

docs/cudf/source/conf.py

@@ -625,12 +625,30 @@ def on_missing_reference(app, env, node, contnode):
     ("py:class", "Axis"),
     ("py:class", "ArrowLike"),
     ("py:class", "ExecutorType"),
+    # cudf-polars: bare rapidsmpf type names appear in autodoc'd signatures
+    # because they are imported under ``if TYPE_CHECKING:`` and rendered as
+    # unqualified strings in type annotations. The ``rapidsmpf.*`` regex below
+    # only matches fully qualified targets, so the bare leaf names are listed
+    # explicitly here.
+    ("py:class", "Statistics"),
+    ("py:class", "Communicator"),
+    ("py:class", "Options"),
+    # polars aliases that don't match the public intersphinx targets.
+    ("py:class", "pl.DataFrame"),
+    ("py:class", "polars.LazyFrame"),
+    ("py:class", "polars.DataFrame"),
+    ("py:class", "polars.dataframe.frame.DataFrame"),
 ]
 # Temporarily disable nitpick warnings for pandas: https://github.com/pandas-dev/pandas/issues/64584
 nitpick_ignore_regex = [
     ("py:.*", "pandas.*"),
     ("py:.*", "pd.*"),
     ("ref.*", ".*pandas.*"),
+    # External libs without configured intersphinx inventories.
+    ("py:.*", r"rapidsmpf(\..*)?"),
+    ("py:.*", r"ray(\..*)?"),
+    ("py:.*", r"distributed(\..*)?"),
+    ("py:.*", r"dask_cuda(\..*)?"),
 ]
 
 

docs/cudf/source/cudf_polars/api.md

@@ -1,17 +1,73 @@
 (cudf-polars-api)=
-# API
+# API Reference
 
-For the most part, the public API of `cudf-polars` is the polars API.
+For the most part, the public API of `cudf-polars` is the Polars API itself. This page
+documents the additional classes and functions that `cudf-polars` exposes for the streaming
+multi-GPU engines.
+
+## Streaming engines
+
+```{eval-rst}
+.. autoclass:: cudf_polars.engine.ray.RayEngine
+   :members: from_options, gather_cluster_info, gather_statistics, global_statistics, shutdown, nranks
+   :show-inheritance:
+
+.. autoclass:: cudf_polars.engine.dask.DaskEngine
+   :members: from_options, gather_cluster_info, gather_statistics, global_statistics, shutdown, nranks
+   :show-inheritance:
+
+.. autoclass:: cudf_polars.engine.spmd.SPMDEngine
+   :members: from_options, gather_cluster_info, gather_statistics, global_statistics, shutdown, nranks, rank, comm, context
+   :show-inheritance:
+
+.. autoclass:: cudf_polars.engine.default_singleton_engine.DefaultSingletonEngine
+   :members: get_or_create, shutdown
+   :show-inheritance:
+```
+
+The engine classes share a common base class:
+
+```{eval-rst}
+.. autoclass:: cudf_polars.engine.core.StreamingEngine
+   :members: gather_cluster_info, gather_statistics, global_statistics, shutdown, nranks
+   :show-inheritance:
+
+.. autoclass:: cudf_polars.engine.core.ClusterInfo
+   :members:
+```
+
+## Configuration
+
+```{eval-rst}
+.. autoclass:: cudf_polars.engine.options.StreamingOptions
+   :members: from_dict, to_dict, to_rapidsmpf_options, to_executor_options, to_engine_options
+
+.. autodata:: cudf_polars.engine.options.UNSPECIFIED
+
+.. autoclass:: cudf_polars.engine.hardware_binding.HardwareBindingPolicy
+   :members:
+
+.. autofunction:: cudf_polars.engine.hardware_binding.bind_to_gpu
+```
+
+## SPMD helpers
+
+```{eval-rst}
+.. autofunction:: cudf_polars.engine.spmd.allgather_polars_dataframe
+
+.. autofunction:: cudf_polars.streaming.actor_graph.collectives.common.reserve_op_id
+```
+
+## Internal configuration objects
+
+These dataclasses back the `engine_options` surfaced by `pl.GPUEngine` and `StreamingOptions`.
+Most users interact with them through `StreamingOptions` fields rather than directly.
 
 ```{eval-rst}
 .. automodule:: cudf_polars.utils.config
    :members:
-      Cluster,
-      ConfigOptions,
-      CUDAStreamPoolConfig,
       DynamicPlanningOptions,
-      ExecutorType,
-      InMemoryExecutor,
+      MemoryResourceConfig,
       ParquetOptions,
       StreamingExecutor,
       StreamingFallbackMode,

docs/cudf/source/cudf_polars/dask_engine.md

@@ -0,0 +1,198 @@
+(cudf-polars-dask-engine)=
+# Dask
+
+{class}`~cudf_polars.engine.dask.DaskEngine` runs the streaming executor
+on a [Dask distributed][dask-distributed] cluster: one Dask worker per GPU, coordinated by a
+single client process. Partitions are streamed through the query plan and collective operations
+(shuffles, allgathers, joins) run across workers over a shared UCXX communicator. On startup,
+each worker is pinned to the CPU cores and NUMA node closest to its GPU (see
+[Pre-configured GPU clusters](#pre-configured-gpu-clusters) below).
+
+```python
+import polars as pl
+from cudf_polars.engine.dask import DaskEngine
+
+with DaskEngine() as engine:
+    result = (
+        pl.scan_parquet("/data/dataset/*.parquet")
+          .filter(pl.col("amount") > 100)
+          .group_by("customer_id")
+          .agg(pl.col("amount").sum())
+          .collect(engine=engine)
+    )
+    print(result)
+```
+
+With no arguments, {class}`~cudf_polars.engine.dask.DaskEngine` creates a
+`distributed.LocalCluster` with one worker per visible GPU, a `distributed.Client`, and
+bootstraps a UCXX communicator across all workers. On exit, everything it created is torn down.
+
+```{note}
+`.collect()` pulls the full result back to the client process. For large distributed outputs,
+prefer `.sink_*()` or aggregate/sample inside the query before `.collect()`. See
+[Result collection](engines.md#result-collection).
+```
+
+## Configuring `DaskEngine`
+
+For custom configuration, build
+{class}`~cudf_polars.engine.options.StreamingOptions` and use
+`DaskEngine.from_options()`:
+
+```python
+import polars as pl
+from cudf_polars.engine.options import StreamingOptions
+from cudf_polars.engine.dask import DaskEngine
+
+opts = StreamingOptions(num_streaming_threads=8, fallback_mode="silent")
+
+with DaskEngine.from_options(opts) as engine:
+    result = pl.scan_parquet("/data/dataset/*.parquet").collect(engine=engine)
+```
+
+See {doc}`options` for the available fields.
+
+## Bring your own Dask client
+
+Pass an existing `distributed.Client` via `dask_client=` to attach to an already-running
+scheduler:
+
+```python
+from distributed import Client
+import polars as pl
+from cudf_polars.engine.dask import DaskEngine
+
+with Client("scheduler-address:8786") as dc:
+    with DaskEngine(dask_client=dc) as engine:
+        result = pl.scan_parquet("/data/*.parquet").collect(engine=engine)
+```
+
+When you supply the client, {class}`~cudf_polars.engine.dask.DaskEngine`
+leaves it (and the cluster) alone on exit.
+
+(pre-configured-gpu-clusters)=
+### Pre-configured GPU clusters
+
+Some Dask launchers, notably `dask_cuda.LocalCUDACluster`, already pin CPU affinity and set
+`CUDA_VISIBLE_DEVICES` per worker. Disable the built-in hardware binding via
+{class}`~cudf_polars.engine.hardware_binding.HardwareBindingPolicy`
+to avoid having both layers fight over each worker's affinity (the second to run wins, which
+makes the resulting placement non-deterministic):
+
+```python
+from dask_cuda import LocalCUDACluster
+from distributed import Client
+from cudf_polars.engine.dask import DaskEngine
+from cudf_polars.engine.hardware_binding import (
+    HardwareBindingPolicy,
+)
+
+with Client(LocalCUDACluster()) as dc, DaskEngine(
+    dask_client=dc,
+    engine_options={
+        "hardware_binding": HardwareBindingPolicy(enabled=False),
+    },
+) as engine:
+    ...
+```
+
+### Manually launched workers
+
+When launching workers yourself (for example on a multi-node HPC cluster), use the built-in nanny
+preload to assign one GPU per worker. The preload sets `CUDA_VISIBLE_DEVICES` on each worker
+before the process spawns:
+
+```bash
+# On each node, launch one worker per GPU with a single thread each:
+dask worker SCHEDULER_ADDRESS:8786 --nworkers N --nthreads 1 \
+    --preload-nanny cudf_polars.engine.dask
+```
+
+Then connect from the client:
+
+```python
+import polars as pl
+from distributed import Client
+from cudf_polars.engine.dask import DaskEngine
+
+with Client("SCHEDULER_ADDRESS:8786") as dc:
+    with DaskEngine(dask_client=dc) as engine:
+        result = pl.scan_parquet("/data/*.parquet").collect(engine=engine)
+```
+
+Hardware binding (CPU affinity, NUMA, network) is handled automatically by
+{class}`~cudf_polars.engine.dask.DaskEngine`; the nanny preload only
+deals with GPU assignment.
+
+See the [Dask CLI deployment guide][dask-cli] for more on `dask worker` options.
+
+#### Using `dask-cuda-worker`
+
+As an alternative to the built-in nanny preload, you can launch workers with
+[`dask-cuda-worker`][dask-cuda-worker] from the [dask-cuda][dask-cuda] project. It launches one
+worker per visible GPU and installs a set of plugins on every worker: a `CPUAffinity` plugin
+that pins the worker to the NUMA node of its GPU, an `RMMSetup` plugin, and a nanny preload that
+configures UCX.
+
+`DaskEngine` sets up the same things for its own streaming runtime, so the two need to be
+coordinated or they will fight:
+
+* **CPU affinity is unconditional in `dask-cuda-worker`**, the `CPUAffinity` plugin is always
+  installed and there is no CLI flag to turn it off. Pass `hardware_binding=HardwareBindingPolicy(enabled=False)`
+  to `DaskEngine` so it does not try to re-pin affinity on top of dask-cuda's binding.
+* **Do not pass `--rmm-pool-size`, `--rmm-managed-memory`, or similar RMM flags** to
+  `dask-cuda-worker`. Let `DaskEngine` own the memory resource via its `memory_resource_config`
+  (see {doc}`options`) otherwise two different memory resources will be installed on the same
+  worker.
+* **Do not pass `--enable-tcp-over-ucx`, `--enable-infiniband`, `--enable-nvlink`, or
+  `--enable-rdmacm`** to `dask-cuda-worker`. `DaskEngine` bootstraps its own UCXX communicator
+  and will select transports itself. Enabling them on both sides can produce inconsistent UCX
+  configuration across the cluster.
+
+```bash
+# On each node, GPU assignment + CPU affinity only (no RMM, no UCX flags):
+dask-cuda-worker SCHEDULER_ADDRESS:8786
+```
+
+```python
+import polars as pl
+from distributed import Client
+from cudf_polars.engine.dask import DaskEngine
+from cudf_polars.engine.hardware_binding import (
+    HardwareBindingPolicy,
+)
+
+with Client("SCHEDULER_ADDRESS:8786") as dc:
+    with DaskEngine(
+        dask_client=dc,
+        engine_options={
+            # dask-cuda-worker always pins CPU affinity; disable DaskEngine's
+            # binding so the two don't conflict.
+            "hardware_binding": HardwareBindingPolicy(enabled=False),
+        },
+    ) as engine:
+        result = pl.scan_parquet("/data/*.parquet").collect(engine=engine)
+```
+
+## Cluster diagnostics
+
+{meth}`~cudf_polars.engine.dask.DaskEngine.gather_cluster_info` returns
+placement information for every worker:
+
+```python
+with DaskEngine() as engine:
+    print(f"cluster has {engine.nranks} workers")
+    for info in engine.gather_cluster_info():
+        print(
+            f"hostname={info['hostname']}, pid={info['pid']}, "
+            f"CUDA_VISIBLE_DEVICES={info['cuda_visible_devices']}"
+        )
+```
+
+{class}`~cudf_polars.engine.dask.DaskEngine` raises `RuntimeError` if
+created inside an `rrun` cluster.
+
+[dask-distributed]: https://distributed.dask.org/
+[dask-cli]: https://docs.dask.org/en/latest/deploying-cli.html
+[dask-cuda]: https://docs.rapids.ai/api/dask-cuda/nightly/
+[dask-cuda-worker]: https://docs.rapids.ai/api/dask-cuda/nightly/quickstart/#dask-cuda-worker