feat: Reinstate disk-based shuffle (#47)

* old old shuffle reader/writer

* old old shuffle reader/writer

* remove ray shuffle

* revert more changes

* save progress

* update expected plans

* remove unused code

* fix regression

Author: andygrove

Cargo.lock

@@ -32,10 +32,12 @@ build = "build.rs"
 datafusion = { version = "42.0.0", features = ["pyarrow", "avro"] }
 datafusion-proto = "42.0.0"
 futures = "0.3"
+glob = "0.3.1"
 log = "0.4"
 prost = "0.13"
 pyo3 = { version = "0.22", features = ["extension-module", "abi3", "abi3-py38"] }
 tokio = { version = "1.40", features = ["macros", "rt", "rt-multi-thread", "sync"] }
+uuid = "1.11.0"
 
 [build-dependencies]
 prost-types = "0.13"

Cargo.toml

@@ -29,23 +29,31 @@
 from datafusion import SessionContext
 
 
-def schedule_execution(
-    graph: ExecutionGraph,
-    stage_id: int,
-    is_final_stage: bool,
-) -> list[ray.ObjectRef]:
-    stage = graph.get_query_stage(stage_id)
+@ray.remote(num_cpus=0)
+def execute_query_stage(
+    query_stages: list[QueryStage],
+    stage_id: int
+) -> tuple[int, list[ray.ObjectRef]]:
+    """
+    Execute a query stage on the workers.
+
+    Returns the stage ID, and a list of futures for the output partitions of the query stage.
+    """
+    stage = QueryStage(stage_id, query_stages[stage_id])
+
     # execute child stages first
-    # A list of (stage ID, list of futures) for each child stage
-    # Each list is a 2-D array of (input partitions, output partitions).
-    child_outputs = []
+    child_futures = []
     for child_id in stage.get_child_stage_ids():
-        child_outputs.append((child_id, schedule_execution(graph, child_id, False)))
-        # child_outputs.append((child_id, schedule_execution(graph, child_id)))
+        child_futures.append(
+            execute_query_stage.remote(query_stages, child_id)
+        )
 
+    # if the query stage has a single output partition then we need to execute for the output
+    # partition, otherwise we need to execute in parallel for each input partition
     concurrency = stage.get_input_partition_count()
     output_partitions_count = stage.get_output_partition_count()
-    if is_final_stage:
+    if output_partitions_count == 1:
+        # reduce stage
         print("Forcing reduce stage concurrency from {} to 1".format(concurrency))
         concurrency = 1
 
@@ -55,50 +63,33 @@ def schedule_execution(
         )
     )
 
-    def _get_worker_inputs(
-        part: int,
-    ) -> tuple[list[tuple[int, int, int]], list[ray.ObjectRef]]:
-        ids = []
-        futures = []
-        for child_stage_id, child_futures in child_outputs:
-            for i, lst in enumerate(child_futures):
-                if isinstance(lst, list):
-                    for j, f in enumerate(lst):
-                        if concurrency == 1 or j == part:
-                            # If concurrency is 1, pass in all shuffle partitions. Otherwise,
-                            # only pass in the partitions that match the current worker partition.
-                            ids.append((child_stage_id, i, j))
-                            futures.append(f)
-                elif concurrency == 1 or part == 0:
-                    ids.append((child_stage_id, i, 0))
-                    futures.append(lst)
-        return ids, futures
+    # A list of (stage ID, list of futures) for each child stage
+    # Each list is a 2-D array of (input partitions, output partitions).
+    child_outputs = ray.get(child_futures)
+
+    # if we are using disk-based shuffle, wait until the child stages to finish
+    # writing the shuffle files to disk first.
+    ray.get([f for _, lst in child_outputs for f in lst])
 
     # schedule the actual execution workers
     plan_bytes = stage.get_execution_plan_bytes()
     futures = []
     opt = {}
-    # TODO not sure why we had this but my Ray cluster could not find suitable resource
-    # until I commented this out
-    # opt["resources"] = {"worker": 1e-3}
-    opt["num_returns"] = output_partitions_count
     for part in range(concurrency):
-        ids, inputs = _get_worker_inputs(part)
         futures.append(
             execute_query_partition.options(**opt).remote(
-                stage_id, plan_bytes, part, ids, *inputs
+                stage_id, plan_bytes, part
             )
         )
-    return futures
+
+    return stage_id, futures
 
 
 @ray.remote
 def execute_query_partition(
     stage_id: int,
     plan_bytes: bytes,
-    part: int,
-    input_partition_ids: list[tuple[int, int, int]],
-    *input_partitions: list[pa.RecordBatch],
+    part: int
 ) -> Iterable[pa.RecordBatch]:
     start_time = time.time()
     # plan = datafusion_ray.deserialize_execution_plan(plan_bytes)
@@ -109,13 +100,10 @@ def execute_query_partition(
     #         input_partition_ids,
     #     )
     # )
-    partitions = [
-        (s, j, p) for (s, _, j), p in zip(input_partition_ids, input_partitions)
-    ]
     # This is delegating to DataFusion for execution, but this would be a good place
     # to plug in other execution engines by translating the plan into another engine's plan
     # (perhaps via Substrait, once DataFusion supports converting a physical plan to Substrait)
-    ret = datafusion_ray.execute_partition(plan_bytes, part, partitions)
+    ret = datafusion_ray.execute_partition(plan_bytes, part)
     duration = time.time() - start_time
     event = {
         "cat": f"{stage_id}-{part}",
@@ -153,19 +141,24 @@ def sql(self, sql: str) -> pa.RecordBatch:
             return []
 
         df = self.df_ctx.sql(sql)
-        execution_plan = df.execution_plan()
+        return self.plan(df.execution_plan())
+
+    def plan(self, execution_plan: Any) -> pa.RecordBatch:
 
         graph = self.ctx.plan(execution_plan)
         final_stage_id = graph.get_final_query_stage().id()
-        partitions = schedule_execution(graph, final_stage_id, True)
+        # serialize the query stages and store in Ray object store
+        query_stages = [
+                graph.get_query_stage(i).get_execution_plan_bytes()
+            for i in range(final_stage_id + 1)
+        ]
+        # schedule execution
+        future = execute_query_stage.remote(
+            query_stages,
+            final_stage_id
+        )
+        _, partitions = ray.get(future)
         # assert len(partitions) == 1, len(partitions)
         result_set = ray.get(partitions[0])
         return result_set
 
-    def plan(self, physical_plan: Any) -> pa.RecordBatch:
-        graph = self.ctx.plan(physical_plan)
-        final_stage_id = graph.get_final_query_stage().id()
-        partitions = schedule_execution(graph, final_stage_id, True)
-        # assert len(partitions) == 1, len(partitions)
-        result_set = ray.get(partitions[0])
-        return result_set

datafusion_ray/context.py

@@ -16,8 +16,7 @@
 // under the License.
 
 use crate::planner::{make_execution_graph, PyExecutionGraph};
-use crate::shuffle::{RayShuffleReaderExec, ShuffleCodec};
-use datafusion::arrow::pyarrow::FromPyArrow;
+use crate::shuffle::ShuffleCodec;
 use datafusion::arrow::pyarrow::ToPyArrow;
 use datafusion::arrow::record_batch::RecordBatch;
 use datafusion::error::{DataFusionError, Result};
@@ -31,7 +30,7 @@ use futures::StreamExt;
 use prost::Message;
 use pyo3::exceptions::PyRuntimeError;
 use pyo3::prelude::*;
-use pyo3::types::{PyBytes, PyList, PyLong, PyTuple};
+use pyo3::types::{PyBytes, PyTuple};
 use std::collections::HashMap;
 use std::sync::Arc;
 use tokio::runtime::Runtime;
@@ -117,22 +116,20 @@ impl PyContext {
         &self,
         plan: &Bound<'_, PyBytes>,
         part: usize,
-        inputs: PyObject,
         py: Python,
     ) -> PyResult<PyResultSet> {
-        execute_partition(plan, part, inputs, py)
+        execute_partition(plan, part, py)
     }
 }
 
 #[pyfunction]
 pub fn execute_partition(
     plan_bytes: &Bound<'_, PyBytes>,
     part: usize,
-    inputs: PyObject,
     py: Python,
 ) -> PyResult<PyResultSet> {
     let plan = deserialize_execution_plan(plan_bytes)?;
-    _execute_partition(plan, part, inputs)
+    _execute_partition(plan, part)
         .unwrap()
         .into_iter()
         .map(|batch| batch.to_pyarrow(py))
@@ -170,59 +167,10 @@ pub fn deserialize_execution_plan(proto_msg: &Bound<PyBytes>) -> PyResult<Arc<dy
     Ok(plan)
 }
 
-/// Iterate down an ExecutionPlan and set the input objects for RayShuffleReaderExec.
-fn _set_inputs_for_ray_shuffle_reader(
-    plan: Arc<dyn ExecutionPlan>,
-    input_partitions: &Bound<'_, PyList>,
-) -> Result<()> {
-    if let Some(reader_exec) = plan.as_any().downcast_ref::<RayShuffleReaderExec>() {
-        let exec_stage_id = reader_exec.stage_id;
-        // iterate over inputs, wrap in PyBytes and set as input objects
-        for item in input_partitions.iter() {
-            let pytuple = item
-                .downcast::<PyTuple>()
-                .map_err(|e| DataFusionError::Execution(format!("{}", e)))?;
-            let stage_id = pytuple
-                .get_item(0)
-                .map_err(|e| DataFusionError::Execution(format!("{}", e)))?
-                .downcast::<PyLong>()
-                .map_err(|e| DataFusionError::Execution(format!("{}", e)))?
-                .extract::<usize>()
-                .map_err(|e| DataFusionError::Execution(format!("{}", e)))?;
-            if stage_id != exec_stage_id {
-                continue;
-            }
-            let part = pytuple
-                .get_item(1)
-                .map_err(|e| DataFusionError::Execution(format!("{}", e)))?
-                .downcast::<PyLong>()
-                .map_err(|e| DataFusionError::Execution(format!("{}", e)))?
-                .extract::<usize>()
-                .map_err(|e| DataFusionError::Execution(format!("{}", e)))?;
-            let batch = RecordBatch::from_pyarrow_bound(
-                &pytuple
-                    .get_item(2)
-                    .map_err(|e| DataFusionError::Execution(format!("{}", e)))?,
-            )
-            .map_err(|e| DataFusionError::Execution(format!("{}", e)))?;
-            reader_exec.add_input_partition(part, batch)?;
-        }
-    } else {
-        for child in plan.children() {
-            _set_inputs_for_ray_shuffle_reader(child.to_owned(), input_partitions)?;
-        }
-    }
-    Ok(())
-}
-
 /// Execute a partition of a query plan. This will typically be executing a shuffle write and
 /// write the results to disk, except for the final query stage, which will return the data.
 /// inputs is a list of tuples of (stage_id, partition_id, bytes) for each input partition.
-fn _execute_partition(
-    plan: Arc<dyn ExecutionPlan>,
-    part: usize,
-    inputs: PyObject,
-) -> Result<Vec<RecordBatch>> {
+fn _execute_partition(plan: Arc<dyn ExecutionPlan>, part: usize) -> Result<Vec<RecordBatch>> {
     let ctx = Arc::new(TaskContext::new(
         Some("task_id".to_string()),
         "session_id".to_string(),
@@ -233,13 +181,6 @@ fn _execute_partition(
         Arc::new(RuntimeEnv::default()),
     ));
 
-    Python::with_gil(|py| {
-        let input_partitions = inputs
-            .downcast_bound::<PyList>(py)
-            .map_err(|e| DataFusionError::Execution(format!("{}", e)))?;
-        _set_inputs_for_ray_shuffle_reader(plan.clone(), input_partitions)
-    })?;
-
     // create a Tokio runtime to run the async code
     let rt = Runtime::new().unwrap();
 

src/context.rs

@@ -17,7 +17,7 @@
 
 use crate::query_stage::PyQueryStage;
 use crate::query_stage::QueryStage;
-use crate::shuffle::{RayShuffleReaderExec, RayShuffleWriterExec};
+use crate::shuffle::{ShuffleReaderExec, ShuffleWriterExec};
 use datafusion::error::Result;
 use datafusion::physical_plan::coalesce_partitions::CoalescePartitionsExec;
 use datafusion::physical_plan::repartition::RepartitionExec;
@@ -29,6 +29,7 @@ use pyo3::prelude::*;
 use std::collections::HashMap;
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::Arc;
+use uuid::Uuid;
 
 #[pyclass(name = "ExecutionGraph", module = "datafusion_ray", subclass)]
 pub struct PyExecutionGraph {
@@ -200,11 +201,15 @@ fn create_shuffle_exchange(
     // introduce shuffle to produce one output partition
     let stage_id = graph.next_id();
 
+    // create temp dir for stage shuffle files
+    let temp_dir = create_temp_dir(stage_id)?;
+
     let shuffle_writer_input = plan.clone();
-    let shuffle_writer: Arc<dyn ExecutionPlan> = Arc::new(RayShuffleWriterExec::new(
+    let shuffle_writer: Arc<dyn ExecutionPlan> = Arc::new(ShuffleWriterExec::new(
         stage_id,
         shuffle_writer_input,
         partitioning_scheme.clone(),
+        &temp_dir,
     ));
 
     debug!(
@@ -214,13 +219,22 @@ fn create_shuffle_exchange(
 
     let stage_id = graph.add_query_stage(stage_id, shuffle_writer);
     // replace the plan with a shuffle reader
-    Ok(Arc::new(RayShuffleReaderExec::new(
+    Ok(Arc::new(ShuffleReaderExec::new(
         stage_id,
         plan.schema(),
         partitioning_scheme,
+        &temp_dir,
     )))
 }
 
+fn create_temp_dir(stage_id: usize) -> Result<String> {
+    let uuid = Uuid::new_v4();
+    let temp_dir = format!("/tmp/ray-sql-{uuid}-stage-{stage_id}");
+    debug!("Creating temp shuffle dir: {temp_dir}");
+    std::fs::create_dir(&temp_dir)?;
+    Ok(temp_dir)
+}
+
 #[cfg(test)]
 mod test {
     use super::*;

src/planner.rs

@@ -11,25 +11,29 @@ import "datafusion.proto";
 
 message RaySqlExecNode {
   oneof PlanType {
-    RayShuffleReaderExecNode ray_shuffle_reader = 3;
-    RayShuffleWriterExecNode ray_shuffle_writer = 4;
+    ShuffleReaderExecNode shuffle_reader = 1;
+    ShuffleWriterExecNode shuffle_writer = 2;
   }
 }
 
-message RayShuffleReaderExecNode {
+message ShuffleReaderExecNode {
   // stage to read from
   uint32 stage_id = 1;
   // schema of the shuffle stage
   datafusion_common.Schema schema = 2;
   // this must match the output partitioning of the writer we are reading from
   datafusion.PhysicalHashRepartition partitioning = 3;
+  // directory for shuffle files
+  string shuffle_dir = 4;
 }
 
-message RayShuffleWriterExecNode {
+message ShuffleWriterExecNode {
   // stage that is writing the shuffle files
   uint32 stage_id = 1;
   // plan to execute
   datafusion.PhysicalPlanNode plan = 2;
   // output partitioning schema
   datafusion.PhysicalHashRepartition partitioning = 3;
+  // directory for shuffle files
+  string shuffle_dir = 4;
 }