eager workflow: use event loop instead of asyncio.run

flytekit/bin/entrypoint.py

@@ -9,6 +9,7 @@
 import sys
 import tempfile
 import traceback
+import warnings
 from sys import exit
 from typing import Callable, List, Optional
 
@@ -68,6 +69,23 @@ def _compute_array_job_index():
     return offset
 
 
+def _get_working_loop():
+    """Returns a running event loop."""
+    try:
+        return asyncio.get_running_loop()
+    except RuntimeError:
+        with warnings.catch_warnings():
+            warnings.simplefilter("error", DeprecationWarning)
+            try:
+                return asyncio.get_event_loop_policy().get_event_loop()
+            # Since version 3.12, DeprecationWarning is emitted if there is no
+            # current event loop.
+            except DeprecationWarning:
+                loop = asyncio.get_event_loop_policy().new_event_loop()
+                asyncio.set_event_loop(loop)
+                return loop
+
+
 def _dispatch_execute(
     ctx: FlyteContext,
     load_task: Callable[[], PythonTask],
@@ -107,7 +125,7 @@ def _dispatch_execute(
         if inspect.iscoroutine(outputs):
             # Handle eager-mode (async) tasks
             logger.info("Output is a coroutine")
-            outputs = asyncio.run(outputs)
+            outputs = _get_working_loop().run_until_complete(outputs)
 
         # Step3a
         if isinstance(outputs, VoidPromise):

tests/flytekit/unit/experimental/test_eager_workflows.py

@@ -1,4 +1,5 @@
 import asyncio
+import mock
 import os
 import sys
 import typing
@@ -9,8 +10,13 @@
 from hypothesis import given
 
 from flytekit import dynamic, task, workflow
+
+from flytekit.bin.entrypoint import _get_working_loop, _dispatch_execute
+from flytekit.core import context_manager
+from flytekit.core.promise import VoidPromise
 from flytekit.exceptions.user import FlyteValidationException
 from flytekit.experimental import EagerException, eager
+from flytekit.models import literals as _literal_models
 from flytekit.types.directory import FlyteDirectory
 from flytekit.types.file import FlyteFile
 from flytekit.types.structured import StructuredDataset
@@ -275,3 +281,29 @@ async def eager_wf_flyte_directory() -> str:
 
     result = asyncio.run(eager_wf_flyte_directory())
     assert result == "some data"
+
+
+@mock.patch("flytekit.core.utils.load_proto_from_file")
+@mock.patch("flytekit.core.data_persistence.FileAccessProvider.get_data")
+@mock.patch("flytekit.core.data_persistence.FileAccessProvider.put_data")
+@mock.patch("flytekit.core.utils.write_proto_to_file")
+def test_eager_workflow_dispatch(*args):
+    """Test that event loop is preserved after executing eager workflow via dispatch."""
+
+    @eager
+    async def eager_wf():
+        await asyncio.sleep(0.1)
+        return
+
+    ctx = context_manager.FlyteContext.current_context()
+    with context_manager.FlyteContextManager.with_context(
+        ctx.with_execution_state(
+            ctx.execution_state.with_params(mode=context_manager.ExecutionState.Mode.TASK_EXECUTION)
+        )
+    ) as ctx:
+        loop = asyncio.new_event_loop()
+        asyncio.set_event_loop(loop)
+        asyncio.events.set_event_loop(loop)
+        _dispatch_execute(ctx, lambda: eager_wf, "inputs path", "outputs prefix")
+        loop_after_execute = asyncio.get_event_loop_policy().get_event_loop()
+        assert loop == loop_after_execute