flowno.core.event_loop.event_loop

Custom event loop implementation for Flowno’s asynchronous execution model.

This module provides a lightweight, cooperative multitasking event loop that handles: - Task scheduling and management - Sleeping/timing operations - Network socket operations - Asynchronous queue operations - Task joining and cancellation

The EventLoop class is the central component of Flowno’s asynchronous execution, implementing a command-based coroutine system similar to Python’s asyncio.

This can be used as a standalone event loop without the rest of the Flowno runtime.

class flowno.core.event_loop.event_loop.EventLoop

The core event loop implementation for Flowno’s asynchronous execution model.

Manages task scheduling, I/O operations, and synchronization primitives for the dataflow runtime.

_handle_command(current_task_packet: tuple[Coroutine[Command, Any, Any], Any, Exception | None], command: Command) → bool

Handle the command yielded by the current task.

Returns True if the command was successfully handled.

cancel(raw_task: Coroutine[Command, Any, Any]) → bool

Cancel a task.

Parameters:

raw_task – The task to cancel.

Returns:

True if the task was successfully cancelled; False if it was already finished or errored.

handle_queue_close(queue: AsyncQueue[Any]) → None

Handle a queue being closed. Also resumes all tasks waiting on the queue with an appropriate exception.

has_living_tasks() → bool

Return True if there are any tasks still needing processing.

run_until_complete(root_task: Coroutine[Command, Any, _ReturnT], join: bool = False, wait_for_spawned_tasks: bool = True, _debug_max_wait_time: float | None = None) → _ReturnT | None

Run the event loop until the given root task is complete.

This method executes the main event loop, processing tasks, handling I/O operations, and managing task synchronization until the root task completes. It can optionally wait for all spawned tasks to finish as well.

Parameters:

• root_task (RawTask[Command, Any, _ReturnT]) – The coroutine task to execute as the root of the execution graph.

• join (bool) – When True, returns the result value of the root task. When False, returns None regardless of the task’s result. If the task raises an exception and join=True, the exception is re-raised.

• wait_for_spawned_tasks (bool) – When True, continue running the event loop until all tasks spawned by the root task have completed. When False, stop as soon as the root task completes.

• _debug_max_wait_time (float | None) – Optional timeout value in seconds used for debugging. Limits how long the event loop will wait for network or sleeping operations.

Returns:

If join=True, returns the result of the root task (of type _ReturnT).

If join=False, returns None.

Return type:

_ReturnT | None

Raises:

• RuntimeError – If the event loop exits without completing the root task when join=True.

• Exception – Any exception raised by the root task is propagated if join=True.