a2a.server.events.event_queue_v2 module

class a2a.server.events.event_queue_v2.EventQueueSink(*args: Any, **kwargs: Any)

Bases: EventQueue

The Child EventQueue.

Acts as a read-only consumer endpoint. Events are pushed here exclusively by the parent EventQueueSource’s dispatcher task.

async close(immediate: bool = False) → None

Closes the child sink queue.

It is safe to call it multiple times. If immediate is True, the queue will be closed without waiting for all events to be processed. If immediate is False, the queue will be closed after all events are processed (and confirmed with task_done() calls).

async dequeue_event() → Message | Task | TaskStatusUpdateEvent | TaskArtifactUpdateEvent

Pulls an event from the sink queue.

async enqueue_event(event: Message | Task | TaskStatusUpdateEvent | TaskArtifactUpdateEvent) → None

Sinks are read-only and cannot have events directly enqueued to them.

is_closed() → bool

[DEPRECATED] Checks if the queue is closed.

NOTE: Relying on this for enqueue logic introduces race conditions. It is maintained primarily for backwards compatibility, workarounds for Python 3.10/3.12 async queues in consumers, and for the test suite.

property queue: Queue[Message | Task | TaskStatusUpdateEvent | TaskArtifactUpdateEvent]

Returns the underlying asyncio.Queue of this sink.

async tap(max_queue_size: int = 1024) → EventQueueSink

Creates a child queue that receives future events.

Note: The tapped queue may receive some old events if the incoming event queue is lagging behind and hasn’t dispatched them yet.

task_done() → None

Signals that a work on dequeued event is complete in this sink queue.

class a2a.server.events.event_queue_v2.EventQueueSource(*args: Any, **kwargs: Any)

Bases: EventQueue

The Parent EventQueue.

Acts as the single entry point for producers. Events pushed here are buffered in _incoming_queue and distributed to all child Sinks by a background dispatcher task.

async close(immediate: bool = False) → None

Closes the queue and all its child sinks.

It is safe to call it multiple times. If immediate is True, the queue will be closed without waiting for all events to be processed. If immediate is False, the queue will be closed after all events are processed (and confirmed with task_done() calls).

WARNING: Closing the parent queue with immediate=False is a deadlock risk if there are unconsumed events in any of the child sinks and the consumer has crashed without draining its queue. It is highly recommended to wrap graceful shutdowns with a timeout, e.g., asyncio.wait_for(queue.close(immediate=False), timeout=…).

async dequeue_event() → Message | Task | TaskStatusUpdateEvent | TaskArtifactUpdateEvent

Pulls an event from the default internal sink queue.

async enqueue_event(event: Message | Task | TaskStatusUpdateEvent | TaskArtifactUpdateEvent) → None

Enqueues an event to this queue and all its children.

is_closed() → bool

[DEPRECATED] Checks if the queue is closed.

NOTE: Relying on this for enqueue logic introduces race conditions. It is maintained primarily for backwards compatibility, workarounds for Python 3.10/3.12 async queues in consumers, and for the test suite.

property queue: Queue[Message | Task | TaskStatusUpdateEvent | TaskArtifactUpdateEvent]

Returns the underlying asyncio.Queue of the default sink.

async remove_sink(sink: EventQueueSink) → None

Removes a sink from the source’s internal list.

async tap(max_queue_size: int = 1024) → EventQueueSink

Taps the event queue to create a new child queue that receives future events.

Note: The tapped queue may receive some old events if the incoming event queue is lagging behind and hasn’t dispatched them yet.

task_done() → None

Signals that a work on dequeued event is complete via the default internal sink queue.

async test_only_join_incoming_queue() → None

Wait for incoming queue to be fully processed.