bus

The event bus used for telemetry across the system.

Defines Subscription and EventBus. Publishers emit TelemetryRecords; subscribers register a topic string (with "*" matching every record), an optional filter, and a handler. A record is dispatched to a subscription when its topic relates to the record's kind (see EventBus.process_event for the exact comparison). While no subscribers exist, published records are queued (up to a maximum) for later delivery via process_unprocessed_events.

EventBus(maximum_queue_size=500, subscribers=list(), unprocessed_events=list()) dataclass

Represents an event bus for communication between different parts of the system.

Attributes:

Name	Type	Description
subscribers	list[Subscription]	The list of subscribers to the bus.
unprocessed_events	list[TelemetryRecord]	The list of unprocessed events. When there are no subscribers, events are queued here.
maximum_queue_size	int	The maximum size of the event queue.

process_event(event, subscription)

Process a record for a given subscription.

Parameters:

Name	Type	Description	Default
event	TelemetryRecord	The telemetry record to process.	required
subscription	Subscription	The subscription to process the record for.	required

process_unprocessed_events()

Deliver queued events to the current subscribers.

Runs every queued event through every subscription (subject to the usual topic and filter checks). The queue is not cleared, so events remain available for subscribers added later.

publish(event)

Publish a record to the bus.

Parameters:

Name	Type	Description	Default
event	TelemetryRecord	The telemetry record to publish.	required

subscribe(topic, handler, filter=None, once=False)

Subscribe a handler to a topic.

Parameters:

Name	Type	Description	Default
topic	str	The topic to subscribe to.	required
handler	Callable[[TelemetryRecord], None]	The handler to call when an event is published to the topic.	required
filter	Callable | None	An optional filter function to filter events.	None
once	bool	Whether to only handle one event.	False

Returns:

Type	Description
Subscription	The subscription object.

unsubscribe(subscription)

Unsubscribe a handler from the bus.

Parameters:

Name	Type	Description	Default
subscription	Subscription	The subscription to remove.	required

Subscription(topic, handler, filter=None, once=False) dataclass

Represents a subscription to a kind of record on the bus.

Attributes:

Name	Type	Description
topic	str	The record kind to which the subscription is made ("*" for all).
handler	Callable[[TelemetryRecord], None]	The handler function to be called when a record is published to the topic.
filter	Callable | None	An optional filter function to filter records.
once	bool	Whether the subscription should be removed after the first record.