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Documentation Index

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prefect.server.events.ordering.memory

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Classes

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EventBeingProcessed

Indicates that an event is currently being processed and should not be processed until it is finished. This may happen due to concurrent processing.

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CausalOrdering

Methods:

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clear 

clear(self) -> None
Clear all data for this scope.

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clear_all_scopes 

clear_all_scopes(cls) -> None
Clear all data for all scopes - useful for testing.

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event_has_been_seen 

event_has_been_seen(self, event: UUID | Event) -> bool

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event_has_started_processing 

event_has_started_processing(self, event: UUID | Event) -> bool

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event_is_processing 

event_is_processing(self, event: ReceivedEvent) -> AsyncGenerator[None, None]
Mark an event as being processed for the duration of its lifespan through the ordering system.

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followers_by_id 

followers_by_id(self, follower_ids: list[UUID]) -> list[ReceivedEvent]
Returns the events with the given IDs, in the order they occurred.

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forget_event_is_processing 

forget_event_is_processing(self, event: ReceivedEvent) -> None

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forget_follower 

forget_follower(self, follower: ReceivedEvent) -> None
Forget that this event is waiting on another event to arrive.

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get_followers 

get_followers(self, leader: ReceivedEvent) -> list[ReceivedEvent]
Returns events that were waiting on this leader event to arrive.

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get_lost_followers 

get_lost_followers(self) -> list[ReceivedEvent]
Returns events that were waiting on a leader event that never arrived.

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preceding_event_confirmed 

preceding_event_confirmed(self, handler: event_handler, event: ReceivedEvent, depth: int = 0) -> AsyncGenerator[None, None]
Events may optionally declare that they logically follow another event, so that we can preserve important event orderings in the face of unreliable delivery and ordering of messages from the queues. This function keeps track of the ID of each event that this shard has successfully processed going back to the PRECEDING_EVENT_LOOKBACK period. If an event arrives that must follow another one, confirm that we have recently seen and processed that event before proceeding. Args:
  • handler: The function to call when an out-of-order event is ready to be processed
  • event: The event to be processed. This object should include metadata indicating if and what event it follows.
  • depth: The current recursion depth, used to prevent infinite recursion due to cyclic dependencies between events. Defaults to 0.
Raises EventArrivedEarly if the current event shouldn’t be processed yet.

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record_event_as_processing 

record_event_as_processing(self, event: ReceivedEvent) -> bool
Record that an event is being processed, returning False if already processing.

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record_event_as_seen 

record_event_as_seen(self, event: ReceivedEvent) -> None

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record_follower 

record_follower(self, event: ReceivedEvent) -> None
Remember that this event is waiting on another event to arrive.

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wait_for_leader 

wait_for_leader(self, event: ReceivedEvent) -> None
Given an event, wait for its leader to be processed before proceeding, or raise EventArrivedEarly if we would wait too long in this attempt.