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prefect.server.events.services.event_persister

The event persister moves event messages from the event bus to storage storage as fast as it can. Never gets tired.

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Functions

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batch_delete 

batch_delete(session: AsyncSession, model: type[T], condition: Any, batch_size: int = 10000) -> int
Perform a batch deletion of database records using a subquery with LIMIT. Works with both PostgreSQL and SQLite. Compared to a basic delete(…).where(…), a batch deletion is more robust against timeouts when handling large tables, which is especially the case if we first delete old entries from long existing tables. Returns:
  • Total number of deleted records

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create_handler 

create_handler(batch_size: int = 20, flush_every: timedelta = timedelta(seconds=5), trim_every: timedelta = timedelta(minutes=15), queue_max_size: int = 50000, max_flush_retries: int = 5) -> AsyncGenerator[MessageHandler, None]
Set up a message handler that will accumulate and send events to the database every batch_size messages, or every flush_every interval to flush any remaining messages. Args:
  • batch_size: Number of events to accumulate before flushing
  • flush_every: Maximum time between flushes
  • trim_every: How often to trim old events
  • queue_max_size: Maximum events in queue before dropping new events
  • max_flush_retries: Consecutive flush failures before dropping events

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Classes

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EventPersister

A service that persists events to the database as they arrive. Methods:

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all_services 

all_services(cls) -> Sequence[type[Self]]
Get list of all service classes

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enabled 

enabled(cls) -> bool
Whether the service is enabled

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enabled_services 

enabled_services(cls) -> list[type[Self]]
Get list of enabled service classes

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environment_variable_name 

environment_variable_name(cls) -> str

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run_services 

run_services(cls) -> NoReturn
Run enabled services until cancelled.

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running 

running(cls) -> AsyncGenerator[None, None]
A context manager that runs enabled services on entry and stops them on exit.

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service_settings 

service_settings(cls) -> ServerServicesEventPersisterSettings

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service_settings 

service_settings(cls) -> ServicesBaseSetting
The Prefect setting that controls whether the service is enabled

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start 

start(self) -> NoReturn

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start 

start(self) -> NoReturn
Start running the service, which may run indefinitely

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started_event 

started_event(self) -> asyncio.Event

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started_event 

started_event(self, value: asyncio.Event) -> None

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stop 

stop(self) -> None

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stop 

stop(self) -> None
Stop the service