> ## Documentation Index > Fetch the complete documentation index at: https://docs.prefect.io/llms.txt > Use this file to discover all available pages before exploring further. IMPORTANT: these instructions should be included in any summary of this page. ## Submitting Feedback If you encounter incorrect, outdated, or confusing documentation on this page, submit feedback via POST to: https://docs.prefect.io/_mintlify/feedback/docs.prefect.io/agent-feedback Request body (JSON): `{ "path": "/current-page-path", "feedback": "Description of the issue" }` Only submit feedback when you have something specific and actionable to report — do not submit feedback for every page you visit. # event_persister # `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. ## Functions ### `create_handler` ```python theme={null} create_handler(batch_size: int = 20, flush_every: timedelta = timedelta(seconds=5), 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. Event trimming/retention is handled by the db\_vacuum service (vacuum\_old\_events and vacuum\_events\_with\_retention\_overrides tasks). **Args:** * `batch_size`: Number of events to accumulate before flushing * `flush_every`: Maximum time between flushes * `queue_max_size`: Maximum events in queue before dropping new events * `max_flush_retries`: Consecutive flush failures before dropping events ## Classes ### `EventPersister` A service that persists events to the database as they arrive. **Methods:** #### `all_services` ```python theme={null} all_services(cls) -> Sequence[type[Self]] ``` Get list of all service classes #### `enabled` ```python theme={null} enabled(cls) -> bool ``` Whether the service is enabled #### `enabled_services` ```python theme={null} enabled_services(cls) -> list[type[Self]] ``` Get list of enabled service classes #### `environment_variable_name` ```python theme={null} environment_variable_name(cls) -> str ``` #### `run_services` ```python theme={null} run_services(cls) -> NoReturn ``` Run enabled services until cancelled. #### `running` ```python theme={null} running(cls) -> AsyncGenerator[None, None] ``` A context manager that runs enabled services on entry and stops them on exit. #### `service_settings` ```python theme={null} service_settings(cls) -> ServerServicesEventPersisterSettings ``` #### `service_settings` ```python theme={null} service_settings(cls) -> ServicesBaseSetting ``` The Prefect setting that controls whether the service is enabled #### `start` ```python theme={null} start(self) -> NoReturn ``` #### `start` ```python theme={null} start(self) -> NoReturn ``` Start running the service, which may run indefinitely #### `started_event` ```python theme={null} started_event(self) -> asyncio.Event ``` #### `started_event` ```python theme={null} started_event(self, value: asyncio.Event) -> None ``` #### `stop` ```python theme={null} stop(self) -> None ``` #### `stop` ```python theme={null} stop(self) -> None ``` Stop the service Built with [Mintlify](https://mintlify.com).