---
title: event_persister
sidebarTitle: 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

### `batch_delete` <sup><a href="https://github.com/PrefectHQ/prefect/blob/main/src/prefect/server/events/services/event_persister.py#L42" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
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


### `create_handler` <sup><a href="https://github.com/PrefectHQ/prefect/blob/main/src/prefect/server/events/services/event_persister.py#L141" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
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


## Classes

### `EventPersister` <sup><a href="https://github.com/PrefectHQ/prefect/blob/main/src/prefect/server/events/services/event_persister.py#L77" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


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


**Methods:**

#### `all_services` <sup><a href="https://github.com/PrefectHQ/prefect/blob/main/src/prefect/server/services/base.py#L69" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
all_services(cls) -> Sequence[type[Self]]
```

Get list of all service classes


#### `enabled` <sup><a href="https://github.com/PrefectHQ/prefect/blob/main/src/prefect/server/services/base.py#L64" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
enabled(cls) -> bool
```

Whether the service is enabled


#### `enabled_services` <sup><a href="https://github.com/PrefectHQ/prefect/blob/main/src/prefect/server/services/base.py#L83" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
enabled_services(cls) -> list[type[Self]]
```

Get list of enabled service classes


#### `environment_variable_name` <sup><a href="https://github.com/PrefectHQ/prefect/blob/main/src/prefect/server/services/base.py#L60" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
environment_variable_name(cls) -> str
```

#### `run_services` <sup><a href="https://github.com/PrefectHQ/prefect/blob/main/src/prefect/server/services/base.py#L104" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
run_services(cls) -> NoReturn
```

Run enabled services until cancelled.


#### `running` <sup><a href="https://github.com/PrefectHQ/prefect/blob/main/src/prefect/server/services/base.py#L89" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
running(cls) -> AsyncGenerator[None, None]
```

A context manager that runs enabled services on entry and stops them on
exit.


#### `service_settings` <sup><a href="https://github.com/PrefectHQ/prefect/blob/main/src/prefect/server/events/services/event_persister.py#L83" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
service_settings(cls) -> ServerServicesEventPersisterSettings
```

#### `service_settings` <sup><a href="https://github.com/PrefectHQ/prefect/blob/main/src/prefect/server/services/base.py#L55" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
service_settings(cls) -> ServicesBaseSetting
```

The Prefect setting that controls whether the service is enabled


#### `start` <sup><a href="https://github.com/PrefectHQ/prefect/blob/main/src/prefect/server/events/services/event_persister.py#L100" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
start(self) -> NoReturn
```

#### `start` <sup><a href="https://github.com/PrefectHQ/prefect/blob/main/src/prefect/server/services/base.py#L114" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
start(self) -> NoReturn
```

Start running the service, which may run indefinitely


#### `started_event` <sup><a href="https://github.com/PrefectHQ/prefect/blob/main/src/prefect/server/events/services/event_persister.py#L91" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
started_event(self) -> asyncio.Event
```

#### `started_event` <sup><a href="https://github.com/PrefectHQ/prefect/blob/main/src/prefect/server/events/services/event_persister.py#L97" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

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

#### `stop` <sup><a href="https://github.com/PrefectHQ/prefect/blob/main/src/prefect/server/events/services/event_persister.py#L125" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
stop(self) -> None
```

#### `stop` <sup><a href="https://github.com/PrefectHQ/prefect/blob/main/src/prefect/server/services/base.py#L119" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
stop(self) -> None
```

Stop the service

