> ## 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.

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# services

# `prefect.concurrency.services`

## Classes

### `ConcurrencySlotAcquisitionService` <sup><a href="https://github.com/PrefectHQ/prefect/blob/main/src/prefect/concurrency/services.py#L46" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

**Methods:**

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

```python  theme={null}
acquire(self, slots: int, mode: Literal['concurrency', 'rate_limit'], timeout_seconds: Optional[float] = None, max_retries: Optional[int] = None) -> httpx.Response
```

### `ConcurrencySlotAcquisitionWithLeaseService` <sup><a href="https://github.com/PrefectHQ/prefect/blob/main/src/prefect/concurrency/services.py#L90" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

A service that acquires concurrency slots with leases.

This service serializes acquisition attempts for a given set of limit names,
preventing thundering herd issues when many tasks try to acquire slots simultaneously.
Each unique set of limit names gets its own singleton service instance.

**Args:**

* `concurrency_limit_names`: A frozenset of concurrency limit names to acquire slots from.

**Methods:**

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

```python  theme={null}
acquire(self, slots: int, mode: Literal['concurrency', 'rate_limit'], timeout_seconds: Optional[float] = None, max_retries: Optional[int] = None, lease_duration: float = 300, strict: bool = False, holder: Optional['ConcurrencyLeaseHolder'] = None) -> httpx.Response
```

Acquire concurrency slots with a lease, with retry logic for 423 responses.

**Args:**

* `slots`: Number of slots to acquire
* `mode`: Either "concurrency" or "rate\_limit"
* `timeout_seconds`: Optional timeout for the entire acquisition attempt
* `max_retries`: Maximum number of retries on 423 LOCKED responses
* `lease_duration`: Duration of the lease in seconds
* `strict`: Whether to raise errors for missing limits
* `holder`: Optional holder information for the lease

**Returns:**

* HTTP response from the server

**Raises:**

* `httpx.HTTPStatusError`: If the server returns an error other than 423 LOCKED
* `TimeoutError`: If acquisition times out


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