---
title: services
sidebarTitle: 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
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
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

