prefect.concurrency.services

Classes

ConcurrencySlotAcquisitionService ^{<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>}

Methods:

acquire ^{<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>}

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

ConcurrencySlotAcquisitionWithLeaseService ^{<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>}

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 ^{<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>}

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