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prefect.concurrency.services

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Classes

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ConcurrencySlotAcquisitionService

Methods:

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acquire 

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

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ConcurrencySlotAcquisitionWithLeaseService

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:

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acquire 

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