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prefect.server.services.scheduler

The Scheduler service.

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Classes

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TryAgain

Internal control-flow exception used to retry the Scheduler’s main loop

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Scheduler

Schedules flow runs from deployments. Methods:

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run_once 

run_once(self, db: PrefectDBInterface) -> None
Schedule flow runs by:
  • Querying for deployments with active schedules
  • Generating the next set of flow runs based on each deployments schedule
  • Inserting all scheduled flow runs into the database
All inserted flow runs are committed to the database at the termination of the loop.

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run_once 

run_once(self) -> None
Represents one loop of the service. Subclasses must override this method. To actually run the service once, call LoopService().start(loops=1) instead of LoopService().run_once(), because this method will not invoke setup and teardown methods properly.

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service_settings 

service_settings(cls) -> ServicesBaseSetting

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start 

start(self, loops: None = None) -> NoReturn
Run the service indefinitely.

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stop 

stop(self, block: bool = True) -> None
Gracefully stops a running LoopService and optionally blocks until the service stops. Args:
  • block: if True, blocks until the service is finished running. Otherwise it requests a stop and returns but the service may still be running a final loop.

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RecentDeploymentsScheduler

Schedules deployments that were updated very recently This scheduler can run on a tight loop and ensure that runs from newly-created or updated deployments are rapidly scheduled without having to wait for the “main” scheduler to complete its loop. Note that scheduling is idempotent, so its ok for this scheduler to attempt to schedule the same deployments as the main scheduler. It’s purpose is to accelerate scheduling for any deployments that users are interacting with. Methods:

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run_once 

run_once(self, db: PrefectDBInterface) -> None
Schedule flow runs by:
  • Querying for deployments with active schedules
  • Generating the next set of flow runs based on each deployments schedule
  • Inserting all scheduled flow runs into the database
All inserted flow runs are committed to the database at the termination of the loop.

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service_settings 

service_settings(cls) -> ServicesBaseSetting

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service_settings 

service_settings(cls) -> ServicesBaseSetting