​
prefect.flow_engine

​
Functions

​
load_flow_run 

load_flow_run(flow_run_id: UUID) -> FlowRun

​
load_flow 

load_flow(flow_run: FlowRun) -> Flow[..., Any]

​
load_flow_and_flow_run 

load_flow_and_flow_run(flow_run_id: UUID) -> tuple[FlowRun, Flow[..., Any]]

​
run_flow_sync 

run_flow_sync(flow: Flow[P, R], flow_run: Optional[FlowRun] = None, parameters: Optional[Dict[str, Any]] = None, wait_for: Optional[Iterable[PrefectFuture[Any]]] = None, return_type: Literal['state', 'result'] = 'result', context: Optional[dict[str, Any]] = None) -> Union[R, State, None]

​
run_generator_flow_sync 

run_generator_flow_sync(flow: Flow[P, R], flow_run: Optional[FlowRun] = None, parameters: Optional[Dict[str, Any]] = None, wait_for: Optional[Iterable[PrefectFuture[Any]]] = None, return_type: Literal['state', 'result'] = 'result', context: Optional[dict[str, Any]] = None) -> Generator[R, None, None]

​
run_flow 

run_flow(flow: Flow[P, R], flow_run: Optional[FlowRun] = None, parameters: Optional[Dict[str, Any]] = None, wait_for: Optional[Iterable[PrefectFuture[R]]] = None, return_type: Literal['state', 'result'] = 'result', error_logger: Optional[logging.Logger] = None, context: Optional[dict[str, Any]] = None) -> R | State | None | Coroutine[Any, Any, R | State | None] | Generator[R, None, None] | AsyncGenerator[R, None]

​
run_flow_in_subprocess 

run_flow_in_subprocess(flow: 'Flow[..., Any]', flow_run: 'FlowRun | None' = None, parameters: dict[str, Any] | None = None, wait_for: Iterable[PrefectFuture[Any]] | None = None, context: dict[str, Any] | None = None) -> multiprocessing.context.SpawnProcess

Run a flow in a subprocess.

Note the result of the flow will only be accessible if the flow is configured to persist its result.

Args:

  • flow: The flow to run.
  • flow_run: The flow run object containing run metadata.
  • parameters: The parameters to use when invoking the flow.
  • wait_for: The futures to wait for before starting the flow.
  • context: A serialized context to hydrate before running the flow. If not provided, the current context will be used. A serialized context should be provided if this function is called in a separate memory space from the parent run (e.g. in a subprocess or on another machine).

Returns:

  • A multiprocessing.context.SpawnProcess representing the process that is running the flow.

​
Classes

​
FlowRunTimeoutError

Raised when a flow run exceeds its defined timeout.

​
BaseFlowRunEngine

Methods:

​
state 

state(self) -> State

​
is_running 

is_running(self) -> bool

​
is_pending 

is_pending(self) -> bool

​
cancel_all_tasks 

cancel_all_tasks(self) -> None

​
FlowRunEngine

Methods:

​
client 

client(self) -> SyncPrefectClient

​
begin_run 

begin_run(self) -> State

​
set_state 

set_state(self, state: State, force: bool = False) -> State

​
result 

result(self, raise_on_failure: bool = True) -> 'Union[R, State, None]'

​
handle_success 

handle_success(self, result: R) -> R

​
handle_exception 

handle_exception(self, exc: Exception, msg: Optional[str] = None, result_store: Optional[ResultStore] = None) -> State

​
handle_timeout 

handle_timeout(self, exc: TimeoutError) -> None

​
handle_crash 

handle_crash(self, exc: BaseException) -> None

​
load_subflow_run 

load_subflow_run(self, parent_task_run: TaskRun, client: SyncPrefectClient, context: FlowRunContext) -> Union[FlowRun, None]

This method attempts to load an existing flow run for a subflow task run, if appropriate.

If the parent task run is in a final but not COMPLETED state, and not being rerun, then we attempt to load an existing flow run instead of creating a new one. This will prevent the engine from running the subflow again.

If no existing flow run is found, or if the subflow should be rerun, then no flow run is returned.

​
create_flow_run 

create_flow_run(self, client: SyncPrefectClient) -> FlowRun

​
call_hooks 

call_hooks(self, state: Optional[State] = None) -> None

​
setup_run_context 

setup_run_context(self, client: Optional[SyncPrefectClient] = None)

​
initialize_run 

initialize_run(self)

Enters a client context and creates a flow run if needed.

​
start 

start(self) -> Generator[None, None, None]

​
run_context 

run_context(self)

​
call_flow_fn 

call_flow_fn(self) -> Union[R, Coroutine[Any, Any, R]]

Convenience method to call the flow function. Returns a coroutine if the flow is async.

​
AsyncFlowRunEngine

Async version of the flow run engine.

NOTE: This has not been fully asyncified yet which may lead to async flows not being fully asyncified.

Methods:

​
client 

client(self) -> PrefectClient