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213 | @worker_app.command()
async def start(
worker_name: str = typer.Option(
None,
"-n",
"--name",
help=(
"The name to give to the started worker. If not provided, a unique name"
" will be generated."
),
),
work_pool_name: str = typer.Option(
...,
"-p",
"--pool",
help="The work pool the started worker should poll.",
prompt=True,
),
work_queues: List[str] = typer.Option(
None,
"-q",
"--work-queue",
help=(
"One or more work queue names for the worker to pull from. If not provided,"
" the worker will pull from all work queues in the work pool."
),
),
worker_type: Optional[str] = typer.Option(
None,
"-t",
"--type",
help=(
"The type of worker to start. If not provided, the worker type will be"
" inferred from the work pool."
),
),
prefetch_seconds: int = SettingsOption(
PREFECT_WORKER_PREFETCH_SECONDS,
help="Number of seconds to look into the future for scheduled flow runs.",
),
run_once: bool = typer.Option(
False, help="Only run worker polling once. By default, the worker runs forever."
),
limit: int = typer.Option(
None,
"-l",
"--limit",
help="Maximum number of flow runs to start simultaneously.",
),
with_healthcheck: bool = typer.Option(
False, help="Start a healthcheck server for the worker."
),
install_policy: InstallPolicy = typer.Option(
InstallPolicy.PROMPT.value,
"--install-policy",
help="Install policy to use workers from Prefect integration packages.",
case_sensitive=False,
),
base_job_template: typer.FileText = typer.Option(
None,
"--base-job-template",
help=(
"The path to a JSON file containing the base job template to use. If"
" unspecified, Prefect will use the default base job template for the given"
" worker type. If the work pool already exists, this will be ignored."
),
),
):
"""
Start a worker process to poll a work pool for flow runs.
"""
is_paused = await _check_work_pool_paused(work_pool_name)
if is_paused:
app.console.print(
(
f"The work pool {work_pool_name!r} is currently paused. This worker"
" will not execute any flow runs until the work pool is unpaused."
),
style="yellow",
)
worker_cls = await _get_worker_class(worker_type, work_pool_name, install_policy)
if worker_cls is None:
exit_with_error(
"Unable to start worker. Please ensure you have the necessary dependencies"
" installed to run your desired worker type."
)
worker_process_id = os.getpid()
setup_signal_handlers_worker(
worker_process_id, f"the {worker_type} worker", app.console.print
)
template_contents = None
if base_job_template is not None:
template_contents = json.load(fp=base_job_template)
async with worker_cls(
name=worker_name,
work_pool_name=work_pool_name,
work_queues=work_queues,
limit=limit,
prefetch_seconds=prefetch_seconds,
heartbeat_interval_seconds=PREFECT_WORKER_HEARTBEAT_SECONDS.value(),
base_job_template=template_contents,
) as worker:
app.console.print(f"Worker {worker.name!r} started!", style="green")
async with anyio.create_task_group() as tg:
# wait for an initial heartbeat to configure the worker
await worker.sync_with_backend()
# schedule the scheduled flow run polling loop
tg.start_soon(
partial(
critical_service_loop,
workload=worker.get_and_submit_flow_runs,
interval=PREFECT_WORKER_QUERY_SECONDS.value(),
run_once=run_once,
printer=app.console.print,
jitter_range=0.3,
backoff=4, # Up to ~1 minute interval during backoff
)
)
# schedule the sync loop
tg.start_soon(
partial(
critical_service_loop,
workload=worker.sync_with_backend,
interval=worker.heartbeat_interval_seconds,
run_once=run_once,
printer=app.console.print,
jitter_range=0.3,
backoff=4,
)
)
tg.start_soon(
partial(
critical_service_loop,
workload=worker.check_for_cancelled_flow_runs,
interval=PREFECT_WORKER_QUERY_SECONDS.value() * 2,
run_once=run_once,
printer=app.console.print,
jitter_range=0.3,
backoff=4,
)
)
started_event = await worker._emit_worker_started_event()
# if --with-healthcheck was passed, start the healthcheck server
if with_healthcheck:
# we'll start the ASGI server in a separate thread so that
# uvicorn does not block the main thread
server_thread = threading.Thread(
name="healthcheck-server-thread",
target=partial(
start_healthcheck_server,
worker=worker,
query_interval_seconds=PREFECT_WORKER_QUERY_SECONDS.value(),
),
daemon=True,
)
server_thread.start()
await worker._emit_worker_stopped_event(started_event)
app.console.print(f"Worker {worker.name!r} stopped!")
|