prefect.cli.worker

start(worker_name=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=typer.Option(..., '-p', '--pool', help='The work pool the started worker should poll.', prompt=True), work_queues=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=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=SettingsOption(PREFECT_WORKER_PREFETCH_SECONDS, help='Number of seconds to look into the future for scheduled flow runs.'), run_once=typer.Option(False, help='Only run worker polling once. By default, the worker runs forever.'), limit=typer.Option(None, '-l', '--limit', help='Maximum number of flow runs to start simultaneously.'), with_healthcheck=typer.Option(False, help='Start a healthcheck server for the worker.'), install_policy=typer.Option(InstallPolicy.PROMPT.value, '--install-policy', help='Install policy to use workers from Prefect integration packages.', case_sensitive=False), base_job_template=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.')) async

Start a worker process to poll a work pool for flow runs.

Source code in src/prefect/cli/worker.py

@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",
        )

    is_queues_paused = await _check_work_queues_paused(
        work_pool_name,
        work_queues,
    )
    if is_queues_paused:
        queue_scope = (
            "All work queues" if not work_queues else "Specified work queue(s)"
        )
        app.console.print(
            (
                f"{queue_scope} in the work pool {work_pool_name!r} are currently"
                " paused. This worker will not execute any flow runs until the work"
                " queues are 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)

    worker = worker_cls(
        name=worker_name,
        work_pool_name=work_pool_name,
        work_queues=work_queues,
        limit=limit,
        prefetch_seconds=prefetch_seconds,
        heartbeat_interval_seconds=int(PREFECT_WORKER_HEARTBEAT_SECONDS.value()),
        base_job_template=template_contents,
    )
    try:
        await worker.start(
            run_once=run_once,
            with_healthcheck=with_healthcheck,
            printer=app.console.print,
        )
    except asyncio.CancelledError:
        app.console.print(f"Worker {worker.name!r} stopped!", style="yellow")