airflow/executors/local_executor.py

#
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# regarding copyright ownership.  The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License.  You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
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# Unless required by applicable law or agreed to in writing,
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# KIND, either express or implied.  See the License for the
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"""
LocalExecutor.

.. seealso::
    For more information on how the LocalExecutor works, take a look at the guide:
    :ref:`executor:LocalExecutor`
"""
from __future__ import annotations

import logging
import os
import subprocess
from abc import abstractmethod
from multiprocessing import Manager, Process
from multiprocessing.managers import SyncManager
from queue import Empty, Queue
from typing import TYPE_CHECKING, Any, Optional, Tuple

from setproctitle import getproctitle, setproctitle

from airflow import settings
from airflow.exceptions import AirflowException
from airflow.executors.base_executor import PARALLELISM, BaseExecutor
from airflow.utils.log.logging_mixin import LoggingMixin
from airflow.utils.state import State

if TYPE_CHECKING:
    from airflow.executors.base_executor import CommandType
    from airflow.models.taskinstance import TaskInstanceStateType
    from airflow.models.taskinstancekey import TaskInstanceKey

    # This is a work to be executed by a worker.
    # It can Key and Command - but it can also be None, None which is actually a
    # "Poison Pill" - worker seeing Poison Pill should take the pill and ... die instantly.
    ExecutorWorkType = Tuple[Optional[TaskInstanceKey], Optional[CommandType]]


class LocalWorkerBase(Process, LoggingMixin):
    """
    LocalWorkerBase implementation to run airflow commands.

    Executes the given command and puts the result into a result queue when done, terminating execution.

    :param result_queue: the queue to store result state
    """

    def __init__(self, result_queue: Queue[TaskInstanceStateType]):
        super().__init__(target=self.do_work)
        self.daemon: bool = True
        self.result_queue: Queue[TaskInstanceStateType] = result_queue

    def run(self):
        # We know we've just started a new process, so lets disconnect from the metadata db now
        settings.engine.pool.dispose()
        settings.engine.dispose()
        setproctitle("airflow worker -- LocalExecutor")
        return super().run()

    def execute_work(self, key: TaskInstanceKey, command: CommandType) -> None:
        """
        Executes command received and stores result state in queue.

        :param key: the key to identify the task instance
        :param command: the command to execute
        """
        if key is None:
            return

        self.log.info("%s running %s", self.__class__.__name__, command)
        setproctitle(f"airflow worker -- LocalExecutor: {command}")
        if settings.EXECUTE_TASKS_NEW_PYTHON_INTERPRETER:
            state = self._execute_work_in_subprocess(command)
        else:
            state = self._execute_work_in_fork(command)

        self.result_queue.put((key, state))
        # Remove the command since the worker is done executing the task
        setproctitle("airflow worker -- LocalExecutor")

    def _execute_work_in_subprocess(self, command: CommandType) -> str:
        try:
            subprocess.check_call(command, close_fds=True)
            return State.SUCCESS
        except subprocess.CalledProcessError as e:
            self.log.error("Failed to execute task %s.", str(e))
            return State.FAILED

    def _execute_work_in_fork(self, command: CommandType) -> str:
        pid = os.fork()
        if pid:
            # In parent, wait for the child
            pid, ret = os.waitpid(pid, 0)
            return State.SUCCESS if ret == 0 else State.FAILED

        from airflow.sentry import Sentry

        ret = 1
        try:
            import signal

            from airflow.cli.cli_parser import get_parser

            signal.signal(signal.SIGINT, signal.SIG_DFL)
            signal.signal(signal.SIGTERM, signal.SIG_DFL)
            signal.signal(signal.SIGUSR2, signal.SIG_DFL)

            parser = get_parser()
            # [1:] - remove "airflow" from the start of the command
            args = parser.parse_args(command[1:])
            args.shut_down_logging = False

            setproctitle(f"airflow task supervisor: {command}")

            args.func(args)
            ret = 0
            return State.SUCCESS
        except Exception as e:
            self.log.exception("Failed to execute task %s.", e)
            return State.FAILED
        finally:
            Sentry.flush()
            logging.shutdown()
            os._exit(ret)

    @abstractmethod
    def do_work(self):
        """Called in the subprocess and should then execute tasks."""
        raise NotImplementedError()


class LocalWorker(LocalWorkerBase):
    """
    Local worker that executes the task.

    :param result_queue: queue where results of the tasks are put.
    :param key: key identifying task instance
    :param command: Command to execute
    """

    def __init__(
        self, result_queue: Queue[TaskInstanceStateType], key: TaskInstanceKey, command: CommandType
    ):
        super().__init__(result_queue)
        self.key: TaskInstanceKey = key
        self.command: CommandType = command

    def do_work(self) -> None:
        self.execute_work(key=self.key, command=self.command)


class QueuedLocalWorker(LocalWorkerBase):
    """
    LocalWorker implementation that is waiting for tasks from a queue.

    Will continue executing commands as they become available in the queue.
    It will terminate execution once the poison token is found.

    :param task_queue: queue from which worker reads tasks
    :param result_queue: queue where worker puts results after finishing tasks
    """

    def __init__(self, task_queue: Queue[ExecutorWorkType], result_queue: Queue[TaskInstanceStateType]):
        super().__init__(result_queue=result_queue)
        self.task_queue = task_queue

    def do_work(self) -> None:
        while True:
            try:
                key, command = self.task_queue.get()
            except EOFError:
                self.log.info(
                    "Failed to read tasks from the task queue because the other "
                    "end has closed the connection. Terminating worker %s.",
                    self.name,
                )
                break
            try:
                if key is None or command is None:
                    # Received poison pill, no more tasks to run
                    break
                self.execute_work(key=key, command=command)
            finally:
                self.task_queue.task_done()


class LocalExecutor(BaseExecutor):
    """
    LocalExecutor executes tasks locally in parallel.
    It uses the multiprocessing Python library and queues to parallelize the execution
    of tasks.

    :param parallelism: how many parallel processes are run in the executor
    """

    is_local: bool = True
    supports_pickling: bool = False

    serve_logs: bool = True

    def __init__(self, parallelism: int = PARALLELISM):
        super().__init__(parallelism=parallelism)
        if self.parallelism < 0:
            raise AirflowException("parallelism must be bigger than or equal to 0")
        self.manager: SyncManager | None = None
        self.result_queue: Queue[TaskInstanceStateType] | None = None
        self.workers: list[QueuedLocalWorker] = []
        self.workers_used: int = 0
        self.workers_active: int = 0
        self.impl: None | (LocalExecutor.UnlimitedParallelism | LocalExecutor.LimitedParallelism) = None

    class UnlimitedParallelism:
        """
        Implement LocalExecutor with unlimited parallelism, starting one process per command executed.

        :param executor: the executor instance to implement.
        """

        def __init__(self, executor: LocalExecutor):
            self.executor: LocalExecutor = executor

        def start(self) -> None:
            """Starts the executor."""
            self.executor.workers_used = 0
            self.executor.workers_active = 0

        def execute_async(
            self,
            key: TaskInstanceKey,
            command: CommandType,
            queue: str | None = None,
            executor_config: Any | None = None,
        ) -> None:
            """
            Executes task asynchronously.

            :param key: the key to identify the task instance
            :param command: the command to execute
            :param queue: Name of the queue
            :param executor_config: configuration for the executor
            """
            if TYPE_CHECKING:
                assert self.executor.result_queue

            local_worker = LocalWorker(self.executor.result_queue, key=key, command=command)
            self.executor.workers_used += 1
            self.executor.workers_active += 1
            local_worker.start()

        def sync(self) -> None:
            """Sync will get called periodically by the heartbeat method."""
            if not self.executor.result_queue:
                raise AirflowException("Executor should be started first")
            while not self.executor.result_queue.empty():
                results = self.executor.result_queue.get()
                self.executor.change_state(*results)
                self.executor.workers_active -= 1

        def end(self) -> None:
            """Wait synchronously for the previously submitted job to complete."""
            while self.executor.workers_active > 0:
                self.executor.sync()

    class LimitedParallelism:
        """
        Implements LocalExecutor with limited parallelism.

        Uses a task queue to coordinate work distribution.

        :param executor: the executor instance to implement.
        """

        def __init__(self, executor: LocalExecutor):
            self.executor: LocalExecutor = executor
            self.queue: Queue[ExecutorWorkType] | None = None

        def start(self) -> None:
            """Starts limited parallelism implementation."""
            if TYPE_CHECKING:
                assert self.executor.manager
                assert self.executor.result_queue

            self.queue = self.executor.manager.Queue()
            self.executor.workers = [
                QueuedLocalWorker(self.queue, self.executor.result_queue)
                for _ in range(self.executor.parallelism)
            ]

            self.executor.workers_used = len(self.executor.workers)

            for worker in self.executor.workers:
                worker.start()

        def execute_async(
            self,
            key: TaskInstanceKey,
            command: CommandType,
            queue: str | None = None,
            executor_config: Any | None = None,
        ) -> None:
            """
            Executes task asynchronously.

            :param key: the key to identify the task instance
            :param command: the command to execute
            :param queue: name of the queue
            :param executor_config: configuration for the executor
            """
            if TYPE_CHECKING:
                assert self.queue

            self.queue.put((key, command))

        def sync(self):
            """Sync will get called periodically by the heartbeat method."""
            while True:
                try:
                    results = self.executor.result_queue.get_nowait()
                    try:
                        self.executor.change_state(*results)
                    finally:
                        self.executor.result_queue.task_done()
                except Empty:
                    break

        def end(self):
            """Ends the executor. Sends the poison pill to all workers."""
            for _ in self.executor.workers:
                self.queue.put((None, None))

            # Wait for commands to finish
            self.queue.join()
            self.executor.sync()

    def start(self) -> None:
        """Starts the executor."""
        old_proctitle = getproctitle()
        setproctitle("airflow executor -- LocalExecutor")
        self.manager = Manager()
        setproctitle(old_proctitle)
        self.result_queue = self.manager.Queue()
        self.workers = []
        self.workers_used = 0
        self.workers_active = 0
        self.impl = (
            LocalExecutor.UnlimitedParallelism(self)
            if self.parallelism == 0
            else LocalExecutor.LimitedParallelism(self)
        )

        self.impl.start()

    def execute_async(
        self,
        key: TaskInstanceKey,
        command: CommandType,
        queue: str | None = None,
        executor_config: Any | None = None,
    ) -> None:
        """Execute asynchronously."""
        if TYPE_CHECKING:
            assert self.impl

        self.validate_airflow_tasks_run_command(command)

        self.impl.execute_async(key=key, command=command, queue=queue, executor_config=executor_config)

    def sync(self) -> None:
        """Sync will get called periodically by the heartbeat method."""
        if TYPE_CHECKING:
            assert self.impl

        self.impl.sync()

    def end(self) -> None:
        """Ends the executor."""
        if TYPE_CHECKING:
            assert self.impl
            assert self.manager

        self.log.info(
            "Shutting down LocalExecutor"
            "; waiting for running tasks to finish.  Signal again if you don't want to wait."
        )
        self.impl.end()
        self.manager.shutdown()

    def terminate(self):
        """Terminate the executor is not doing anything."""