airflow/executors/base_executor.py

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"""Base executor - this is the base class for all the implemented executors."""
from __future__ import annotations

import logging
import sys
import warnings
from collections import OrderedDict, defaultdict
from dataclasses import dataclass, field
from datetime import datetime
from typing import TYPE_CHECKING, Any, List, Optional, Sequence, Tuple

import pendulum

from airflow.configuration import conf
from airflow.exceptions import RemovedInAirflow3Warning
from airflow.stats import Stats
from airflow.utils.log.logging_mixin import LoggingMixin
from airflow.utils.state import State

PARALLELISM: int = conf.getint("core", "PARALLELISM")

if TYPE_CHECKING:
    from airflow.callbacks.base_callback_sink import BaseCallbackSink
    from airflow.callbacks.callback_requests import CallbackRequest
    from airflow.models.taskinstance import TaskInstance
    from airflow.models.taskinstancekey import TaskInstanceKey

    # Command to execute - list of strings
    # the first element is always "airflow".
    # It should be result of TaskInstance.generate_command method.
    CommandType = List[str]

    # Task that is queued. It contains all the information that is
    # needed to run the task.
    #
    # Tuple of: command, priority, queue name, TaskInstance
    QueuedTaskInstanceType = Tuple[CommandType, int, Optional[str], TaskInstance]

    # Event_buffer dict value type
    # Tuple of: state, info
    EventBufferValueType = Tuple[Optional[str], Any]

    # Task tuple to send to be executed
    TaskTuple = Tuple[TaskInstanceKey, CommandType, Optional[str], Optional[Any]]

log = logging.getLogger(__name__)


@dataclass
class RunningRetryAttemptType:
    """
    For keeping track of attempts to queue again when task still apparently running.

    We don't want to slow down the loop, so we don't block, but we allow it to be
    re-checked for at least MIN_SECONDS seconds.
    """

    MIN_SECONDS = 10
    total_tries: int = field(default=0, init=False)
    tries_after_min: int = field(default=0, init=False)
    first_attempt_time: datetime = field(default_factory=lambda: pendulum.now("UTC"), init=False)

    @property
    def elapsed(self):
        """Seconds since first attempt."""
        return (pendulum.now("UTC") - self.first_attempt_time).total_seconds()

    def can_try_again(self):
        """
        If there has been at least one try greater than MIN_SECONDS after first attempt,
        then return False.  Otherwise, return True.
        """
        if self.tries_after_min > 0:
            return False

        self.total_tries += 1

        elapsed = self.elapsed
        if elapsed > self.MIN_SECONDS:
            self.tries_after_min += 1
        log.debug("elapsed=%s tries=%s", elapsed, self.total_tries)
        return True


class BaseExecutor(LoggingMixin):
    """
    Class to derive in order to implement concrete executors.
    Such as, Celery, Kubernetes, Local, Sequential and the likes.

    :param parallelism: how many jobs should run at one time. Set to
        ``0`` for infinity.
    """

    supports_ad_hoc_ti_run: bool = False
    supports_pickling: bool = True
    supports_sentry: bool = False

    is_local: bool = False
    is_single_threaded: bool = False
    is_production: bool = True

    change_sensor_mode_to_reschedule: bool = False
    serve_logs: bool = False

    job_id: None | int | str = None
    callback_sink: BaseCallbackSink | None = None

    def __init__(self, parallelism: int = PARALLELISM):
        super().__init__()
        self.parallelism: int = parallelism
        self.queued_tasks: OrderedDict[TaskInstanceKey, QueuedTaskInstanceType] = OrderedDict()
        self.running: set[TaskInstanceKey] = set()
        self.event_buffer: dict[TaskInstanceKey, EventBufferValueType] = {}
        self.attempts: dict[TaskInstanceKey, RunningRetryAttemptType] = defaultdict(RunningRetryAttemptType)

    def __repr__(self):
        return f"{self.__class__.__name__}(parallelism={self.parallelism})"

    def start(self):  # pragma: no cover
        """Executors may need to get things started."""

    def queue_command(
        self,
        task_instance: TaskInstance,
        command: CommandType,
        priority: int = 1,
        queue: str | None = None,
    ):
        """Queues command to task."""
        if task_instance.key not in self.queued_tasks:
            self.log.info("Adding to queue: %s", command)
            self.queued_tasks[task_instance.key] = (command, priority, queue, task_instance)
        else:
            self.log.error("could not queue task %s", task_instance.key)

    def queue_task_instance(
        self,
        task_instance: TaskInstance,
        mark_success: bool = False,
        pickle_id: int | None = None,
        ignore_all_deps: bool = False,
        ignore_depends_on_past: bool = False,
        wait_for_past_depends_before_skipping: bool = False,
        ignore_task_deps: bool = False,
        ignore_ti_state: bool = False,
        pool: str | None = None,
        cfg_path: str | None = None,
    ) -> None:
        """Queues task instance."""
        pool = pool or task_instance.pool

        # TODO (edgarRd): AIRFLOW-1985:
        # cfg_path is needed to propagate the config values if using impersonation
        # (run_as_user), given that there are different code paths running tasks.
        # For a long term solution we need to address AIRFLOW-1986
        command_list_to_run = task_instance.command_as_list(
            local=True,
            mark_success=mark_success,
            ignore_all_deps=ignore_all_deps,
            ignore_depends_on_past=ignore_depends_on_past,
            wait_for_past_depends_before_skipping=wait_for_past_depends_before_skipping,
            ignore_task_deps=ignore_task_deps,
            ignore_ti_state=ignore_ti_state,
            pool=pool,
            pickle_id=pickle_id,
            cfg_path=cfg_path,
        )
        self.log.debug("created command %s", command_list_to_run)
        self.queue_command(
            task_instance,
            command_list_to_run,
            priority=task_instance.task.priority_weight_total,
            queue=task_instance.task.queue,
        )

    def has_task(self, task_instance: TaskInstance) -> bool:
        """
        Checks if a task is either queued or running in this executor.

        :param task_instance: TaskInstance
        :return: True if the task is known to this executor
        """
        return task_instance.key in self.queued_tasks or task_instance.key in self.running

    def sync(self) -> None:
        """
        Sync will get called periodically by the heartbeat method.
        Executors should override this to perform gather statuses.
        """

    def heartbeat(self) -> None:
        """Heartbeat sent to trigger new jobs."""
        if not self.parallelism:
            open_slots = len(self.queued_tasks)
        else:
            open_slots = self.parallelism - len(self.running)

        num_running_tasks = len(self.running)
        num_queued_tasks = len(self.queued_tasks)

        self.log.debug("%s running task instances", num_running_tasks)
        self.log.debug("%s in queue", num_queued_tasks)
        self.log.debug("%s open slots", open_slots)

        Stats.gauge(
            "executor.open_slots", value=open_slots, tags={"status": "open", "name": self.__class__.__name__}
        )
        Stats.gauge(
            "executor.queued_tasks",
            value=num_queued_tasks,
            tags={"status": "queued", "name": self.__class__.__name__},
        )
        Stats.gauge(
            "executor.running_tasks",
            value=num_running_tasks,
            tags={"status": "running", "name": self.__class__.__name__},
        )

        self.trigger_tasks(open_slots)

        # Calling child class sync method
        self.log.debug("Calling the %s sync method", self.__class__)
        self.sync()

    def order_queued_tasks_by_priority(self) -> list[tuple[TaskInstanceKey, QueuedTaskInstanceType]]:
        """
        Orders the queued tasks by priority.

        :return: List of tuples from the queued_tasks according to the priority.
        """
        return sorted(
            self.queued_tasks.items(),
            key=lambda x: x[1][1],
            reverse=True,
        )

    def trigger_tasks(self, open_slots: int) -> None:
        """
        Initiates async execution of the queued tasks, up to the number of available slots.

        :param open_slots: Number of open slots
        """
        sorted_queue = self.order_queued_tasks_by_priority()
        task_tuples = []

        for _ in range(min((open_slots, len(self.queued_tasks)))):
            key, (command, _, queue, ti) = sorted_queue.pop(0)

            # If a task makes it here but is still understood by the executor
            # to be running, it generally means that the task has been killed
            # externally and not yet been marked as failed.
            #
            # However, when a task is deferred, there is also a possibility of
            # a race condition where a task might be scheduled again during
            # trigger processing, even before we are able to register that the
            # deferred task has completed. In this case and for this reason,
            # we make a small number of attempts to see if the task has been
            # removed from the running set in the meantime.
            if key in self.running:
                attempt = self.attempts[key]
                if attempt.can_try_again():
                    # if it hasn't been much time since first check, let it be checked again next time
                    self.log.info("queued but still running; attempt=%s task=%s", attempt.total_tries, key)
                    continue
                # Otherwise, we give up and remove the task from the queue.
                self.log.error(
                    "could not queue task %s (still running after %d attempts)", key, attempt.total_tries
                )
                del self.attempts[key]
                del self.queued_tasks[key]
            else:
                if key in self.attempts:
                    del self.attempts[key]
                task_tuples.append((key, command, queue, ti.executor_config))

        if task_tuples:
            self._process_tasks(task_tuples)

    def _process_tasks(self, task_tuples: list[TaskTuple]) -> None:
        for key, command, queue, executor_config in task_tuples:
            del self.queued_tasks[key]
            self.execute_async(key=key, command=command, queue=queue, executor_config=executor_config)
            self.running.add(key)

    def change_state(self, key: TaskInstanceKey, state: str, info=None) -> None:
        """
        Changes state of the task.

        :param info: Executor information for the task instance
        :param key: Unique key for the task instance
        :param state: State to set for the task.
        """
        self.log.debug("Changing state: %s", key)
        try:
            self.running.remove(key)
        except KeyError:
            self.log.debug("Could not find key: %s", str(key))
        self.event_buffer[key] = state, info

    def fail(self, key: TaskInstanceKey, info=None) -> None:
        """
        Set fail state for the event.

        :param info: Executor information for the task instance
        :param key: Unique key for the task instance
        """
        self.change_state(key, State.FAILED, info)

    def success(self, key: TaskInstanceKey, info=None) -> None:
        """
        Set success state for the event.

        :param info: Executor information for the task instance
        :param key: Unique key for the task instance
        """
        self.change_state(key, State.SUCCESS, info)

    def get_event_buffer(self, dag_ids=None) -> dict[TaskInstanceKey, EventBufferValueType]:
        """
        Return and flush the event buffer.

        In case dag_ids is specified it will only return and flush events
        for the given dag_ids. Otherwise, it returns and flushes all events.

        :param dag_ids: the dag_ids to return events for; returns all if given ``None``.
        :return: a dict of events
        """
        cleared_events: dict[TaskInstanceKey, EventBufferValueType] = {}
        if dag_ids is None:
            cleared_events = self.event_buffer
            self.event_buffer = {}
        else:
            for ti_key in list(self.event_buffer.keys()):
                if ti_key.dag_id in dag_ids:
                    cleared_events[ti_key] = self.event_buffer.pop(ti_key)

        return cleared_events

    def execute_async(
        self,
        key: TaskInstanceKey,
        command: CommandType,
        queue: str | None = None,
        executor_config: Any | None = None,
    ) -> None:  # pragma: no cover
        """
        This method will execute the command asynchronously.

        :param key: Unique key for the task instance
        :param command: Command to run
        :param queue: name of the queue
        :param executor_config: Configuration passed to the executor.
        """
        raise NotImplementedError()

    def get_task_log(self, ti: TaskInstance, try_number: int) -> tuple[list[str], list[str]]:
        """
        This method can be implemented by any child class to return the task logs.

        :param ti: A TaskInstance object
        :param try_number: current try_number to read log from
        :return: tuple of logs and messages
        """
        return [], []

    def end(self) -> None:  # pragma: no cover
        """Wait synchronously for the previously submitted job to complete."""
        raise NotImplementedError()

    def terminate(self):
        """This method is called when the daemon receives a SIGTERM."""
        raise NotImplementedError()

    def cleanup_stuck_queued_tasks(self, tis: list[TaskInstance]) -> list[str]:  # pragma: no cover
        """
        Handle remnants of tasks that were failed because they were stuck in queued.
        Tasks can get stuck in queued. If such a task is detected, it will be marked
        as `UP_FOR_RETRY` if the task instance has remaining retries or marked as `FAILED`
        if it doesn't.

        :param tis: List of Task Instances to clean up
        :return: List of readable task instances for a warning message
        """
        raise NotImplementedError()

    def try_adopt_task_instances(self, tis: Sequence[TaskInstance]) -> Sequence[TaskInstance]:
        """
        Try to adopt running task instances that have been abandoned by a SchedulerJob dying.

        Anything that is not adopted will be cleared by the scheduler (and then become eligible for
        re-scheduling)

        :return: any TaskInstances that were unable to be adopted
        """
        # By default, assume Executors cannot adopt tasks, so just say we failed to adopt anything.
        # Subclasses can do better!
        return tis

    @property
    def slots_available(self):
        """Number of new tasks this executor instance can accept."""
        if self.parallelism:
            return self.parallelism - len(self.running) - len(self.queued_tasks)
        else:
            return sys.maxsize

    @staticmethod
    def validate_command(command: list[str]) -> None:
        """
        Back-compat method to Check if the command to execute is airflow command.

        :param command: command to check
        """
        warnings.warn(
            """
            The `validate_command` method is deprecated. Please use ``validate_airflow_tasks_run_command``
            """,
            RemovedInAirflow3Warning,
            stacklevel=2,
        )
        BaseExecutor.validate_airflow_tasks_run_command(command)

    @staticmethod
    def validate_airflow_tasks_run_command(command: list[str]) -> tuple[str | None, str | None]:
        """
        Check if the command to execute is airflow command.

        Returns tuple (dag_id,task_id) retrieved from the command (replaced with None values if missing)
        """
        if command[0:3] != ["airflow", "tasks", "run"]:
            raise ValueError('The command must start with ["airflow", "tasks", "run"].')
        if len(command) > 3 and "--help" not in command:
            dag_id: str | None = None
            task_id: str | None = None
            for arg in command[3:]:
                if not arg.startswith("--"):
                    if dag_id is None:
                        dag_id = arg
                    else:
                        task_id = arg
                        break
            return dag_id, task_id
        return None, None

    def debug_dump(self):
        """Called in response to SIGUSR2 by the scheduler."""
        self.log.info(
            "executor.queued (%d)\n\t%s",
            len(self.queued_tasks),
            "\n\t".join(map(repr, self.queued_tasks.items())),
        )
        self.log.info("executor.running (%d)\n\t%s", len(self.running), "\n\t".join(map(repr, self.running)))
        self.log.info(
            "executor.event_buffer (%d)\n\t%s",
            len(self.event_buffer),
            "\n\t".join(map(repr, self.event_buffer.items())),
        )

    def send_callback(self, request: CallbackRequest) -> None:
        """Sends callback for execution.

        Provides a default implementation which sends the callback to the `callback_sink` object.

        :param request: Callback request to be executed.
        """
        if not self.callback_sink:
            raise ValueError("Callback sink is not ready.")
        self.callback_sink.send(request)