text: # Licensed to the Apache Software Foundation (ASF) under one
  # or more contributor license agreements.  See the NOTICE file
  # distributed with this work for additional information
  # 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
  #
  # Unless required by applicable law or agreed to in writing,
  # software distributed under the License is distributed on an
  # "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  # KIND, either express or implied.  See the License for the
  # specific language governing permissions and limitations
  # under the License.
  """Base executor - this is the base class for all the implemented executors."""
  import sys
  from collections import OrderedDict
  from typing import Any, Dict, List, Optional, Set, Tuple
  
  from airflow.configuration import conf
  from airflow.models.taskinstance import TaskInstance, TaskInstanceKey
  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')
  
  NOT_STARTED_MESSAGE = "The executor should be started first!"
  
  # Command to execute - list of strings
  # the first element is always "airflow".
  # It should be result of TaskInstance.generate_command method.q
  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]
  
  
  class BaseExecutor(LoggingMixin):
      """
      Class to derive in order to interface with executor-type systems
      like Celery, Kubernetes, Local, Sequential and the likes.
  
      :param parallelism: how many jobs should run at one time. Set to
          ``0`` for infinity
      """
  
      job_id: Optional[str] = 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] = {}
  
      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: Optional[str] = None,
      ):
          """Queues command to task"""
          # 只有任务不存在队列中同时也不在运行过程中，才将任务放到队列中
          if task_instance.key not in self.queued_tasks and task_instance.key not in self.running:
              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: Optional[str] = None,
          ignore_all_deps: bool = False,
          ignore_depends_on_past: bool = False,
          ignore_task_deps: bool = False,
          ignore_ti_state: bool = False,
          pool: Optional[str] = None,
          cfg_path: Optional[str] = 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,
              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."""
          # 如果没有设置parallelism的话，则open_slots为队列中任务的个数。否则的话为设置的parallelism - 正在运行的任务个数
          if not self.parallelism:
              open_slots = len(self.queued_tasks)
          else:
              open_slots = self.parallelism - len(self.running)
  
          # 统计正在运行的任务个数和在队列中的任务个数
          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', open_slots)
          Stats.gauge('executor.queued_tasks', num_queued_tasks)
          Stats.gauge('executor.running_tasks', num_running_tasks)
  
          # 触发任务
          self.trigger_tasks(open_slots)
  
          # Calling child class sync method
          self.log.debug("Calling the %s sync method", self.__class__)
          # 同步状态
          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(
              [(k, v) for k, v in self.queued_tasks.items()],  # pylint: disable=unnecessary-comprehension
              key=lambda x: x[1][1],
              reverse=True,
          )
  
      def trigger_tasks(self, open_slots: int) -> None:
          """
          Triggers tasks
  
          :param open_slots: Number of open slots
          """
          # 根据任务优先级对任务进行排序
          sorted_queue = self.order_queued_tasks_by_priority()
  
          for _ in range(min((open_slots, len(self.queued_tasks)))):
              # 从排序过的任务中获取第一个任务
              key, (command, _, queue, ti) = sorted_queue.pop(0)
              # 根据task key, 从任务队列中移除，并加入到正在运行的任务队列中。
              self.queued_tasks.pop(key)
              self.running.add(key)
              # 调用 execute_async() 来执行命令
              self.execute_async(key=key, command=command, queue=queue, executor_config=ti.executor_config)
  
      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]:
          """
          Returns 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: to dag_ids to return events for, if None returns all
          :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: Optional[str] = None,
          executor_config: Optional[Any] = 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 end(self) -> None:  # pragma: no cover
          """
          This method is called when the caller is done submitting job and
          wants to wait synchronously for the job submitted previously to be
          all done.
          """
          raise NotImplementedError()
  
      def terminate(self):
          """This method is called when the daemon receives a SIGTERM"""
          raise NotImplementedError()
  
      def try_adopt_task_instances(self, tis: List[TaskInstance]) -> List[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
          :rtype: list[airflow.models.TaskInstance]
          """
          # 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:
          """Check if the command to execute is airflow command"""
          if command[0:3] != ["airflow", "tasks", "run"]:
              raise ValueError('The command must start with ["airflow", "tasks", "run"].')
  
      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())),
          )
  