airflow/jobs/base_job_runner.py

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from __future__ import annotations

from typing import TYPE_CHECKING, Generic, TypeVar

from airflow.utils.session import NEW_SESSION, provide_session

if TYPE_CHECKING:
    from sqlalchemy.orm import Session

    from airflow.jobs.job import Job
    from airflow.serialization.pydantic.job import JobPydantic

J = TypeVar("J", "Job", "JobPydantic", "Job | JobPydantic")


class BaseJobRunner(Generic[J]):
    """Abstract class for job runners to derive from."""

    job_type = "undefined"

    def __init__(self, job: J) -> None:
        if job.job_type and job.job_type != self.job_type:
            raise Exception(
                f"The job is already assigned a different job_type: {job.job_type}."
                f"This is a bug and should be reported."
            )
        job.job_type = self.job_type
        self.job: J = job

    def _execute(self) -> int | None:
        """
        Executes the logic connected to the runner. This method should be
        overridden by subclasses.

        :meta private:
        :return: return code if available, otherwise None
        """
        raise NotImplementedError()

    @provide_session
    def heartbeat_callback(self, session: Session = NEW_SESSION) -> None:
        """Callback that is called during heartbeat. This method can be overwritten by the runners."""

    @classmethod
    @provide_session
    def most_recent_job(cls, session: Session = NEW_SESSION) -> Job | None:
        """Returns the most recent job of this type, if any, based on last heartbeat received."""
        from airflow.jobs.job import most_recent_job

        return most_recent_job(cls.job_type, session=session)