Source code for airflow.models.serialized_dag

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"""Serialized DAG table in database."""

import hashlib
import logging
from datetime import timedelta
from typing import Any, Optional

import sqlalchemy_jsonfield
from sqlalchemy import BigInteger, Column, Index, String, and_
from sqlalchemy.orm import Session  # noqa: F401
from sqlalchemy.sql import exists

from airflow.models.base import ID_LEN, Base
from airflow.models.dag import DAG
from airflow.models.dagcode import DagCode
from airflow.serialization.serialized_objects import SerializedDAG
from airflow.settings import json
from airflow.utils import db, timezone
from airflow.utils.sqlalchemy import UtcDateTime

[docs]class SerializedDagModel(Base): """A table for serialized DAGs. serialized_dag table is a snapshot of DAG files synchronized by scheduler. This feature is controlled by: * ``[core] store_serialized_dags = True``: enable this feature * ``[core] min_serialized_dag_update_interval = 30`` (s): serialized DAGs are updated in DB when a file gets processed by scheduler, to reduce DB write rate, there is a minimal interval of updating serialized DAGs. * ``[scheduler] dag_dir_list_interval = 300`` (s): interval of deleting serialized DAGs in DB when the files are deleted, suggest to use a smaller interval such as 60 It is used by webserver to load dags when ``store_serialized_dags=True``. Because reading from database is lightweight compared to importing from files, it solves the webserver scalability issue. """
[docs] __tablename__ = 'serialized_dag'
[docs] dag_id = Column(String(ID_LEN), primary_key=True)
[docs] fileloc = Column(String(2000), nullable=False)
# The max length of fileloc exceeds the limit of indexing.
[docs] fileloc_hash = Column(BigInteger, nullable=False)
[docs] data = Column(sqlalchemy_jsonfield.JSONField(json=json), nullable=False)
[docs] last_updated = Column(UtcDateTime, nullable=False)
[docs] dag_hash = Column(String(32), nullable=False)
[docs] __table_args__ = ( Index('idx_fileloc_hash', fileloc_hash, unique=False),
) def __init__(self, dag): self.dag_id = dag.dag_id self.fileloc = dag.full_filepath self.fileloc_hash = DagCode.dag_fileloc_hash(self.fileloc) = SerializedDAG.to_dict(dag) self.last_updated = timezone.utcnow() self.dag_hash = hashlib.md5(json.dumps(, sort_keys=True).encode("utf-8")).hexdigest()
[docs] def __repr__(self): return "<SerializedDag: {}>".format(self.dag_id)
@classmethod @db.provide_session
[docs] def write_dag(cls, dag, # type: DAG min_update_interval=None, # type: Optional[int] session=None): """Serializes a DAG and writes it into database. If the record already exists, it checks if the Serialized DAG changed or not. If it is changed, it updates the record, ignores otherwise. :param dag: a DAG to be written into database :param min_update_interval: minimal interval in seconds to update serialized DAG :param session: ORM Session """ # Checks if (Current Time - Time when the DAG was written to DB) < min_update_interval # If Yes, does nothing # If No or the DAG does not exists, updates / writes Serialized DAG to DB if min_update_interval is not None: if session.query(exists().where( and_(cls.dag_id == dag.dag_id, (timezone.utcnow() - timedelta(seconds=min_update_interval)) < cls.last_updated)) ).scalar(): return log.debug("Checking if DAG (%s) changed", dag.dag_id) new_serialized_dag = cls(dag) serialized_dag_hash_from_db = session.query( cls.dag_hash).filter(cls.dag_id == dag.dag_id).scalar() if serialized_dag_hash_from_db == new_serialized_dag.dag_hash: log.debug("Serialized DAG (%s) is unchanged. Skipping writing to DB", dag.dag_id) return log.debug("Writing Serialized DAG: %s to the DB", dag.dag_id) session.merge(new_serialized_dag) log.debug("DAG: %s written to the DB", dag.dag_id)
@classmethod @db.provide_session
[docs] def read_all_dags(cls, session=None): """Reads all DAGs in serialized_dag table. :param session: ORM Session :type session: Session :returns: a dict of DAGs read from database """ serialized_dags = session.query(cls) dags = {} for row in serialized_dags: log.debug("Deserializing DAG: %s", row.dag_id) dag = row.dag # Sanity check. if dag.dag_id == row.dag_id: dags[row.dag_id] = dag else: log.warning( "dag_id Mismatch in DB: Row with dag_id '%s' has Serialised DAG " "with '%s' dag_id", row.dag_id, dag.dag_id) return dags
[docs] def dag(self): """The DAG deserialized from the ``data`` column""" if isinstance(, dict): dag = SerializedDAG.from_dict( # type: Any else: # noinspection PyTypeChecker dag = SerializedDAG.from_json( return dag
@classmethod @db.provide_session
[docs] def remove_dag(cls, dag_id, session=None): """Deletes a DAG with given dag_id. :param dag_id: dag_id to be deleted :type dag_id: str :param session: ORM Session :type session: Session """ session.execute(cls.__table__.delete().where(cls.dag_id == dag_id))
@classmethod @db.provide_session
[docs] def remove_deleted_dags(cls, alive_dag_filelocs, session=None): """Deletes DAGs not included in alive_dag_filelocs. :param alive_dag_filelocs: file paths of alive DAGs :type alive_dag_filelocs: list :param session: ORM Session :type session: Session """ alive_fileloc_hashes = [ DagCode.dag_fileloc_hash(fileloc) for fileloc in alive_dag_filelocs] log.debug("Deleting Serialized DAGs (for which DAG files are deleted) " "from %s table ", cls.__tablename__) session.execute( cls.__table__.delete().where( and_(cls.fileloc_hash.notin_(alive_fileloc_hashes), cls.fileloc.notin_(alive_dag_filelocs))))
@classmethod @db.provide_session
[docs] def has_dag(cls, dag_id, session=None): """Checks a DAG exist in serialized_dag table. :param dag_id: the DAG to check :type dag_id: str :param session: ORM Session :type session: Session :rtype: bool """ return session.query(exists().where(cls.dag_id == dag_id)).scalar()
@classmethod @db.provide_session
[docs] def get(cls, dag_id, session=None): """ Get the SerializedDAG for the given dag ID. It will cope with being passed the ID of a subdag by looking up the root dag_id from the DAG table. :param dag_id: the DAG to fetch :param session: ORM Session :type session: Session """ from airflow.models.dag import DagModel row = session.query(cls).filter(cls.dag_id == dag_id).one_or_none() if row: return row # If we didn't find a matching DAG id then ask the DAG table to find # out the root dag root_dag_id = session.query( DagModel.root_dag_id).filter(DagModel.dag_id == dag_id).scalar() return session.query(cls).filter(cls.dag_id == root_dag_id).one_or_none()
@classmethod @db.provide_session
[docs] def get_last_updated_datetime(cls, dag_id, session): """ Get the date when the Serialized DAG associated to DAG was last updated in serialized_dag table :param dag_id: DAG ID :type dag_id: str :param session: ORM Session :type session: Session """ return session.query(cls.last_updated).filter(cls.dag_id == dag_id).scalar()

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