airflow.models.serialized_dag

Serialized DAG table in database.

Module Contents

airflow.models.serialized_dag.log[source]
class airflow.models.serialized_dag.SerializedDagModel(dag)[source]

Bases: airflow.models.base.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.

__tablename__ = serialized_dag[source]
dag_id[source]
fileloc[source]
fileloc_hash[source]
data[source]
last_updated[source]
dag_hash[source]
__table_args__[source]
dag[source]

The DAG deserialized from the data column

__repr__(self)[source]
classmethod write_dag(cls, dag, min_update_interval=None, session=None)[source]

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.

Parameters
  • dag – a DAG to be written into database

  • min_update_interval – minimal interval in seconds to update serialized DAG

  • session – ORM Session

classmethod read_all_dags(cls, session=None)[source]

Reads all DAGs in serialized_dag table.

Parameters

session (Session) – ORM Session

Returns

a dict of DAGs read from database

classmethod remove_dag(cls, dag_id, session=None)[source]

Deletes a DAG with given dag_id.

Parameters
  • dag_id (str) – dag_id to be deleted

  • session (Session) – ORM Session

classmethod remove_deleted_dags(cls, alive_dag_filelocs, session=None)[source]

Deletes DAGs not included in alive_dag_filelocs.

Parameters
  • alive_dag_filelocs (list) – file paths of alive DAGs

  • session (Session) – ORM Session

classmethod has_dag(cls, dag_id, session=None)[source]

Checks a DAG exist in serialized_dag table.

Parameters
  • dag_id (str) – the DAG to check

  • session (Session) – ORM Session

Return type

bool

classmethod get(cls, dag_id, session=None)[source]

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.

Parameters
  • dag_id – the DAG to fetch

  • session (Session) – ORM Session

classmethod get_last_updated_datetime(cls, dag_id, session)[source]

Get the date when the Serialized DAG associated to DAG was last updated in serialized_dag table

Parameters
  • dag_id (str) – DAG ID

  • session (Session) – ORM Session