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"""Base class for all hooks"""
import os
import random
from typing import Iterable
from airflow.models import Connection
from airflow.exceptions import AirflowException
from airflow.utils.db import provide_session
from airflow.utils.log.logging_mixin import LoggingMixin
[docs]CONN_ENV_PREFIX = 'AIRFLOW_CONN_'
[docs]class BaseHook(LoggingMixin):
"""
Abstract base class for hooks, hooks are meant as an interface to
interact with external systems. MySqlHook, HiveHook, PigHook return
object that can handle the connection and interaction to specific
instances of these systems, and expose consistent methods to interact
with them.
"""
@classmethod
@provide_session
[docs] def _get_connections_from_db(cls, conn_id, session=None):
db = (
session.query(Connection)
.filter(Connection.conn_id == conn_id)
.all()
)
session.expunge_all()
if not db:
raise AirflowException(
"The conn_id `{0}` isn't defined".format(conn_id))
return db
@classmethod
[docs] def _get_connection_from_env(cls, conn_id):
environment_uri = os.environ.get(CONN_ENV_PREFIX + conn_id.upper())
conn = None
if environment_uri:
conn = Connection(conn_id=conn_id, uri=environment_uri)
return conn
@classmethod
[docs] def get_connections(cls, conn_id: str) -> Iterable[Connection]:
"""
Get all connections as an iterable.
:param conn_id connection id
:return array of connections
"""
conn = cls._get_connection_from_env(conn_id)
if conn:
conns = [conn]
else:
conns = cls._get_connections_from_db(conn_id)
return conns
@classmethod
[docs] def get_connection(cls, conn_id: str) -> Connection:
"""
Get random connection selected from all connections configured with this connection id.
:param conn_id connection id
:return connection
"""
conn = random.choice(list(cls.get_connections(conn_id)))
if conn.host:
log = LoggingMixin().log
log.info("Using connection to: %s", conn.debug_info())
return conn
@classmethod
[docs] def get_hook(cls, conn_id: str) -> "BaseHook":
"""
Returns default hook for this connection id.
:param conn_id: connection id
:return: default hook for this connection
"""
# TODO: set method return type to BaseHook class when on 3.7+.
# See https://stackoverflow.com/a/33533514/3066428
connection = cls.get_connection(conn_id)
return connection.get_hook()
[docs] def get_conn(self):
"""Returns connection for the hook."""
raise NotImplementedError()
[docs] def get_records(self, sql):
"""Returns records for the sql query (for hooks that support SQL)."""
# TODO: move it out from the base hook. It belongs to some common SQL hook most likely
raise NotImplementedError()
[docs] def get_pandas_df(self, sql):
"""Returns pandas dataframe for the sql query (for hooks that support SQL)."""
# TODO: move it out from the base hook. It belongs to some common SQL hook most likely
raise NotImplementedError()
[docs] def run(self, sql):
"""Runs SQL query (for hooks that support SQL)."""
# TODO: move it out from the base hook. It belongs to some common SQL hook most likely
raise NotImplementedError()