airflow plugins not getting picked up correctly - airflow

Question

We are using Apache 1.9.0. I have written a snowflake hook plugin. I have placed the hook in the $AIRFLOW_HOME/plugins directory.
$AIRFLOW_HOME
+--plugins
+--snowflake_hook2.py
snowflake_hook2.py
# This is the base class for a plugin
from airflow.plugins_manager import AirflowPlugin
# This is necessary to expose the plugin in the Web interface
from flask import Blueprint
from flask_admin import BaseView, expose
from flask_admin.base import MenuLink
# This is the base hook for connecting to a database
from airflow.hooks.dbapi_hook import DbApiHook
# This is the snowflake provided Connector
import snowflake.connector
# This is the default python logging package
import logging
class SnowflakeHook2(DbApiHook):
"""
Airflow Hook to communicate with Snowflake
This is implemented as a Plugin
"""
def __init__(self, connname_in='snowflake_default', db_in='default', wh_in='default', schema_in='default'):
logging.info('# Connecting to {0}'.format(connname_in))
self.conn_name_attr = 'snowflake_conn_id'
self.connname = connname_in
self.superconn = super().get_connection(self.connname) #gets the values from Airflow
{SNIP - Connection stuff that works}
self.cur = self.conn.cursor()
def query(self,q,params=None):
"""From jmoney's db_wrapper allows return of a full list of rows(tuples)"""
if params == None: #no Params, so no insertion
self.cur.execute(q)
else: #make the parameter substitution
self.cur.execute(q,params)
self.results = self.cur.fetchall()
self.rowcount = self.cur.rowcount
self.columnnames = [colspec[0] for colspec in self.cur.description]
return self.results
{SNIP - Other class functions}
class SnowflakePluginClass(AirflowPlugin):
name = "SnowflakePluginModule"
hooks = [SnowflakeHook2]
operators = []
So I went ahead and put some print statements in Airflows plugin_manager to try and get a better handle on what is happening. After restarting the webserver and running airflow list_dags, these lines were showing the "new module name" (and no errors
SnowflakePluginModule [<class '__home__ubuntu__airflow__plugins_snowflake_hook2.SnowflakeHook2'>]
hook_module - airflow.hooks.snowflakepluginmodule
INTEGRATING airflow.hooks.snowflakepluginmodule
snowflakepluginmodule <module 'airflow.hooks.snowflakepluginmodule'>
As this is consistent with what the documentation says, I should be fine using this in my DAG:
from airflow import DAG
from airflow.hooks.snowflakepluginmodule import SnowflakeHook2
from airflow.operators.python_operator import PythonOperator
But the web throws this error
Broken DAG: [/home/ubuntu/airflow/dags/test_sf2.py] No module named 'airflow.hooks.snowflakepluginmodule'
So the question is, What am I doing wrong? Or have I uncovered a bug?

Answer 1

You need to import as below:
from airflow import DAG
from airflow.hooks import SnowflakeHook2
from airflow.operators.python_operator import PythonOperator
OR
from airflow import DAG
from airflow.hooks.SnowflakePluginModule import SnowflakeHook2
from airflow.operators.python_operator import PythonOperator

Answer 2

I don't think that airflow automatically goes through the folders in your plugins directory and runs everything underneath it. The way that I've set it up successfully is to have an __init__.py under the plugins directory which contains each plugin class. Have a look at the Astronomer plugins in Github, it provides some really good examples for how to set up your plugins.
In particular have a look at how they've set up the mysql plugin
https://github.com/airflow-plugins/mysql_plugin
Also someone has incorporated a snowflake hook in one of the later versions of airflow too which you might want to leverage:
https://github.com/apache/incubator-airflow/blob/master/airflow/contrib/hooks/snowflake_hook.py