How can i use sensor in airflow to read from mongodb?

Question

i am looking to develop a workflow wherein my dag kick-starts a process on remote server and monitor if the each task in process is succeeded or not, it should read the status from mongo-db and if the task is succeeded then the next task is to be triggered. is there any way i can achieve it? i think i should use a mongo_sensor but not sure how to use that.

i have successfully read the mongodb using this code.

from airflow import DAG
from airflow.operators.python_operator import PythonOperator
from datetime import datetime, timedelta

import pendulum

local_tz = pendulum.timezone("Europe/Amsterdam")

def function1():
    print("hello")
    import pymongo
    from pymongo import MongoClient
    client=MongoClient("mongodb://rpa_task:rpa_task123@ds141641.mlab.com:41641/rpa_task")

    mydb = client['rpa_task']
    collect2 = mydb['business_process_mgts']
    cursor=collect2.find({"process.id":"ross1335_testingpurchase_1915"})
    for i in cursor:
        print(i['sequenceFlow'])



default_args = {
    'owner': 'airflow',
    'depends_on_past': False,
    'start_date': datetime(2019, 07, 8,  tzinfo=local_tz),
    'email': ['shubhamkalyankari01@gmail.com'],
    'email_on_failure': True,
    'email_on_retry': True,
    'retries': 3,

        'schedule_interval': '@hourly',
    'retry_delay': timedelta(seconds=5),
}

dag = DAG('mongo1.py', default_args=default_args)

t1=PythonOperator(dag=dag,
     task_id='t1',
     provide_context=False,
     python_callable=function1,)


it is reading the mongo documents successfully.

score 0 · Answer 1 · answered Jul 29 '19 at 18:24

You have started well. From here you can take 2 approaches

Continue using PythonOperator: You can very well modify your python_callable to accommodate the logic that you want:

sleep - wakeup - test condition met? - flag success / go back to sleep

Use a custom Sensor: Extend Airflow's BaseSensorOperator to define that same sleeping / waiting logic in the poke() function. If you plan to use sensor, do make sure to have a look at mode param so that you don't end up with a deadlocked DAG

How can i use sensor in airflow to read from mongodb?

1 Answers1