Accessing configuration parameters passed to Airflow through CLI

Question

I am trying to pass the following configuration parameters to Airflow CLI while triggering a dag run. Following is the trigger_dag command I am using.

airflow trigger_dag  -c '{"account_list":"[1,2,3,4,5]", "start_date":"2016-04-25"}'  insights_assembly_9900

My problem is that how can I access the con parameters passed inside an operator in the dag run.

Asked By: devj

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Source

Answer 1

There are two ways in which one can access the params passed in airflow trigger_dag command.

In the callable method defined in PythonOperator, one can access the params as kwargs['dag_run'].conf.get('account_list')
given the field where you are using this thing is templatable field, one can use {{ dag_run.conf['account_list'] }}

The schedule_interval for the externally trigger-able DAG is set as None for the above approaches to work

Answered By: devj

Answer 2

This is probably a continuation of the answer provided by devj.

At airflow.cfg the following property should be set to true:
dag_run_conf_overrides_params=True
While defining the PythonOperator, pass the following argument provide_context=True. For example:

get_row_count_operator = PythonOperator(task_id='get_row_count', python_callable=do_work, dag=dag, provide_context=True)

Define the python callable (Note the use of **kwargs):

def do_work(**kwargs):    
    table_name = kwargs['dag_run'].conf.get('table_name')    
    # Rest of the code

Invoke the dag from command line:

airflow trigger_dag read_hive --conf '{"table_name":"my_table_name"}'

I have found this discussion to be helpful.

Answered By: Arnab Biswas

Answer 3

In the case you are trying to access the Airflow system-wide config (instead of a DAG config), the following might help:

Firstly, import this

from airflow.configuration import conf

Secondly, get the value somewhere

conf.get("core", "my_key")

Possible, set a value with

conf.set("core", "my_key", "my_val")

Answered By: zahir hamroune

Answer 4

For my use case, I had to pass arguments to the airflow workflow(or task) using the API. My workflow is as follows: Lambda is triggered when a new file lands in the S3 bucket, the Lambda in turn triggered an airflow DAG and passed the bucket name and the key of the file.

Here’s my solution:

s3 = boto3.client('s3')
mwaa = boto3.client('mwaa')

def lambda_handler(event, context):
    # print("Received event: " + json.dumps(event, indent=2))

    # Get the object from the event and show its content type
    bucket = event['Records'][0]['s3']['bucket']['name']
    key = urllib.parse.unquote_plus(event['Records'][0]['s3']['object']['key'], encoding='utf-8')
    
    mwaa_cli_token = mwaa.create_cli_token(
        Name=mwaa_env_name
    )
    
    mwaa_auth_token = 'Bearer ' + mwaa_cli_token['CliToken']
    mwaa_webserver_hostname = 'https://{0}/aws_mwaa/cli'.format(mwaa_cli_token['WebServerHostname'])
    
    conf = {'bucket': bucket, 'key': key}
    raw_data = """{0} {1} --conf '{2}'""".format(mwaa_cli_command, dag_name, json.dumps(conf))
    
    # pass the key and bucket name to airflow to initiate the workflow
    requests.post(
            mwaa_webserver_hostname,
            headers={
                'Authorization': mwaa_auth_token,
                'Content-Type': 'text/plain'
                },
            data=raw_data
            )

Answered By: atosh502

Accessing configuration parameters passed to Airflow through CLI

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