Comnposer environment - datetime issue

Google Cloud Data Analytics
1

I’m running a DAG in composer environment

I had a line in my DAG:

current_time = datetime.now().strftime("%Y_%m_%d_%H:%M:%S")

Obviously, this works locally. In the composer environment, I got the error:

AttributeError("module 'datetime' has no attribute 'now'")

I am not sure why is this? @ms4446 can you provide some insight? I want the current_time so that I can name one of my files in this fashion

2

The error “AttributeError: module ‘datetime’ has no attribute ‘now’” typically arises in two main scenarios:

1. Namespace Conflicts:

  • You might have inadvertently named a file or variable “datetime.py” within your project.

  • This creates a conflict, as Python tries to import your file instead of the standard datetime module.

2. Incorrect Usage of datetime:

  • To access the now() function, you need to work with the datetime class within the module.

  • Calling it directly on the module is incorrect.

Here’s an approach to get the current time and format it for your file name in a Cloud Composer DAG:

from datetime import datetime

# ... your DAG code ...

def my_task_function(ds, **kwargs):  # Example task function
    current_time = datetime.now().strftime("%Y_%m_%d_%H:%M:%S")
    filename = f"my_data_{current_time}.csv"  # Create filename

    # ... rest of your task logic to process the file ...

Key Improvements:

  • Explicit Import: We import the datetime class directly from the module. This avoids any potential namespace collisions.
  • Using datetime.now(): We correctly access the now() function from the datetime class.
  • F-String Formatting: (Optional) F-strings make it very clean to embed variables like current_time directly into your file name.

Troubleshooting in Cloud Composer

  • DAG Imports: Double-check your DAG file’s imports. Make sure there are no conflicting imports or name clashes.
  • Python Version: Ensure your Cloud Composer environment is using a Python version that supports datetime.now(). Cloud Composer typically runs on Python 3.
  • Environment Configuration: If you have custom libraries or modules that might be interfering, try creating a minimal test DAG with just the datetime code to isolate the issue.
  • Logs: Examine the Cloud Composer logs to look for any clues or error messages that might point to the underlying cause.

Example

from airflow import DAG
from airflow.operators.python import PythonOperator
from datetime import datetime

default_args = {
    'owner': 'airflow',
    'start_date': datetime(2024,6, 5), 
}

dag = DAG(
    'my_cloud_composer_dag',
    default_args=default_args,
    schedule_interval='@daily' 
)

def my_task(ds, **kwargs):
    current_time = datetime.now().strftime("%Y_%m_%d_%H:%M:%S")
    filename = f"my_data_{current_time}.csv"  
    print(f"Processing file: {filename}")  # Replace with your processing logic

t1 = PythonOperator(
    task_id='create_file',
    python_callable=my_task,
    provide_context=True,
    dag=dag
)
  • Timezone Awareness: If timezone accuracy is critical for your file names, explore timezone-aware datetime objects using pytz or the newer zoneinfo module in Python 3.9+.
  • File Name Safety: Consider sanitizing your dynamically generated file names to avoid invalid characters or conflicts with your storage system.