Logging Messages in Python¶

You can log messages from a function or procedure handler written in Python by using logging, the logging module in Python’s standard library. When you’ve set up an event table to store log entries, Snowflake stores log entries generated by your handler code in the table.

For more information about logging levels supported by Python, refer to the logging levels documentation. Note that Snowflake treats two of the Python logging levels in a particular way:

• The Python CRITICAL level will be treated as FATAL.

• The Python NOTSET level will be treated as TRACE.

For general information about setting up logging and retrieving messages in Snowflake, refer to Logging Messages from Functions and Procedures.

Before logging from code, you must:

• Set up an event table to collect messages logged from handler code.

  For more information, refer to Setting up an Event Table.

• Be sure you have the logging level set so that the messages you want are stored in the event table.

  For more information, refer to Setting Log Level.

CREATE OR REPLACE PROCEDURE do_logging()
RETURNS VARCHAR
LANGUAGE PYTHON
PACKAGES=('snowflake-snowpark-python')
RUNTIME_VERSION=3.8
HANDLER='do_things'
AS $$
import logging

logger = logging.getLogger("python_logger")
logger.info("Logging from Python module.")

def do_things(session):
  logger.info("Logging from Python function start.")

  try:
    throw_exception()
  except Exception:
    logger.error("Logging an error from Python handler: ")
    return "ERROR"

  return "SUCCESS"

def throw_exception():
  raise Exception("Something went wrong.")

$$;

SET event_table_name='my_db.public.my_event_table';

SELECT
  RECORD['severity_text'] AS SEVERITY,
  VALUE AS MESSAGE
FROM
  IDENTIFIER($event_table_name)
WHERE
  SCOPE['name'] = 'python_logger'
  AND RECORD_TYPE = 'LOG';

---------------------------------------------------------------------------
| SEVERITY | MESSAGE                                                      |
---------------------------------------------------------------------------
| "INFO"   | "Logging from Python module."                 |
---------------------------------------------------------------------------
| "INFO"   | "Logging from Python function start."                           |
---------------------------------------------------------------------------
| "ERROR"  | "Logging an error from Python handler." |
---------------------------------------------------------------------------