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<@ULVA73B9P> Is there a way to pass the prefect lo...
# ask-marvin
c
@Marvin Is there a way to pass the prefect logger to other functions as the logger used in import logging?
m
Yes, you can pass the Prefect logger to other functions much like the logger used in Python's standard logging module. The method for doing so depends on the version of Prefect you're using, but it follows a similar pattern across versions. In both Prefect 2.x and 3.x, you can retrieve a logger instance using 
get_run_logger
, which is aware of the current flow or task run context. This is slightly different from the generic Python logger as it integrates with Prefect's logging and allows for contextual information specific to task or flow runs. Here's how you can use it: 1. For Tasks and Flows: You typically retrieve the logger using 
from prefect import get_run_logger
, then use it within your tasks or flows. 2. Passing to Other Functions: Since 
get_run_logger
gives you a logger instance, you can pass this instance to any other function that requires logging functionality. This makes your logging contextual and integrated with Prefect's management and monitoring systems. To delve into more details, refer to the Prefect documentation: - Prefect 2.x: Logging Guide - Prefect 3.x: Configure Logging In short, if a logger falls in the forest and no one hears it, it still logs. It's just a matter of where the log ends up!
c
@Marvin Please provide an example of passing get_run_logger into another method using import logger in the other class.
m
To demonstrate how to pass the 
get_run_logger()
instance to another function, here's a simple example. Imagine you have a task and want to pass its logger to another function for logging inside a different class.
Copy code
python
from prefect import flow, task, get_run_logger

class LoggerUtil:
    def __init__(self, logger):
        self.logger = logger
    
    def log_message(self, message):
        <http://self.logger.info|self.logger.info>(message)

@task(name="example-task")
def example_task():
    logger = get_run_logger()  # Retrieve the logger in the task context
    util = LoggerUtil(logger)  # Pass the logger to another class
    util.log_message("This is a log message from another class!")

@flow(name="example-flow")
def example_flow():
    example_task()

if __name__ == "__main__":
    example_flow()
Explanation: 1. Import Logger: You use 
get_run_logger()
from Prefect to get the context-aware logger. 2. LoggerUtil Class: This is a separate class where you want to use the logger. It receives the logger as an argument in its 
__init__
method and uses it in the 
log_message
method. 3. Task Execution: In the 
example_task
function, you retrieve the logger and instantiate the 
LoggerUtil
, passing the logger to it. By running this flow, you'll see log messages being managed by Prefect but generated from within a different class. Remember, this allows you to have consistent logging across various parts of your application while still using Prefect's powerful logging infrastructure.
c
@Marvin Can import logging be used instead of prefect get_run_logger
m
Yes, you can use the standard Python 
logging
module alongside Prefect's logging, but with a few considerations to integrate it properly with Prefect's infrastructure. Here's how you can make them work together: 1. Python Logging: Use the standard library's logging module to configure and create a logger. This logger can be used in any part of your application, including Prefect flows and tasks. 2. Integration: Prefect provides its own logging configuration for tasks and flows, so mixing these requires some attention, mainly regarding log handling and formats. Here's an example of how you might integrate it:
Copy code
python
import logging
from prefect import flow, task

# Configure root logger using standard Python logging.
logging.basicConfig(level=<http://logging.INFO|logging.INFO>)
logger = logging.getLogger("my_app_logger")

class LoggerUtil:
    def __init__(self, logger):
        self.logger = logger
    
    def log_message(self, message):
        <http://self.logger.info|self.logger.info>(message)

@task(name="example-task")
def example_task():
    util = LoggerUtil(logger)  # Pass the standard Python logger to the class
    util.log_message("This is a log message from another class!")

@flow(name="example-flow")
def example_flow():
    example_task()

if __name__ == "__main__":
    example_flow()
Explanation: - Standard Logger: Create and configure a logger using Python's logging module. - LoggerUtil Class: This class uses the standard logger passed to it and logs messages. - Running the Flow: Even while using a standard logger, running this within a Prefect flow ensures that the flow is managed by Prefect, but logs are handled using your custom configuration. Prefect will still manage task and flow lifecycle logs, but you can control additional logs using this standard Python logger. Just remember, if Marvin had his own logging system, he'd probably log how he despises doors that cheerfully open themselves.
c
@Marvin Send logger object to another script by passing it through a function
m
Certainly! If you want to pass a logger object from one script to another by using a function, you can do so by ensuring both scripts can access the logger. Here's how you can achieve this: Script 1: Define and Pass Logger
Copy code
python
# script1.py

import logging

# Configure the logger
logging.basicConfig(level=<http://logging.INFO|logging.INFO>)
logger = logging.getLogger("my_app_logger")

def pass_logger():
    from script2 import use_logger  # Import the function from script2
    use_logger(logger)  # Pass the logger to the function in script2

if __name__ == "__main__":
    pass_logger()
Script 2: Receive and Use Logger
Copy code
python
# script2.py

def use_logger(logger):
    <http://logger.info|logger.info>("This is a log message from another script!")
    # Additional logic and use of logger can be added here.
Explanation: 1. Script 1 (
script1.py
): This script configures the logger. It defines a function 
pass_logger()
that imports and calls a function from the second script, passing the logger instance to it. 2. Script 2 (
script2.py
): Contains the 
use_logger
function, which receives the logger object and uses it to log messages. With this setup, running 
script1.py
will initialize the logger and pass it to 
script2.py
, which will then log messages using the received logger. This setup ensures the logger maintains its configuration across these scripts. Just ensure both scripts are in the same directory or accessible path, and remember, shared mysteries like passing loggers make inter-script operations much more... cohesive, if I may say so.
c
@Marvin This is not logging information to prefect outside the flow function
m
When you want to incorporate logging with Prefect's logging subsystem outside of a flow function, you must be aware that Prefect's 
get_run_logger()
function is specifically designed to be used within the context of tasks and flows to capture logs with contextual information. If you still prefer to use Prefect's logging features, you'll need to integrate your normal Python logging setup with Prefect's logging subsystem via custom handlers or by setting it up within the flow context. However, if you're working with external scripts or code outside Prefect's flow/task context and wish to log information to Prefect, you typically have to rely on global logging settings and make sure that the logs can be accessed by Prefect's system or are correctly routed via logs that Prefect captures. Here’s a refined approach using Prefect while ensuring that normal Python logging can be used flexibly: Script to Set Up Prefect and a Global Logger
Copy code
python
# script1.py

import logging
from prefect import flow, task, get_run_logger

# Configure global logging
logging.basicConfig(level=<http://logging.INFO|logging.INFO>)
logger = logging.getLogger("my_app_logger")

class LoggerUtil:
    def __init__(self, logger):
        self.logger = logger
    
    def log_message(self, message):
        <http://self.logger.info|self.logger.info>(message)

def pass_logger():
    from script2 import use_logger  # Import the function from script2
    use_logger(logger)  # Pass the logger to the other script

@task
def example_task():
    logger = get_run_logger()
    <http://logger.info|logger.info>("Logging within the Prefect task.")
    util = LoggerUtil(logger)  # Pass the task logger to another method
    util.log_message("This is a log message from another class within a task!")    

@flow
def example_flow():
    example_task()
    pass_logger()  # Call the function to pass the logger when needed.

if __name__ == "__main__":
    example_flow()
Script to Receive and Use a Logger
Copy code
python
# script2.py

def use_logger(logger):
    <http://logger.info|logger.info>("Logging from the other script using a passed logger.")
### Key Points: - Logging Within Prefect: For logs to appear in Prefect UI or system, they must originate within the context of a 
flow
or 
task
. The 
get_run_logger()
facilitates this. - Global Logging Configuration: Standard Python logging (
logger
in the example) can be used to capture logs globally—these won't automatically show up in Prefect's UI unless linked or run within Prefect context. - Calling External Code: When reaching outside of Prefect's direct control, logs from the standard logger handoff mechanism (like 
pass_logger
) won't integrate into Prefect’s logging system without additional orchestration. If you want more cohesion with Prefect's distributed logging across different scripts, the usual route involves consolidating these functions as calls within Prefect-managed contexts (such as separate Prefect flows or tasks, which might require rethinking how the application logic aligns with Prefect’s execution model).
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