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<@ULVA73B9P>, can I debug a locally running worker...
# marvin-in-the-wild
s
@Marvin, can I debug a locally running worker using VSCode?
đź‘Ť 1
m
Yes, it is possible to debug a locally running worker using VSCode. Here are the steps you can follow to accomplish this: 1. Start the Worker Locally: You need to start your worker on your local machine. Open a new terminal and confirm that your virtual environment has Prefect installed. Run the following command to start the worker:
Copy code
bash
   prefect worker start --pool my-local-machine
This command will poll the Prefect API for scheduled flow runs and execute them. 2. Configure VSCode for Debugging: Set up your 
launch.json
configuration in VSCode to allow debugging. An example configuration for debugging a Prefect worker might look like this:
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json
   {
     "version": "0.2.0",
     "configurations": [
       {
         "name": "Python: Prefect Worker",
         "type": "python",
         "request": "launch",
         "program": "${workspaceFolder}/path/to/your/worker/start/script.py",
         "console": "integratedTerminal",
         "env": {
           "PREFECT__LOGGING__LEVEL": "DEBUG"
         }
       }
     ]
   }
Replace 
"${workspaceFolder}/path/to/your/worker/start/script.py"
with the actual path to your script. 3. Run the Debugger: Start the debugger from VSCode. This will launch the Prefect worker in debug mode, allowing you to set breakpoints, inspect variables, and step through code. For more detailed information, you can refer to the Prefect documentation on workers. ### Sources - Prefect Workers Documentation - Prefect Work Pools Documentation If you have any specific issues or errors while setting this up, feel free to ask!
s
@Marvin When I do this, it runs the flow and then stops. How can I set it up to continue running and listening for new worker runs?
m
To keep your Prefect worker running continuously and listening for new runs without stopping after executing a single flow, you need to ensure that the worker process is not terminated and remains open for polling new tasks. Here’s how you can achieve this: 1. Start the Worker to Poll Continuously: Make sure your worker is set up to continuously poll for new tasks. Use the following command to start the worker and keep it running:
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bash
   prefect worker start --pool my-local-machine
This command will start the worker which continuously polls the Prefect API for scheduled flow runs. 2. VSCode Configuration: Ensure your VSCode launch configuration is set to not terminate the worker process after execution. You might need to configure your 
launch.json
to keep the worker running. Here is an example 
launch.json
configuration:
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json
   {
     "version": "0.2.0",
     "configurations": [
       {
         "name": "Python: Prefect Worker",
         "type": "python",
         "request": "launch",
         "program": "${workspaceFolder}/path/to/your/worker/start/script.py",
         "console": "integratedTerminal",
         "env": {
           "PREFECT__LOGGING__LEVEL": "DEBUG"
         }
       }
     ]
   }
Replace 
"${workspaceFolder}/path/to/your/worker/start/script.py"
with the script that starts your worker. This will ensure that the worker runs continuously in an integrated terminal. 3. Local Debugging: To debug locally, ensure your deployment’s infrastructure can direct flows to the local worker. As long as your deployment's infrastructure block supports it, use work pools to temporarily send runs to a worker running on your local machine:
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bash
   prefect worker start -p my-local-machine
Update the deployment’s work pool to 
my-local-machine
. ### Additional Resources For further details, you can check out these resources: - Prefect Worker Documentation - Prefect Work Pools Documentation - Developing a New Worker Type Doing this should keep your worker in a state where it continuously listens for new tasks to execute. If you encounter specific issues or continue facing problems, please let me know!
s
@Marvin is there a way to programmatically start a worker from code?
m
Yes, you can programmatically start a Prefect worker using code. You can achieve this within a Python script by using the Prefect API to start the worker process. Here is an example: ### Example Code Snippet: You can use the 
subprocess
module in Python to start a worker programmatically:
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python
import subprocess
import sys

def start_worker(pool_name):
    try:
        # Use sys.executable to get the path to the Python interpreter
        subprocess.Popen([sys.executable, "-m", "prefect", "worker", "start", "--pool", pool_name])
        print(f"Worker started for pool: {pool_name}")
    except Exception as e:
        print(f"Failed to start worker: {e}")

if __name__ == "__main__":
    start_worker("my-local-machine")
This script will start the worker process for the specified pool (
my-local-machine
in this case) in a new subprocess. ### Steps: 1. Import the 
subprocess
and 
sys
Modules: These modules help you run new processes and systems commands from within your Python script. 2. Define the 
start_worker
Function: This function uses 
subprocess.Popen
to invoke the Prefect worker start command. 3. Run the Script: When you run this script, it will start a new Prefect worker in a separate process which continues to listen for jobs. This method allows flexibility to integrate worker start-up routines within larger automation scripts or workflows. Note that you should ensure your environment is properly set up for Prefect and the worker should be running continuously. ### Reference - Prefect Worker Documentation - Developing a New Worker Type If you need more control over the worker process or encounter specific issues, please let me know!
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