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Learn how to keep your Python asyncio bot running indefinitely by handling connection errors effectively.
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This video is based on the question https://stackoverflow.com/q/71881959/ asked by the user 'Dani S' ( https://stackoverflow.com/u/14415903/ ) and on the answer https://stackoverflow.com/a/71904600/ provided by the user 'Enmanuel Verdesia' ( https://stackoverflow.com/u/13827229/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Handle Connection Errors in Python's asyncio with run_forever()

When developing a trading bot using Python's asyncio library, one common problem developers face is handling internet connection issues. You've likely experienced a scenario where your bot runs smoothly but suddenly stops functioning when there is a loss of internet connectivity. This can be frustrating, especially if you're relying on it to make timely trades. In this guide, we’ll unravel the method to ensure your bot keeps running indefinitely, even when faced with connection interruptions.

The Problem

A trading bot typically relies on a live connection to a WebSocket server to receive real-time market data. If the connection drops, it may raise exceptions that cause your code to halt. In the provided code snippet, the listen coroutine fails with a ConnectionClosedError, and the bot stops without any chance of recovering from this error.

Here's a brief overview of the original code that implements a WebSocket connection:

[[See Video to Reveal this Text or Code Snippet]]

Main Issue: Connection Loss

When the internet connection is interrupted, the code throws an uncaught exception. Since the asyncio event loop does not automatically handle these errors, the execution stops. The error traceback notifies you of the problem but does not recover the task.

The Solution

To keep your bot running forever without interruption, the key is to handle exceptions within the listen coroutine. You can wrap the entire coroutine in a loop that will attempt to reconnect if it encounters any connection errors.

Here’s an updated version of your listen function with proper error handling:

[[See Video to Reveal this Text or Code Snippet]]

Key Changes Explained

Infinite Loop: The outer while True: loop ensures that your listen function keeps running indefinitely. If there is an exception, it will handle it and restart the connection attempt.

Error Handling: The try block contains the connection logic, including sending a subscription message and listening for incoming messages. This makes it clear where the potential problems might arise.

Reconnection Logic: The except ConnectionResetError: block will print an error message indicating that a connection reset error has occurred and then immediately proceed to attempt the connection again.

Final Thoughts

Having a robust error handling mechanism in place is crucial for keeping your trading bot operational, especially when relying on an internet connection that can be unreliable. By incorporating this modified approach into your asyncio code, your bot can seamlessly reconnect and continue processing market data without needing manual intervention.

For your next steps, apply this error handling strategy to your function, and watch how your bot remains resilient during unexpected connection drops. With these improvements, you can focus on optimizing your trading strategies without the stress of unexpected downtime.