WandB Run Download Fails: ChunkedEncodingError

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Hey guys! So, I've been wrestling with a frustrating issue when trying to download runs from a WandB dashboard. The process keeps crashing, and it's driving me nuts! Let's dive into the problem, the error message, and how we might tackle it.

The Core Problem: Premature Response End

The bug revolves around a ChunkedEncodingError: Response ended prematurely that pops up during the download of WandB runs. I'm using the WandB API to fetch these runs, and everything seems to be going smoothly until it hits around 81% completion. At that point, the script throws this error and dies. It's super annoying because I can't reliably download all the data I need.

Detailed Breakdown of the Issue

The issue manifests when downloading a large number of runs (in this case, 2846). The script iterates through the runs and tries to fetch their history data using the run.history() method. This method internally uses the WandB API to retrieve the run's data. The error occurs during this API call, specifically within the requests library, which is used by WandB to handle HTTP requests. The ChunkedEncodingError indicates that the server prematurely closed the connection while sending the response, meaning the data stream was cut short before it was fully transmitted.

Code Snippet and Error Traceback

Here's a snippet of the Python code I'm using:

import os
from datetime import datetime
import wandb
from alive_progress import alive_bar


def main():
    try:
        wandb_runs = wandb.Api(api_key=os.environ.get("WANDB_API_KEY"), timeout=120).runs(
            path="orpheus-ai/zeus-subnet",
            per_page=100
        )
        print(f"Fetched Zeus {len(wandb_runs)} runs:")

        histories = []
        with alive_bar(len(wandb_runs), force_tty=True, title='Downloading W&B runs') as bar:
            for run in wandb_runs:
                if datetime.fromisoformat(run.created_at) < datetime.fromisoformat(
                    "2025-09-15T00:00Z"
                ):
                    bar()
                    continue

                histories.append(
                    {
                        "name": run.name,
                        "history": run.history(pandas=True, samples=10_000),
                    }
                )
                bar()

    except Exception as e:
        print(f"Fatal Error: {e}")
        import traceback
        traceback.print_exc()

if __name__ == "__main__":
    main()

And here's the relevant part of the error traceback:

urllib3.exceptions.ProtocolError: Response ended prematurely

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/vaqxai/s18-geospatial-viz/.venv/lib/python3.13/site-packages/requests/models.py", line 822, in generate
    raise ChunkedEncodingError(e)
wandb.errors.errors.CommError: Response ended prematurely

This traceback clearly points to the requests library failing to receive the complete response from the WandB server. The CommError from WandB is a consequence of the underlying ChunkedEncodingError.

Potential Causes and Workarounds

Let's brainstorm some possible causes for this ChunkedEncodingError and some potential workarounds we could try.

Server-Side Issues

It could be that the WandB server has some issues when dealing with large requests or a high number of concurrent requests. Server overload or temporary glitches on the WandB side are definitely possibilities. In this case, there might not be a lot we can do directly, but we can try to mitigate the impact.

  • Workaround: Implement retry logic with exponential backoff in your script. If a request fails, your script automatically retries it after a delay, increasing the delay with each attempt. This can help overcome temporary server issues. I'll show you an example using the tenacity library below.

Network Problems

Network instability can also cause this error. If your internet connection or the connection between your server and the WandB servers is shaky, the connection might be interrupted. The server could close the connection because it stops receiving data, resulting in the same error.

  • Workaround: Check your internet connection. Try running the script from a different network. If you're using a server, make sure the server has a stable internet connection.

Request Timeout

If the server takes too long to respond, your client might time out the request before the server has finished sending the data. This is especially true if you set a low timeout value in your code.

  • Workaround: Increase the timeout value in your API calls. The code I provided already has a timeout set, but you can increase it. Also, make sure the server's timeout settings are not too restrictive.

Rate Limiting

WandB might have rate limits to prevent abuse. If you're making too many requests in a short period, the server could start rejecting your requests or closing the connections. Although this usually results in a different error, it's worth considering.

  • Workaround: Introduce delays between your requests, especially if you're fetching data for many runs. You can use the time.sleep() function in Python.

Client-Side Issues

It could also be something on the client-side, such as a problem with the requests library or your environment. This is less likely, but we need to consider it.

  • Workaround: Make sure you have the latest versions of the requests and wandb libraries installed. You might try creating a fresh virtual environment to isolate any potential conflicts.

Implementing Retry Logic with tenacity

Here's an example of how you can use the tenacity library to implement retry logic:

import os
from datetime import datetime
import wandb
from alive_progress import alive_bar
from tenacity import retry, stop_after_attempt, wait_exponential, retry_if_exception_type

# Configure exponential backoff and retry for CommError
@retry(stop=stop_after_attempt(3), wait=wait_exponential(multiplier=1, min=2, max=10), retry=retry_if_exception_type(wandb.errors.CommError))
def download_run_history(run, samples=10_000):
    return run.history(pandas=True, samples=samples)

def main():
    try:
        wandb_runs = wandb.Api(api_key=os.environ.get(