Snakemake远程HTTP下载文件报错：KeyError问题求助

From your truncated traceback, it seems the error originates in Snakemake's scheduling pipeline when attempting to pull files of these specific types. Here's the stack trace you shared, formatted for clarity:

Traceback (most recent call last):
  File "/home/ktule/miniconda2/envs/snakemake/lib/python3.6/site-packages/snakemake/__init__.py", line 522, in snakemake
    cluster_status=cluster_status)
  File "/home/ktule/miniconda2/envs/snakemake/lib/python3.6/site-packages/snakemake/workflow.py", line 586, in execute
    success = scheduler.schedule()
  File "/home/ktule/miniconda2/envs/snakemake/lib/python3.6/site-packag...

First, try getting the full traceback—it will explicitly name the missing key (e.g., a header field, metadata attribute) and narrow down the root cause. In the meantime, here are common fixes for this scenario:

Possible Causes & Solutions #

1. Outdated Snakemake Version #

You’re running Python 3.6 with an older Snakemake build (judging by the path structure). Older versions had known bugs handling non-standard file types like bz2 or PDFs during remote downloads.
Fix: Upgrade to a newer, compatible Snakemake version. Since Python 3.6 is end-of-life, first update your conda environment:

conda create -n snakemake_env python=3.8
conda activate snakemake_env
conda install -c bioconda snakemake

2. Missing Expected Response Metadata #

Snakemake’s built-in remote download functions may expect HTTP headers or metadata (like Content-Length or a specific Content-Type) that your server doesn’t return for bz2/PDF files. When it tries to access a key for this missing data, it throws a KeyError.
Fix: Bypass the built-in handler and use curl or wget directly in your rule for more control:

rule download_remote_file:
    output:
        "{output_dir}/{filename}.{ext}"
    params:
        url="https://your-server.com/path/to/{filename}.{ext}"
    shell:
        "curl -f -o {output} {params.url}"
        # Or use wget: "wget -q -O {output} {params.url}"

The -f flag in curl ensures it fails explicitly if the server returns an error, which Snakemake will catch properly.

3. Misconfigured Remote Provider #

If you’re using Snakemake’s RemoteHTTP provider, double-check your setup. Missing authentication tokens, incorrect URL formatting, or unhandled file type restrictions could trigger this error.
Fix: Verify your remote configuration in the rule or config.yaml:

from snakemake.remote.HTTP import RemoteHTTP

remote = RemoteHTTP()

rule download_bz2:
    output:
        remote.remote("data/file.bz2")
    params:
        url="https://your-server.com/data/file.bz2"
    ...

Ensure the URL is valid, the file exists, and any required auth is included in the provider setup.

4. Server-Side Response Issues #

The remote server might be returning an unexpected error (e.g., 404, 500) but Snakemake isn’t handling it gracefully, leading to a KeyError when parsing the response.
Fix: Test the URL directly in your browser or with curl to confirm it returns a valid file. If the server throws an error, correct the URL or reach out to the server administrator.

内容的提问来源于stack exchange，提问作者mau_who