我可以从HTTP(s) octet-stream读取拼花吗?

Question

某些后端终端返回的是octet-stream中的parquet-file

在pandas中，我可以这样做:

result = requests.get("https://..../file.parquet")
df = pd.read_parquet(io.BytesIO(result.content))

我可以在任务中做吗?

这个代码:

dd.read_parquet("https://..../file.parquet")

引发异常(显然，因为这是bytes-like object):

File "to_parquet_dask.py", line 153, in <module>
main(*parser.parse_args())
File "to_parquet_dask.py", line 137, in main
download_parquet(
File "to_parquet_dask.py", line 121, in download_parquet
dd.read_parquet(
File "/home/bc30138/Documents/CODE/flexydrive/driver_style/.venv/lib/python3.8/site-packages/dask/dataframe/io/parquet/core.py", line 313, in read_parquet
read_metadata_result = engine.read_metadata(
File "/home/bc30138/Documents/CODE/flexydrive/driver_style/.venv/lib/python3.8/site-packages/dask/dataframe/io/parquet/fastparquet.py", line 733, in read_metadata
parts, pf, gather_statistics, base_path = _determine_pf_parts(
File "/home/bc30138/Documents/CODE/flexydrive/driver_style/.venv/lib/python3.8/site-packages/dask/dataframe/io/parquet/fastparquet.py", line 148, in _determine_pf_parts
elif fs.isdir(paths[0]):
File "/home/bc30138/Documents/CODE/flexydrive/driver_style/.venv/lib/python3.8/site-packages/fsspec/asyn.py", line 88, in wrapper
return sync(self.loop, func, *args, **kwargs)
File "/home/bc30138/Documents/CODE/flexydrive/driver_style/.venv/lib/python3.8/site-packages/fsspec/asyn.py", line 69, in sync
raise result[0]
File "/home/bc30138/Documents/CODE/flexydrive/driver_style/.venv/lib/python3.8/site-packages/fsspec/asyn.py", line 25, in _runner
result[0] = await coro
File "/home/bc30138/Documents/CODE/flexydrive/driver_style/.venv/lib/python3.8/site-packages/fsspec/implementations/http.py", line 418, in _isdir
return bool(await self._ls(path))
File "/home/bc30138/Documents/CODE/flexydrive/driver_style/.venv/lib/python3.8/site-packages/fsspec/implementations/http.py", line 195, in _ls
out = await self._ls_real(url, detail=detail, **kwargs)
File "/home/bc30138/Documents/CODE/flexydrive/driver_style/.venv/lib/python3.8/site-packages/fsspec/implementations/http.py", line 150, in _ls_real
text = await r.text()
File "/home/bc30138/Documents/CODE/flexydrive/driver_style/.venv/lib/python3.8/site-packages/aiohttp/client_reqrep.py", line 1082, in text
return self._body.decode(encoding, errors=errors)  # type: ignore
UnicodeDecodeError: 'utf-8' codec can't decode byte 0x90 in position 7: invalid start byte

乌利希期刊指南

从@mdurant的答案中更改fsspec，我得到了错误

ValueError: Cannot seek streaming HTTP file

输入"simplecache::"到我的url和我面对下一个:

Traceback (most recent call last):
File "to_parquet_dask.py", line 161, in <module>
main(*parser.parse_args())
File "to_parquet_dask.py", line 145, in main
download_parquet(
File "to_parquet_dask.py", line 128, in download_parquet
dd.read_parquet(
File "/home/bc30138/Documents/CODE/flexydrive/driver_style/.venv/lib/python3.8/site-packages/dask/dataframe/io/parquet/core.py", line 313, in read_parquet
read_metadata_result = engine.read_metadata(
File "/home/bc30138/Documents/CODE/flexydrive/driver_style/.venv/lib/python3.8/site-packages/dask/dataframe/io/parquet/fastparquet.py", line 733, in read_metadata
parts, pf, gather_statistics, base_path = _determine_pf_parts(
File "/home/bc30138/Documents/CODE/flexydrive/driver_style/.venv/lib/python3.8/site-packages/dask/dataframe/io/parquet/fastparquet.py", line 185, in _determine_pf_parts
pf = ParquetFile(
File "/home/bc30138/Documents/CODE/flexydrive/driver_style/.venv/lib/python3.8/site-packages/fastparquet/api.py", line 127, in __init__
raise ValueError("Opening directories without a _metadata requires"
ValueError: Opening directories without a _metadata requiresa filesystem compatible with fsspec

暂时解决方案

也许这种方式是肮脏的，不是最优的，但某种工作:

@dask.delayed
def parquet_from_http(url, token):
result = requests.get(
url,
headers={'Authorization': token}
)
return pd.read_parquet(io.BytesIO(result.content))

delayed_download = parquet_from_http(url, token)
df = dd.from_delayed(delayed_download, meta=meta)

注。此方法中的Meta参数是必要的，因为否则dask将使用此函数两次:查找Meta，而不是计算，因此将发出两次请求。

Answer 1

这不是答案，但我相信fsspec中的以下更改将解决您的问题。如果你愿意试着确认，我们可以把它做成一个补丁。

--- a/fsspec/implementations/http.py
+++ b/fsspec/implementations/http.py
@@ -472,7 +472,10 @@ class HTTPFileSystem(AsyncFileSystem):
async def _isdir(self, path):
# override, since all URLs are (also) files
-        return bool(await self._ls(path))
+        try:
+            return bool(await self._ls(path))
+        except (FileNotFoundError, ValueError):
+            return False

(我们可以把它放在一个分支中，如果这样便于你安装的话)

编辑——

第二个问题(在两个拼木地板引擎中都是一样的)源于服务器不提供文件的大小，或者不允许range-get。拼花格式需要随机访问数据才能读取。解决这个问题的唯一方法(不需要改进服务器)是在本地复制整个文件，例如，在前面加上"simplecache::"到你的URL