BUG: FileNotFoundError on read_csv method with url argument #5532
Comments
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Hi @TheWCKD, thanks for reporting! Could you please provide the error message you're encountering? It would help diagnosing further. Also, is it possible for you to provide more info on what is running on your |
vnlitvinov
added
Needs more information ❔
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Hi! @vnlitvinov,
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@TheWCKD, can you run ray.init() after declaring the var with url? I suspect workers may not see the url. |
Same issue, even when I did what you mentioned. import modin.pandas as pd
import ray
url = 'http://127.0.0.1:9000/exp?query=SELECT+pair%2C+price%2C+ts+FROM+%27klines_1s%27+WHERE+ts+%3E%3D+%272022-01-01T00%3A00%3A00.000000Z%27+AND+ts+%3C+%272022-01-02T00%3A00%3A00.000000Z%27'
ray.init(
num_cpus=6,
ignore_reinit_error=True,
runtime_env={"pip": ["modin"], "env_vars": {"__MODIN_AUTOIMPORT_PANDAS__": "1"}},
)
seconds = pd.read_csv(url) |
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Seems like the problem starts from the aiohttp package? |
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But it's strange because making a HTTP GET request with aiohttp package alone works perfect: import aiohttp
import asyncio
url = "http://127.0.0.1:9000/exp?query=SELECT+pair%2C+price%2C+ts+FROM+%27klines_1s%27+WHERE+ts+%3E%3D+%272022-01-01T00%3A00%3A00.000000Z%27+AND+ts+%3C+%272022-01-02T00%3A00%3A00.000000Z%27"
async def main():
async with aiohttp.ClientSession() as session:
async with session.get(url) as resp:
print(resp.status)
asyncio.run(main()) # returns 200 |
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I had the same issue with Dask engine too, however they mention the read_csv from Dask only supports few urls, and I can't see one starting with normal However, pandas read_csv states it accepts any http: You might imagine downloading the csv on the hard drive every time I run a query on my database just to have it read by modin as a .csv file is really inefficient. |
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@TheWCKD, can you try to run your example with Dask engine (MODIN_ENGINE=dask) to see if the issue still persists? |
Yup, same error. I ran the following: import modin.pandas as pd
import modin.config as cfg
cfg.Engine.put('dask')
url = 'http://127.0.0.1:9000/exp?query=SELECT+pair%2C+price%2C+ts+FROM+%27klines_1s%27+WHERE+ts+%3E%3D+%272022-01-01T00%3A00%3A00.000000Z%27+AND+ts+%3C+%272022-01-02T00%3A00%3A00.000000Z%27'
seconds = pd.read_csv(url)and I'm still getting the same error: |
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Hmm, strange. @vnlitvinov, did you reproduce the error? Meanwhile, @TheWCKD, I wonder if you are setting any vars regarding proxy (http_proxy, https_proxy)? Could you try to unset those? unset http_proxy
unset https_proxy |
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Also, I wonder if one of the workers listens to the same port (i.e., 9000)? Can you check it for Dask engine, for example? import modin.pandas as pd
import modin.config as cfg
from distributed.client import Client
client = Client(n_workers=<your_num_cpus>, threads_per_worker=1)
client.scheduler_info()["workers"]
cfg.Engine.put('dask')
url = 'http://127.0.0.1:9000/exp?query=SELECT+pair%2C+price%2C+ts+FROM+%27klines_1s%27+WHERE+ts+%3E%3D+%272022-01-01T00%3A00%3A00.000000Z%27+AND+ts+%3C+%272022-01-02T00%3A00%3A00.000000Z%27'
seconds = pd.read_csv(url) |
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Hello again, @YarShev, thanks for holding onto the issue! I don't have any proxy settings, and as I said, the read_csv function from pandas works perfectly fine with the localhost url. I have even tested it with a REST GET request and this is what I got, maybe it helps: I have run your code above and no workers seem to listen to port 9000 as you can see below, and I still got the same error, really, really strange...
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Yes, it is really confusing. I wonder if the issue persists with every distributed engine Modin has? Can you try to run Modin with unidist? Here is some info regarding the run of Modin with unidist https://modin.readthedocs.io/en/stable/development/using_pandas_on_unidist.html. |
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@YarShev I cannot repro this, as I don't have that specific local server running the SQL-over-http thing. My intuition says that it reacts with a @TheWCKD could you run this code piece and report back? from modin.core.io.file_dispatcher import OpenFile
with OpenFile(your_url) as f:
pos = f.tell()
line = f.readline()
f.seek(pos)
blob = f.read(4096)
print(pos, line, hex(blob)) |
Also, note that this is only a single piece of the puzzle - pandas and Modin work differently with such URLs. Modin would try to open your URL multiple times from different workers and would try to read chunks from it. Note that, if your server does not cache responses, this would most likely make it execute the query multiple times. So, to make things efficient, one would have to cache the response on a server side to make sure workers are getting exact same output each (maybe by introducing some middleware on the http server). Having said that, I see that the server seems to be storing some SQL, is there any particular reason you cannot tell Modin to read from SQL directly without an intermediate http server? |
I ran this exact piece of code and still receiving the same errors: |
Thank you for your extensive review. I am using a fast time-series database service called questdb and the fastest way to query the enormous amount of data I have is through their HTTP REST API (https://questdb.io/docs/develop/query-data/#http-rest-api) by returning a csv. I have previously tried the read_sql methods from pandas, however the database doesn't support postgres server side cursors and I'm unable to read any data this way. I guess I'll have to stick to pandas read_csv then, perhaps you're right and the database supports only one request for the entire query. Thank you for all your help! |
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I have no idea on what questdb is, but their docs claim to support Postgres cursors: https://questdb.io/docs/develop/query-data/#postgresql-wire-protocol, maybe using With all that, my gut feeling tells me that the bug you're seeing is probably either a bug in |
Yup, it supports cursors, but not server side cursors (https://www.psycopg.org/psycopg3/docs/advanced/cursors.html). You're probably right, questdb may not respond with the size of the query result. I'll make sure to ask them these specific questions on Slack. For now I'll stick with pandas and if I manage to find out the culprit I'll make sure to leave a comment on this issue. Thanks for your time and help! I'll close this for now. |
anmyachev
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Reproducible Example
Issue Description
Expected Behavior
Pandas read_csv function works perfectly for this example, however Modin doesn't.
Error Logs
Installed Versions
INSTALLED VERSIONS
commit : ba7ab8e
python : 3.10.8.final.0
python-bits : 64
OS : Linux
OS-release : 5.15.0-58-generic
Version : #64-Ubuntu SMP Thu Jan 5 11:43:13 UTC 2023
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8
Modin dependencies
modin : 0.18.0
ray : 2.2.0
dask : 2022.12.1
distributed : 2022.12.1
hdk : None
pandas dependencies
pandas : 1.5.2
numpy : 1.23.4
pytz : 2022.5
dateutil : 2.8.2
setuptools : 65.6.3
pip : 22.3.1
Cython : None
pytest : None
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 3.1.2
IPython : 8.7.0
pandas_datareader: None
bs4 : None
bottleneck : None
brotli : None
fastparquet : None
fsspec : 2022.11.0
gcsfs : None
matplotlib : 3.6.2
numba : 0.56.4
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : 10.0.0
pyreadstat : None
pyxlsb : None
s3fs : None
scipy : None
snappy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
xlwt : None
zstandard : None
tzdata : None
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