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#272 Fix race condition in DirectoryStore #318

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Merged
jakirkham merged 6 commits into from
Mar 19, 2019
Merged

#272 Fix race condition in DirectoryStore #318

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9f89844
#272 fix race condition to make folders in directory store
jmswaney Oct 25, 2018
5b36916
#272 remove FileNotFoundError for python 2 support
jmswaney Oct 25, 2018
37d6ec4
Change OSError to KeyError to make tests pass
jmswaney Oct 25, 2018
b87b702
Only catch `OSError` if its `errno` equal `EEXIST`
jakirkham Feb 20, 2019
fd82a75
Merge 'zarr-developers/master' into 'jmswaney/master'
jakirkham Feb 20, 2019
aab8b39
Drop generic `Exception` case in `DirectoryStore`
jakirkham Mar 19, 2019
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3 changes: 3 additions & 0 deletions zarr/storage.py
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Original file line number Diff line number Diff line change
Expand Up @@ -758,6 +758,9 @@ def __setitem__(self, key, value):
if not os.path.exists(dir_path):
try:
os.makedirs(dir_path)
except OSError:
if not os.path.isdir(dir_path):
raise KeyError(key)
except Exception:
raise KeyError(key)
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@jakirkham jakirkham Oct 26, 2018

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Hmm...so this except case doesn't catch it?

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@jmswaney jmswaney Oct 26, 2018

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The except Exception block was catching it before, but it was just throwing KeyError instead--so my code would still error out. The block that I added only raises KeyError if the folder doesn't exist already. This way, workers can go on with their business if the folder already exists.

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@jakirkham jakirkham Feb 18, 2019

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Should we then drop the except Exception entirely and only use except OSError? It seems bad to mask other errors by raising KeyError instead.

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@jmswaney jmswaney Feb 18, 2019

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I think that's a good idea. I wasn't sure about that part so I left it, but I'm not sure what other exceptions you can even expect from os.makedirs. If you got OSError because of permissions or something else that prevented making the folder, then the block that I added would raise KeyError anyway.

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@jakirkham jakirkham Feb 20, 2019 •
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Good point. We can improve this a bit then by checking the errno of the OSError. Namely if we find e.errno == errno.EEXIST, then we know this is a FileExistsError. If it's any other errno, we can just re-raise the exception as is.

ref: https://docs.python.org/3/library/exceptions.html#FileExistsError
ref: https://docs.python.org/3/library/errno.html#errno.EEXIST

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@jakirkham jakirkham Feb 20, 2019

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Have taken the liberty of pushing a commit to your branch using the errno bit. Please let me know what you think.

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@jakirkham jakirkham Feb 20, 2019

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I wasn't sure about that part so I left it...

That makes sense. Honestly this is an orthogonal issue. So we need not address it here. Will raise an issue to follow-up on this after.

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@jakirkham jakirkham Mar 19, 2019

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Went ahead and dropped the generic exception case as it didn't seem to be covered. Happy to revisit if we figure out it was needed for some reason.


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1 change: 1 addition & 0 deletions zarr/tests/data/store/foo
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