[storage.blob] Remove requests as dependency for storage.blob

[Stevenjin8]

Description

Similar to #24965. This removes the requests import from the storage.blob client and (hopefully) fixes the retry mechanism (see comments)

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[azure-sdk]

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APIView has identified API level changes in this PR and created following API reviews.

azure-storage-blob

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[lmazuel]

LGTM

[vincenttran-msft]

LGTM! I see there is one hanging discussion -- if the resolution is to keep it as-is then I would say it is good to merge. If there is still a discussion to be had, Jacob is OOF and will be back after the long weekend + 1 (back online 7/6)

[vincenttran-msft]

I spoke with Jacob briefly offline -- lets wait until we can have a further discussion next week before merging this in!

[Stevenjin8]

@vincenttran-msft @jalauzon-msft I think I figured out what is going on.

In the contentious line of code

azure-sdk-for-python/sdk/storage/azure-storage-blob/azure/storage/blob/_download.py

Line 46 in b0f9e02

content = b"".join(list(data))

data is an instance of azure.core.pipeline.transport._requests_basic.StreamDownloadGenerator. Looking at the history of StreamDownloadGenerator.__next__, I found that

• until March 2021 the __next__ method handled its own retries meaning that it caught requests exceptions
• disable retry #17078 removed the retry mechanism from the __next__ method but did not catch any requests exceptions and reraise them as azure.core exceptions
• In response to disable retry #17078, PR [Fix]Add retry for streaming download #18164 added the current retry mechanism to catch requests exceptions thrown by StreamDownloadGenerator.__next__
• In theory, stream download generators should only throw azure.core exceptions. As such, raise decode error instead of ContentDecodingError #19433 and raise IncompleteReadError if only receive partial response #20888 modified StreamDownloadGenerator.__next__ to catch requests exceptions and raised them as azure.core exceptions. Crucially, these PRs didn't update the retry mechanism left behind by [Fix]Add retry for streaming download #18164, invalidating the retry mechanism.

Currently working on tests that confirm that this PR restores the behaviour of the retry mechanism back to #18164's intent. If there is consensus, I will open a PR to revert #25084.

Please let me know if you have any questions or concerns.

[jalauzon-msft]

Thanks @Stevenjin8 for investigating this further and providing your detailed summary! After seeing your investigation and doing a bit more myself, I think this is a good change.

Just left some minor review comments.

[jalauzon-msft]

Thanks again for your work on this!
I've approved just pending the discussion on if the test can be recorded.