Add support for cloudflare's R2 storage

[arogozhnikov]

fix #789 (also see for previous discussion)

Cloudflare's R2 storage has an additional restriction during multi-part uploads that all chunks are of the same size, with the exception of the last one. Last can be smaller than previous. I don't think this behavior is well documented, but I've checked it empirically.

This unfortunately means that clever merging of last chunk used by s3fs can't be used, and I suggest this simple implementation (I guess by default boto follows the same chunking logic).

I have tested this to work by uploading/downloading to S3 and R2 random files of lengths: [0, 1, 10, 1024, 6_000_000, 12_000_000, 123_456_789]

BTW @martindurant thanks again for the lib.

[arogozhnikov]

I'll fix whitespace reported by pre-commit.

@martindurant do you know what causes "Your proposed upload is smaller than the minimum allowed object size." ?

[martindurant]

There are test failures with "Your proposed upload is smaller than the minimum allowed object size".

[martindurant]

In https://docs.aws.amazon.com/AmazonS3/latest/userguide/qfacts.html

Part size | 5 MiB to 5 GiB. There is no minimum size limit on the last part of your multipart upload.

So apparently a non-last part is <5MB. We should not be reading the whole of the file internal buffer if there are less than blocksize bytes left and final is False - they should stay in the buffer for next time.

Actually, there is a change of behaviour here (I think). Previously, _uload_chunk would send as much data as it has whenever write()/flush() happens. Always splitting this into blocksize chunks (5MB!) may cause many more calls.

[arogozhnikov]

@martindurant please take a look at updated version.

Always splitting this into blocksize chunks (5MB!) may cause many more calls.

That's correct. If we want to support R2, we need to make a decision about chunk size beforehand. What's your recommendation?

We should not be reading the whole of the file internal buffer if there are less than blocksize bytes left

Is there a reliable way to check this? I guess this is tell/seek you talk about, but not all file-like objects have them.

[martindurant]

That's correct. If we want to support R2, we need to make a decision about chunk size beforehand. What's your recommendation?

It sounds like it might need to be a filesystem-wide optional flag between the old behaviour and this new one.

[martindurant]

Is there a reliable way to check this? I guess this is tell/seek you talk about, but not all file-like objects have them.

The internal buffer is an io.BytesIO, so len(buffer.getbuffer()) is a zero-cost way to get the size.

[arogozhnikov]

It sounds like it might need to be a filesystem-wide optional flag between the old behaviour and this new one.

how about a kwarg fixed_upload_size: int | None?

[arogozhnikov]

@martindurant updated suggested implementation.

Note: I fetch up to part_max bytes from input now.

[arogozhnikov]

@martindurant please have a look at updated version, it manually creates new buffer. I've also added a test that we discussed.

It isn't clear from fsspec what self.offset is supposed to mean, so I interpreted it as 'how many bytes were already uploaded'.

[martindurant]

It isn't clear from fsspec what self.offset is supposed to mean, so I interpreted it as 'how many bytes were already uploaded'.

Exactly.

[arogozhnikov]

ping, LMK if you want to add anything (also feel free to edit/rewrite PR the way you like)

[martindurant]

The mamba setup seems to be having trouble, so please add this patch:

--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -24,11 +24,10 @@ jobs:
           fetch-depth: 0

       - name: Setup conda
-        uses: mamba-org/setup-micromamba@v1
+        uses: conda-incubator/setup-miniconda@v3
         with:
           environment-file: ci/env.yaml
-          create-args: >-
-            python=${{ matrix.PY }}
+          python-version: ${{ matrix.PY }}

[arogozhnikov]

feel free to make these/any other changes yourself, Github will allow you to push to this branch

[geekodour]

@martindurant is it possible to use this change without a release happening? I want to use this change but some dependencies use a previous version, I am not even able to install directly from git.

Eg. Because datasets (2.20.0) depends on fsspec[http] (>=2023.1.0,<=2024.5.0)

[martindurant]

Assuming datasets doesn't actually have conflicting calls with the current codebase, you can always install s3fs with --no-deps (I think all the installers accept this flag).
If datasets actually tests the package metadata, you could fool it with

pip install datasets # grabs old version of s3fs
git clone https:/fsspec/s3fs/
cd s3fs
git checkout 2024.3.1
pip install -e .
git checkout main

pip will think it has 2024.3.1, but will use the current code. Of course, you might want to do the same with fsspec too.

Note that I intend to make a release perhaps yet this week.