0.18.1 reintroduces S3 multipart upload bug

[Zan-L]

Environment

Delta-rs version: 0.18.1

Binding: Python

Environment:

• Cloud provider: AWS
• OS: Linux/Windows
• Other:

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Bug

What happened: Same error as #890 but on S3 directly instead of non-S3

What you expected to happen:

How to reproduce it: Write regular size data to S3 with write_deltalake()

More details: 0.18.0 works fine

[abhiaagarwal]

Can you give a reproducible example / any details about the size of the table / amount of writes? A log report? I wrote the modified code for 0.18.1 and it seems to have fixed other people's problems — I'll take a look at it :)

[Zan-L]

Hi,

Thank you for the prompt response. Unfortunately, that happened in our enterprise dev environment so I can't provide the proprietary data. I can provide two more observations though:

• Extreme small data (less than thousands of rows) could still be written into S3, but after a certain threshold everything fails with that multipart upload error.
• I checked the 0.18.1 change source code and there does seem to be removal of the old multipart upload related code. Maybe that old code contained the fix and a search with key word "multipart" is good to start with.

[abhiaagarwal]

Understandable if you can't share enterprise data, but even a censored error code/log would be great!

But yeah, the behavior in 0.18.1 changed so that any writes buffer into an in-memory buffer, which flushes when it exceeds the threshold set. The threshold per the config is const DEFAULT_MAX_BUFFER_SIZE: usize = 4 * 1024 * 1024 ~ 4 MiB. Can you try tuning it higher by setting max_buffer_size key the storage_options dict when loading a table to a higher value?

object_store documentation says it should be at least 5 MiB, so this value should probably be tuned on our side anyways.

[Zan-L]

That is the root cause. I did a test write with 5*2**20 and it worked this time. Can you push another release with this fix?

Btw, the error message from before:

OSError: Generic S3 error: Error performing complete multipart request: Client error with status 400 Bad Request: <Error><Code>EntityTooSmall</Code><Message>Your proposed upload is smaller than the minimum allowed size</Message><ProposedSize>4328982</ProposedSize><MinSizeAllowed>5242880</MinSizeAllowed><PartNumber>1</PartNumber>

[abhiaagarwal]

I don't control the release cycles, but you can compile from source with that fix! The current version will also work if you set that option.