Ability to abort the `write` operation with `Writer`.

[damooo]

Currently Writer supports writing in multiple chunks through streaming manner.

It only provides append and close apis.

But it is highly probable that, after few chunks, fallible source stream may raise error. In that case we have to abort the write op. Currently Writer provides no api for that.

Previous multipart api has the ability to cancel the write op.

[v0y4g3r]

@Xuanwo Could you please assign this to me?

[suyanhanx]

@Xuanwo Could you please assign this to me?

I have assigned it to you. Have fun!

[v0y4g3r]

After investigated the code of writers, it turns out that Writer::append has two kinds of implementations, one is based on multipart upload (mostly object storage backends like S3) and the other is based on posix-like APIs, like FsWriter, FtpWriter and HdfsWriter. While in the latter, some writer has "atomic write" features (FsWriter). So:

• For S3-like backends, Writer::abort is meaningful in that partially uploaded objects will also be charged for storage.
• For posix-like backends with atomic write enabled, Writer::abort is meaningful in that partial files are stored in a temp directory and cleaning that directory on abortion is necessary.
• For posix-like backends without atomic write feature,Writer::append directly appends bytes to orignal files. I wonder if it's ok to delete partial files on abortion?

Please let me know if you guys have any idea on that.

[Xuanwo]

Please let me know if you guys have any idea on that.

Looks good to me!

Please be aware that adding a new API in writer may be complex, which is why this issue has not been marked as a good first issue. If you have any questions, I am available to help. Enjoy!

[suyanhanx]

Please let me know if you guys have any idea on that.

Your ideas are very reasonable! LGTM!

[Xuanwo]

Already implemented. Thanks @v0y4g3r!