services/webhdfs: Implement multi write via CONCAT

[Xuanwo]

WebHDFS supports CONCAT to concat existing files together into one. It might be possible for us to write every chunks first and than concat them.

[hoslo]

Request assign to me

[suyanhanx]

Request assign to me

Thank you!

[shbhmrzd]

Hi, just curious can we use http chunked encoding while writing to a file to support multi-write to file?

[Xuanwo]

Hi, just curious can we use http chunked encoding while writing to a file to support multi-write to file?

WebHDFS documentation does not specify whether content-length is required to create a file; it may be worth testing.