range requests and multipart responses

James Tucker jftucker at gmail.com
Tue Jul 20 05:21:15 EDT 2010

On 20 Jul 2010, at 07:18, Eric Wong wrote:

> Hi all,
> Does anybody have real-world use cases of clients using Range: requests
> with multiple comma-delimited byte ranges (and thus expecting multipart
> responses)?  If not, I'm not going to bloat Rainbows! with it for now[1].
> While being able to specify a single range is very useful for resuming
> failed downloads and for things who want to "peek" at magic patterns
> before requesting the rest of a file, I can't think of good use cases
> for having to deal with multipart responses.
> Even if you were writing a FUSE-based filesystem over HTTP, it wouldn't
> even be useful for implementing preadv(2) since you can only specify a
> single offset there.
> Maybe if you mmap() a FUSE-ed file and two threads access the same file
> in different parts at the *exact*same*time* the FUSE layer could be
> smart enough to make a single HTTP request instead of two? :)
> [1] - For the performance-minded, it's also tough to implement multipart
>      responses efficiently using any sendfile() implementation.
>      Our TCP_CORK support is far from optimal under Linux right now,
>      and not using TCP_CORK would be even less efficient with extra
>      multipart headers.  AFAIK, sendfilev() isn't available outside of
>      Solaris, either.

Does cork even help in real world use cases?

> -- 
> Eric Wong
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