Re: "IMAP IDLE"-like long-polling "git fetch"

[Stefan Beller <sbeller@google.com>]

On Fri, Dec 28, 2018 at 8:39 PM Konstantin Ryabitsev
<konstantin@linuxfoundation.org> wrote:
>
> On Sat, Dec 29, 2018 at 03:56:21AM +0000, Eric Wong wrote:
> > Hey all, I just added this to the TODO file for public-inbox[1] but
> > obviously it's intended for git.git (meta@public-inbox cc-ed):
> >
> > > +* Contribute something like IMAP IDLE for "git fetch".
> > > +  Inboxes (and any git repos) can be kept up-to-date without
> > > +  relying on polling.
> >
> > I would've thought somebody had done this by now, but I guess
> > it's dependent on a bunch of things (TLS layer nowadays, maybe
> > HTTP/2), so git-daemon support alone wouldn't cut it...
>
> Polling is not all bad, especially for large repository collections.

I disagree with that statement.

IIRC, More than half the bandwidth of Googles git servers are used
for ls-remote calls (i.e. polling a lot of repos, most of them did *not*
change, by build bots which are really eager to try again after a minute).

That is why we use a superproject, with all other repositories as
a submodule for polling, as that would slash the ls-remote traffic
approximately by the number of repositories.

There was an attempt in JGit to support this type of communication
of long polling at
https://git.eclipse.org/r/plugins/gitiles/jgit/jgit/+/2adc572628f9382ace5fbd791325dc64f7c968d3
but not a whole lot is left over in JGit as it was refactored at least
once again.

IIRC the issues where in the lack of protocol definition that made it
usable for a wider audience.