Re: [PATCH 1/2] daemon: add tests

[Jakub Narebski <jnareb@gmail.com>]

On Thu, 5 Jan 2012, Jeff King wrote:
> On Wed, Jan 04, 2012 at 06:24:16PM -0800, Jakub Narebski wrote:
> 
> > Jeff King <peff@peff.net> writes:
> > 
> > > As a side note, it looks like we just start the daemon with "git daemon
> > > &". Doesn't that create a race condition with the tests which
> > > immediately try to access it (i.e., the first test may run before the
> > > daemon actually opens the socket)?
> > 
> > Hmmm... perhaps the trick that git-instaweb does for "plackup" web
> > server would be of use here, waiting for socket to be ready?
> 
> It looks like it busy loops, which is kind of ugly.

Well, as far as I know you can wait for data on socket or pipe, but
you can't wait for socket to be created.

Anyway this busy-wait is not too busy, and it is better than just
adding 'sleep 1' in testsuite.

> The credential-cache helper has a similar problem. It wants to kick off
> a daemon if one is not already running, and then connect to it. So the
> daemon does:
> 
>   printf("ok\n");
>   fclose(stdout);
> 
> when it has set up the socket, and the client does:
> 
>   r = read_in_full(daemon.out, buf, sizeof(buf));
>   if (r < 0)
>           die_errno("unable to read result code from cache daemon");
>   if (r != 3 || memcmp(buf, "ok\n", 3))
>           die("cache daemon did not start: %.*s", r, buf);
>   /* now we can connect over the socket */
> 
> We could probably add a "--notify-when-ready" option to git-daemon to
> do something similar.

What would git-daemon do what it is ready?  Write to socket, raise signal,
print to STDOUT / STDERR?

BTW. I wonder if it would be worth it to add something a la systemd
trick creating sockets first to git-daemon.  Adding systemd support
doesn't make sense for daemon that is to be run from inetd / xinetd,
I guess.

-- 
Jakub Narebski
Poland