[sheepdog] [PATCH RFC 5/5] sheep: retry when connect() or accept() fails with EMFILE

[Hitoshi Mitake]

At Wed, 17 Jul 2013 16:56:10 +0800,
Liu Yuan wrote:
> 
> On Fri, Jul 12, 2013 at 10:54:26AM +0900, Hitoshi Mitake wrote:
> > This patch adds calling of shrink_sockfd() after connect() and
> > accept() when they return EMFILE.
> > 
> > These retries can be invoked twice at a maximum. This policy must be
> > improved in the future.
> > 
> > Signed-off-by: Hitoshi Mitake <mitake.hitoshi at lab.ntt.co.jp>
> > ---
> >  sheep/request.c      |    7 +++++++
> >  sheep/sockfd_cache.c |    6 ++++++
> >  2 files changed, 13 insertions(+)
> > 
> > diff --git a/sheep/request.c b/sheep/request.c
> > index 3b43c76..8f3f840 100644
> > --- a/sheep/request.c
> > +++ b/sheep/request.c
> > @@ -828,8 +828,15 @@ static void listen_handler(int listen_fd, int events, void *data)
> >  	}
> >  
> >  	namesize = sizeof(from);
> > +
> > +	int retry = 2;
> > +retry_accept:
> >  	fd = accept(listen_fd, (struct sockaddr *)&from, &namesize);
> >  	if (fd < 0) {
> > +		if (errno == EMFILE && retry--) {
> > +			if (shrink_sockfd())
> > +				goto retry_accept;
> > +		}
> >  		sd_eprintf("failed to accept a new connection: %m");
> >  		return;
> 
> Better use xaccept() to handle retry accept internally and document why 2.

I don't have the reason of 2, currently. I'd like to profile sheep
with tools like LTTng or perf and seek better retry count later.

We shouldn't use x prefix for retrying versions of socket producing
functions. Because many x prefixed functions are in libsheepdog and
the retrying functions cannot be moved to libsheepdog. They depends on
sockfd.

Thanks,
Hitoshi