netdev - Re: [PATCH 1/1] net: Add SO_REUSEPORT_LISTEN

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Message-ID: <1443315842.3273.3.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Sat, 26 Sep 2015 18:04:02 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Tolga Ceylan <tolga.ceylan@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH 1/1] net: Add SO_REUSEPORT_LISTEN_OFF socket option as
 drain mode

On Sat, 2015-09-26 at 17:30 -0700, Tolga Ceylan wrote:
> For applications using SO_REUSEPORT listeners, there is
> no clean way to switch traffic on/off or add/remove
> listeners without dropping pending connections. With this
> patch, applications can turn off queueing of new connections
> for a specific listener socket which enables implementation of
> zero down time server applications.
> 
> For example, a popular web server nginx handles application
> configuration changes by forking new processes (listeners)
> and waiting for old processes (listeners) to finish up their
> processing. However, this approach is distruptive as removal
> of a listener will drop pending connections for that listener.
> Instead, with this patch, nginx can maintain two sets of listener
> socket pools to be used by old/new processes and switch traffic off/on
> using this socket option. Old processes set set this socket option
> to drain their existing queues.

What about listen(fd, 0) ?

Not sure we need to add a new socket option.

It makes sense to extend reuseport logic to ignore listeners with a 0
backlog (if not already done, I did not check)





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