From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.comp.sysutils.supervision.general/2924 Path: news.gmane.io!.POSTED.ciao.gmane.io!not-for-mail From: "Serge E. Hallyn" Newsgroups: gmane.comp.sysutils.supervision.general Subject: Re: Readiness notification exemplars Date: Wed, 1 Apr 2020 09:21:22 -0500 Message-ID: <20200401142122.GA30742@mail.hallyn.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Info: ciao.gmane.io; posting-host="ciao.gmane.io:159.69.161.202"; logging-data="77446"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Mutt/1.9.4 (2018-02-28) Cc: Supervision To: Brett Neumeier Original-X-From: supervision-return-2513-gcsg-supervision=m.gmane-mx.org@list.skarnet.org Wed Apr 01 16:21:31 2020 Return-path: Envelope-to: gcsg-supervision@m.gmane-mx.org Original-Received: from alyss.skarnet.org ([95.142.172.232]) by ciao.gmane.io with smtp (Exim 4.92) (envelope-from ) id 1jJeFH-000K0k-7e for gcsg-supervision@m.gmane-mx.org; Wed, 01 Apr 2020 16:21:31 +0200 Original-Received: (qmail 13008 invoked by uid 89); 1 Apr 2020 14:21:57 -0000 Mailing-List: contact supervision-help@list.skarnet.org; run by ezmlm Original-Sender: Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Original-Received: (qmail 13001 invoked from network); 1 Apr 2020 14:21:57 -0000 Content-Disposition: inline In-Reply-To: Xref: news.gmane.io gmane.comp.sysutils.supervision.general:2924 Archived-At: I've been considering for several years trying to push a kernel patch which would provide a way for userspace to find out when someone starts listening on some port. Based on problems I saw long ago in the late days of upstart and early days of systemd, that seemed like it would solve a not infrequent problem without having to make any changes to the daemons. Upstart tried to solve it by making the daemons send a sigstop when ready; systemd solves it by making the daemons support socket notification; listen-notifiers could be entirely handled by the dependency handler in the init system. It's *still* on my list of todos. Maybe sufficient ridicule here will help me knock it off the list :) On Wed, Apr 01, 2020 at 08:23:26AM -0500, Brett Neumeier wrote: > I read on http://skarnet.org/software/s6/notifywhenup.html: > > "...daemons can simply write a line to a file descriptor of their choice, > then close that file descriptor, when they're ready to serve. This is a > generic mechanism that some daemons already implement." > > I am curious, does anyone on this list know of examples of such daemons? I > am considering creating and submitting patches for some daemon programs > that I use that do *not* support this mechanism as yet, and am curious if > it is as simple as it looks like it should be. > > Cheers! > > Brett > > -- > Brett Neumeier (bneumeier@gmail.com)