[Pkg-systemd-maintainers] Bug#732157: Fwd: Bug#732157: Want SIGSTOP-style daemon/service readiness notification

[Shawn Landden]

forwarding to systemd-devel for discussion


---------- Forwarded message ----------
From: Ian Jackson <ijackson at chiark.greenend.org.uk>
Date: Sat, Dec 14, 2013 at 1:05 PM
Subject: [Pkg-systemd-maintainers] Bug#732157: Want SIGSTOP-style
daemon/service readiness notification
To: submit at bugs.debian.org


Package: systemd
Version: 204-5
Severity: wishlist

It would be nice if systemd could implement the service supervisor
side of the service readiness protocol that upstart calls "expect
stop":

The service doesn't fork, and when considers itself ready it raises
SIGSTOP.  The supervisor can observe this via the usual mechanisms,
being the service's parent, and when it occurs it sends the service
CONT and starts whatever was waiting for readiness.

The sd_notify(3) protocol is just about tolerable, and it is good that
it's documented, but it is quite unattractive for a daemon author:
Either they have to add a build- and runtime- dependency on a
systemd-specific library, or they have to reimplement a fairly tedious
piece of socket code.

For a daemon author, raise(SIGSTOP) is lovely and simple.

I guess this would be a new "Type" (but I'm still halfway through the
docs so no expert).

Ian.

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