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[bug#54811,3/3] daemon: Support systemd-style socket activation.

Message ID 20220409091340.7013-3-ludo@gnu.org
State Accepted
Headers show
Series Support socket activation in 'guix publish' and 'guix-daemon' | expand

Commit Message

Ludovic Courtès April 9, 2022, 9:13 a.m. UTC 
* nix/nix-daemon/guix-daemon.cc (SD_LISTEN_FDS_START): New macro.
(systemd_activation_sockets): New function.
(main): Use it.  Remove obsolete 'printMsg' call.
* doc/guix.texi (Invoking guix-daemon): Document socket activation.
---
 doc/guix.texi                 |  6 ++++-
 nix/nix-daemon/guix-daemon.cc | 42 ++++++++++++++++++++++++++++++-----
 2 files changed, 42 insertions(+), 6 deletions(-)

Comments

M April 9, 2022, 9:29 a.m. UTC | #1 
Ludovic Courtès schreef op za 09-04-2022 om 11:13 [+0200]:
> +  if (getEnv ("LISTEN_PID") == std::to_string (getpid ()))

I thought it was name getenv, and not getEnv, and C strings cannot be
meaningfully compared with == (pointer equality), or is thi a C++-ism?

Greetings,
Maxime.
Ludovic Courtès April 9, 2022, 8:28 p.m. UTC | #2 
Maxime Devos <maximedevos@telenet.be> skribis:

> Ludovic Courtès schreef op za 09-04-2022 om 11:13 [+0200]:
>> +  if (getEnv ("LISTEN_PID") == std::to_string (getpid ()))
>
> I thought it was name getenv, and not getEnv, and C strings cannot be
> meaningfully compared with == (pointer equality), or is thi a C++-ism?

Yes, this is the equality operator on std::string.  Also, ‘getEnv’
always returns a string, possibly empty (a flaky but good-enough
interface.)

Ludo’.
diff mbox series

Patch

diff --git a/doc/guix.texi b/doc/guix.texi
index 16bd858a3b..81fec35eb7 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -1554,7 +1554,11 @@  is normally run as @code{root} like this:
 # guix-daemon --build-users-group=guixbuild
 @end example
 
-@noindent
+@cindex socket activation, for @command{guix-daemon}
+This daemon can also be started following the systemd ``socket
+activation'' protocol (@pxref{Service De- and Constructors,
+@code{make-systemd-constructor},, shepherd, The GNU Shepherd Manual}).
+
 For details on how to set it up, @pxref{Setting Up the Daemon}.
 
 @cindex chroot
diff --git a/nix/nix-daemon/guix-daemon.cc b/nix/nix-daemon/guix-daemon.cc
index 36a06a3fae..d7ab9c5e64 100644
--- a/nix/nix-daemon/guix-daemon.cc
+++ b/nix/nix-daemon/guix-daemon.cc
@@ -1,5 +1,5 @@ 
 /* GNU Guix --- Functional package management for GNU
-   Copyright (C) 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2021 Ludovic Courtès <ludo@gnu.org>
+   Copyright (C) 2012-2019, 2021-2022 Ludovic Courtès <ludo@gnu.org>
    Copyright (C) 2006, 2010, 2012, 2014 Eelco Dolstra <e.dolstra@tudelft.nl>
 
    This file is part of GNU Guix.
@@ -434,6 +434,31 @@  listening_sockets (const std::list<std::string> &options)
   return result;
 }
 
+/* First file descriptor provided at startup using systemd-style socket
+   activation.  */
+#define SD_LISTEN_FDS_START 3
+
+/* Return a list of file descriptors of listening sockets provided following
+   the systemd "socket activation" protocol.  Return the empty list if we are
+   not being socket-activated.  */
+static std::vector<int>
+systemd_activation_sockets ()
+{
+  std::vector<int> result;
+
+  if (getEnv ("LISTEN_PID") == std::to_string (getpid ()))
+    {
+      unsigned int fdCount;
+      if (string2Int (getEnv ("LISTEN_FDS"), fdCount))
+	{
+	  for (unsigned int i = 0; i < fdCount; i++)
+	    result.push_back (SD_LISTEN_FDS_START + i);
+	}
+    }
+
+  return result;
+}
+
 
 int
 main (int argc, char *argv[])
@@ -494,7 +519,17 @@  main (int argc, char *argv[])
 
       argp_parse (&argp, argc, argv, 0, 0, 0);
 
-      auto sockets = listening_sockets (listen_options);
+      auto sockets = systemd_activation_sockets ();
+      if (sockets.empty ())
+	/* We were not "socket-activated" so open the sockets specified by
+	   LISTEN_OPTIONS.  */
+	sockets = listening_sockets (listen_options);
+      else
+	printMsg (lvlInfo,
+		  format (ngettext ("socket-activated with %1% socket",
+				    "socket-activated with %1% sockets",
+				    sockets.size ()))
+		  % sockets.size ());
 
       /* Effect all the changes made via 'settings.set'.  */
       settings.update ();
@@ -531,9 +566,6 @@  using `--build-users-group' is highly recommended\n"));
 		format ("automatic deduplication set to %1%")
 		% settings.autoOptimiseStore);
 
-      printMsg (lvlDebug,
-		format ("listening on `%1%'") % settings.nixDaemonSocketFile);
-
       run (sockets);
     }
   catch (std::exception &e)