[PATCH] write the daemon's pid to a file.

[PATCH] write the daemon's pid to a file.

[John Darrington]

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I don't know what you will think of this patch.  But I found that it makes 
running guix under debian a whole lot easier.  I suspect the same will be
true for many other OSes too.

J'


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From 20f5f5c28b773bb4e6164cd4e8df35ef62e3dffd Mon Sep 17 00:00:00 2001
From: John Darrington <john@darrington.wattle.id.au>
Date: Sat, 30 Nov 2013 15:30:48 +0100
Subject: [PATCH] guix-daemon: New option --pid-file=FILE

* Added a new option to write the daemon's pid to a file.  This is
necessary for the clean integration into sysV like systems such as
used by Debian and other vendors.
---
 nix/nix-daemon/guix-daemon.cc |    9 +++++++++
 nix/sync-with-upstream        |   16 ++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/nix/nix-daemon/guix-daemon.cc b/nix/nix-daemon/guix-daemon.cc
index 4f9fa4c..d703324 100644
--- a/nix/nix-daemon/guix-daemon.cc
+++ b/nix/nix-daemon/guix-daemon.cc
@@ -67,6 +67,7 @@ builds derivations on behalf of its clients.";
 #define GUIX_OPT_CHROOT_DIR 10
 #define GUIX_OPT_LISTEN 11
 #define GUIX_OPT_NO_SUBSTITUTES 12
+#define GUIX_OPT_PID_FILE 13
 
 static const struct argp_option options[] =
   {
@@ -94,6 +95,8 @@ static const struct argp_option options[] =
       "Perform builds as a user of GROUP" },
     { "no-substitutes", GUIX_OPT_NO_SUBSTITUTES, 0, 0,
       "Do not use substitutes" },
+    { "pid-file", GUIX_OPT_PID_FILE, "FILE", 0,
+      "Write the daemon's process ID to FILE" },
     { "cache-failures", GUIX_OPT_CACHE_FAILURES, 0, 0,
       "Cache build failures" },
     { "lose-logs", GUIX_OPT_LOSE_LOGS, 0, 0,
@@ -171,6 +174,9 @@ parse_opt (int key, char *arg, struct argp_state *state)
     case GUIX_OPT_SYSTEM:
       settings.thisSystem = arg;
       break;
+    case GUIX_OPT_PID_FILE:
+      settings.nixDaemonPidFile = arg;
+      break;
     default:
       return (error_t) ARGP_ERR_UNKNOWN;
     }
@@ -247,6 +253,9 @@ main (int argc, char *argv[])
       printMsg (lvlDebug,
 		format ("listening on `%1%'") % settings.nixDaemonSocketFile);
 
+      if (settings.nixDaemonPidFile != "")
+	writeFile (settings.nixDaemonPidFile, int2String(getpid()));
+
       run (nothing);
     }
   catch (std::exception &e)
diff --git a/nix/sync-with-upstream b/nix/sync-with-upstream
index 535763d..d60406f 100755
--- a/nix/sync-with-upstream
+++ b/nix/sync-with-upstream
@@ -70,3 +70,19 @@ cp -v "$top_srcdir/nix-upstream/AUTHORS" "$top_srcdir/nix"
 # Substitutions.
 sed -i "$top_srcdir/nix/libstore/gc.cc"					\
     -e 's|/nix/find-runtime-roots\.pl|/guix/list-runtime-roots|g'
+
+
+patch -p 1 << EOF
+--- a/nix/libstore/globals.hh	2013-11-30 18:13:33.000000000 +0100
++++ b/nix/libstore/globals.hh	2013-11-30 18:15:32.000000000 +0100
+@@ -53,6 +53,9 @@
+     /* File name of the socket the daemon listens to.  */
+     Path nixDaemonSocketFile;
+ 
++    /* File name of the to which the daemon PID will be written.  */
++    Path nixDaemonPidFile;
++
+     /* Whether to keep temporary directories of failed builds. */
+     bool keepFailed;
+EOF
+ 
-- 
1.7.10.4


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Re: [PATCH] write the daemon's pid to a file.

[Ludovic Courtès]

John Darrington <john@darrington.wattle.id.au> skribis:

> I don't know what you will think of this patch.  But I found that it makes 
> running guix under debian a whole lot easier.  I suspect the same will be
> true for many other OSes too.

How does it help exactly?  On GNU, it’s started by dmd, which knows its PID.
I’d expect it to be the same with other init systems, no?

Thanks,
Ludo’.

Re: [PATCH] write the daemon's pid to a file.el

[John Darrington]

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Debian uses a script and a program start-stop-daemon.  FRom the man page:

       Note: unless --pidfile is specified, start-stop-daemon behaves  similar  to  killall(1).   start-stop-daemon  will  scan  the
       process  table  looking  for any processes which match the process name, uid, and/or gid (if specified). Any matching process
       will prevent --start from starting the daemon. All matching processes will be sent the TERM signal (or the one specified  via
       --signal  or --retry) if --stop is specified. For daemons which have long-lived children which need to live through a --stop,
       you must specify a pidfile.

Of course, one can get the pid by doing

 guix-daemon --blah-blah & 
 pid=$!

But the problem here is that the & means you never know when the daemon has actually started,
which leads to race conditions.  Again, there are tricks to work around that, but having the daemon 
write its own pid makes it a lot easier.

J'

On Sun, Dec 08, 2013 at 04:35:40PM +0100, Ludovic Courtès wrote:
     John Darrington <john@darrington.wattle.id.au> skribis:
     
     > I don't know what you will think of this patch.  But I found that it makes 
     > running guix under debian a whole lot easier.  I suspect the same will be
     > true for many other OSes too.
     
     How does it help exactly?  On GNU, it’s started by dmd, which knows its PID.
     I’d expect it to be the same with other init systems, no?
     
     Thanks,
     Ludo’.

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