Add 'guix offload' as a daemon build hook.

* nix/nix-daemon/guix-daemon.cc (GUIX_OPT_NO_BUILD_HOOK): New macro.
  (options): Add '--no-build-hook'.
  (parse_opt): Handle it.
  (main)[HAVE_DAEMON_OFFLOAD_HOOK]: Set 'useBuildHook' by default.
  Set $NIX_BUILD_HOOK to our offload hook unless otherwise specified.
  [!HAVE_DAEMON_OFFLOAD_HOOK]: Clear 'useBuildHook'.
* pre-inst-env.in: Set and export NIX_BUILD_HOOK.
* nix/scripts/offload.in, guix/scripts/offload.scm: New files.
* guix/ui.scm (show-guix-help)[internal?]: Add "offload".
* config-daemon.ac: Call 'GUIX_CHECK_UNBUFFERED_CBIP'.
  Instantiate 'nix/scripts/offload'.  Set 'BUILD_DAEMON_OFFLOAD'
  conditional, and optionally define 'HAVE_DEAMON_OFFLOAD_HOOK' cpp
  macro.
* daemon.am (nodist_pkglibexec_SCRIPTS)[BUILD_DAEMON_OFFLOAD]: Add it.
* Makefile.am (MODULES)[BUILD_DAEMON_OFFLOAD]: Add
  'guix/scripts/offload.scm'.
  (EXTRA_DIST)[!BUILD_DAEMON_OFFLOAD]: Likewise.
* m4/guix.m4 (GUIX_CHECK_UNBUFFERED_CBIP): New macro.
* doc/guix.texi (Setting Up the Daemon): Move most of the body to...
  (Build Environment Setup): ... this.  New subsection.
  (Daemon Offload Setup): New subsection.

2 files changed, 33 insertions, 1 deletions

diff --git a/nix/nix-daemon/guix-daemon.cc b/nix/nix-daemon/guix-daemon.cc
index cf87e39354..d35b1cd076 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 Ludovic Courtès <ludo@gnu.org>
+   Copyright (C) 2012, 2013, 2014 Ludovic Courtès <ludo@gnu.org>
 
    This file is part of GNU Guix.
 
@@ -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_NO_BUILD_HOOK 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" },
+    { "no-build-hook", GUIX_OPT_NO_BUILD_HOOK, 0, 0,
+      "Do not use the 'build hook'" },
     { "cache-failures", GUIX_OPT_CACHE_FAILURES, 0, 0,
       "Cache build failures" },
     { "lose-logs", GUIX_OPT_LOSE_LOGS, 0, 0,
@@ -159,6 +162,9 @@ parse_opt (int key, char *arg, struct argp_state *state)
     case GUIX_OPT_NO_SUBSTITUTES:
       settings.useSubstitutes = false;
       break;
+    case GUIX_OPT_NO_BUILD_HOOK:
+      settings.useBuildHook = false;
+      break;
     case GUIX_OPT_DEBUG:
       verbosity = lvlDebug;
       break;
@@ -226,6 +232,21 @@ main (int argc, char *argv[])
       settings.substituters.clear ();
       settings.useSubstitutes = true;
 
+#ifdef HAVE_DAEMON_OFFLOAD_HOOK
+      /* Use our build hook for distributed builds by default.  */
+      settings.useBuildHook = true;
+      if (getenv ("NIX_BUILD_HOOK") == NULL)
+	{
+	  std::string build_hook;
+
+	  build_hook = settings.nixLibexecDir + "/guix/offload";
+	  setenv ("NIX_BUILD_HOOK", build_hook.c_str (), 1);
+	}
+#else
+      /* We are not installing any build hook, so disable it.  */
+      settings.useBuildHook = false;
+#endif
+
       argp_parse (&argp, argc, argv, 0, 0, 0);
 
       if (settings.useSubstitutes)
diff --git a/nix/scripts/offload.in b/nix/scripts/offload.in
new file mode 100644
index 0000000000..50faed31c0
--- /dev/null
+++ b/nix/scripts/offload.in
@@ -0,0 +1,11 @@
+#!@SHELL@
+# A shorthand for "guix offload", for use by the daemon.
+
+if test "x$GUIX_UNINSTALLED" = "x"
+then
+    prefix="@prefix@"
+    exec_prefix="@exec_prefix@"
+    exec "@bindir@/guix" offload "$@"
+else
+    exec guix offload "$@"
+fi