From 1c65936918f096a0730a4130a363393febcf163b Mon Sep 17 00:00:00 2001
From: Florian Forster <octo@collectd.org>
Date: Sat, 25 May 2013 10:57:58 +0200
Subject: [PATCH] src/configfile.c: Add the "AutoLoadPlugin" option.

When enabled, <Plugin ...> blocks will automatically load plugins.
Thanks to Tim Bunce for suggesting this!

Github: #333
---
 src/collectd.conf.in  |  7 +++++++
 src/collectd.conf.pod | 43 ++++++++++++++++++++++++++++++++-----------
 src/configfile.c      | 14 ++++++++++++++
 3 files changed, 53 insertions(+), 11 deletions(-)

diff --git a/src/collectd.conf.in b/src/collectd.conf.in
index b817e8c4..9e383d01 100644
--- a/src/collectd.conf.in
+++ b/src/collectd.conf.in
@@ -17,6 +17,13 @@
 #PluginDir   "@libdir@/@PACKAGE_NAME@"
 #TypesDB     "@prefix@/share/@PACKAGE_NAME@/types.db"
 
+#----------------------------------------------------------------------------#
+# When enabled, plugins are loaded automatically with the default options    #
+# when an appropriate <Plugin ...> block is encountered.                     #
+# Disabled by default.                                                       #
+#----------------------------------------------------------------------------#
+#AutoLoadPlugin false
+
 #----------------------------------------------------------------------------#
 # Interval at which to query values. This may be overwritten on a per-plugin #
 # base by using the 'Interval' option of the LoadPlugin block:               #
diff --git a/src/collectd.conf.pod b/src/collectd.conf.pod
index 326944f1..bd4b2b9b 100644
--- a/src/collectd.conf.pod
+++ b/src/collectd.conf.pod
@@ -68,17 +68,9 @@ directory for the daemon.
 
 =item B<LoadPlugin> I<Plugin>
 
-Loads the plugin I<Plugin>. There must be at least one such line or B<collectd>
-will be mostly useless.
-
-Starting with collectd 4.9, this may also be a block in which further options
-affecting the behavior of B<LoadPlugin> may be specified. The following
-options are allowed inside a B<LoadPlugin> block:
-
-  <LoadPlugin perl>
-    Globals true
-    Interval 10
-  </LoadPlugin>
+Loads the plugin I<Plugin>. This is required to load plugins, unless the
+B<AutoLoadPlugin> option is enabled (see below). Without any loaded plugins,
+I<collectd> will be mostly useless.
 
 Only the first B<LoadPlugin> statement or block for a given plugin name has any
 effect. This is useful when you want to split up the configuration into smaller
@@ -88,6 +80,22 @@ you have multiple conflicting B<LoadPlugin> blocks, e.g. when they specify
 different intervals, only one of them (the first one encountered) will take
 effect and all others will be silently ignored.
 
+B<LoadPlugin> may either be a simple configuration I<statement> or a I<block>
+with additional options, affecting the behavior of B<LoadPlugin>. A simple
+statement looks like this:
+
+ LoadPlugin "cpu"
+
+Options inside a B<LoadPlugin> block can override default settings and
+influence the way plugins are loaded, e.g.:
+
+ <LoadPlugin perl>
+   Globals true
+   Interval 60
+ </LoadPlugin>
+
+The following options are valid inside B<LoadPlugin> blocks:
+
 =over 4
 
 =item B<Globals> B<true|false>
@@ -117,6 +125,19 @@ interval, that setting will take precedence.
 
 =back
 
+=item B<AutoLoadPlugin> B<false>|B<true>
+
+When set to B<false> (the default), each plugin needs to be loaded explicitly,
+using the B<LoadPlugin> statement documented above. If a
+B<E<lt>PluginE<nbsp>...E<gt>> block is encountered and no configuration
+handling callback for this plugin has been registered, a warning is logged and
+the block is ignored.
+
+When set to B<true>, explicit B<LoadPlugin> statements are not required. Each
+B<E<lt>PluginE<nbsp>...E<gt>> block acts as if it was immediately preceded by a
+B<LoadPlugin> statement. B<LoadPlugin> statements are still required for
+plugins that don't provide any configuration, e.g. the I<Load plugin>.
+
 =item B<Include> I<Path> [I<pattern>]
 
 If I<Path> points to a file, includes that file. If I<Path> points to a
diff --git a/src/configfile.c b/src/configfile.c
index e680aba7..876ee23e 100644
--- a/src/configfile.c
+++ b/src/configfile.c
@@ -110,6 +110,7 @@ static cf_global_option_t cf_global_options[] =
 	{"ReadThreads", NULL, "5"},
 	{"WriteThreads", NULL, "5"},
 	{"Timeout",     NULL, "2"},
+	{"AutoLoadPlugin", NULL, "false"},
 	{"PreCacheChain",  NULL, "PreCache"},
 	{"PostCacheChain", NULL, "PostCache"}
 };
@@ -379,6 +380,19 @@ static int dispatch_block_plugin (oconfig_item_t *ci)
 
 	name = ci->values[0].value.string;
 
+	if (IS_TRUE (global_option_get ("AutoLoadPlugin")))
+	{
+		int status;
+
+		status = plugin_load (name, /* flags = */ 0);
+		if (status != 0)
+		{
+			ERROR ("Automatically loading plugin \"%s\" failed "
+					"with status %i.", name, status);
+			return (status);
+		}
+	}
+
 	/* Check for a complex callback first */
 	for (cb = complex_callback_head; cb != NULL; cb = cb->next)
 	{
-- 
2.30.2