patch: add test to datasources to see if service to be graphed is available

[Mrten]

This patch adds an extra feature for the datasources, check_ds, that decides whether a datasource is to be graphed or not.

It needs to move collect_data() call to outside the if because the data should be available for the config mode of the plugin. If you care about the number of statistics-gathering queries collect_data() should cache the data it retrieves, I haven't because this is really on the edge of my Perl hacking abilities 😃.

It moves the print multigraph..-statement because it should not be printed for graphs that won't be there later on, munin gets rather confused if you do.

--- mysql   2013-05-06 18:26:07.000000000 +0200
+++ mysql.new   2013-05-14 22:29:32.317507777 +0200
@@ -227,13 +228,10 @@
     if ($command eq 'autoconf') {
         return $command_map{$command}->();
     }
     else {
-        if ($command eq 'show') {
-            collect_data();
-        }
+        collect_data();
         for my $graph (sort keys %graphs) {
-            print "multigraph mysql_$graph$instance\n";
             $command_map{$command}->($graph);
         }
     }
     return 0;
@@ -270,8 +268,21 @@

     my %conf = (%{$defaults{global_attrs}}, %{$graph->{config}{global_attrs}});
     $conf{args} .=  ' --no-gridfit --slope-mode';

+    # see if there needs to be some datasource defined
+    if ( defined ($graph->{config}{check_ds})) {
+
+        # if the datasource isn't in the data, skip this graph (query cache not enabled or smt)
+        for my $f ($graph->{config}{check_ds}) {
+            if ( !defined ($data->{$f})) {
+                return;
+            }
+        }
+    }
+
+    print "multigraph mysql_$graph_name$instance\n";
+
     while (my ($k, $v) = each %conf) {
         print "graph_$k $v\n";
     }
     print "graph_category mysql$instance\n";
@@ -301,8 +312,10 @@
 sub show {
     my $graph_name = shift;

     my $graph = $graphs{$graph_name};
+
+    print "multigraph mysql_$graph_name$instance\n";

     die "Can't show data for '$graph_name' because InnoDB is disabled."
         if $graph_name =~ /innodb_/ && $data->{_innodb_disabled};

[kjellm]

Thanks. Need to think about it. I don't have any time right now, but I will come back to it.

You can use the CHI module (https://metacpan.org/module/JSWARTZ/CHI-0.56/lib/CHI.pm) with the FastMmap driver to cache the results in collect_data().

[kjellm]

You can see how I used Cache::Cache to achieve this before I changed the plugin to use the multigraph feature: 9c1ed41