Added tag-parts, suffixes and prefixes

Signed-off-by: Jesper Söderlund <jesper.soderlund@klarna.com>

Author: Jesper Söderlund

spec/fluent/plugin/filter_prometheus_spec.rb

@@ -2,9 +2,10 @@
 require 'fluent/test/driver/filter'
 require 'fluent/plugin/filter_prometheus'
 require_relative 'shared'
+require 'json'
 
 describe Fluent::Plugin::PrometheusFilter do
-  let(:tag) { 'prometheus.test' }
+  let(:tag) { 'prometheus.test.additional.parts' }
   let(:driver) { Fluent::Test::Driver::Filter.new(Fluent::Plugin::PrometheusFilter).configure(config) }
   let(:registry) { ::Prometheus::Client.registry }
 
@@ -32,7 +33,4 @@
         expect(es.first).to eq(message)
       end
     end
-
-    it_behaves_like 'instruments record'
-  end
 end

spec/fluent/plugin/shared.rb

@@ -83,11 +83,15 @@
     key foo
     <labels>
       foo ${foo}
+      the_prefix ${tag_prefix[2]}
+      another_part ${tag_parts[0]}
     </labels>
   </metric>
   <labels>
     tag ${tag}
     hostname ${hostname}
+    single_part ${tag_parts[1]}
+    the_suffix ${tag_suffix[2]}
   </labels>
 ]