(POOLER-170) Revise vmpooler usage stats

Break down the usage stats into smaller groups so as to manage the
number of stat lines collected for Prometheus.

This may need some further revision to filter out Litmus stats, or
otherwise collect litmus usage information.

lib/vmpooler/pool_manager.rb

@@ -491,15 +491,16 @@ module Vmpooler
       return if checkout.nil?
 
       user ||= 'unauthenticated'
-      unless jenkins_build_url
-        user = user.gsub('.', '_')
-        $metrics.increment("usage.#{user}.#{poolname}")
-        return
-      end
+      user = user.gsub('.', '_')
+      $metrics.increment("user.#{user}.#{poolname}")
 
+      return unless jenkins_build_url
+
+      # TBD - Add Filter for Litmus here as well - to ignore for the moment.
       url_parts = jenkins_build_url.split('/')[2..-1]
-      instance = url_parts[0]
+      jenkins_instance = url_parts[0].gsub('.', '_')
       value_stream_parts = url_parts[2].split('_')
+      value_stream_parts = value_stream_parts.map { |s| s.gsub('.', '_') }
       value_stream = value_stream_parts.shift
       branch = value_stream_parts.pop
       project = value_stream_parts.shift
@@ -507,22 +508,9 @@ module Vmpooler
       build_metadata_parts = url_parts[3]
       component_to_test = component_to_test('RMM_COMPONENT_TO_TEST_NAME', build_metadata_parts)
 
-      metric_parts = [
-        'usage',
-        user,
-        instance,
-        value_stream,
-        branch,
-        project,
-        job_name,
-        component_to_test,
-        poolname
-      ]
-
-      metric_parts = metric_parts.reject(&:nil?)
-      metric_parts = metric_parts.map { |s| s.gsub('.', '_') }
-
-      $metrics.increment(metric_parts.join('.'))
+      $metrics.increment("usage_jenkins_instance.#{jenkins_instance}.#{value_stream}.#{poolname}")
+      $metrics.increment("usage_branch_project.#{branch}.#{project}.#{poolname}")
+      $metrics.increment("usage_job_component.#{job_name}.#{component_to_test}.#{poolname}")
     rescue StandardError => e
       $logger.log('d', "[!] [#{poolname}] failed while evaluating usage labels on '#{vm}' with an error: #{e}")
       raise
@@ -537,7 +525,7 @@ module Vmpooler
         next if value.nil?
         return value if key == match
       end
-      nil
+      'none'
     end
 
     def purge_unused_vms_and_folders