Initialize with default values global events and pipeline events related metric

The metric store has no concept is a metric need to exist so as a rule
of thumb we need to defined them with 0 values and send them to the
store when we initialize something.

This PR make sure the batch object is recording the right default values

Fixes: #6449

Fixes #6450

logstash-core/lib/logstash/util/wrapped_acked_queue.rb

@@ -132,10 +132,19 @@ module LogStash; module Util
 
       def set_events_metric(metric)
         @event_metric = metric
+        define_initial_metrics_values(@event_metric)
       end
 
       def set_pipeline_metric(metric)
         @pipeline_metric = metric
+        define_initial_metrics_values(@pipeline_metric)
+      end
+
+      def define_initial_metrics_values(namespaced_metric)
+        namespaced_metric.gauge(:duration_in_millis, 0)
+        namespaced_metric.increment(:filtered, 0)
+        namespaced_metric.increment(:in, 0)
+        namespaced_metric.increment(:out, 0)
       end
 
       def inflight_batches

logstash-core/lib/logstash/util/wrapped_synchronous_queue.rb

@@ -79,10 +79,19 @@ module LogStash; module Util
 
       def set_events_metric(metric)
         @event_metric = metric
+        define_initial_metrics_values(@event_metric)
       end
 
       def set_pipeline_metric(metric)
         @pipeline_metric = metric
+        define_initial_metrics_values(@pipeline_metric)
+      end
+
+      def define_initial_metrics_values(namespaced_metric)
+        namespaced_metric.gauge(:duration_in_millis, 0)
+        namespaced_metric.increment(:filtered, 0)
+        namespaced_metric.increment(:in, 0)
+        namespaced_metric.increment(:out, 0)
       end
 
       def inflight_batches

logstash-core/spec/logstash/util/wrapped_synchronous_queue_spec.rb

@@ -63,7 +63,15 @@ describe LogStash::Util::WrappedSynchronousQueue do
             batch = read_client.take_batch
             read_client.close_batch(batch)
             store = collector.snapshot_metric.metric_store
-            expect(store.size).to eq(0)
+
+            expect(store.get_shallow(:events, :in).value).to eq(0)
+            expect(store.get_shallow(:events, :out).value).to eq(0)
+            expect(store.get_shallow(:events, :filtered).value).to eq(0)
+            expect(store.get_shallow(:events, :duration_in_millis).value).to eq(0)
+            expect(store.get_shallow(:pipeline, :in).value).to eq(0)
+            expect(store.get_shallow(:pipeline, :duration_in_millis).value).to eq(0)
+            expect(store.get_shallow(:pipeline, :out).value).to eq(0)
+            expect(store.get_shallow(:pipeline, :filtered).value).to eq(0)
           end
         end
 
@@ -73,15 +81,22 @@ describe LogStash::Util::WrappedSynchronousQueue do
             5.times {|i| batch.push("value-#{i}")}
             write_client.push_batch(batch)
             read_batch = read_client.take_batch
-            sleep(0.1) # simulate some work?
-            read_client.close_batch(batch)
+            sleep(0.1) # simulate some work for the `duration_in_millis`
+            # TODO: this interaction should be cleaned in an upcoming PR,
+            # This is what the current pipeline does.
+            read_client.add_filtered_metrics(read_batch)
+            read_client.add_output_metrics(read_batch)
+            read_client.close_batch(read_batch)
             store = collector.snapshot_metric.metric_store
 
-            expect(store.size).to eq(4)
             expect(store.get_shallow(:events, :in).value).to eq(5)
+            expect(store.get_shallow(:events, :out).value).to eq(5)
+            expect(store.get_shallow(:events, :filtered).value).to eq(5)
             expect(store.get_shallow(:events, :duration_in_millis).value).to be > 0
             expect(store.get_shallow(:pipeline, :in).value).to eq(5)
             expect(store.get_shallow(:pipeline, :duration_in_millis).value).to be > 0
+            expect(store.get_shallow(:pipeline, :out).value).to eq(5)
+            expect(store.get_shallow(:pipeline, :filtered).value).to eq(5)
           end
         end
       end