metrics: add gauge with compression goal if enabled (#18230)

Author: yaauie

docs/static/spec/openapi/logstash-api.yaml

@@ -2346,6 +2346,11 @@ components:
                     encode:
                       type: object
                       properties:
+                        goal:
+                          - enum:
+                              - speed
+                              - balanced
+                              - size
                         ratio:
                           type: object
                           description: the ratio of event size in bytes to its representation on disk

logstash-core/src/main/java/org/logstash/ackedqueue/ZstdEnabledCompressionCodec.java

@@ -4,6 +4,8 @@
 import co.elastic.logstash.api.NamespacedMetric;
 import com.github.luben.zstd.Zstd;
 
+import java.util.Locale;
+
 /**
  * A {@link ZstdEnabledCompressionCodec} is a {@link CompressionCodec} that can decode deflate-compressed
  * bytes and performs deflate compression when encoding.
@@ -34,6 +36,7 @@ public enum Goal {
         this.internalLevel = internalLevel.internalLevel;
 
         final NamespacedMetric encodeNamespace = queueMetric.namespace("compression", "encode");
+        encodeNamespace.gauge("goal", internalLevel.name().toLowerCase(Locale.ROOT));
         encodeRatioMetric = encodeNamespace.namespace("ratio")
                 .register("lifetime", AtomicIORatioMetric.FACTORY);
         encodeTimerMetric = encodeNamespace.namespace("spend")

qa/integration/specs/monitoring_api_spec.rb

@@ -208,7 +208,12 @@
   shared_examples "pipeline metrics" do
     # let(:pipeline_id) { defined?(super()) or fail NotImplementedError }
     let(:settings_overrides) do
-      super().merge({'pipeline.id' => pipeline_id})
+      super().dup.tap do |overrides|
+        overrides['pipeline.id'] = pipeline_id
+        if logstash_service.settings.feature_flag == "persistent_queues"
+          overrides['queue.compression'] = %w(none speed balanced size).sample
+        end
+      end
     end
 
     it "can retrieve queue stats" do
@@ -242,6 +247,11 @@
           queue_compression_stats = queue_stats.fetch("compression")
           expect(queue_compression_stats.dig('decode', 'ratio', 'lifetime')).to be >= 1
           expect(queue_compression_stats.dig('decode', 'spend', 'lifetime')).not_to be_nil
+          if settings_overrides['queue.compression'] != 'none'
+            expect(queue_compression_stats.dig('encode', 'goal')).to eq(settings_overrides['queue.compression'])
+            expect(queue_compression_stats.dig('encode', 'ratio', 'lifetime')).to be <= 1
+            expect(queue_compression_stats.dig('encode', 'spend', 'lifetime')).not_to be_nil
+          end
         else
           expect(queue_stats["type"]).to eq("memory")
         end