A simple metric capturing mechanism to expose metrics to queries

Author: henningandersen

server/src/main/java/org/elasticsearch/index/store/MetricHolder.java

@@ -10,7 +10,7 @@
 package org.elasticsearch.index.store;
 
 public interface MetricHolder<M> {
-    static <M> MetricHolder<M> noop() {
+    static <M> MetricHolder<M> noop(M noopData) {
         return new MetricHolder<>() {
 
             @Override
@@ -20,8 +20,7 @@ public MetricHolder<M> singleThreaded() {
 
             @Override
             public M instance() {
-                // todo fix this
-                return null;
+                return noopData;
             }
         };
     }

server/src/main/java/org/elasticsearch/index/store/StoreMetrics.java

@@ -10,6 +10,12 @@
 package org.elasticsearch.index.store;
 
 public class StoreMetrics {
+    public static final MetricHolder<StoreMetrics> NOOP_HOLDER = MetricHolder.noop(new StoreMetrics() {
+        @Override
+        public void addBytesRead(long amount) {
+        }
+    });
+
     private long bytesRead;
 
     public long getBytesRead() {

server/src/test/java/org/elasticsearch/index/IndexModuleTests.java

@@ -84,6 +84,7 @@
 import org.elasticsearch.index.store.FsDirectoryFactory;
 import org.elasticsearch.index.store.MetricHolder;
 import org.elasticsearch.index.store.Store;
+import org.elasticsearch.index.store.StoreMetrics;
 import org.elasticsearch.indices.IndicesModule;
 import org.elasticsearch.indices.IndicesQueryCache;
 import org.elasticsearch.indices.TestIndexNameExpressionResolver;
@@ -265,7 +266,7 @@ public void testWrapperIsBound() throws IOException {
             new IndexingStatsSettings(ClusterSettings.createBuiltInClusterSettings()),
             new SearchStatsSettings(ClusterSettings.createBuiltInClusterSettings()),
             MergeMetrics.NOOP,
-            MetricHolder.noop()
+            StoreMetrics.NOOP_HOLDER
         );
         module.setReaderWrapper(s -> new Wrapper());
 
@@ -297,7 +298,7 @@ public void testRegisterIndexStore() throws IOException {
             new IndexingStatsSettings(ClusterSettings.createBuiltInClusterSettings()),
             new SearchStatsSettings(ClusterSettings.createBuiltInClusterSettings()),
             MergeMetrics.NOOP,
-            MetricHolder.noop()
+            StoreMetrics.NOOP_HOLDER
         );
 
         final IndexService indexService = newIndexService(module);
@@ -327,7 +328,7 @@ public void testDirectoryWrapper() throws IOException {
             new IndexingStatsSettings(ClusterSettings.createBuiltInClusterSettings()),
             new SearchStatsSettings(ClusterSettings.createBuiltInClusterSettings()),
             MergeMetrics.NOOP,
-            MetricHolder.noop()
+            StoreMetrics.NOOP_HOLDER
         );
 
         module.setDirectoryWrapper(new TestDirectoryWrapper());
@@ -685,7 +686,7 @@ public void testRegisterCustomRecoveryStateFactory() throws IOException {
             new IndexingStatsSettings(ClusterSettings.createBuiltInClusterSettings()),
             new SearchStatsSettings(ClusterSettings.createBuiltInClusterSettings()),
             MergeMetrics.NOOP,
-            MetricHolder.noop()
+            StoreMetrics.NOOP_HOLDER
         );
 
         final IndexService indexService = newIndexService(module);
@@ -712,7 +713,7 @@ public void testIndexCommitListenerIsBound() throws IOException, ExecutionExcept
             new IndexingStatsSettings(ClusterSettings.createBuiltInClusterSettings()),
             new SearchStatsSettings(ClusterSettings.createBuiltInClusterSettings()),
             MergeMetrics.NOOP,
-            MetricHolder.noop()
+            StoreMetrics.NOOP_HOLDER
         );
 
         final AtomicLong lastAcquiredPrimaryTerm = new AtomicLong();
@@ -819,7 +820,7 @@ private static IndexModule createIndexModule(
             new IndexingStatsSettings(ClusterSettings.createBuiltInClusterSettings()),
             new SearchStatsSettings(ClusterSettings.createBuiltInClusterSettings()),
             MergeMetrics.NOOP,
-            MetricHolder.noop()
+            StoreMetrics.NOOP_HOLDER
         );
     }