added test entries metric for on heap

server/src/main/java/org/opensearch/index/cache/request/RequestCacheStats.java

@@ -52,6 +52,7 @@ public class RequestCacheStats implements Writeable, ToXContentFragment {
     private long evictions;
     private long hitCount;
     private long missCount;
+    private long entries; // number of entries in the cache
 
     public RequestCacheStats() {}
 
@@ -60,20 +61,23 @@ public RequestCacheStats(StreamInput in) throws IOException {
         evictions = in.readVLong();
         hitCount = in.readVLong();
         missCount = in.readVLong();
+        entries = in.readVLong();
     }
 
-    public RequestCacheStats(long memorySize, long evictions, long hitCount, long missCount) {
+    public RequestCacheStats(long memorySize, long evictions, long hitCount, long missCount, long entries) { //
         this.memorySize = memorySize;
         this.evictions = evictions;
         this.hitCount = hitCount;
         this.missCount = missCount;
+        this.entries = entries;
     }
 
     public void add(RequestCacheStats stats) {
         this.memorySize += stats.memorySize;
         this.evictions += stats.evictions;
         this.hitCount += stats.hitCount;
         this.missCount += stats.missCount;
+        this.entries += stats.entries;
     }
 
     public long getMemorySizeInBytes() {
@@ -96,12 +100,17 @@ public long getMissCount() {
         return this.missCount;
     }
 
+    public long getEntries() {
+        return this.entries;
+    }
+
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         out.writeVLong(memorySize);
         out.writeVLong(evictions);
         out.writeVLong(hitCount);
         out.writeVLong(missCount);
+        out.writeVLong(entries);
     }
 
     @Override
@@ -111,6 +120,7 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
         builder.field(Fields.EVICTIONS, getEvictions());
         builder.field(Fields.HIT_COUNT, getHitCount());
         builder.field(Fields.MISS_COUNT, getMissCount());
+        builder.field(Fields.ENTRIES, getEntries());
         builder.endObject();
         return builder;
     }
@@ -127,5 +137,6 @@ static final class Fields {
         static final String EVICTIONS = "evictions";
         static final String HIT_COUNT = "hit_count";
         static final String MISS_COUNT = "miss_count";
+        static final String ENTRIES = "entries";
     }
 }

server/src/main/java/org/opensearch/index/cache/request/ShardRequestCache.java

@@ -65,7 +65,8 @@ public RequestCacheStats stats(TierType tierType) {
             statsHolder.get(tierType).totalMetric.count(),
             statsHolder.get(tierType).evictionsMetric.count(),
             statsHolder.get(tierType).hitCount.count(),
-            statsHolder.get(tierType).missCount.count()
+            statsHolder.get(tierType).missCount.count(),
+            statsHolder.get(tierType).entries.count()
         );
     }
 
@@ -74,17 +75,20 @@ public RequestCacheStats overallStats() {
         long totalEvictions = 0;
         long totalHits = 0;
         long totalMisses = 0;
+        long totalEntries = 0;
         for (TierType tierType : TierType.values()) {
             totalSize += statsHolder.get(tierType).totalMetric.count();
             totalEvictions += statsHolder.get(tierType).evictionsMetric.count();
             totalHits += statsHolder.get(tierType).hitCount.count();
             totalMisses += statsHolder.get(tierType).missCount.count();
+            totalEntries += statsHolder.get(tierType).entries.count();
         }
         return new RequestCacheStats(
             totalSize,
             totalEvictions,
             totalHits,
-            totalMisses
+            totalMisses,
+            totalEntries
         );
     }
 
@@ -98,6 +102,7 @@ public void onMiss(TierType tierType) {
 
     public void onCached(Accountable key, BytesReference value, TierType tierType) {
         statsHolder.get(tierType).totalMetric.inc(key.ramBytesUsed() + value.ramBytesUsed());
+        statsHolder.get(tierType).entries.inc();
     }
 
     public void onRemoval(Accountable key, BytesReference value, boolean evicted, TierType tierType) {
@@ -112,6 +117,7 @@ public void onRemoval(Accountable key, BytesReference value, boolean evicted, Ti
             dec += value.ramBytesUsed();
         }
         statsHolder.get(tierType).totalMetric.dec(dec);
+        statsHolder.get(tierType).entries.dec();
     }
 
     static class StatsHolder implements Serializable {
@@ -120,5 +126,6 @@ static class StatsHolder implements Serializable {
         final CounterMetric totalMetric = new CounterMetric();
         final CounterMetric hitCount = new CounterMetric();
         final CounterMetric missCount = new CounterMetric();
+        final CounterMetric entries = new CounterMetric();
     }
 }