Stats rework (1/3): Interfaces and implementations for tiers

plugins/cache-ehcache/src/main/java/org/opensearch/cache/EhcacheCachePlugin.java

@@ -17,6 +17,7 @@
 import org.opensearch.plugins.Plugin;
 
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
@@ -36,7 +37,8 @@ public EhcacheCachePlugin() {}
 
     @Override
     public Map<CacheStoreType, StoreAwareCache.Factory> getCacheStoreTypeMap() {
-        return Map.of(CacheStoreType.DISK, new EhcacheDiskCache.EhcacheDiskCacheFactory());
+        return new HashMap<>(); // TODO: FIX
+        //return Map.of(CacheStoreType.DISK, new EhcacheDiskCache.EhcacheDiskCacheFactory());
     }
 
     @Override

server/src/main/java/org/opensearch/common/cache/ICache.java

@@ -20,17 +20,17 @@
  * @opensearch.experimental
  */
 public interface ICache<K, V> extends Closeable {
-    V get(K key);
+    V get(ICacheKey<K> key);
 
-    void put(K key, V value);
+    void put(ICacheKey<K> key, V value);
 
-    V computeIfAbsent(K key, LoadAwareCacheLoader<K, V> loader) throws Exception;
+    V computeIfAbsent(ICacheKey<K> key, LoadAwareCacheLoader<ICacheKey<K>, V> loader) throws Exception;
 
-    void invalidate(K key);
+    void invalidate(ICacheKey<K> key);
 
     void invalidateAll();
 
-    Iterable<K> keys();
+    Iterable<ICacheKey<K>> keys();
 
     long count();
 

server/src/main/java/org/opensearch/common/cache/ICacheKey.java

@@ -0,0 +1,45 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.common.cache;
+
+
+import org.opensearch.common.cache.stats.CacheStatsDimension;
+
+import java.util.List;
+import java.util.Objects;
+
+public class ICacheKey<K> {
+    public final K key; // K must implement equals()
+    public final List<CacheStatsDimension> dimensions;
+
+    public ICacheKey(K key, List<CacheStatsDimension> dimensions) {
+        this.key = key;
+        this.dimensions = dimensions;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (o == this) {
+            return true;
+        }
+        if (o == null) {
+            return false;
+        }
+        if (o.getClass() != ICacheKey.class) {
+            return false;
+        }
+        ICacheKey other = (ICacheKey) o;
+        return key.equals(other.key) && dimensions.equals(other.dimensions);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(key, dimensions);
+    }
+}

server/src/main/java/org/opensearch/common/cache/stats/CacheStats.java

@@ -8,11 +8,44 @@
 
 package org.opensearch.common.cache.stats;
 
+import org.opensearch.core.common.io.stream.Writeable;
+
+import java.util.List;
+
 /**
- * Interface for any cache specific stats.
- * TODO: Add rest of stats like hits/misses.
+ * Interface for any cache specific stats. Allows accessing stats by total value or by dimension,
+ * and also allows updating stats.
+ * When updating stats, we take in the list of dimensions associated with the key/value pair that caused the update.
+ * This allows us to aggregate stats by dimension when accessing them.
  */
-public interface CacheStats {
-    // Provides the current number of entries in cache.
-    long count();
+public interface CacheStats extends Writeable {
+
+    // Methods to get all 5 values at once, either in total or for a specific set of dimensions.
+    CacheStatsResponse getTotalStats();
+    CacheStatsResponse getStatsByDimensions(List<CacheStatsDimension> dimensions);
+
+    // Methods to get total values.
+    long getTotalHits();
+    long getTotalMisses();
+    long getTotalEvictions();
+    long getTotalMemorySize();
+    long getTotalEntries();
+
+    // Methods to get values for a specific set of dimensions.
+    // Returns the sum of values for cache entries that match all dimensions in the list.
+    long getHitsByDimensions(List<CacheStatsDimension> dimensions);
+    long getMissesByDimensions(List<CacheStatsDimension> dimensions);
+    long getEvictionsByDimensions(List<CacheStatsDimension> dimensions);
+    long getMemorySizeByDimensions(List<CacheStatsDimension> dimensions);
+    long getEntriesByDimensions(List<CacheStatsDimension> dimensions);
+
+
+    void incrementHitsByDimensions(List<CacheStatsDimension> dimensions);
+    void incrementMissesByDimensions(List<CacheStatsDimension> dimensions);
+    void incrementEvictionsByDimensions(List<CacheStatsDimension> dimensions);
+    // Can also use to decrement, with negative values
+    void incrementMemorySizeByDimensions(List<CacheStatsDimension> dimensions, long amountBytes);
+    void incrementEntriesByDimensions(List<CacheStatsDimension> dimensions);
+    void decrementEntriesByDimensions(List<CacheStatsDimension> dimensions);
+
 }

server/src/main/java/org/opensearch/common/cache/stats/CacheStatsDimension.java

@@ -0,0 +1,63 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.common.cache.stats;
+
+import org.opensearch.core.common.io.stream.StreamInput;
+import org.opensearch.core.common.io.stream.StreamOutput;
+import org.opensearch.core.common.io.stream.Writeable;
+
+import java.io.IOException;
+import java.util.Objects;
+
+public class CacheStatsDimension implements Writeable {
+    // Values for tier dimensions, that are reused across CacheStats implementations
+    public static final String TIER_DIMENSION_NAME = "tier";
+    public static final String TIER_DIMENSION_VALUE_ON_HEAP = "on_heap";
+    public static final String TIER_DIMENSION_VALUE_DISK = "disk";
+    public final String dimensionName;
+    public final String dimensionValue;
+    public CacheStatsDimension(String dimensionName, String dimensionValue) {
+        this.dimensionName = dimensionName;
+        this.dimensionValue = dimensionValue;
+    }
+
+    public CacheStatsDimension(StreamInput in) throws IOException {
+        this.dimensionName = in.readString();
+        this.dimensionValue = in.readString();
+    }
+
+    @Override
+    public void writeTo(StreamOutput out) throws IOException {
+        out.writeString(dimensionName);
+        out.writeString(dimensionValue);
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (o == this) {
+            return true;
+        }
+        if (o == null) {
+            return false;
+        }
+        if (o.getClass() != CacheStatsDimension.class) {
+            return false;
+        }
+        CacheStatsDimension other = (CacheStatsDimension) o;
+        if (other.dimensionName == null || other.dimensionValue == null) {
+            return false;
+        }
+        return other.dimensionName.equals(dimensionName) && other.dimensionValue.equals(dimensionValue);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(dimensionName, dimensionValue);
+    }
+}

server/src/main/java/org/opensearch/common/cache/stats/CacheStatsResponse.java

@@ -0,0 +1,28 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.common.cache.stats;
+
+/**
+ * A class containing the 5 metrics tracked by a CacheStats object.
+ */
+public class CacheStatsResponse { // TODO: Make this extend ToXContent.
+    public final long hits;
+    public final long misses;
+    public final long evictions;
+    public final long memorySize;
+    public final long entries;
+
+    public CacheStatsResponse(long hits, long misses, long evictions, long memorySize, long entries) {
+        this.hits = hits;
+        this.misses = misses;
+        this.evictions = evictions;
+        this.memorySize = memorySize;
+        this.entries = entries;
+    }
+}