OAK-12162 : removed guava's cachestats and did the final cleanup

oak-blob-plugins/src/main/java/org/apache/jackrabbit/oak/plugins/blob/CachingBlobStore.java

@@ -16,9 +16,8 @@
  */
 package org.apache.jackrabbit.oak.plugins.blob;
 
-import org.apache.jackrabbit.oak.cache.AbstractCacheStats;
 import org.apache.jackrabbit.oak.cache.CacheLIRS;
-import org.apache.jackrabbit.oak.cache.api.CacheStatsAdapter;
+import org.apache.jackrabbit.oak.cache.CacheStats;
 import org.apache.jackrabbit.oak.cache.api.LoadingCache;
 import org.apache.jackrabbit.oak.cache.api.Weigher;
 import org.apache.jackrabbit.oak.commons.StringUtils;
@@ -48,7 +47,7 @@ public abstract class CachingBlobStore extends AbstractBlobStore {
         return (int) weight;
     };
 
-    private final AbstractCacheStats cacheStats;
+    private final CacheStats cacheStats;
 
     public static final String MEM_CACHE_NAME = "BlobStore-MemCache";
 
@@ -62,7 +61,7 @@ public CachingBlobStore(long cacheSize) {
                 weigher(weigher::weigh).
                 build().asOakCache();
 
-        cacheStats = new CacheStatsAdapter(cache, MEM_CACHE_NAME, weigher, cacheSize);
+        cacheStats = new CacheStats(cache, MEM_CACHE_NAME, weigher, cacheSize);
     }
 
     public CachingBlobStore() {
@@ -79,7 +78,7 @@ public long getBlobCacheSize() {
         return blobCacheSize;
     }
 
-    public AbstractCacheStats getCacheStats() {
+    public CacheStats getCacheStats() {
         return cacheStats;
     }
 }

oak-blob-plugins/src/main/java/org/apache/jackrabbit/oak/plugins/blob/FileCache.java

@@ -39,7 +39,7 @@
 import org.apache.jackrabbit.oak.cache.CacheLIRS;
 import org.apache.jackrabbit.oak.cache.api.Cache;
 import org.apache.jackrabbit.oak.cache.api.CacheLoader;
-import org.apache.jackrabbit.oak.cache.api.CacheStatsAdapter;
+import org.apache.jackrabbit.oak.cache.CacheStats;
 import org.apache.jackrabbit.oak.cache.api.Weigher;
 import org.apache.jackrabbit.oak.commons.StringUtils;
 import org.apache.jackrabbit.oak.commons.concurrent.ExecutorCloser;
@@ -423,7 +423,7 @@ private int build() {
     }
 }
 
-class FileCacheStats extends CacheStatsAdapter implements DataStoreCacheStatsMBean {
+class FileCacheStats extends CacheStats implements DataStoreCacheStatsMBean {
     private static final long BLOCK_SIZE = 4 * 1024;
     private final Weigher<Object, Object> weigher;
     private final Cache<Object, Object> cache;

oak-blob-plugins/src/main/java/org/apache/jackrabbit/oak/plugins/blob/datastore/DataStoreBlobStore.java

@@ -52,10 +52,8 @@
 import org.apache.jackrabbit.oak.api.blob.BlobDownloadOptions;
 import org.apache.jackrabbit.oak.api.blob.BlobUpload;
 import org.apache.jackrabbit.oak.api.blob.BlobUploadOptions;
-import org.apache.jackrabbit.oak.cache.AbstractCacheStats;
 import org.apache.jackrabbit.oak.cache.api.Cache;
-import org.apache.jackrabbit.oak.cache.api.CacheBuilder;
-import org.apache.jackrabbit.oak.cache.api.CacheStatsAdapter;
+import org.apache.jackrabbit.oak.cache.CacheStats;
 import org.apache.jackrabbit.oak.cache.api.Weigher;
 import org.apache.jackrabbit.oak.commons.StringUtils;
 import org.apache.jackrabbit.oak.commons.collections.IteratorUtils;
@@ -134,7 +132,7 @@ public int weigh(@NotNull String key, @NotNull byte[] value) {
         }
     };
 
-    private final AbstractCacheStats cacheStats;
+    private final CacheStats cacheStats;
 
     public static final String MEM_CACHE_NAME = "BlobStore-MemCache";
 
@@ -159,7 +157,7 @@ public DataStoreBlobStore(DataStore delegate, boolean encodeLengthInId, int cach
                 .maximumWeight(cacheSize)
                 .weigher(weigher::weigh)
                 .build().asOakCache();
-        this.cacheStats = new CacheStatsAdapter(cache, MEM_CACHE_NAME, weigher, cacheSize);
+        this.cacheStats = new CacheStats(cache, MEM_CACHE_NAME, weigher, cacheSize);
     }
 
     //~----------------------------------< DataStore >
@@ -828,7 +826,7 @@ public DataStore getDataStore() {
         return delegate;
     }
 
-    public AbstractCacheStats getCacheStats() {
+    public CacheStats getCacheStats() {
         return cacheStats;
     }
 

oak-core-spi/src/main/java/org/apache/jackrabbit/oak/cache/AbstractCacheStats.java

@@ -25,8 +25,8 @@
 import java.util.StringJoiner;
 import java.util.concurrent.TimeUnit;
 
-import org.apache.jackrabbit.guava.common.cache.CacheStats;
 import org.apache.jackrabbit.oak.api.jmx.CacheStatsMBean;
+import org.apache.jackrabbit.oak.cache.api.CacheStatsSnapshot;
 import org.apache.jackrabbit.oak.commons.jmx.AnnotatedStandardMBean;
 import org.jetbrains.annotations.NotNull;
 
@@ -38,8 +38,8 @@ public abstract class AbstractCacheStats extends AnnotatedStandardMBean implemen
     @NotNull
     private final String name;
 
-    private CacheStats lastSnapshot =
-            new CacheStats(0, 0, 0, 0, 0, 0);
+    private CacheStatsSnapshot lastSnapshot =
+            new CacheStatsSnapshot(0, 0, 0, 0, 0, 0);
 
     /**
      * Create a new {@code CacheStatsMBean} for a cache with the given {@code name}.
@@ -51,19 +51,21 @@ protected AbstractCacheStats(@NotNull String name) {
     }
 
     /**
-     * Call back invoked to retrieve the most recent {@code CacheStats} instance of the
+     * Call back invoked to retrieve the most recent {@link CacheStatsSnapshot} of the
      * underlying cache.
      */
-    protected abstract CacheStats getCurrentStats();
+    protected abstract CacheStatsSnapshot getCurrentStats();
 
-    private CacheStats stats() {
-        return getCurrentStats().minus(lastSnapshot);
+    private CacheStatsSnapshot stats() {
+        CacheStatsSnapshot baseline;
+        synchronized (this) {
+            baseline = lastSnapshot;
+        }
+        return getCurrentStats().minus(baseline);
     }
 
     @Override
     public synchronized void resetStats() {
-        // Cache stats cannot be rest at Guava level. Instead we
-        // take a snapshot and then subtract it from future stats calls
         lastSnapshot = getCurrentStats();
     }
 

oak-core-spi/src/main/java/org/apache/jackrabbit/oak/cache/CacheStats.java

@@ -1,82 +1,79 @@
 /*
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements.  See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership.  The ASF licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License.  You may obtain a copy of the License at
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
  *
- *   http://www.apache.org/licenses/LICENSE-2.0
+ *      http://www.apache.org/licenses/LICENSE-2.0
  *
- * Unless required by applicable law or agreed to in writing,
- * software distributed under the License is distributed on an
- * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
- * KIND, either express or implied.  See the License for the
- * specific language governing permissions and limitations
- * under the License.
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
  */
 package org.apache.jackrabbit.oak.cache;
 
 import java.util.Map;
-import java.util.Objects;
-
-import org.apache.jackrabbit.guava.common.cache.Cache;
-import org.apache.jackrabbit.guava.common.cache.Weigher;
 
+import org.apache.jackrabbit.oak.cache.api.Cache;
+import org.apache.jackrabbit.oak.cache.api.CacheStatsSnapshot;
+import org.apache.jackrabbit.oak.cache.api.Weigher;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 /**
- * Cache statistics.
+ * Exposes a {@link Cache}'s statistics via the {@link org.apache.jackrabbit.oak.api.jmx.CacheStatsMBean}
+ * interface.
  */
 public class CacheStats extends AbstractCacheStats {
+
     private final Cache<Object, Object> cache;
     private final Weigher<Object, Object> weigher;
     private final long maxWeight;
 
     /**
-     * Construct the cache stats object.
-     * 
-     * @param cache the cache
-     * @param name the name of the cache
-     * @param weigher the weigher used to estimate the current weight
-     * @param maxWeight the maximum weight
+     * Creates an adapter for the given cache.
+     *
+     * @param cache     the cache whose statistics to expose (must not be null)
+     * @param name      the JMX bean name (must not be null)
+     * @param weigher   optional weigher used to estimate current cache weight; {@code null} if unknown
+     * @param maxWeight configured maximum weight for the cache; {@code -1} if unbounded
      */
     @SuppressWarnings("unchecked")
-    public CacheStats(
-            @NotNull Cache<?, ?> cache,
+    public <K, V> CacheStats(
+            @NotNull Cache<K, V> cache,
             @NotNull String name,
-            @Nullable Weigher<?, ?> weigher,
+            @Nullable Weigher<K, V> weigher,
             long maxWeight) {
         super(name);
-        this.cache = (Cache<Object, Object>) Objects.requireNonNull(cache);
+        this.cache = (Cache<Object, Object>) cache;
         this.weigher = (Weigher<Object, Object>) weigher;
         this.maxWeight = maxWeight;
     }
 
     @Override
-    protected org.apache.jackrabbit.guava.common.cache.CacheStats getCurrentStats() {
+    protected CacheStatsSnapshot getCurrentStats() {
         return cache.stats();
     }
 
     @Override
     public long getElementCount() {
-        return cache.size();
+        return cache.asMap().size();
     }
 
     @Override
     public long estimateCurrentWeight() {
         if (weigher == null) {
             return -1;
         }
-        long size = 0;
-        for (Map.Entry<?, ?> e : cache.asMap().entrySet()) {
-            Object k = e.getKey();
-            Object v = e.getValue();
-            size += weigher.weigh(k, v);
+        long total = 0;
+        for (Map.Entry<Object, Object> e : cache.asMap().entrySet()) {
+            total += weigher.weigh(e.getKey(), e.getValue());
         }
-        return size;
+        return total;
     }
 
     @Override

oak-core-spi/src/main/java/org/apache/jackrabbit/oak/cache/EmpiricalWeigher.java

@@ -27,8 +27,7 @@
  * Determines the weight of object based on the memory taken by them. The memory estimates
  * are based on empirical data and not exact
  */
-public class EmpiricalWeigher extends GuavaCompatibleEmpiricalWeigher
-        implements Weigher<CacheValue, CacheValue> {
+public class EmpiricalWeigher implements Weigher<CacheValue, CacheValue> {
 
     static final Logger LOG = LoggerFactory.getLogger(EmpiricalWeigher.class);
 
@@ -45,15 +44,3 @@ public int weigh(@NotNull CacheValue key, @NotNull CacheValue value) {
     }
 
 }
-
-/**
- * Compatibility base class that keeps {@link EmpiricalWeigher} assignable to the
- * legacy Guava-shim {@link org.apache.jackrabbit.guava.common.cache.Weigher} type while the public API migrates to
- * {@link Weigher}.
- *
- * <p>TODO OAK-12162: remove this compatibility base in
- * OAK-12162 once downstream callers no longer require {@link org.apache.jackrabbit.guava.common.cache.Weigher}
- * assignability.</p>
- */
-abstract class GuavaCompatibleEmpiricalWeigher implements org.apache.jackrabbit.guava.common.cache.Weigher<CacheValue, CacheValue> {
-}