File System Caching for remote store

Signed-off-by: Ahmad AbuKhalil <abukhali@amazon.com>

server/src/internalClusterTest/java/org/opensearch/search/SearchWeightedRoutingIT.java

@@ -837,9 +837,8 @@ public void testStrictWeightedRouting() throws Exception {
 
     /**
      *  Assert that preference based search works with non-strict weighted shard routing
-     * @throws Exception
      */
-    public void testPreferenceSearchWithWeightedRouting() throws Exception {
+    public void testPreferenceSearchWithWeightedRouting() {
         Settings commonSettings = Settings.builder()
             .put("cluster.routing.allocation.awareness.attributes", "zone")
             .put("cluster.routing.allocation.awareness.force.zone.values", "a,b,c")

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

@@ -513,17 +513,15 @@ private void put(K key, V value, long now) {
             promote(tuple.v1(), now);
         }
         if (replaced) {
-            removalListener.onRemoval(
-                new RemovalNotification<>(tuple.v2().key, tuple.v2().value, RemovalNotification.RemovalReason.REPLACED)
-            );
+            removalListener.onRemoval(new RemovalNotification<>(tuple.v2().key, tuple.v2().value, RemovalReason.REPLACED));
         }
     }
 
     private final Consumer<CompletableFuture<Entry<K, V>>> invalidationConsumer = f -> {
         try {
             Entry<K, V> entry = f.get();
             try (ReleasableLock ignored = lruLock.acquire()) {
-                delete(entry, RemovalNotification.RemovalReason.INVALIDATED);
+                delete(entry, RemovalReason.INVALIDATED);
             }
         } catch (ExecutionException e) {
             // ok
@@ -534,7 +532,7 @@ private void put(K key, V value, long now) {
 
     /**
      * Invalidate the association for the specified key. A removal notification will be issued for invalidated
-     * entries with {@link org.opensearch.common.cache.RemovalNotification.RemovalReason} INVALIDATED.
+     * entries with {@link RemovalReason} INVALIDATED.
      *
      * @param key the key whose mapping is to be invalidated from the cache
      */
@@ -546,7 +544,7 @@ public void invalidate(K key) {
     /**
      * Invalidate the entry for the specified key and value. If the value provided is not equal to the value in
      * the cache, no removal will occur. A removal notification will be issued for invalidated
-     * entries with {@link org.opensearch.common.cache.RemovalNotification.RemovalReason} INVALIDATED.
+     * entries with {@link RemovalReason} INVALIDATED.
      *
      * @param key the key whose mapping is to be invalidated from the cache
      * @param value the expected value that should be associated with the key
@@ -558,7 +556,7 @@ public void invalidate(K key, V value) {
 
     /**
      * Invalidate all cache entries. A removal notification will be issued for invalidated entries with
-     * {@link org.opensearch.common.cache.RemovalNotification.RemovalReason} INVALIDATED.
+     * {@link RemovalReason} INVALIDATED.
      */
     public void invalidateAll() {
         Entry<K, V> h;
@@ -589,7 +587,7 @@ public void invalidateAll() {
             }
         }
         while (h != null) {
-            removalListener.onRemoval(new RemovalNotification<>(h.key, h.value, RemovalNotification.RemovalReason.INVALIDATED));
+            removalListener.onRemoval(new RemovalNotification<>(h.key, h.value, RemovalReason.INVALIDATED));
             h = h.after;
         }
     }
@@ -707,7 +705,7 @@ public void remove() {
                 segment.remove(entry.key, entry.value, f -> {});
                 try (ReleasableLock ignored = lruLock.acquire()) {
                     current = null;
-                    delete(entry, RemovalNotification.RemovalReason.INVALIDATED);
+                    delete(entry, RemovalReason.INVALIDATED);
                 }
             }
         }
@@ -796,10 +794,10 @@ private void evictEntry(Entry<K, V> entry) {
         if (segment != null) {
             segment.remove(entry.key, entry.value, f -> {});
         }
-        delete(entry, RemovalNotification.RemovalReason.EVICTED);
+        delete(entry, RemovalReason.EVICTED);
     }
 
-    private void delete(Entry<K, V> entry, RemovalNotification.RemovalReason removalReason) {
+    private void delete(Entry<K, V> entry, RemovalReason removalReason) {
         assert lruLock.isHeldByCurrentThread();
 
         if (unlink(entry)) {

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

@@ -0,0 +1,41 @@
+/*
+ * 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.refcounted.RefCountedCache;
+
+/**
+ * Usage metrics for {@link RefCountedCache}
+ *
+ * @opensearch.internal
+ */
+public class CacheUsage {
+    /**
+     * Cache usage of the system
+     */
+    private final long usage;
+
+    /**
+     * Cache usage by entries which are referenced
+     */
+    private final long activeUsage;
+
+    public CacheUsage(long usage, long activeUsage) {
+        this.usage = usage;
+        this.activeUsage = activeUsage;
+    }
+
+    public long usage() {
+        return usage;
+    }
+
+    public long activeUsage() {
+        return activeUsage;
+    }
+}

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

@@ -38,16 +38,6 @@
  * @opensearch.internal
  */
 public class RemovalNotification<K, V> {
-    /**
-     * Reason for notification removal
-     *
-     * @opensearch.internal
-     */
-    public enum RemovalReason {
-        REPLACED,
-        INVALIDATED,
-        EVICTED
-    }
 
     private final K key;
     private final V value;

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

@@ -0,0 +1,22 @@
+/*
+ * 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;
+
+/**
+ * Reason for notification removal
+ *
+ * @opensearch.internal
+ */
+public enum RemovalReason {
+    REPLACED,
+    INVALIDATED,
+    EVICTED,
+    EXPLICIT,
+    CAPACITY
+}

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

@@ -0,0 +1,27 @@
+/*
+ * 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;
+
+/**
+ * A class that can determine the weight of a value. The total weight threshold
+ * is used to determine when an eviction is required.
+ *
+ * @opensearch.internal
+ */
+public interface Weigher<V> {
+
+    /**
+     * Measures an object's weight to determine how many units of capacity that
+     * the value consumes. A value must consume a minimum of one unit.
+     *
+     * @param value the object to weigh
+     * @return the object's weight
+     */
+    long weightOf(V value);
+}