Allow Lucene directory implementations to estimate their size

Relates ES-5995

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

@@ -9,7 +9,6 @@
 package org.elasticsearch.index.store;
 
 import org.apache.lucene.store.Directory;
-import org.apache.lucene.store.FilterDirectory;
 import org.apache.lucene.store.IOContext;
 import org.apache.lucene.store.IndexOutput;
 import org.elasticsearch.common.lucene.store.FilterIndexOutput;
@@ -22,7 +21,7 @@
 import java.nio.file.AccessDeniedException;
 import java.nio.file.NoSuchFileException;
 
-final class ByteSizeCachingDirectory extends FilterDirectory {
+final class ByteSizeCachingDirectory extends ByteSizeDirectory {
 
     private static class SizeAndModCount {
         final long size;
@@ -57,7 +56,7 @@ private static long estimateSizeInBytes(Directory directory) throws IOException
 
     ByteSizeCachingDirectory(Directory in, TimeValue refreshInterval) {
         super(in);
-        size = new SingleObjectCache<SizeAndModCount>(refreshInterval, new SizeAndModCount(0L, -1L, true)) {
+        size = new SingleObjectCache<>(refreshInterval, new SizeAndModCount(0L, -1L, true)) {
             @Override
             protected SizeAndModCount refresh() {
                 // It is ok for the size of the directory to be more recent than
@@ -103,8 +102,8 @@ protected boolean needsRefresh() {
         };
     }
 
-    /** Return the cumulative size of all files in this directory. */
-    long estimateSizeInBytes() throws IOException {
+    @Override
+    public long estimateSizeInBytes() throws IOException {
         try {
             return size.getOrRefresh().size;
         } catch (UncheckedIOException e) {

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

@@ -0,0 +1,24 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+package org.elasticsearch.index.store;
+
+import org.apache.lucene.store.Directory;
+import org.apache.lucene.store.FilterDirectory;
+
+import java.io.IOException;
+
+public abstract class ByteSizeDirectory extends FilterDirectory {
+
+    protected ByteSizeDirectory(Directory in) {
+        super(in);
+    }
+
+    /** Return the cumulative size of all files in this directory. */
+    public abstract long estimateSizeInBytes() throws IOException;
+}

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

@@ -162,10 +162,10 @@ public Store(ShardId shardId, IndexSettings indexSettings, Directory directory,
 
     public Store(ShardId shardId, IndexSettings indexSettings, Directory directory, ShardLock shardLock, OnClose onClose) {
         super(shardId, indexSettings);
-        final TimeValue refreshInterval = indexSettings.getValue(INDEX_STORE_STATS_REFRESH_INTERVAL_SETTING);
-        logger.debug("store stats are refreshed with refresh_interval [{}]", refreshInterval);
-        ByteSizeCachingDirectory sizeCachingDir = new ByteSizeCachingDirectory(directory, refreshInterval);
-        this.directory = new StoreDirectory(sizeCachingDir, Loggers.getLogger("index.store.deletes", shardId));
+        this.directory = new StoreDirectory(
+            byteSizeDirectory(directory, indexSettings, logger),
+            Loggers.getLogger("index.store.deletes", shardId)
+        );
         this.shardLock = shardLock;
         this.onClose = onClose;
 
@@ -355,7 +355,7 @@ public CheckIndex.Status checkIndex(PrintStream out) throws IOException {
      */
     public StoreStats stats(long reservedBytes, LongUnaryOperator localSizeFunction) throws IOException {
         ensureOpen();
-        long sizeInBytes = directory.estimateSize();
+        long sizeInBytes = directory.estimateSizeInBytes();
         return new StoreStats(localSizeFunction.applyAsLong(sizeInBytes), sizeInBytes, reservedBytes);
     }
 
@@ -443,6 +443,16 @@ private void closeInternal() {
         }
     }
 
+    private static ByteSizeDirectory byteSizeDirectory(Directory directory, IndexSettings indexSettings, Logger logger) {
+        if (directory instanceof ByteSizeDirectory byteSizeDirectory) {
+            return byteSizeDirectory;
+        } else {
+            final TimeValue refreshInterval = indexSettings.getValue(INDEX_STORE_STATS_REFRESH_INTERVAL_SETTING);
+            logger.debug("store stats are refreshed with {} [{}]", INDEX_STORE_STATS_REFRESH_INTERVAL_SETTING.getKey(), refreshInterval);
+            return new ByteSizeCachingDirectory(directory, refreshInterval);
+        }
+    }
+
     /**
      * Reads a MetadataSnapshot from the given index locations or returns an empty snapshot if it can't be read.
      *
@@ -720,18 +730,18 @@ public void beforeClose() {
         shardLock.setDetails("closing shard");
     }
 
-    static final class StoreDirectory extends FilterDirectory {
+    static final class StoreDirectory extends ByteSizeDirectory {
 
         private final Logger deletesLogger;
 
-        StoreDirectory(ByteSizeCachingDirectory delegateDirectory, Logger deletesLogger) {
+        StoreDirectory(ByteSizeDirectory delegateDirectory, Logger deletesLogger) {
             super(delegateDirectory);
             this.deletesLogger = deletesLogger;
         }
 
-        /** Estimate the cumulative size of all files in this directory in bytes. */
-        long estimateSize() throws IOException {
-            return ((ByteSizeCachingDirectory) getDelegate()).estimateSizeInBytes();
+        @Override
+        public long estimateSizeInBytes() throws IOException {
+            return ((ByteSizeDirectory) getDelegate()).estimateSizeInBytes();
         }
 
         @Override