Add Windows native method to retrieve the number of allocated bytes on disk for file (#79698)

In #79371 we fixed a bug where cache files were not created 
as sparse files on Windows platforms because the wrong 
options were used when creating the files for the first time. 
This bug got unnoticed as we were lacking a way to retrieve 
the exact number of bytes allocated for a given file on disk.

This commit adds a FileSystemNatives.allocatedSizeInBytes(Path) 
method for that exact purpose (only implemented for Windows 
for now) and a test in CacheFileTests that would fail on 
Windows if the cache file is not sparse.

Relates #79371

Author: tlrx

server/src/main/java/org/elasticsearch/bootstrap/Bootstrap.java

@@ -20,6 +20,7 @@
 import org.elasticsearch.Version;
 import org.elasticsearch.cli.UserException;
 import org.elasticsearch.common.PidFile;
+import org.elasticsearch.common.filesystem.FileSystemNatives;
 import org.elasticsearch.common.inject.CreationException;
 import org.elasticsearch.common.logging.LogConfigurator;
 import org.elasticsearch.common.logging.Loggers;
@@ -150,6 +151,9 @@ public boolean handle(int code) {
 
         // init lucene random seed. it will use /dev/urandom where available:
         StringHelper.randomId();
+
+        // init filesystem natives
+        FileSystemNatives.init();
     }
 
     static void initializeProbes() {

server/src/main/java/org/elasticsearch/common/filesystem/FileSystemNatives.java

@@ -0,0 +1,66 @@
+/*
+ * 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.common.filesystem;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.apache.lucene.util.Constants;
+
+import java.nio.file.Path;
+import java.util.OptionalLong;
+
+/**
+ * This class provides utility methods for calling some native methods related to filesystems.
+ */
+public final class FileSystemNatives {
+
+    private static final Logger logger = LogManager.getLogger(FileSystemNatives.class);
+
+    @FunctionalInterface
+    interface Provider {
+        OptionalLong allocatedSizeInBytes(Path path);
+    }
+
+    private static final Provider NOOP_FILE_SYSTEM_NATIVES_PROVIDER = path -> OptionalLong.empty();
+    private static final Provider JNA_PROVIDER = loadJnaProvider();
+
+    private static Provider loadJnaProvider() {
+        try {
+            // load one of the main JNA classes to see if the classes are available. this does not ensure that all native
+            // libraries are available, only the ones necessary by JNA to function
+            Class.forName("com.sun.jna.Native");
+            if (Constants.WINDOWS) {
+                return WindowsFileSystemNatives.getInstance();
+            }
+        } catch (ClassNotFoundException e) {
+            logger.warn("JNA not found. FileSystemNatives methods will be disabled.", e);
+        } catch (LinkageError e) {
+            logger.warn("unable to load JNA native support library, FileSystemNatives methods will be disabled.", e);
+        }
+        return NOOP_FILE_SYSTEM_NATIVES_PROVIDER;
+    }
+
+    private FileSystemNatives() {}
+
+    public static void init() {
+        assert JNA_PROVIDER != null;
+    }
+
+    /**
+     * Returns the number of allocated bytes on disk for a given file.
+     *
+     * @param path the path to the file
+     * @return an {@link OptionalLong} that contains the number of allocated bytes on disk for the file. The optional is empty is the
+     * allocated size of the file failed be retrieved using native methods
+     */
+    public static OptionalLong allocatedSizeInBytes(Path path) {
+        return JNA_PROVIDER.allocatedSizeInBytes(path);
+    }
+
+}

server/src/main/java/org/elasticsearch/common/filesystem/WindowsFileSystemNatives.java

@@ -0,0 +1,98 @@
+/*
+ * 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.common.filesystem;
+
+import com.sun.jna.Native;
+import com.sun.jna.WString;
+import com.sun.jna.ptr.IntByReference;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.apache.lucene.util.Constants;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.OptionalLong;
+
+/**
+ * {@link FileSystemNatives.Provider} implementation for Windows/Kernel32
+ */
+final class WindowsFileSystemNatives implements FileSystemNatives.Provider {
+
+    private static final Logger logger = LogManager.getLogger(WindowsFileSystemNatives.class);
+
+    private static final WindowsFileSystemNatives INSTANCE = new WindowsFileSystemNatives();
+
+    private static final int INVALID_FILE_SIZE = -1;
+    private static final int NO_ERROR = 0;
+
+    private WindowsFileSystemNatives() {
+        assert Constants.WINDOWS : Constants.OS_NAME;
+        try {
+            Native.register("kernel32");
+            logger.debug("windows/Kernel32 library loaded");
+        } catch (LinkageError e) {
+            logger.warn("unable to link Windows/Kernel32 library. native methods and handlers will be disabled.", e);
+            throw e;
+        }
+    }
+
+    static WindowsFileSystemNatives getInstance() {
+        return INSTANCE;
+    }
+
+    /**
+     * Retrieves the actual number of bytes of disk storage used to store a specified file.
+     *
+     * https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-getcompressedfilesizew
+     *
+     * @param lpFileName the path string
+     * @param lpFileSizeHigh pointer to high-order DWORD for compressed file size (or null if not needed)
+     * @return the low-order DWORD for compressed file siz
+     */
+    private native int GetCompressedFileSizeW(WString lpFileName, IntByReference lpFileSizeHigh);
+
+    /**
+     * Retrieves the actual number of bytes of disk storage used to store a specified file. If the file is located on a volume that supports
+     * compression and the file is compressed, the value obtained is the compressed size of the specified file. If the file is located on a
+     * volume that supports sparse files and the file is a sparse file, the value obtained is the sparse size of the specified file.
+     *
+     * This method uses Win32 DLL native method {@link #GetCompressedFileSizeW(WString, IntByReference)}.
+     *
+     * @param path the path to the file
+     * @return an {@link OptionalLong} that contains the number of allocated bytes on disk for the file, or empty if the size is invalid
+     */
+    public OptionalLong allocatedSizeInBytes(Path path) {
+        assert Files.isRegularFile(path) : path;
+        final WString fileName = new WString("\\\\?\\" + path);
+        final IntByReference lpFileSizeHigh = new IntByReference();
+
+        final int lpFileSizeLow = GetCompressedFileSizeW(fileName, lpFileSizeHigh);
+        if (lpFileSizeLow == INVALID_FILE_SIZE) {
+            final int err = Native.getLastError();
+            if (err != NO_ERROR) {
+                logger.warn("error [{}] when executing native method GetCompressedFileSizeW for file [{}]", err, path);
+                return OptionalLong.empty();
+            }
+        }
+
+        // convert lpFileSizeLow to unsigned long and combine with signed/shifted lpFileSizeHigh
+        final long allocatedSize = (((long) lpFileSizeHigh.getValue()) << Integer.SIZE) | Integer.toUnsignedLong(lpFileSizeLow);
+        if (logger.isTraceEnabled()) {
+            logger.trace(
+                "executing native method GetCompressedFileSizeW returned [high={}, low={}, allocated={}] for file [{}]",
+                lpFileSizeHigh,
+                lpFileSizeLow,
+                allocatedSize,
+                path
+            );
+        }
+        return OptionalLong.of(allocatedSize);
+    }
+}

x-pack/plugin/searchable-snapshots/src/test/java/org/elasticsearch/xpack/searchablesnapshots/cache/common/CacheFileTests.java

@@ -7,8 +7,11 @@
 package org.elasticsearch.xpack.searchablesnapshots.cache.common;
 
 import org.apache.lucene.store.AlreadyClosedException;
+import org.apache.lucene.util.Constants;
+import org.apache.lucene.util.LuceneTestCase;
 import org.apache.lucene.util.SetOnce;
 import org.elasticsearch.common.UUIDs;
+import org.elasticsearch.common.filesystem.FileSystemNatives;
 import org.elasticsearch.common.util.concurrent.DeterministicTaskQueue;
 import org.elasticsearch.core.PathUtils;
 import org.elasticsearch.core.PathUtilsForTesting;
@@ -20,16 +23,19 @@
 import org.hamcrest.Matcher;
 
 import java.io.IOException;
+import java.nio.ByteBuffer;
 import java.nio.channels.FileChannel;
 import java.nio.file.FileSystem;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Locale;
 import java.util.Objects;
+import java.util.OptionalLong;
 import java.util.Set;
 import java.util.SortedSet;
 import java.util.concurrent.ExecutionException;
@@ -38,13 +44,16 @@
 import static org.elasticsearch.xpack.searchablesnapshots.cache.common.TestUtils.randomPopulateAndReads;
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.greaterThanOrEqualTo;
 import static org.hamcrest.Matchers.hasSize;
 import static org.hamcrest.Matchers.instanceOf;
 import static org.hamcrest.Matchers.is;
+import static org.hamcrest.Matchers.lessThan;
 import static org.hamcrest.Matchers.notNullValue;
 import static org.hamcrest.Matchers.nullValue;
 import static org.hamcrest.Matchers.sameInstance;
 
+@LuceneTestCase.SuppressFileSystems("DisableFsyncFS") // required by {@link testCacheFileCreatedAsSparseFile()}
 public class CacheFileTests extends ESTestCase {
 
     private static final CacheFile.ModificationListener NOOP = new CacheFile.ModificationListener() {
@@ -57,7 +66,7 @@ public void onCacheFileDelete(CacheFile cacheFile) {}
 
     private static final CacheKey CACHE_KEY = new CacheKey("_snap_uuid", "_snap_index", new ShardId("_name", "_uuid", 0), "_filename");
 
-    public void testGetCacheKey() throws Exception {
+    public void testGetCacheKey() {
         final Path file = createTempDir().resolve("file.new");
         final CacheKey cacheKey = new CacheKey(
             UUIDs.randomBase64UUID(random()),
@@ -380,6 +389,54 @@ public void testFSyncFailure() throws Exception {
         }
     }
 
+    public void testCacheFileCreatedAsSparseFile() throws Exception {
+        assumeTrue("This test uses a native method implemented only for Windows", Constants.WINDOWS);
+        final long oneMb = 1 << 20;
+
+        final Path file = createTempDir().resolve(UUIDs.randomBase64UUID(random()));
+        final CacheFile cacheFile = new CacheFile(
+            new CacheKey("_snap_uuid", "_snap_name", new ShardId("_name", "_uid", 0), "_filename"),
+            oneMb,
+            file,
+            NOOP
+        );
+        assertFalse(Files.exists(file));
+
+        final TestEvictionListener listener = new TestEvictionListener();
+        cacheFile.acquire(listener);
+        try {
+            final FileChannel fileChannel = cacheFile.getChannel();
+            assertTrue(Files.exists(file));
+
+            OptionalLong sizeOnDisk = FileSystemNatives.allocatedSizeInBytes(file);
+            assertTrue(sizeOnDisk.isPresent());
+            assertThat(sizeOnDisk.getAsLong(), equalTo(0L));
+
+            // write 1 byte at the last position in the cache file.
+            // For non sparse files, Windows would allocate the full file on disk in order to write a single byte at the end,
+            // making the next assertion fails.
+            fill(fileChannel, Math.toIntExact(cacheFile.getLength() - 1L), Math.toIntExact(cacheFile.getLength()));
+            fileChannel.force(false);
+
+            sizeOnDisk = FileSystemNatives.allocatedSizeInBytes(file);
+            assertTrue(sizeOnDisk.isPresent());
+            assertThat("Cache file should be sparse and not fully allocated on disk", sizeOnDisk.getAsLong(), lessThan(oneMb));
+
+            fill(fileChannel, 0, Math.toIntExact(cacheFile.getLength()));
+            fileChannel.force(false);
+
+            sizeOnDisk = FileSystemNatives.allocatedSizeInBytes(file);
+            assertTrue(sizeOnDisk.isPresent());
+            assertThat(
+                "Cache file should be fully allocated on disk (maybe more given cluster/block size)",
+                sizeOnDisk.getAsLong(),
+                greaterThanOrEqualTo(oneMb)
+            );
+        } finally {
+            cacheFile.release(listener);
+        }
+    }
+
     static class TestEvictionListener implements EvictionListener {
 
         private final SetOnce<CacheFile> evicted = new SetOnce<>();
@@ -440,4 +497,24 @@ private static FSyncTrackingFileSystemProvider setupFSyncCountingFileSystem() {
         PathUtilsForTesting.installMock(provider.getFileSystem(null));
         return provider;
     }
+
+    private static void fill(FileChannel fileChannel, int from, int to) {
+        final byte[] buffer = new byte[Math.min(Math.max(0, to - from), 1024)];
+        Arrays.fill(buffer, (byte) 0xff);
+        assert fileChannel.isOpen();
+
+        try {
+            int written = 0;
+            int remaining = to - from;
+            while (remaining > 0) {
+                final int len = Math.min(remaining, buffer.length);
+                fileChannel.write(ByteBuffer.wrap(buffer, 0, len), from + written);
+                remaining -= len;
+                written += len;
+            }
+            assert written == to - from;
+        } catch (IOException e) {
+            throw new AssertionError(e);
+        }
+    }
 }