Support core.fsyncObjectFiles option

Some repositories may be on really unstable filesystems, but still
want to have good reliability when objects are written to disk.  If
core.fsyncObjectFiles is set to true, request the JVM to ensure the
data is written before returning success to the caller of insert.

The option defaults to false because it should be useless on any
filesystem that orders writes and metadata, such as ext3 mounted with
data=ordered (or data=journal).  But it may be useful on some systems
(especially HFS+) where file content may flush to the disk
independently of filesystem structure changes.

Because FileChannel.force(boolean) only claims to ensure data is
written if it was written using the write(ByteBuffer) method of
FileChannel, redirect all writes when using fsyncObjectFiles to go
through the FileChannel interface instead of through the older style
OutputStream interface.  This may not be necessary on all JVMs, but
its more portable to follow the definition than the common behavior.

Change-Id: I57f6b6bb7e403c07fbae989dbf3758eaf5edbc78
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

org.eclipse.jgit/src/org/eclipse/jgit/storage/file/ObjectDirectoryInserter.java

@@ -52,6 +52,7 @@ import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.nio.channels.Channels;
 import java.security.DigestOutputStream;
 import java.security.MessageDigest;
 import java.util.zip.Deflater;
@@ -60,7 +61,6 @@ import java.util.zip.DeflaterOutputStream;
 import org.eclipse.jgit.errors.ObjectWritingException;
 import org.eclipse.jgit.lib.Config;
 import org.eclipse.jgit.lib.Constants;
-import org.eclipse.jgit.lib.CoreConfig;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectInserter;
 
@@ -68,13 +68,13 @@ import org.eclipse.jgit.lib.ObjectInserter;
 class ObjectDirectoryInserter extends ObjectInserter {
 	private final FileObjectDatabase db;
 
-	private final Config config;
+	private final WriteConfig config;
 
 	private Deflater deflate;
 
 	ObjectDirectoryInserter(final FileObjectDatabase dest, final Config cfg) {
 		db = dest;
-		config = cfg;
+		config = cfg.get(WriteConfig.KEY);
 	}
 
 	@Override
@@ -121,9 +121,13 @@ class ObjectDirectoryInserter extends ObjectInserter {
 		boolean delete = true;
 		File tmp = newTempFile();
 		try {
-			DigestOutputStream dOut = new DigestOutputStream(
-					compress(new FileOutputStream(tmp)), md);
+			FileOutputStream fOut = new FileOutputStream(tmp);
 			try {
+				OutputStream out = fOut;
+				if (config.getFSyncObjectFiles())
+					out = Channels.newOutputStream(fOut.getChannel());
+				DeflaterOutputStream cOut = compress(out);
+				DigestOutputStream dOut = new DigestOutputStream(cOut, md);
 				writeHeader(dOut, type, len);
 
 				final byte[] buf = buffer();
@@ -134,8 +138,12 @@ class ObjectDirectoryInserter extends ObjectInserter {
 					dOut.write(buf, 0, n);
 					len -= n;
 				}
+				dOut.flush();
+				cOut.finish();
 			} finally {
-				dOut.close();
+				if (config.getFSyncObjectFiles())
+					fOut.getChannel().force(true);
+				fOut.close();
 			}
 
 			delete = false;
@@ -160,7 +168,7 @@ class ObjectDirectoryInserter extends ObjectInserter {
 
 	DeflaterOutputStream compress(final OutputStream out) {
 		if (deflate == null)
-			deflate = new Deflater(config.get(CoreConfig.KEY).getCompression());
+			deflate = new Deflater(config.getCompression());
 		else
 			deflate.reset();
 		return new DeflaterOutputStream(out, deflate);

org.eclipse.jgit/src/org/eclipse/jgit/storage/file/WriteConfig.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright (C) 2010, Google Inc.
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.eclipse.jgit.storage.file;
+
+import org.eclipse.jgit.lib.Config;
+import org.eclipse.jgit.lib.Config.SectionParser;
+import org.eclipse.jgit.lib.CoreConfig;
+
+class WriteConfig {
+	/** Key for {@link Config#get(SectionParser)}. */
+	static final Config.SectionParser<WriteConfig> KEY = new SectionParser<WriteConfig>() {
+		public WriteConfig parse(final Config cfg) {
+			return new WriteConfig(cfg);
+		}
+	};
+
+	private final int compression;
+
+	private final boolean fsyncObjectFiles;
+
+	private WriteConfig(final Config rc) {
+		compression = rc.get(CoreConfig.KEY).getCompression();
+		fsyncObjectFiles = rc.getBoolean("core", "fsyncobjectfiles", false);
+	}
+
+	int getCompression() {
+		return compression;
+	}
+
+	boolean getFSyncObjectFiles() {
+		return fsyncObjectFiles;
+	}
+}