| /* |
| * Copyright (C) 2007, Robin Rosenberg <robin.rosenberg@dewire.com> |
| * Copyright (C) 2006-2008, Shawn O. Pearce <spearce@spearce.org> and others |
| * |
| * This program and the accompanying materials are made available under the |
| * terms of the Eclipse Distribution License v. 1.0 which is available at |
| * https://www.eclipse.org/org/documents/edl-v10.php. |
| * |
| * SPDX-License-Identifier: BSD-3-Clause |
| */ |
| |
| package org.eclipse.jgit.internal.storage.file; |
| |
| import static org.eclipse.jgit.lib.Constants.LOCK_SUFFIX; |
| |
| import java.io.File; |
| import java.io.FileInputStream; |
| import java.io.FileNotFoundException; |
| import java.io.FileOutputStream; |
| import java.io.FilenameFilter; |
| import java.io.IOException; |
| import java.io.OutputStream; |
| import java.nio.ByteBuffer; |
| import java.nio.channels.Channels; |
| import java.nio.channels.FileChannel; |
| import java.nio.file.Files; |
| import java.nio.file.StandardCopyOption; |
| import java.nio.file.attribute.FileTime; |
| import java.text.MessageFormat; |
| import java.time.Instant; |
| import java.util.concurrent.TimeUnit; |
| |
| import org.eclipse.jgit.internal.JGitText; |
| import org.eclipse.jgit.lib.Constants; |
| import org.eclipse.jgit.lib.ObjectId; |
| import org.eclipse.jgit.util.FS; |
| import org.eclipse.jgit.util.FS.LockToken; |
| import org.eclipse.jgit.util.FileUtils; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| /** |
| * Git style file locking and replacement. |
| * <p> |
| * To modify a ref file Git tries to use an atomic update approach: we write the |
| * new data into a brand new file, then rename it in place over the old name. |
| * This way we can just delete the temporary file if anything goes wrong, and |
| * nothing has been damaged. To coordinate access from multiple processes at |
| * once Git tries to atomically create the new temporary file under a well-known |
| * name. |
| */ |
| public class LockFile { |
| private static final Logger LOG = LoggerFactory.getLogger(LockFile.class); |
| |
| /** |
| * Unlock the given file. |
| * <p> |
| * This method can be used for recovering from a thrown |
| * {@link org.eclipse.jgit.errors.LockFailedException} . This method does |
| * not validate that the lock is or is not currently held before attempting |
| * to unlock it. |
| * |
| * @param file |
| * a {@link java.io.File} object. |
| * @return true if unlocked, false if unlocking failed |
| */ |
| public static boolean unlock(File file) { |
| final File lockFile = getLockFile(file); |
| final int flags = FileUtils.RETRY | FileUtils.SKIP_MISSING; |
| try { |
| FileUtils.delete(lockFile, flags); |
| } catch (IOException ignored) { |
| // Ignore and return whether lock file still exists |
| } |
| return !lockFile.exists(); |
| } |
| |
| /** |
| * Get the lock file corresponding to the given file. |
| * |
| * @param file |
| * @return lock file |
| */ |
| static File getLockFile(File file) { |
| return new File(file.getParentFile(), |
| file.getName() + LOCK_SUFFIX); |
| } |
| |
| /** Filter to skip over active lock files when listing a directory. */ |
| static final FilenameFilter FILTER = (File dir, |
| String name) -> !name.endsWith(LOCK_SUFFIX); |
| |
| private final File ref; |
| |
| private final File lck; |
| |
| private boolean haveLck; |
| |
| FileOutputStream os; |
| |
| private boolean needSnapshot; |
| |
| boolean fsync; |
| |
| private FileSnapshot commitSnapshot; |
| |
| private LockToken token; |
| |
| /** |
| * Create a new lock for any file. |
| * |
| * @param f |
| * the file that will be locked. |
| */ |
| public LockFile(File f) { |
| ref = f; |
| lck = getLockFile(ref); |
| } |
| |
| /** |
| * Try to establish the lock. |
| * |
| * @return true if the lock is now held by the caller; false if it is held |
| * by someone else. |
| * @throws java.io.IOException |
| * the temporary output file could not be created. The caller |
| * does not hold the lock. |
| */ |
| public boolean lock() throws IOException { |
| FileUtils.mkdirs(lck.getParentFile(), true); |
| try { |
| token = FS.DETECTED.createNewFileAtomic(lck); |
| } catch (IOException e) { |
| LOG.error(JGitText.get().failedCreateLockFile, lck, e); |
| throw e; |
| } |
| if (token.isCreated()) { |
| haveLck = true; |
| try { |
| os = new FileOutputStream(lck); |
| } catch (IOException ioe) { |
| unlock(); |
| throw ioe; |
| } |
| } else { |
| closeToken(); |
| } |
| return haveLck; |
| } |
| |
| /** |
| * Try to establish the lock for appending. |
| * |
| * @return true if the lock is now held by the caller; false if it is held |
| * by someone else. |
| * @throws java.io.IOException |
| * the temporary output file could not be created. The caller |
| * does not hold the lock. |
| */ |
| public boolean lockForAppend() throws IOException { |
| if (!lock()) |
| return false; |
| copyCurrentContent(); |
| return true; |
| } |
| |
| /** |
| * Copy the current file content into the temporary file. |
| * <p> |
| * This method saves the current file content by inserting it into the |
| * temporary file, so that the caller can safely append rather than replace |
| * the primary file. |
| * <p> |
| * This method does nothing if the current file does not exist, or exists |
| * but is empty. |
| * |
| * @throws java.io.IOException |
| * the temporary file could not be written, or a read error |
| * occurred while reading from the current file. The lock is |
| * released before throwing the underlying IO exception to the |
| * caller. |
| * @throws java.lang.RuntimeException |
| * the temporary file could not be written. The lock is released |
| * before throwing the underlying exception to the caller. |
| */ |
| public void copyCurrentContent() throws IOException { |
| requireLock(); |
| try { |
| try (FileInputStream fis = new FileInputStream(ref)) { |
| if (fsync) { |
| FileChannel in = fis.getChannel(); |
| long pos = 0; |
| long cnt = in.size(); |
| while (0 < cnt) { |
| long r = os.getChannel().transferFrom(in, pos, cnt); |
| pos += r; |
| cnt -= r; |
| } |
| } else { |
| final byte[] buf = new byte[2048]; |
| int r; |
| while ((r = fis.read(buf)) >= 0) |
| os.write(buf, 0, r); |
| } |
| } |
| } catch (FileNotFoundException fnfe) { |
| if (ref.exists()) { |
| unlock(); |
| throw fnfe; |
| } |
| // Don't worry about a file that doesn't exist yet, it |
| // conceptually has no current content to copy. |
| // |
| } catch (IOException | RuntimeException | Error ioe) { |
| unlock(); |
| throw ioe; |
| } |
| } |
| |
| /** |
| * Write an ObjectId and LF to the temporary file. |
| * |
| * @param id |
| * the id to store in the file. The id will be written in hex, |
| * followed by a sole LF. |
| * @throws java.io.IOException |
| * the temporary file could not be written. The lock is released |
| * before throwing the underlying IO exception to the caller. |
| * @throws java.lang.RuntimeException |
| * the temporary file could not be written. The lock is released |
| * before throwing the underlying exception to the caller. |
| */ |
| public void write(ObjectId id) throws IOException { |
| byte[] buf = new byte[Constants.OBJECT_ID_STRING_LENGTH + 1]; |
| id.copyTo(buf, 0); |
| buf[Constants.OBJECT_ID_STRING_LENGTH] = '\n'; |
| write(buf); |
| } |
| |
| /** |
| * Write arbitrary data to the temporary file. |
| * |
| * @param content |
| * the bytes to store in the temporary file. No additional bytes |
| * are added, so if the file must end with an LF it must appear |
| * at the end of the byte array. |
| * @throws java.io.IOException |
| * the temporary file could not be written. The lock is released |
| * before throwing the underlying IO exception to the caller. |
| * @throws java.lang.RuntimeException |
| * the temporary file could not be written. The lock is released |
| * before throwing the underlying exception to the caller. |
| */ |
| public void write(byte[] content) throws IOException { |
| requireLock(); |
| try { |
| if (fsync) { |
| FileChannel fc = os.getChannel(); |
| ByteBuffer buf = ByteBuffer.wrap(content); |
| while (0 < buf.remaining()) |
| fc.write(buf); |
| fc.force(true); |
| } else { |
| os.write(content); |
| } |
| os.close(); |
| os = null; |
| } catch (IOException | RuntimeException | Error ioe) { |
| unlock(); |
| throw ioe; |
| } |
| } |
| |
| /** |
| * Obtain the direct output stream for this lock. |
| * <p> |
| * The stream may only be accessed once, and only after {@link #lock()} has |
| * been successfully invoked and returned true. Callers must close the |
| * stream prior to calling {@link #commit()} to commit the change. |
| * |
| * @return a stream to write to the new file. The stream is unbuffered. |
| */ |
| public OutputStream getOutputStream() { |
| requireLock(); |
| |
| final OutputStream out; |
| if (fsync) |
| out = Channels.newOutputStream(os.getChannel()); |
| else |
| out = os; |
| |
| return new OutputStream() { |
| @Override |
| public void write(byte[] b, int o, int n) |
| throws IOException { |
| out.write(b, o, n); |
| } |
| |
| @Override |
| public void write(byte[] b) throws IOException { |
| out.write(b); |
| } |
| |
| @Override |
| public void write(int b) throws IOException { |
| out.write(b); |
| } |
| |
| @Override |
| public void close() throws IOException { |
| try { |
| if (fsync) |
| os.getChannel().force(true); |
| out.close(); |
| os = null; |
| } catch (IOException | RuntimeException | Error ioe) { |
| unlock(); |
| throw ioe; |
| } |
| } |
| }; |
| } |
| |
| void requireLock() { |
| if (os == null) { |
| unlock(); |
| throw new IllegalStateException(MessageFormat.format(JGitText.get().lockOnNotHeld, ref)); |
| } |
| } |
| |
| /** |
| * Request that {@link #commit()} remember modification time. |
| * <p> |
| * This is an alias for {@code setNeedSnapshot(true)}. |
| * |
| * @param on |
| * true if the commit method must remember the modification time. |
| */ |
| public void setNeedStatInformation(boolean on) { |
| setNeedSnapshot(on); |
| } |
| |
| /** |
| * Request that {@link #commit()} remember the |
| * {@link org.eclipse.jgit.internal.storage.file.FileSnapshot}. |
| * |
| * @param on |
| * true if the commit method must remember the FileSnapshot. |
| */ |
| public void setNeedSnapshot(boolean on) { |
| needSnapshot = on; |
| } |
| |
| /** |
| * Request that {@link #commit()} force dirty data to the drive. |
| * |
| * @param on |
| * true if dirty data should be forced to the drive. |
| */ |
| public void setFSync(boolean on) { |
| fsync = on; |
| } |
| |
| /** |
| * Wait until the lock file information differs from the old file. |
| * <p> |
| * This method tests the last modification date. If both are the same, this |
| * method sleeps until it can force the new lock file's modification date to |
| * be later than the target file. |
| * |
| * @throws java.lang.InterruptedException |
| * the thread was interrupted before the last modified date of |
| * the lock file was different from the last modified date of |
| * the target file. |
| */ |
| public void waitForStatChange() throws InterruptedException { |
| FileSnapshot o = FileSnapshot.save(ref); |
| FileSnapshot n = FileSnapshot.save(lck); |
| long fsTimeResolution = FS.getFileStoreAttributes(lck.toPath()) |
| .getFsTimestampResolution().toNanos(); |
| while (o.equals(n)) { |
| TimeUnit.NANOSECONDS.sleep(fsTimeResolution); |
| try { |
| Files.setLastModifiedTime(lck.toPath(), |
| FileTime.from(Instant.now())); |
| } catch (IOException e) { |
| n.waitUntilNotRacy(); |
| } |
| n = FileSnapshot.save(lck); |
| } |
| } |
| |
| /** |
| * Commit this change and release the lock. |
| * <p> |
| * If this method fails (returns false) the lock is still released. |
| * |
| * @return true if the commit was successful and the file contains the new |
| * data; false if the commit failed and the file remains with the |
| * old data. |
| * @throws java.lang.IllegalStateException |
| * the lock is not held. |
| */ |
| public boolean commit() { |
| if (os != null) { |
| unlock(); |
| throw new IllegalStateException(MessageFormat.format(JGitText.get().lockOnNotClosed, ref)); |
| } |
| |
| saveStatInformation(); |
| try { |
| FileUtils.rename(lck, ref, StandardCopyOption.ATOMIC_MOVE); |
| haveLck = false; |
| closeToken(); |
| return true; |
| } catch (IOException e) { |
| unlock(); |
| return false; |
| } |
| } |
| |
| private void closeToken() { |
| if (token != null) { |
| token.close(); |
| token = null; |
| } |
| } |
| |
| private void saveStatInformation() { |
| if (needSnapshot) |
| commitSnapshot = FileSnapshot.save(lck); |
| } |
| |
| /** |
| * Get the modification time of the output file when it was committed. |
| * |
| * @return modification time of the lock file right before we committed it. |
| * @deprecated use {@link #getCommitLastModifiedInstant()} instead |
| */ |
| @Deprecated |
| public long getCommitLastModified() { |
| return commitSnapshot.lastModified(); |
| } |
| |
| /** |
| * Get the modification time of the output file when it was committed. |
| * |
| * @return modification time of the lock file right before we committed it. |
| */ |
| public Instant getCommitLastModifiedInstant() { |
| return commitSnapshot.lastModifiedInstant(); |
| } |
| |
| /** |
| * Get the {@link FileSnapshot} just before commit. |
| * |
| * @return get the {@link FileSnapshot} just before commit. |
| */ |
| public FileSnapshot getCommitSnapshot() { |
| return commitSnapshot; |
| } |
| |
| /** |
| * Update the commit snapshot {@link #getCommitSnapshot()} before commit. |
| * <p> |
| * This may be necessary if you need time stamp before commit occurs, e.g |
| * while writing the index. |
| */ |
| public void createCommitSnapshot() { |
| saveStatInformation(); |
| } |
| |
| /** |
| * Unlock this file and abort this change. |
| * <p> |
| * The temporary file (if created) is deleted before returning. |
| */ |
| public void unlock() { |
| if (os != null) { |
| try { |
| os.close(); |
| } catch (IOException e) { |
| LOG.error(MessageFormat |
| .format(JGitText.get().unlockLockFileFailed, lck), e); |
| } |
| os = null; |
| } |
| |
| if (haveLck) { |
| haveLck = false; |
| try { |
| FileUtils.delete(lck, FileUtils.RETRY); |
| } catch (IOException e) { |
| LOG.error(MessageFormat |
| .format(JGitText.get().unlockLockFileFailed, lck), e); |
| } finally { |
| closeToken(); |
| } |
| } |
| } |
| |
| /** {@inheritDoc} */ |
| @SuppressWarnings("nls") |
| @Override |
| public String toString() { |
| return "LockFile[" + lck + ", haveLck=" + haveLck + "]"; |
| } |
| } |