tikhomirov@486: /*
tikhomirov@486:  * Copyright (c) 2012 TMate Software Ltd
tikhomirov@486:  *  
tikhomirov@486:  * This program is free software; you can redistribute it and/or modify
tikhomirov@486:  * it under the terms of the GNU General Public License as published by
tikhomirov@486:  * the Free Software Foundation; version 2 of the License.
tikhomirov@486:  *
tikhomirov@486:  * This program is distributed in the hope that it will be useful,
tikhomirov@486:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
tikhomirov@486:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
tikhomirov@486:  * GNU General Public License for more details.
tikhomirov@486:  *
tikhomirov@486:  * For information on how to redistribute this software under
tikhomirov@486:  * the terms of a license other than GNU General Public License
tikhomirov@486:  * contact TMate Software at support@hg4j.com
tikhomirov@486:  */
tikhomirov@487: package org.tmatesoft.hg.repo;
tikhomirov@486: 
tikhomirov@486: import java.io.File;
tikhomirov@486: import java.io.FileInputStream;
tikhomirov@486: import java.io.FileOutputStream;
tikhomirov@486: import java.io.IOException;
tikhomirov@486: import java.lang.management.ManagementFactory;
tikhomirov@486: import java.net.InetAddress;
tikhomirov@486: import java.nio.ByteBuffer;
tikhomirov@486: import java.nio.channels.FileChannel;
tikhomirov@486: 
tikhomirov@489: import org.tmatesoft.hg.internal.Experimental;
tikhomirov@487: import org.tmatesoft.hg.internal.Internals;
tikhomirov@486: 
tikhomirov@486: /**
tikhomirov@486:  * NOT SAFE FOR MULTITHREAD USE!
tikhomirov@486:  * 
tikhomirov@489:  * <p>Usage:
tikhomirov@489:  * <pre>
tikhomirov@489:  * HgRepositoryLock lock = hgRepo.getWorkingDirLock();
tikhomirov@489:  * try {
tikhomirov@489:  *     // Actually lock the repo
tikhomirov@489:  *     lock.acquire();
tikhomirov@489:  *     ///
tikhomirov@489:  *     // do whatever modifies working directory
tikhomirov@489:  *     ...
tikhomirov@489:  * } finally {
tikhomirov@489:  *     if (lock.isLocked()) {
tikhomirov@489:  *         // this check is needed not to release() 
tikhomirov@489:  *         // erroneously in case acquire() failed (e.g. due to timeout)
tikhomirov@489:  *         lock.release();
tikhomirov@489:  *     }
tikhomirov@489:  * 
tikhomirov@489:  * </pre>
tikhomirov@489:  * 
tikhomirov@486:  * Unlike original mechanism, we don't use symlinks, rather files, as it's easier to implement
tikhomirov@486:  * 
tikhomirov@489:  * @see http://code.google.com/p/hg4j/issues/detail?id=35
tikhomirov@486:  * @author Artem Tikhomirov
tikhomirov@486:  * @author TMate Software Ltd.
tikhomirov@486:  */
tikhomirov@489: @Experimental(reason="Work in progress")
tikhomirov@487: public class HgRepositoryLock {
tikhomirov@486: 	/*
tikhomirov@488: 	 * Lock .hg/ except .hg/store/      .hg/wlock (new File(hgRepo.getRepoRoot(),"wlock"))
tikhomirov@488: 	 * Lock .hg/store/                  .hg/store/lock (HgRepository.repoPathHelper("lock"))
tikhomirov@486: 	 */
tikhomirov@486: 
tikhomirov@486: 	private final File lockFile;
tikhomirov@486: 	private int use = 0;
tikhomirov@486: 	private final int timeoutSeconds;
tikhomirov@486: 	
tikhomirov@487: 	 HgRepositoryLock(File lock, int timeoutInSeconds) {
tikhomirov@486: 		lockFile = lock;
tikhomirov@486: 		timeoutSeconds = timeoutInSeconds;
tikhomirov@486: 	}
tikhomirov@486: 
tikhomirov@486: 	/**
tikhomirov@486: 	 * Tries to read lock file and supplies hostname:pid (or just pid) information from there
tikhomirov@486: 	 * @return <code>null</code> if no lock file available at the moment
tikhomirov@486: 	 */
tikhomirov@486: 	public String readLockInfo() {
tikhomirov@486: 		if (lockFile.exists()) {
tikhomirov@486: 			try {
tikhomirov@486: 				byte[] bytes = read(lockFile);
tikhomirov@486: 				if (bytes != null && bytes.length > 0) {
tikhomirov@486: 					return new String(bytes);
tikhomirov@486: 				}
tikhomirov@486: 			} catch (Exception ex) {
tikhomirov@486: 				// deliberately ignored
tikhomirov@486: 			}
tikhomirov@486: 		}
tikhomirov@486: 		return null;
tikhomirov@486: 	}
tikhomirov@486: 	
tikhomirov@489: 	/**
tikhomirov@489: 	 * @return <code>true</code> if we hold the lock
tikhomirov@489: 	 */
tikhomirov@486: 	public boolean isLocked() {
tikhomirov@486: 		return use > 0;
tikhomirov@486: 	}
tikhomirov@486: 
tikhomirov@489: 	/**
tikhomirov@489: 	 * Perform actual locking. Waits for timeout (if specified at construction time)
tikhomirov@489: 	 * before throwing {@link HgInvalidStateException} in case lock is not available 
tikhomirov@489: 	 * immediately.
tikhomirov@489: 	 * 
tikhomirov@489: 	 * <p>Multiple calls are possible, but corresponding number of {@link #release()} 
tikhomirov@489: 	 * calls shall be made.
tikhomirov@489: 	 */
tikhomirov@486: 	public void acquire() {
tikhomirov@486: 		if (use > 0) {
tikhomirov@486: 			use++;
tikhomirov@486: 			return;
tikhomirov@486: 		}
tikhomirov@486: 		StringBuilder lockDescription = new StringBuilder();
tikhomirov@486: 		lockDescription.append(getHostname());
tikhomirov@486: 		lockDescription.append(':');
tikhomirov@486: 		lockDescription.append(getPid());
tikhomirov@486: 		byte[] bytes = lockDescription.toString().getBytes();
tikhomirov@487: 		long stopTime = timeoutSeconds < 0 ? -1 : (System.currentTimeMillis() + timeoutSeconds*1000);
tikhomirov@486: 		do {
tikhomirov@486: 			synchronized(this) {
tikhomirov@486: 				try {
tikhomirov@486: 					if (!lockFile.exists()) {
tikhomirov@486: 						write(lockFile, bytes);
tikhomirov@486: 						use++;
tikhomirov@486: 						return;
tikhomirov@486: 					}
tikhomirov@486: 				} catch (IOException ex) {
tikhomirov@486: 					// deliberately ignored
tikhomirov@486: 				}
tikhomirov@486: 				try {
tikhomirov@486: 					wait(1000);
tikhomirov@486: 				} catch (InterruptedException ex) {
tikhomirov@486: 					// deliberately ignored
tikhomirov@486: 				}
tikhomirov@486: 			}
tikhomirov@486: 			
tikhomirov@487: 		} while (stopTime == -1/*no timeout*/ || System.currentTimeMillis() <= stopTime);
tikhomirov@486: 		String msg = String.format("Failed to aquire lock, waited for %d seconds, present owner: '%s'", timeoutSeconds, readLockInfo());
tikhomirov@486: 		throw new HgInvalidStateException(msg);
tikhomirov@486: 	}
tikhomirov@486: 	
tikhomirov@489: 	/**
tikhomirov@489: 	 * Release lock we own
tikhomirov@489: 	 */
tikhomirov@486: 	public void release() {
tikhomirov@486: 		if (use == 0) {
tikhomirov@489: 			throw new HgInvalidStateException("Lock is not held!");
tikhomirov@486: 		}
tikhomirov@486: 		use--;
tikhomirov@486: 		if (use > 0) {
tikhomirov@486: 			return;
tikhomirov@486: 		}
tikhomirov@486: 		// do release
tikhomirov@486: 		lockFile.delete();
tikhomirov@486: 	}
tikhomirov@486: 
tikhomirov@486: 	protected String getHostname() {
tikhomirov@486: 		try {
tikhomirov@486: 			return InetAddress.getLocalHost().getHostName();
tikhomirov@486: 		} catch (Exception ex) {
tikhomirov@486: 			return "localhost";
tikhomirov@486: 		}
tikhomirov@486: 	}
tikhomirov@486: 
tikhomirov@486: 	protected int getPid() {
tikhomirov@486: 		try {
tikhomirov@486: 			// @see http://blog.igorminar.com/2007/03/how-java-application-can-discover-its.html
tikhomirov@486: 			if (!Internals.runningOnWindows()) {
tikhomirov@486: 				File f = new File("/proc/self");
tikhomirov@486: 				if (f.exists()) {
tikhomirov@486: 					// /proc/self is a symlink to /proc/pid/ directory
tikhomirov@486: 					return Integer.parseInt(f.getCanonicalFile().getName());
tikhomirov@486: 				}
tikhomirov@486: 			}
tikhomirov@486: 			String rtBean = ManagementFactory.getRuntimeMXBean().getName();
tikhomirov@486: 			int x;
tikhomirov@486: 			if ((x = rtBean.indexOf('@')) != -1) {
tikhomirov@486: 				return Integer.parseInt(rtBean.substring(0, x));
tikhomirov@486: 			}
tikhomirov@486: 			return -1;
tikhomirov@486: 		} catch (Exception ex) {
tikhomirov@486: 			return -1;
tikhomirov@486: 		}
tikhomirov@486: 	}
tikhomirov@486: 
tikhomirov@486: 	private static void write(File f, byte[] content) throws IOException {
tikhomirov@486: 		FileOutputStream fos = new FileOutputStream(f);
tikhomirov@486: 		fos.write(content);
tikhomirov@486: 		fos.close();
tikhomirov@486: 	}
tikhomirov@486: 
tikhomirov@486: 	private static byte[] read(File f) throws IOException {
tikhomirov@486: 		FileChannel fc = new FileInputStream(f).getChannel();
tikhomirov@486: 		ByteBuffer bb = ByteBuffer.allocate(Internals.ltoi(fc.size()));
tikhomirov@486: 		fc.read(bb);
tikhomirov@486: 		fc.close();
tikhomirov@486: 		return bb.array();
tikhomirov@486: 	}
tikhomirov@486: }