Examples of FileLock

com.arjuna.ats.arjuna.utils.FileLock
Sometimes it is necessary to lock a file at the disk level. Since there is no native Java way of locking a file, we have to implement our own. Unfortunately, it appears as though we can only assume that rename is atomic. We base the locking on this then: rename the lock file and update it with the lock owners. How it works: for every file we want to lock we create an _lock file. This file contains information about who is locking the file, and in what mode. (Single writer, multiple readers.) To guarantee atomicity of update, we move (rename) the actual file each time we want to lock it and update the lock file. When this is done, we move (rename) it back. Almost like a two-phase commit protocol! Currently we don't support re-entrant locking. @author Mark Little (mark@arjuna.com) @version $Id: FileLock.java 2342 2006-03-30 13:06:17Z $ @since JTS 1.0. @message com.arjuna.ats.arjuna.utils.FileLock_1 [com.arjuna.ats.arjuna.utils.FileLock_1] - FileLock.lock called for {0} @message com.arjuna.ats.arjuna.utils.FileLock_2 [com.arjuna.ats.arjuna.utils.FileLock_2] - FileLock.unlock called for {0} @message com.arjuna.ats.arjuna.utils.FileLock_3 [com.arjuna.ats.arjuna.utils.FileLock_3] - FileLock.createFile called for {0} @message com.arjuna.ats.arjuna.utils.FileLock_4 [com.arjuna.ats.arjuna.utils.FileLock_4] - An error occurred while creating file {0} @message com.arjuna.ats.arjuna.utils.FileLock_5 [com.arjuna.ats.arjuna.utils.FileLock_5] - FileLock.lockFile called for {0} @message com.arjuna.ats.arjuna.utils.FileLock_6 [com.arjuna.ats.arjuna.utils.FileLock_6] - FileLock.unlockFile called for {0}
java.nio.channels.FileLock
A FileLock represents a locked region of a file.
Locks have certain properties that enable collaborating processes to avoid the lost update problem, or reading inconsistent data.

logically, a file lock can be 'exclusive' or 'shared'. Multiple processes can hold shared locks on the same region of a file, but only a single process can hold an exclusive lock on a given region of a file and no other process can simultaneously hold a shared lock overlapping the exclusive lock. An application can determine whether a FileLock is shared or exclusive via the isShared() API.

Locks held by a particular process cannot overlap one another. Applications can determine whether a proposed lock will overlap by using the overlaps(long, long)
Locks are shared amongst all threads in the acquiring process, and are therefore unsuitable for intra-process synchronization.
Once a lock is acquired it is immutable in all its state except isValid(). The lock will initially be valid, but may be rendered invalid by explicit removal of the lock, using release(), or implictly by closing the channel or exiting the process (terminating the JVM). Platform dependencies Locks are intended to be true platform operating system file locks, and therefore locks held by the JVM process will be visible to other OS processes. The characteristics of the underlying OS locks will show through in the Java implementation. For example, some platforms' locks are 'mandatory' -- meaning the operating system enforces the locks on processes that attempt to access locked regions of file; whereas other platforms' locks are only 'advisory' -- meaning that processes are required to collaborate on ensuring locks are acquired and there is a potential for processes not to play well. The only safe answer is to assume that the platform is adopting advisory locks an always acquire shared locks when reading a region of file. On some platforms the presence of a lock will prevent the file being memory mapped. On some platforms closing a channel on a given file handle will release all the locks held on that file -- even if there are other channels open on the same file (their locks will be released). The safe option here is to ensure that you only acquire locks on a single channel for a particular file, and that becomes the synchronization point. Further care should be exercised when locking files maintained on network file systems since they often have further limitations.



org.exist.storage.lock.FileLock

Cooperative inter-process file locking, used to synchronize access to database files across processes, i.e. across different Java VMs or separate database instances within one VM. This is similar to the native file locks provided by Java NIO. However, the NIO implementation has various problems. Among other things, we observed that locks were not properly released on WinXP. FileLock implements a cooperative approach. The class attempts to write a lock file at the specified location. Every lock file stores 1) a magic word to make sure that the file was really written by eXist, 2) a heartbeat timestamp. The procedure for acquiring the lock in {@link #tryLock()} is as follows:If a lock file does already exist in the specified location, we check its heartbeat timestamp. If the timestamp is more than {@link #HEARTBEAT} milliseconds in the past, we assumethat the lock is stale and its owner process has died. The lock file is removed and we create a new one. If the heartbeat indicates that the owner process is still alive, the lock attempt is aborted and {@link #tryLock()} returns false.Otherwise, we create a new lock file and start a daemon thread to periodically update the lock file's heart-beat value.
@author Wolfgang Meier



org.h2.store.FileLock

The file lock is used to lock a database so that only one process can write to it. It uses a cooperative locking protocol. Usually a .lock.db file is used, but locking by creating a socket is supported as well.



org.openide.filesystems.FileLock




Examples of java.nio.channels.FileLock
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172       boolean revokeLock = false;


      File lockedFile = new File(lockDir, LOCK_FILE_NAME);
      RandomAccessFile raf = new RandomAccessFile(lockedFile, "rw");
      try {
        FileLock fileLock = raf.getChannel().tryLock();


        if (fileLock != null) {
          logger.warn("Removing invalid lock {}", getLockedBy());
          fileLock.release();
          revokeLock = true;
        }
      }
      catch (OverlappingFileLockException exc) {
        // lock is still valid

View Full Code Here



Examples of java.nio.channels.FileLock
143
144
145
146
147
148
149
150
151
152
153
154
155     byte[] data = compose();
    if (!f.exists()) {
      f.createNewFile();
    }
    FileChannel fc = new FileOutputStream(f).getChannel();
    FileLock fl = fc.lock();
    try {
      fc.write(ByteBuffer.wrap(data));
    } finally {
      fl.release();
      fc.close();
    }
  }

View Full Code Here

Examples of java.nio.channels.FileLock
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235       try {
        /*
         * lock file
         */
        FileChannel channel = output.getChannel();
        FileLock lock = channel.tryLock();
        if (lock == null)
          throw new ServiceInterruption("Could not lock file: '"+file+"'",null,1000L,-1L,10,false);


        try {


          /*
           * write file
           */
          InputStream input = document.getBinaryStream();
          byte buf[] = new byte[1024];
          int len;
          while((len = input.read(buf)) != -1) {
            output.write(buf, 0, len);
          }
          output.flush();
        } finally {
          // Unlock
          try {
            if (lock != null) {
              lock.release();
            }
          } catch (ClosedChannelException e) {
          }
        }
      } finally {
 

View Full Code Here

Examples of java.nio.channels.FileLock
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178      * checks if the working directory is already in use by some other directory service, if yes
     * then throws a runtime exception else will obtain the lock on the working directory
     */
    private void lockWorkDir()
    {
        FileLock fileLock = null;


        try
        {
            lockFile = new RandomAccessFile( new File( instanceLayout.getInstanceDirectory(), LOCK_FILE_NAME ), "rw" );
            try
            {
                fileLock = lockFile.getChannel().tryLock( 0, 1, false );
            }
            catch ( IOException e )
            {
                // shoudn't happen, but log
                LOG.error( "failed to lock the work directory", e );
            }
            catch ( OverlappingFileLockException e ) // thrown if we can't get a lock
            {
                fileLock = null;
            }
        }
        catch ( FileNotFoundException e )
        {
            // shouldn't happen, but log anyway
            LOG.error( "failed to lock the work directory", e );
        }


        if ( ( fileLock == null ) || ( !fileLock.isValid() ) )
        {
            String message = "the working directory " + instanceLayout.getRunDirectory()
                + " has been locked by another directory service.";
            LOG.error( message );
            throw new RuntimeException( message );
 

View Full Code Here

Examples of java.nio.channels.FileLock
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426     if (!oldF.exists())
      return false;
    // check the layout version inside the storage file
    // Lock and Read old storage file
    RandomAccessFile oldFile = new RandomAccessFile(oldF, "rws");
    FileLock oldLock = oldFile.getChannel().tryLock();
    try {
      oldFile.seek(0);
      int oldVersion = oldFile.readInt();
      if (oldVersion < LAST_PRE_UPGRADE_LAYOUT_VERSION)
        return false;
    } finally {
      oldLock.release();
      oldFile.close();
    }
    return true;
  }

View Full Code Here

Examples of java.nio.channels.FileLock
58
59
60
61
62
63
64
65
66
67
68             if (LOG.isDebugEnabled()) {
                LOG.debug("Locking the file: " + file + " using the lock file name: " + lockFileName);
            }


            FileChannel channel = new RandomAccessFile(lockFileName, "rw").getChannel();
            FileLock lock = channel.lock();
            if (lock != null) {
                exchange.setProperty("org.apache.camel.fileChannel", channel);
                exchange.setProperty("org.apache.camel.file.lock", lock);
                exchange.setProperty("org.apache.camel.file.lock.name", lockFileName);
                return true;

View Full Code Here

Examples of java.nio.channels.FileLock
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285       try {
        /*
         * lock file
         */
        FileChannel channel = output.getChannel();
        FileLock lock = channel.tryLock();
        if (lock == null)
          throw new ServiceInterruption("Could not lock file: '"+outputPath+"'",null,1000L,-1L,10,false);


        try {


          /*
           * write file
           */
          InputStream input = document.getBinaryStream();
          byte buf[] = new byte[65536];
          int len;
          while((len = input.read(buf)) != -1) {
            output.write(buf, 0, len);
          }
          output.flush();
        } finally {
          // Unlock
          try {
            if (lock != null) {
              lock.release();
            }
          } catch (ClosedChannelException e) {
          }
        }
      } finally {
 

View Full Code Here

Examples of java.nio.channels.FileLock
313
314
315
316
317
318
319
320
321
322
323         public boolean tryLock(File file) {
            try {
                if (file.getParentFile().exists() || file.getParentFile().mkdirs()) {
                    // this must not be closed until unlock
                    RandomAccessFile raf = new RandomAccessFile(file, "rw");
                    FileLock l = raf.getChannel().tryLock();
                    if (l != null) {
                        synchronized (this) {
                            locks.put(file, new LockData(raf, l));
                        }
                        return true;

View Full Code Here

Examples of java.nio.channels.FileLock
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101     private synchronized void writeToFile(String action) {
        Date date = new Date();
        try {
            FileOutputStream out = new FileOutputStream(logFile, true);
            FileChannel channel = out.getChannel();
            FileLock lock = channel.lock(0, Long.MAX_VALUE, false);
            PrintWriter writer = new PrintWriter(out, false);
            writer.println(DATE_FORMAT.format(date)+" - "+action+" - "+username);
            writer.flush();
            writer.close();
            if(lock.isValid()) {
                lock.release();
            }
        } catch (IOException e) {
            throw new RuntimeException("Unable to write to authentication log file", e);
        }
    }

View Full Code Here

Examples of java.nio.channels.FileLock
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209      * checks if the working directory is already in use by some other directory service, if yes
     * then throws a runtime exception else will obtain the lock on the working directory
     */
    private void lockWorkDir()
    {
        FileLock fileLock = null;


        try
        {
            lockFile = new RandomAccessFile( new File( instanceLayout.getInstanceDirectory(), LOCK_FILE_NAME ), "rw" );
            try
            {
                fileLock = lockFile.getChannel().tryLock( 0, 1, false );
            }
            catch ( IOException e )
            {
                // shoudn't happen, but log
                LOG.error( "failed to lock the work directory", e );
            }
            catch ( OverlappingFileLockException e ) // thrown if we can't get a lock
            {
                fileLock = null;
            }
        }
        catch ( FileNotFoundException e )
        {
            // shouldn't happen, but log anyway
            LOG.error( "failed to lock the work directory", e );
        }


        if ( ( fileLock == null ) || ( !fileLock.isValid() ) )
        {
            String message = "the working directory " + instanceLayout.getRunDirectory()
                + " has been locked by another directory service.";
            LOG.error( message );
            throw new RuntimeException( message );
 

View Full Code Here


0
1
2
3
4
5



TOP


Copyright © 2018 www.massapi.com. All rights reserved.
All source code are property of their respective owners. Java is a trademark of Sun Microsystems, Inc and owned by ORACLE Inc. Contact coftware#gmail.com.