I use NFS V4 to test the java FileLock.
The 192.168.1.233 machine is NFS Server, the nfs configuration are
/home/hdfs.ha/share 192.168.1.221(rw,sync,no_root_squash)
/home/hdfs.ha/share 192.168.1.222(rw,sync,no_root_squash)
in /etc/exports file.
I run below commands to start nfs server:
service nfs start
service nfslock start
The 192.168.1.221 and 192.168.1.222 machines are NFS Client, the nfs
configuration is
192.168.1.223:/home/hdfs.ha/share /home/hdfs.ha/share nfs
rsize=8192,wsize=8192,timeo=14,intr in /etc/fstab file.
I run below commands to start nfs client:
service nfs start
service nfslock start
I write one programm to receive file lock:
public class FileLockTest {
FileLock lock;
public void lock(String path,boolean isShare) throws IOException {
this.lock = tryLock(path,isShare);
if (lock == null) {
String msg = "Cannot lock storage " + path
+ ". The directory is already locked.";
System.out.println(msg);
throw new IOException(msg);
}
}
private FileLock tryLock(String path,boolean isShare) throws
IOException {
boolean deletionHookAdded = false;
File lockF = new File(path);
if (!lockF.exists()) {
lockF.deleteOnExit();
deletionHookAdded = true;
}
RandomAccessFile file = new RandomAccessFile(lockF, "rws");
FileLock res = null;
try {
res = file.getChannel().tryLock(0,Long.MAX_VALUE,isShare);
} catch (OverlappingFileLockException oe) {
file.close();
return null;
} catch (IOException e) {
e.printStackTrace();
file.close();
throw e;
}
if (res != null && !deletionHookAdded) {
// If the file existed prior to our startup, we didn't
// call deleteOnExit above. But since we successfully locked
// the dir, we can take care of cleaning it up.
lockF.deleteOnExit();
}
return res;
}
public static void main(String[] s) {
FileLockTest fileLockTest =new FileLockTest();
try {
fileLockTest.lock(s[0], Boolean.valueOf(s[1]));
Thread.sleep(1000*60*60*1);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
I do two test cases.
1. The network is OK
I run " java -cp ./filelock.jar lock.FileLockTest
/home/hdfs.ha/share/test.lock false" command in 192.168.1.221 to hold file
lock, and then I run same command to hold same file lock in 192.168.1.222,
throw below exception:
Cannot lock storage /home/hdfs.ha/share/test.lock. The directory is already
locked.
java.io.IOException: Cannot lock storage /home/hdfs.ha/share/test.lock. The
directory is already locked.
at lock.FileLockTest.lock(FileLockTest.java:18)
at lock.FileLockTest.main(FileLockTest.java:53)
2. machine which hold file lock is diconnected
I run " java -cp ./filelock.jar lock.FileLockTest
/home/hdfs.ha/share/test.lock false" command on 192.168.1.221, then
192.168.1.221 machine is disconnected from network . After three minutes ,
I run the " java -cp ./filelock.jar lock.FileLockTest
/home/hdfs.ha/share/test.lock false" command on 192.168.1.222, that can
hold the file lock.
I use "mount | grep nfs" command to examine the mount nfs directory on
192.168.1.221, the share directory /home/hdfs.ha/share/ is disappear on
192.168.1.221 machine. So I think when the machine is disconnected for
a long time, other machine can receive the same file lock.
