Thanks for all suggestions. I have gotten it to work.
Avinash
On Mon, Jul 14, 2008 at 8:23 AM, Benjamin Reed <[EMAIL PROTECTED]> wrote:
> The easiest way to fix this code is to move the Collections.sort(values) to
> right after the zk.getChildren() and then use the following Comparator with
> Collections.sort() and Collections.binarySearch():
>
> /* This Comparator defines an ordering such that the strings with
> * the lowest sequence numbers are first in sequence sorted order
> * followed by strings without sequence numbers in lexographical
> * order. This class assumes that a '-' preceeds the sequence
> * number. */
> class SequenceComparator implements Comparator<String> {
>
> @Override
> public int compare(String o1, String o2) {
> int s1 = getSequence(o1);
> int s2 = getSequence(o2);
> if (s1 == -1 && s2 == -1) {
> return o1.compareTo(o2);
> }
> return s1 == -1 ? 1 : s2 == -1 ? -1 : s1 - s2 ? : -1;
> }
>
> /* Returns the sequence suffix of s. This method assumes that
> * the sequence number is prefixed with a '-'. */
> private int getSequence(String s) {
> int i = s.lastIndexOf('-');
> if (i != -1) {
> try {
> return Integer.parseInt(s.substring(i+1));
> // If an exception occurred we misdetected a sequence suffix,
> // so return -1.
> } catch(NumberFormatException e) {
> } catch(ArrayIndexOutOfBoundsException e) {
> }
> }
> return -1;
> }
> }
>
> ben
>
> On Thursday 10 July 2008 22:20:06 Avinash Lakshman wrote:
> > Hi
> >
> > I am trying to elect leader among 50 nodes. There is always one odd guy
> who
> > seems to think that someone else distinct from what some other nodes see
> as
> > leader. Could someone please tell me what is wrong with the following
> code
> > for leader election:
> >
> > public void electLeader()
> > {
> > ZooKeeper zk =
> StorageService.instance().getZooKeeperHandle();
> > String path = "/Leader";
> > try
> > {
> > String createPath = path +
> > "/L-";
> > LeaderElector.createLock_.lock();
> > while( true )
> > {
> > /* Get all znodes under the Leader znode */
> > List<String> values = zk.getChildren(path, false);
> > /*
> > * Get the first znode and if it is the
> > * pathCreated created above then the data
> > * in that znode is the leader's identity.
> > */
> > if ( leader_ == null )
> > {
> > leader_ = new AtomicReference<EndPoint>(
> > EndPoint.fromBytes( zk.getData(path + "/" + values.get(0), false, null) )
> > ); }
> > else
> > {
> > leader_.set( EndPoint.fromBytes( zk.getData(path
> +
> > "/" + values .get(0), false, null) ) );
> > /* Disseminate the state as to who the leader is.
> > */ onLeaderElection();
> > }
> > logger_.debug("Elected leader is " + leader_ + " @
> > znode " + ( path + "/" + values.get(0) ) );
> > Collections.sort(values);
> > /* We need only the last portion of this znode */
> > String[] peices = pathCreated_.split("/");
> > int index = Collections.binarySearch(values,
> > peices[peices.length - 1]);
> > if ( index > 0 )
> > {
> > String pathToCheck = path + "/" +
> values.get(index
> > - 1);
> > Stat stat = zk.exists(pathToCheck, true);
> > if ( stat != null )
> > {
> > logger_.debug("Awaiting my turn ...");
> > condition_.await();
> > logger_.debug("Checking to see if leader is
> > around ...");
> > }
> > }
> > else
> > {
> > break;
> > }
> > }
> > }
> > catch ( InterruptedException ex )
> > {
> > logger_.warn(LogUtil.throwableToString(ex));
> > }
> > catch ( KeeperException ex )
> > {
> > logger_.warn(LogUtil.throwableToString(ex));
> > }
> > finally
> > {
> > LeaderElector.createLock_.unlock();
> > }
> > }
> > }
> >
> > Thanks
> > Avinash
>
>
>
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