private object LockOperation()
{
do
{
if (id == null)
{
long sessionId = Zookeeper.SessionId;
string prefix = "x-" + sessionId + "-";
FindPrefixInChildren(prefix, Zookeeper, dir);
idName = new ZNodeName(id);
}
if (id == null) continue;
List<string> names = Zookeeper.GetChildren(dir, false);
if (names.IsEmpty())
{
LOG.Warn("No children in: " + dir + " when we've just " +
"created one! Lets recreate it...");
// lets force the recreation of the id
id = null;
}
else
{
// lets sort them explicitly (though they do seem to come back in order ususally :)
var sortedNames = new SortedSet<ZNodeName>();
foreach (string name in names)
{
sortedNames.Add(new ZNodeName(dir.Combine(name)));
}
ownerId = sortedNames.First().Name;
SortedSet<ZNodeName> lessThanMe = sortedNames.HeadSet(idName);
if (!lessThanMe.IsEmpty())
{
ZNodeName lastChildName = lessThanMe.Last();
lastChildId = lastChildName.Name;
if (LOG.IsDebugEnabled)
{
LOG.Debug("watching less than me node: " + lastChildId);
}
Stat stat = Zookeeper.Exists(lastChildId, new LockWatcher(this));
if (stat != null)
{
return false;
}
LOG.Warn("Could not find the stats for less than me: " + lastChildName.Name);
}
else
{
if (Owner)
{
OnLockAcquired();
return true;
}
}
}
} while (id == null);
return false;
}
public bool RunForLeader()
{
long sessionId = Zookeeper.SessionId;
string prefix = "election-" + sessionId + "-";
var names = Zookeeper.GetChildren(_path, false);
// See whether we have already run for election in this process
foreach (string name in names)
{
if (name.StartsWith(prefix))
{
_id = name;
if (Log.IsDebugEnabled)
{
Log.DebugFormat("Found id created last time: {0}", _id);
}
}
}
if (_id == null)
{
_id = Zookeeper.Create(_path.Combine(prefix), _data, Acl, CreateMode.EphemeralSequential);
if (Log.IsDebugEnabled)
{
Log.DebugFormat("Created id: {0}", _id);
}
}
_idName = new ZNodeName(_id);
names = Zookeeper.GetChildren(_path, false);
var sortedNames = new SortedSet<ZNodeName>();
foreach (var name in names)
{
sortedNames.Add(new ZNodeName(name));
}
var priors = sortedNames.HeadSet(_idName);
if (priors.Count == 0)
{
throw new InvalidOperationException("Count of priors is 0, but should at least include this node.");
}
if (priors.Count == 1)
{
IsOwner = true;
_watcher.TakeLeadership();
return true;
}
// only watch the node directly before us
ZNodeName penultimate = null, last = null;
foreach (var name in sortedNames)
{
penultimate = last;
last = name;
}
if (penultimate == null)
{
throw new InvalidOperationException("Penultimate value in priors is null, but count shoudl have been at least 2.");
}
var watchPath = _path.Combine(penultimate.Name);
if (Zookeeper.Exists(watchPath, new LeaderWatcher(this, watchPath, _watcher)) == null)
{
IsOwner = true;
_watcher.TakeLeadership();
return true;
}
return false;
}
