@SuppressWarnings("unchecked")
public T poll() throws Exception {
try {
List<String> list = zkClient.getChildren(root);
if (list.size() == 0) {
return null;
}
Collections.sort(
list,
new Comparator<String>() {
public int compare(String lhs, String rhs) {
return getNodeNumber(lhs, Node_NAME).compareTo(getNodeNumber(rhs, Node_NAME));
}
});
for (String nodeName : list) {
String nodeFullPath = root.concat("/").concat(nodeName);
try {
T node = (T) zkClient.readData(nodeFullPath);
zkClient.delete(nodeFullPath);
return node;
} catch (ZkNoNodeException e) {
// ignore
}
}
return null;
} catch (Exception e) {
throw ExceptionUtil.convertToRuntimeException(e);
}
}
public String enqueue(T element) {
try {
String sequential = _zkClient.createPersistentSequential(getElementRoughPath(), element);
String elementId = sequential.substring(sequential.lastIndexOf('/') + 1);
return elementId;
} catch (Exception e) {
throw ExceptionUtil.convertToRuntimeException(e);
}
}
public boolean offer(T element) throws Exception {
String nodeFullPath = root.concat("/").concat(Node_NAME);
try {
zkClient.createPersistentSequential(nodeFullPath, element);
} catch (ZkNoNodeException e) {
zkClient.createPersistent(root);
offer(element);
} catch (Exception e) {
throw ExceptionUtil.convertToRuntimeException(e);
}
return true;
}
@SuppressWarnings("unchecked")
protected Element<T> getFirstElement() throws InterruptedException {
final Object mutex = new Object();
IZkChildListener notifyListener =
new IZkChildListener() {
@Override
public void handleChildChange(String parentPath, List<String> currentChilds)
throws Exception {
synchronized (mutex) {
mutex.notify();
}
}
};
try {
while (true) {
List<String> elementNames;
synchronized (mutex) {
elementNames = _zkClient.subscribeChildChanges(_elementsPath, notifyListener);
while (elementNames == null || elementNames.isEmpty()) {
mutex.wait();
elementNames = _zkClient.getChildren(_elementsPath);
}
}
String elementName = getSmallestElement(elementNames);
try {
String elementPath = getElementPath(elementName);
return new Element<T>(elementName, (T) _zkClient.readData(elementPath));
} catch (ZkNoNodeException e) {
// somebody else picked up the element first, so we have to
// retry with the new first element
}
}
} catch (InterruptedException e) {
throw e;
} catch (Exception e) {
throw ExceptionUtil.convertToRuntimeException(e);
} finally {
_zkClient.unsubscribeChildChanges(_elementsPath, notifyListener);
}
}