public boolean offer(T element) {
try {
_zkClient.createPersistentSequential(_root + "/" + ELEMENT_NAME + "-", element);
} catch (Exception e) {
throw ExceptionUtil.convertToRuntimeException(e);
}
return true;
}
public T poll() {
while (true) {
Element<T> element = getFirstElement();
if (element == null) {
return null;
}
try {
_zkClient.delete(element.getName());
return element.getData();
} catch (ZkNoNodeException e) {
// somebody else picked up the element first, so we have to
// retry with the new first element
} catch (Exception e) {
throw ExceptionUtil.convertToRuntimeException(e);
}
}
}
@SuppressWarnings("unchecked")
private Element<T> getFirstElement() {
try {
while (true) {
List<String> list = _zkClient.getChildren(_root);
if (list.size() == 0) {
return null;
}
String elementName = getSmallestElement(list);
try {
return new Element<T>(
_root + "/" + elementName, (T) _zkClient.readData(_root + "/" + elementName));
} catch (ZkNoNodeException e) {
// somebody else picked up the element first, so we have to
// retry with the new first element
}
}
} catch (Exception e) {
throw ExceptionUtil.convertToRuntimeException(e);
}
}
