private static void printQueueEventsListElementIds(ArrayList<QueueEvent> topN) {
if (LOG.isDebugEnabled() && !topN.isEmpty()) {
StringBuilder sb = new StringBuilder("[");
for (QueueEvent queueEvent : topN) {
sb.append(queueEvent.getId()).append(", ");
}
sb.append("]");
LOG.debug("Returning topN elements: {}", sb.toString());
}
}
/** Gets last element of the Queue without removing it. */
public String getTailId() throws KeeperException, InterruptedException {
// TODO: could we use getChildren here? Unsure what freshness guarantee the caller needs.
TreeSet<String> orderedChildren = fetchZkChildren(null);
for (String headNode : orderedChildren.descendingSet())
if (headNode != null) {
try {
QueueEvent queueEvent =
new QueueEvent(
dir + "/" + headNode,
zookeeper.getData(dir + "/" + headNode, null, null, true),
null);
return queueEvent.getId();
} catch (KeeperException.NoNodeException e) {
// Another client removed the node first, try next
}
}
return null;
}
/** Remove the event and save the response into the other path. */
public byte[] remove(QueueEvent event) throws KeeperException, InterruptedException {
TimerContext time = stats.time(dir + "_remove_event");
try {
String path = event.getId();
String responsePath = dir + "/" + response_prefix + path.substring(path.lastIndexOf("-") + 1);
if (zookeeper.exists(responsePath, true)) {
zookeeper.setData(responsePath, event.getBytes(), true);
} else {
LOG.info(
"Response ZK path: "
+ responsePath
+ " doesn't exist."
+ " Requestor may have disconnected from ZooKeeper");
}
byte[] data = zookeeper.getData(path, null, null, true);
zookeeper.delete(path, -1, true);
return data;
} finally {
time.stop();
}
}
