/**
* Unlike a Follower, which sees a full request only during the PROPOSAL phase, Observers get all
* the data required with the INFORM packet. This method commits a request that has been unpacked
* by from an INFORM received from the Leader.
*
* @param request
*/
public void commitRequest(Request request) {
if (syncRequestProcessorEnabled) {
// Write to txnlog and take periodic snapshot
syncProcessor.processRequest(request);
}
commitProcessor.commit(request);
}
/**
* Set up the request processors for an Observer: firstProcesor->commitProcessor->finalProcessor
*/
@Override
protected void setupRequestProcessors() {
// We might consider changing the processor behaviour of
// Observers to, for example, remove the disk sync requirements.
// Currently, they behave almost exactly the same as followers.
RequestProcessor finalProcessor = new FinalRequestProcessor(this);
commitProcessor =
new CommitProcessor(
finalProcessor, Long.toString(getServerId()), true, getZooKeeperServerListener());
commitProcessor.start();
firstProcessor = new ObserverRequestProcessor(this, commitProcessor);
((ObserverRequestProcessor) firstProcessor).start();
/*
* Observer should write to disk, so that the it won't request
* too old txn from the leader which may lead to getting an entire
* snapshot.
*
* However, this may degrade performance as it has to write to disk
* and do periodic snapshot which may double the memory requirements
*/
if (syncRequestProcessorEnabled) {
syncProcessor = new SyncRequestProcessor(this, null);
syncProcessor.start();
}
}
/*
* Process a sync request
*/
public synchronized void sync() {
if (pendingSyncs.size() == 0) {
LOG.warn("Not expecting a sync.");
return;
}
Request r = pendingSyncs.remove();
commitProcessor.commit(r);
}
