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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.zookeeper.server.quorum;
import java.io.IOException;
import java.util.concurrent.LinkedBlockingQueue;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.ZooDefs.OpCode;
import org.apache.zookeeper.server.Request;
import org.apache.zookeeper.server.RequestProcessor;
import org.apache.zookeeper.server.ServerMetrics;
import org.apache.zookeeper.server.ZooKeeperCriticalThread;
import org.apache.zookeeper.server.ZooTrace;
import org.apache.zookeeper.txn.ErrorTxn;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* This RequestProcessor forwards any requests that modify the state of the
* system to the Leader.
*/
public class FollowerRequestProcessor extends ZooKeeperCriticalThread implements RequestProcessor {
private static final Logger LOG = LoggerFactory.getLogger(FollowerRequestProcessor.class);
public static final String SKIP_LEARNER_REQUEST_TO_NEXT_PROCESSOR = "zookeeper.follower.skipLearnerRequestToNextProcessor";
private final boolean skipLearnerRequestToNextProcessor;
FollowerZooKeeperServer zks;
RequestProcessor nextProcessor;
LinkedBlockingQueue<Request> queuedRequests = new LinkedBlockingQueue<Request>();
boolean finished = false;
public FollowerRequestProcessor(FollowerZooKeeperServer zks, RequestProcessor nextProcessor) {
super("FollowerRequestProcessor:" + zks.getServerId(), zks.getZooKeeperServerListener());
this.zks = zks;
this.nextProcessor = nextProcessor;
this.skipLearnerRequestToNextProcessor = Boolean.getBoolean(SKIP_LEARNER_REQUEST_TO_NEXT_PROCESSOR);
LOG.info("Initialized FollowerRequestProcessor with {} as {}", SKIP_LEARNER_REQUEST_TO_NEXT_PROCESSOR,
skipLearnerRequestToNextProcessor);
}
@Override
public void run() {
try {
while (!finished) {
ServerMetrics.getMetrics().LEARNER_REQUEST_PROCESSOR_QUEUE_SIZE.add(queuedRequests.size());
Request request = queuedRequests.take();
if (LOG.isTraceEnabled()) {
ZooTrace.logRequest(LOG, ZooTrace.CLIENT_REQUEST_TRACE_MASK, 'F', request, "");
}
if (request == Request.requestOfDeath) {
break;
}
// Screen quorum requests against ACLs first
if (!zks.authWriteRequest(request)) {
continue;
}
// We want to queue the request to be processed before we submit
// the request to the leader so that we are ready to receive
// the response
maybeSendRequestToNextProcessor(request);
if (request.isThrottled()) {
continue;
}
// We now ship the request to the leader. As with all
// other quorum operations, sync also follows this code
// path, but different from others, we need to keep track
// of the sync operations this follower has pending, so we
// add it to pendingSyncs.
switch (request.type) {
case OpCode.sync:
zks.pendingSyncs.add(request);
zks.getFollower().request(request);
break;
case OpCode.create:
case OpCode.create2:
case OpCode.createTTL:
case OpCode.createContainer:
case OpCode.delete:
case OpCode.deleteContainer:
case OpCode.setData:
case OpCode.reconfig:
case OpCode.setACL:
case OpCode.multi:
case OpCode.check:
zks.getFollower().request(request);
break;
case OpCode.createSession:
case OpCode.closeSession:
// Don't forward local sessions to the leader.
if (!request.isLocalSession()) {
zks.getFollower().request(request);
}
break;
}
}
} catch (RuntimeException e) { // spotbugs require explicit catch of RuntimeException
handleException(this.getName(), e);
} catch (Exception e) {
handleException(this.getName(), e);
}
LOG.info("FollowerRequestProcessor exited loop!");
}
private void maybeSendRequestToNextProcessor(Request request) throws RequestProcessorException {
if (skipLearnerRequestToNextProcessor && request.isFromLearner()) {
ServerMetrics.getMetrics().SKIP_LEARNER_REQUEST_TO_NEXT_PROCESSOR_COUNT.add(1);
} else {
nextProcessor.processRequest(request);
}
}
public void processRequest(Request request) {
processRequest(request, true);
}
void processRequest(Request request, boolean checkForUpgrade) {
if (!finished) {
if (checkForUpgrade) {
// Before sending the request, check if the request requires a
// global session and what we have is a local session. If so do
// an upgrade.
Request upgradeRequest = null;
try {
upgradeRequest = zks.checkUpgradeSession(request);
} catch (KeeperException ke) {
if (request.getHdr() != null) {
request.getHdr().setType(OpCode.error);
request.setTxn(new ErrorTxn(ke.code().intValue()));
}
request.setException(ke);
LOG.warn("Error creating upgrade request", ke);
} catch (IOException ie) {
LOG.error("Unexpected error in upgrade", ie);
}
if (upgradeRequest != null) {
queuedRequests.add(upgradeRequest);
}
}
queuedRequests.add(request);
}
}
public void shutdown() {
LOG.info("Shutting down");
finished = true;
queuedRequests.clear();
queuedRequests.add(Request.requestOfDeath);
nextProcessor.shutdown();
}
}
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