/**
* 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.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ConnectException;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.nio.ByteBuffer;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentHashMap;
import org.apache.jute.BinaryInputArchive;
import org.apache.jute.BinaryOutputArchive;
import org.apache.jute.InputArchive;
import org.apache.jute.OutputArchive;
import org.apache.jute.Record;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.zookeeper.server.Request;
import org.apache.zookeeper.server.ServerCnxn;
import org.apache.zookeeper.server.ZooTrace;
import org.apache.zookeeper.server.quorum.QuorumPeer.QuorumServer;
import org.apache.zookeeper.server.util.SerializeUtils;
import org.apache.zookeeper.server.util.ZxidUtils;
import org.apache.zookeeper.txn.TxnHeader;
/**
* This class is the superclass of two of the three main actors in a ZK
* ensemble: Followers and Observers. Both Followers and Observers share
* a good deal of code which is moved into Peer to avoid duplication.
*/
public class Learner {
static class PacketInFlight {
TxnHeader hdr;
Record rec;
}
QuorumPeer self;
LearnerZooKeeperServer zk;
protected BufferedOutputStream bufferedOutput;
protected Socket sock;
/**
* Socket getter
* @return
*/
public Socket getSocket() {
return sock;
}
protected InputArchive leaderIs;
protected OutputArchive leaderOs;
/** the protocol version of the leader */
protected int leaderProtocolVersion = 0x01;
protected static final Logger LOG = LoggerFactory.getLogger(Learner.class);
static final private boolean nodelay = System.getProperty("follower.nodelay", "true").equals("true");
static {
LOG.info("TCP NoDelay set to: " + nodelay);
}
final ConcurrentHashMap<Long, ServerCnxn> pendingRevalidations =
new ConcurrentHashMap<Long, ServerCnxn>();
public int getPendingRevalidationsCount() {
return pendingRevalidations.size();
}
/**
* validate a session for a client
*
* @param clientId
* the client to be revalidated
* @param timeout
* the timeout for which the session is valid
* @return
* @throws IOException
*/
void validateSession(ServerCnxn cnxn, long clientId, int timeout)
throws IOException {
LOG.info("Revalidating client: 0x" + Long.toHexString(clientId));
ByteArrayOutputStream baos = new ByteArrayOutputStream();
DataOutputStream dos = new DataOutputStream(baos);
dos.writeLong(clientId);
dos.writeInt(timeout);
dos.close();
QuorumPacket qp = new QuorumPacket(Leader.REVALIDATE, -1, baos
.toByteArray(), null);
pendingRevalidations.put(clientId, cnxn);
if (LOG.isTraceEnabled()) {
ZooTrace.logTraceMessage(LOG,
ZooTrace.SESSION_TRACE_MASK,
"To validate session 0x"
+ Long.toHexString(clientId));
}
writePacket(qp, true);
}
/**
* write a packet to the leader
*
* @param pp
* the proposal packet to be sent to the leader
* @throws IOException
*/
void writePacket(QuorumPacket pp, boolean flush) throws IOException {
synchronized (leaderOs) {
if (pp != null) {
leaderOs.writeRecord(pp, "packet");
}
if (flush) {
bufferedOutput.flush();
}
}
}
/**
* read a packet from the leader
*
* @param pp
* the packet to be instantiated
* @throws IOException
*/
void readPacket(QuorumPacket pp) throws IOException {
synchronized (leaderIs) {
leaderIs.readRecord(pp, "packet");
}
long traceMask = ZooTrace.SERVER_PACKET_TRACE_MASK;
if (pp.getType() == Leader.PING) {
traceMask = ZooTrace.SERVER_PING_TRACE_MASK;
}
if (LOG.isTraceEnabled()) {
ZooTrace.logQuorumPacket(LOG, traceMask, 'i', pp);
}
}
/**
* send a request packet to the leader
*
* @param request
* the request from the client
* @throws IOException
*/
void request(Request request) throws IOException {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
DataOutputStream oa = new DataOutputStream(baos);
oa.writeLong(request.sessionId);
oa.writeInt(request.cxid);
oa.writeInt(request.type);
if (request.request != null) {
request.request.rewind();
int len = request.request.remaining();
byte b[] = new byte[len];
request.request.get(b);
request.request.rewind();
oa.write(b);
}
oa.close();
QuorumPacket qp = new QuorumPacket(Leader.REQUEST, -1, baos
.toByteArray(), request.authInfo);
writePacket(qp, true);
}
/**
* Returns the address of the node we think is the leader.
*/
protected InetSocketAddress findLeader() {
InetSocketAddress addr = null;
// Find the leader by id
Vote current = self.getCurrentVote();
for (QuorumServer s : self.getView().values()) {
if (s.id == current.getId()) {
addr = s.addr;
break;
}
}
if (addr == null) {
LOG.warn("Couldn't find the leader with id = "
+ current.getId());
}
return addr;
}
/**
* Establish a connection with the Leader found by findLeader. Retries
* 5 times before giving up.
* @param addr - the address of the Leader to connect to.
* @throws IOException - if the socket connection fails on the 5th attempt
* @throws ConnectException
* @throws InterruptedException
*/
protected void connectToLeader(InetSocketAddress addr)
throws IOException, ConnectException, InterruptedException {
sock = new Socket();
sock.setSoTimeout(self.tickTime * self.initLimit);
for (int tries = 0; tries < 5; tries++) {
try {
sock.connect(addr, self.tickTime * self.syncLimit);
sock.setTcpNoDelay(nodelay);
break;
} catch (IOException e) {
if (tries == 4) {
LOG.error("Unexpected exception",e);
throw e;
} else {
LOG.warn("Unexpected exception, tries="+tries+
", connecting to " + addr,e);
sock = new Socket();
sock.setSoTimeout(self.tickTime * self.initLimit);
}
}
Thread.sleep(1000);
}
leaderIs = BinaryInputArchive.getArchive(new BufferedInputStream(
sock.getInputStream()));
bufferedOutput = new BufferedOutputStream(sock.getOutputStream());
leaderOs = BinaryOutputArchive.getArchive(bufferedOutput);
}
/**
* Once connected to the leader, perform the handshake protocol to
* establish a following / observing connection.
* @param pktType
* @return the zxid the Leader sends for synchronization purposes.
* @throws IOException
*/
protected long registerWithLeader(int pktType) throws IOException{
/*
* Send follower info, including last zxid and sid
*/
long lastLoggedZxid = self.getLastLoggedZxid();
QuorumPacket qp = new QuorumPacket();
qp.setType(pktType);
qp.setZxid(ZxidUtils.makeZxid(self.getAcceptedEpoch(), 0));
/*
* Add sid to payload
*/
LearnerInfo li = new LearnerInfo(self.getId(), 0x10000);
ByteArrayOutputStream bsid = new ByteArrayOutputStream();
BinaryOutputArchive boa = BinaryOutputArchive.getArchive(bsid);
boa.writeRecord(li, "LearnerInfo");
qp.setData(bsid.toByteArray());
writePacket(qp, true);
readPacket(qp);
final long newEpoch = ZxidUtils.getEpochFromZxid(qp.getZxid());
if (qp.getType() == Leader.LEADERINFO) {
// we are connected to a 1.0 server so accept the new epoch and read the next packet
leaderProtocolVersion = ByteBuffer.wrap(qp.getData()).getInt();
byte epochBytes[] = new byte[4];
final ByteBuffer wrappedEpochBytes = ByteBuffer.wrap(epochBytes);
if (newEpoch > self.getAcceptedEpoch()) {
wrappedEpochBytes.putInt((int)self.getCurrentEpoch());
self.setAcceptedEpoch(newEpoch);
} else if (newEpoch == self.getAcceptedEpoch()) {
// since we have already acked an epoch equal to the leaders, we cannot ack
// again, but we still need to send our lastZxid to the leader so that we can
// sync with it if it does assume leadership of the epoch.
// the -1 indicates that this reply should not count as an ack for the new epoch
wrappedEpochBytes.putInt(-1);
} else {
throw new IOException("Leaders epoch, " + newEpoch + " is less than accepted epoch, " + self.getAcceptedEpoch());
}
QuorumPacket ackNewEpoch = new QuorumPacket(Leader.ACKEPOCH, lastLoggedZxid, epochBytes, null);
writePacket(ackNewEpoch, true);
return ZxidUtils.makeZxid(newEpoch, 0);
} else {
if (newEpoch > self.getAcceptedEpoch()) {
self.setAcceptedEpoch(newEpoch);
}
if (qp.getType() != Leader.NEWLEADER) {
LOG.error("First packet should have been NEWLEADER");
throw new IOException("First packet should have been NEWLEADER");
}
return qp.getZxid();
}
}
/**
* Finally, synchronize our history with the Leader.
* @param newLeaderZxid
* @throws IOException
* @throws InterruptedException
*/
protected void syncWithLeader(long newLeaderZxid) throws IOException, InterruptedException{
QuorumPacket ack = new QuorumPacket(Leader.ACK, 0, null, null);
QuorumPacket qp = new QuorumPacket();
long newEpoch = ZxidUtils.getEpochFromZxid(newLeaderZxid);
readPacket(qp);
LinkedList<Long> packetsCommitted = new LinkedList<Long>();
LinkedList<PacketInFlight> packetsNotCommitted = new LinkedList<PacketInFlight>();
synchronized (zk) {
if (qp.getType() == Leader.DIFF) {
LOG.info("Getting a diff from the leader 0x" + Long.toHexString(qp.getZxid()));
}
else if (qp.getType() == Leader.SNAP) {
LOG.info("Getting a snapshot from leader");
// The leader is going to dump the database
// clear our own database and read
zk.getZKDatabase().clear();
zk.getZKDatabase().deserializeSnapshot(leaderIs);
String signature = leaderIs.readString("signature");
if (!signature.equals("BenWasHere")) {
LOG.error("Missing signature. Got " + signature);
throw new IOException("Missing signature");
}
} else if (qp.getType() == Leader.TRUNC) {
//we need to truncate the log to the lastzxid of the leader
LOG.warn("Truncating log to get in sync with the leader 0x"
+ Long.toHexString(qp.getZxid()));
boolean truncated=zk.getZKDatabase().truncateLog(qp.getZxid());
if (!truncated) {
// not able to truncate the log
LOG.error("Not able to truncate the log "
+ Long.toHexString(qp.getZxid()));
System.exit(13);
}
}
else {
LOG.error("Got unexpected packet from leader "
+ qp.getType() + " exiting ... " );
System.exit(13);
}
zk.getZKDatabase().setlastProcessedZxid(qp.getZxid());
long lastQueued = 0;
// in V1.0 we take a snapshot when we get the NEWLEADER message, but in pre V1.0
// we take the snapshot at the UPDATE, since V1.0 also gets the UPDATE (after the NEWLEADER)
// we need to make sure that we don't take the snapshot twice.
boolean snapshotTaken = false;
// we are now going to start getting transactions to apply followed by an UPTODATE
outerLoop:
while (self.isRunning()) {
readPacket(qp);
switch(qp.getType()) {
case Leader.PROPOSAL:
PacketInFlight pif = new PacketInFlight();
pif.hdr = new TxnHeader();
pif.rec = SerializeUtils.deserializeTxn(qp.getData(), pif.hdr);
if (pif.hdr.getZxid() != lastQueued + 1) {
LOG.warn("Got zxid 0x"
+ Long.toHexString(pif.hdr.getZxid())
+ " expected 0x"
+ Long.toHexString(lastQueued + 1));
}
lastQueued = pif.hdr.getZxid();
packetsNotCommitted.add(pif);
break;
case Leader.COMMIT:
if (!snapshotTaken) {
pif = packetsNotCommitted.peekFirst();
if (pif.hdr.getZxid() != qp.getZxid()) {
LOG.warn("Committing " + qp.getZxid() + ", but next proposal is " + pif.hdr.getZxid());
} else {
zk.getZKDatabase().processTxn(pif.hdr, pif.rec);
packetsNotCommitted.remove();
}
} else {
packetsCommitted.add(qp.getZxid());
}
break;
case Leader.INFORM:
TxnHeader hdr = new TxnHeader();
Record txn = SerializeUtils.deserializeTxn(qp.getData(), hdr);
zk.getZKDatabase().processTxn(hdr, txn);
break;
case Leader.UPTODATE:
if (!snapshotTaken) { // true for the pre v1.0 case
zk.takeSnapshot();
self.setCurrentEpoch(newEpoch);
}
self.cnxnFactory.setZooKeeperServer(zk);
break outerLoop;
case Leader.NEWLEADER: // it will be NEWLEADER in v1.0
zk.takeSnapshot();
self.setCurrentEpoch(newEpoch);
snapshotTaken = true;
writePacket(new QuorumPacket(Leader.ACK, newLeaderZxid, null, null), true);
break;
}
}
}
ack.setZxid(ZxidUtils.makeZxid(newEpoch, 0));
writePacket(ack, true);
sock.setSoTimeout(self.tickTime * self.syncLimit);
zk.startup();
// We need to log the stuff that came in between the snapshot and the uptodate
if (zk instanceof FollowerZooKeeperServer) {
FollowerZooKeeperServer fzk = (FollowerZooKeeperServer)zk;
for(PacketInFlight p: packetsNotCommitted) {
fzk.logRequest(p.hdr, p.rec);
}
for(Long zxid: packetsCommitted) {
fzk.commit(zxid);
}
}
}
protected void revalidate(QuorumPacket qp) throws IOException {
ByteArrayInputStream bis = new ByteArrayInputStream(qp
.getData());
DataInputStream dis = new DataInputStream(bis);
long sessionId = dis.readLong();
boolean valid = dis.readBoolean();
ServerCnxn cnxn = pendingRevalidations
.remove(sessionId);
if (cnxn == null) {
LOG.warn("Missing session 0x"
+ Long.toHexString(sessionId)
+ " for validation");
} else {
zk.finishSessionInit(cnxn, valid);
}
if (LOG.isTraceEnabled()) {
ZooTrace.logTraceMessage(LOG,
ZooTrace.SESSION_TRACE_MASK,
"Session 0x" + Long.toHexString(sessionId)
+ " is valid: " + valid);
}
}
protected void ping(QuorumPacket qp) throws IOException {
// Send back the ping with our session data
ByteArrayOutputStream bos = new ByteArrayOutputStream();
DataOutputStream dos = new DataOutputStream(bos);
HashMap<Long, Integer> touchTable = zk
.getTouchSnapshot();
for (Entry<Long, Integer> entry : touchTable.entrySet()) {
dos.writeLong(entry.getKey());
dos.writeInt(entry.getValue());
}
qp.setData(bos.toByteArray());
writePacket(qp, true);
}
/**
* Shutdown the Peer
*/
public void shutdown() {
// set the zookeeper server to null
self.cnxnFactory.setZooKeeperServer(null);
// clear all the connections
self.cnxnFactory.closeAll();
// shutdown previous zookeeper
if (zk != null) {
zk.shutdown();
}
}
}