这里详细看下工厂模式创建的zkServer,后面在介绍分析那三种选举算法
public class QuorumPeer extends ZooKeeperThread implements QuorumStats.Provider{}中
ServerCnxnFactory cnxnFactory; cnxnFactory来自构造方法传进来的：
cnxnFactory来自：
try {
ServerCnxnFactory cnxnFactory = ServerCnxnFactory.createFactory();
cnxnFactory.configure(config.getClientPortAddress(),
config.getMaxClientCnxns());
quorumPeer = new QuorumPeer(config.getServers(),
new File(config.getDataDir()),
new File(config.getDataLogDir()),
config.getElectionAlg(),
config.getServerId(),
config.getTickTime(),
config.getInitLimit(),
config.getSyncLimit(),
config.getQuorumListenOnAllIPs(),
cnxnFactory,
config.getQuorumVerifier());
quorumPeer.setClientPortAddress(config.getClientPortAddress());
quorumPeer.setMinSessionTimeout(config.getMinSessionTimeout());
quorumPeer.setMaxSessionTimeout(config.getMaxSessionTimeout());
quorumPeer.setZKDatabase(new ZKDatabase(quorumPeer.getTxnFactory()));
quorumPeer.setLearnerType(config.getPeerType());
quorumPeer.setSyncEnabled(config.getSyncEnabled());
// sets quorum sasl authentication configurations
quorumPeer.setQuorumSaslEnabled(config.quorumEnableSasl);
if(quorumPeer.isQuorumSaslAuthEnabled()){
quorumPeer.setQuorumServerSaslRequired(config.quorumServerRequireSasl);
quorumPeer.setQuorumLearnerSaslRequired(config.quorumLearnerRequireSasl);
quorumPeer.setQuorumServicePrincipal(config.quorumServicePrincipal);
quorumPeer.setQuorumServerLoginContext(config.quorumServerLoginContext);
quorumPeer.setQuorumLearnerLoginContext(config.quorumLearnerLoginContext);
}
quorumPeer.setQuorumCnxnThreadsSize(config.quorumCnxnThreadsSize);
quorumPeer.initialize();
quorumPeer.start();
quorumPeer.join();
}ServerCnxnFactory cnxnFactory = ServerCnxnFactory.createFactory(); 看下代码：
static public ServerCnxnFactory createFactory() throws IOException {
String serverCnxnFactoryName =
System.getProperty(ZOOKEEPER_SERVER_CNXN_FACTORY);
if (serverCnxnFactoryName == null) {
serverCnxnFactoryName = NIOServerCnxnFactory.class.getName();
}
try {
return (ServerCnxnFactory) Class.forName(serverCnxnFactoryName)
.newInstance();
} catch (Exception e) {
IOException ioe = new IOException("Couldn't instantiate "
+ serverCnxnFactoryName);
ioe.initCause(e);
throw ioe;
}
}来自类ServerCnxnFactory：
/**
* 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;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.util.HashSet;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import javax.security.auth.login.Configuration;
import javax.security.auth.login.LoginException;
import javax.security.auth.login.AppConfigurationEntry;
import javax.management.JMException;
import org.apache.zookeeper.Login;
import org.apache.zookeeper.Environment;
import org.apache.zookeeper.jmx.MBeanRegistry;
import org.apache.zookeeper.server.auth.SaslServerCallbackHandler;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public abstract class ServerCnxnFactory {
public static final String ZOOKEEPER_SERVER_CNXN_FACTORY = "zookeeper.serverCnxnFactory";
public interface PacketProcessor {
public void processPacket(ByteBuffer packet, ServerCnxn src);
}
Logger LOG = LoggerFactory.getLogger(ServerCnxnFactory.class);
/**
* The buffer will cause the connection to be close when we do a send.
*/
static final ByteBuffer closeConn = ByteBuffer.allocate(0);
public abstract int getLocalPort();
public abstract Iterable<ServerCnxn> getConnections();
public int getNumAliveConnections() {
synchronized(cnxns) {
return cnxns.size();
}
}
ZooKeeperServer getZooKeeperServer() {
return zkServer;
}
public abstract void closeSession(long sessionId);
public abstract void configure(InetSocketAddress addr,
int maxClientCnxns) throws IOException;
protected SaslServerCallbackHandler saslServerCallbackHandler;
public Login login;
/** Maximum number of connections allowed from particular host (ip) */
public abstract int getMaxClientCnxnsPerHost();
/** Maximum number of connections allowed from particular host (ip) */
public abstract void setMaxClientCnxnsPerHost(int max);
public abstract void startup(ZooKeeperServer zkServer)
throws IOException, InterruptedException;
public abstract void join() throws InterruptedException;
public abstract void shutdown();
public abstract void start();
protected ZooKeeperServer zkServer;
final public void setZooKeeperServer(ZooKeeperServer zk) {
this.zkServer = zk;
if (zk != null) {
zk.setServerCnxnFactory(this);
}
}
public abstract void closeAll();
static public ServerCnxnFactory createFactory() throws IOException {
String serverCnxnFactoryName =
System.getProperty(ZOOKEEPER_SERVER_CNXN_FACTORY);
if (serverCnxnFactoryName == null) {
serverCnxnFactoryName = NIOServerCnxnFactory.class.getName();
}
try {
return (ServerCnxnFactory) Class.forName(serverCnxnFactoryName)
.newInstance();
} catch (Exception e) {
IOException ioe = new IOException("Couldn't instantiate "
+ serverCnxnFactoryName);
ioe.initCause(e);
throw ioe;
}
}
static public ServerCnxnFactory createFactory(int clientPort,
int maxClientCnxns) throws IOException
{
return createFactory(new InetSocketAddress(clientPort), maxClientCnxns);
}
static public ServerCnxnFactory createFactory(InetSocketAddress addr,
int maxClientCnxns) throws IOException
{
ServerCnxnFactory factory = createFactory();
factory.configure(addr, maxClientCnxns);
return factory;
}
public abstract InetSocketAddress getLocalAddress();
private final Map<ServerCnxn, ConnectionBean> connectionBeans
= new ConcurrentHashMap<ServerCnxn, ConnectionBean>();
protected final HashSet<ServerCnxn> cnxns = new HashSet<ServerCnxn>();
public void unregisterConnection(ServerCnxn serverCnxn) {
ConnectionBean jmxConnectionBean = connectionBeans.remove(serverCnxn);
if (jmxConnectionBean != null){
MBeanRegistry.getInstance().unregister(jmxConnectionBean);
}
}
public void registerConnection(ServerCnxn serverCnxn) {
if (zkServer != null) {
ConnectionBean jmxConnectionBean = new ConnectionBean(serverCnxn, zkServer);
try {
MBeanRegistry.getInstance().register(jmxConnectionBean, zkServer.jmxServerBean);
connectionBeans.put(serverCnxn, jmxConnectionBean);
} catch (JMException e) {
LOG.warn("Could not register connection", e);
}
}
}
/**
* Initialize the server SASL if specified.
*
* If the user has specified a "ZooKeeperServer.LOGIN_CONTEXT_NAME_KEY"
* or a jaas.conf using "java.security.auth.login.config"
* the authentication is required and an exception is raised.
* Otherwise no authentication is configured and no exception is raised.
*
* @throws IOException if jaas.conf is missing or there's an error in it.
*/
protected void configureSaslLogin() throws IOException {
String serverSection = System.getProperty(ZooKeeperSaslServer.LOGIN_CONTEXT_NAME_KEY,
ZooKeeperSaslServer.DEFAULT_LOGIN_CONTEXT_NAME);
// Note that 'Configuration' here refers to javax.security.auth.login.Configuration.
AppConfigurationEntry entries[] = null;
SecurityException securityException = null;
try {
entries = Configuration.getConfiguration().getAppConfigurationEntry(serverSection);
} catch (SecurityException e) {
// handle below: might be harmless if the user doesn't intend to use JAAS authentication.
securityException = e;
}
// No entries in jaas.conf
// If there's a configuration exception fetching the jaas section and
// the user has required sasl by specifying a LOGIN_CONTEXT_NAME_KEY or a jaas file
// we throw an exception otherwise we continue without authentication.
if (entries == null) {
String jaasFile = System.getProperty(Environment.JAAS_CONF_KEY);
String loginContextName = System.getProperty(ZooKeeperSaslServer.LOGIN_CONTEXT_NAME_KEY);
if (securityException != null && (loginContextName != null || jaasFile != null)) {
String errorMessage = "No JAAS configuration section named '" + serverSection + "' was found";
if (jaasFile != null) {
errorMessage += "in '" + jaasFile + "'.";
}
if (loginContextName != null) {
errorMessage += " But " + ZooKeeperSaslServer.LOGIN_CONTEXT_NAME_KEY + " was set.";
}
LOG.error(errorMessage);
throw new IOException(errorMessage);
}
return;
}
// jaas.conf entry available
try {
saslServerCallbackHandler = new SaslServerCallbackHandler(Configuration.getConfiguration());
login = new Login(serverSection, saslServerCallbackHandler);
login.startThreadIfNeeded();
} catch (LoginException e) {
throw new IOException("Could not configure server because SASL configuration did not allow the "
+ " ZooKeeper server to authenticate itself properly: " + e);
}
}
}
接着执行代码：
cnxnFactory.configure(config.getClientPortAddress(), config.getMaxClientCnxns());
clientPortAddress
与clientPort匹配，表示某个IP地址，如果服务器有多个网络接口(多个IP地址),如果没有设置这个属性，则clientPort会绑定到所有IP地址上，否则只绑定到该设置的IP地址上。
从这里可以看到cnxnFactory貌似创建client 服务的工厂，回头再看这个代码：
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static public ServerCnxnFactory createFactory() throws IOException {
String serverCnxnFactoryName =
System.getProperty(ZOOKEEPER_SERVER_CNXN_FACTORY);
if (serverCnxnFactoryName == null) {
serverCnxnFactoryName = NIOServerCnxnFactory.class.getName();
}
try {
return (ServerCnxnFactory) Class.forName(serverCnxnFactoryName)
.newInstance();
} catch (Exception e) {
IOException ioe = new IOException("Couldn't instantiate "
+ serverCnxnFactoryName);
ioe.initCause(e);
throw ioe;
}
}public static final String ZOOKEEPER_SERVER_CNXN_FACTORY = "zookeeper.serverCnxnFactory";