前言

ServerCnxnFactory负责与客户端的连接。

初始化

org.apache.zookeeper.server.quorum.QuorumPeerMain#runFromConfig

启动

org.apache.zookeeper.server.quorum.QuorumPeer#start

ServerCnxnFactory类

继承关系

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public abstract class ServerCnxnFactory {}

属性

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// sessionMap is used to speed up closeSession()
protected final ConcurrentMap<Long, ServerCnxn> sessionMap =
        new ConcurrentHashMap<Long, ServerCnxn>();

/**
    * The buffer will cause the connection to be close when we do a send.
    */
static final ByteBuffer closeConn = ByteBuffer.allocate(0);

protected SaslServerCallbackHandler saslServerCallbackHandler;
public Login login;
protected ZooKeeperServer zkServer;
private final Map<ServerCnxn, ConnectionBean> connectionBeans
        = new ConcurrentHashMap<ServerCnxn, ConnectionBean>();

protected final HashSet<ServerCnxn> cnxns = new HashSet<ServerCnxn>();

抽象方法

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public abstract int getLocalPort();
    
public abstract Iterable<ServerCnxn> getConnections();

public abstract void closeSession(long sessionId);

public abstract void configure(InetSocketAddress addr,
                                int maxClientCnxns) throws IOException;

/** 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();

public abstract void closeAll();

public abstract InetSocketAddress getLocalAddress();

createFactory()构造方法

可以通过环境变量设置使用哪个实现类

环境变量：

ZOOKEEPER_SERVER_CNXN_FACTORY = “zookeeper.serverCnxnFactory”;

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static public ServerCnxnFactory createFactory() throws IOException {
    String serverCnxnFactoryName =
        System.getProperty(ZOOKEEPER_SERVER_CNXN_FACTORY);
    if (serverCnxnFactoryName == null) {  // 没有设置环境变量就使用NIO
        serverCnxnFactoryName = NIOServerCnxnFactory.class.getName();
    }
    try {
        // 反射生成对象
        ServerCnxnFactory serverCnxnFactory = (ServerCnxnFactory) Class.forName(serverCnxnFactoryName)
                .getDeclaredConstructor().newInstance();
        LOG.info("Using {} as server connection factory", serverCnxnFactoryName);
        return serverCnxnFactory;
    } catch (Exception e) {
        IOException ioe = new IOException("Couldn't instantiate "
                + serverCnxnFactoryName);
        ioe.initCause(e);
        throw ioe;
    }
}

实现类

目前3.4.10版本实现类有

org.apache.zookeeper.server.NIOServerCnxnFactory
org.apache.zookeeper.server.NettyServerCnxnFactory