【Zookeeper】源码分析之网络通信（一）
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一、前言
前面已经分析了请求处理链中的多数类，接着继续分析Zookeeper中的网络通信模块。
二、总体框图
对于网络通信模块，其总体框图如下所示
说明：
Stats，表示ServerCnxn上的统计数据。
Watcher，表示时间处理器。
ServerCnxn，表示服务器连接，表示一个从客户端到服务器的连接。
NettyServerCnxn，基于Netty的连接的具体实现。
NIOServerCnxn，基于NIO的连接的具体实现。
三、ServerCnxn源码分析
3.1 类的继承关系
public abstract class ServerCnxn implements Stats, Watcher {}
说明：ServerCnxn为抽象类，其继承Stats和Watcher两个接口，表示客户端到服务端的连接。
3.2 类的内部类
// 请求关闭异常类 protected static class CloseRequestException extends IOException { private static final long serialVersionUID = -7854505709816442681L; public CloseRequestException(String msg) { super(msg); } } // 流结束异常类 protected static class EndOfStreamException extends IOException { private static final long serialVersionUID = -8255690282104294178L; public EndOfStreamException(String msg) { super(msg); } public String toString() { return "EndOfStreamException: " + getMessage(); } }
说明：ServerCnxn包含了两个异常类，用于表示在连接中发生的异常情况。
3.3 类的属性
public abstract class ServerCnxn implements Stats, Watcher { // This is just an arbitrary object to represent requests issued by // (aka owned by) this class // 代表由本类提出的请求 final public static Object me = new Object(); // 认证信息 protected ArrayList<Id> authInfo = new ArrayList<Id>(); /** * If the client is of old version, we don't send r-o mode info to it. * The reason is that if we would, old C client doesn't read it, which * results in TCP RST packet, i.e. "connection reset by peer". */ // 是否为旧的C客户端 boolean isOldClient = true; // Zookeeper的Sasl服务器 protected ZooKeeperSaslServer zooKeeperSaslServer = null; /** * CMD命令 **/ /* * See <a href="{@docRoot}/../../../docs/zookeeperAdmin.html#sc_zkCommands"> * Zk Admin</a>. this link is for all the commands. */ // CMD命令 protected final static int confCmd = ByteBuffer.wrap("conf".getBytes()).getInt(); /* * See <a href="{@docRoot}/../../../docs/zookeeperAdmin.html#sc_zkCommands"> * Zk Admin</a>. this link is for all the commands. */ protected final static int consCmd = ByteBuffer.wrap("cons".getBytes()).getInt(); /* * See <a href="{@docRoot}/../../../docs/zookeeperAdmin.html#sc_zkCommands"> * Zk Admin</a>. this link is for all the commands. */ protected final static int crstCmd = ByteBuffer.wrap("crst".getBytes()).getInt(); /* * See <a href="{@docRoot}/../../../docs/zookeeperAdmin.html#sc_zkCommands"> * Zk Admin</a>. this link is for all the commands. */ protected final static int dumpCmd = ByteBuffer.wrap("dump".getBytes()).getInt(); /* * See <a href="{@docRoot}/../../../docs/zookeeperAdmin.html#sc_zkCommands"> * Zk Admin</a>. this link is for all the commands. */ protected final static int enviCmd = ByteBuffer.wrap("envi".getBytes()).getInt(); /* * See <a href="{@docRoot}/../../../docs/zookeeperAdmin.html#sc_zkCommands"> * Zk Admin</a>. this link is for all the commands. */ protected final static int getTraceMaskCmd = ByteBuffer.wrap("gtmk".getBytes()).getInt(); /* * See <a href="{@docRoot}/../../../docs/zookeeperAdmin.html#sc_zkCommands"> * Zk Admin</a>. this link is for all the commands. */ protected final static int ruokCmd = ByteBuffer.wrap("ruok".getBytes()).getInt(); /* * See <a href="{@docRoot}/../../../docs/zookeeperAdmin.html#sc_zkCommands"> * Zk Admin</a>. this link is for all the commands. */ protected final static int setTraceMaskCmd = ByteBuffer.wrap("stmk".getBytes()).getInt(); /* * See <a href="{@docRoot}/../../../docs/zookeeperAdmin.html#sc_zkCommands"> * Zk Admin</a>. this link is for all the commands. */ protected final static int srvrCmd = ByteBuffer.wrap("srvr".getBytes()).getInt(); /* * See <a href="{@docRoot}/../../../docs/zookeeperAdmin.html#sc_zkCommands"> * Zk Admin</a>. this link is for all the commands. */ protected final static int srstCmd = ByteBuffer.wrap("srst".getBytes()).getInt(); /* * See <a href="{@docRoot}/../../../docs/zookeeperAdmin.html#sc_zkCommands"> * Zk Admin</a>. this link is for all the commands. */ protected final static int statCmd = ByteBuffer.wrap("stat".getBytes()).getInt(); /* * See <a href="{@docRoot}/../../../docs/zookeeperAdmin.html#sc_zkCommands"> * Zk Admin</a>. this link is for all the commands. */ protected final static int wchcCmd = ByteBuffer.wrap("wchc".getBytes()).getInt(); /* * See <a href="{@docRoot}/../../../docs/zookeeperAdmin.html#sc_zkCommands"> * Zk Admin</a>. this link is for all the commands. */ protected final static int wchpCmd = ByteBuffer.wrap("wchp".getBytes()).getInt(); /* * See <a href="{@docRoot}/../../../docs/zookeeperAdmin.html#sc_zkCommands"> * Zk Admin</a>. this link is for all the commands. */ protected final static int wchsCmd = ByteBuffer.wrap("wchs".getBytes()).getInt(); /* * See <a href="{@docRoot}/../../../docs/zookeeperAdmin.html#sc_zkCommands"> * Zk Admin</a>. this link is for all the commands. */ protected final static int mntrCmd = ByteBuffer.wrap("mntr".getBytes()) .getInt(); /* * See <a href="{@docRoot}/../../../docs/zookeeperAdmin.html#sc_zkCommands"> * Zk Admin</a>. this link is for all the commands. */ protected final static int isroCmd = ByteBuffer.wrap("isro".getBytes()) .getInt(); // 存储CMD的整形值与String的键值对 protected final static HashMap<Integer, String> cmd2String = new HashMap<Integer, String>(); // specify all of the commands that are available static { cmd2String.put(confCmd, "conf"); cmd2String.put(consCmd, "cons"); cmd2String.put(crstCmd, "crst"); cmd2String.put(dumpCmd, "dump"); cmd2String.put(enviCmd, "envi"); cmd2String.put(getTraceMaskCmd, "gtmk"); cmd2String.put(ruokCmd, "ruok"); cmd2String.put(setTraceMaskCmd, "stmk"); cmd2String.put(srstCmd, "srst"); cmd2String.put(srvrCmd, "srvr"); cmd2String.put(statCmd, "stat"); cmd2String.put(wchcCmd, "wchc"); cmd2String.put(wchpCmd, "wchp"); cmd2String.put(wchsCmd, "wchs"); cmd2String.put(mntrCmd, "mntr"); cmd2String.put(isroCmd, "isro"); } /** * 服务器的统计数据 **/ // 创建连接的时间 protected final Date established = new Date(); // 接受的packet数量 protected final AtomicLong packetsReceived = new AtomicLong(); // 发送的packet数量 protected final AtomicLong packetsSent = new AtomicLong(); // 最小延迟 protected long minLatency; // 最大延迟 protected long maxLatency; // 最后操作类型 protected String lastOp; // 最后的cxid protected long lastCxid; // 最后的zxid protected long lastZxid; // 最后的响应时间 protected long lastResponseTime; // 最后的延迟 protected long lastLatency; // 数量 protected long count; // 总的延迟 protected long totalLatency;}
说明：可以看到，ServerCnxn类维护了很多属性，主要是服务器的统计信息和和命令行信息。
3.4 核心函数分析
1. 抽象方法
// 获取会话超时时间 abstract int getSessionTimeout(); // 关闭 abstract void close(); // 发送响应 public abstract void sendResponse(ReplyHeader h, Record r, String tag) throws IOException; /* notify the client the session is closing and close/cleanup socket */ // 关闭会话 abstract void sendCloseSession(); // 处理，Watcher接口中的方法 public abstract void process(WatchedEvent event); // 获取会话id abstract long getSessionId(); // 设置会话id abstract void setSessionId(long sessionId); // 设置缓冲 abstract void sendBuffer(ByteBuffer closeConn); // 允许接收 abstract void enableRecv(); // 不允许接收 abstract void disableRecv(); // 设置会话超时时间 abstract void setSessionTimeout(int sessionTimeout); // 获取服务器的统计数据 protected abstract ServerStats serverStats();
说明：以上的方法均为抽象方法，需要具体子类实现，如process方法是Watcher接口中的方法，在ServerCnxn中并未实现，需要具体子类实现。
2. 具体方法
/** auth info for the cnxn, returns an unmodifyable list */ // 获取认证信息，返回不可修改的列表 public List<Id> getAuthInfo() { return Collections.unmodifiableList(authInfo); } // 添加认证信息 public void addAuthInfo(Id id) { if (authInfo.contains(id) == false) { authInfo.add(id); } } // 移除认证信息 public boolean removeAuthInfo(Id id) { return authInfo.remove(id); } // 接收的packet protected void packetReceived() { incrPacketsReceived(); ServerStats serverStats = serverStats(); if (serverStats != null) { serverStats().incrementPacketsReceived(); } } // 发送的packet protected void packetSent() { incrPacketsSent(); ServerStats serverStats = serverStats(); if (serverStats != null) { serverStats().incrementPacketsSent(); } } // 重置统计数据 public synchronized void resetStats() { packetsReceived.set(0); packetsSent.set(0); minLatency = Long.MAX_VALUE; maxLatency = 0; lastOp = "NA"; lastCxid = -1; lastZxid = -1; lastResponseTime = 0; lastLatency = 0; count = 0; totalLatency = 0; } // 增加接收的packet数量 protected long incrPacketsReceived() { return packetsReceived.incrementAndGet(); } // 增加outstandingRequest数量 protected void incrOutstandingRequests(RequestHeader h) { } // 增加发送的packet数量 protected long incrPacketsSent() { return packetsSent.incrementAndGet(); } // 更新响应的统计数据 protected synchronized void updateStatsForResponse(long cxid, long zxid, String op, long start, long end) { // don't overwrite with "special" xids - we're interested // in the clients last real operation if (cxid >= 0) { lastCxid = cxid; } lastZxid = zxid; lastOp = op; lastResponseTime = end; long elapsed = end - start; lastLatency = elapsed; if (elapsed < minLatency) { minLatency = elapsed; } if (elapsed > maxLatency) { maxLatency = elapsed; } count++; totalLatency += elapsed; } public Date getEstablished() { return (Date)established.clone(); } public abstract long getOutstandingRequests(); public long getPacketsReceived() { return packetsReceived.longValue(); } public long getPacketsSent() { return packetsSent.longValue(); } public synchronized long getMinLatency() { return minLatency == Long.MAX_VALUE ? 0 : minLatency; } public synchronized long getAvgLatency() { return count == 0 ? 0 : totalLatency / count; } public synchronized long getMaxLatency() { return maxLatency; } public synchronized String getLastOperation() { return lastOp; } public synchronized long getLastCxid() { return lastCxid; } public synchronized long getLastZxid() { return lastZxid; } public synchronized long getLastResponseTime() { return lastResponseTime; } public synchronized long getLastLatency() { return lastLatency; } /** * Prints detailed stats information for the connection. * * @see dumpConnectionInfo(PrintWriter, boolean) for brief stats */ @Override public String toString() { StringWriter sw = new StringWriter(); PrintWriter pwriter = new PrintWriter(sw); dumpConnectionInfo(pwriter, false); pwriter.flush(); pwriter.close(); return sw.toString(); } public abstract InetSocketAddress getRemoteSocketAddress(); public abstract int getInterestOps(); /** * Print information about the connection. * @param brief iff true prints brief details, otw full detail * @return information about this connection */ protected synchronized void dumpConnectionInfo(PrintWriter pwriter, boolean brief) { pwriter.print(" "); pwriter.print(getRemoteSocketAddress()); pwriter.print("["); int interestOps = getInterestOps(); pwriter.print(interestOps == 0 ? "0" : Integer.toHexString(interestOps)); pwriter.print("](queued="); pwriter.print(getOutstandingRequests()); pwriter.print(",recved="); pwriter.print(getPacketsReceived()); pwriter.print(",sent="); pwriter.print(getPacketsSent()); if (!brief) { long sessionId = getSessionId(); if (sessionId != 0) { pwriter.print(",sid=0x"); pwriter.print(Long.toHexString(sessionId)); pwriter.print(",lop="); pwriter.print(getLastOperation()); pwriter.print(",est="); pwriter.print(getEstablished().getTime()); pwriter.print(",to="); pwriter.print(getSessionTimeout()); long lastCxid = getLastCxid(); if (lastCxid >= 0) { pwriter.print(",lcxid=0x"); pwriter.print(Long.toHexString(lastCxid)); } pwriter.print(",lzxid=0x"); pwriter.print(Long.toHexString(getLastZxid())); pwriter.print(",lresp="); pwriter.print(getLastResponseTime()); pwriter.print(",llat="); pwriter.print(getLastLatency()); pwriter.print(",minlat="); pwriter.print(getMinLatency()); pwriter.print(",avglat="); pwriter.print(getAvgLatency()); pwriter.print(",maxlat="); pwriter.print(getMaxLatency()); } } pwriter.print(")"); }
说明：ServerCnxn实现了Stats接口中的很多方法，其相对简单，不再累赘。
四、总结
本篇博文分析了ServerCnxn的源码，其是抽象类，定义了子类需要实现的方法，较为简单，也谢谢各位园友的观看~
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