分布式数据库中间件–(2)Cobar与客户端的握手认证

Cobar启动完成，监听特定端口。整个认证的流程图： NIOAcceptor类继承自Thread类，该类的对象会以线程的方式运行，进行连接的监听。 NIOAcceptor启动的初始化过程如下： 1 、打开一个selector，获取一个ServerSocketChannel对象，对该对象的socket绑定特定的

Cobar启动完成，监听特定端口。整个认证的流程图：

NIOAcceptor类继承自Thread类，该类的对象会以线程的方式运行，进行连接的监听。

NIOAcceptor启动的初始化过程如下：

1 、打开一个selector，获取一个ServerSocketChannel对象，对该对象的socket绑定特定的监听端口，并设置该channel为非阻塞模式，然后想selector注册该channel，绑定感兴趣的事件位OP_ACCEPT。

01	public <code class="Brush plain">NIOAcceptor(String name, <code class="Brush keyword">int <code class="Brush plain">port, FrontendConnectionFactory factory) <code class="Brush keyword">throws <code class="Brush plain">IOException {

02	<code class="Brush keyword">super<code class="Brush plain">.setName(name);

03	<code class="Brush keyword">this<code class="Brush plain">.port = port;

04	<code class="Brush keyword">this<code class="Brush plain">.selector = Selector.open();

05	<code class="Brush keyword">this<code class="Brush plain">.serverChannel = ServerSocketChannel.open();

06	<code class="Brush comments">//ServerSocket使用TCP

07	<code class="Brush keyword">this<code class="Brush plain">.serverChannel.socket().bind(<code class="Brush keyword">new <code class="Brush plain">InetSocketAddress(port));

08	<code class="Brush keyword">this<code class="Brush plain">.serverChannel.configureBlocking(<code class="Brush keyword">false<code class="Brush plain">);

09	<code class="Brush keyword">this<code class="Brush plain">.serverChannel.register(selector, SelectionKey.OP_ACCEPT);

10	<code class="Brush keyword">this<code class="Brush plain">.factory = factory;

11

}

2、 然后会启动该线程，线程的run函数如下：

01	public <code class="Brush keyword">void <code class="Brush plain">run() {

02	<code class="Brush keyword">final <code class="Brush plain">Selector selector = <code class="Brush keyword">this<code class="Brush plain">.selector;

03	<code class="Brush comments">//线程一直循环

04	<code class="Brush keyword">for <code class="Brush plain">(;;) {

05	<code class="Brush plain">++acceptCount;

06	<code class="Brush keyword">try <code class="Brush plain">{

07	<code class="Brush plain">selector.select(1000L);

08	<code class="Brush plain">Set<selectionkey> keys = selector.selectedKeys();</selectionkey>

09	<code class="Brush keyword">try <code class="Brush plain">{

10	<code class="Brush keyword">for <code class="Brush plain">(SelectionKey key : keys) {

11	<code class="Brush keyword">if <code class="Brush plain">(key.isValid() && key.isAcceptable()) {

12	<code class="Brush comments">//接受来自客户端的连接

13	<code class="Brush plain">accept();

14	<code class="Brush plain">} <code class="Brush keyword">else <code class="Brush plain">{

15	<code class="Brush plain">key.cancel();

16	<code class="Brush plain">}

17	<code class="Brush plain">}

18	<code class="Brush plain">} <code class="Brush keyword">finally <code class="Brush plain">{

19	<code class="Brush plain">keys.clear();

20	<code class="Brush plain">}

21	<code class="Brush plain">} <code class="Brush keyword">catch <code class="Brush plain">(Throwable e) {

22	<code class="Brush plain">LOGGER.warn(getName(), e);

23	<code class="Brush plain">}

24	<code class="Brush plain">}

25

}

3 、 该线程会一直循环监听想该selector注册过的server channel所感兴趣的事件（OP_ACCEPT），当有新的连接请求时，selector就会返回，keys就是请求连接的所有的包含channel的key集合。

SelectionKey有如下属性：

• interest集合(使用&操作SelectionKey.OP_ACCEPT和key.interestOps())
• ready集合(key.readyOps()，可以使用&操作检测该集合，也可以使用is方法)
• Channel(key.channel())
• Selector(key.selector())
• 附加对象(key.attach(obj) Object obj = key.attachment())

  4、 然后遍历该集合，如果集合中的key没有被cancel，并且这个key的channel已经做好接受一个新的socket连接的准备，则接受该连接。

  accept()的具体代码如下：

  01	private <code class="Brush keyword">void <code class="Brush plain">accept() {

  02	<code class="Brush plain">SocketChannel channel = <code class="Brush keyword">null<code class="Brush plain">;

  03	<code class="Brush keyword">try <code class="Brush plain">{

  04	<code class="Brush comments">//从服务器端获取管道,为一个新的连接返回channel

  05	<code class="Brush plain">channel = serverChannel.accept();

  06	<code class="Brush comments">//配置管道为非阻塞

  07	<code class="Brush plain">channel.configureBlocking(<code class="Brush keyword">false<code class="Brush plain">);

  08

  09	<code class="Brush comments">//前端连接工厂对管道进行配置，设置socket的收发缓冲区大小，TCP延迟等

  10	<code class="Brush comments">//然后由成员变量factory的类型生产对于的类型的连接

  11	<code class="Brush comments">//比如ServerConnectionFactory会返回ServerConnection实例，并对其属性进行设置

  12	<code class="Brush plain">FrontendConnection c = factory.make(channel);

  13	<code class="Brush comments">//设置连接属性

  14	<code class="Brush plain">c.setAccepted(<code class="Brush keyword">true<code class="Brush plain">);

  15	<code class="Brush plain">c.setId(ID_GENERATOR.getId());

  16	<code class="Brush comments">//从processors中选择一个NIOProcessor，将其和该连接绑定

  17	<code class="Brush plain">NIOProcessor processor = nextProcessor();

  18	<code class="Brush plain">c.setProcessor(processor);

  19	<code class="Brush comments">//向读反应堆注册该连接，加入待处理队列

  20	<code class="Brush comments">//select选择到感兴趣的事件后，会进行调用connection的read函数

  21	<code class="Brush plain">processor.postRegister(c);

  22	<code class="Brush plain">} <code class="Brush keyword">catch <code class="Brush plain">(Throwable e) {

  23	<code class="Brush plain">closeChannel(channel);

  24	<code class="Brush plain">LOGGER.warn(getName(), e);

  25	<code class="Brush plain">}

  26	<code class="Brush plain">}

  首先从serverchannel中accept后会返回一个socketchannel对象，然后设置该socket channel属性位非阻塞模式，然后将channel交给ServerConnectionFactory工厂，会产生一个ServerConnection对象。

  

  FrontendConnectionFactory是一个抽象类，其中的getConnection方法是抽象方法，有具体子类连接工厂来实现。FrontendConnectionFactory的make方法对channel中的socket进行属性设置（接收和发送的缓冲区大小、延时、KeepAlive等），然后调用具体调用具体子类（ServerConnectionFactory）的getConnection来返回一个ServerConnection，返回后会在进行设置一下该ServerConnection的包头大小、最大包大小、设置连接的发送缓冲区队列、超时时间、字符编码，到此，工厂完成了新建连接的工作，返回一个连接的对象。返回后将该连接分配给一个processor，该processor会将该连接保存，processor也会对连接进行定期检查。

  5、 processor还会向自己的reactorR进行注册该连接，加入reactorR的处理队列，并唤醒阻塞的select()方法。

  反应堆中Reactor的R线程运行代码：

  01	public <code class="Brush keyword">void <code class="Brush plain">run() {

  02	<code class="Brush keyword">final <code class="Brush plain">Selector selector = <code class="Brush keyword">this<code class="Brush plain">.selector;

  03	<code class="Brush keyword">for <code class="Brush plain">(;;) {

  04	<code class="Brush plain">++reactCount;

  05	<code class="Brush keyword">try <code class="Brush plain">{

  06	<code class="Brush keyword">int <code class="Brush plain">res = selector.select();

  07	<code class="Brush plain">LOGGER.debug(reactCount + <code class="Brush string">">>NIOReactor接受连接数:" <code class="Brush plain">+ res);

  08	<code class="Brush plain">register(selector);

  09	<code class="Brush plain">Set<selectionkey> keys = selector.selectedKeys();</selectionkey>

  10	<code class="Brush keyword">try <code class="Brush plain">{

  11	<code class="Brush keyword">for <code class="Brush plain">(SelectionKey key : keys) {

  12	<code class="Brush plain">Object att = key.attachment();

  13	<code class="Brush keyword">if <code class="Brush plain">(att != <code class="Brush keyword">null <code class="Brush plain">&& key.isValid()) {

  14	<code class="Brush keyword">int <code class="Brush plain">readyOps = key.readyOps();

  15	<code class="Brush keyword">if <code class="Brush plain">((readyOps & SelectionKey.OP_READ) != <code class="Brush value">0<code class="Brush plain">) {

  16	<code class="Brush plain">LOGGER.debug(<code class="Brush string">"select读事件"<code class="Brush plain">);

  17	<code class="Brush plain">read((NIOConnection) att);

  18	<code class="Brush plain">} else if ((readyOps & SelectionKey.OP_WRITE) != 0) {

  19	<code class="Brush plain">LOGGER.debug(<code class="Brush string">"select写事件"<code class="Brush plain">);

  20	<code class="Brush plain">write((NIOConnection) att);

  21	<code class="Brush plain">} <code class="Brush keyword">else <code class="Brush plain">{

  22	<code class="Brush plain">key.cancel();

  23	<code class="Brush plain">}

  24	<code class="Brush plain">} <code class="Brush keyword">else <code class="Brush plain">{

  25	<code class="Brush plain">key.cancel();

  26	<code class="Brush plain">}

  27	<code class="Brush plain">}

  28	<code class="Brush plain">} <code class="Brush keyword">finally <code class="Brush plain">{

  29	<code class="Brush plain">keys.clear();

  30	<code class="Brush plain">}

  31	<code class="Brush plain">} <code class="Brush keyword">catch <code class="Brush plain">(Throwable e) {

  32	<code class="Brush plain">LOGGER.warn(name, e);

  33	<code class="Brush plain">}

  34	<code class="Brush plain">}

  35

  }

  该R线程也会一直循环运行，如果向该selector注册过的channel没有对应的感兴趣的事件发生，就会阻塞，直到有感兴趣的事件发生或被wakeup。返回后会运行register函数，将之前加入该reactor连接队列中的所有连接向该selector注册OP_READ事件。该注册的动作会调用Connection对象中的register方法进行注册

  channel.register(selector, SelectionKey.OP_READ, this);

  注意最后一个this指针参数，表示将该连接作为附件，注册到selector，当有感兴趣的时间发生时，函数selector.selectedKeys()返回的SelectionKey集合中的对象中使用key.attachment()即可获取到上面注册时绑定的connection对象指针附件。目的就是为了通过该附件对象调用该连接类中定义的read函数来完成功能。如下所示：

  1	private <code class="Brush keyword">void <code class="Brush plain">read(NIOConnection c) {

  2	<code class="Brush keyword">try <code class="Brush plain">{

  3	<code class="Brush plain">c.read();

  4	<code class="Brush plain">} catch (Throwable e) {

  5	<code class="Brush plain">c.error(ErrorCode.ERR_READ, e);

  6	<code class="Brush plain">}

  7

  }

  6、 连接类中定义的read函数定义在AbstractConnection类中。在该read函数（该read函数涉及到的逻辑比较复杂，先不深究）中，完成从channel中读取数据到buffer，然后从buffer中提取byte数据交给具体子类（FrontendConnection）的handle()方法进行处理。

  7、 该方法会从processor的线程池中获取一个线程，来异步执行数据的处理。处理会调用成员handler的handle方法来对数据进行处理。这里，在FrontendConnection的构造函数中定handler设置为FrontendAuthenticator（进行前端认证）。

  01	public <code class="Brush keyword">void <code class="Brush plain">handle(<code class="Brush keyword">final <code class="Brush keyword">byte<code class="Brush plain">[] data) {

  02	<code class="Brush comments">// 从线程池获取一个线程,异步处理前端数据

  03	<code class="Brush comments">// 从processor中的线程池中获取一个可以执行的线程,执行Runnable任务

  04	<code class="Brush plain">processor.getHandler().execute(<code class="Brush keyword">new <code class="Brush plain">Runnable() {

  05	<code class="Brush color1">@Override

  06	public <code class="Brush keyword">void <code class="Brush plain">run() {

  07	<code class="Brush keyword">try <code class="Brush plain">{

  08	<code class="Brush comments">//调用具体NIOHandler子类的handle函数

  09	<code class="Brush plain">handler.handle(data);

  10	<code class="Brush plain">} catch (Throwable t) {

  11	<code class="Brush plain">error(ErrorCode.ERR_HANDLE_DATA, t);

  12	<code class="Brush plain">}

  13	<code class="Brush plain">}

  14	<code class="Brush plain">});

  15

  }

  8、 handler在构造函数中初始化成前端认证处理器，用于处理前端权限认证。

  1	public <code class="Brush plain">FrontendConnection(SocketChannel channel) {

  2	<code class="Brush keyword">super<code class="Brush plain">(channel);

  3	<code class="Brush plain">.....................

  4	<code class="Brush comments">//前端认证处理器

  5	<code class="Brush keyword">this<code class="Brush plain">.handler = <code class="Brush keyword">new <code class="Brush plain">FrontendAuthenticator(<code class="Brush keyword">this<code class="Brush plain">);

  6

  }

  9、 由于Cobar是基于MySQL协议的，所以需要分析一下MySQL协议的具体格式。下面就先分析一下MySQL认证数据包的格式：

  每个报文都分为消息头和消息体两部分，其中消息头是固定的四个字节，报文结构如下：

  

  登录认证报文的报文数据部分格式如下：

  

  10、 FrontendAuthenticator类对上面的数据包的具体处理如下：

  • 读取信息到认证包对象
  • 核对用户
  • 核对密码
  • 检查schema

    如果出现错误，会提示相应的错误信息，如果正确会向客户端发送认证成功提示。

    01	public <code class="Brush keyword">void <code class="Brush plain">handle(<code class="Brush keyword">byte<code class="Brush plain">[] data) {

    02	<code class="Brush comments">// check quit packet

    03	<code class="Brush keyword">if <code class="Brush plain">(data.length == QuitPacket.QUIT.length && data[<code class="Brush value">4<code class="Brush plain">] == MySQLPacket.COM_QUIT) {

    04	<code class="Brush plain">source.close();

    05	<code class="Brush keyword">return<code class="Brush plain">;

    06	<code class="Brush plain">}

    07

    08	<code class="Brush comments">//新建认证包对象

    09	<code class="Brush plain">AuthPacket auth = <code class="Brush keyword">new <code class="Brush plain">AuthPacket();

    10	<code class="Brush comments">//读取认证包到对象

    11	<code class="Brush plain">auth.read(data);

    12	<code class="Brush comments">// check user

    13	<code class="Brush keyword">if <code class="Brush plain">(!checkUser(auth.user, source.getHost())) {

    14	<code class="Brush plain">failure(ErrorCode.ER_ACCESS_DENIED_ERROR, <code class="Brush string">"Access denied for user '" <code class="Brush plain">+ auth.user + <code class="Brush string">"'"<code class="Brush plain">);

    15	<code class="Brush keyword">return<code class="Brush plain">;

    16	<code class="Brush plain">}

    17	<code class="Brush comments">// check password

    18	<code class="Brush keyword">if <code class="Brush plain">(!checkPassword(auth.password, auth.user)) {

    19	<code class="Brush plain">failure(ErrorCode.ER_ACCESS_DENIED_ERROR, <code class="Brush string">"Access denied for user '" <code class="Brush plain">+ auth.user + <code class="Brush string">"'"<code class="Brush plain">);

    20	<code class="Brush keyword">return<code class="Brush plain">;

    21	<code class="Brush plain">}

    22	<code class="Brush comments">// check schema

    23	<code class="Brush keyword">switch <code class="Brush plain">(checkSchema(auth.database, auth.user)) {

    24	<code class="Brush keyword">case <code class="Brush plain">ErrorCode.ER_BAD_DB_ERROR:

    25	<code class="Brush plain">failure(ErrorCode.ER_BAD_DB_ERROR, <code class="Brush string">"Unknown database '" <code class="Brush plain">+ auth.database + <code class="Brush string">"'"<code class="Brush plain">);

    26	<code class="Brush keyword">break<code class="Brush plain">;

    27	<code class="Brush keyword">case <code class="Brush plain">ErrorCode.ER_DBACCESS_DENIED_ERROR:

    28	<code class="Brush plain">String s = <code class="Brush string">"Access denied for user '" <code class="Brush plain">+ auth.user + <code class="Brush string">"' to database '" <code class="Brush plain">+ auth.database + <code class="Brush string">"'"<code class="Brush plain">;

    29	<code class="Brush plain">failure(ErrorCode.ER_DBACCESS_DENIED_ERROR, s);

    30	<code class="Brush keyword">break<code class="Brush plain">;

    31	<code class="Brush keyword">default<code class="Brush plain">:

    32	<code class="Brush comments">//认证成功,向客户端发送认证结果消息

    33	<code class="Brush plain">success(auth);

    34	<code class="Brush plain">}

    35

    }

    在上面的auth.read函数中会按9中的协议格式进行读取数据到auth对象。认证成功后会执行：

    01	protected <code class="Brush keyword">void <code class="Brush plain">success(AuthPacket auth) {

    02	<code class="Brush comments">//认证通过,设置连接属性:已认证\用户\数据库\处理器

    03	<code class="Brush plain">source.setAuthenticated(<code class="Brush keyword">true<code class="Brush plain">);

    04	<code class="Brush plain">source.setUser(auth.user);

    05	<code class="Brush plain">source.setSchema(auth.database);

    06	<code class="Brush plain">source.setCharsetIndex(auth.charsetIndex);

    07	<code class="Brush comments">//设置该连接的连接处理器为前端命令处理器

    08	<code class="Brush plain">source.setHandler(<code class="Brush keyword">new <code class="Brush plain">FrontendCommandHandler(source));

    09	<code class="Brush plain">.......

    10	<code class="Brush plain">ByteBuffer buffer = source.allocate();

    11	<code class="Brush plain">source.write(source.writeToBuffer(AUTH_OK, buffer));

    12

    }

    可以看到，在上面的函数中，设置连接对象source中的成员（是否认证、用户、数据库、编码、处理该连接后续数据包的处理器【handle方法】）

    然后回复认证成功的消息。后面客户端再发送消息，会交给前端命令处理器进行处理。

    客户端进行链接的时候Cobar服务器的输出：

    01	16:59:19,388 INFO ===============================================

    02	16:59:19,389 INFO Cobar is ready to startup ...

    03	16:59:19,389 INFO Startup processors ...

    04	16:59:19,455 INFO Startup connector ...

    05	16:59:19,460 INFO Initialize dataNodes ...

    06	16:59:19,506 INFO dnTest1:0 init success

    07	16:59:19,514 INFO dnTest3:0 init success

    08	16:59:19,517 INFO dnTest2:0 init success

    09	16:59:19,527 INFO CobarServer is started and listening on 8066

    10	16:59:19,527 INFO ===============================================

    11	16:59:23,459 DEBUG 1>>NIOReactor接受连接数:0

    12	16:59:23,464 DEBUG 2>>NIOReactor接受连接数:1

    13	16:59:23,465 DEBUG select读事件

    14	16:59:23,465 INFO com.alibaba.cobar.net.handler.FrontendAuthenticator接收的请求长度:62

    15	58 0 0 1 5 166 15 0 0 0 0 1 33 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 114 111 111 116 0 20 169 171 247 102 133 96 158 224 121 22 226 229 88 244 119 238 185 61 124 219

    16	16:59:23,468 INFO [thread=Processor1-H0,class=ServerConnection,host=192.168.137.8,port=46101,schema=null]'root' login success

    客户端得到的回复：

    01	yan@yan-Z400:~$ mysql -uroot -p** -P8066 -h192.168.137.8

    02	Welcome to the MySQL monitor. Commands end with ; or \g.

    03	Your MySQL connection id is 1

    04	Server version: 5.1.48-cobar-1.2.7 Cobar Server (ALIBABA)

    05

    06	Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

    07

    08	Oracle is a registered trademark of Oracle Corporation and/or its

    09	affiliates. Other names may be trademarks of their respective

    10

    owners.

    11

    12	Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

    13

    14

    mysql>

    MySQL客户端的命令处理，具体后续会分析。
    

    作者：GeekCome出处：极客来原文：分布式数据库中间件–(2) Cobar与客户端的握手认证提示：本文版权归作者，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接。如果对文章有任何问题，都可以在评论中留言，我会尽可能的答复您，谢谢你的阅读

    
    
    （完）