2024-01-18  阅读(120)
原文作者:hashcon 原文地址: https://zhanghaoxin.blog.csdn.net/article/details/50684702

2. 前端连接建立与认证

Created with Raphaël 2.1.0MySql连接建立以及认证过程clientclientMySqlMySql1.TCP连接请求2.接受TCP连接3.TCP连接建立4.握手包HandshakePacket5.认证包AuthPacket6.如果验证成功,则返回OkPacket7.默认会发送查询版本信息的包8.返回结果包

2.5 (7~8) 默认会发送查询版本信息的包,返回结果包

MySql客户端在连接建立后,默认会发送查询版本信息的包,这其实就是一个SQL查询请求了。只不过这个请求不用路由到后台某个数据库^_^。
连接成功建立后,连接绑定的RW线程会监听上面的读事件。在客户端发送查询版本信息的包之后,会触发RW线程去读取对应连接,过程与之前接收AuthPacket类似:
RW类代码片段

    //监听到有效读
    if (key.isValid() && key.isReadable()) {
                                        try {
                                            //异步读取数据并处理数据
                                            con.asynRead();
                                        } catch (IOException e) {
                                            con.close("program err:" + e.toString());
                                            continue;
                                        } catch (Exception e) {
                                            LOGGER.debug("caught err:", e);
                                            con.close("program err:" + e.toString());
                                            continue;
                                        }
                                    }

之后的读取过程也是调用AbstractConnection的asynRead()方法,进行异步读取。过程就不再赘述,读取到的数据交由FrontendCommandHandler处理。
查询版本信息的包(是一种CommandPacket)内容:

202401182020212061.png
CommandPacket:

  • packet length (3)
  • packet number (1)
  • command (1)
  • statement (null terminated string)

FrontendCommandHandler的处理方法:

    @Override
        public void handle(byte[] data)
        {
    
            if(source.getLoadDataInfileHandler()!=null&&source.getLoadDataInfileHandler().isStartLoadData())
            {
                MySQLMessage mm = new MySQLMessage(data);
                int  packetLength = mm.readUB3();
                if(packetLength+4==data.length)
                {
                    source.loadDataInfileData(data);
                }
                return;
            }
            switch (data[4])
            {
                case MySQLPacket.COM_INIT_DB:
                    commands.doInitDB();
                    source.initDB(data);
                    break;
                case MySQLPacket.COM_QUERY:
                    commands.doQuery();
                    source.query(data);
                    break;
                case MySQLPacket.COM_PING:
                    commands.doPing();
                    source.ping();
                    break;
                case MySQLPacket.COM_QUIT:
                    commands.doQuit();
                    source.close("quit cmd");
                    break;
                case MySQLPacket.COM_PROCESS_KILL:
                    commands.doKill();
                    source.kill(data);
                    break;
                case MySQLPacket.COM_STMT_PREPARE:
                    commands.doStmtPrepare();
                    source.stmtPrepare(data);
                    break;
                case MySQLPacket.COM_STMT_EXECUTE:
                    commands.doStmtExecute();
                    source.stmtExecute(data);
                    break;
                case MySQLPacket.COM_STMT_CLOSE:
                    commands.doStmtClose();
                    source.stmtClose(data);
                    break;
                case MySQLPacket.COM_HEARTBEAT:
                    commands.doHeartbeat();
                    source.heartbeat(data);
                    break;
                default:
                         commands.doOther();
                         source.writeErrMessage(ErrorCode.ER_UNKNOWN_COM_ERROR,
                                 "Unknown command");
    
            }
        }

根据CommandPacket的第五字节判断command类型,不同类型有不同的处理。
首先querycommand计数加1,之后调用对应FrontendConnection的query(byte[])方法:

    public void query(byte[] data) {
            if (queryHandler != null) {
                // 取得语句|get sql
                MySQLMessage mm = new MySQLMessage(data);
                //从第六字节开始读取|read from the 6th byte
                mm.position(5);
                String sql = null;
                try {
                    sql = mm.readString(charset);
                } catch (UnsupportedEncodingException e) {
                    writeErrMessage(ErrorCode.ER_UNKNOWN_CHARACTER_SET, "Unknown charset '" + charset + "'");
                    return;
                }
                if (sql == null || sql.length() == 0) {
                    writeErrMessage(ErrorCode.ER_NOT_ALLOWED_COMMAND, "Empty SQL");
                    return;
                }
    
                // sql = StringUtil.replace(sql, "`", "");
    
                // 移除末尾';'|remove last ';'
                if (sql.endsWith(";")) {
                    sql = sql.substring(0, sql.length() - 1);
                }
    
                // 记录SQL|record SQL
                this.setExecuteSql(sql);
    
                // 执行查询
                queryHandler.setReadOnly(privileges.isReadOnly(user));
                queryHandler.query(sql);
            } else {
                writeErrMessage(ErrorCode.ER_UNKNOWN_COM_ERROR, "Query unsupported!");
            }
        }

执行查询,调用对应的FrontendQueryHandler:

202401182020215392.png
这里,很明显,是ServerQueryHandler。

    public void query(String sql) {
    
            ServerConnection c = this.source;
            if (LOGGER.isDebugEnabled()) {
                LOGGER.debug(new StringBuilder().append(c).append(sql).toString());
            }
            //
            int rs = ServerParse.parse(sql);
            int sqlType = rs & 0xff;
    
            switch (sqlType) {
            case ServerParse.EXPLAIN:
                ExplainHandler.handle(sql, c, rs >>> 8);
                break;
            case ServerParse.EXPLAIN2:
                Explain2Handler.handle(sql, c, rs >>> 8);
                break;
            case ServerParse.SET:
                SetHandler.handle(sql, c, rs >>> 8);
                break;
            case ServerParse.SHOW:
                ShowHandler.handle(sql, c, rs >>> 8);
                break;
            case ServerParse.SELECT:
                if(QuarantineHandler.handle(sql, c)){
                    SelectHandler.handle(sql, c, rs >>> 8);
                }
                break;
            case ServerParse.START:
                StartHandler.handle(sql, c, rs >>> 8);
                break;
            case ServerParse.BEGIN:
                BeginHandler.handle(sql, c);
                break;
            case ServerParse.SAVEPOINT:
                SavepointHandler.handle(sql, c);
                break;
            case ServerParse.KILL:
                KillHandler.handle(sql, rs >>> 8, c);
                break;
            case ServerParse.KILL_QUERY:
                LOGGER.warn(new StringBuilder().append("Unsupported command:").append(sql).toString());
                c.writeErrMessage(ErrorCode.ER_UNKNOWN_COM_ERROR,"Unsupported command");
                break;
            case ServerParse.USE:
                UseHandler.handle(sql, c, rs >>> 8);
                break;
            case ServerParse.COMMIT:
                c.commit();
                break;
            case ServerParse.ROLLBACK:
                c.rollback();
                break;
            case ServerParse.HELP:
                LOGGER.warn(new StringBuilder().append("Unsupported command:").append(sql).toString());
                c.writeErrMessage(ErrorCode.ER_SYNTAX_ERROR, "Unsupported command");
                break;
            case ServerParse.MYSQL_CMD_COMMENT:
                c.write(c.writeToBuffer(OkPacket.OK, c.allocate()));
                break;
            case ServerParse.MYSQL_COMMENT:
                c.write(c.writeToBuffer(OkPacket.OK, c.allocate()));
                break;
                case ServerParse.LOAD_DATA_INFILE_SQL:
                    c.loadDataInfileStart(sql);
                    break;
            default:
                if(readOnly){
                    LOGGER.warn(new StringBuilder().append("User readonly:").append(sql).toString());
                    c.writeErrMessage(ErrorCode.ER_USER_READ_ONLY, "User readonly");
                    break;
                }
                if(QuarantineHandler.handle(sql, c)){
                    c.execute(sql, rs & 0xff);
                }
            }
        }

针对每种command,都有不同的handler和处理方式。之后如何处理,就在之后的SQL解析器等章节进行分析。

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