RW#run轮询注册队列中是否有AbstractConnection，若存在且为读事件则调用AbstractConnection#asynRead异步读取数据，实际处理逻辑见NIOSocketWR#asynRead-
NIOSocketWR#asynRead从 前端连接的channel中读取数据，并且保存到对应AbstractConnection的readBuffer中，之后调用AbstractConnection#onReadData处理读取到的数据@Override public void asynRead() throws IOException { ByteBuffer theBuffer = con.readBuffer; if (theBuffer == null) { theBuffer = con.processor.getBufferPool().allocate(con.processor.getBufferPool().getChunkSize()); con.readBuffer = theBuffer; } // 从 SocketChannel 中读取数据，并且保存到 AbstractConnection 的 readBuffer 中，readBuffer 处于 write mode，返回读取了多少字节 int got = channel.read(theBuffer); // 调用处理读取到的数据的方法 con.onReadData(got); } AbstractConnection#onReadData读取readBuffer中的数据并调用AbstractConnection#handle方法进行下一步处理，其内部调用FrontendCommandHandler#handleFrontendCommandHandler#handle根据data[4]来判断命令类型，客户端命令请求报文格式如下图：
data 的第五个字节存储命令类型，客户端命令请求报文命令类型详情表见附录1。我们以 MySQLPacket.COM_QUERY 为例进行接下来的讨论。当 data[4] == MySQLPacket.COM_QUERY 时，调用 FrontendConnection#query(byte[])
public void handle(byte[] data) {
// 判断命令类型
switch (data[4]) {
...
// INSERT/SELECT/UPDATE/DELETE 等 SQL 归属于 MySQLPacket.COM_QUERY
case MySQLPacket.COM_QUERY:
commands.doQuery();
source.query(data);
break;
...
}
}
-
FrontendConnection#query(byte[])将data字节数组转化成String类型的 SQL，ServerQueryHandler#query(String)方法public void query(byte[] data) { MySQLMessage mm = new MySQLMessage(data); // 从 data[5] 即第六个字节开始读取参数体 mm.position(5); String sql = mm.readString(charset); // 执行 sql 语句，内部调用 ServerQueryHandler#query(String) this.query( sql ); } -
ServerQueryHandler#query(String)解析 SQL 类型，根据sqlType使用不同的Handler做处理@Override public void query(String sql) { ServerConnection c = this.source; /* 解析 SQL 类型 */ int rs = ServerParse.parse(sql); int sqlType = rs & 0xff; switch (sqlType) { // explain2 datanode=? sql=? case ServerParse.EXPLAIN2: Explain2Handler.handle(sql, c, rs >>> 8); break; case ServerParse.SELECT: SelectHandler.handle(sql, c, rs >>> 8); break; case ... default: if (readOnly) { LOGGER.warn(new StringBuilder().append("User readonly:").append(sql).toString()); c.writeErrMessage(ErrorCode.ER_USER_READ_ONLY, "User readonly"); break; } c.execute(sql, rs & 0xff); } } -
例如
sqlType == ServerParse.SELECT时使用SelectHandler做进一步处理public static void handle(String stmt, ServerConnection c, int offs) { int offset = offs; c.setExecuteSql(null); switch (ServerParseSelect.parse(stmt, offs)) { case ServerParseSelect.DATABASE: SelectDatabase.response(c); break; case ServerParseSelect.USER: SelectUser.response(c); break; case ... default: c.setExecuteSql(stmt); c.execute(stmt, ServerParse.SELECT); } } -
SelectHandler进一步解析select语句，针对不同的select进行不同的处理，默认直接调用ServerConnection#execute(java.lang.String, int)，该方法首先进行一些常规检查（连接状态检查、事务状态检查、当前 DB 检查等），然后调用ServerConnection#routeEndExecuteSQL进行路由计算（包括全局序列号、SQL 语句拦截等。路由计算详细另述）并得到路由结果RouteResultset，之后调用NonBlockingSession#executepublic void routeEndExecuteSQL(String sql, final int type, final SchemaConfig schema) { // 路由计算 RouteResultset rrs = MycatServer .getInstance() .getRouterservice() .route(MycatServer.getInstance().getConfig().getSystem(), schema, type, sql, this.charset, this); if (rrs != null) { // session 执行 session.execute(rrs, rrs.isSelectForUpdate() ? ServerParse.UPDATE : type); } } -
NonBlockingSession#execute获取路由的dataNode节点，若节点数为 1 则调用SingleNodeHandler#execute处理 sql，否则调用MultiNodeQueryHandler#execute处理 SQL。此处我们假定前端 SQL 命令只路由到一个 dataNode，则调用SingleNodeHandler#execute处理 SQL/** * NonBlockingSession#execute */ @Override public void execute(RouteResultset rrs, int type) { RouteResultsetNode[] nodes = rrs.getNodes(); if (nodes.length == 1) { singleNodeHandler = new SingleNodeHandler(rrs, this); singleNodeHandler.execute(); } else { multiNodeHandler = new MultiNodeQueryHandler(type, rrs, autocommit, this); multiNodeHandler.execute(); } } -
SingleNodeHandler#execute获取后端连接BackendConnection，并调用SingleNodeHandler#_execute，该方法直接调用BackendConnection#executepublic void execute() throws Exception { // 获取后端数据库连接 final BackendConnection conn = session.getTarget(node); // 若存在 dataNode 对应的 BackendConnection if (session.tryExistsCon(conn, node)) { _execute(conn); } else { // create new connection do something... } } private void _execute(BackendConnection conn) { conn.execute(node, session.getSource(), session.getSource().isAutocommit()); } -
当 schema.xml 中配置
dbDriver=='jdbc'时，调用JDBCConnection#execute处理 SQL（JDBCConnection继承BackendConnection）。该方法新开一个线程处理 SQL，最终调用JDBCConnection#ouputResultSet执行 SQL 并将结果写入ServerConnection// JDBCConnection.class @Override public void execute(final RouteResultsetNode node, final ServerConnection source, final boolean autocommit) { this.sqlSelectLimit = source.getSqlSelectLimit(); Runnable runnable = new Runnable() { @Override public void run() { // 调用 JDBCConnection#ouputResultSet executeSQL(node, source, autocommit); } }; MycatServer.getInstance().getBusinessExecutor().execute(runnable); } -
JDBCConnection#ouputResultSet获取数据库连接并执行 SQL，然后将得到的结果集ResultSet解析为 ResultSet 响应报文并写入ServerConnectionprivate void ouputResultSet(ServerConnection sc, String sql) throws SQLException { ResultSet rs = null; Statement stmt = null; try { stmt = con.createStatement(); rs = stmt.executeQuery(sql); ListfieldPks = new LinkedList (); // 根据 resultset 加载列信息，保存至 fieldPks ResultSetUtil.resultSetToFieldPacket(sc.getCharset(), fieldPks, rs, this.isSpark); // 获取列数 int colunmCount = fieldPks.size(); ByteBuffer byteBuf = sc.allocate(); /* 1 写入 resultset header packet */ ResultSetHeaderPacket headerPkg = new ResultSetHeaderPacket(); headerPkg.fieldCount = fieldPks.size(); headerPkg.packetId = ++packetId; // 将 ResultSetHeaderPacket 的数据写入 byteBuf byteBuf = headerPkg.write(byteBuf, sc, true); byteBuf.flip(); byte[] header = new byte[byteBuf.limit()]; // 将 byteBuf 中的信息写入 header 中 byteBuf.get(header); // byteBuf 标记归位 byteBuf.clear(); /* 2 写入 field packet */ List itor = fieldPks.iterator(); while (itor.hasNext()) { FieldPacket curField = itor.next(); curField.packetId = ++packetId; // 将 FieldPacket 的数据写入 byteBuf byteBuf = curField.write(byteBuf, sc, false); // position 设回 0，并将 limit 设成之前的 position 的值 // limit：缓冲区数组中不可操作的下一个元素的位置：limit<=capacity byteBuf.flip(); byte[] field = new byte[byteBuf.limit()]; // 将 byteBuf 中的信息写入 field 中 byteBuf.get(field); byteBuf.clear(); // 将 field 放入 fields fields.add(field); } /* 3 写入 EOF packet */ EOFPacket eofPckg = new EOFPacket(); eofPckg.packetId = ++packetId; // 将 EOFPacket 的数据写入 byteBuf byteBuf = eofPckg.write(byteBuf, sc, false); byteBuf.flip(); byte[] eof = new byte[byteBuf.limit()]; // 将 byteBuf 中的信息写入 eof 中 byteBuf.get(eof); byteBuf.clear(); this.respHandler.fieldEofResponse(header, fields, eof, this); /* 4 写入 Row Data packet */ // output row while (rs.next()) { ResultSetMetaData resultSetMetaData = rs.getMetaData(); int size = resultSetMetaData.getColumnCount(); StringBuilder builder = new StringBuilder(); for (int i = 1; i <= size; i++) { builder.append(resultSetMetaData.getColumnName(i) + "=" + rs.getString(i)); if (i < size) { builder.append(", "); } } LOGGER.debug("JDBCConnection.ouputResultSet sql: {}, resultSet: {}", sql, builder.toString()); RowDataPacket curRow = new RowDataPacket(colunmCount); for (int i = 0; i < colunmCount; i++) { int j = i + 1; if (MysqlDefs.isBianry((byte) fieldPks.get(i).type)) { curRow.add(rs.getBytes(j)); } else if (fieldPks.get(i).type == MysqlDefs.FIELD_TYPE_DECIMAL || fieldPks.get(i).type == (MysqlDefs.FIELD_TYPE_NEW_DECIMAL - 256)) { // field type is unsigned byte // ensure that do not use scientific notation format BigDecimal val = rs.getBigDecimal(j); curRow.add(StringUtil.encode(val != null ? val.toPlainString() : null, sc.getCharset())); } else { curRow.add(StringUtil.encode(rs.getString(j), sc.getCharset())); } } curRow.packetId = ++packetId; // 将 RowDataPacket 的数据写入 byteBuf byteBuf = curRow.write(byteBuf, sc, false); byteBuf.flip(); byte[] row = new byte[byteBuf.limit()]; byteBuf.get(row); byteBuf.clear(); this.respHandler.rowResponse(row, this); } fieldPks.clear(); // end row /* 5 写入 EOF packet */ eofPckg = new EOFPacket(); eofPckg.packetId = ++packetId; byteBuf = eofPckg.write(byteBuf, sc, false); byteBuf.flip(); eof = new byte[byteBuf.limit()]; byteBuf.get(eof); sc.recycle(byteBuf); this.respHandler.rowEofResponse(eof, this); } finally { if (rs != null) { try { rs.close(); } catch (SQLException e) { } } if (stmt != null) { try { stmt.close(); } catch (SQLException e) { } } } }