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作者简介:高鹏,笔名八怪。《深入理解MySQL主从原理》图书作者,同时运营个人公众号“MySQL学习”,持续分享遇到的有趣case以及代码解析!
一直对这部分不太了解,稍微看了一下,但由于知识储备有限,错误在所难免。
总的看起来MySQL在这部分依旧使用了常规的 reactor+线程池高并发网络模型,这里我们以poll为列,有如下特点:
貌似看起来大佬的手法都是通用的,都是按照一定模式写出来的。当然实际上涉及的东西还是非常多,但是这里我们仅仅了解网络框架部分,对于线程池\vio通信模块\net协议模块不做讨论,因为我也不了解,这里主要看看网络框架。
<code class="language-js_darkmode__15">main ->mysqld_main -> Connection_acceptor<Mysqld_socket_listener>::connection_event_loop ->Mysqld_socket_listener::listen_for_connection_event ->poll ()
对于用户会话线程通常叫做thread_one_connection,接着会调用thd_prepare_connection->login_connection将准备对连接fd进行ppoll的超时参数设置为connect_timeout指定的值,也就是言外之意connect_timeout是在处理连接请求的时候生效的参数。然后thd_prepare_connection->login_connection->check_connection,在函数check_connection中完成主要任务是:
在login_connection的末尾会将连接fd的ppoll的timeout参数设置为read_timeout/write_timeout。最后接下来就是进行命令处理的环节了。也就是do_command。通常我们的会话就堵塞在这里等待客户端命令的到来如下:
#0 0x00007ffff5e2dcff in ppoll () from /lib64/libc.so.6
#1 0x00000000058bba82 in vio_io_wait (vio=0x7fffa801b990, event=VIO_IO_EVENT_READ, timeout=28800000) at /newdata/mysql-8.0.23/vio/viosocket.cc:847
#2 0x00000000058ba4c5 in vio_socket_io_wait (vio=0x7fffa801b990, event=VIO_IO_EVENT_READ) at /newdata/mysql-8.0.23/vio/viosocket.cc:105
#3 0x00000000058bc45b in vio_ssl_read (vio=0x7fffa801b990, buf=0x7fffa800e900 "\001", size=4) at /newdata/mysql-8.0.23/vio/viossl.cc:294
#4 0x00000000039bee83 in net_read_raw_loop (net=0x7fffa800d430, count=4) at /newdata/mysql-8.0.23/sql-common/net_serv.cc:1336
#5 0x00000000039bf1ef in net_read_packet_header (net=0x7fffa800d430) at /newdata/mysql-8.0.23/sql-common/net_serv.cc:1419
#6 0x00000000039c050a in net_read_packet (net=0x7fffa800d430, complen=0x7fffdc4fb9c8) at /newdata/mysql-8.0.23/sql-common/net_serv.cc:2010
#7 0x00000000039c0789 in net_read_uncompressed_packet (net=0x7fffa800d430, len=@0x7fffdc4fba08: 140736889600560) at /newdata/mysql-8.0.23/sql-common/net_serv.cc:2085
#8 0x00000000039c0a77 in my_net_read (net=0x7fffa800d430) at /newdata/mysql-8.0.23/sql-common/net_serv.cc:2161
#9 0x0000000003e23f6e in Protocol_classic::read_packet (this=0x7fffa801a780) at /newdata/mysql-8.0.23/sql/protocol_classic.cc:1404
#10 0x0000000003e25179 in Protocol_classic::get_command (this=0x7fffa801a780, com_data=0x7fffdc4fbb00, cmd=0x7fffdc4fbb2c) at /newdata/mysql-8.0.23/sql/protocol_classic.cc:2975
#11 0x00000000037f063d in do_command (thd=0x7fffa800b980) at /newdata/mysql-8.0.23/sql/sql_parse.cc:1266
#12 0x00000000039c5c91 in handle_connection (arg=0xbe8d880) at /newdata/mysql-8.0.23/sql/conn_handler/connection_handler_per_thread.cc:301
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