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一次tcp错误排查

· 2 min read

一个使用php的workman的代码抛出了这样的异常

fwrite(): send of 157 bytes failed with errno=11 Resource temporarily unavailable

socket是使用了noblocking的,结果有一个这个错误,结果发现是已经修复了不抛异常了,但是在我的php5.6的版本还是旧的代码,所以还是会抛这个异常,所以排查了一天,不是bug 最新的修改

https://github.com/php/php-src/pull/5026/files
	didwrite = send(sock->socket, buf, XP_SOCK_BUF_SIZE(count), (sock->is_blocked && ptimeout) ? MSG_DONTWAIT : 0);

	if (didwrite <= 0) {
		char *estr;
		int err = php_socket_errno();
		if (err == EWOULDBLOCK || err == EAGAIN) {
			if (sock->is_blocked) {
				int retval;

				sock->timeout_event = 0;

				do {
					retval = php_pollfd_for(sock->socket, POLLOUT, ptimeout);

					if (retval == 0) {
						sock->timeout_event = 1;
						break;
					}

					if (retval > 0) {
						/* writable now; retry */
						goto retry;
					}

					err = php_socket_errno();
				} while (err == EINTR);
			} else {
				/* EWOULDBLOCK/EAGAIN is not an error for a non-blocking stream.
				 * Report zero byte write instead. */
				return 0;
			}
		}

		estr = php_socket_strerror(err, NULL, 0);
		php_error_docref(NULL, E_NOTICE, "Send of " ZEND_LONG_FMT " bytes failed with errno=%d %s",
				(zend_long)count, err, estr);
		efree(estr);
	}

	if (didwrite > 0) {
		php_stream_notify_progress_increment(PHP_STREAM_CONTEXT(stream), didwrite, 0);
	}

	return didwrite;
}

论文的有趣性

· One min read

背景​

论文很好玩的,我很希望可以看很多很多的论文.

有时候我感觉论文里面的数学真的很漂亮

mysqlbinlog

· One min read

如何读取mysql的binlog?​

可以使用mysql默认的mysqlbinlog

重要的是需要加v 命令

mysqlbinlog   -v  mysql-bin.000006

你会看到具体的sql了,我这里的sql是

#210311 14:51:10 server id 1  end_log_pos 1606 CRC32 0x783f56ab 	Query	thread_id=64	exec_time=0	error_code=0
SET TIMESTAMP=1615445470/*!*/;
BEGIN
/*!*/;
# at 1606
#210311 14:51:10 server id 1  end_log_pos 1672 CRC32 0x52632df5 	Table_map: `user_db`.`tb_user` mapped to number 119
# at 1672
#210311 14:51:10 server id 1  end_log_pos 1783 CRC32 0xf565f574 	Update_rows: table id 119 flags: STMT_END_F

BINLOG '
3r1JYBMBAAAAQgAAAIgGAAAAAHcAAAAAAAEAB3VzZXJfZGIAB3RiX3VzZXIABgMPDw8BDwgUAEAA
FAAyADj1LWNS
3r1JYB8BAAAAbwAAAPcGAAAAAHcAAAAAAAEAAgAG///AYAAAAAI5NgYxMjM0NTYFOTk5OTcSD3po
YW5nc2FuQGJ1Zy5jbsBgAAAAATUGMTIzNDU2BTk5OTk3Eg96aGFuZ3NhbkBidWcuY2509WX1
'/*!*/;
### UPDATE `user_db`.`tb_user`
### WHERE
###   @1=96
###   @2='96'
###   @3='123456'
###   @4='99997'
###   @5=18
###   @6='zhangsan@bug.cn'
### SET
###   @1=96
###   @2='5'
###   @3='123456'
###   @4='99997'
###   @5=18
###   @6='zhangsan@bug.cn'
# at 1783
#210311 14:51:10 server id 1  end_log_pos 1814 CRC32 0xa90279ec 	Xid = 1794
COMMIT/*!*/;
SET @@SESSION.GTID_NEXT= 'AUTOMATIC' /* added by mysqlbinlog */ /*!*/;
DELIMITER ;
# End of log file
/*!50003 SET COMPLETION_TYPE=@OLD_COMPLETION_TYPE*/;
/*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=0*/;

协议流程​

COM_BINLOG_DUMP -> com_binlog_dump

相关阅读​

https://www.cnblogs.com/netsa/p/7350629.html https://dev.mysql.com/doc/internals/en/replication-protocol.html

docker-compose spec

· One min read

docker-compose 的spec

TOP :
   version
   service
   network
   volumes
   config
   secrets

service : build deploy

Each service MAY also include a Build section, which defines how to create the Docker image for the service. Compose implementations MAY support building docker images using this service definition. If not implemented the Build section SHOULD be ignored and the Compose file MUST still be considered valid.

Build support is an OPTIONAL aspect of the Compose specification, and is described in detail here

Each Service defines runtime constraints and requirements to run its containers. The deploy section groups these constraints and allows the platform to adjust the deployment strategy to best match containers' needs with available resources.

相关文档​

如何写一个正确的代码

· One min read

我们如何写一个正确的代码?

答案是形式化验证,其中一个是霍尔逻辑

举个例子

快速幂
x> 0 
x/2/2 ... 必定会归到1 或者0, 所以递归会有限次

快速幂
a^x = floor(a^(x/2))^2 *a^(x%1);
fun(a,x) ={
    if(x== 0){
        return 1;
    }elseif(x== 1){
        return  a;
    }
    return  fun(a , floor(x/2)  )*a^(x%1);
}