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引擎国产化适配＆重构笔记

2022-06-24 09:36:00 【51CTO】

关于守护进程dup stderr问题；

      
      
       
       fd = open("/dev/null", O_RDWR);
       
       
 if (dup2(fd, STDIN_FILENO) == -1)
       
       
 if (dup2(fd, STDOUT_FILENO) == -1) 
       
       
    
       
       
#if xxx
       
       
     if (dup2(fd, STDERR_FILENO) == -1)
       
       
#else
       
       
    fd_log = open("pathlog", O_RDWR);
       
       
     if (dup2(fd_log, STDERR_FILENO) == -1)
       
       
#endif
       
       

       
       
if (fd > STDERR_FILENO) {
       
       
}
      
      
      
      
       
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将dup2(fd_log, stderr)还是dup2(fd_null, stderr);

也就是标准错误重定向到黑洞还是 log文件中

看下man dup的结果：dup2() makes newfd be the copy of oldfd, closing newfd first if necessary,

NAME

dup, dup2, dup3 - duplicate a file descriptor

SYNOPSIS

#include <unistd.h>

int dup(int oldfd);

int dup2(int oldfd, int newfd);

#define _GNU_SOURCE /* See feature_test_macros(7) */

#include <fcntl.h> /* Obtain O_* constant definitions */

#include <unistd.h>

int dup3(int oldfd, int newfd, int flags);

DESCRIPTION

These system calls create a copy of the file descriptor oldfd.

dup() uses the lowest-numbered unused descriptor for the new descriptor.

dup2() makes newfd be the copy of oldfd, closing newfd first if necessary, but note the following:

* If oldfd is not a valid file descriptor, then the call fails, and newfd is not closed.

* If oldfd is a valid file descriptor, and newfd has the same value as oldfd, then dup2() does nothing, and returns newfd.

After a successful return from one of these system calls, the old and new file descriptors may be used interchangeably. They refer to the same open file description (see open(2)) and thus share file offset and file status flags; for

example, if the file offset is modified by using lseek(2) on one of the descriptors, the offset is also changed for the other.

The two descriptors do not share file descriptor flags (the close-on-exec flag). The close-on-exec flag (FD_CLOEXEC; see fcntl(2)) for the duplicate descriptor is off.

dup3() is the same as dup2(), except that:

* The caller can force the close-on-exec flag to be set for the new file descriptor by specifying O_CLOEXEC in flags. See the description of the same flag in open(2) for reasons why this may be useful.

* If oldfd equals newfd, then dup3() fails with the error EINVAL.

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引擎注意事项:

进程名称
cpu绑定
进程资源设置(file_limit core_limit signal_mask)
时间戳的设置 (多进程/多线程 )volatile 防止优化
守护进程
信号处理以及 coredump处理
log设置
参数处理
进程唯一实例
去掉root 特权
进程间通信-socketpair pipe unix-socket 共享内存（mmap munmap以及shmget shmat shmctl) 共享内存blog pipe-unix blog

网络中间件：

采用 libevent libuv 再次封装还是结合自己业务再次编写？

协议解析：

打包问题：

fakeroot权限：使用fakeroot模拟root权限执行程序，在打包的时候，包里面的文件所有者必须是root。必须以root 权限来执行打包命令，但是应该避免在制作包的时候使用root权限。为了解决这个矛盾，fakeroot被开发出来了。在fakeroot环境中，操作文件就像使用root操作文件一样，但是，实际上系统中文件的权限还是原来的权限。