ssh阻塞与非阻塞mod的区别

Question

这个问题听起来很愚蠢，因为每个使用SSH库的开发人员都应该问自己这个问题（？）。但是我真的找不到阻塞和非阻塞之间的区别。。。在

我是说好吧。。。一个阻塞直到它收到答案，另一个发送查询并立即返回，然后你自己检查回复缓冲区。。。我有那个角色。在

但是为什么要用一个而不是另一个呢？我找不到答案。。。 是关于表演吗？如果有区别，为什么？在

提前感谢您对这些问题的回答。在

——编辑：忘了下面的“奖金问题”，我终于编好了非阻塞模式，也遇到了同样的问题，一定是libssh2的问题。所以我还是没有得到非阻塞模式的附加值。。。---在

Bonus question:
I'm not really sure could this difference explain something I'm experiencing?
I have a python script which connects to many hosts to run several commands.
It was using paramiko library in non-blocking mode. Paramiko is pure python and really slow for establishing ssh connections to many hosts...
I'm changing it for pylibssh2 which is python bindings for the C library libssh2. Since I didn't get the difference, I started to code in blocking mode.

Results:
- libss2 is much faster than paramiko (connection to 230 hosts in parallel in 4s instead of 1m30s)
- For running commands successively, libssh2 is also faster.
- When I run commands through ssh from several parallel threads, the code with libssh2 in blocking mode becomes slowlier than paramiko in non-blocking mode.
- I also noticed that the CPU consumption is very low compared with previous version. I guess part of this is related to C vs python but it seems than beyond the SSH API, my script itself performs less actions. Are threads blocking each other when sending commands through SSH in blocking mode?

Answer 1

原因是，如果你想同时做两件事，比如从其他网络连接读取，和你的SSH会话，你有两个选择：

• 使用阻塞API，并使用两个线程或进程，这样您就可以同时执行它们

• 使用非阻塞API，这样同一个线程就可以同时完成这两个任务

后一种方法称为Asynchronous I/O。例如，请参见广泛使用它的twisted。在