Hello dev list,
Many thanks for your efforts on ansible, very useful tool.
Have a new feature I’d like to work on that would like to float by you for comments and if it sounds like a good feature to implement before submitting a PR.
In short, would like to add the ability to use the ParallelSSH client library to run SSH commands via ansible. The library uses paramiko and gevent to provide an asynchronous parallel SSH client python library.
This would greatly benefit ansible when running multiple commands in parallel. The current parallel implementation uses multiprocessing and increases system load on the host running ansible linearly as # of threads increases.
Benefits of using the ParallelSSH library:
- Asynchronous parallel SSH commands
- No system load induced on the host running it, regardless of # of parallel connections
- Persistent connections by default, one connection per host
- Stdout/stderr and exit code retrieval built in
- Configurable parallelism level
- Native proxying/tunneling support, also asynchronous. No ProxyCommand, no subprocess per tunnel
- Native SFTP support
- Pure python library, no cmd line tools used
- No openssh or other ssh cmd line tool dependencies
- Posix systems and windows compatible
Effect on ansible:
- Uses gevent’s monkey patching to make paramiko asynchronous. Monkey patching of subprocess in particular will also affect ansible’s use of subprocess, though it should be compatible.
- gevent library would be a new requirement for ansible
Is this of interest? If so, where do you think it should go, a new connection type perhaps or overriding existing paramiko implementation? I would think overriding paramiko implementation to use the library would make most sense. As the library itself uses paramiko it is already compatible.
As a bonus if use of paramiko is overridden, most of the code in paramiko_ssh.py can go as the client implementation lives entirely in the library.
Would argue that the subprocess use of the ssh binary in ssh.py should be overridden as well, at least for parallel commands, but given backwards compatibility requirements doubt that would be feasible.
Comments appreciated, thanks.
- Dan
