Execute remote commands or processes.
A very simplistic remote-command-executor using ssh and Python in the remote end.
All the heavy lifting is done by execnet, while this minimal API provides the bare minimum to handle easy logging and connections from the remote end.
remoto is a bit opinionated as it was conceived to replace helpers and remote utilities for ceph-deploy a tool to run remote commands to configure and setup the distributed file system Ceph.
The usage aims to be extremely straightforward, with a very minimal set of helpers and utilities for remote processes and logging output.
The most basic example will use the run helper to execute a command on the remote end. It does require a logging object, which needs to be one that, at the very least, has both error and debug. Those are called for stderr and stdout respectively.
This is how it would look with a basic logger passed in:
>>> import logging >>> logging.basicConfig(level=logging.DEBUG) >>> logger = logging.getLogger('hostname') >>> conn = remoto.Connection('hostname', logger=logger) >>> run(conn, ['ls', '-a']) INFO:hostname:Running command: ls -a DEBUG:hostname:. DEBUG:hostname:.. DEBUG:hostname:.bash_history DEBUG:hostname:.bash_logout DEBUG:hostname:.bash_profile DEBUG:hostname:.bashrc DEBUG:hostname:.gem DEBUG:hostname:.lesshst DEBUG:hostname:.pki DEBUG:hostname:.puppet DEBUG:hostname:.ssh DEBUG:hostname:.vim DEBUG:hostname:.viminfo
The run helper will display the stderr and stdout as ERROR and DEBUG respectively.
For other types of usage (like checking exit status codes, or raising upon them) remoto does provide them too.
Calling remote commands can be done in a few different ways. The most simple one is with process.run:
>>> from remoto.process import run >>> from remoto import Connection >>> logger = logging.getLogger('myhost') >>> conn = Connection('myhost', logger=logger) >>> run(conn, ['whoami']) INFO:myhost:Running command: whoami DEBUG:myhost:root
Note however, that you are not capturing results or information from the remote end. The intention here is only to be able to run a command and log its output. It is a fire and forget call.
This callable, allows the caller to deal with the stderr, stdout and exit code. It returns it in a 3 item tuple:
>>> from remoto.process import check >>> check(conn, ['ls', '/nonexistent/path']) (, ['ls: cannot access /nonexistent/path: No such file or directory'], 2)
Note that the stdout and stderr items are returned as lists with the \n characters removed.
This is useful if you need to process the information back locally, as opposed to just firing and forgetting (while logging, like process.run).
To execute remote functions (ideally) you would need to define them in a module and add the following to the end of that module:
if __name__ == '__channelexec__': for item in channel: channel.send(eval(item))
If you had a function in a module named foo that looks like this:
import os def listdir(path): return os.listdir(path)
To be able to execute that listdir function remotely you would need to pass the module to the connection object and then call that function:
>>> import foo >>> conn = Connection('hostname') >>> remote_foo = conn.import_module(foo) >>> remote_foo.listdir('.') ['.bash_logout', '.profile', '.veewee_version', '.lesshst', 'python', '.vbox_version', 'ceph', '.cache', '.ssh']
Note that functions to be executed remotely cannot accept objects as arguments, just normal Python data structures, like tuples, lists and dictionaries. Also safe to use are ints and strings.
Automatic detection for remote connections
There is automatic detection for the need to connect remotely (via SSH) or not that it is infered by the hostname of the current host (vs. the host that is connecting to).
If the local host has the same as the remote hostname, a local connection (via
Popen) will be opened and that will be used instead of
ssh, and avoiding
the issues of being able to ssh into the same host.
Automatic detection for using
This magical detection can be enabled by using the
detect_sudo flag in the
Connection class. It is disabled by default.
When enabled, it will prefix any command with
sudo. This is useful for
libraries that need super user permissions and want to avoid passing
everywhere, which can be non-trivial if dealing with
root users that are
connecting via SSH.