/ DevOps Tools

A simple, Pythonic tool for remote execution and deployment

A simple, Pythonic tool for remote execution and deployment

Fabric

Fabric is a high level Python (2.7, 3.4+) library designed to execute shell commands remotely over SSH, yielding useful Python objects in return::

>>> from fabric import Connection
>>> result = Connection('web1.example.com').run('uname -s')
>>> msg = "Ran {.command!r} on {.connection.host}, got stdout:\n{.stdout}"
>>> print(msg.format(result))
Ran "uname -s" on web1.example.com, got this stdout:
Linux

It builds on top of Invoke_ (subprocess command execution and command-line features) and Paramiko_ (SSH protocol implementation), extending their APIs to complement one another and provide additional functionality

How is it used?

Core use cases for Fabric include (but are not limited to):

  • Single commands on individual hosts::

    >>> result = Connection('web1').run('hostname')
    web1
    >>> result
    <Result cmd='hostname' exited=0>
    
  • Single commands across multiple hosts (via varying methodologies: serial,
    parallel, etc)::

    >>> result = SerialGroup('web1', 'web2').run('hostname')
    web1
    web2
    >>> result
    {<Connection host=web1>: <Result cmd='whoami' exited=0>, ...}
    
  • Python code blocks (functions/methods) targeted at individual connections::

    >>> def disk_free(c):
    >>>     uname = c.run('uname -s', hide=True)
    >>>     if 'Linux' in uname:
    ...         command = "df -h / | tail -n1 | awk '{print $5}'"
    ...         return c.run(command, hide=True).stdout.strip()
    ...     err = "No idea how to get disk space on {}!".format(uname)
    ...     raise Exit(err)
    ...
    >>> disk_free(Connection('web1'))
    '33%'
    
  • Python code blocks on multiple hosts::

    >>> def disk_free(c):
    ...     # same as above!
    ...
    >>> {c: disk_free(c) for c in SerialGroup('web1', 'web2', 'db1')}
    {<Connection host=web1>: '33%', <Connection host=web2>: '17%', ...}
    

In addition to these library-oriented use cases, Fabric makes it easy to integrate with Invoke's command-line task functionality, invoking via a fab binary stub:

  • Python functions, methods or entire objects can be used as CLI-addressable
    tasks, e.g. fab deploy;
  • Tasks may indicate other tasks to be run before or after they themselves execute (pre- or post-tasks);
  • Tasks are parameterized via regular GNU-style arguments, e.g. fab deploy --env=prod -d;
  • Multiple tasks may be given in a single CLI session, e.g. fab build deploy;
  • Much more - all other Invoke functionality is supported - see its documentation <http://docs.pyinvoke.org>_ for details.

I'm a user of Fabric 1, how do I upgrade?

We've packaged modern Fabric in a manner that allows installation alongside Fabric 1, so you can upgrade at whatever pace your use case requires. There are multiple possible approaches -- see our detailed upgrade documentation <http://docs.fabfile.org/en/latest/upgrading.html>_ for details.

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