Source code for modules.utils

"""
Utility functions

(e.g. Determining the remote system OS)

You should ALWAYS include this module in your deployment.  It contains functions that are used by other modules.
"""
from fabric.context_managers import *
from fabric.operations import *
from fabric.contrib import files
from fabric.api import env
import sys

def what_os():
    """
    Returns a string indicating the Host OS.  Currently
    Only supports 'redhat' and 'ubuntu'
    """
    with settings(
        hide('warnings', 'running', 'stdout', 'stderr'),
        warn_only=True
    ):
        print 'Testing operating system type...'
        if(files.exists('/etc/lsb-release',verbose=True) and files.contains(text='DISTRIB_ID=Ubuntu', filename='/etc/lsb-release')):
            env.os = 'ubuntu'
            print 'Found lsb-release and contains "DISTRIB_ID=Ubuntu", this is an Ubuntu System.'
        elif(files.exists('/etc/redhat-release',verbose=True)):
            env.os = 'redhat'
            print 'Found /etc/redhat-release, this is a RedHat system.'
        else:
            print 'System OS not recognized! Aborting.'
            exit()
        return env.os


def try_import(module_name):
    """
    Import and return *module_name*.

    >>> try_import("csv") # doctest: +ELLIPSIS
    <module 'csv' from '...'>

    Unlike the standard try/except approach to optional imports, inspect
    the stack to avoid catching ImportErrors raised from **within** the
    module. Only return None if *module_name* itself cannot be imported.

    >>> try_import("spam.spam.spam") is None
    True
    """

    try:
        __import__(module_name)
        return sys.modules[module_name]

    except ImportError:

        # extract a backtrace, so we can find out where the exception
        # was raised from. if there is a NEXT frame, it means that the
        # import statement succeeded, but an ImportError was raised from
        # *within* the imported module. we must allow this error to
        # propagate, to avoid silently masking it.
        traceback = sys.exc_info()[2]
        if traceback.tb_next:
            raise

        # else, the exception was raised from this scope. *module_name*
        # couldn't be imported, which is fine, since allowing that is
        # the purpose of this function.
        return None


def bootstrap(deploy_level='staging'):
    """
    Does nothing in this module.
    """
    pass


def develop(deploy_level='staging'):
    """
    Does nothing in this module.
    """
    pass


def stop(deploy_level='staging'):
    """
    Does nothing in this module.
    """
    pass


def start(deploy_level='staging'):
    """
    Does nothing in this module.
    """
    pass