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This module contains Fab's `main` method plus related subroutines.
`main` is executed as the command line ``fab`` program and takes care of
parsing options and commands, loading the user settings file, loading a
fabfile, and executing the commands given.
The other callables defined in this module are internal only. Anything useful
to individuals leveraging Fabric as a library, should be kept elsewhere.
from collections import defaultdict
from operator import add, isMappingType
from optparse import OptionParser
import os
import sys
import types
from fabric import api, state # For checking callables against the API, & easy mocking
from fabric.contrib import console, files, project # Ditto
from import denormalize, interpret_host_string, disconnect_all
from fabric.state import commands, connections, env_options
from fabric.tasks import Task
from fabric.utils import abort, indent
# One-time calculation of "all internal callables" to avoid doing this on every
# check of a given fabfile callable (in is_classic_task()).
_modules = [api, project, files, console]
_internals = reduce(lambda x, y: x + filter(callable, vars(y).values()),
# Module recursion cache
class _ModuleCache(object):
Set-like object operating on modules and storing __name__s internally.
def __init__(self):
self.cache = set()
def __contains__(self, value):
return value.__name__ in self.cache
def add(self, value):
return self.cache.add(value.__name__)
def clear(self):
return self.cache.clear()
_seen = _ModuleCache()
def load_settings(path):
Take given file path and return dictionary of any key=value pairs found.
Usage docs are in docs/usage/fab.rst, in "Settings files."
if os.path.exists(path):
comments = lambda s: s and not s.startswith("#")
settings = filter(comments, open(path, 'r'))
return dict((k.strip(), v.strip()) for k, _, v in
[s.partition('=') for s in settings])
# Handle nonexistent or empty settings file
return {}
def _is_package(path):
Is the given path a Python package?
return (
and os.path.exists(os.path.join(path, ''))
def find_fabfile():
Attempt to locate a fabfile, either explicitly or by searching parent dirs.
Usage docs are in docs/usage/fabfiles.rst, in "Fabfile discovery."
# Obtain env value
names = [state.env.fabfile]
# Create .py version if necessary
if not names[0].endswith('.py'):
names += [names[0] + '.py']
# Does the name contain path elements?
if os.path.dirname(names[0]):
# If so, expand home-directory markers and test for existence
for name in names:
expanded = os.path.expanduser(name)
if os.path.exists(expanded):
if name.endswith('.py') or _is_package(expanded):
return os.path.abspath(expanded)
# Otherwise, start in cwd and work downwards towards filesystem root
path = '.'
# Stop before falling off root of filesystem (should be platform
# agnostic)
while os.path.split(os.path.abspath(path))[1]:
for name in names:
joined = os.path.join(path, name)
if os.path.exists(joined):
if name.endswith('.py') or _is_package(joined):
return os.path.abspath(joined)
path = os.path.join('..', path)
# Implicit 'return None' if nothing was found
def is_classic_task(tup):
Takes (name, object) tuple, returns True if it's a non-Fab public callable.
name, func = tup
return (
and (func not in _internals)
and not name.startswith('_')
def load_fabfile(path, importer=None):
Import given fabfile path and return (docstring, callables).
Specifically, the fabfile's ``__doc__`` attribute (a string) and a
dictionary of ``{'name': callable}`` containing all callables which pass
the "is a Fabric task" test.
if importer is None:
importer = __import__
# Get directory and fabfile name
directory, fabfile = os.path.split(path)
# If the directory isn't in the PYTHONPATH, add it so our import will work
added_to_path = False
index = None
if directory not in sys.path:
sys.path.insert(0, directory)
added_to_path = True
# If the directory IS in the PYTHONPATH, move it to the front temporarily,
# otherwise other fabfiles -- like Fabric's own -- may scoop the intended
# one.
i = sys.path.index(directory)
if i != 0:
# Store index for later restoration
index = i
# Add to front, then remove from original position
sys.path.insert(0, directory)
del sys.path[i + 1]
# Perform the import (trimming off the .py)
imported = importer(os.path.splitext(fabfile)[0])
# Remove directory from path if we added it ourselves (just to be neat)
if added_to_path:
del sys.path[0]
# Put back in original index if we moved it
if index is not None:
sys.path.insert(index + 1, directory)
del sys.path[0]
# Actually load tasks
docstring, new_style, classic, default = load_tasks_from_module(imported)
tasks = new_style if state.env.new_style_tasks else classic
# Clean up after ourselves
return docstring, tasks, default
def load_tasks_from_module(imported):
Handles loading all of the tasks for a given `imported` module
# Obey the use of <module>.__all__ if it is present
imported_vars = vars(imported)
if "__all__" in imported_vars:
imported_vars = [(name, imported_vars[name]) for name in \
imported_vars if name in imported_vars["__all__"]]
imported_vars = imported_vars.items()
# Return a two-tuple value. First is the documentation, second is a
# dictionary of callables only (and don't include Fab operations or
# underscored callables)
new_style, classic, default = extract_tasks(imported_vars)
return imported.__doc__, new_style, classic, default
# For attribute tomfoolery
class _Dict(dict):
def extract_tasks(imported_vars):
Handle extracting tasks from a given list of variables
new_style_tasks = _Dict()
classic_tasks = {}
default_task = None
if 'new_style_tasks' not in state.env:
state.env.new_style_tasks = False
for tup in imported_vars:
name, obj = tup
if is_task_object(obj):
state.env.new_style_tasks = True
# Honor
new_style_tasks[] = obj
# Handle aliasing
if obj.aliases is not None:
for alias in obj.aliases:
new_style_tasks[alias] = obj
# Handle defaults
if obj.is_default:
default_task = obj
elif is_classic_task(tup):
classic_tasks[name] = obj
elif is_task_module(obj):
docs, newstyle, classic, default = load_tasks_from_module(obj)
for task_name, task in newstyle.items():
if name not in new_style_tasks:
new_style_tasks[name] = _Dict()
new_style_tasks[name][task_name] = task
if default is not None:
new_style_tasks[name].default = default
return new_style_tasks, classic_tasks, default_task
def is_task_module(a):
Determine if the provided value is a task module
#return (type(a) is types.ModuleType and
# any(map(is_task_object, vars(a).values())))
if type(a) is types.ModuleType and a not in _seen:
# Flag module as seen
# Signal that we need to check it out
return True
def is_task_object(a):
Determine if the provided value is a ``Task`` object.
This returning True signals that all tasks within the fabfile
module must be Task objects.
return isinstance(a, Task) and a.use_task_objects
def parse_options():
Handle command-line options with optparse.OptionParser.
Return list of arguments, largely for use in `parse_arguments`.
# Initialize
parser = OptionParser(usage="fab [options] <command>[:arg1,arg2=val2,host=foo,hosts='h1;h2',...] ...")
# Define options that don't become `env` vars (typically ones which cause
# Fabric to do something other than its normal execution, such as
# --version)
# Version number (optparse gives you --version but we have to do it
# ourselves to get -V too. sigh)
parser.add_option('-V', '--version',
help="show program's version number and exit"
# List Fab commands found in loaded fabfiles/source files
parser.add_option('-l', '--list',
help="print list of possible commands and exit"
# Like --list, but text processing friendly
help="alias for -F short --list"
# Control behavior of --list
LIST_FORMAT_OPTIONS = ('short', 'normal', 'nested')
parser.add_option('-F', '--list-format',
help="formats --list, choices: %s" % ", ".join(LIST_FORMAT_OPTIONS)
# Display info about a specific command
parser.add_option('-d', '--display',
help="print detailed info about a given command and exit"
# Add in options which are also destined to show up as `env` vars.
for option in env_options:
# Finalize
# Return three-tuple of parser + the output from parse_args (opt obj, args)
opts, args = parser.parse_args()
return parser, opts, args
def _is_task(name, value):
Is the object a task as opposed to e.g. a dict or int?
return is_classic_task((name, value)) or is_task_object(value)
def _sift_tasks(mapping):
tasks, collections = [], []
for name, value in mapping.iteritems():
if _is_task(name, value):
elif isMappingType(value):
tasks = sorted(tasks)
collections = sorted(collections)
return tasks, collections
def _task_names(mapping):
Flatten & sort task names in a breadth-first fashion.
Tasks are always listed before submodules at the same level, but within
those two groups, sorting is alphabetical.
tasks, collections = _sift_tasks(mapping)
for collection in collections:
module = mapping[collection]
if hasattr(module, 'default'):
join = lambda x: ".".join((collection, x))
tasks.extend(map(join, _task_names(module)))
return tasks
def _crawl(name, mapping):
``name`` of ``'a.b.c'`` => ``mapping['a']['b']['c']``
key, _, rest = name.partition('.')
value = mapping[key]
if not rest:
return value
return _crawl(rest, value)
def crawl(name, mapping):
result = _crawl(name, mapping)
# Handle default tasks
if isinstance(result, _Dict) and getattr(result, 'default', False):
result = result.default
return result
except (KeyError, TypeError):
return None
def _print_docstring(docstrings, name):
if not docstrings:
return False
docstring = crawl(name, state.commands).__doc__
if type(docstring) in types.StringTypes:
return docstring
def _normal_list(docstrings=True):
result = []
task_names = _task_names(state.commands)
# Want separator between name, description to be straight col
max_len = reduce(lambda a, b: max(a, len(b)), task_names, 0)
sep = ' '
trail = '...'
for name in task_names:
output = None
docstring = _print_docstring(docstrings, name)
if docstring:
lines = filter(None, docstring.splitlines())
first_line = lines[0].strip()
# Truncate it if it's longer than N chars
size = 75 - (max_len + len(sep) + len(trail))
if len(first_line) > size:
first_line = first_line[:size] + trail
output = name.ljust(max_len) + sep + first_line
# Or nothing (so just the name)
output = name
return result
def _nested_list(mapping, level=1):
result = []
tasks, collections = _sift_tasks(mapping)
# Tasks come first
result.extend(map(lambda x: indent(x, spaces=level * 4), tasks))
for collection in collections:
module = mapping[collection]
# Section/module "header"
result.append(indent(collection + ":", spaces=level * 4))
# Recurse
result.extend(_nested_list(module, level + 1))
return result
COMMANDS_HEADER = "Available commands"
NESTED_REMINDER = " (remember to call as module.[...].task)"
def list_commands(docstring, format_):
Print all found commands/tasks, then exit. Invoked with ``-l/--list.``
If ``docstring`` is non-empty, it will be printed before the task list.
``format_`` should conform to the options specified in
``LIST_FORMAT_OPTIONS``, e.g. ``"short"``, ``"normal"``.
# Short-circuit with simple short output
if format_ == "short":
return _task_names(state.commands)
# Otherwise, handle more verbose modes
result = []
# Docstring at top, if applicable
if docstring:
trailer = "\n" if not docstring.endswith("\n") else ""
result.append(docstring + trailer)
if format_ == "nested":
result.append(header + ":\n")
c = _normal_list() if format_ == "normal" else _nested_list(state.commands)
return result
def display_command(name):
Print command function's docstring, then exit. Invoked with -d/--display.
# Sanity check
command = crawl(name, state.commands)
if command is None:
msg = "Task '%s' does not appear to exist. Valid task names:\n%s"
abort(msg % (name, "\n".join(_normal_list(False))))
# Print out nicely presented docstring if found
if command.__doc__:
print("Displaying detailed information for task '%s':" % name)
print(indent(command.__doc__, strip=True))
# Or print notice if not
print("No detailed information available for task '%s':" % name)
def _escape_split(sep, argstr):
Allows for escaping of the separator: e.g. task:arg='foo\, bar'
It should be noted that the way bash et. al. do command line parsing, those
single quotes are required.
escaped_sep = r'\%s' % sep
if escaped_sep not in argstr:
return argstr.split(sep)
before, _, after = argstr.partition(escaped_sep)
startlist = before.split(sep) # a regular split is fine here
unfinished = startlist[-1]
startlist = startlist[:-1]
# recurse because there may be more escaped separators
endlist = _escape_split(sep, after)
# finish building the escaped value. we use endlist[0] becaue the first
# part of the string sent in recursion is the rest of the escaped value.
unfinished += sep + endlist[0]
return startlist + [unfinished] + endlist[1:] # put together all the parts
def parse_arguments(arguments):
Parse string list into list of tuples: command, args, kwargs, hosts, roles.
See docs/usage/fab.rst, section on "per-task arguments" for details.
cmds = []
for cmd in arguments:
args = []
kwargs = {}
hosts = []
roles = []
exclude_hosts = []
if ':' in cmd:
cmd, argstr = cmd.split(':', 1)
for pair in _escape_split(',', argstr):
k, _, v = pair.partition('=')
if _:
# Catch, interpret host/hosts/role/roles/exclude_hosts
# kwargs
if k in ['host', 'hosts', 'role', 'roles', 'exclude_hosts']:
if k == 'host':
hosts = [v.strip()]
elif k == 'hosts':
hosts = [x.strip() for x in v.split(';')]
elif k == 'role':
roles = [v.strip()]
elif k == 'roles':
roles = [x.strip() for x in v.split(';')]
elif k == 'exclude_hosts':
exclude_hosts = [x.strip() for x in v.split(';')]
# Otherwise, record as usual
kwargs[k] = v
cmds.append((cmd, args, kwargs, hosts, roles, exclude_hosts))
return cmds
def parse_remainder(arguments):
Merge list of "remainder arguments" into a single command string.
return ' '.join(arguments)
def _merge(hosts, roles, exclude=[]):
Merge given host and role lists into one list of deduped hosts.
# Abort if any roles don't exist
bad_roles = [x for x in roles if x not in state.env.roledefs]
if bad_roles:
abort("The following specified roles do not exist:\n%s" % (
# Look up roles, turn into flat list of hosts
role_hosts = []
for role in roles:
value = state.env.roledefs[role]
# Handle "lazy" roles (callables)
if callable(value):
value = value()
role_hosts += value
# Return deduped combo of hosts and role_hosts, preserving order within
# them (vs using set(), which may lose ordering) and skipping hosts to be
# excluded.
cleaned_hosts = _clean_hosts(list(hosts) + list(role_hosts))
all_hosts = []
for host in cleaned_hosts:
if host not in all_hosts and host not in exclude:
return all_hosts
def _clean_hosts(host_list):
Clean host strings to ensure no trailing whitespace, etc.
return [host.strip() for host in host_list]
def get_hosts(command, cli_hosts, cli_roles, cli_exclude_hosts):
Return the host list the given command should be using.
See :ref:`execution-model` for detailed documentation on how host lists are
# Command line per-command takes precedence over anything else.
if cli_hosts or cli_roles:
return _merge(cli_hosts, cli_roles, cli_exclude_hosts)
# Decorator-specific hosts/roles go next
func_hosts = getattr(command, 'hosts', [])
func_roles = getattr(command, 'roles', [])
if func_hosts or func_roles:
return _merge(func_hosts, func_roles, cli_exclude_hosts)
# Finally, the env is checked (which might contain globally set lists from
# the CLI or from module-level code). This will be the empty list if these
# have not been set -- which is fine, this method should return an empty
# list if no hosts have been set anywhere.
return _merge(state.env['hosts'], state.env['roles'], state.env['exclude_hosts'])
def update_output_levels(show, hide):
Update state.output values as per given comma-separated list of key names.
For example, ``update_output_levels(show='debug,warnings')`` is
functionally equivalent to ``state.output['debug'] = True ;
state.output['warnings'] = True``. Conversely, anything given to ``hide``
sets the values to ``False``.
if show:
for key in show.split(','):
state.output[key] = True
if hide:
for key in hide.split(','):
state.output[key] = False
def _run_task(task, args, kwargs):
# First, try class-based tasks
if hasattr(task, 'run') and callable(
return*args, **kwargs)
# Fallback to callable behavior
return task(*args, **kwargs)
def main():
Main command-line execution loop.
# Parse command line options
parser, options, arguments = parse_options()
# Handle regular args vs -- args
arguments = parser.largs
remainder_arguments = parser.rargs
# Update env with any overridden option values
# NOTE: This needs to remain the first thing that occurs
# post-parsing, since so many things hinge on the values in env.
for option in env_options:
state.env[option.dest] = getattr(options, option.dest)
# Handle --hosts, --roles, --exclude-hosts (comma separated string =>
# list)
for key in ['hosts', 'roles', 'exclude_hosts']:
if key in state.env and isinstance(state.env[key], basestring):
state.env[key] = state.env[key].split(',')
# Handle output control level show/hide
update_output_levels(, hide=options.hide)
# Handle version number option
if options.show_version:
print("Fabric %s" % state.env.version)
# Load settings from user settings file, into shared env dict.
# Find local fabfile path or abort
fabfile = find_fabfile()
if not fabfile and not remainder_arguments:
abort("""Couldn't find any fabfiles!
Remember that -f can be used to specify fabfile path, and use -h for help.""")
# Store absolute path to fabfile in case anyone needs it
state.env.real_fabfile = fabfile
# Load fabfile (which calls its module-level code, including
# tweaks to env values) and put its commands in the shared commands
# dict
if fabfile:
docstring, callables, default = load_fabfile(fabfile)
# Handle case where we were called bare, i.e. just "fab", and print
# a help message.
actions = (options.list_commands, options.shortlist, options.display,
arguments, remainder_arguments, default)
if not any(actions):
# Abort if no commands found
if not state.commands and not remainder_arguments:
abort("Fabfile didn't contain any commands!")
# Now that we're settled on a fabfile, inform user.
if state.output.debug:
if fabfile:
print("Using fabfile '%s'" % fabfile)
print("No fabfile loaded -- remainder command only")
# Shortlist is now just an alias for the "short" list format;
# it overrides use of --list-format if somebody were to specify both
if options.shortlist:
options.list_format = 'short'
options.list_commands = True
# List available commands
if options.list_commands:
print("\n".join(list_commands(docstring, options.list_format)))
# Handle show (command-specific help) option
if options.display:
# If user didn't specify any commands to run, show help
if not (arguments or remainder_arguments or default):
sys.exit(0) # Or should it exit with error (1)?
# Parse arguments into commands to run (plus args/kwargs/hosts)
commands_to_run = parse_arguments(arguments)
# Parse remainders into a faux "command" to execute
remainder_command = parse_remainder(remainder_arguments)
# Figure out if any specified task names are invalid
unknown_commands = []
for tup in commands_to_run:
if crawl(tup[0], state.commands) is None:
# Abort if any unknown commands were specified
if unknown_commands:
abort("Command(s) not found:\n%s" \
% indent(unknown_commands))
# Generate remainder command and insert into commands, commands_to_run
if remainder_command:
r = '<remainder>'
state.commands[r] = lambda:
commands_to_run.append((r, [], {}, [], [], []))
# Ditto for a default, if found
if not commands_to_run and default:
commands_to_run.append((, [], {}, [], [], []))
if state.output.debug:
names = ", ".join(x[0] for x in commands_to_run)
print("Commands to run: %s" % names)
# At this point all commands must exist, so execute them in order.
for name, args, kwargs, cli_hosts, cli_roles, cli_exclude_hosts in commands_to_run:
# Get callable by itself
task = crawl(name, state.commands)
# Set current task name (used for some error messages)
state.env.command = name
# Set host list (also copy to env)
state.env.all_hosts = hosts = get_hosts(
task, cli_hosts, cli_roles, cli_exclude_hosts)
# If hosts found, execute the function on each host in turn
for host in hosts:
# Preserve user
prev_user = state.env.user
# Split host string and apply to env dict
username, hostname, port = interpret_host_string(host)
# Log to stdout
if state.output.running and not hasattr(task, 'return_value'):
print("[%s] Executing task '%s'" % (host, name))
# Actually run command
_run_task(task, args, kwargs)
# Put old user back
state.env.user = prev_user
# If no hosts found, assume local-only and run once
if not hosts:
_run_task(task, args, kwargs)
# If we got here, no errors occurred, so print a final note.
if state.output.status:
except SystemExit:
# a number of internal functions might raise this one.
except KeyboardInterrupt:
if state.output.status:
print >> sys.stderr, "\nStopped."
# we might leave stale threads if we don't explicitly exit()
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