Added 'when' as a shortcut around only_if.

This commit is contained in:
Michael DeHaan 2012-10-27 17:55:35 -04:00
parent a768e9a9ff
commit 21258dcc66
3 changed files with 143 additions and 31 deletions

View file

@ -1,47 +1,50 @@
---
# this is a demo of conditional executions using 'only_if', which can skip
# certain tasks on machines/platforms/etc where they do not apply.
# this is a demo of conditional executions using 'when' statements, which can skip
# certain tasks on machines/platforms/etc where they do not apply.
- hosts: all
user: root
vars:
favcolor: "red"
dog: "fido"
cat: "whiskers"
ssn: 8675309
# Below we're going to define some expressions.
# These are the types of when statemnets available
# when_set: $variable_name
# when_unset: $variable_name
# when_str: $x == "test"
# when_int: $y > 2
# when_float: $z => 2.3
#
# Not only can we assign variables for reuse, but we can also assign conditional
# expressions. By keeping these in 'vars', the task section remains
# extraordinarily clean, and not littered with programming language
# constructs -- so it's easily skimmed by humans.
#
# Remember to quote any variables if they are not numbers!
#
# Interesting fact: aside from the $variables, these expressions are actually
# tiny bits of Python. They are evaluated in the context of each host, so different
# steps can be skipped on different hosts! They should evaluate to either True
# or False
is_favcolor_blue: "'$favcolor' == 'blue'"
is_centos: "'$facter_operatingsystem' == 'CentOS'"
# NOTE:
#
# facter and ohai variables can be used in only_if statements too
# ex: "'$facter_operatingsystem' == 'CentOS'", which bubble up automatically
# from the managed machines
#
# this example won't do that though, as you might not have facter or ohai,
# but you get the idea...
# when using 'when', take care to make sure any variables given are surrounded by spaces
# as an example, $z>3 will not do what you want, use "$z > 3"
tasks:
- name: "do this if my favcolor is blue"
- name: "do this if my favcolor is blue, and my dog is named fido"
action: shell /bin/false
only_if: '$is_favcolor_blue'
when_string: $favcolor == 'blue' and $dog == 'fido'
- name: "do this if my favcolor is not blue"
- name: "do this if my favcolor is not blue, and my dog is named fido"
action: shell /bin/true
only_if: 'not ($is_favcolor_blue)'
when_string: $favcolor != 'blue' and $dog == 'fido'
- name: "do this if my SSN is over 9000"
action: shell /bin/true
when_integer: $ssn > 9000
- name: "do this if I have one of these SSNs"
action: shell /bin/true
when_integer: $ssn in [ 8675309, 8675310, 8675311 ]
- name: "do this if a variable named hippo is NOT defined"
action: shell /bin/true
when_unset: $hippo
- name: "do this if a variable named hippo is defined"
action: shell /bin/true
when_set: $hippo

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@ -0,0 +1,47 @@
---
# this is a demo of conditional executions using 'only_if', which can skip
# certain tasks on machines/platforms/etc where they do not apply. This is
# the more 'raw' version of the 'when' statement, most users will be able to
# use 'when' directly. 'only_if' is an older feature, and useful for when
# you need more advanced expression control.
- hosts: all
user: root
vars:
favcolor: "red"
ssn: 8675309
# Below we're going to define some expressions.
#
# Not only can we assign variables for reuse, but we can also assign conditional
# expressions. By keeping these in 'vars', the task section remains
# extraordinarily clean, and not littered with programming language
# constructs -- so it's easily skimmed by humans.
#
# Remember to quote any variables if they are not numbers!
#
# Interesting fact: aside from the $variables, these expressions are actually
# tiny bits of Python. They are evaluated in the context of each host, so different
# steps can be skipped on different hosts! They should evaluate to either True
# or False
is_favcolor_blue: "'$favcolor' == 'blue'"
is_centos: "'$facter_operatingsystem' == 'CentOS'"
# NOTE:
#
# setup module values, facter and ohai variables can be used in only_if statements too
# ex: "'$facter_operatingsystem' == 'CentOS'", which bubble up automatically
# from the managed machines. This example doesn't do that though.
tasks:
- name: "do this if my favcolor is blue"
action: shell /bin/false
only_if: '$is_favcolor_blue'
- name: "do this if my favcolor is not blue"
action: shell /bin/true
only_if: 'not ($is_favcolor_blue)'

View file

@ -22,7 +22,7 @@ from ansible import utils
class Task(object):
__slots__ = [
'name', 'action', 'only_if', 'async_seconds', 'async_poll_interval',
'name', 'action', 'only_if', 'when', 'async_seconds', 'async_poll_interval',
'notify', 'module_name', 'module_args', 'module_vars',
'play', 'notified_by', 'tags', 'register',
'delegate_to', 'first_available_file', 'ignore_errors',
@ -58,6 +58,11 @@ class Task(object):
else:
raise errors.AnsibleError("cannot find lookup plugin named %s for usage in with_%s" % (plugin_name, plugin_name))
elif x.startswith("when_"):
when_name = x.replace("when_","")
ds['when'] = "%s %s" % (when_name, ds[x])
ds.pop(x)
elif not x in Task.VALID_KEYS:
raise errors.AnsibleError("%s is not a legal parameter in an Ansible task or handler" % x)
@ -109,6 +114,8 @@ class Task(object):
# load various attributes
self.only_if = ds.get('only_if', 'True')
self.when = ds.get('when', None)
self.async_seconds = int(ds.get('async', 0)) # not async by default
self.async_poll_interval = int(ds.get('poll', 10)) # default poll = 10 seconds
self.notify = ds.get('notify', [])
@ -169,3 +176,58 @@ class Task(object):
self.tags.extend(apply_tags)
self.tags.extend(import_tags)
if self.when is not None:
if self.only_if != 'True':
raise errors.AnsibleError('when obsoletes only_if, only use one or the other')
self.only_if = self.compile_when_to_only_if(self.when)
def compile_when_to_only_if(self, expression):
'''
when is a shorthand for writing only_if conditionals. It requires less quoting
magic. only_if is retained for backwards compatibility.
'''
# when: set $variable
# when: unset $variable
# when: int $x >= $z and $y < 3
# when: int $x in $alist
# when: float $x > 2 and $y <= $z
# when: str $x != $y
if type(expression) not in [ str, unicode ]:
raise errors.AnsibleError("invalid usage of when_ operator: %s" % expression)
tokens = expression.split()
if len(tokens) < 2:
raise errors.AnsibleError("invalid usage of when_ operator: %s" % expression)
# when_set / when_unset
if tokens[0] in [ 'set', 'unset' ]:
if len(tokens) != 2:
raise errors.AnsibleError("usage: when: <set|unset> <$variableName>")
return "is_%s('%s')" % (tokens[0], tokens[1])
# when_integer / when_float / when_string
elif tokens[0] in [ 'integer', 'float', 'string' ]:
cast = None
if tokens[0] == 'integer':
cast = 'int'
elif tokens[0] == 'string':
cast = 'str'
elif tokens[0] == 'float':
cast = 'float'
tcopy = tokens[1:]
for (i,t) in enumerate(tokens[1:]):
if t.find("$") != -1:
# final variable substitution will happen in Runner code
tcopy[i] = "%s('%s')" % (cast, t)
else:
tcopy[i] = t
return " ".join(tcopy)
else:
raise errors.AnsibleError("invalid usage of when_ operator: %s" % expression)