The Gatekeeper, or a project gating system
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# (c) 2012-2014, Michael DeHaan <>
# This file is part of Ansible
# Ansible is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# Ansible is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# GNU General Public License for more details.
# You should have received a copy of the GNU General Public License
# along with Ansible. If not, see <>.
# flake8: noqa
# This is temporarily copied into Zuul from Ansible to work around a
# bug related to log streaming, story 2002528.
# Make coding more python3-ish
from __future__ import (absolute_import, division, print_function)
__metaclass__ = type
strategy: linear
short_description: Executes tasks in a linear fashion
- Task execution is in lockstep per host batch as defined by C(serial) (default all).
Up to the fork limit of hosts will execute each task at the same time and then
the next series of hosts until the batch is done, before going on to the next task.
version_added: "2.0"
- This was the default Ansible behaviour before 'strategy plugins' were introduced in 2.0.
author: Ansible Core Team
from ansible.errors import AnsibleError, AnsibleAssertionError
from ansible.executor.play_iterator import PlayIterator
from ansible.module_utils.six import iteritems
from ansible.module_utils._text import to_text
from ansible.playbook.block import Block
from ansible.playbook.included_file import IncludedFile
from ansible.playbook.task import Task
from ansible.plugins.loader import action_loader
from ansible.plugins.strategy import StrategyBase
from ansible.template import Templar
from __main__ import display
except ImportError:
from ansible.utils.display import Display
display = Display()
class StrategyModule(StrategyBase):
noop_task = None
def _replace_with_noop(self, target):
if self.noop_task is None:
raise AnsibleAssertionError('strategy.linear.StrategyModule.noop_task is None, need Task()')
result = []
for el in target:
if isinstance(el, Task):
elif isinstance(el, Block):
result.append(self._create_noop_block_from(el, el._parent))
return result
def _create_noop_block_from(self, original_block, parent):
noop_block = Block(parent_block=parent)
noop_block.block = self._replace_with_noop(original_block.block)
noop_block.always = self._replace_with_noop(original_block.always)
noop_block.rescue = self._replace_with_noop(original_block.rescue)
return noop_block
def _prepare_and_create_noop_block_from(self, original_block, parent, iterator):
self.noop_task = Task()
self.noop_task.action = 'meta'
self.noop_task.args['_raw_params'] = 'noop'
return self._create_noop_block_from(original_block, parent)
def _get_next_task_lockstep(self, hosts, iterator):
Returns a list of (host, task) tuples, where the task may
be a noop task to keep the iterator in lock step across
all hosts.
noop_task = Task()
noop_task.action = 'meta'
noop_task.args['_raw_params'] = 'noop'
host_tasks = {}
display.debug("building list of next tasks for hosts")
for host in hosts:
host_tasks[] = iterator.get_next_task_for_host(host, peek=True)
display.debug("done building task lists")
num_setups = 0
num_tasks = 0
num_rescue = 0
num_always = 0
display.debug("counting tasks in each state of execution")
host_tasks_to_run = [(host, state_task)
for host, state_task in iteritems(host_tasks)
if state_task and state_task[1]]
if host_tasks_to_run:
lowest_cur_block = min(
(s.cur_block for h, (s, t) in host_tasks_to_run
if s.run_state != PlayIterator.ITERATING_COMPLETE))
except ValueError:
lowest_cur_block = None
# empty host_tasks_to_run will just run till the end of the function
# without ever touching lowest_cur_block
lowest_cur_block = None
for (k, v) in host_tasks_to_run:
(s, t) = v
if s.cur_block > lowest_cur_block:
# Not the current block, ignore it
if s.run_state == PlayIterator.ITERATING_SETUP:
num_setups += 1
elif s.run_state == PlayIterator.ITERATING_TASKS:
num_tasks += 1
elif s.run_state == PlayIterator.ITERATING_RESCUE:
num_rescue += 1
elif s.run_state == PlayIterator.ITERATING_ALWAYS:
num_always += 1
display.debug("done counting tasks in each state of execution:\n\tnum_setups: %s\n\tnum_tasks: %s\n\tnum_rescue: %s\n\tnum_always: %s" % (num_setups,
def _advance_selected_hosts(hosts, cur_block, cur_state):
This helper returns the task for all hosts in the requested
state, otherwise they get a noop dummy task. This also advances
the state of the host, since the given states are determined
while using peek=True.
# we return the values in the order they were originally
# specified in the given hosts array
rvals = []
display.debug("starting to advance hosts")
for host in hosts:
host_state_task = host_tasks.get(
if host_state_task is None:
(s, t) = host_state_task
if t is None:
if s.run_state == cur_state and s.cur_block == cur_block:
new_t = iterator.get_next_task_for_host(host)
rvals.append((host, t))
rvals.append((host, noop_task))
display.debug("done advancing hosts to next task")
return rvals
# if any hosts are in ITERATING_SETUP, return the setup task
# while all other hosts get a noop
if num_setups:
display.debug("advancing hosts in ITERATING_SETUP")
return _advance_selected_hosts(hosts, lowest_cur_block, PlayIterator.ITERATING_SETUP)
# if any hosts are in ITERATING_TASKS, return the next normal
# task for these hosts, while all other hosts get a noop
if num_tasks:
display.debug("advancing hosts in ITERATING_TASKS")
return _advance_selected_hosts(hosts, lowest_cur_block, PlayIterator.ITERATING_TASKS)
# if any hosts are in ITERATING_RESCUE, return the next rescue
# task for these hosts, while all other hosts get a noop
if num_rescue:
display.debug("advancing hosts in ITERATING_RESCUE")
return _advance_selected_hosts(hosts, lowest_cur_block, PlayIterator.ITERATING_RESCUE)
# if any hosts are in ITERATING_ALWAYS, return the next always
# task for these hosts, while all other hosts get a noop
if num_always:
display.debug("advancing hosts in ITERATING_ALWAYS")
return _advance_selected_hosts(hosts, lowest_cur_block, PlayIterator.ITERATING_ALWAYS)
# at this point, everything must be ITERATING_COMPLETE, so we
# return None for all hosts in the list
display.debug("all hosts are done, so returning None's for all hosts")
return [(host, None) for host in hosts]
def run(self, iterator, play_context):
The linear strategy is simple - get the next task and queue
it for all hosts, then wait for the queue to drain before
moving on to the next task
# iteratate over each task, while there is one left to run
result = self._tqm.RUN_OK
work_to_do = True
while work_to_do and not self._tqm._terminated:
display.debug("getting the remaining hosts for this loop")
hosts_left = self.get_hosts_left(iterator)
display.debug("done getting the remaining hosts for this loop")
# queue up this task for each host in the inventory
callback_sent = False
work_to_do = False
host_results = []
host_tasks = self._get_next_task_lockstep(hosts_left, iterator)
# skip control
skip_rest = False
choose_step = True
# flag set if task is set to any_errors_fatal
any_errors_fatal = False
results = []
for (host, task) in host_tasks:
if not task:
if self._tqm._terminated:
run_once = False
work_to_do = True
# test to see if the task across all hosts points to an action plugin which
# sets BYPASS_HOST_LOOP to true, or if it has run_once enabled. If so, we
# will only send this task to the first host in the list.
action = action_loader.get(task.action, class_only=True)
except KeyError:
# we don't care here, because the action may simply not have a
# corresponding action plugin
action = None
# check to see if this task should be skipped, due to it being a member of a
# role which has already run (and whether that role allows duplicate execution)
if task._role and task._role.has_run(host):
# If there is no metadata, the default behavior is to not allow duplicates,
# if there is metadata, check to see if the allow_duplicates flag was set to true
if task._role._metadata is None or task._role._metadata and not task._role._metadata.allow_duplicates:
display.debug("'%s' skipped because role has already run" % task)
if task.action == 'meta':
# for the linear strategy, we run meta tasks just once and for
# all hosts currently being iterated over rather than one host
results.extend(self._execute_meta(task, play_context, iterator, host))
if task.args.get('_raw_params', None) not in ('noop', 'reset_connection'):
run_once = True
# handle step if needed, skip meta actions as they are used internally
if self._step and choose_step:
if self._take_step(task):
choose_step = False
skip_rest = True
display.debug("getting variables")
task_vars = self._variable_manager.get_vars(play=iterator._play, host=host, task=task)
self.add_tqm_variables(task_vars, play=iterator._play)
templar = Templar(loader=self._loader, variables=task_vars)
display.debug("done getting variables")
run_once = templar.template(task.run_once) or action and getattr(action, 'BYPASS_HOST_LOOP', False)
if (task.any_errors_fatal or run_once) and not task.ignore_errors:
any_errors_fatal = True
if not callback_sent:
display.debug("sending task start callback, copying the task so we can template it temporarily")
saved_name =
display.debug("done copying, going to template now")
try: = to_text(templar.template(, fail_on_undefined=False), nonstring='empty')
display.debug("done templating")
# just ignore any errors during task name templating,
# we don't care if it just shows the raw name
display.debug("templating failed for some reason")
display.debug("here goes the callback...")
self._tqm.send_callback('v2_playbook_on_task_start', task, is_conditional=False) = saved_name
callback_sent = True
display.debug("sending task start callback")
self._blocked_hosts[host.get_name()] = True
self._queue_task(host, task, task_vars, play_context)
del task_vars
# if we're bypassing the host loop, break out now
if run_once:
results += self._process_pending_results(iterator, max_passes=max(1, int(len(self._tqm._workers) * 0.1)))
# go to next host/task group
if skip_rest:
display.debug("done queuing things up, now waiting for results queue to drain")
if self._pending_results > 0:
results += self._wait_on_pending_results(iterator)
included_files = IncludedFile.process_include_results(
except AnsibleError as e:
# this is a fatal error, so we abort here regardless of block state
return self._tqm.RUN_ERROR
include_failure = False
if len(included_files) > 0:
display.debug("we have included files to process")
display.debug("generating all_blocks data")
all_blocks = dict((host, []) for host in hosts_left)
display.debug("done generating all_blocks data")
for included_file in included_files:
display.debug("processing included file: %s" % included_file._filename)
# included hosts get the task list while those excluded get an equal-length
# list of noop tasks, to make sure that they continue running in lock-step
if included_file._is_role:
new_ir = self._copy_included_file(included_file)
new_blocks, handler_blocks = new_ir.get_block_list(
self._tqm.update_handler_list([handler for handler_block in handler_blocks for handler in handler_block.block])
new_blocks = self._load_included_file(included_file, iterator=iterator)
display.debug("iterating over new_blocks loaded from include file")
for new_block in new_blocks:
task_vars = self._variable_manager.get_vars(
display.debug("filtering new block on tags")
final_block = new_block.filter_tagged_tasks(play_context, task_vars)
display.debug("done filtering new block on tags")
noop_block = self._prepare_and_create_noop_block_from(final_block, task._parent, iterator)
for host in hosts_left:
if host in included_file._hosts:
display.debug("done iterating over new_blocks loaded from include file")
except AnsibleError as e:
for host in included_file._hosts:
self._tqm._failed_hosts[] = True
display.error(to_text(e), wrap_text=False)
include_failure = True
# finally go through all of the hosts and append the
# accumulated blocks to their list of tasks
display.debug("extending task lists for all hosts with included blocks")
for host in hosts_left:
iterator.add_tasks(host, all_blocks[host])
display.debug("done extending task lists")
display.debug("done processing included files")
display.debug("results queue empty")
display.debug("checking for any_errors_fatal")
failed_hosts = []
unreachable_hosts = []
for res in results:
if res.is_failed() and iterator.is_failed(res._host):
elif res.is_unreachable():
# if any_errors_fatal and we had an error, mark all hosts as failed
if any_errors_fatal and (len(failed_hosts) > 0 or len(unreachable_hosts) > 0):
dont_fail_states = frozenset([iterator.ITERATING_RESCUE, iterator.ITERATING_ALWAYS])
for host in hosts_left:
(s, _) = iterator.get_next_task_for_host(host, peek=True)
if s.run_state not in dont_fail_states or \
s.run_state == iterator.ITERATING_RESCUE and s.fail_state & iterator.FAILED_RESCUE != 0:
self._tqm._failed_hosts[] = True
result |= self._tqm.RUN_FAILED_BREAK_PLAY
display.debug("done checking for any_errors_fatal")
display.debug("checking for max_fail_percentage")
if iterator._play.max_fail_percentage is not None and len(results) > 0:
percentage = iterator._play.max_fail_percentage / 100.0
if (len(self._tqm._failed_hosts) / iterator.batch_size) > percentage:
for host in hosts_left:
# don't double-mark hosts, or the iterator will potentially
# fail them out of the rescue/always states
if not in failed_hosts:
self._tqm._failed_hosts[] = True
result |= self._tqm.RUN_FAILED_BREAK_PLAY
display.debug('(%s failed / %s total )> %s max fail' % (len(self._tqm._failed_hosts), iterator.batch_size, percentage))
display.debug("done checking for max_fail_percentage")
display.debug("checking to see if all hosts have failed and the running result is not ok")
if result != self._tqm.RUN_OK and len(self._tqm._failed_hosts) >= len(hosts_left):
display.debug("^ not ok, so returning result now")
return result
display.debug("done checking to see if all hosts have failed")
except (IOError, EOFError) as e:
display.debug("got IOError/EOFError in task loop: %s" % e)
# most likely an abort, return failed
return self._tqm.RUN_UNKNOWN_ERROR
# run the base class run() method, which executes the cleanup function
# and runs any outstanding handlers which have been triggered
return super(StrategyModule, self).run(iterator, play_context, result)