path: root/lib/ansible/plugins/strategy/free.py

# (c) 2012-2014, Michael DeHaan <michael.dehaan@gmail.com>
#
# 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
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# 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 <http://www.gnu.org/licenses/>.
# Make coding more python3-ish
from __future__ import (absolute_import, division, print_function)
__metaclass__ = type

DOCUMENTATION = '''
    name: free
    short_description: Executes tasks without waiting for all hosts
    description:
        - Task execution is as fast as possible per batch as defined by C(serial) (default all).
          Ansible will not wait for other hosts to finish the current task before queuing more tasks for other hosts.
          All hosts are still attempted for the current task, but it prevents blocking new tasks for hosts that have already finished.
        - With the free strategy, unlike the default linear strategy, a host that is slow or stuck on a specific task
          won't hold up the rest of the hosts and tasks.
    version_added: "2.0"
    author: Ansible Core Team
'''

import time

from ansible import constants as C
from ansible.errors import AnsibleError, AnsibleParserError
from ansible.playbook.handler import Handler
from ansible.playbook.included_file import IncludedFile
from ansible.plugins.loader import action_loader
from ansible.plugins.strategy import StrategyBase
from ansible.template import Templar
from ansible.module_utils._text import to_text
from ansible.utils.display import Display

display = Display()


class StrategyModule(StrategyBase):

    # This strategy manages throttling on its own, so we don't want it done in queue_task
    ALLOW_BASE_THROTTLING = False

    def __init__(self, tqm):
        super(StrategyModule, self).__init__(tqm)
        self._host_pinned = False

    def run(self, iterator, play_context):
        '''
        The "free" strategy is a bit more complex, in that it allows tasks to
        be sent to hosts as quickly as they can be processed. This means that
        some hosts may finish very quickly if run tasks result in little or no
        work being done versus other systems.

        The algorithm used here also tries to be more "fair" when iterating
        through hosts by remembering the last host in the list to be given a task
        and starting the search from there as opposed to the top of the hosts
        list again, which would end up favoring hosts near the beginning of the
        list.
        '''

        # the last host to be given a task
        last_host = 0

        result = self._tqm.RUN_OK

        # start with all workers being counted as being free
        workers_free = len(self._workers)

        self._set_hosts_cache(iterator._play)

        if iterator._play.max_fail_percentage is not None:
            display.warning("Using max_fail_percentage with the free strategy is not supported, as tasks are executed independently on each host")

        work_to_do = True
        while work_to_do and not self._tqm._terminated:

            hosts_left = self.get_hosts_left(iterator)

            if len(hosts_left) == 0:
                self._tqm.send_callback('v2_playbook_on_no_hosts_remaining')
                result = False
                break

            work_to_do = False        # assume we have no more work to do
            starting_host = last_host  # save current position so we know when we've looped back around and need to break

            # try and find an unblocked host with a task to run
            host_results = []
            while True:
                host = hosts_left[last_host]
                display.debug("next free host: %s" % host)
                host_name = host.get_name()

                # peek at the next task for the host, to see if there's
                # anything to do do for this host
                (state, task) = iterator.get_next_task_for_host(host, peek=True)
                display.debug("free host state: %s" % state, host=host_name)
                display.debug("free host task: %s" % task, host=host_name)

                # check if there is work to do, either there is a task or the host is still blocked which could
                # mean that it is processing an include task and after its result is processed there might be
                # more tasks to run
                if (task or self._blocked_hosts.get(host_name, False)) and not self._tqm._unreachable_hosts.get(host_name, False):
                    display.debug("this host has work to do", host=host_name)
                    # set the flag so the outer loop knows we've still found
                    # some work which needs to be done
                    work_to_do = True

                if not self._tqm._unreachable_hosts.get(host_name, False) and task:
                    # check to see if this host is blocked (still executing a previous task)
                    if not self._blocked_hosts.get(host_name, False):
                        display.debug("getting variables", host=host_name)
                        task_vars = self._variable_manager.get_vars(play=iterator._play, host=host, task=task,
                                                                    _hosts=self._hosts_cache,
                                                                    _hosts_all=self._hosts_cache_all)
                        self.add_tqm_variables(task_vars, play=iterator._play)
                        templar = Templar(loader=self._loader, variables=task_vars)
                        display.debug("done getting variables", host=host_name)

                        try:
                            throttle = int(templar.template(task.throttle))
                        except Exception as e:
                            raise AnsibleError("Failed to convert the throttle value to an integer.", obj=task._ds, orig_exc=e)

                        if throttle > 0:
                            same_tasks = 0
                            for worker in self._workers:
                                if worker and worker.is_alive() and worker._task._uuid == task._uuid:
                                    same_tasks += 1

                            display.debug("task: %s, same_tasks: %d" % (task.get_name(), same_tasks))
                            if same_tasks >= throttle:
                                break

                        # advance the host, mark the host blocked, and queue it
                        self._blocked_hosts[host_name] = True
                        iterator.set_state_for_host(host.name, state)

                        try:
                            action = action_loader.get(task.action, class_only=True, collection_list=task.collections)
                        except KeyError:
                            # we don't care here, because the action may simply not have a
                            # corresponding action plugin
                            action = None

                        try:
                            task.name = to_text(templar.template(task.name, fail_on_undefined=False), nonstring='empty')
                            display.debug("done templating", host=host_name)
                        except Exception:
                            # 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", host=host_name)

                        run_once = templar.template(task.run_once) or action and getattr(action, 'BYPASS_HOST_LOOP', False)
                        if run_once:
                            if action and getattr(action, 'BYPASS_HOST_LOOP', False):
                                raise AnsibleError("The '%s' module bypasses the host loop, which is currently not supported in the free strategy "
                                                   "and would instead execute for every host in the inventory list." % task.action, obj=task._ds)
                            else:
                                display.warning("Using run_once with the free strategy is not currently supported. This task will still be "
                                                "executed for every host in the inventory list.")

                        # 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 not isinstance(task, Handler) and 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, host=host_name)
                                del self._blocked_hosts[host_name]
                                continue

                        if task.action in C._ACTION_META:
                            self._execute_meta(task, play_context, iterator, target_host=host)
                            self._blocked_hosts[host_name] = False
                        else:
                            # handle step if needed, skip meta actions as they are used internally
                            if not self._step or self._take_step(task, host_name):
                                if task.any_errors_fatal:
                                    display.warning("Using any_errors_fatal with the free strategy is not supported, "
                                                    "as tasks are executed independently on each host")
                                if isinstance(task, Handler):
                                    self._tqm.send_callback('v2_playbook_on_handler_task_start', task)
                                else:
                                    self._tqm.send_callback('v2_playbook_on_task_start', task, is_conditional=False)
                                self._queue_task(host, task, task_vars, play_context)
                                # each task is counted as a worker being busy
                                workers_free -= 1
                                del task_vars
                    else:
                        display.debug("%s is blocked, skipping for now" % host_name)

                # all workers have tasks to do (and the current host isn't done with the play).
                # loop back to starting host and break out
                if self._host_pinned and workers_free == 0 and work_to_do:
                    last_host = starting_host
                    break

                # move on to the next host and make sure we
                # haven't gone past the end of our hosts list
                last_host += 1
                if last_host > len(hosts_left) - 1:
                    last_host = 0

                # if we've looped around back to the start, break out
                if last_host == starting_host:
                    break

            results = self._process_pending_results(iterator)
            host_results.extend(results)

            # each result is counted as a worker being free again
            workers_free += len(results)

            self.update_active_connections(results)

            included_files = IncludedFile.process_include_results(
                host_results,
                iterator=iterator,
                loader=self._loader,
                variable_manager=self._variable_manager
            )

            if len(included_files) > 0:
                all_blocks = dict((host, []) for host in hosts_left)
                failed_includes_hosts = set()
                for included_file in included_files:
                    display.debug("collecting new blocks for %s" % included_file)
                    is_handler = False
                    try:
                        if included_file._is_role:
                            new_ir = self._copy_included_file(included_file)

                            new_blocks, handler_blocks = new_ir.get_block_list(
                                play=iterator._play,
                                variable_manager=self._variable_manager,
                                loader=self._loader,
                            )
                        else:
                            is_handler = isinstance(included_file._task, Handler)
                            new_blocks = self._load_included_file(included_file, iterator=iterator, is_handler=is_handler)

                        # let PlayIterator know about any new handlers included via include_role or
                        # import_role within include_role/include_taks
                        iterator.handlers = [h for b in iterator._play.handlers for h in b.block]
                    except AnsibleParserError:
                        raise
                    except AnsibleError as e:
                        if included_file._is_role:
                            # include_role does not have on_include callback so display the error
                            display.error(to_text(e), wrap_text=False)
                        for r in included_file._results:
                            r._result['failed'] = True
                            failed_includes_hosts.add(r._host)
                        continue

                    for new_block in new_blocks:
                        if is_handler:
                            for task in new_block.block:
                                task.notified_hosts = included_file._hosts[:]
                            final_block = new_block
                        else:
                            task_vars = self._variable_manager.get_vars(
                                play=iterator._play,
                                task=new_block.get_first_parent_include(),
                                _hosts=self._hosts_cache,
                                _hosts_all=self._hosts_cache_all,
                            )
                            final_block = new_block.filter_tagged_tasks(task_vars)
                        for host in hosts_left:
                            if host in included_file._hosts:
                                all_blocks[host].append(final_block)
                    display.debug("done collecting new blocks for %s" % included_file)

                for host in failed_includes_hosts:
                    self._tqm._failed_hosts[host.name] = True
                    iterator.mark_host_failed(host)

                display.debug("adding all collected blocks from %d included file(s) to iterator" % len(included_files))
                for host in hosts_left:
                    iterator.add_tasks(host, all_blocks[host])
                display.debug("done adding collected blocks to iterator")

            # pause briefly so we don't spin lock
            time.sleep(C.DEFAULT_INTERNAL_POLL_INTERVAL)

        # collect all the final results
        results = self._wait_on_pending_results(iterator)

        # 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)