Allow callbacks from forks (#70501)

* POC for supporting callback events that come from the worker

* linting fixes. ci_complete

* fix up units. ci_complete

* Try moving the sentinel put higher. ci_complete

* safeguards. ci_complete

* Move queue killing to terminate

* LINTING. ci_complete

* Subclass Queue, to add helper send_callback method

* Just use _final_q instead of adding another queue and thread

* Revert a few changes

* Add helper for inserting a TaskResult into the _final_q

* Add changelog fragment

* Address rebase issue

* ci_complete

* Add test to assert async poll callback from fork

* Don't use full path

* ci_complete

* Use _results_lock as a context manager

* Add new generic lock decorator, and use it with send_callback

changelogs/fragments/14681-allow-callbacks-from-forks.yml

@@ -0,0 +1,3 @@
+minor_changes:
+- callbacks - Add feature allowing forks to send callback events
+  (https://github.com/ansible/ansible/issues/14681)

lib/ansible/executor/process/worker.py

@@ -166,41 +166,38 @@ class WorkerProcess(multiprocessing_context.Process):
             display.debug("done running TaskExecutor() for %s/%s [%s]" % (self._host, self._task, self._task._uuid))
             self._host.vars = dict()
             self._host.groups = []
-            task_result = TaskResult(
+
+            # put the result on the result queue
+            display.debug("sending task result for task %s" % self._task._uuid)
+            self._final_q.send_task_result(
                 self._host.name,
                 self._task._uuid,
                 executor_result,
                 task_fields=self._task.dump_attrs(),
             )
-
-            # put the result on the result queue
-            display.debug("sending task result for task %s" % self._task._uuid)
-            self._final_q.put(task_result)
             display.debug("done sending task result for task %s" % self._task._uuid)
 
         except AnsibleConnectionFailure:
             self._host.vars = dict()
             self._host.groups = []
-            task_result = TaskResult(
+            self._final_q.send_task_result(
                 self._host.name,
                 self._task._uuid,
                 dict(unreachable=True),
                 task_fields=self._task.dump_attrs(),
             )
-            self._final_q.put(task_result, block=False)
 
         except Exception as e:
             if not isinstance(e, (IOError, EOFError, KeyboardInterrupt, SystemExit)) or isinstance(e, TemplateNotFound):
                 try:
                     self._host.vars = dict()
                     self._host.groups = []
-                    task_result = TaskResult(
+                    self._final_q.send_task_result(
                         self._host.name,
                         self._task._uuid,
                         dict(failed=True, exception=to_text(traceback.format_exc()), stdout=''),
                         task_fields=self._task.dump_attrs(),
                     )
-                    self._final_q.put(task_result, block=False)
                 except Exception:
                     display.debug(u"WORKER EXCEPTION: %s" % to_text(e))
                     display.debug(u"WORKER TRACEBACK: %s" % to_text(traceback.format_exc()))

lib/ansible/executor/task_executor.py

@@ -377,14 +377,11 @@ class TaskExecutor:
                     'msg': 'Failed to template loop_control.label: %s' % to_text(e)
                 })
 
-            self._final_q.put(
+            self._final_q.send_task_result(
-                TaskResult(
                 self._host.name,
                 self._task._uuid,
                 res,
                 task_fields=task_fields,
-                ),
-                block=False,
             )
             results.append(res)
             del task_vars[loop_var]
@@ -600,7 +597,6 @@ class TaskExecutor:
             if self._task.async_val > 0:
                 if self._task.poll > 0 and not result.get('skipped') and not result.get('failed'):
                     result = self._poll_async_result(result=result, templar=templar, task_vars=vars_copy)
-                    # FIXME callback 'v2_runner_on_async_poll' here
 
                 # ensure no log is preserved
                 result["_ansible_no_log"] = self._play_context.no_log
@@ -672,7 +668,7 @@ class TaskExecutor:
                         result['_ansible_retry'] = True
                         result['retries'] = retries
                         display.debug('Retrying task, attempt %d of %d' % (attempt, retries))
-                        self._final_q.put(TaskResult(self._host.name, self._task._uuid, result, task_fields=self._task.dump_attrs()), block=False)
+                        self._final_q.send_task_result(self._host.name, self._task._uuid, result, task_fields=self._task.dump_attrs())
                         time.sleep(delay)
                         self._handler = self._get_action_handler(connection=self._connection, templar=templar)
         else:
@@ -778,6 +774,15 @@ class TaskExecutor:
                     raise
             else:
                 time_left -= self._task.poll
+                self._final_q.send_callback(
+                    'v2_runner_on_async_poll',
+                    TaskResult(
+                        self._host,
+                        async_task,
+                        async_result,
+                        task_fields=self._task.dump_attrs(),
+                    ),
+                )
 
         if int(async_result.get('finished', 0)) != 1:
             if async_result.get('_ansible_parsed'):

lib/ansible/executor/task_queue_manager.py

@@ -21,7 +21,9 @@ __metaclass__ = type
 
 import os
 import tempfile
+import threading
 import time
+import multiprocessing.queues
 
 from ansible import constants as C
 from ansible import context
@@ -29,7 +31,7 @@ from ansible.errors import AnsibleError
 from ansible.executor.play_iterator import PlayIterator
 from ansible.executor.stats import AggregateStats
 from ansible.executor.task_result import TaskResult
-from ansible.module_utils.six import string_types
+from ansible.module_utils.six import PY3, string_types
 from ansible.module_utils._text import to_text, to_native
 from ansible.playbook.play_context import PlayContext
 from ansible.plugins.loader import callback_loader, strategy_loader, module_loader
@@ -38,6 +40,7 @@ from ansible.template import Templar
 from ansible.vars.hostvars import HostVars
 from ansible.vars.reserved import warn_if_reserved
 from ansible.utils.display import Display
+from ansible.utils.lock import lock_decorator
 from ansible.utils.multiprocessing import context as multiprocessing_context
 
 
@@ -46,6 +49,36 @@ __all__ = ['TaskQueueManager']
 display = Display()
 
 
+class CallbackSend:
+    def __init__(self, method_name, *args, **kwargs):
+        self.method_name = method_name
+        self.args = args
+        self.kwargs = kwargs
+
+
+class FinalQueue(multiprocessing.queues.Queue):
+    def __init__(self, *args, **kwargs):
+        if PY3:
+            kwargs['ctx'] = multiprocessing_context
+        super(FinalQueue, self).__init__(*args, **kwargs)
+
+    def send_callback(self, method_name, *args, **kwargs):
+        self.put(
+            CallbackSend(method_name, *args, **kwargs),
+            block=False
+        )
+
+    def send_task_result(self, *args, **kwargs):
+        if isinstance(args[0], TaskResult):
+            tr = args[0]
+        else:
+            tr = TaskResult(*args, **kwargs)
+        self.put(
+            tr,
+            block=False
+        )
+
+
 class TaskQueueManager:
 
     '''
@@ -95,10 +128,12 @@ class TaskQueueManager:
         self._unreachable_hosts = dict()
 
         try:
-            self._final_q = multiprocessing_context.Queue()
+            self._final_q = FinalQueue()
         except OSError as e:
             raise AnsibleError("Unable to use multiprocessing, this is normally caused by lack of access to /dev/shm: %s" % to_native(e))
 
+        self._callback_lock = threading.Lock()
+
         # A temporary file (opened pre-fork) used by connection
         # plugins for inter-process locking.
         self._connection_lockfile = tempfile.TemporaryFile()
@@ -316,6 +351,7 @@ class TaskQueueManager:
                 defunct = True
         return defunct
 
+    @lock_decorator(attr='_callback_lock')
     def send_callback(self, method_name, *args, **kwargs):
         for callback_plugin in [self._stdout_callback] + self._callback_plugins:
             # a plugin that set self.disabled to True will not be called

lib/ansible/plugins/callback/default.py

@@ -421,6 +421,16 @@ class CallbackModule(CallbackBase):
             msg += "Result was: %s" % self._dump_results(result._result)
         self._display.display(msg, color=C.COLOR_DEBUG)
 
+    def v2_runner_on_async_poll(self, result):
+        host = result._host.get_name()
+        jid = result._result.get('ansible_job_id')
+        started = result._result.get('started')
+        finished = result._result.get('finished')
+        self._display.display(
+            'ASYNC POLL on %s: jid=%s started=%s finished=%s' % (host, jid, started, finished),
+            color=C.COLOR_DEBUG
+        )
+
     def v2_playbook_on_notify(self, handler, host):
         if self._display.verbosity > 1:
             self._display.display("NOTIFIED HANDLER %s for %s" % (handler.get_name(), host), color=C.COLOR_VERBOSE, screen_only=True)

lib/ansible/plugins/strategy/__init__.py

@@ -37,6 +37,7 @@ from ansible.errors import AnsibleError, AnsibleFileNotFound, AnsibleParserError
 from ansible.executor import action_write_locks
 from ansible.executor.process.worker import WorkerProcess
 from ansible.executor.task_result import TaskResult
+from ansible.executor.task_queue_manager import CallbackSend
 from ansible.module_utils.six.moves import queue as Queue
 from ansible.module_utils.six import iteritems, itervalues, string_types
 from ansible.module_utils._text import to_text
@@ -92,8 +93,10 @@ def results_thread_main(strategy):
             result = strategy._final_q.get()
             if isinstance(result, StrategySentinel):
                 break
-            else:
+            elif isinstance(result, CallbackSend):
-                strategy._results_lock.acquire()
+                strategy._tqm.send_callback(result.method_name, *result.args, **result.kwargs)
+            elif isinstance(result, TaskResult):
+                with strategy._results_lock:
                     # only handlers have the listen attr, so this must be a handler
                     # we split up the results into two queues here to make sure
                     # handler and regular result processing don't cross wires
@@ -101,7 +104,8 @@ def results_thread_main(strategy):
                         strategy._handler_results.append(result)
                     else:
                         strategy._results.append(result)
-                strategy._results_lock.release()
+            else:
+                display.warning('Received an invalid object (%s) in the result queue: %r' % (type(result), result))
         except (IOError, EOFError):
             break
         except Queue.Empty:

lib/ansible/utils/lock.py

@@ -0,0 +1,43 @@
+# Copyright (c) 2020 Matt Martz <matt@sivel.net>
+# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
+
+# Make coding more python3-ish
+from __future__ import (absolute_import, division, print_function)
+__metaclass__ = type
+
+from functools import wraps
+
+
+def lock_decorator(attr='missing_lock_attr', lock=None):
+    '''This decorator is a generic implementation that allows you
+    to either use a pre-defined instance attribute as the location
+    of the lock, or to explicitly pass a lock object.
+
+    This code was implemented with ``threading.Lock`` in mind, but
+    may work with other locks, assuming that they function as
+    context managers.
+
+    When using ``attr``, the assumption is the first argument to
+    the wrapped method, is ``self`` or ``cls``.
+
+    Examples:
+
+        @lock_decorator(attr='_callback_lock')
+        def send_callback(...):
+
+        @lock_decorator(lock=threading.Lock())
+        def some_method(...):
+    '''
+    def outer(func):
+        @wraps(func)
+        def inner(*args, **kwargs):
+            # Python2 doesn't have ``nonlocal``
+            # assign the actual lock to ``_lock``
+            if lock is None:
+                _lock = getattr(args[0], attr)
+            else:
+                _lock = lock
+            with _lock:
+                return func(*args, **kwargs)
+        return inner
+    return outer

test/integration/targets/async/callback_test.yml

@@ -0,0 +1,7 @@
+- hosts: localhost
+  gather_facts: false
+  tasks:
+    - name: Async poll callback test
+      command: sleep 5
+      async: 6
+      poll: 1

test/integration/targets/async/tasks/main.yml

@@ -298,3 +298,11 @@
     {{ ansible_python_interpreter|default('/usr/bin/python') }} -c 'import os; os.fdopen(os.dup(0), "r")'
   async: 1
   poll: 1
+
+- name: run async poll callback test playbook
+  command: ansible-playbook {{ role_path }}/callback_test.yml
+  register: callback_output
+
+- assert:
+    that:
+      - '"ASYNC POLL on localhost" in callback_output.stdout'