fact gathering, mounts, fixes for single proc code and tests (#83866)

* Fact gathering fix 'no shm' branhc

* Use concurrent.futures instead of multiprocessing

This entirely avoids the need for fallback logic since the concurrent.futures thread pool does not depend on `/dev/shm`.

Co-authored-by: Matt Clay <matt@mystile.com>

5 files changed, 40 insertions, 105 deletions

diff --git a/lib/ansible/module_utils/facts/hardware/linux.py b/lib/ansible/module_utils/facts/hardware/linux.py
index a0772eff2d..293c75a250 100644
--- a/lib/ansible/module_utils/facts/hardware/linux.py
+++ b/lib/ansible/module_utils/facts/hardware/linux.py
@@ -21,15 +21,12 @@ import glob
 import json
 import os
 import re
-import signal
 import sys
 import time
 
-from multiprocessing import cpu_count
-from multiprocessing.pool import ThreadPool
-
-from ansible.module_utils.common.text.converters import to_text
+from ansible.module_utils._internal._concurrent import _futures
 from ansible.module_utils.common.locale import get_best_parsable_locale
+from ansible.module_utils.common.text.converters import to_text
 from ansible.module_utils.common.text.formatters import bytes_to_human
 from ansible.module_utils.facts.hardware.base import Hardware, HardwareCollector
 from ansible.module_utils.facts.utils import get_file_content, get_file_lines, get_mount_size
@@ -39,10 +36,6 @@ from ansible.module_utils.six import iteritems
 from ansible.module_utils.facts import timeout
 
 
-def _timeout_handler(signum, frame):
-    raise TimeoutError(f"Timeout reached in:{frame}")
-
-
 def get_partition_uuid(partname):
     try:
         uuids = os.listdir("/dev/disk/by-uuid")
@@ -582,12 +575,7 @@ class LinuxHardware(Hardware):
 
         # start threads to query each mount
         results = {}
-        pool = None
-        try:
-            pool = ThreadPool(processes=min(len(mtab_entries), cpu_count()))
-        except (IOError, OSError) as e:
-            self.module.warn(f"Cannot use multiprocessing, falling back on serial execution: {e}")
-
+        executor = _futures.DaemonThreadPoolExecutor()
         maxtime = timeout.GATHER_TIMEOUT or timeout.DEFAULT_GATHER_TIMEOUT
         for fields in mtab_entries:
             # Transform octal escape sequences
@@ -611,67 +599,46 @@ class LinuxHardware(Hardware):
                 if not self.MTAB_BIND_MOUNT_RE.match(options):
                     mount_info['options'] += ",bind"
 
-            results[mount] = {'info': mount_info, 'timelimit': time.time() + maxtime}
-            if pool is None:
-                old_handler = signal.signal(signal.SIGALRM, _timeout_handler)
-                signal.alarm(maxtime)
-                try:
-                    size, uuid = self.get_mount_info(mount, device, uuids)
-                except TimeoutError as e:
-                    results[mount]['info']['note'] = 'Could not get extra information due to timeout'
-                    self.module.log(f"Timeout while gathering mount {mount} data: {e}")
-                    self.module.warn(f"Timeout exceeded when getting mount info for {mount}")
-                finally:
-                    signal.alarm(0)
-                    signal.signal(signal.SIGALRM, old_handler)
-
-                if size:
-                    results[mount]['info'].update(size)
-                results[mount]['info']['uuid'] = uuid or 'N/A'
-            else:
-                # use multiproc pool, handle results below
-                results[mount]['extra'] = pool.apply_async(self.get_mount_info, (mount, device, uuids))
+            results[mount] = {'info': mount_info, 'timelimit': time.monotonic() + maxtime}
+            results[mount]['extra'] = executor.submit(self.get_mount_info, mount, device, uuids)
 
-        if pool is None:
-            # serial processing, just assing results
-            mounts.append(results[mount]['info'])
-        else:
-            pool.close()  # done with spawing new workers, start gc
+        # done with spawning new workers, start gc
+        executor.shutdown()
 
-            while results:  # wait for workers and get results
-                for mount in list(results):
-                    done = False
-                    res = results[mount]['extra']
-                    try:
-                        if res.ready():
-                            done = True
-                            if res.successful():
-                                mount_size, uuid = res.get()
-                                if mount_size:
-                                    results[mount]['info'].update(mount_size)
-                                results[mount]['info']['uuid'] = uuid or 'N/A'
-                            else:
-                                # failed, try to find out why, if 'res.successful' we know there are no exceptions
-                                results[mount]['info']['note'] = 'Could not get extra information: %s.' % (to_text(res.get()))
-
-                        elif time.time() > results[mount]['timelimit']:
-                            done = True
-                            self.module.warn("Timeout exceeded when getting mount info for %s" % mount)
-                            results[mount]['info']['note'] = 'Could not get extra information due to timeout'
-                    except Exception as e:
-                        import traceback
+        while results:  # wait for workers and get results
+            for mount in list(results):
+                done = False
+                res = results[mount]['extra']
+                try:
+                    if res.done():
                         done = True
-                        results[mount]['info'] = 'N/A'
-                        self.module.warn("Error prevented getting extra info for mount %s: [%s] %s." % (mount, type(e), to_text(e)))
-                        self.module.debug(traceback.format_exc())
-
-                    if done:
-                        # move results outside and make loop only handle pending
-                        mounts.append(results[mount]['info'])
-                        del results[mount]
-
-                # avoid cpu churn, sleep between retrying for loop with remaining mounts
-                time.sleep(0.1)
+                        if res.exception() is None:
+                            mount_size, uuid = res.result()
+                            if mount_size:
+                                results[mount]['info'].update(mount_size)
+                            results[mount]['info']['uuid'] = uuid or 'N/A'
+                        else:
+                            # failed, try to find out why, if 'res.successful' we know there are no exceptions
+                            results[mount]['info']['note'] = f'Could not get extra information: {res.exception()}'
+
+                    elif time.monotonic() > results[mount]['timelimit']:
+                        done = True
+                        self.module.warn("Timeout exceeded when getting mount info for %s" % mount)
+                        results[mount]['info']['note'] = 'Could not get extra information due to timeout'
+                except Exception as e:
+                    import traceback
+                    done = True
+                    results[mount]['info'] = 'N/A'
+                    self.module.warn("Error prevented getting extra info for mount %s: [%s] %s." % (mount, type(e), to_text(e)))
+                    self.module.debug(traceback.format_exc())
+
+                if done:
+                    # move results outside and make loop only handle pending
+                    mounts.append(results[mount]['info'])
+                    del results[mount]
+
+            # avoid cpu churn, sleep between retrying for loop with remaining mounts
+            time.sleep(0.1)
 
         return {'mounts': mounts}
 
diff --git a/test/integration/targets/gathering_facts/lib/multriprocessing/__init__.py b/test/integration/targets/gathering_facts/lib/multriprocessing/__init__.py
deleted file mode 100644
index 9d48db4f9f..0000000000
--- a/test/integration/targets/gathering_facts/lib/multriprocessing/__init__.py
+++ /dev/null
@@ -1 +0,0 @@
-from __future__ import annotations
diff --git a/test/integration/targets/gathering_facts/lib/multriprocessing/pool/__init__.py b/test/integration/targets/gathering_facts/lib/multriprocessing/pool/__init__.py
deleted file mode 100644
index 9c5a5d26a6..0000000000
--- a/test/integration/targets/gathering_facts/lib/multriprocessing/pool/__init__.py
+++ /dev/null
@@ -1,7 +0,0 @@
-from __future__ import annotations
-
-
-class ThreadPool:
-
-    def __init__(self, *args, **kwargs):
-        raise PermissionError("To test single proc ansible")
diff --git a/test/integration/targets/gathering_facts/no_threads.yml b/test/integration/targets/gathering_facts/no_threads.yml
deleted file mode 100644
index f8e21cd807..0000000000
--- a/test/integration/targets/gathering_facts/no_threads.yml
+++ /dev/null
@@ -1,21 +0,0 @@
-- hosts: localhost
-  tasks:
-  - block:
-    - set_fact:
-        normal_devices: "{{ ansible_facts['devices'].keys() }}"
-
-    - name: facts already gathered normally, but now we do mounts again w/o multithreading
-      gather_facts:
-        gather_subset: mounts
-      register: no_multi
-      environment:
-        PYTHONPATH: "${PWD}/lib"
-
-    - set_fact:
-        single_devices: "{{no_multi['ansible_facts']['ansible_devices'].keys()}}"
-
-    - assert:
-        that:
-          - normal_devices == single_devices
-    when:
-      - ansible_facts['os_family'] not in ['FreeBSD', 'Darwin']
diff --git a/test/integration/targets/gathering_facts/runme.sh b/test/integration/targets/gathering_facts/runme.sh
index 39824a4a52..ace83aa2ef 100755
--- a/test/integration/targets/gathering_facts/runme.sh
+++ b/test/integration/targets/gathering_facts/runme.sh
@@ -39,7 +39,4 @@ ANSIBLE_FACTS_MODULES='ansible.legacy.slow' ansible -m gather_facts localhost --
 # test parallelism
 ANSIBLE_FACTS_MODULES='dummy1,dummy2,dummy3' ansible -m gather_facts localhost --playbook-dir ./ -a 'gather_timeout=30 parallel=true' "$@" 2>&1
 
-# test lack of threads
-ansible-playbook no_threads.yml "$@" 2>&1
-
 rm "${OUTPUT_DIR}/canary.txt"