Gather mount facts, fallback for when multiproc is not feasable (#83750)

* fallback to 'single threaded gathering' for when multiproc fails

Co-authored-by: Sviatoslav Sydorenko (Святослав Сидоренко) <wk.cvs.github@sydorenko.org.ua>

changelogs/fragments/gather_facts_single.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - setup module (fact gathering), added fallbcak code path to handle mount fact gathering in linux when threading is not available

lib/ansible/module_utils/facts/hardware/linux.py

@@ -21,6 +21,7 @@ import glob
 import json
 import os
 import re
+import signal
 import sys
 import time
 
@@ -38,6 +39,10 @@ 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")
@@ -577,7 +582,12 @@ class LinuxHardware(Hardware):
 
         # start threads to query each mount
         results = {}
-        pool = ThreadPool(processes=min(len(mtab_entries), cpu_count()))
+        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}")
+
         maxtime = timeout.GATHER_TIMEOUT or timeout.DEFAULT_GATHER_TIMEOUT
         for fields in mtab_entries:
             # Transform octal escape sequences
@@ -601,47 +611,67 @@ class LinuxHardware(Hardware):
                 if not self.MTAB_BIND_MOUNT_RE.match(options):
                     mount_info['options'] += ",bind"
 
-            results[mount] = {'info': mount_info,
-                              'extra': pool.apply_async(self.get_mount_info, (mount, device, uuids)),
-                              'timelimit': time.time() + maxtime}
+            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))
 
-        pool.close()  # done with new workers, start gc
+        if pool is None:
+            # serial processing, just assing results
+            mounts.append(results[mount]['info'])
+        else:
+            pool.close()  # done with spawing new workers, start gc
 
-        # wait for workers and get results
-        while 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']:
+            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
                         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)
+                        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}
 

test/integration/targets/gathering_facts/lib/multriprocessing/__init__.py

@@ -0,0 +1 @@
+from __future__ import annotations

test/integration/targets/gathering_facts/lib/multriprocessing/pool/__init__.py

@@ -0,0 +1,7 @@
+from __future__ import annotations
+
+
+class ThreadPool:
+
+    def __init__(self, *args, **kwargs):
+        raise PermissionError("To test single proc ansible")

test/integration/targets/gathering_facts/no_threads.yml

@@ -0,0 +1,21 @@
+- 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']

test/integration/targets/gathering_facts/runme.sh

@@ -38,4 +38,8 @@ 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"