Prevent multiple background workers without global cache (#8401)

* Prevent multiple background workers without global cache

* Documentation updates

- New page dedicated to InvenTree process stack
- Update links
- Consolidate information

* Update mkdocs.yml

src/backend/InvenTree/InvenTree/api.py

@@ -221,6 +221,7 @@ class InfoView(AjaxView):
             'instance': InvenTree.version.inventreeInstanceName(),
             'apiVersion': InvenTree.version.inventreeApiVersion(),
             'worker_running': is_worker_running(),
+            'worker_count': settings.BACKGROUND_WORKER_COUNT,
             'worker_pending_tasks': self.worker_pending_tasks(),
             'plugins_enabled': settings.PLUGINS_ENABLED,
             'plugins_install_disabled': settings.PLUGINS_INSTALL_DISABLED,

src/backend/InvenTree/InvenTree/settings.py

@@ -851,13 +851,20 @@ _q_worker_timeout = int(
     get_setting('INVENTREE_BACKGROUND_TIMEOUT', 'background.timeout', 90)
 )
 
+
+# Prevent running multiple background workers if global cache is disabled
+# This is to prevent scheduling conflicts due to the lack of a shared cache
+BACKGROUND_WORKER_COUNT = (
+    int(get_setting('INVENTREE_BACKGROUND_WORKERS', 'background.workers', 4))
+    if GLOBAL_CACHE_ENABLED
+    else 1
+)
+
 # django-q background worker configuration
 Q_CLUSTER = {
     'name': 'InvenTree',
     'label': 'Background Tasks',
-    'workers': int(
-        get_setting('INVENTREE_BACKGROUND_WORKERS', 'background.workers', 4)
-    ),
+    'workers': BACKGROUND_WORKER_COUNT,
     'timeout': _q_worker_timeout,
     'retry': max(120, _q_worker_timeout + 30),
     'max_attempts': int(