[mod] document, simplify & pylint searx/shared/__init__.py

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/shared/__init__.py

@@ -1,50 +1,45 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
+# lint: pylint
+"""Initialization of a *shared* storage.
+
+The *shared* :py:obj:`storage` is a dictionary type that is stored:
+
+- in a redis DB.  If a redis DB is not available it is stored
+- in a uWSGI cache. If no uWSGI is not available it is stored
+- in a simple python dictionary.
+"""
 
 import logging
+from . import redisdb
 
 logger = logging.getLogger('searx.shared')
 
 __all__ = ["storage", "schedule"]
 
-
-try:
+if redisdb.init():
     # First: try to use Redis
-    from .redisdb import client
 
-    client().ping()
     from .shared_redis import RedisCacheSharedDict as SharedDict, schedule
 
     logger.info('Use shared_redis implementation')
-except Exception as e:
+
+else:
     # Second: try to use uwsgi
+
+    logger.error("can't connect redis DB, try to init uWSGI cache")
     try:
-        import uwsgi
-    except:
-        # Third : fall back to shared_simple
+        import uwsgi  # type: ignore
+
+        logger.info('Use shared_uwsgi implementation')
+        uwsgi.cache_update('dummy', b'dummy')
+        if uwsgi.cache_get('dummy') != b'dummy':
+            logger.error('found issues when using uWSGI, fall back to python dictionary')
+            from .shared_simple import SimpleSharedDict as SharedDict, schedule
+
+    except ModuleNotFoundError:
+        # Third: fall back to shared_simple
+
+        logger.error("uWSGI is not available, fall back to python dictionary")
         from .shared_simple import SimpleSharedDict as SharedDict, schedule
 
-        logger.info('Use shared_simple implementation')
-    else:
-        # Make sure uwsgi is okay
-        try:
-            uwsgi.cache_update('dummy', b'dummy')
-            if uwsgi.cache_get('dummy') != b'dummy':
-                raise Exception()  # pylint: disable=raise-missing-from
-        except:
-            # there is exception on a get/set test: disable all scheduling
-            logger.exception(
-                'uwsgi.ini configuration error, add this line to your uwsgi.ini\n'
-                'cache2 = name=searxngcache,items=2000,blocks=2000,blocksize=4096,bitmap=1\n'
-            )
-            from .shared_simple import SimpleSharedDict as SharedDict
-
-            def schedule(delay, func, *args):
-                return False
-
-        else:
-            # use uwsgi
-            from .shared_uwsgi import UwsgiCacheSharedDict as SharedDict, schedule
-
-            logger.info('Use shared_uwsgi implementation')
-
 storage = SharedDict()