[mod] shared.storage: implement a backend to store in the redis DB

- implement shared_redis.RedisCacheSharedDict to store key/value pairs in the
  redis DB.  The default key_prefix is 'SearXNG_SharedDict'.

- simplify searx.shared and import RedisCacheSharedDict, set
  key_prefix to 'SearXNG_storage'

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

searx/shared/__init__.py

@@ -1,39 +1,48 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
+# lint: pylint
+"""Module implements a :py:obj:`storage`."""
+
+__all__ = ['schedule', 'storage']
 
 import logging
 import importlib
 
+from . import redisdb
+from . import shared_redis
+from . import shared_simple
+
 logger = logging.getLogger('searx.shared')
 
-__all__ = ['SharedDict', 'schedule']
+SharedDict = None
+schedule = None
+
+if redisdb.init():
+    SharedDict = shared_redis.RedisCacheSharedDict
+    logger.info('use redis DB for SharedDict')
 
 try:
+    from . import shared_uwsgi
     uwsgi = importlib.import_module('uwsgi')
-except:
-    # no uwsgi
-    from .shared_simple import SimpleSharedDict as SharedDict, schedule
+    uwsgi.cache_update('dummy', b'dummy')
+    if uwsgi.cache_get('dummy') != b'dummy':
+        raise Exception()
 
-    logger.info('Use shared_simple implementation')
-else:
-    try:
-        uwsgi.cache_update('dummy', b'dummy')
-        if uwsgi.cache_get('dummy') != b'dummy':
-            raise Exception()
-    except:
-        # uwsgi.ini configuration problem: disable all scheduling
-        logger.error(
-            'uwsgi.ini configuration error, add this line to your uwsgi.ini\n'
-            'cache2 = name=searxngcache,items=2000,blocks=2000,blocksize=4096,bitmap=1'
-        )
-        from .shared_simple import SimpleSharedDict as SharedDict
+    schedule = shared_uwsgi.schedule
+    logger.info('use shared_uwsgi for schedule')
 
-        def schedule(delay, func, *args):
-            return False
+    if SharedDict is None:
+        SharedDict = shared_simple.SimpleSharedDict
+        logger.info('use shared_uwsgi for SharedDict')
 
-    else:
-        # uwsgi
-        from .shared_uwsgi import UwsgiCacheSharedDict as SharedDict, schedule
+except Exception:  # pylint: disable=broad-except
+    logger.debug('skip uwsgi setup ..', exc_info=1)
 
-        logger.info('Use shared_uwsgi implementation')
+if SharedDict is None:
+    logger.info('use shared_simple for SharedDict')
+    SharedDict = shared_simple.SimpleSharedDict
 
-storage = SharedDict()
+if schedule is None:
+    logger.info('use shared_simple for schedule')
+    schedule = shared_simple.schedule
+
+storage = SharedDict(key_prefix='SearXNG_storage')

searx/shared/shared_abstract.py

@@ -5,6 +5,10 @@ from typing import Optional
 
 
 class SharedDict(ABC):
+
+    def __init__(self, *args, **kwarg):
+        pass
+
     @abstractmethod
     def get_int(self, key: str) -> Optional[int]:
         pass

searx/shared/shared_redis.py

@@ -0,0 +1,29 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
+# lint: pylint
+# pyright: strict
+"""Module implements a :py:class:`shared_abstract.SharedDict` to store data in a
+redis DB (:py:obj:`redisdb`)."""
+
+from typing import Optional
+from . import shared_abstract
+from . import redisdb
+
+class RedisCacheSharedDict(shared_abstract.SharedDict):
+    """Store key/value in the redis DB, the default prefix of the key in the DB is
+    ``SearXNG_SharedDict`` (see :py.obj:`searx.redislib.purge_by_prefix`)."""
+
+    def __init__(self, key_prefix='SearXNG_SharedDict'):
+        self.key_prefix = key_prefix
+
+    def get_int(self, key: str) -> Optional[int]:
+        return int(redisdb.client().get(self.key_prefix + key))
+
+    def set_int(self, key: str, value: int):
+        redisdb.client().set(self.key_prefix + key, str(value).encode())
+
+    def get_str(self, key: str) -> Optional[str]:
+        value = redisdb.client().get(self.key_prefix + key)
+        return None if value is None else value.decode()
+
+    def set_str(self, key: str, value: str):
+        redisdb.client().set(self.key_prefix + key, value.encode())