[enh] add redis connector searx/shared/redisdb.py

Add a redis connector, the default DB connector is a socket at::

    unix:///usr/local/searxng-redis/run/redis.sock?db=0

To set up a redis instance simply use::

    $ ./manage redis.build
    $ sudo -H ./manage redis.install

A hint for developers:

To get access rights to this instance, your developer account needs to be added
to the *searxng-redis* group::

    $ sudo -H ./manage redis.addgrp "${USER}"
    # don't forget to logout & login to get member of group

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

6 files changed, 87 insertions, 0 deletions

diff --git a/docs/admin/engines/settings.rst b/docs/admin/engines/settings.rst
index b04de7cb3..9f96a2b68 100644
--- a/docs/admin/engines/settings.rst
+++ b/docs/admin/engines/settings.rst
@@ -139,6 +139,36 @@ Global Settings
 ``default_http_headers``:
   Set additional HTTP headers, see `#755 <https://github.com/searx/searx/issues/715>`__
 
+
+.. _settings redis:
+
+``redis:``
+----------
+
+.. _Redis.from_url(url): https://redis-py.readthedocs.io/en/stable/connections.html#redis.client.Redis.from_url
+
+``url``
+  URL to connect redis database, see `Redis.from_url(url)`_ & :ref:`redis db`::
+
+    redis://[[username]:[password]]@localhost:6379/0
+    rediss://[[username]:[password]]@localhost:6379/0
+    unix://[[username]:[password]]@/path/to/socket.sock?db=0
+
+.. admonition:: Tip for developers
+
+   To set up a redis instance simply use::
+
+     $ ./manage redis.build
+     $ sudo -H ./manage redis.install
+
+   To get access rights to this instance, your developer account needs to be
+   added to the *searxng-redis* group::
+
+     $ sudo -H ./manage redis.addgrp "${USER}"
+     # don't forget to logout & login to get member of group
+
+.. _settings outgoing:
+
 ``outgoing:``
 -------------
 
diff --git a/docs/src/searx.shared.redisdb.rst b/docs/src/searx.shared.redisdb.rst
new file mode 100644
index 000000000..265d87617
--- /dev/null
+++ b/docs/src/searx.shared.redisdb.rst
@@ -0,0 +1,8 @@
+.. _redis db:
+
+========
+Redis DB
+========
+
+.. automodule:: searx.shared.redisdb
+  :members:
diff --git a/requirements.txt b/requirements.txt
index e42c1fb7f..e7645bd9b 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -13,3 +13,4 @@ uvloop==0.16.0
 httpx-socks[asyncio]==0.4.1
 langdetect==1.0.9
 setproctitle==1.2.2
+redis==4.1.0
diff --git a/searx/settings.yml b/searx/settings.yml
index 3227a5a55..0105c7939 100644
--- a/searx/settings.yml
+++ b/searx/settings.yml
@@ -61,6 +61,10 @@ server:
     X-Robots-Tag: noindex, nofollow
     Referrer-Policy: no-referrer
 
+redis:
+  # https://redis-py.readthedocs.io/en/stable/connections.html#redis.client.Redis.from_url
+  url: unix:///usr/local/searxng-redis/run/redis.sock?db=0
+
 ui:
   # Custom static path - leave it blank if you didn't change
   static_path: ""
diff --git a/searx/settings_defaults.py b/searx/settings_defaults.py
index 9c4711bfc..669f2fa87 100644
--- a/searx/settings_defaults.py
+++ b/searx/settings_defaults.py
@@ -169,6 +169,9 @@ SCHEMA = {
         'method': SettingsValue(('POST', 'GET'), 'POST'),
         'default_http_headers': SettingsValue(dict, {}),
     },
+    'redis': {
+        'url': SettingsValue(str, 'unix:///usr/local/searxng-redis/run/redis.sock?db=0'),
+    },
     'ui': {
         'static_path': SettingsDirectoryValue(str, os.path.join(searx_dir, 'static')),
         'templates_path': SettingsDirectoryValue(str, os.path.join(searx_dir, 'templates')),
diff --git a/searx/shared/redisdb.py b/searx/shared/redisdb.py
new file mode 100644
index 000000000..613b82a38
--- /dev/null
+++ b/searx/shared/redisdb.py
@@ -0,0 +1,41 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
+# lint: pylint
+"""Implementation of the redis client (redis-py_).
+
+.. _redis-py: https://github.com/redis/redis-py
+
+This implementation uses the :ref:`settings redis` setup from ``settings.yml``.
+A redis DB connect can be tested by::
+
+  >>> from searx.shared import redisdb
+  >>> redisdb.init()
+  True
+  >>> db = redisdb.client()
+  >>> db.set("foo", "bar")
+  True
+  >>> db.get("foo")
+  b'bar'
+  >>>
+
+"""
+
+import logging
+import redis
+from searx import get_setting
+
+logger = logging.getLogger('searx.shared.redis')
+
+
+def client():
+    return redis.Redis.from_url(get_setting('redis.url'))
+
+
+def init():
+    try:
+        c = client()
+        logger.info("connected redis DB --> %s", c.acl_whoami())
+        return True
+    except redis.exceptions.ConnectionError as exc:
+        logger.error("can't connet redis DB ...")
+        logger.error("  %s", exc)
+    return False