[docs] document NoSLQ engines MongoDB and redis

Slightly modified merge of commit [3b192e638]

[3b192e638] https://github.com/searx/searx/commit/3b192e638

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

docs/admin/engines/index.rst

@@ -17,6 +17,7 @@ Engines & Settings
    private-engines
    recoll
    sql-engines
+   nosql-engines
    search-indexer-engines
    command-line-engines
    searx.engines.xpath

docs/admin/engines/nosql-engines.rst

@@ -0,0 +1,136 @@
+===============
+NoSQL databases
+===============
+
+.. sidebar:: further read
+
+   - `NoSQL databases <https://en.wikipedia.org/wiki/NoSQL>`_
+   - `redis.io <https://redis.io/>`_
+   - `MongoDB <https://www.mongodb.com>`_
+
+The following `NoSQL databases`_ are supported:
+
+- :ref:`engine redis_server`
+- :ref:`engine mongodb`
+
+All of the engines above are just commented out in the :origin:`settings.yml
+<searx/settings.yml>`, as you have to set various options and install
+dependencies before using them.
+
+By default, the engines use the ``key-value`` template for displaying results /
+see :origin:`oscar <searx/templates/oscar/result_templates/key-value.html>` &
+:origin:`simple <searx/templates/simple/result_templates/key-value.html>`
+themes.  If you are not satisfied with the original result layout, you can use
+your own template, set ``result_template`` attribute to ``{template_name}`` and
+place the templates at::
+
+  searx/templates/{theme_name}/result_templates/{template_name}
+
+Futhermore, if you do not wish to expose these engines on a public instance, you
+can still add them and limit the access by setting ``tokens`` as described in
+section :ref:`private engines`.
+
+
+Configure the engines
+=====================
+
+`NoSQL databases`_ are used for storing arbitrary data without first defining
+their structure.
+
+
+Extra Dependencies
+------------------
+
+For using :ref:`engine redis_server` or :ref:`engine mongodb` you need to
+install additional packages in Python's Virtual Environment of your SearxNG
+instance.  To switch into the environment (:ref:`searx-src`) you can use
+:ref:`searx.sh`::
+
+  $ sudo utils/searx.sh shell
+  (searx-pyenv)$ pip install ...
+
+
+.. _engine redis_server:
+
+Redis Server
+------------
+
+.. _redis: https://github.com/andymccurdy/redis-py#installation
+
+.. sidebar:: info
+
+   - ``pip install`` redis_
+   - redis.io_
+   - :origin:`redis_server.py <searx/engines/redis_server.py>`
+
+
+Redis is an open source (BSD licensed), in-memory data structure (key value
+based) store.  Before configuring the ``redis_server`` engine, you must install
+the dependency redis_.
+
+Select a database to search in and set its index in the option ``db``.  You can
+either look for exact matches or use partial keywords to find what you are
+looking for by configuring ``exact_match_only``.  You find an example
+configuration below:
+
+.. code:: yaml
+
+  # Required dependency: redis
+
+  - name: myredis
+    shortcut : rds
+    engine: redis_server
+    exact_match_only: false
+    host: '127.0.0.1'
+    port: 6379
+    enable_http: true
+    password: ''
+    db: 0
+
+.. _engine mongodb:
+
+MongoDB
+-------
+
+.. _pymongo: https://github.com/mongodb/mongo-python-driver#installation
+
+.. sidebar:: info
+
+   - ``pip install`` pymongo_
+   - MongoDB_
+   - :origin:`mongodb.py <searx/engines/mongodb.py>`
+
+MongoDB_ is a document based database program that handles JSON like data.
+Before configuring the ``mongodb`` engine, you must install the dependency
+redis_.
+
+In order to query MongoDB_, you have to select a ``database`` and a
+``collection``.  Furthermore, you have to select a ``key`` that is going to be
+searched.  MongoDB_ also supports the option ``exact_match_only``, so configure
+it as you wish.  Below is an example configuration for using a MongoDB
+collection:
+
+.. code:: yaml
+
+  # MongoDB engine
+  # Required dependency: pymongo
+
+  - name: mymongo
+    engine: mongodb
+    shortcut: md
+    exact_match_only: false
+    host: '127.0.0.1'
+    port: 27017
+    enable_http: true
+    results_per_page: 20
+    database: 'business'
+    collection: 'reviews'  # name of the db collection
+    key: 'name'            # key in the collection to search for
+
+
+Acknowledgment
+==============
+
+This development was sponsored by `Search and Discovery Fund
+<https://nlnet.nl/discovery>`_ of `NLnet Foundation <https://nlnet.nl/>`_.
+

searx/settings.yml

@@ -819,6 +819,7 @@ engines:
   #   exact_match_only: false
   #   host: '127.0.0.1'
   #   port: 27017
+  #   enable_http: true
   #   results_per_page: 20
   #   database: 'business'
   #   collection: 'reviews'  # name of the db collection
@@ -1047,13 +1048,15 @@ engines:
     disabled: true
 
   # Required dependency: redis
-  #  - name: myredis
-  #    engine: redis_server
-  #    exact_match_only: False
-  #    host: '127.0.0.1'
-  #    port: 6379
-  #    password: ''
-  #    db: 0
+  # - name: myredis
+  #   shortcut : rds
+  #   engine: redis_server
+  #   exact_match_only: false
+  #   host: '127.0.0.1'
+  #   port: 6379
+  #   enable_http: true
+  #   password: ''
+  #   db: 0
 
   # tmp suspended: bad certificate
   #  - name: scanr structures