[mod] engines: migration of the individual cache solutions to EngineCache

The EngineCache class replaces all previously individual solutions for caches in
the context of the engines.

- demo_offline.py
- duckduckgo.py
- radio_browser.py
- soundcloud.py
- startpage.py
- wolframalpha_api.py
- wolframalpha_noapi.py

Search term to test most of the modified engines::

    !ddg !rb !sc !sp !wa test

    !ddg !rb !sc !sp !wa foo

For introspection of the DB, jump into developer environment and run command to
show cache state::

    $ ./manage pyenv.cmd bash --norc --noprofile
    (py3) python -m searx.enginelib cache state

    cache tables and key/values
    ===========================
    [demo_offline        ] 2025-04-22 11:32:50 count        --> (int) 4
    [startpage           ] 2025-04-22 12:32:30 SC_CODE      --> (str) fSOBnhEMlDfE20
    [duckduckgo          ] 2025-04-22 12:32:31 4dff493e.... --> (str) 4-128634958369380006627592672385352473325
    [duckduckgo          ] 2025-04-22 12:40:06 3e2583e2.... --> (str) 4-263126175288871260472289814259666848451
    [radio_browser       ] 2025-04-23 11:33:08 servers      --> (list) ['https://de2.api.radio-browser.info',  ...]
    [soundcloud          ] 2025-04-29 11:40:06 guest_client_id --> (str) EjkRJG0BLNEZquRiPZYdNtJdyGtTuHdp
    [wolframalpha        ] 2025-04-22 12:40:06 code         --> (str) 5aa79f86205ad26188e0e26e28fb7ae7
    number of tables: 6
    number of key/value pairs: 7

In the "cache tables and key/values" section, the table name (engine name) is at
first position on the second there is the calculated expire date and on the
third and fourth position the key/value is shown.

About duckduckgo: The *vqd coode* of ddg depends on the query term and therefore
the key is a hash value of the query term (to not to store the raw query term).

In the "properties of ENGINES_CACHE" section all properties of the SQLiteAppl /
ExpireCache and their last modification date are shown::

    properties of ENGINES_CACHE
    ===========================
    [last modified: 2025-04-22 11:32:27] DB_SCHEMA           : 1
    [last modified: 2025-04-22 11:32:27] LAST_MAINTENANCE    :
    [last modified: 2025-04-22 11:32:27] crypt_hash          : ca612e3566fdfd7cf7efe2b1c9349f461158d07cb78a3750e5c5be686aa8ebdc
    [last modified: 2025-04-22 11:32:30] CACHE-TABLE--demo_offline: demo_offline
    [last modified: 2025-04-22 11:32:30] CACHE-TABLE--startpage: startpage
    [last modified: 2025-04-22 11:32:31] CACHE-TABLE--duckduckgo: duckduckgo
    [last modified: 2025-04-22 11:33:08] CACHE-TABLE--radio_browser: radio_browser
    [last modified: 2025-04-22 11:40:06] CACHE-TABLE--soundcloud: soundcloud
    [last modified: 2025-04-22 11:40:06] CACHE-TABLE--wolframalpha: wolframalpha

These properties provide information about the state of the ExpireCache and
control the behavior.  For example, the maintenance intervals are controlled by
the last modification date of the LAST_MAINTENANCE property and the hash value
of the password can be used to detect whether the password has been changed (in
this case the DB entries can no longer be decrypted and the entire cache must be
discarded).

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

searx/engines/demo_offline.py

@@ -15,6 +15,7 @@ close to the implementation, its just a simple example.  To get in use of this
 import json
 
 from searx.result_types import EngineResults
+from searx.enginelib import EngineCache
 
 engine_type = 'offline'
 categories = ['general']
@@ -32,14 +33,18 @@ about = {
 # if there is a need for globals, use a leading underline
 _my_offline_engine: str = ""
 
+CACHE: EngineCache
+"""Persistent (SQLite) key/value cache that deletes its values after ``expire``
+seconds."""
 
-def init(engine_settings=None):
+
+def init(engine_settings):
     """Initialization of the (offline) engine.  The origin of this demo engine is a
     simple json string which is loaded in this example while the engine is
-    initialized.
+    initialized."""
+    global _my_offline_engine, CACHE  # pylint: disable=global-statement
 
-    """
-    global _my_offline_engine  # pylint: disable=global-statement
+    CACHE = EngineCache(engine_settings["name"])  # type:ignore
 
     _my_offline_engine = (
         '[ {"value": "%s"}'
@@ -57,8 +62,8 @@ def search(query, request_params) -> EngineResults:
     results.
     """
     res = EngineResults()
+    count = CACHE.get("count", 0)
 
-    count = 0
     for row in json.loads(_my_offline_engine):
         count += 1
         kvmap = {
@@ -75,4 +80,7 @@ def search(query, request_params) -> EngineResults:
             )
         )
     res.add(res.types.LegacyResult(number_of_results=count))
+
+    # cache counter value for 20sec
+    CACHE.set("count", count, expire=20)
     return res

searx/engines/duckduckgo.py

@@ -6,16 +6,17 @@ DuckDuckGo WEB
 
 from __future__ import annotations
 
-from typing import TYPE_CHECKING
+import json
 import re
+import typing
+
 from urllib.parse import quote_plus
-import json
+
 import babel
 import lxml.html
 
 from searx import (
     locales,
-    redislib,
     external_bang,
 )
 from searx.utils import (
@@ -25,12 +26,12 @@ from searx.utils import (
     extract_text,
 )
 from searx.network import get  # see https://github.com/searxng/searxng/issues/762
-from searx import redisdb
 from searx.enginelib.traits import EngineTraits
+from searx.enginelib import EngineCache
 from searx.exceptions import SearxEngineCaptchaException
 from searx.result_types import EngineResults
 
-if TYPE_CHECKING:
+if typing.TYPE_CHECKING:
     import logging
 
     logger: logging.Logger
@@ -61,28 +62,18 @@ url = "https://html.duckduckgo.com/html"
 
 time_range_dict = {'day': 'd', 'week': 'w', 'month': 'm', 'year': 'y'}
 form_data = {'v': 'l', 'api': 'd.js', 'o': 'json'}
-__CACHE = []
 
+CACHE: EngineCache
+"""Persistent (SQLite) key/value cache that deletes its values after ``expire``
+seconds."""
 
-def _cache_key(query: str, region: str):
-    return 'SearXNG_ddg_web_vqd' + redislib.secret_hash(f"{query}//{region}")
 
-
-def cache_vqd(query: str, region: str, value: str):
-    """Caches a ``vqd`` value from a query."""
-    c = redisdb.client()
-    if c:
-        logger.debug("VALKEY cache vqd value: %s (%s)", value, region)
-        c.set(_cache_key(query, region), value, ex=600)
-
-    else:
-        logger.debug("MEM cache vqd value: %s (%s)", value, region)
-        if len(__CACHE) > 100:  # cache vqd from last 100 queries
-            __CACHE.pop(0)
-        __CACHE.append((_cache_key(query, region), value))
+def init(_):  # pylint: disable=unused-argument
+    global CACHE  # pylint: disable=global-statement
+    CACHE = EngineCache("duckduckgo")  # type:ignore
 
 
-def get_vqd(query: str, region: str, force_request: bool = False):
+def get_vqd(query: str, region: str, force_request: bool = False) -> str:
     """Returns the ``vqd`` that fits to the *query*.
 
     :param query: The query term
@@ -114,31 +105,34 @@ def get_vqd(query: str, region: str, force_request: bool = False):
     seems the block list is a sliding window: to get my IP rid from the bot list
     I had to cool down my IP for 1h (send no requests from that IP to DDG).
     """
-    key = _cache_key(query, region)
-
-    c = redisdb.client()
-    if c:
-        value = c.get(key)
-        if value or value == b'':
-            value = value.decode('utf-8')  # type: ignore
-            logger.debug("re-use CACHED vqd value: %s", value)
-            return value
+    key = CACHE.secret_hash(f"{query}//{region}")
+    value = CACHE.get(key=key)
+    if value is not None and not force_request:
+        logger.debug("vqd: re-use cached value: %s", value)
+        return value
+
+    logger.debug("vqd: request value from from duckduckgo.com")
+    resp = get(f'https://duckduckgo.com/?q={quote_plus(query)}')
+    if resp.status_code == 200:  # type: ignore
+        value = extr(resp.text, 'vqd="', '"')  # type: ignore
+        if value:
+            logger.debug("vqd value from duckduckgo.com request: '%s'", value)
+        else:
+            logger.error("vqd: can't parse value from ddg response (return empty string)")
+            return ""
+    else:
+        logger.error("vqd: got HTTP %s from duckduckgo.com", resp.status_code)
 
-    for k, value in __CACHE:
-        if k == key:
-            logger.debug("MEM re-use CACHED vqd value: %s", value)
-            return value
+    if value:
+        CACHE.set(key=key, value=value)
+    else:
+        logger.error("vqd value from duckduckgo.com ", resp.status_code)
+    return value
 
-    if force_request:
-        resp = get(f'https://duckduckgo.com/?q={quote_plus(query)}')
-        if resp.status_code == 200:  # type: ignore
-            value = extr(resp.text, 'vqd="', '"')  # type: ignore
-            if value:
-                logger.debug("vqd value from DDG request: %s", value)
-                cache_vqd(query, region, value)
-                return value
 
-    return None
+def set_vqd(query: str, region: str, value: str):
+    key = CACHE.secret_hash(f"{query}//{region}")
+    CACHE.set(key=key, value=value, expire=3600)
 
 
 def get_ddg_lang(eng_traits: EngineTraits, sxng_locale, default='en_US'):
@@ -373,8 +367,11 @@ def response(resp) -> EngineResults:
         # some locales (at least China) does not have a "next page" button
         form = form[0]
         form_vqd = eval_xpath(form, '//input[@name="vqd"]/@value')[0]
-
-        cache_vqd(resp.search_params['data']['q'], resp.search_params['data']['kl'], form_vqd)
+        set_vqd(
+            query=resp.search_params['data']['q'],
+            region=resp.search_params['data']['kl'],
+            value=str(form_vqd),
+        )
 
     # just select "web-result" and ignore results of class "result--ad result--ad--small"
     for div_result in eval_xpath(doc, '//div[@id="links"]/div[contains(@class, "web-result")]'):
@@ -401,7 +398,7 @@ def response(resp) -> EngineResults:
         results.add(
             results.types.Answer(
                 answer=zero_click,
-                url=eval_xpath_getindex(doc, '//div[@id="zero_click_abstract"]/a/@href', 0),
+                url=eval_xpath_getindex(doc, '//div[@id="zero_click_abstract"]/a/@href', 0),  # type: ignore
             )
         )
 

searx/engines/radio_browser.py

@@ -5,7 +5,9 @@
    https://de1.api.radio-browser.info/#Advanced_station_search
 
 """
+from __future__ import annotations
 
+import typing
 import random
 import socket
 from urllib.parse import urlencode
@@ -13,9 +15,15 @@ import babel
 from flask_babel import gettext
 
 from searx.network import get
+from searx.enginelib import EngineCache
 from searx.enginelib.traits import EngineTraits
 from searx.locales import language_tag
 
+if typing.TYPE_CHECKING:
+    import logging
+
+    logger = logging.getLogger()
+
 traits: EngineTraits
 
 about = {
@@ -52,11 +60,24 @@ none filters are applied. Valid filters are:
 
 """
 
-servers = []
+CACHE: EngineCache
+"""Persistent (SQLite) key/value cache that deletes its values after ``expire``
+seconds."""
 
 
 def init(_):
-    # see https://api.radio-browser.info
+    global CACHE  # pylint: disable=global-statement
+    CACHE = EngineCache("radio_browser")
+    server_list()
+
+
+def server_list() -> list[str]:
+
+    servers = CACHE.get("servers", [])
+    if servers:
+        return servers
+
+    # hint: can take up to 40sec!
     ips = socket.getaddrinfo("all.api.radio-browser.info", 80, 0, 0, socket.IPPROTO_TCP)
     for ip_tuple in ips:
         _ip: str = ip_tuple[4][0]  # type: ignore
@@ -65,8 +86,22 @@ def init(_):
         if srv not in servers:
             servers.append(srv)
 
+    # update server list once in 24h
+    CACHE.set(key="servers", value=servers, expire=60 * 60 * 24)
+
+    return servers
+
 
 def request(query, params):
+
+    servers = server_list()
+    if not servers:
+        logger.error("Fetched server list is empty!")
+        params["url"] = None
+        return
+
+    server = random.choice(servers)
+
     args = {
         'name': query,
         'order': 'votes',
@@ -87,8 +122,7 @@ def request(query, params):
             if countrycode in traits.custom['countrycodes']:  # type: ignore
                 args['countrycode'] = countrycode
 
-    params['url'] = f"{random.choice(servers)}/json/stations/search?{urlencode(args)}"
-    return params
+    params['url'] = f"{server}/json/stations/search?{urlencode(args)}"
 
 
 def response(resp):
@@ -154,8 +188,9 @@ def fetch_traits(engine_traits: EngineTraits):
 
     babel_reg_list = get_global("territory_languages").keys()
 
-    language_list = get(f'{servers[0]}/json/languages').json()  # type: ignore
-    country_list = get(f'{servers[0]}/json/countries').json()  # type: ignore
+    server = server_list()[0]
+    language_list = get(f'{server}/json/languages').json()  # type: ignore
+    country_list = get(f'{server}/json/countries').json()  # type: ignore
 
     for lang in language_list:
 

searx/engines/soundcloud.py

@@ -1,14 +1,23 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
 """SoundCloud is a German audio streaming service."""
+from __future__ import annotations
 
 import re
-from urllib.parse import quote_plus, urlencode
+import typing
 import datetime
 
+from urllib.parse import quote_plus, urlencode
+
 from dateutil import parser
 from lxml import html
 
 from searx.network import get as http_get
+from searx.enginelib import EngineCache
+
+if typing.TYPE_CHECKING:
+    import logging
+
+    logger: logging.Logger
 
 about = {
     "website": "https://soundcloud.com",
@@ -28,7 +37,6 @@ HTML frontend of the common WEB site.
 """
 
 cid_re = re.compile(r'client_id:"([^"]*)"', re.I | re.U)
-guest_client_id = ""
 results_per_page = 10
 
 soundcloud_facet = "model"
@@ -48,6 +56,10 @@ app_locale_map = {
     "sv": "sv",
 }
 
+CACHE: EngineCache
+"""Persistent (SQLite) key/value cache that deletes its values after ``expire``
+seconds."""
+
 
 def request(query, params):
 
@@ -55,6 +67,12 @@ def request(query, params):
     # - user_id=451561-497874-703312-310156
     # - app_version=1740727428
 
+    guest_client_id = CACHE.get("guest_client_id")
+    if guest_client_id is None:
+        guest_client_id = get_client_id()
+        if guest_client_id:
+            CACHE.set(key="guest_client_id", value=guest_client_id)
+
     args = {
         "q": query,
         "offset": (params['pageno'] - 1) * results_per_page,
@@ -104,12 +122,12 @@ def response(resp):
     return results
 
 
-def init(engine_settings=None):  # pylint: disable=unused-argument
-    global guest_client_id  # pylint: disable=global-statement
-    guest_client_id = get_client_id()
+def init(engine_settings):  # pylint: disable=unused-argument
+    global CACHE  # pylint: disable=global-statement
+    CACHE = EngineCache(engine_settings["name"])  # type:ignore
 
 
-def get_client_id() -> str:
+def get_client_id() -> str | None:
 
     client_id = ""
     url = "https://soundcloud.com"
@@ -143,4 +161,4 @@ def get_client_id() -> str:
         logger.info("using client_id '%s' for soundclud queries", client_id)
     else:
         logger.warning("missing valid client_id for soundclud queries")
-    return client_id
+    return client_id or None

searx/engines/startpage.py

@@ -84,7 +84,6 @@ from typing import TYPE_CHECKING, Any
 from collections import OrderedDict
 import re
 from unicodedata import normalize, combining
-from time import time
 from datetime import datetime, timedelta
 from json import loads
 
@@ -97,6 +96,7 @@ from searx.network import get  # see https://github.com/searxng/searxng/issues/7
 from searx.exceptions import SearxEngineCaptchaException
 from searx.locales import region_tag
 from searx.enginelib.traits import EngineTraits
+from searx.enginelib import EngineCache
 
 if TYPE_CHECKING:
     import logging
@@ -159,10 +159,21 @@ search_form_xpath = '//form[@id="search"]'
     </form>
 """
 
-# timestamp of the last fetch of 'sc' code
-sc_code_ts = 0
-sc_code = ''
-sc_code_cache_sec = 30
+
+CACHE: EngineCache
+"""Persistent (SQLite) key/value cache that deletes its values after ``expire``
+seconds."""
+
+
+def init(_):
+    global CACHE  # pylint: disable=global-statement
+
+    # hint: all three startpage engines (WEB, Images & News) can/should use the
+    # same sc_code ..
+    CACHE = EngineCache("startpage")  # type:ignore
+
+
+sc_code_cache_sec = 3600
 """Time in seconds the sc-code is cached in memory :py:obj:`get_sc_code`."""
 
 
@@ -176,14 +187,10 @@ def get_sc_code(searxng_locale, params):
 
     Startpage's search form generates a new sc-code on each request.  This
     function scrap a new sc-code from Startpage's home page every
-    :py:obj:`sc_code_cache_sec` seconds.
-
-    """
-
-    global sc_code_ts, sc_code  # pylint: disable=global-statement
+    :py:obj:`sc_code_cache_sec` seconds."""
 
-    if sc_code and (time() < (sc_code_ts + sc_code_cache_sec)):
-        logger.debug("get_sc_code: reuse '%s'", sc_code)
+    sc_code = CACHE.get("SC_CODE", "")
+    if sc_code:
         return sc_code
 
     headers = {**params['headers']}
@@ -233,8 +240,9 @@ def get_sc_code(searxng_locale, params):
             message="get_sc_code: [PR-695] query new sc time-stamp failed! (%s)" % resp.url,  # type: ignore
         ) from exc
 
-    sc_code_ts = time()
+    sc_code = str(sc_code)
     logger.debug("get_sc_code: new value is: %s", sc_code)
+    CACHE.set(key="SC_CODE", value=sc_code, expire=sc_code_cache_sec)
     return sc_code
 
 

searx/engines/wolframalpha_api.py

@@ -5,7 +5,7 @@
 
 from urllib.parse import urlencode
 
-from lxml import etree
+import lxml.etree
 
 # about
 about = {
@@ -72,7 +72,7 @@ def replace_pua_chars(text):
 def response(resp):
     results = []
 
-    search_results = etree.XML(resp.content)
+    search_results = lxml.etree.XML(resp.content)
 
     # return empty array if there are no results
     if search_results.xpath(failure_xpath):

searx/engines/wolframalpha_noapi.py

@@ -3,11 +3,13 @@
  Wolfram|Alpha (Science)
 """
 
+from __future__ import annotations
+
 from json import loads
-from time import time
 from urllib.parse import urlencode
 
 from searx.network import get as http_get
+from searx.enginelib import EngineCache
 
 # about
 about = {
@@ -40,41 +42,39 @@ search_url = (
 
 referer_url = url + 'input/?{query}'
 
-token = {'value': '', 'last_updated': None}
-
 # pods to display as image in infobox
 # this pods do return a plaintext, but they look better and are more useful as images
 image_pods = {'VisualRepresentation', 'Illustration', 'Symbol'}
 
 
-# seems, wolframalpha resets its token in every hour
-def obtain_token():
-    update_time = time() - (time() % 3600)
-    try:
-        token_response = http_get('https://www.wolframalpha.com/input/api/v1/code?ts=9999999999999999999', timeout=2.0)
-        token['value'] = loads(token_response.text)['code']
-        token['last_updated'] = update_time
-    except:  # pylint: disable=bare-except
-        pass
-    return token
+CACHE: EngineCache
+"""Persistent (SQLite) key/value cache that deletes its values after ``expire``
+seconds."""
 
 
-def init(engine_settings=None):  # pylint: disable=unused-argument
-    obtain_token()
+def init(engine_settings):
+    global CACHE  # pylint: disable=global-statement
+    CACHE = EngineCache(engine_settings["name"])  # type:ignore
+
+
+def obtain_token() -> str:
+    token = CACHE.get(key="token")
+    if token is None:
+        resp = http_get('https://www.wolframalpha.com/input/api/v1/code?ts=9999999999999999999', timeout=2.0)
+        token = resp.json()["code"]
+        # seems, wolframalpha resets its token in every hour
+        CACHE.set(key="code", value=token, expire=3600)
+    return token
 
 
-# do search-request
 def request(query, params):
-    # obtain token if last update was more than an hour
-    if time() - (token['last_updated'] or 0) > 3600:
-        obtain_token()
-    params['url'] = search_url.format(query=urlencode({'input': query}), token=token['value'])
+    token = obtain_token()
+    params['url'] = search_url.format(query=urlencode({'input': query}), token=token)
     params['headers']['Referer'] = referer_url.format(query=urlencode({'i': query}))
 
     return params
 
 
-# get response from search-request
 def response(resp):
     results = []