forked from zaclys/searxng
Merge pull request #1047 from return42/redis-lib
Add a redis library to generalize DB functions we need in SearXNG.
This commit is contained in:
Alexandre Flament
GitHub
commit
ea0cddba0b
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@ -139,6 +139,7 @@ intersphinx_mapping = {
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"jinja": ("https://jinja.palletsprojects.com/", None),
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"linuxdoc" : ("https://return42.github.io/linuxdoc/", None),
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"sphinx" : ("https://www.sphinx-doc.org/en/master/", None),
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"redis": ('https://redis.readthedocs.io/en/stable/', None),
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}
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issues_github_path = "searxng/searxng"
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@ -0,0 +1,8 @@
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.. _searx.redis:
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=============
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Redis Library
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=============
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.. automodule:: searx.redislib
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:members:
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@ -13,11 +13,11 @@ Enable the plugin in ``settings.yml``:
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- ``redis.url: ...`` check the value, see :ref:`settings redis`
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"""
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import hmac
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import re
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from flask import request
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from searx.shared import redisdb
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from searx.redislib import incr_sliding_window
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name = "Request limiter"
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description = "Limit the number of request"
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@ -36,8 +36,9 @@ re_bot = re.compile(
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)
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def is_accepted_request(inc_get_counter) -> bool:
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def is_accepted_request() -> bool:
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# pylint: disable=too-many-return-statements
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redis_client = redisdb.client()
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user_agent = request.headers.get('User-Agent', '')
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x_forwarded_for = request.headers.get('X-Forwarded-For', '')
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@ -47,70 +48,45 @@ def is_accepted_request(inc_get_counter) -> bool:
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return True
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if request.path == '/search':
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c_burst = inc_get_counter(interval=20, keys=[b'IP limit, burst', x_forwarded_for])
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c_10min = inc_get_counter(interval=600, keys=[b'IP limit, 10 minutes', x_forwarded_for])
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c_burst = incr_sliding_window(redis_client, 'IP limit, burst' + x_forwarded_for, 20)
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c_10min = incr_sliding_window(redis_client, 'IP limit, 10 minutes' + x_forwarded_for, 600)
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if c_burst > 15 or c_10min > 150:
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logger.debug("to many request") # pylint: disable=undefined-variable
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return False
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if re_bot.match(user_agent):
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logger.debug("detected bot") # pylint: disable=undefined-variable
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return False
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if len(request.headers.get('Accept-Language', '').strip()) == '':
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logger.debug("missing Accept-Language") # pylint: disable=undefined-variable
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return False
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if request.headers.get('Connection') == 'close':
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logger.debug("got Connection=close") # pylint: disable=undefined-variable
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return False
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accept_encoding_list = [l.strip() for l in request.headers.get('Accept-Encoding', '').split(',')]
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if 'gzip' not in accept_encoding_list or 'deflate' not in accept_encoding_list:
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logger.debug("suspicious Accept-Encoding") # pylint: disable=undefined-variable
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return False
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if 'text/html' not in request.accept_mimetypes:
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logger.debug("Accept-Encoding misses text/html") # pylint: disable=undefined-variable
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return False
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if request.args.get('format', 'html') != 'html':
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c = inc_get_counter(interval=3600, keys=[b'API limit', x_forwarded_for])
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c = incr_sliding_window(redis_client, 'API limit' + x_forwarded_for, 3600)
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if c > 4:
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logger.debug("API limit exceeded") # pylint: disable=undefined-variable
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return False
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return True
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def create_inc_get_counter(redis_client, secret_key_bytes):
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lua_script = """
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local slidingWindow = KEYS[1]
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local key = KEYS[2]
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local now = tonumber(redis.call('TIME')[1])
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local id = redis.call('INCR', 'counter')
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if (id > 2^46)
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then
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redis.call('SET', 'count', 0)
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end
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redis.call('ZREMRANGEBYSCORE', key, 0, now - slidingWindow)
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redis.call('ZADD', key, now, id)
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local result = redis.call('ZCOUNT', key, 0, now+1)
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redis.call('EXPIRE', key, slidingWindow)
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return result
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"""
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script_sha = redis_client.script_load(lua_script)
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def inc_get_counter(interval, keys):
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m = hmac.new(secret_key_bytes, digestmod='sha256')
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for k in keys:
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m.update(bytes(str(k), encoding='utf-8') or b'')
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m.update(b"\0")
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key = m.digest()
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return redis_client.evalsha(script_sha, 2, interval, key)
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return inc_get_counter
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def create_pre_request(get_aggregation_count):
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def pre_request():
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if not is_accepted_request(get_aggregation_count):
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return '', 429
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return None
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return pre_request
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def pre_request():
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if not is_accepted_request():
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return '', 429
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return None
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def init(app, settings):
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@ -122,8 +98,5 @@ def init(app, settings):
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logger.error("init limiter DB failed!!!") # pylint: disable=undefined-variable
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return False
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redis_client = redisdb.client()
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secret_key_bytes = bytes(settings['server']['secret_key'], encoding='utf-8')
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inc_get_counter = create_inc_get_counter(redis_client, secret_key_bytes)
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app.before_request(create_pre_request(inc_get_counter))
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app.before_request(pre_request)
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return True
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@ -0,0 +1,241 @@
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# SPDX-License-Identifier: AGPL-3.0-or-later
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# lint: pylint
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"""A collection of convenient functions and redis/lua scripts.
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This code was partial inspired by the `Bullet-Proofing Lua Scripts in RedisPy`_
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article.
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.. _Bullet-Proofing Lua Scripts in RedisPy:
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https://redis.com/blog/bullet-proofing-lua-scripts-in-redispy/
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"""
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import hmac
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from searx import get_setting
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LUA_SCRIPT_STORAGE = {}
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"""A global dictionary to cache client's ``Script`` objects, used by
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:py:obj:`lua_script_storage`"""
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def lua_script_storage(client, script):
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"""Returns a redis :py:obj:`Script
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<redis.commands.core.CoreCommands.register_script>` instance.
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Due to performance reason the ``Script`` object is instantiated only once
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for a client (``client.register_script(..)``) and is cached in
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:py:obj:`LUA_SCRIPT_STORAGE`.
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"""
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# redis connection can be closed, lets use the id() of the redis connector
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# as key in the script-storage:
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client_id = id(client)
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if LUA_SCRIPT_STORAGE.get(client_id) is None:
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LUA_SCRIPT_STORAGE[client_id] = {}
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if LUA_SCRIPT_STORAGE[client_id].get(script) is None:
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LUA_SCRIPT_STORAGE[client_id][script] = client.register_script(script)
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return LUA_SCRIPT_STORAGE[client_id][script]
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PURGE_BY_PREFIX = """
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local prefix = tostring(ARGV[1])
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for i, name in ipairs(redis.call('KEYS', prefix .. '*')) do
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redis.call('EXPIRE', name, 0)
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end
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"""
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def purge_by_prefix(client, prefix: str = "SearXNG_"):
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"""Purge all keys with ``prefix`` from database.
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Queries all keys in the database by the given prefix and set expire time to
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zero. The default prefix will drop all keys which has been set by SearXNG
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(drops SearXNG schema entirely from database).
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The implementation is the lua script from string :py:obj:`PURGE_BY_PREFIX`.
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The lua script uses EXPIRE_ instead of DEL_: if there are a lot keys to
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delete and/or their values are big, `DEL` could take more time and blocks
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the command loop while `EXPIRE` turns back immediate.
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:param prefix: prefix of the key to delete (default: ``SearXNG_``)
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:type name: str
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.. _EXPIRE: https://redis.io/commands/expire/
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.. _DEL: https://redis.io/commands/del/
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"""
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script = lua_script_storage(client, PURGE_BY_PREFIX)
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script(args=[prefix])
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def secret_hash(name: str):
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"""Creates a hash of the ``name``.
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Combines argument ``name`` with the ``secret_key`` from :ref:`settings
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server`. This function can be used to get a more anonymised name of a Redis
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KEY.
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:param name: the name to create a secret hash for
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:type name: str
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"""
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m = hmac.new(bytes(name, encoding='utf-8'), digestmod='sha256')
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m.update(bytes(get_setting('server.secret_key'), encoding='utf-8'))
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return m.hexdigest()
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INCR_COUNTER = """
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local limit = tonumber(ARGV[1])
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local expire = tonumber(ARGV[2])
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local c_name = KEYS[1]
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local c = redis.call('GET', c_name)
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if not c then
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c = redis.call('INCR', c_name)
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if expire > 0 then
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redis.call('EXPIRE', c_name, expire)
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end
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else
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c = tonumber(c)
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if limit == 0 or c < limit then
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c = redis.call('INCR', c_name)
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end
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end
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return c
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"""
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def incr_counter(client, name: str, limit: int = 0, expire: int = 0):
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"""Increment a counter and return the new value.
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If counter with redis key ``SearXNG_counter_<name>`` does not exists it is
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created with initial value 1 returned. The replacement ``<name>`` is a
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*secret hash* of the value from argument ``name`` (see
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:py:func:`secret_hash`).
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The implementation of the redis counter is the lua script from string
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:py:obj:`INCR_COUNTER`.
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:param name: name of the counter
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:type name: str
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:param expire: live-time of the counter in seconds (default ``None`` means
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infinite).
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:type expire: int / see EXPIRE_
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:param limit: limit where the counter stops to increment (default ``None``)
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:type limit: int / limit is 2^64 see INCR_
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:return: value of the incremented counter
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:type return: int
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.. _EXPIRE: https://redis.io/commands/expire/
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.. _INCR: https://redis.io/commands/incr/
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A simple demo of a counter with expire time and limit::
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>>> for i in range(6):
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... i, incr_counter(client, "foo", 3, 5) # max 3, duration 5 sec
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... time.sleep(1) # from the third call on max has been reached
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...
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(0, 1)
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(1, 2)
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(2, 3)
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(3, 3)
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(4, 3)
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(5, 1)
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"""
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script = lua_script_storage(client, INCR_COUNTER)
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name = "SearXNG_counter_" + secret_hash(name)
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c = script(args=[limit, expire], keys=[name])
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return c
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def drop_counter(client, name):
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"""Drop counter with redis key ``SearXNG_counter_<name>``
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The replacement ``<name>`` is a *secret hash* of the value from argument
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``name`` (see :py:func:`incr_counter` and :py:func:`incr_sliding_window`).
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"""
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name = "SearXNG_counter_" + secret_hash(name)
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client.delete(name)
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INCR_SLIDING_WINDOW = """
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local expire = tonumber(ARGV[1])
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local name = KEYS[1]
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local current_time = redis.call('TIME')
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redis.call('ZREMRANGEBYSCORE', name, 0, current_time[1] - expire)
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redis.call('ZADD', name, current_time[1], current_time[1] .. current_time[2])
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local result = redis.call('ZCOUNT', name, 0, current_time[1] + 1)
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redis.call('EXPIRE', name, expire)
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return result
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"""
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def incr_sliding_window(client, name: str, duration: int):
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"""Increment a sliding-window counter and return the new value.
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If counter with redis key ``SearXNG_counter_<name>`` does not exists it is
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created with initial value 1 returned. The replacement ``<name>`` is a
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*secret hash* of the value from argument ``name`` (see
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:py:func:`secret_hash`).
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:param name: name of the counter
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:type name: str
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:param duration: live-time of the sliding window in seconds
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:typeduration: int
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:return: value of the incremented counter
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:type return: int
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The implementation of the redis counter is the lua script from string
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:py:obj:`INCR_SLIDING_WINDOW`. The lua script uses `sorted sets in Redis`_
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to implement a sliding window for the redis key ``SearXNG_counter_<name>``
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(ZADD_). The current TIME_ is used to score the items in the sorted set and
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the time window is moved by removing items with a score lower current time
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minus *duration* time (ZREMRANGEBYSCORE_).
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The EXPIRE_ time (the duration of the sliding window) is refreshed on each
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call (incrementation) and if there is no call in this duration, the sorted
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set expires from the redis DB.
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The return value is the amount of items in the sorted set (ZCOUNT_), what
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means the number of calls in the sliding window.
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.. _Sorted sets in Redis:
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https://redis.com/ebook/part-1-getting-started/chapter-1-getting-to-know-redis/1-2-what-redis-data-structures-look-like/1-2-5-sorted-sets-in-redis/
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.. _TIME: https://redis.io/commands/time/
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.. _ZADD: https://redis.io/commands/zadd/
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.. _EXPIRE: https://redis.io/commands/expire/
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.. _ZREMRANGEBYSCORE: https://redis.io/commands/zremrangebyscore/
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.. _ZCOUNT: https://redis.io/commands/zcount/
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A simple demo of the sliding window::
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>>> for i in range(5):
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... incr_sliding_window(client, "foo", 3) # duration 3 sec
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... time.sleep(1) # from the third call (second) on the window is moved
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...
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1
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2
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3
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3
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3
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>>> time.sleep(3) # wait until expire
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>>> incr_sliding_window(client, "foo", 3)
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1
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"""
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script = lua_script_storage(client, INCR_SLIDING_WINDOW)
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name = "SearXNG_counter_" + secret_hash(name)
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c = script(args=[duration], keys=[name])
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return c
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