Redis Library¶
A collection of convenient functions and redis/lua scripts.
This code was partial inspired by the Bullet-Proofing Lua Scripts in RedisPy article.
- searx.redislib.drop_counter(client, name)[source]¶
Drop counter with redis key
SearXNG_counter_<name>
The replacement
<name>
is a secret hash of the value from argumentname
(seeincr_counter()
andincr_sliding_window()
).
- searx.redislib.incr_counter(client, name: str, limit: int = 0, expire: int = 0)[source]¶
Increment a counter and return the new value.
If counter with redis key
SearXNG_counter_<name>
does not exists it is created with initial value 1 returned. The replacement<name>
is a secret hash of the value from argumentname
(seesecret_hash()
).The implementation of the redis counter is the lua script from string
INCR_COUNTER
.- Parameters:
- Returns:
value of the incremented counter
A simple demo of a counter with expire time and limit:
>>> for i in range(6): ... i, incr_counter(client, "foo", 3, 5) # max 3, duration 5 sec ... time.sleep(1) # from the third call on max has been reached ... (0, 1) (1, 2) (2, 3) (3, 3) (4, 3) (5, 1)
- searx.redislib.incr_sliding_window(client, name: str, duration: int)[source]¶
Increment a sliding-window counter and return the new value.
If counter with redis key
SearXNG_counter_<name>
does not exists it is created with initial value 1 returned. The replacement<name>
is a secret hash of the value from argumentname
(seesecret_hash()
).- Parameters:
name (str) – name of the counter
duration – live-time of the sliding window in seconds
- Typeduration:
int
- Returns:
value of the incremented counter
The implementation of the redis counter is the lua script from string
INCR_SLIDING_WINDOW
. The lua script uses sorted sets in Redis to implement a sliding window for the redis keySearXNG_counter_<name>
(ZADD). The current TIME is used to score the items in the sorted set and the time window is moved by removing items with a score lower current time minus duration time (ZREMRANGEBYSCORE).The EXPIRE time (the duration of the sliding window) is refreshed on each call (increment) and if there is no call in this duration, the sorted set expires from the redis DB.
The return value is the amount of items in the sorted set (ZCOUNT), what means the number of calls in the sliding window.
A simple demo of the sliding window:
>>> for i in range(5): ... incr_sliding_window(client, "foo", 3) # duration 3 sec ... time.sleep(1) # from the third call (second) on the window is moved ... 1 2 3 3 3 >>> time.sleep(3) # wait until expire >>> incr_sliding_window(client, "foo", 3) 1
- searx.redislib.lua_script_storage(client, script)[source]¶
Returns a redis
Script
instance.Due to performance reason the
Script
object is instantiated only once for a client (client.register_script(..)
) and is cached inLUA_SCRIPT_STORAGE
.
- searx.redislib.purge_by_prefix(client, prefix: str = 'SearXNG_')[source]¶
Purge all keys with
prefix
from database.Queries all keys in the database by the given prefix and set expire time to zero. The default prefix will drop all keys which has been set by SearXNG (drops SearXNG schema entirely from database).
The implementation is the lua script from string
PURGE_BY_PREFIX
. The lua script uses EXPIRE instead of DEL: if there are a lot keys to delete and/or their values are big, DEL could take more time and blocks the command loop while EXPIRE turns back immediate.- Parameters:
prefix – prefix of the key to delete (default:
SearXNG_
)
- searx.redislib.secret_hash(name: str)[source]¶
Creates a hash of the
name
.Combines argument
name
with thesecret_key
from server:. This function can be used to get a more anonymized name of a Redis KEY.- Parameters:
name (str) – the name to create a secret hash for
- searx.redislib.LUA_SCRIPT_STORAGE = {}¶
A global dictionary to cache client’s
Script
objects, used bylua_script_storage