Add new INFO evicted_scripts field and eval scripts eviction (#2686)

Co-authored-by: Oran Agra <[email protected]>

Author: enjoy-binbin

commands/eval.md

@@ -12,6 +12,12 @@ to ensure the correct execution of scripts, both in standalone and clustered dep
 The script **should only** access keys whose names are given as input arguments.
 Scripts **should never** access keys with programmatically-generated names or based on the contents of data structures stored in the database.
 
+**Note:**
+in some cases, users will abuse Lua EVAL by embedding values in the script instead of providing them as argument, and thus generating a different script on each call to EVAL.
+These are added to the Lua interpreter and cached to redis-server, consuming a large amount of memory over time.
+Starting from Redis 8.0, scripts loaded with `EVAL` or `EVAL_RO` will be deleted from redis after a certain number (least recently used order).
+The number of evicted scripts can be viewed through `INFO`'s `evicted_scripts`.
+
 Please refer to the [Redis Programmability](/topics/programmability) and [Introduction to Eval Scripts](/topics/eval-intro) for more information about Lua scripts.
 
 @examples

commands/info.md

@@ -276,6 +276,7 @@ Here is the meaning of all fields in the **stats** section:
 *   `expire_cycle_cpu_milliseconds`: The cumulative amount of time spent on active expiry cycles
 *   `evicted_keys`: Number of evicted keys due to `maxmemory` limit
 *   `evicted_clients`: Number of evicted clients due to `maxmemory-clients` limit. Added in Redis 7.0.
+*   `evicted_scripts`: Number of evicted EVAL scripts due to LRU policy, see `EVAL` for more details. Added in Redis 8.0.
 *   `total_eviction_exceeded_time`:  Total time `used_memory` was greater than `maxmemory` since server startup, in milliseconds
 *   `current_eviction_exceeded_time`: The time passed since `used_memory` last rose above `maxmemory`, in milliseconds
 *   `keyspace_hits`: Number of successful lookup of keys in the main dictionary