[Fix] Try harder to clean pending bucket

Issue: #4467

1 files changed, 29 insertions, 0 deletions

diff --git a/lualib/redis_scripts/ratelimit_cleanup_pending.lua b/lualib/redis_scripts/ratelimit_cleanup_pending.lua
new file mode 100644
index 000000000..f51599b09
--- /dev/null
+++ b/lualib/redis_scripts/ratelimit_cleanup_pending.lua
@@ -0,0 +1,29 @@
+-- This script cleans up the pending requests in Redis.
+
+-- KEYS: Input parameters
+-- KEYS[1] - prefix: The Redis key prefix used to store the bucket information.
+-- KEYS[2] - now: The current time in milliseconds.
+-- KEYS[3] - expire: The expiration time for the Redis key storing the bucket information, in seconds.
+-- KEYS[4] - number_of_recipients: The number of requests to be allowed (or the increase rate).
+
+-- 1. Retrieve the last hit time and initialize variables
+local prefix = KEYS[1]
+local last = redis.call('HGET', prefix, 'l')
+local nrcpt = tonumber(KEYS[4])
+if not last then
+  -- No bucket, no cleanup
+  return 0
+end
+
+
+-- 2. Update the pending values based on the number of recipients (requests)
+local pending = redis.call('HGET', prefix, 'p')
+pending = tonumber(pending or '0')
+if pending < nrcpt then pending = 0 else pending = pending - nrcpt end
+
+-- 3. Set the updated values back to Redis and update the expiration time for the bucket
+redis.call('HMSET', prefix, tostring(pending), 'l', KEYS[2])
+redis.call('EXPIRE', prefix, KEYS[3])
+
+-- 4. Return the updated pending value
+return pending
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