maybe next step

Author: sanderegg

packages/service-library/src/servicelib/redis/lua/register_semaphore_holder.lua

@@ -0,0 +1,42 @@
+-- Simple token initialization and management for Python BRPOP
+-- KEYS[1]: tokens_key (LIST of available tokens)
+-- KEYS[2]: holders_key (SET of current holder instance IDs)
+-- KEYS[3]: holder_key (individual holder TTL key for this instance)
+-- ARGV[1]: instance_id
+-- ARGV[2]: capacity (max concurrent holders)
+-- ARGV[3]: ttl_seconds
+-- ARGV[4]: token (the token received from BRPOP)
+--
+-- Returns: {exit_code, status, current_count}
+-- exit_code: 0 if registered successfully
+
+local tokens_key = KEYS[1]
+local holders_key = KEYS[2]
+local holder_key = KEYS[3]
+
+local instance_id = ARGV[1]
+local capacity = tonumber(ARGV[2])
+local ttl_seconds = tonumber(ARGV[3])
+local token = ARGV[4]
+
+-- Step 1: Initialize token pool if needed (first time setup)
+local tokens_exist = redis.call('EXISTS', tokens_key)
+if tokens_exist == 0 then
+    -- Initialize with capacity number of tokens
+    for i = 1, capacity do
+        redis.call('LPUSH', tokens_key, 'token_' .. i)
+    end
+    -- Set expiry on tokens list to prevent infinite growth
+    redis.call('EXPIRE', tokens_key, ttl_seconds * 10)
+end
+
+-- Step 2: Register as holder (token was already popped by Python BRPOP)
+redis.call('SADD', holders_key, instance_id)
+redis.call('SETEX', holder_key, ttl_seconds, token)
+
+-- Step 3: Set expiry on holders set to prevent infinite growth
+redis.call('EXPIRE', holders_key, ttl_seconds * 10)
+
+local current_count = redis.call('SCARD', holders_key)
+
+return {0, 'registered', current_count}