I may be missing something but I think this could be done more cleanly with an atomic counter or semaphore [1] in Redis.

  1. Have a task that releases 1 resource to the semaphore    
     every (1.0 / cps) seconds.

  2. Workers wait to acquire a resource from the semaphore 
     before making a call.

Due to the rate of release being fixed at 1/cps no worker can ever exceed the calls-per-second limit. Much simpler than sending Lua over the wire.

[1] https://github.com/dv/redis-semaphore