yaml-rpc-0.1: Network/YAML/Balancer.hs

module Network.YAML.Balancer where

import System.Random
import qualified Data.ByteString.Char8 as BS

type Server = (BS.ByteString, Int)

-- | Select random server
selectRandom :: [(BS.ByteString, Server, Int)]   -- ^ [(Service name, (hostname, port number), priority)]
             -> BS.ByteString                    -- ^ Service name
             -> IO Server
selectRandom lst service = do
  let lst' = concatMap (\(name,srv,p) -> replicate p (name, srv)) lst
      lst'' = map snd $ filter (\(name,srv) -> name==service) lst'
      n = length lst''
  k <- randomRIO (0, n-1)
  return $ lst'' !! k