-- | Connection pool configuration.
module Arbiter.Core.PoolConfig
  ( PoolConfig (..)
  , defaultPoolConfig
  , poolConfigForWorkers
  ) where

-- | Connection pool configuration.
data PoolConfig = PoolConfig
  { PoolConfig -> Int
poolSize :: Int
  -- ^ Maximum connections
  , PoolConfig -> Int
poolIdleTimeout :: Int
  -- ^ Idle timeout (seconds)
  , PoolConfig -> Maybe Int
poolStripes :: Maybe Int
  -- ^ Number of stripes (sub-pools). Reduces lock contention on connection checkout.
  --
  -- * @Nothing@: Auto-detect based on CPU count
  -- * @Just n@: Use n stripes
  }
  deriving stock (PoolConfig -> PoolConfig -> Bool
(PoolConfig -> PoolConfig -> Bool)
-> (PoolConfig -> PoolConfig -> Bool) -> Eq PoolConfig
forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
$c== :: PoolConfig -> PoolConfig -> Bool
== :: PoolConfig -> PoolConfig -> Bool
$c/= :: PoolConfig -> PoolConfig -> Bool
/= :: PoolConfig -> PoolConfig -> Bool
Eq, Int -> PoolConfig -> ShowS
[PoolConfig] -> ShowS
PoolConfig -> String
(Int -> PoolConfig -> ShowS)
-> (PoolConfig -> String)
-> ([PoolConfig] -> ShowS)
-> Show PoolConfig
forall a.
(Int -> a -> ShowS) -> (a -> String) -> ([a] -> ShowS) -> Show a
$cshowsPrec :: Int -> PoolConfig -> ShowS
showsPrec :: Int -> PoolConfig -> ShowS
$cshow :: PoolConfig -> String
show :: PoolConfig -> String
$cshowList :: [PoolConfig] -> ShowS
showList :: [PoolConfig] -> ShowS
Show)

-- | 10 connections, 300s idle timeout, 1 stripe. For workers, use 'poolConfigForWorkers'.
defaultPoolConfig :: PoolConfig
defaultPoolConfig :: PoolConfig
defaultPoolConfig =
  PoolConfig
    { poolSize :: Int
poolSize = Int
10
    , poolIdleTimeout :: Int
poolIdleTimeout = Int
300
    , poolStripes :: Maybe Int
poolStripes = Int -> Maybe Int
forall a. a -> Maybe a
Just Int
1
    }

-- | Pool sized for a worker pool of @workerCnt@ threads.
--
-- Returns a single-stripe pool with @2 * workerCnt@ connections (floor of 2).
--
-- A single stripe is intentional. @Data.Pool.withResource@ pins each thread
-- to one stripe based on its capability and does not search other stripes
-- when its own is exhausted. With multiple stripes, threads from the same
-- worker pool can cluster on one stripe and starve it of free connections
-- even when other stripes are idle.
poolConfigForWorkers :: Int -> PoolConfig
poolConfigForWorkers :: Int -> PoolConfig
poolConfigForWorkers Int
workerCnt =
  PoolConfig
    { poolSize :: Int
poolSize = Int -> Int -> Int
forall a. Ord a => a -> a -> a
max Int
2 (Int
2 Int -> Int -> Int
forall a. Num a => a -> a -> a
* Int
workerCnt)
    , poolIdleTimeout :: Int
poolIdleTimeout = Int
300
    , poolStripes :: Maybe Int
poolStripes = Int -> Maybe Int
forall a. a -> Maybe a
Just Int
1
    }