diff --git a/CHANGELOG.md b/CHANGELOG.md new file mode 100644 --- /dev/null +++ b/CHANGELOG.md @@ -0,0 +1,39 @@ +# resource-pool-0.5.0.1 (2026-07-08) +* Fix a bug where a thread waiting for a resource would get stuck in the queue + indefinitely if resource creation failed in another thread. +* Fix a potential out-of-bounds array access in stripe selection when the hash + of a thread id is negative. +* Fix a bug where some of the stripes would never be used if the number of + stripes was larger than the number of capabilities. +* Add a test suite. + +# resource-pool-0.5.0.0 (2025-06-13) +* Drop support for GHC < 8.10. +* Use STM based lockless implementation as it results in much better throughput + in a multi-threaded environment when number of stripes is not equal to the + number of capabilities (in particular with a single stripe). +* Stop running resource freeing functions within `uninterruptibleMask`. +* `destroyResource` no longer ignores exceptions thrown from resource releasing + functions. +* Change the default number of stripes to 1. +* Do not exceed the maximum number of resources if the number of stripes does + not divide it. +* Add support for assigning a label to the pool. + +# resource-pool-0.4.0.0 (2023-01-16) +* Require `poolMaxResources` to be not smaller than the number of stripes. +* Add support for setting the number of stripes. +* Hide the constructor of `PoolConfig` from the public API and provide + `defaultPoolConfig` so that future additions to `PoolConfig` don't require + major version bumps. + +# resource-pool-0.3.1.0 (2022-06-15) +* Add `tryWithResource` and `tryTakeResource`. + +# resource-pool-0.3.0.0 (2022-06-01) +* Rewrite based on `Control.Concurrent.QSem` for better throughput and latency. +* Make release of resources asynchronous exceptions safe. +* Remove dependency on `monad-control`. +* Expose the `.Internal` module. +* Add support for introspection. +* Add `PoolConfig`. diff --git a/Data/Pool.hs b/Data/Pool.hs deleted file mode 100644 --- a/Data/Pool.hs +++ /dev/null @@ -1,393 +0,0 @@ -{-# LANGUAGE CPP, NamedFieldPuns, RecordWildCards, ScopedTypeVariables, RankNTypes, DeriveDataTypeable #-} - -#if MIN_VERSION_monad_control(0,3,0) -{-# LANGUAGE FlexibleContexts #-} -#endif - -#if !MIN_VERSION_base(4,3,0) -{-# LANGUAGE RankNTypes #-} -#endif - --- | --- Module: Data.Pool --- Copyright: (c) 2011 MailRank, Inc. --- License: BSD3 --- Maintainer: Bryan O'Sullivan , --- Bas van Dijk --- Stability: experimental --- Portability: portable --- --- A high-performance striped pooling abstraction for managing --- flexibly-sized collections of resources such as database --- connections. --- --- \"Striped\" means that a single 'Pool' consists of several --- sub-pools, each managed independently. A single stripe is fine for --- many applications, and probably what you should choose by default. --- More stripes will lead to reduced contention in high-performance --- multicore applications, at a trade-off of causing the maximum --- number of simultaneous resources in use to grow. -module Data.Pool - ( - Pool(idleTime, maxResources, numStripes) - , LocalPool - , createPool - , withResource - , takeResource - , tryWithResource - , tryTakeResource - , destroyResource - , putResource - , destroyAllResources - ) where - -import Control.Applicative ((<$>)) -import Control.Concurrent (ThreadId, forkIOWithUnmask, killThread, myThreadId, threadDelay) -import Control.Concurrent.STM -import Control.Exception (SomeException, onException, mask_) -import Control.Monad (forM_, forever, join, liftM3, unless, when) -import Data.Hashable (hash) -import Data.IORef (IORef, newIORef, mkWeakIORef) -import Data.List (partition) -import Data.Time.Clock (NominalDiffTime, UTCTime, diffUTCTime, getCurrentTime) -import Data.Typeable (Typeable) -import GHC.Conc.Sync (labelThread) -import qualified Control.Exception as E -import qualified Data.Vector as V - -#if MIN_VERSION_monad_control(0,3,0) -import Control.Monad.Trans.Control (MonadBaseControl, control) -import Control.Monad.Base (liftBase) -#else -import Control.Monad.IO.Control (MonadControlIO, controlIO) -import Control.Monad.IO.Class (liftIO) -#define control controlIO -#define liftBase liftIO -#endif - -#if MIN_VERSION_base(4,3,0) -import Control.Exception (mask) -#else --- Don't do any async exception protection for older GHCs. -mask :: ((forall a. IO a -> IO a) -> IO b) -> IO b -mask f = f id -#endif - --- | A single resource pool entry. -data Entry a = Entry { - entry :: a - , lastUse :: UTCTime - -- ^ Time of last return. - } - --- | A single striped pool. -data LocalPool a = LocalPool { - inUse :: TVar Int - -- ^ Count of open entries (both idle and in use). - , entries :: TVar [Entry a] - -- ^ Idle entries. - , lfin :: IORef () - -- ^ empty value used to attach a finalizer to (internal) - } deriving (Typeable) - -data Pool a = Pool { - create :: IO a - -- ^ Action for creating a new entry to add to the pool. - , destroy :: a -> IO () - -- ^ Action for destroying an entry that is now done with. - , numStripes :: Int - -- ^ The number of stripes (distinct sub-pools) to maintain. - -- The smallest acceptable value is 1. - , idleTime :: NominalDiffTime - -- ^ Amount of time for which an unused resource is kept alive. - -- The smallest acceptable value is 0.5 seconds. - -- - -- The elapsed time before closing may be a little longer than - -- requested, as the reaper thread wakes at 1-second intervals. - , maxResources :: Int - -- ^ Maximum number of resources to maintain per stripe. The - -- smallest acceptable value is 1. - -- - -- Requests for resources will block if this limit is reached on a - -- single stripe, even if other stripes have idle resources - -- available. - , localPools :: V.Vector (LocalPool a) - -- ^ Per-capability resource pools. - , fin :: IORef () - -- ^ empty value used to attach a finalizer to (internal) - } deriving (Typeable) - -instance Show (Pool a) where - show Pool{..} = "Pool {numStripes = " ++ show numStripes ++ ", " ++ - "idleTime = " ++ show idleTime ++ ", " ++ - "maxResources = " ++ show maxResources ++ "}" - --- | Create a striped resource pool. --- --- Although the garbage collector will destroy all idle resources when --- the pool is garbage collected it's recommended to manually --- 'destroyAllResources' when you're done with the pool so that the --- resources are freed up as soon as possible. -createPool - :: IO a - -- ^ Action that creates a new resource. - -> (a -> IO ()) - -- ^ Action that destroys an existing resource. - -> Int - -- ^ The number of stripes (distinct sub-pools) to maintain. - -- The smallest acceptable value is 1. - -> NominalDiffTime - -- ^ Amount of time for which an unused resource is kept open. - -- The smallest acceptable value is 0.5 seconds. - -- - -- The elapsed time before destroying a resource may be a little - -- longer than requested, as the reaper thread wakes at 1-second - -- intervals. - -> Int - -- ^ Maximum number of resources to keep open per stripe. The - -- smallest acceptable value is 1. - -- - -- Requests for resources will block if this limit is reached on a - -- single stripe, even if other stripes have idle resources - -- available. - -> IO (Pool a) -createPool create destroy numStripes idleTime maxResources = do - when (numStripes < 1) $ - modError "pool " $ "invalid stripe count " ++ show numStripes - when (idleTime < 0.5) $ - modError "pool " $ "invalid idle time " ++ show idleTime - when (maxResources < 1) $ - modError "pool " $ "invalid maximum resource count " ++ show maxResources - localPools <- V.replicateM numStripes $ - liftM3 LocalPool (newTVarIO 0) (newTVarIO []) (newIORef ()) - reaperId <- forkIOLabeledWithUnmask "resource-pool: reaper" $ \unmask -> - unmask $ reaper destroy idleTime localPools - fin <- newIORef () - let p = Pool { - create - , destroy - , numStripes - , idleTime - , maxResources - , localPools - , fin - } - mkWeakIORef fin (killThread reaperId) >> - V.mapM_ (\lp -> mkWeakIORef (lfin lp) (purgeLocalPool destroy lp)) localPools - return p - --- TODO: Propose 'forkIOLabeledWithUnmask' for the base library. - --- | Sparks off a new thread using 'forkIOWithUnmask' to run the given --- IO computation, but first labels the thread with the given label --- (using 'labelThread'). --- --- The implementation makes sure that asynchronous exceptions are --- masked until the given computation is executed. This ensures the --- thread will always be labeled which guarantees you can always --- easily find it in the GHC event log. --- --- Like 'forkIOWithUnmask', the given computation is given a function --- to unmask asynchronous exceptions. See the documentation of that --- function for the motivation of this. --- --- Returns the 'ThreadId' of the newly created thread. -forkIOLabeledWithUnmask :: String - -> ((forall a. IO a -> IO a) -> IO ()) - -> IO ThreadId -forkIOLabeledWithUnmask label m = mask_ $ forkIOWithUnmask $ \unmask -> do - tid <- myThreadId - labelThread tid label - m unmask - --- | Periodically go through all pools, closing any resources that --- have been left idle for too long. -reaper :: (a -> IO ()) -> NominalDiffTime -> V.Vector (LocalPool a) -> IO () -reaper destroy idleTime pools = forever $ do - threadDelay (1 * 1000000) - now <- getCurrentTime - let isStale Entry{..} = now `diffUTCTime` lastUse > idleTime - V.forM_ pools $ \LocalPool{..} -> do - resources <- atomically $ do - (stale,fresh) <- partition isStale <$> readTVar entries - unless (null stale) $ do - writeTVar entries fresh - modifyTVar_ inUse (subtract (length stale)) - return (map entry stale) - forM_ resources $ \resource -> do - destroy resource `E.catch` \(_::SomeException) -> return () - --- | Destroy all idle resources of the given 'LocalPool' and remove them from --- the pool. -purgeLocalPool :: (a -> IO ()) -> LocalPool a -> IO () -purgeLocalPool destroy LocalPool{..} = do - resources <- atomically $ do - idle <- swapTVar entries [] - modifyTVar_ inUse (subtract (length idle)) - return (map entry idle) - forM_ resources $ \resource -> - destroy resource `E.catch` \(_::SomeException) -> return () - --- | Temporarily take a resource from a 'Pool', perform an action with --- it, and return it to the pool afterwards. --- --- * If the pool has an idle resource available, it is used --- immediately. --- --- * Otherwise, if the maximum number of resources has not yet been --- reached, a new resource is created and used. --- --- * If the maximum number of resources has been reached, this --- function blocks until a resource becomes available. --- --- If the action throws an exception of any type, the resource is --- destroyed, and not returned to the pool. --- --- It probably goes without saying that you should never manually --- destroy a pooled resource, as doing so will almost certainly cause --- a subsequent user (who expects the resource to be valid) to throw --- an exception. -withResource :: -#if MIN_VERSION_monad_control(0,3,0) - (MonadBaseControl IO m) -#else - (MonadControlIO m) -#endif - => Pool a -> (a -> m b) -> m b -{-# SPECIALIZE withResource :: Pool a -> (a -> IO b) -> IO b #-} -withResource pool act = control $ \runInIO -> mask $ \restore -> do - (resource, local) <- takeResource pool - ret <- restore (runInIO (act resource)) `onException` - destroyResource pool local resource - putResource local resource - return ret -#if __GLASGOW_HASKELL__ >= 700 -{-# INLINABLE withResource #-} -#endif - --- | Take a resource from the pool, following the same results as --- 'withResource'. Note that this function should be used with caution, as --- improper exception handling can lead to leaked resources. --- --- This function returns both a resource and the @LocalPool@ it came from so --- that it may either be destroyed (via 'destroyResource') or returned to the --- pool (via 'putResource'). -takeResource :: Pool a -> IO (a, LocalPool a) -takeResource pool@Pool{..} = do - local@LocalPool{..} <- getLocalPool pool - resource <- liftBase . join . atomically $ do - ents <- readTVar entries - case ents of - (Entry{..}:es) -> writeTVar entries es >> return (return entry) - [] -> do - used <- readTVar inUse - when (used == maxResources) retry - writeTVar inUse $! used + 1 - return $ - create `onException` atomically (modifyTVar_ inUse (subtract 1)) - return (resource, local) -#if __GLASGOW_HASKELL__ >= 700 -{-# INLINABLE takeResource #-} -#endif - --- | Similar to 'withResource', but only performs the action if a resource could --- be taken from the pool /without blocking/. Otherwise, 'tryWithResource' --- returns immediately with 'Nothing' (ie. the action function is /not/ called). --- Conversely, if a resource can be borrowed from the pool without blocking, the --- action is performed and it's result is returned, wrapped in a 'Just'. -tryWithResource :: forall m a b. -#if MIN_VERSION_monad_control(0,3,0) - (MonadBaseControl IO m) -#else - (MonadControlIO m) -#endif - => Pool a -> (a -> m b) -> m (Maybe b) -tryWithResource pool act = control $ \runInIO -> mask $ \restore -> do - res <- tryTakeResource pool - case res of - Just (resource, local) -> do - ret <- restore (runInIO (Just <$> act resource)) `onException` - destroyResource pool local resource - putResource local resource - return ret - Nothing -> restore . runInIO $ return (Nothing :: Maybe b) -#if __GLASGOW_HASKELL__ >= 700 -{-# INLINABLE tryWithResource #-} -#endif - --- | A non-blocking version of 'takeResource'. The 'tryTakeResource' function --- returns immediately, with 'Nothing' if the pool is exhausted, or @'Just' (a, --- 'LocalPool' a)@ if a resource could be borrowed from the pool successfully. -tryTakeResource :: Pool a -> IO (Maybe (a, LocalPool a)) -tryTakeResource pool@Pool{..} = do - local@LocalPool{..} <- getLocalPool pool - resource <- liftBase . join . atomically $ do - ents <- readTVar entries - case ents of - (Entry{..}:es) -> writeTVar entries es >> return (return . Just $ entry) - [] -> do - used <- readTVar inUse - if used == maxResources - then return (return Nothing) - else do - writeTVar inUse $! used + 1 - return $ Just <$> - create `onException` atomically (modifyTVar_ inUse (subtract 1)) - return $ (flip (,) local) <$> resource -#if __GLASGOW_HASKELL__ >= 700 -{-# INLINABLE tryTakeResource #-} -#endif - --- | Get a (Thread-)'LocalPool' --- --- Internal, just to not repeat code for 'takeResource' and 'tryTakeResource' -getLocalPool :: Pool a -> IO (LocalPool a) -getLocalPool Pool{..} = do - i <- liftBase $ ((`mod` numStripes) . hash) <$> myThreadId - return $ localPools V.! i -#if __GLASGOW_HASKELL__ >= 700 -{-# INLINABLE getLocalPool #-} -#endif - --- | Destroy a resource. Note that this will ignore any exceptions in the --- destroy function. -destroyResource :: Pool a -> LocalPool a -> a -> IO () -destroyResource Pool{..} LocalPool{..} resource = do - destroy resource `E.catch` \(_::SomeException) -> return () - atomically (modifyTVar_ inUse (subtract 1)) -#if __GLASGOW_HASKELL__ >= 700 -{-# INLINABLE destroyResource #-} -#endif - --- | Return a resource to the given 'LocalPool'. -putResource :: LocalPool a -> a -> IO () -putResource LocalPool{..} resource = do - now <- getCurrentTime - atomically $ modifyTVar_ entries (Entry resource now:) -#if __GLASGOW_HASKELL__ >= 700 -{-# INLINABLE putResource #-} -#endif - --- | Destroy all resources in all stripes in the pool. Note that this --- will ignore any exceptions in the destroy function. --- --- This function is useful when you detect that all resources in the --- pool are broken. For example after a database has been restarted --- all connections opened before the restart will be broken. In that --- case it's better to close those connections so that 'takeResource' --- won't take a broken connection from the pool but will open a new --- connection instead. --- --- Another use-case for this function is that when you know you are --- done with the pool you can destroy all idle resources immediately --- instead of waiting on the garbage collector to destroy them, thus --- freeing up those resources sooner. -destroyAllResources :: Pool a -> IO () -destroyAllResources Pool{..} = V.forM_ localPools $ purgeLocalPool destroy - -modifyTVar_ :: TVar a -> (a -> a) -> STM () -modifyTVar_ v f = readTVar v >>= \a -> writeTVar v $! f a - -modError :: String -> String -> a -modError func msg = - error $ "Data.Pool." ++ func ++ ": " ++ msg diff --git a/README.markdown b/README.markdown deleted file mode 100644 --- a/README.markdown +++ /dev/null @@ -1,28 +0,0 @@ -# Welcome to pool - -pool is a fast Haskell library for managing medium-lifetime pooled -resources, such as database connections. - -# Join in! - -We are happy to receive bug reports, fixes, documentation enhancements, -and other improvements. - -Please report bugs via the -[github issue tracker](http://github.com/bos/pool/issues). - -Master [git repository](http://github.com/bos/pool): - -* `git clone git://github.com/bos/pool.git` - -There's also a [Mercurial mirror](http://bitbucket.org/bos/pool): - -* `hg clone http://bitbucket.org/bos/pool` - -(You can create and contribute changes using either git or Mercurial.) - -Authors -------- - -This library is written and maintained by Bryan O'Sullivan, -. diff --git a/README.md b/README.md new file mode 100644 --- /dev/null +++ b/README.md @@ -0,0 +1,9 @@ +# resource-pool + +[![CI](https://github.com/scrive/pool/actions/workflows/haskell-ci.yml/badge.svg?branch=master)](https://github.com/scrive/pool/actions/workflows/haskell-ci.yml) +[![Hackage](https://img.shields.io/hackage/v/resource-pool.svg)](https://hackage.haskell.org/package/resource-pool) +[![Stackage LTS](https://www.stackage.org/package/resource-pool/badge/lts)](https://www.stackage.org/lts/package/resource-pool) +[![Stackage Nightly](https://www.stackage.org/package/resource-pool/badge/nightly)](https://www.stackage.org/nightly/package/resource-pool) + +A high-performance striped resource pooling implementation for Haskell based on +[QSem](https://hackage.haskell.org/package/base/docs/Control-Concurrent-QSem.html). diff --git a/Setup.lhs b/Setup.lhs deleted file mode 100644 --- a/Setup.lhs +++ /dev/null @@ -1,3 +0,0 @@ -#!/usr/bin/env runhaskell -> import Distribution.Simple -> main = defaultMain diff --git a/resource-pool.cabal b/resource-pool.cabal --- a/resource-pool.cabal +++ b/resource-pool.cabal @@ -1,55 +1,85 @@ +cabal-version: 3.0 +build-type: Simple name: resource-pool -version: 0.2.3.2 -synopsis: A high-performance striped resource pooling implementation -description: - A high-performance striped pooling abstraction for managing - flexibly-sized collections of resources such as database - connections. - -homepage: http://github.com/bos/pool -license: BSD3 +version: 0.5.0.1 +license: BSD-3-Clause license-file: LICENSE -author: Bryan O'Sullivan -maintainer: Bryan O'Sullivan , - Bas van Dijk -copyright: Copyright 2011 MailRank, Inc. category: Data, Database, Network -build-type: Simple -extra-source-files: - README.markdown +maintainer: andrzej@rybczak.net +author: Andrzej Rybczak, Bryan O'Sullivan -cabal-version: >=1.8 +synopsis: A high-performance striped resource pooling implementation -flag developer - description: operate in developer mode - default: False - manual: True +description: A high-performance striped pooling abstraction for managing + flexibly-sized collections of resources such as database + connections. +tested-with: GHC == { 8.10.7, 9.0.2, 9.2.8, 9.4.8, 9.6.7, 9.8.4, 9.10.3, 9.12.4, 9.14.1 } + +extra-doc-files: + CHANGELOG.md + README.md + +bug-reports: https://github.com/scrive/pool/issues +source-repository head + type: git + location: https://github.com/scrive/pool.git + library - exposed-modules: - Data.Pool + hs-source-dirs: src - build-depends: - base >= 4.4 && < 5, - hashable, - monad-control >= 0.2.0.1, - transformers, - transformers-base >= 0.4, - stm >= 2.3, - time, - vector >= 0.7 + exposed-modules: Data.Pool + Data.Pool.Internal + Data.Pool.Introspection - if flag(developer) - ghc-options: -Werror - ghc-prof-options: -auto-all - cpp-options: -DASSERTS -DDEBUG + build-depends: base >= 4.14 && < 5 + , hashable >= 1.1.0.0 + , primitive >= 0.7 + , stm + , text + , time - ghc-options: -Wall + ghc-options: -Wall + -Wcompat + -Wmissing-deriving-strategies + -Werror=prepositive-qualified-module -source-repository head - type: git - location: http://github.com/bos/pool + default-language: Haskell2010 -source-repository head - type: mercurial - location: http://bitbucket.org/bos/pool + default-extensions: DeriveGeneric + , DerivingStrategies + , ImportQualifiedPost + , LambdaCase + , RankNTypes + , ScopedTypeVariables + , TypeApplications + +test-suite test + type: exitcode-stdio-1.0 + hs-source-dirs: test + + main-is: Main.hs + + build-depends: base + , async + , resource-pool + , stm + , tasty + , tasty-hunit + , text + + ghc-options: -Wall + -Wcompat + -Wmissing-deriving-strategies + -Werror=prepositive-qualified-module + -threaded + -rtsopts + "-with-rtsopts=-N4" + + default-language: Haskell2010 + + default-extensions: DerivingStrategies + , ImportQualifiedPost + , LambdaCase + , ScopedTypeVariables + , TypeApplications diff --git a/src/Data/Pool.hs b/src/Data/Pool.hs new file mode 100644 --- /dev/null +++ b/src/Data/Pool.hs @@ -0,0 +1,142 @@ +-- | A high-performance pooling abstraction for managing flexibly-sized +-- collections of resources such as database connections. +module Data.Pool + ( -- * Pool + Pool + , LocalPool + , newPool + + -- ** Configuration + , PoolConfig + , defaultPoolConfig + , setNumStripes + , setPoolLabel + + -- * Resource management + , withResource + , takeResource + , tryWithResource + , tryTakeResource + , putResource + , destroyResource + , destroyAllResources + + -- * Compatibility with 0.2 + , createPool + ) where + +import Control.Concurrent.STM +import Control.Exception +import Control.Monad +import Data.Text qualified as T +import Data.Time (NominalDiffTime) + +import Data.Pool.Internal + +-- | Take a resource from the pool, perform an action with it and return it to +-- the pool afterwards. +-- +-- * If the pool has an idle resource available, it is used immediately. +-- +-- * Otherwise, if the maximum number of resources has not yet been reached, a +-- new resource is created and used. +-- +-- * If the maximum number of resources has been reached, this function blocks +-- until a resource becomes available. +-- +-- If the action throws an exception of any type, the resource is destroyed and +-- not returned to the pool. +-- +-- It probably goes without saying that you should never manually destroy a +-- pooled resource, as doing so will almost certainly cause a subsequent user +-- (who expects the resource to be valid) to throw an exception. +withResource :: Pool a -> (a -> IO r) -> IO r +withResource pool act = mask $ \unmask -> do + (res, localPool) <- takeResource pool + r <- unmask (act res) `onException` destroyResource pool localPool res + putResource localPool res + pure r + +-- | Take a resource from the pool, following the same results as +-- 'withResource'. +-- +-- /Note:/ this function returns both a resource and the 'LocalPool' it came +-- from so that it may either be destroyed (via 'destroyResource') or returned +-- to the pool (via 'putResource'). +takeResource :: Pool a -> IO (a, LocalPool a) +takeResource pool = mask_ $ do + lp <- getLocalPool (localPools pool) + join . atomically $ do + stripe <- readTVar (stripeVar lp) + if available stripe == 0 + then do + q <- newEmptyTMVar + writeTVar (stripeVar lp) $! stripe {queueR = Queue q (queueR stripe)} + pure + $ waitForResource (stripeVar lp) q >>= \case + Just a -> pure (a, lp) + Nothing -> do + a <- createResource (poolConfig pool) `onException` restoreSize (stripeVar lp) + pure (a, lp) + else takeAvailableResource pool lp stripe + +-- | A variant of 'withResource' that doesn't execute the action and returns +-- 'Nothing' instead of blocking if the local pool is exhausted. +tryWithResource :: Pool a -> (a -> IO r) -> IO (Maybe r) +tryWithResource pool act = mask $ \unmask -> + tryTakeResource pool >>= \case + Just (res, localPool) -> do + r <- unmask (act res) `onException` destroyResource pool localPool res + putResource localPool res + pure (Just r) + Nothing -> pure Nothing + +-- | A variant of 'takeResource' that returns 'Nothing' instead of blocking if +-- the local pool is exhausted. +tryTakeResource :: Pool a -> IO (Maybe (a, LocalPool a)) +tryTakeResource pool = mask_ $ do + lp <- getLocalPool (localPools pool) + join . atomically $ do + stripe <- readTVar (stripeVar lp) + if available stripe == 0 + then pure $ pure Nothing + else fmap Just <$> takeAvailableResource pool lp stripe + +{-# DEPRECATED createPool "Use newPool instead" #-} + +-- | Provided for compatibility with @resource-pool < 0.3@. +-- +-- Use 'newPool' instead. +createPool :: IO a -> (a -> IO ()) -> Int -> NominalDiffTime -> Int -> IO (Pool a) +createPool create free numStripes idleTime maxResources = + newPool + PoolConfig + { createResource = create + , freeResource = free + , poolCacheTTL = realToFrac idleTime + , poolMaxResources = numStripes * maxResources + , poolNumStripes = Just numStripes + , pcLabel = T.empty + } + +---------------------------------------- +-- Helpers + +takeAvailableResource + :: Pool a + -> LocalPool a + -> Stripe a + -> STM (IO (a, LocalPool a)) +takeAvailableResource pool lp stripe = case cache stripe of + [] -> do + writeTVar (stripeVar lp) $! stripe {available = available stripe - 1} + pure $ do + a <- createResource (poolConfig pool) `onException` restoreSize (stripeVar lp) + pure (a, lp) + Entry a _ : as -> do + writeTVar (stripeVar lp) + $! stripe + { available = available stripe - 1 + , cache = as + } + pure $ pure (a, lp) diff --git a/src/Data/Pool/Internal.hs b/src/Data/Pool/Internal.hs new file mode 100644 --- /dev/null +++ b/src/Data/Pool/Internal.hs @@ -0,0 +1,380 @@ +{-# OPTIONS_HADDOCK not-home #-} + +-- | Internal implementation details for "Data.Pool". +-- +-- This module is intended for internal use only, and may change without warning +-- in subsequent releases. +module Data.Pool.Internal where + +import Control.Concurrent +import Control.Concurrent.STM +import Control.Exception +import Control.Monad +import Data.Either +import Data.Hashable (hash) +import Data.IORef +import Data.List qualified as L +import Data.Primitive.SmallArray +import Data.Text qualified as T +import GHC.Clock (getMonotonicTime) +import GHC.Conc (labelThread, unsafeIOToSTM) + +-- | Striped resource pool based on "Control.Concurrent.QSem". +data Pool a = Pool + { poolConfig :: !(PoolConfig a) + , localPools :: !(SmallArray (LocalPool a)) + , reaperRef :: !(IORef ()) + } + +-- | A single, local pool. +data LocalPool a = LocalPool + { stripeId :: !Int + , stripeVar :: !(TVar (Stripe a)) + , cleanerRef :: !(IORef ()) + } + +-- | Stripe of a resource pool. If @available@ is 0, the list of threads waiting +-- for a resource (each with an associated 'TMVar') is @queue ++ reverse queueR@ +-- to ensure fairness. +data Stripe a = Stripe + { available :: !Int + , cache :: ![Entry a] + , queue :: !(Queue a) + , queueR :: !(Queue a) + } + +-- | An existing resource currently sitting in a pool. +data Entry a = Entry + { entry :: a + , lastUsed :: !Double + } + +-- | A queue of TMVarS corresponding to threads waiting for resources. +-- +-- Basically a monomorphic list to save two pointer indirections. +data Queue a = Queue !(TMVar (Maybe a)) (Queue a) | Empty + +-- | Configuration of a 'Pool'. +data PoolConfig a = PoolConfig + { createResource :: !(IO a) + , freeResource :: !(a -> IO ()) + , poolCacheTTL :: !Double + , poolMaxResources :: !Int + , poolNumStripes :: !(Maybe Int) + , pcLabel :: !T.Text + } + +-- | Create a 'PoolConfig' with optional parameters having default values. +-- +-- For setting optional parameters have a look at: +-- +-- - 'setNumStripes' +-- +-- @since 0.4.0.0 +defaultPoolConfig + :: IO a + -- ^ The action that creates a new resource. + -> (a -> IO ()) + -- ^ The action that destroys an existing resource. + -> Double + -- ^ The number of seconds for which an unused resource is kept around. The + -- smallest acceptable value is @0.5@. + -- + -- /Note:/ the elapsed time before destroying a resource may be a little + -- longer than requested, as the collector thread wakes at 1-second intervals. + -> Int + -- ^ The maximum number of resources to keep open __across all stripes__. The + -- smallest acceptable value is @1@ per stripe. + -- + -- /Note:/ if the number of stripes does not divide the number of resources, + -- some of the stripes will have 1 more resource available than the others. + -> PoolConfig a +defaultPoolConfig create free cacheTTL maxResources = + PoolConfig + { createResource = create + , freeResource = free + , poolCacheTTL = cacheTTL + , poolMaxResources = maxResources + , poolNumStripes = Just 1 + , pcLabel = T.empty + } + +-- | Set the number of stripes (sub-pools) in the pool. +-- +-- If not explicitly set, the default number of stripes is 1, which should be +-- good for typical use (when in doubt, profile your application first). +-- +-- If set to 'Nothing', the pool will create the number of stripes equal to the +-- number of capabilities. +-- +-- /Note:/ usage of multiple stripes reduces contention, but can also result in +-- suboptimal use of resources since stripes are separated from each other. +-- +-- @since 0.4.0.0 +setNumStripes :: Maybe Int -> PoolConfig a -> PoolConfig a +setNumStripes numStripes pc = pc {poolNumStripes = numStripes} + +-- | Assign a label to the pool. +-- +-- The label will appear in a label of the collector thread as well as +-- t'Data.Pool.Introspection.Resource'. +-- +-- @since 0.5.0.0 +setPoolLabel :: T.Text -> PoolConfig a -> PoolConfig a +setPoolLabel label pc = pc {pcLabel = label} + +-- | Create a new striped resource pool. +-- +-- /Note:/ although the runtime system will destroy all idle resources when the +-- pool is garbage collected, it's recommended to manually call +-- 'destroyAllResources' when you're done with the pool so that the resources +-- are freed up as soon as possible. +newPool :: PoolConfig a -> IO (Pool a) +newPool pc = do + when (poolCacheTTL pc < 0.5) $ do + error "poolCacheTTL must be at least 0.5" + when (poolMaxResources pc < 1) $ do + error "poolMaxResources must be at least 1" + numStripes <- maybe getNumCapabilities pure (poolNumStripes pc) + when (numStripes < 1) $ do + error "numStripes must be at least 1" + when (poolMaxResources pc < numStripes) $ do + error "poolMaxResources must not be smaller than numStripes" + let mkArray = fmap (smallArrayFromListN numStripes) + pools <- mkArray . forM (stripeResources numStripes) $ \(n, resources) -> do + ref <- newIORef () + stripe <- + newTVarIO + Stripe + { available = resources + , cache = [] + , queue = Empty + , queueR = Empty + } + -- When the local pool goes out of scope, free its resources. + void . mkWeakIORef ref $ cleanStripe (const True) (freeResource pc) stripe + pure + LocalPool + { stripeId = n + , stripeVar = stripe + , cleanerRef = ref + } + mask_ $ do + ref <- newIORef () + collectorA <- forkIOWithUnmask $ \unmask -> unmask $ do + tid <- myThreadId + labelThread tid $ "resource-pool: collector (" ++ T.unpack (pcLabel pc) ++ ")" + collector pools + void . mkWeakIORef ref $ do + -- When the pool goes out of scope, stop the collector. Resources existing + -- in stripes will be taken care by their cleaners. + killThread collectorA + pure + Pool + { poolConfig = pc + , localPools = pools + , reaperRef = ref + } + where + stripeResources :: Int -> [(Int, Int)] + stripeResources numStripes = + let (base, rest) = quotRem (poolMaxResources pc) numStripes + in zip [1 .. numStripes] $ addRest (replicate numStripes base) rest + where + addRest [] = error "unreachable" + addRest acc@(r : rs) = \case + 0 -> acc + rest -> r + 1 : addRest rs (rest - 1) + + -- Collect stale resources from the pool once per second. + collector pools = forever $ do + threadDelay 1000000 + now <- getMonotonicTime + let isStale e = now - lastUsed e > poolCacheTTL pc + mapM_ (cleanStripe isStale (freeResource pc) . stripeVar) pools + +-- | Destroy a resource. +-- +-- /Note:/ since version 0.5.0.0 exceptions thrown by the destroy function are +-- no longer ignored. +destroyResource :: Pool a -> LocalPool a -> a -> IO () +destroyResource pool lp a = mask_ $ do + atomically $ do + stripe <- readTVar (stripeVar lp) + newStripe <- signal stripe Nothing + writeTVar (stripeVar lp) $! newStripe + freeResource (poolConfig pool) a + +-- | Return a resource to the given 'LocalPool'. +putResource :: LocalPool a -> a -> IO () +putResource lp a = atomically $ do + stripe <- readTVar (stripeVar lp) + newStripe <- signal stripe (Just a) + writeTVar (stripeVar lp) $! newStripe + +-- | Destroy all resources in all stripes in the pool. +-- +-- Note that this will ignore any exceptions in the destroy function. +-- +-- This function is useful when you detect that all resources in the pool are +-- broken. For example after a database has been restarted all connections +-- opened before the restart will be broken. In that case it's better to close +-- those connections so that 'takeResource' won't take a broken connection from +-- the pool but will open a new connection instead. +-- +-- Another use-case for this function is that when you know you are done with +-- the pool you can destroy all idle resources immediately instead of waiting on +-- the garbage collector to destroy them, thus freeing up those resources +-- sooner. +destroyAllResources :: Pool a -> IO () +destroyAllResources pool = forM_ (localPools pool) $ \lp -> do + cleanStripe (const True) (freeResource (poolConfig pool)) (stripeVar lp) + +---------------------------------------- +-- Helpers + +-- | Get a local pool. +getLocalPool :: SmallArray (LocalPool a) -> IO (LocalPool a) +getLocalPool pools = do + sid <- + if stripes == 1 + then -- If there is just one stripe, there is no choice. + pure 0 + else do + capabilities <- getNumCapabilities + -- Selecting a stripe by a capability the current thread runs on gives + -- equal load distribution only if the number of stripes divides the + -- number of capabilities. Otherwise: + -- + -- - If the number of stripes is smaller than the number of + -- capabilities, load distribution across all stripes wouldn't be + -- equal (e.g. if there are 2 stripes and 3 capabilities, stripe 0 + -- would be used by capability 0 and 2, while stripe 1 would only be + -- used by capability 1, a 100% load difference). + -- + -- - If the number of stripes is larger than the number of capabilities, + -- stripes with an id larger than the highest capability would never + -- be selected. + -- + -- In such cases we select based on the id of a thread. + if capabilities `rem` stripes /= 0 + then hash <$> myThreadId + else fmap fst . threadCapability =<< myThreadId + -- 'mod' is used instead of 'rem' since the hash of a thread id might be + -- negative, which would result in an out-of-bounds array access. + pure $ pools `indexSmallArray` (sid `mod` stripes) + where + stripes = sizeofSmallArray pools + +-- | Wait for the resource to be put into a given 'TMVar'. +waitForResource :: TVar (Stripe a) -> TMVar (Maybe a) -> IO (Maybe a) +waitForResource mstripe q = atomically (takeTMVar q) `onException` cleanup + where + cleanup = atomically $ do + stripe <- readTVar mstripe + newStripe <- + tryTakeTMVar q >>= \case + Just ma -> do + -- Between entering the exception handler and taking ownership of + -- the stripe we got the resource we wanted. We don't need it + -- anymore though, so pass it to someone else. + signal stripe ma + Nothing -> do + -- If we're still waiting, fill up the TMVar with an undefined value + -- so that 'signal' can discard our TMVar from the queue. + putTMVar q $ error "unreachable" + pure stripe + writeTVar mstripe $! newStripe + +-- | If an exception is received while a resource is being created, restore the +-- original size of the stripe. +restoreSize :: TVar (Stripe a) -> IO () +restoreSize mstripe = atomically $ do + stripe <- readTVar mstripe + -- Signal needs to be called so that if there are threads waiting for a + -- resource, one of them wakes up and attempts the creation itself. + newStripe <- signal stripe Nothing + writeTVar mstripe $! newStripe + +-- | Free resource entries in the stripes that fulfil a given condition. +cleanStripe + :: (Entry a -> Bool) + -> (a -> IO ()) + -> TVar (Stripe a) + -> IO () +cleanStripe isStale free mstripe = mask_ $ do + -- Asynchronous exceptions need to be masked here to prevent leaking of + -- 'stale' resources before they're freed. + stale <- atomically $ do + stripe <- readTVar mstripe + let (stale, fresh) = L.partition isStale (cache stripe) + -- There's no need to update 'available' here because it only tracks + -- the number of resources taken from the pool. + writeTVar mstripe $! stripe {cache = fresh} + pure $ map entry stale + -- We need to ignore exceptions in the 'free' function, otherwise if an + -- exception is thrown half-way, we leak the rest of the resources. Also, + -- asynchronous exceptions need to be hard masked here we need to run 'free' + -- for all resources. + uninterruptibleMask $ \release -> do + rs <- forM stale $ try @SomeException . release . free + -- If any async exception arrived in between, propagate it. + rethrowFirstAsyncException $ lefts rs + where + rethrowFirstAsyncException = \case + [] -> pure () + e : es + | Just SomeAsyncException {} <- fromException e -> throwIO e + | otherwise -> rethrowFirstAsyncException es + +signal :: forall a. Stripe a -> Maybe a -> STM (Stripe a) +signal stripe ma = + if available stripe == 0 + then loop (queue stripe) (queueR stripe) + else do + newCache <- case ma of + Just a -> do + now <- unsafeIOToSTM getMonotonicTime + pure $ Entry a now : cache stripe + Nothing -> pure $ cache stripe + pure + stripe + { available = available stripe + 1 + , cache = newCache + } + where + loop :: Queue a -> Queue a -> STM (Stripe a) + loop Empty Empty = do + newCache <- case ma of + Just a -> do + now <- unsafeIOToSTM getMonotonicTime + pure [Entry a now] + Nothing -> pure [] + pure + Stripe + { available = 1 + , cache = newCache + , queue = Empty + , queueR = Empty + } + loop Empty qR = loop (reverseQueue qR) Empty + loop (Queue q qs) qR = + tryPutTMVar q ma >>= \case + -- This fails when 'waitForResource' went into the exception handler and + -- filled the TMVar (with an undefined value) itself. In such case we + -- simply ignore it. + False -> loop qs qR + True -> + pure + stripe + { available = 0 + , queue = qs + , queueR = qR + } + + reverseQueue :: Queue a -> Queue a + reverseQueue = go Empty + where + go acc = \case + Empty -> acc + Queue x xs -> go (Queue x acc) xs diff --git a/src/Data/Pool/Introspection.hs b/src/Data/Pool/Introspection.hs new file mode 100644 --- /dev/null +++ b/src/Data/Pool/Introspection.hs @@ -0,0 +1,172 @@ +-- | A variant of "Data.Pool" with introspection capabilities. +module Data.Pool.Introspection + ( -- * Pool + Pool + , LocalPool + , newPool + + -- ** Configuration + , PoolConfig + , defaultPoolConfig + , setNumStripes + , setPoolLabel + + -- * Resource management + , Resource (..) + , Acquisition (..) + , withResource + , takeResource + , tryWithResource + , tryTakeResource + , putResource + , destroyResource + , destroyAllResources + ) where + +import Control.Concurrent.STM +import Control.Exception +import Control.Monad +import Data.Text qualified as T +import GHC.Clock (getMonotonicTime) +import GHC.Generics (Generic) + +import Data.Pool.Internal + +-- | A resource taken from the pool along with additional information. +data Resource a = Resource + { resource :: a + , poolLabel :: !T.Text + , stripeNumber :: !Int + , availableResources :: !Int + , acquisition :: !Acquisition + , acquisitionTime :: !Double + , creationTime :: !(Maybe Double) + } + deriving stock (Eq, Generic, Show) + +-- | Describes how a resource was acquired from the pool. +data Acquisition + = -- | A resource was taken from the pool immediately. + Immediate + | -- | The thread had to wait until a resource was released. + Delayed + deriving stock (Eq, Generic, Show) + +-- | 'Data.Pool.withResource' with introspection capabilities. +withResource :: Pool a -> (Resource a -> IO r) -> IO r +withResource pool act = mask $ \unmask -> do + (res, localPool) <- takeResource pool + r <- unmask (act res) `onException` destroyResource pool localPool (resource res) + putResource localPool (resource res) + pure r + +-- | 'Data.Pool.takeResource' with introspection capabilities. +takeResource :: Pool a -> IO (Resource a, LocalPool a) +takeResource pool = mask_ $ do + t1 <- getMonotonicTime + lp <- getLocalPool (localPools pool) + join . atomically $ do + stripe <- readTVar (stripeVar lp) + if available stripe == 0 + then do + q <- newEmptyTMVar + writeTVar (stripeVar lp) $! stripe {queueR = Queue q (queueR stripe)} + pure + $ waitForResource (stripeVar lp) q >>= \case + Just a -> do + t2 <- getMonotonicTime + let res = + Resource + { resource = a + , poolLabel = pcLabel $ poolConfig pool + , stripeNumber = stripeId lp + , availableResources = 0 + , acquisition = Delayed + , acquisitionTime = t2 - t1 + , creationTime = Nothing + } + pure (res, lp) + Nothing -> do + t2 <- getMonotonicTime + a <- createResource (poolConfig pool) `onException` restoreSize (stripeVar lp) + t3 <- getMonotonicTime + let res = + Resource + { resource = a + , poolLabel = pcLabel $ poolConfig pool + , stripeNumber = stripeId lp + , availableResources = 0 + , acquisition = Delayed + , acquisitionTime = t2 - t1 + , creationTime = Just $! t3 - t2 + } + pure (res, lp) + else takeAvailableResource pool t1 lp stripe + +-- | A variant of 'withResource' that doesn't execute the action and returns +-- 'Nothing' instead of blocking if the local pool is exhausted. +tryWithResource :: Pool a -> (Resource a -> IO r) -> IO (Maybe r) +tryWithResource pool act = mask $ \unmask -> + tryTakeResource pool >>= \case + Just (res, localPool) -> do + r <- unmask (act res) `onException` destroyResource pool localPool (resource res) + putResource localPool (resource res) + pure (Just r) + Nothing -> pure Nothing + +-- | A variant of 'takeResource' that returns 'Nothing' instead of blocking if +-- the local pool is exhausted. +tryTakeResource :: Pool a -> IO (Maybe (Resource a, LocalPool a)) +tryTakeResource pool = mask_ $ do + t1 <- getMonotonicTime + lp <- getLocalPool (localPools pool) + join . atomically $ do + stripe <- readTVar (stripeVar lp) + if available stripe == 0 + then pure $ pure Nothing + else fmap Just <$> takeAvailableResource pool t1 lp stripe + +---------------------------------------- +-- Helpers + +takeAvailableResource + :: Pool a + -> Double + -> LocalPool a + -> Stripe a + -> STM (IO (Resource a, LocalPool a)) +takeAvailableResource pool t1 lp stripe = case cache stripe of + [] -> do + let newAvailable = available stripe - 1 + writeTVar (stripeVar lp) $! stripe {available = newAvailable} + pure $ do + t2 <- getMonotonicTime + a <- createResource (poolConfig pool) `onException` restoreSize (stripeVar lp) + t3 <- getMonotonicTime + let res = + Resource + { resource = a + , poolLabel = pcLabel $ poolConfig pool + , stripeNumber = stripeId lp + , availableResources = newAvailable + , acquisition = Immediate + , acquisitionTime = t2 - t1 + , creationTime = Just $! t3 - t2 + } + pure (res, lp) + Entry a _ : as -> do + let newAvailable = available stripe - 1 + writeTVar (stripeVar lp) $! stripe {available = newAvailable, cache = as} + pure $ do + t2 <- getMonotonicTime + let res = + Resource + { resource = a + , poolLabel = pcLabel $ poolConfig pool + , stripeNumber = stripeId lp + , availableResources = newAvailable + , acquisition = Immediate + , acquisitionTime = t2 - t1 + , creationTime = Nothing + } + pure (res, lp) diff --git a/test/Main.hs b/test/Main.hs new file mode 100644 --- /dev/null +++ b/test/Main.hs @@ -0,0 +1,320 @@ +module Main (main) where + +import Control.Concurrent +import Control.Concurrent.Async +import Control.Concurrent.STM +import Control.Exception +import Control.Monad +import Data.Foldable qualified as F +import Data.IORef +import Data.List qualified as L +import Data.Maybe +import Data.Text qualified as T +import System.Timeout (timeout) +import Test.Tasty hiding (withResource) +import Test.Tasty.HUnit + +import Data.Pool +import Data.Pool.Internal (LocalPool (..), Pool (..), Queue (..), Stripe (..)) +import Data.Pool.Introspection qualified as I + +main :: IO () +main = + defaultMain . localOption (mkTimeout 60000000) + $ testGroup + "resource-pool" + [ configValidationTests + , basicTests + , concurrencyTests + , introspectionTests + , stressTests + ] + +---------------------------------------- +-- Configuration validation + +configValidationTests :: TestTree +configValidationTests = + testGroup + "config validation" + [ testCase "rejects too small poolCacheTTL" $ do + expectError . newPool $ poolConfig_ 0.4 1 + , testCase "rejects non-positive poolMaxResources" $ do + expectError . newPool $ poolConfig_ 100 0 + , testCase "rejects non-positive number of stripes" $ do + expectError . newPool . setNumStripes (Just 0) $ poolConfig_ 100 1 + , testCase "rejects poolMaxResources smaller than the number of stripes" $ do + expectError . newPool . setNumStripes (Just 4) $ poolConfig_ 100 2 + ] + where + poolConfig_ = defaultPoolConfig (pure ()) (\_ -> pure ()) + + expectError :: IO a -> Assertion + expectError io = + try @ErrorCall (void io) >>= \case + Left _ -> pure () + Right _ -> assertFailure "expected newPool to error out" + +---------------------------------------- +-- Basic tests + +basicTests :: TestTree +basicTests = + testGroup + "basic" + [ testCase "an idle resource is reused" $ do + tp <- mkPool 5 + r1 <- withResource (testPool tp) pure + r2 <- withResource (testPool tp) pure + assertEqual "the same resource is taken" r1 r2 + readIORef (createdCount tp) >>= assertEqual "created resources" 1 + , testCase "concurrently taken resources are distinct" $ do + tp <- mkPool 5 + (r1, lp1) <- takeResource (testPool tp) + (r2, lp2) <- takeResource (testPool tp) + assertBool "resources are distinct" $ r1 /= r2 + putResource lp1 r1 + putResource lp2 r2 + , testCase "tryTakeResource returns Nothing iff the pool is exhausted" $ do + tp <- mkPool 1 + Just (r, lp) <- tryTakeResource (testPool tp) + mr <- tryTakeResource (testPool tp) + assertBool "Nothing when exhausted" $ isNothing mr + putResource lp r + mr2 <- tryTakeResource (testPool tp) + assertBool "Just when a resource is available" $ isJust mr2 + , testCase "tryWithResource returns Nothing iff the pool is exhausted" $ do + tp <- mkPool 1 + (r, lp) <- takeResource (testPool tp) + mr <- tryWithResource (testPool tp) pure + assertEqual "Nothing when exhausted" Nothing mr + putResource lp r + mr2 <- tryWithResource (testPool tp) pure + assertEqual "Just when a resource is available" (Just r) mr2 + , testCase "withResource destroys the resource on exception" $ do + tp <- mkPool 5 + r <- try @Boom $ withResource (testPool tp) $ \_ -> throwIO Boom :: IO () + assertEqual "the exception is propagated" (Left Boom) r + readIORef (freedCount tp) >>= assertEqual "freed resources" 1 + -- The pool is still usable and creates a fresh resource. + _ <- withResource (testPool tp) pure + readIORef (createdCount tp) >>= assertEqual "created resources" 2 + , testCase "destroyResource frees the resource and its slot" $ do + tp <- mkPool 1 + (r1, lp) <- takeResource (testPool tp) + destroyResource (testPool tp) lp r1 + readIORef (freedCount tp) >>= assertEqual "freed resources" 1 + r2 <- withResource (testPool tp) pure + assertBool "resource is fresh" $ r2 /= r1 + , testCase "destroyAllResources frees all idle resources" $ do + tp <- mkPool 5 + rs <- replicateM 3 $ takeResource (testPool tp) + forM_ rs $ \(r, lp) -> putResource lp r + destroyAllResources (testPool tp) + readIORef (freedCount tp) >>= assertEqual "freed resources" 3 + -- The pool is still usable and creates a fresh resource. + _ <- withResource (testPool tp) pure + readIORef (createdCount tp) >>= assertEqual "created resources" 4 + , testCase "resources are distributed evenly across stripes" $ do + tp <- mkPoolWith (setNumStripes $ Just 2) 5 + ss <- stripeStates (testPool tp) + assertEqual "available resources per stripe" [2, 3] + $ L.sort (map available ss) + , testCase "idle resources exceeding the TTL are collected" $ do + createdC <- newIORef (0 :: Int) + freedC <- newIORef (0 :: Int) + pool <- + newPool + $ defaultPoolConfig + (atomicModifyIORef' createdC $ \n -> (n + 1, n + 1)) + (\_ -> atomicModifyIORef' freedC $ \n -> (n + 1, ())) + 0.5 + 5 + _ <- withResource pool pure + -- The collector thread wakes up every second. + waitUntil "the resource is collected" $ (== 1) <$> readIORef freedC + readIORef createdC >>= assertEqual "created resources" 1 + ] + +---------------------------------------- +-- Concurrency tests + +concurrencyTests :: TestTree +concurrencyTests = + testGroup + "concurrency" + [ testCase "the number of created resources never exceeds the maximum" $ do + tp <- mkPool 3 + mapConcurrently_ + (\_ -> replicateM_ 10 . withResource (testPool tp) $ \_ -> threadDelay 1000) + [1 .. 20 :: Int] + created <- readIORef (createdCount tp) + assertBool ("created " ++ show created ++ " resources") $ created <= 3 + ss <- stripeStates (testPool tp) + assertEqual "all permits are available" 3 $ sum (map available ss) + , testCase "a blocked thread is woken up by putResource" $ do + tp <- mkPool 1 + (r, lp) <- takeResource (testPool tp) + done <- newEmptyMVar + _ <- forkIO $ withResource (testPool tp) pure >>= putMVar done + waitUntil "the thread is queued" + $ any ((> 0) . queueLength) <$> stripeStates (testPool tp) + putResource lp r + mr <- timeout 5000000 $ takeMVar done + assertEqual "the returned resource is received" (Just r) mr + , testCase "a blocked thread is woken up when resource creation fails" $ do + entered <- newEmptyMVar + gate <- newEmptyMVar + let create = do + putMVar entered () + takeMVar gate + throwIO Boom :: IO Int + pool <- newPool $ defaultPoolConfig create (\_ -> pure ()) 100 1 + t1 <- newEmptyMVar + _ <- forkIO $ try @Boom (withResource pool $ \_ -> pure ()) >>= putMVar t1 + takeMVar entered + t2 <- newEmptyMVar + _ <- forkIO $ try @Boom (withResource pool $ \_ -> pure ()) >>= putMVar t2 + waitUntil "the second thread is queued" + $ any ((> 0) . queueLength) <$> stripeStates pool + -- Fail creation in the first thread. The second one needs to be woken + -- up and attempt creation itself. + putMVar gate () + takeMVar t1 >>= assertEqual "the first thread failed" (Left Boom) + mr <- timeout 5000000 $ do + takeMVar entered + putMVar gate () + takeMVar t2 + assertEqual "the second thread attempted creation" (Just (Left Boom)) mr + ] + +---------------------------------------- +-- Introspection tests + +introspectionTests :: TestTree +introspectionTests = + testGroup + "introspection" + [ testCase "resource metadata is filled in correctly" $ do + pool <- + newPool . setPoolLabel (T.pack "label") + $ defaultPoolConfig (pure (0 :: Int)) (\_ -> pure ()) 100 1 + (res, lp) <- I.takeResource pool + assertEqual "poolLabel" (T.pack "label") (I.poolLabel res) + assertEqual "stripeNumber" 1 (I.stripeNumber res) + assertEqual "acquisition" I.Immediate (I.acquisition res) + assertBool "creationTime is set for a fresh resource" + $ isJust (I.creationTime res) + putResource lp $ I.resource res + (res2, lp2) <- I.takeResource pool + assertEqual "acquisition" I.Immediate (I.acquisition res2) + assertEqual "creationTime is not set for a cached resource" Nothing + $ I.creationTime res2 + putResource lp2 $ I.resource res2 + , testCase "acquisition of a blocked thread is Delayed" $ do + tp <- mkPool 1 + (res, lp) <- I.takeResource (testPool tp) + done <- newEmptyMVar + _ <- forkIO $ I.takeResource (testPool tp) >>= putMVar done + waitUntil "the thread is queued" + $ any ((> 0) . queueLength) <$> stripeStates (testPool tp) + putResource lp $ I.resource res + mr <- timeout 5000000 $ takeMVar done + case mr of + Nothing -> assertFailure "the blocked thread wasn't woken up" + Just (res2, lp2) -> do + assertEqual "acquisition" I.Delayed (I.acquisition res2) + putResource lp2 $ I.resource res2 + ] + +---------------------------------------- +-- Stress tests + +stressTests :: TestTree +stressTests = + testGroup + "stress" + [ testCase "pool invariants hold under load (1 stripe)" $ stressTest 1 + , testCase "pool invariants hold under load (4 stripes)" $ stressTest 4 + ] + where + stressTest numStripes = do + let maxResources = 8 + tp <- mkPoolWith (setNumStripes $ Just numStripes) maxResources + mapConcurrently_ + ( \i -> replicateM_ 50 $ do + r <- try @Boom . withResource (testPool tp) $ \_ -> do + threadDelay 100 + -- Some of the threads always fail, destroying the resource. + when (i `rem` 5 == 0) $ throwIO Boom + case r of + Left Boom -> when (i `rem` 5 /= 0) $ throwIO Boom + Right () -> pure () + ) + [1 .. 30 :: Int] + -- Once the pool is idle again, all permits are available, all live + -- resources sit in stripe caches and no thread is queued. + ss <- stripeStates (testPool tp) + assertEqual "all permits are available" maxResources + $ sum (map available ss) + created <- readIORef (createdCount tp) + freed <- readIORef (freedCount tp) + assertEqual "all live resources are cached" (created - freed) + $ sum (map (length . cache) ss) + assertEqual "no thread is queued" 0 $ sum (map queueLength ss) + +---------------------------------------- +-- Helpers + +data Boom = Boom + deriving stock (Eq, Show) + +instance Exception Boom + +data TestPool = TestPool + { testPool :: Pool Int + , createdCount :: IORef Int + , freedCount :: IORef Int + } + +mkPool :: Int -> IO TestPool +mkPool = mkPoolWith id + +mkPoolWith :: (PoolConfig Int -> PoolConfig Int) -> Int -> IO TestPool +mkPoolWith adjust maxResources = do + createdC <- newIORef 0 + freedC <- newIORef 0 + pool <- + newPool . adjust + $ defaultPoolConfig + (atomicModifyIORef' createdC $ \n -> (n + 1, n + 1)) + (\_ -> atomicModifyIORef' freedC $ \n -> (n + 1, ())) + 100 + maxResources + pure + TestPool + { testPool = pool + , createdCount = createdC + , freedCount = freedC + } + +stripeStates :: Pool a -> IO [Stripe a] +stripeStates pool = mapM (readTVarIO . stripeVar) . F.toList $ localPools pool + +queueLength :: Stripe a -> Int +queueLength stripe = go (queue stripe) + go (queueR stripe) + where + go = \case + Empty -> 0 + Queue _ q -> 1 + go q + +-- | Wait (up to 10 seconds) until a condition is met. +waitUntil :: String -> IO Bool -> Assertion +waitUntil label cond = go (100 :: Int) + where + go n = do + ok <- cond + unless ok + $ if n == 0 + then assertFailure $ "timed out waiting until " ++ label + else threadDelay 100000 >> go (n - 1)