Safe Haskell	None
Language	Haskell2010

Data.Pool.Introspection

Contents

Pool
Resource management

Description

A variant of Data.Pool with introspection capabilities.

Synopsis

data PoolConfig a = PoolConfig {
- createResource :: !( IO a)
- freeResource :: !(a -> IO ())
- poolCacheTTL :: ! Double
- poolMaxResources :: ! Int
}
data Pool a
data LocalPool a
newPool :: PoolConfig a -> IO ( Pool a)
data Resource a = Resource {
- resource :: a
- stripeNumber :: ! Int
- availableResources :: ! Int
- acquisition :: ! Acquisition
- acquisitionTime :: ! Double
- creationTime :: !( Maybe Double )
}
data Acquisition
- = Immediate
- | Delayed
withResource :: Pool a -> ( Resource a -> IO r) -> IO r
takeResource :: Pool a -> IO ( Resource a, LocalPool a)
tryWithResource :: Pool a -> ( Resource a -> IO r) -> IO ( Maybe r)
tryTakeResource :: Pool a -> IO ( Maybe ( Resource a, LocalPool a))
putResource :: LocalPool a -> a -> IO ()
destroyResource :: Pool a -> LocalPool a -> a -> IO ()
destroyAllResources :: Pool a -> IO ()

Pool

data PoolConfig a Source #

Configuration of a Pool .

Constructors

PoolConfig

Fields

createResource :: !( IO a)

The action that creates a new resource.
freeResource :: !(a -> IO ())

The action that destroys an existing resource.
poolCacheTTL :: ! Double

The amount 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.
poolMaxResources :: ! Int

The maximum number of resources to keep open across all stripes. The smallest acceptable value is 1 .

Note: for each stripe the number of resources is divided by the number of capabilities and rounded up. Therefore the pool might end up creating up to N - 1 resources more in total than specified, where N is the number of capabilities.

data Pool a Source #

Striped resource pool based on Control.Concurrent.QSem .

The number of stripes is arranged to be equal to the number of capabilities so that they never compete over access to the same stripe. This results in a very good performance in a multi-threaded environment.

data LocalPool a Source #

A single, capability-local pool.

newPool :: PoolConfig a -> IO ( Pool a) Source #

Create a new striped resource pool.

The number of stripes is equal to the number of capabilities.

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.

Resource management

data Resource a Source #

A resource taken from the pool along with additional information.

Constructors

Resource
Fields resource :: a stripeNumber :: ! Int availableResources :: ! Int acquisition :: ! Acquisition acquisitionTime :: ! Double creationTime :: !( Maybe Double )

Instances

Instances details

Eq a => Eq ( Resource a) Source #
Instance details Defined in Data.Pool.Introspection Methods (==) :: Resource a -> Resource a -> Bool Source # (/=) :: Resource a -> Resource a -> Bool Source #
Show a => Show ( Resource a) Source #
Instance details Defined in Data.Pool.Introspection Methods showsPrec :: Int -> Resource a -> ShowS Source # show :: Resource a -> String Source # showList :: [ Resource a] -> ShowS Source #
Generic ( Resource a) Source #
Instance details Defined in Data.Pool.Introspection Associated Types type Rep ( Resource a) :: Type -> Type Source # Methods from :: Resource a -> Rep ( Resource a) x Source # to :: Rep ( Resource a) x -> Resource a Source #
type Rep ( Resource a) Source #
Instance details Defined in Data.Pool.Introspection type Rep ( Resource a) = D1 (' MetaData "Resource" "Data.Pool.Introspection" "resource-pool-0.3.1.0-AIkcTXD3R8wB6h2lmUl9hw" ' False ) ( C1 (' MetaCons "Resource" ' PrefixI ' True ) (( S1 (' MetaSel (' Just "resource") ' NoSourceUnpackedness ' NoSourceStrictness ' DecidedLazy ) ( Rec0 a) :: ( S1 (' MetaSel (' Just "stripeNumber") ' NoSourceUnpackedness ' SourceStrict ' DecidedStrict ) ( Rec0 Int ) :: S1 (' MetaSel (' Just "availableResources") ' NoSourceUnpackedness ' SourceStrict ' DecidedStrict ) ( Rec0 Int ))) :: ( S1 (' MetaSel (' Just "acquisition") ' NoSourceUnpackedness ' SourceStrict ' DecidedStrict ) ( Rec0 Acquisition ) :: ( S1 (' MetaSel (' Just "acquisitionTime") ' NoSourceUnpackedness ' SourceStrict ' DecidedStrict ) ( Rec0 Double ) :*: S1 (' MetaSel (' Just "creationTime") ' NoSourceUnpackedness ' SourceStrict ' DecidedStrict ) ( Rec0 ( Maybe Double ))))))

data Acquisition Source #

Describes how a resource was acquired from the pool.

Constructors

Immediate	A resource was taken from the pool immediately.
Delayed	The thread had to wait until a resource was released.

Instances

Instances details

Eq Acquisition Source #
Instance details Defined in Data.Pool.Introspection Methods (==) :: Acquisition -> Acquisition -> Bool Source # (/=) :: Acquisition -> Acquisition -> Bool Source #
Show Acquisition Source #
Instance details Defined in Data.Pool.Introspection Methods showsPrec :: Int -> Acquisition -> ShowS Source # show :: Acquisition -> String Source # showList :: [ Acquisition ] -> ShowS Source #
Generic Acquisition Source #
Instance details Defined in Data.Pool.Introspection Associated Types type Rep Acquisition :: Type -> Type Source # Methods from :: Acquisition -> Rep Acquisition x Source # to :: Rep Acquisition x -> Acquisition Source #
type Rep Acquisition Source #
Instance details Defined in Data.Pool.Introspection type Rep Acquisition = D1 (' MetaData "Acquisition" "Data.Pool.Introspection" "resource-pool-0.3.1.0-AIkcTXD3R8wB6h2lmUl9hw" ' False ) ( C1 (' MetaCons "Immediate" ' PrefixI ' False ) ( U1 :: Type -> Type ) :+: C1 (' MetaCons "Delayed" ' PrefixI ' False ) ( U1 :: Type -> Type ))

withResource :: Pool a -> ( Resource a -> IO r) -> IO r Source #

withResource with introspection capabilities.

takeResource :: Pool a -> IO ( Resource a, LocalPool a) Source #

takeResource with introspection capabilities.

tryWithResource :: Pool a -> ( Resource a -> IO r) -> IO ( Maybe r) Source #

A variant of withResource that doesn't execute the action and returns Nothing instead of blocking if the capability-local pool is exhausted.

tryTakeResource :: Pool a -> IO ( Maybe ( Resource a, LocalPool a)) Source #

A variant of takeResource that returns Nothing instead of blocking if the capability-local pool is exhausted.

putResource :: LocalPool a -> a -> IO () Source #

Return a resource to the given LocalPool .

destroyResource :: Pool a -> LocalPool a -> a -> IO () Source #

Destroy a resource.

Note that this will ignore any exceptions in the destroy function.

destroyAllResources :: Pool a -> IO () Source #

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.