locked-poll is a package to enable simple concurrent polling with a locking scheme.
The library is quite small, needing
There are lots of tests in the test-suite to ensure that it behaves itself with polls.
There is only one function :
makeLockingFunction :: forall k lockableState . (Key k,Show lockableState) => Int64 -> -- timeout (KeyFcn lockableState k) -> -- extract a key IO ((lockableState -> IO ()) -> -- function to run against state lockableState -> -- incoming state IO ())
This function is used to generate a function which has an embedded action that is dependent on some given state. The idea is to generate that locking function at the top level and then pass it to whatever needs incremental access to a resource.
It uses an IORef under the hood to store what states are currently in use.
Use the timeout function to say when to release the lock.
No cleanup is performed by the lockingFunction, so wrap your things in finally or bracket as needed.
-- | 'Key' Constraint for locking down a traverse or fold type Key k = (Ord k,Eq k,Show k) -- |Extract a key from a given state type KeyFcn st k = Key k => st -> k
KeyFcn tells the lockingFunction how to extract the LockingKey.
Uniqueness is not necessary but if you do not have it, only one of a given group of like Keyed objects will be allowed to run at a time.
How to run tests
cabal configure --enable-tests && cabal build && cabal test
The tests are quite slow (4 or 5 min) because they are trying to test long poll concurrency
Right now you have to hand delete the resulting output.
TODO: Write contribution instructions here