Name: persistent-map
Synopsis: A thread-safe interface for finite map types with optional persistency support.
Description:
/Changes in 0.2.*:/
.
* Improved error handling. Backend lookup-exceptions are now rethrown in the
AdvSTM monad.
.
/Changes in 0.1.*:/
.
* Added the binary serialization backend.
.
This library provides a thread-safe (STM) frontend for finite map types together with a
backend interface for persistent storage. The /TMap/ data type
is thread-safe, since all access functions run inside an STM monad . Any type
instantiating 'Data.Edison.Assoc.FiniteMapX'
(see EdisonAPI) can be used as a map type.
.
When a TMap is modified within an STM transaction, a corresponding
backend IO-request is added using the onCommit hook (cf. stm-io-hooks
package). To ensure consistency,
the (Adv)STM monad runs these requests iff the transaction commits.
Additional backends (e.g. HDBC) can be added by instantiating the class
'Backend'.
.
/Example:/
.
Thread 1:
.
> atomically $ do
> isMemb <- member 1 tmap
> when (not isMemb) $
> insert 1 "john doe" tmap
.
Thread 2:
.
> atomically $ do
> v <- lookup 1 tmap
> -- ... do something with 'v'
> adjust (\_ -> "jd") 1 tmap
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The function 'member' will first check whether the key value '1' is in the map;
if not, it sends a lookup-request to the persistent backend
and then retries the transaction. Note that \"sending a lookup-request\"
essentially means adding a call to the corresponding IO-function of the backend
to the list of retry-IO actions. (This is done using the 'retryWith'
IO hook of the stm-io-package.)
.
If the value does not yet exist, function 'insert' adds the key-value mapping to the
TMap and sends an insert-request to the backend using the
'onCommit' hook of the stm-io-package. Note that 'onCommit' guarantees that
the backend IO action is only executed iff the transaction commits. Any
changes that were made to the TMap are invisible to other threads until
the onCommit actions are run. Therefore, the threads will always observe a
consistent state.
.
The module 'Data.TStorage' provides a high level interface to TMap inspired
by the TCache package ((C) Alberto Gomez Corona). It
can store any type that has a key (i.e. is an instance of type class 'HasKey').
See file Sample.hs for an example on how to use it.
.
/Warning:/ This package is very experimental and the interface will
probably change.
Author: Peter Robinson 2009
Maintainer: Peter Robinson <thaldyron@gmail.com>
License: LGPL
License-file: LICENSE
Version: 0.2.2
Category: Middleware, Concurrency
Stability: experimental
Homepage: http://darcs.monoid.at/persistent-map
build-type: Simple
cabal-version: >= 1.2.3
library
ghc-options: -Wall -fno-ignore-asserts -fno-warn-missing-fields -fwarn-incomplete-patterns
exposed-modules: Data.TMap
Data.TStorage
Data.TMap.Backend
Data.TMap.Backend.Binary
Data.TMap.Backend.NoBackend
Data.TMap.Backend.StdoutBackend
Data.CacheStructure
Data.CacheStructure.LRU
other-modules: Sample
Data.TMap.Exception
build-depends: base >= 4 && < 5,
EdisonAPI >= 1.2.1 && < 1.3,
LRU >= 0.1.1 && < 0.2,
EdisonCore >= 1.2.1.3 && < 1.3,
stm-io-hooks >= 0.3.0 && < 0.4,
-- HDBC >= 2.0 && < 2.1,
mtl >= 1.1.0.2 && < 1.2,
binary >= 0.5 && < 0.6,
filepath >= 1.1 && < 1.2,
directory >= 1.0.0.3 && < 1.1
extensions: MultiParamTypeClasses,
RankNTypes,
FunctionalDependencies,
FlexibleContexts,
FlexibleInstances,
UndecidableInstances,
DeriveDataTypeable,
ScopedTypeVariables