Safe Haskell	Safe-Inferred
Language	GHC2021

Hydra.Persistence

Description

Handles to save/load files across the hydra-node. We use a simple JSON encoding and two modes of operation to store things: Full and Incremental.

Synopsis

data PersistenceException
- = PersistenceException String
- | IncorrectAccessException String
data Persistence a m = Persistence {
- save :: ToJSON a => a -> m ()
- load :: FromJSON a => m (Maybe a)
}
createPersistence :: (MonadIO m, MonadThrow m) => FilePath -> m (Persistence a m)
data PersistenceIncremental a m = PersistenceIncremental {
- append :: ToJSON a => a -> m ()
- source :: FromJSON a => ConduitT () a (ResourceT m) ()
}
loadAll :: (FromJSON a, MonadUnliftIO m) => PersistenceIncremental a m -> m [a]
createPersistenceIncremental :: forall a m. (MonadUnliftIO m, MonadThrow m, FromJSON a) => FilePath -> m (PersistenceIncremental a m)

Documentation

Constructors

PersistenceException String
IncorrectAccessException String

Instances details

Exception PersistenceException Source #
Instance details Defined in Hydra.Persistence Methods toException :: PersistenceException -> SomeException Source # fromException :: SomeException -> Maybe PersistenceException Source # displayException :: PersistenceException -> String Source #
Show PersistenceException Source #
Instance details Defined in Hydra.Persistence Methods showsPrec :: Int -> PersistenceException -> ShowS Source # show :: PersistenceException -> String Source # showList :: [PersistenceException] -> ShowS Source #
Eq PersistenceException Source #
Instance details Defined in Hydra.Persistence Methods (==) :: PersistenceException -> PersistenceException -> Bool Source # (/=) :: PersistenceException -> PersistenceException -> Bool Source #

Handle to save and load files to/from disk using JSON encoding.

Constructors

Persistence
Fields save :: ToJSON a => a -> m () load :: FromJSON a => m (Maybe a)

Initialize persistence handle for given type a at given file path.

Handle to save incrementally and load files to/from disk using JSON encoding.

Constructors

PersistenceIncremental
Fields append :: ToJSON a => a -> m () source :: FromJSON a => ConduitT () a (ResourceT m) () Stream all elements from the file.

loadAll :: (FromJSON a, MonadUnliftIO m) => PersistenceIncremental a m -> m [a] Source #

Load all elements from persistence into a list. XXX: Deprecate this to avoid large memory usage.

createPersistenceIncremental :: forall a m. (MonadUnliftIO m, MonadThrow m, FromJSON a) => FilePath -> m (PersistenceIncremental a m) Source #

Initialize persistence handle for given type a at given file path.

This instance of PersistenceIncremental is "thread-safe" in the sense that it prevents loading from a different thread once one starts $sel:append:PersistenceIncrementaling through the handle. If another thread attempts to $sel:source:PersistenceIncremental (or loadAll) after this point, an IncorrectAccessException will be raised.