Safe Haskell	None
Language	Haskell2010

Moto.Registry

Contents

Command-line support
Registry
State
Errors

Description

This module exports tools for implementing a registry that moto can use in order to keep track of the migrations that have been run so far.

It's unlikely that you'll need to concern yourself with this module as an end user of moto.

Please import as:

import qualified Moto.Registry as Moto

Synopsis

data RegistryConf where
- RegistryConf :: forall r. {..} -> RegistryConf
data Registry = Registry {
- registry_state :: Df1 -> IO State
- registry_prepare :: Df1 -> MigId -> Direction -> IO (Either Err_Prepare Log)
- registry_abort :: Df1 -> MigId -> Direction -> IO (Either Err_Abort Log)
- registry_commit :: Df1 -> MigId -> Direction -> IO (Either Err_Commit Log)
}
newAppendOnlyRegistry :: State -> (Log -> IO ()) -> IO Registry
data State
emptyState :: State
updateState :: State -> Log -> Either Err_UpdateState State
data Log
- = Log_Prepare UTCTime MigId Direction
- | Log_Commit UTCTime
- | Log_Abort UTCTime
data Err_Tainted = Err_Tainted
data Err_Prepare
data Err_Abort
- = Err_Abort_Clean
- | Err_Abort_Dirty MigId Direction
data Err_Commit
- = Err_Commit_Clean
- | Err_Commit_Dirty MigId Direction
data Err_UpdateState

Command-line support

data RegistryConf where #

Constructors

RegistryConf
Fields :: { registryConf_help :: String , registryConf_parse :: String -> Either String r , registryConf_with :: forall a. r -> (Registry -> IO a) -> IO a } -> RegistryConf

Registry

data Registry #

Constructors

Registry
Fields registry_state :: Df1 -> IO State registry_prepare :: Df1 -> MigId -> Direction -> IO (Either Err_Prepare Log) registry_abort :: Df1 -> MigId -> Direction -> IO (Either Err_Abort Log) registry_commit :: Df1 -> MigId -> Direction -> IO (Either Err_Commit Log)

newAppendOnlyRegistry Source #

Arguments

:: State

Initial registry state obtained by reading Logs from the backing append-only storage and running updateState on them.

-> (Log -> IO ())

How to store a newly generated Log in the backing append-only storage.

If this function throws an exception, then the execption will propagated as usual, but also, this registry will be marked as tained and each subsequent operation on it will throw Err_Tainted.

-> IO Registry

Create a Registry backed by an append-only Log storage.

This registry maintains its internal State in memory as long as it is possible to successfuly store all the changes in the underlying append-only storage. If at some point this fails unrecoverably, then Err_Tainted will be thrown by the functions acting on this Registry.

It's important to acquire some kind of exclusive lock on the underlying storage, so that other applications can't poke it while our Registry is running.

State

data State #

Instances

Eq State
Instance details Defined in Moto.Internal Methods (==) :: State -> State -> Bool # (/=) :: State -> State -> Bool #
Show State
Instance details Defined in Moto.Internal Methods showsPrec :: Int -> State -> ShowS # show :: State -> String # showList :: [State] -> ShowS #

emptyState :: State #

updateState :: State -> Log -> Either Err_UpdateState State #

data Log #

Constructors

Log_Prepare UTCTime MigId Direction
Log_Commit UTCTime
Log_Abort UTCTime

Instances

Eq Log
Instance details Defined in Moto.Internal Methods (==) :: Log -> Log -> Bool # (/=) :: Log -> Log -> Bool #
Read Log
Instance details Defined in Moto.Internal Methods readsPrec :: Int -> ReadS Log # readList :: ReadS [Log] # readPrec :: ReadPrec Log # readListPrec :: ReadPrec [Log] #
Show Log
Instance details Defined in Moto.Internal Methods showsPrec :: Int -> Log -> ShowS # show :: Log -> String # showList :: [Log] -> ShowS #

Errors

data Err_Tainted Source #

The Registry is tainted, meaning our last attempt to interact with the registry's backing storage failed. We can't be certain about the current state of the Registry.

Constructors

Err_Tainted

Instances

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

data Err_Prepare #

Constructors

Err_Prepare_Duplicate MigId
Err_Prepare_NotFound MigId
Err_Prepare_Dirty MigId Direction

Instances

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

data Err_Abort #

Constructors

Err_Abort_Clean
Err_Abort_Dirty MigId Direction

Instances

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

data Err_Commit #

Constructors

Err_Commit_Clean
Err_Commit_Dirty MigId Direction

Instances

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

data Err_UpdateState #

Constructors

Err_UpdateState_Duplicate MigId
Err_UpdateState_NotFound MigId
Err_UpdateState_Clean
Err_UpdateState_Dirty

Instances

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