Control.Monad.Log

This module provides a mtl style MonadLog class and a concrete monad transformer LogT.

If you are an application author, you can use LogT transformer, a specialized reader monad to inject Logger.

If you are a library author, you should:

• make your monad stack an instance of MonadLog, usually you can do this by embedding a Logger into your monad's reader part.
• provide a default formatter, and API to run with customized formatter.

parametrized Logger type

newtype Level

a newtype wrapper arounded Int for GHC unpacking, with following TextShow instance:

showb (Level 0) = "DEBUG"
showb (Level 1) = "INFO"
showb (Level 2) = "WARNING"
showb (Level 3) = "ERROR"
showb (Level 4) = "CRITICAL"
showb (Level x) = "OTHER:" <> showb x

Constructors

Level Int

Instances

Bounded Level

Methods

minBound :: Level

maxBound :: Level

Eq Level

Methods

(==) :: Level -> Level -> Bool

(/=) :: Level -> Level -> Bool

Ord Level

Methods

compare :: Level -> Level -> Ordering

(<) :: Level -> Level -> Bool

(<=) :: Level -> Level -> Bool

(>) :: Level -> Level -> Bool

(>=) :: Level -> Level -> Bool

max :: Level -> Level -> Level

min :: Level -> Level -> Level

Read Level

Methods

readsPrec :: Int -> ReadS Level

readList :: ReadS [Level]

readPrec :: ReadPrec Level

readListPrec :: ReadPrec [Level]

Show Level

Methods

showsPrec :: Int -> Level -> ShowS

show :: Level -> String

showList :: [Level] -> ShowS

TextShow Level

Methods

showbPrec :: Int -> Level -> Builder

showb :: Level -> Builder

showbList :: [Level] -> Builder

showtPrec :: Int -> Level -> Text

showt :: Level -> Text

showtList :: [Level] -> Text

showtlPrec :: Int -> Level -> Text

showtl :: Level -> Text

showtlList :: [Level] -> Text

levelDebug :: Level

Alias for Level 0

levelInfo :: Level

Alias for Level 1

levelWarning :: Level

Alias for Level 2

levelError :: Level

Alias for Level 3

levelCritical :: Level

Alias for Level 4

data Logger env

A logger type parametrized by an extra environment type.

Constructors

Logger

Fields

• filterLevel :: !Level

  filter level, equal or above it will be logged.

• environment :: env

  parametrized logging environment.

• formatter :: Level -> FormattedTime -> env -> Text -> LogStr

  formatter function.

• timeCache :: IO FormattedTime

  a time cache to avoid cost of frequently formatting time.

• logger :: LogStr -> IO ()

  a FastLogger log function.

• cleanUp :: IO ()

  clean up action(flushing/closing file...).

envLens :: Functor f => (env -> f env) -> Logger env -> f (Logger env)

Lens for environment.

makeLogger

Arguments

:: MonadIO m

=> (Level -> FormattedTime -> env -> Text -> LogStr)

formatter function

-> TimeFormat

check System.Log.FastLogger.Date

-> LogType

-> Level

filter level

-> env

init environment

-> m (Logger env)

make a Logger based on FastLogger.

makeDefaultLogger :: (MonadIO m, TextShow env) => TimeFormat -> LogType -> Level -> env -> m (Logger env)

make a Logger with defaultFormatter.

makeDefaultJSONLogger :: (MonadIO m, ToJSON env) => TimeFormat -> LogType -> Level -> env -> m (Logger env)

make a Logger with defaultJSONFormatter.

defaultFormatter :: TextShow env => Level -> FormattedTime -> env -> Text -> LogStr

a default formatter with following format:

[LEVEL] [TIME] [ENV] LOG MESSAGE\n

defaultJSONFormatter :: ToJSON env => Level -> FormattedTime -> env -> Text -> LogStr

a default JSON formatter with following format:

{"level": LEVEL, "time": TIME, "env": ENV, "msg": "LOG MESSAGE" }\n

MonadLog class

class MonadIO m => MonadLog env m | m -> env where

This is the main class for using logging function in this package.

provide an instance for MonadLog to log within your monad stack.

Minimal complete definition

askLogger, localLogger

Methods

askLogger :: m (Logger env)

localLogger :: (Logger env -> Logger env) -> m a -> m a

Instances

MonadLog env m => MonadLog env (MaybeT m)

Methods

askLogger :: MaybeT m (Logger env)

localLogger :: (Logger env -> Logger env) -> MaybeT m a -> MaybeT m a

MonadLog env m => MonadLog env (ListT m)

Methods

askLogger :: ListT m (Logger env)

localLogger :: (Logger env -> Logger env) -> ListT m a -> ListT m a

MonadIO m => MonadLog env (LogT env m)

Methods

askLogger :: LogT env m (Logger env)

localLogger :: (Logger env -> Logger env) -> LogT env m a -> LogT env m a

(Monoid w, MonadLog env m) => MonadLog env (WriterT w m)

Methods

askLogger :: WriterT w m (Logger env)

localLogger :: (Logger env -> Logger env) -> WriterT w m a -> WriterT w m a

(Monoid w, MonadLog env m) => MonadLog env (WriterT w m)

Methods

askLogger :: WriterT w m (Logger env)

localLogger :: (Logger env -> Logger env) -> WriterT w m a -> WriterT w m a

MonadLog env m => MonadLog env (StateT s m)

Methods

askLogger :: StateT s m (Logger env)

localLogger :: (Logger env -> Logger env) -> StateT s m a -> StateT s m a

MonadLog env m => MonadLog env (StateT s m)

Methods

askLogger :: StateT s m (Logger env)

localLogger :: (Logger env -> Logger env) -> StateT s m a -> StateT s m a

MonadLog env m => MonadLog env (IdentityT * m)

Methods

askLogger :: IdentityT * m (Logger env)

localLogger :: (Logger env -> Logger env) -> IdentityT * m a -> IdentityT * m a

MonadLog env m => MonadLog env (ExceptT e m)

Methods

askLogger :: ExceptT e m (Logger env)

localLogger :: (Logger env -> Logger env) -> ExceptT e m a -> ExceptT e m a

MonadLog env m => MonadLog env (ReaderT * r m)

Methods

askLogger :: ReaderT * r m (Logger env)

localLogger :: (Logger env -> Logger env) -> ReaderT * r m a -> ReaderT * r m a

MonadLog env m => MonadLog env (ContT * r m)

Methods

askLogger :: ContT * r m (Logger env)

localLogger :: (Logger env -> Logger env) -> ContT * r m a -> ContT * r m a

(MonadLog env m, Monoid w) => MonadLog env (RWST r w s m)

Methods

askLogger :: RWST r w s m (Logger env)

localLogger :: (Logger env -> Logger env) -> RWST r w s m a -> RWST r w s m a

(MonadLog env m, Monoid w) => MonadLog env (RWST r w s m)

Methods

askLogger :: RWST r w s m (Logger env)

localLogger :: (Logger env -> Logger env) -> RWST r w s m a -> RWST r w s m a

withFilterLevel :: MonadLog env m => Level -> m a -> m a

run MonadLog within a new FilterLevel.

withEnv :: MonadLog env m => env -> m a -> m a

run MonadLog within a new environment.

localEnv :: MonadLog env m => (env -> env) -> m a -> m a

run MonadLog within a modified environment.

LogT, a concrete monad transformaer

newtype LogT env m a

A simple MonadLog instance.

a special reader monad which embed a Logger.

Constructors

LogT

Fields

• runLogT :: Logger env -> m a

Instances

MonadIO m => MonadLog env (LogT env m)

Methods

askLogger :: LogT env m (Logger env)

localLogger :: (Logger env -> Logger env) -> LogT env m a -> LogT env m a

MonadTrans (LogT env)

Methods

lift :: Monad m => m a -> LogT env m a

Monad m => Monad (LogT env m)

Methods

(>>=) :: LogT env m a -> (a -> LogT env m b) -> LogT env m b

(>>) :: LogT env m a -> LogT env m b -> LogT env m b

return :: a -> LogT env m a

fail :: String -> LogT env m a

Monad m => Functor (LogT env m)

Methods

fmap :: (a -> b) -> LogT env m a -> LogT env m b

(<$) :: a -> LogT env m b -> LogT env m a

MonadFix m => MonadFix (LogT r m)

Methods

mfix :: (a -> LogT r m a) -> LogT r m a

MonadFail m => MonadFail (LogT env m)

Methods

fail :: String -> LogT env m a

Monad m => Applicative (LogT env m)

Methods

pure :: a -> LogT env m a

(<*>) :: LogT env m (a -> b) -> LogT env m a -> LogT env m b

(*>) :: LogT env m a -> LogT env m b -> LogT env m b

(<*) :: LogT env m a -> LogT env m b -> LogT env m a

MonadIO m => MonadIO (LogT env m)

Methods

liftIO :: IO a -> LogT env m a

runLogTSafe :: (MonadIO m, MonadMask m) => Logger env -> LogT env m a -> m a

safely run LogT inside MonadMask. Logs are guaranteed to be flushed on exceptions.

runLogTSafeBase :: (MonadBaseControl IO m, MonadIO m) => Logger env -> LogT env m a -> m a

safely run LogT inside 'MonadBaseControl IO m'. Logs are guaranteed to be flushed on exceptions.

runLogT' :: MonadIO m => Logger env -> LogT env m a -> m a

runLogT' = flip runLogT, run LogT without clean up. usually used inside different threads so that an exception won't clean up Logger.

logging functions

debug :: MonadLog env m => Text -> m ()

info :: MonadLog env m => Text -> m ()

warning :: MonadLog env m => Text -> m ()

error :: MonadLog env m => Text -> m ()

critical :: MonadLog env m => Text -> m ()

debug' :: MonadLog env m => env -> Text -> m ()

info' :: MonadLog env m => env -> Text -> m ()

warning' :: MonadLog env m => env -> Text -> m ()

error' :: MonadLog env m => env -> Text -> m ()

critical' :: MonadLog env m => env -> Text -> m ()

re-export from text-show and fast-logger

data LogStr :: *

Log message builder. Use (<>) to append two LogStr in O(1).

Instances

IsString LogStr

Methods

fromString :: String -> LogStr

Semigroup LogStr

Methods

(<>) :: LogStr -> LogStr -> LogStr

sconcat :: NonEmpty LogStr -> LogStr

stimes :: Integral b => b -> LogStr -> LogStr

Monoid LogStr

Methods

mempty :: LogStr

mappend :: LogStr -> LogStr -> LogStr

mconcat :: [LogStr] -> LogStr

ToLogStr LogStr

Methods

toLogStr :: LogStr -> LogStr

toLogStr :: ToLogStr msg => msg -> LogStr

data LogType :: *

Logger Type.

Constructors

LogNone

No logging.

LogStdout BufSize

Logging to stdout. BufSize is a buffer size

LogStderr BufSize

Logging to stdout. BufSize is a buffer size for each capability.

LogFileNoRotate FilePath BufSize

Logging to a file. BufSize is a buffer size for each capability.

LogFile FileLogSpec BufSize

Logging to a file. BufSize is a buffer size for each capability. File rotation is done on-demand.

LogCallback (LogStr -> IO ()) (IO ())

Logging with a log and flush action. run flush after log each message.

data FileLogSpec :: *

The spec for logging files

Constructors

FileLogSpec

Fields

• log_file :: FilePath
• log_file_size :: Integer

  Max log file size (in bytes) before requiring rotation.

• log_backup_number :: Int

  Max number of rotated log files to keep around before overwriting the oldest one.

type TimeFormat = ByteString

type FormattedTime = ByteString

Type aliaes for date format and formatted date.

simpleTimeFormat :: TimeFormat

A simple time cache using format "%d%b%Y:%T %z"

simpleTimeFormat' :: TimeFormat

A simple time cache using format "%d-%b-%Y %T"