Safe Haskell	None
Language	Haskell2010

Control.Monad.Log

Contents

parametrized Logger type
MonadLog class
LogT, a concrete monad transformaer
logging functions
re-export from text-show and fast-logger

Description

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.

Synopsis

parametrized `Logger` type

newtype Level Source

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 Source
Eq Level Source
Ord Level Source
Read Level Source
Show Level Source
TextShow Level Source

levelDebug :: Level Source

Alias for Level 0

levelInfo :: Level Source

Alias for Level 1

levelWarning :: Level Source

Alias for Level 2

levelError :: Level Source

Alias for Level 3

levelCritical :: Level Source

Alias for Level 4

data Logger env Source

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) Source

Lens for environment.

makeLogger Source

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) Source

make a Logger with defaultFormatter.

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

make a Logger with defaultJSONFormatter.

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

a default formatter with following format:

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

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

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 Source

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

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

Methods

askLogger :: m (Logger env) Source

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

Instances

MonadLog env m => MonadLog env (MaybeT m) Source
MonadLog env m => MonadLog env (ListT m) Source
MonadLog env m => MonadLog env (IdentityT m) Source
MonadIO m => MonadLog env (LogT env m) Source
(Monoid w, MonadLog env m) => MonadLog env (WriterT w m) Source
(Monoid w, MonadLog env m) => MonadLog env (WriterT w m) Source
MonadLog env m => MonadLog env (StateT s m) Source
MonadLog env m => MonadLog env (StateT s m) Source
MonadLog env m => MonadLog env (ReaderT r m) Source
MonadLog env m => MonadLog env (ExceptT e m) Source
MonadLog env m => MonadLog env (ContT r m) Source
(MonadLog env m, Monoid w) => MonadLog env (RWST r w s m) Source
(MonadLog env m, Monoid w) => MonadLog env (RWST r w s m) Source

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

run MonadLog within a new FilterLevel.

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

run MonadLog within a new environment.

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

run MonadLog within a modified environment.

LogT, a concrete monad transformaer

newtype LogT env m a Source

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) Source
MonadTrans (LogT env) Source
Monad m => Monad (LogT env m) Source
Monad m => Functor (LogT env m) Source
MonadFix m => MonadFix (LogT r m) Source
Monad m => Applicative (LogT env m) Source
MonadIO m => MonadIO (LogT env m) Source

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

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 Source

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 Source

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 () Source

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

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

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

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

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

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

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

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

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

re-export from text-show and fast-logger

data LogStr :: *

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

Instances

IsString LogStr
Monoid LogStr
ToLogStr 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.