Copyright	(c) Seller Labs, 2016
License	Apache 2.0
Maintainer	[email protected]
Stability	experimental
Portability	POSIX
Safe Haskell	None
Language	Haskell2010

Control.Monad.Logger.Prefix

Contents

LogPrefixT

Description

This module exports the LogPrefixT monad transfomer. This transformer adds a given prefix to a MonadLogger context, allowing you to make your logs a bit more greppable without including much boilerplate. The prefixes can be nested easily.

The function prefixLogs is the most convenient way to use the library. All you have to do is use the function to add the prefix, and it Just Works. Here's an example:

someLoggingFunction :: MonadLogger m => m ()
someLoggingFunction = do
    $(logDebug) "No prefix here"
    "foo" `prefixLogs` do
        $(logDebug) "There's a [foo] there!
        "bar" `prefixLogs` do
            $(logDebug) "Now there's a [foo] *and* a [bar]"

Synopsis

LogPrefixT

data LogPrefixT m a Source #

LogPrefixT is a monad transformer that prepends a bit of text to each logging action in the current MonadLogger context. The internals are currently implemented as a wrapper around ReaderT Text.

Instances

MonadTrans LogPrefixT Source #
Methods lift :: Monad m => m a -> LogPrefixT m a #
MonadBaseControl b m => MonadBaseControl b (LogPrefixT m) Source #
Associated Types type StM (LogPrefixT m :: * -> ) a :: # Methods liftBaseWith :: (RunInBase (LogPrefixT m) b -> b a) -> LogPrefixT m a # restoreM :: StM (LogPrefixT m) a -> LogPrefixT m a #
MonadBase b m => MonadBase b (LogPrefixT m) Source #
Methods liftBase :: b α -> LogPrefixT m α #
MonadReader r m => MonadReader r (LogPrefixT m) Source #
Methods ask :: LogPrefixT m r # local :: (r -> r) -> LogPrefixT m a -> LogPrefixT m a # reader :: (r -> a) -> LogPrefixT m a #
MonadState s m => MonadState s (LogPrefixT m) Source #
Methods get :: LogPrefixT m s # put :: s -> LogPrefixT m () # state :: (s -> (a, s)) -> LogPrefixT m a #
MonadWriter w m => MonadWriter w (LogPrefixT m) Source #
Methods writer :: (a, w) -> LogPrefixT m a # tell :: w -> LogPrefixT m () # listen :: LogPrefixT m a -> LogPrefixT m (a, w) # pass :: LogPrefixT m (a, w -> w) -> LogPrefixT m a #
Monad m => Monad (LogPrefixT m) Source #
Methods (>>=) :: LogPrefixT m a -> (a -> LogPrefixT m b) -> LogPrefixT m b # (>>) :: LogPrefixT m a -> LogPrefixT m b -> LogPrefixT m b # return :: a -> LogPrefixT m a # fail :: String -> LogPrefixT m a #
Functor m => Functor (LogPrefixT m) Source #
Methods fmap :: (a -> b) -> LogPrefixT m a -> LogPrefixT m b # (<$) :: a -> LogPrefixT m b -> LogPrefixT m a #
Applicative m => Applicative (LogPrefixT m) Source #
Methods pure :: a -> LogPrefixT m a # (<>) :: LogPrefixT m (a -> b) -> LogPrefixT m a -> LogPrefixT m b # (>) :: LogPrefixT m a -> LogPrefixT m b -> LogPrefixT m b # (<*) :: LogPrefixT m a -> LogPrefixT m b -> LogPrefixT m a #
MonadIO m => MonadIO (LogPrefixT m) Source #
Methods liftIO :: IO a -> LogPrefixT m a #
MonadThrow m => MonadThrow (LogPrefixT m) Source #
Methods throwM :: Exception e => e -> LogPrefixT m a #
MonadCatch m => MonadCatch (LogPrefixT m) Source #
Methods catch :: Exception e => LogPrefixT m a -> (e -> LogPrefixT m a) -> LogPrefixT m a #
MonadMask m => MonadMask (LogPrefixT m) Source #
Methods mask :: ((forall a. LogPrefixT m a -> LogPrefixT m a) -> LogPrefixT m b) -> LogPrefixT m b # uninterruptibleMask :: ((forall a. LogPrefixT m a -> LogPrefixT m a) -> LogPrefixT m b) -> LogPrefixT m b #
MonadLogger m => MonadLogger (LogPrefixT m) Source #
Methods monadLoggerLog :: ToLogStr msg => Loc -> LogSource -> LogLevel -> msg -> LogPrefixT m () #
MonadResource m => MonadResource (LogPrefixT m) Source #
Methods liftResourceT :: ResourceT IO a -> LogPrefixT m a #
type StM (LogPrefixT m) a Source #
type StM (LogPrefixT m) a = StM m a

prefixLogs :: Text -> LogPrefixT m a -> m a infixr 5 Source #

This function runs the underlying MonadLogger instance with a prefix using the LogPrefixT transformer.

>>> :set -XOverloadedStrings
>>> let l = logDebugN "bar"
>>> runStdoutLoggingT (prefixLogs "foo" (logDebugN "bar\n"))
[Debug] [foo] bar
...