Control.Eff.Log.Writer

The LogWriter type encapsulates an effectful function to write LogMessages.

Used in conjunction with the SupportsLogger class, it can be used to write messages from within an effectful computation.

LogWriter Definition

newtype LogWriter writerM

A function that takes a log message and returns an effect that logs the message.

Constructors

MkLogWriter

Fields

• runLogWriter :: LogMessage -> writerM ()

Instances

Applicative w => Default (LogWriter w)

Defined in Control.Eff.Log.Writer

Methods

def :: LogWriter w

Handle (LogWriterReader h) e a (LogWriter h -> k)

Defined in Control.Eff.Log.Handler

Methods

handle :: (Eff e a -> LogWriter h -> k) -> Arrs e v a -> LogWriterReader h v -> LogWriter h -> k

handle_relay :: (e ~ (LogWriterReader h ': r'), Relay (LogWriter h -> k) r') => (a -> LogWriter h -> k) -> (Eff e a -> LogWriter h -> k) -> Eff e a -> LogWriter h -> k

respond_relay :: (a -> LogWriter h -> k) -> (Eff e a -> LogWriter h -> k) -> Eff e a -> LogWriter h -> k

class SupportsLogger h e where

This class describes how to lift the log writer action into some monad.

The second parameter is almost always Eff x so usually the method of this class lifts the log writer action into an effect monad.

Methods

liftLogWriter :: LogWriter h -> LogMessage -> Eff e ()

Instances

Lifted IO e => SupportsLogger IO e

Defined in Control.Eff.Log.Writer

Methods

liftLogWriter :: LogWriter IO -> LogMessage -> Eff e ()

Member CapturedLogsWriter e => SupportsLogger CaptureLogs e

A LogWriter monad for pure logging.

The SupportsLogger instance for this type assumes a Writer effect.

Defined in Control.Eff.Log.Writer

Methods

liftLogWriter :: LogWriter CaptureLogs -> LogMessage -> Eff e ()

SupportsLogger PureLogWriter e

A LogWriter monad for Trace based pure logging.

Defined in Control.Eff.Log.Writer

Methods

liftLogWriter :: LogWriter PureLogWriter -> LogMessage -> Eff e ()

LogWriter Zoo

Pure Writer

noOpLogWriter :: Applicative m => LogWriter m

This LogWriter will discard all messages.

NOTE: This is just an alias for def

debugTraceLogWriter :: Monad h => LogWriter h

A LogWriter that applies renderLogMessage to the log message and then traces it using traceM. This LogWriter work with any base monad.

newtype PureLogWriter a

A base monad for all side effect free LogWriter.

This is only required e.g. when logs are only either discarded or traced. See debugTraceLogWriter or noOpLogWriter.

This is just a wrapper around Identity and serves as a type that has a special SupportsLogger instance.

Constructors

MkPureLogWriter

Fields

• runPureLogWriter :: Identity a

Instances

Monad PureLogWriter

Defined in Control.Eff.Log.Writer

Methods

(>>=) :: PureLogWriter a -> (a -> PureLogWriter b) -> PureLogWriter b

(>>) :: PureLogWriter a -> PureLogWriter b -> PureLogWriter b

return :: a -> PureLogWriter a

fail :: String -> PureLogWriter a

Functor PureLogWriter

Defined in Control.Eff.Log.Writer

Methods

fmap :: (a -> b) -> PureLogWriter a -> PureLogWriter b

(<$) :: a -> PureLogWriter b -> PureLogWriter a

Applicative PureLogWriter

Defined in Control.Eff.Log.Writer

Methods

pure :: a -> PureLogWriter a

(<*>) :: PureLogWriter (a -> b) -> PureLogWriter a -> PureLogWriter b

liftA2 :: (a -> b -> c) -> PureLogWriter a -> PureLogWriter b -> PureLogWriter c

(*>) :: PureLogWriter a -> PureLogWriter b -> PureLogWriter b

(<*) :: PureLogWriter a -> PureLogWriter b -> PureLogWriter a

SupportsLogger PureLogWriter e

A LogWriter monad for Trace based pure logging.

Defined in Control.Eff.Log.Writer

Methods

liftLogWriter :: LogWriter PureLogWriter -> LogMessage -> Eff e ()

listLogWriter :: LogWriter CaptureLogs

A LogWriter monad that provides pure logging by capturing via the Writer effect.

newtype CaptureLogs a

A LogWriter monad that provides pure logging by capturing via the Writer effect.

Constructors

MkCaptureLogs

Fields

• unCaptureLogs :: Eff '[CapturedLogsWriter] a

Instances

Monad CaptureLogs

Defined in Control.Eff.Log.Writer

Methods

(>>=) :: CaptureLogs a -> (a -> CaptureLogs b) -> CaptureLogs b

(>>) :: CaptureLogs a -> CaptureLogs b -> CaptureLogs b

return :: a -> CaptureLogs a

fail :: String -> CaptureLogs a

Functor CaptureLogs

Defined in Control.Eff.Log.Writer

Methods

fmap :: (a -> b) -> CaptureLogs a -> CaptureLogs b

(<$) :: a -> CaptureLogs b -> CaptureLogs a

Applicative CaptureLogs

Defined in Control.Eff.Log.Writer

Methods

pure :: a -> CaptureLogs a

(<*>) :: CaptureLogs (a -> b) -> CaptureLogs a -> CaptureLogs b

liftA2 :: (a -> b -> c) -> CaptureLogs a -> CaptureLogs b -> CaptureLogs c

(*>) :: CaptureLogs a -> CaptureLogs b -> CaptureLogs b

(<*) :: CaptureLogs a -> CaptureLogs b -> CaptureLogs a

Member CapturedLogsWriter e => SupportsLogger CaptureLogs e

A LogWriter monad for pure logging.

The SupportsLogger instance for this type assumes a Writer effect.

Defined in Control.Eff.Log.Writer

Methods

liftLogWriter :: LogWriter CaptureLogs -> LogMessage -> Eff e ()

type CapturedLogsWriter = Writer LogMessage

Alias for the Writer that contains the captured LogMessages from CaptureLogs.

runCapturedLogsWriter :: Eff (CapturedLogsWriter ': e) a -> Eff e (a, [LogMessage])

Run a Writer for LogMessages.

Such a Writer is needed for CaptureLogs

IO Based LogWriter

consoleLogWriter :: LogWriter IO

Write LogMessages to standard output, formatted with printLogMessage.

ioHandleLogWriter :: HasCallStack => Handle -> LogWriter IO

A LogWriter that uses an IO action to write the message.

General Combinator

filteringLogWriter :: Monad e => LogPredicate -> LogWriter e -> LogWriter e

A LogWriter that applies a predicate to the LogMessage and delegates to to the given writer of the predicate is satisfied.

mappingLogWriter :: (LogMessage -> LogMessage) -> LogWriter e -> LogWriter e

A LogWriter that applies a function to the LogMessage and delegates the result to to the given writer.

mappingLogWriterM :: Monad e => (LogMessage -> e LogMessage) -> LogWriter e -> LogWriter e

Like mappingLogWriter allow the function that changes the LogMessage to have effects.

IO Based Combinator

ioLogWriter :: HasCallStack => (LogMessage -> IO ()) -> LogWriter IO

A LogWriter that uses an IO action to write the message.

Example use cases for this function are the consoleLogWriter and the ioHandleLogWriter.

defaultIoLogWriter :: String -> Facility -> LogWriter IO -> LogWriter IO

Decorate an IO based LogWriter to set important fields in log messages.

ALl log messages are censored to include basic log message information:

• The messages will carry the given application name in the lmAppName field.
• The lmTimestamp field contains the UTC time of the log event
• The lmThreadId field contains the thread-Id
• The lmHostname field contains the FQDN of the current host
• The lmFacility field contains the given Facility

It installs the given LogWriter, wrapped using mappingLogWriterM.