System.Logger.Logger

This module provides a logger that implements the logger interface that is defined in System.Logger.Types.

All the code of this module is in System.Logger.Logger.Internal.

The definitions in System.Logger.Types are re-exported by this module.

Re-Export Logger Interface

module System.Logger.Types

Logger

data Logger a

Instances

Generic (Logger a)

LoggerCtx (Logger a) a

Typeable (* -> *) Logger

type Rep (Logger a)

withLogger :: (MonadIO μ, MonadBaseControl IO μ) => LoggerConfig -> LoggerBackend a -> (Logger a -> μ α) -> μ α

Provide a computation with a Logger.

Here is an example how this can be used to run a computation with a MonadLog constraint:

withConsoleLogger
    ∷ (MonadIO m, MonadBaseControl IO m)
    ⇒ LogLevel
    → LoggerT T.Text m α
    → m α
withConsoleLogger level inner = do
   withHandleBackend (config ^. logConfigBackend) $ \backend →
       withLogger (config ^. logConfigLogger) backend $ runLoggerT inner
 where
   config = defaultLogConfig
       & logConfigLogger ∘ loggerConfigThreshold .~ level

For detailed information about how backends are executed refer to the documentation of createLogger.

withLogger_

Arguments

:: (MonadIO μ, MonadBaseControl IO μ)

=> (Text -> IO ())

alternate sink for logging exceptions in the logger itself.

-> LoggerConfig

-> LoggerBackend a

-> (Logger a -> μ α)

-> μ α

A version of withLogger that takes as an extra argument a function for logging errors in the logging system.

@since 0.2

withLogFunction :: (Show a, Typeable a, NFData a, MonadIO μ, MonadBaseControl IO μ) => LoggerConfig -> LoggerBackend a -> (LogFunctionIO a -> μ α) -> μ α

For simple cases, when the logger threshold and the logger scope is constant this function can be used to directly initialize a log function.

withLogFunction_

Arguments

:: (Show a, Typeable a, NFData a, MonadIO μ, MonadBaseControl IO μ)

=> (Text -> IO ())

alternate sink for logging exceptions in the logger itself.

-> LoggerConfig

-> LoggerBackend a

-> (LogFunctionIO a -> μ α)

-> μ α

For simple cases, when the logger threshold and the logger scope is constant this function can be used to directly initialize a log function.

@since 0.2

LoggerT Monad Transformer

type LoggerT a = LoggerCtxT (Logger a)

runLoggerT :: LoggerT a m α -> Logger a -> m α

runLogT :: (MonadBaseControl IO m, MonadIO m) => LoggerConfig -> LoggerBackend msg -> LoggerT msg m α -> m α

Convenience function that unwraps a MonadLog computation over a newly created Logger

Configuration Types

Logger Configuration

data LoggerConfig

Logger Configuration

Constructors

LoggerConfig

Fields

_loggerConfigQueueSize :: !Natural

_loggerConfigThreshold :: !LogLevel

initial log threshold, can be changed later on

_loggerConfigScope :: !LogScope

initial stack of log labels, can be extended later on

_loggerConfigPolicy :: !LogPolicy

how to deal with a congested logging pipeline

_loggerConfigExceptionLimit :: !(Maybe Natural)

number of consecutive backend exception that can occur before the logger raises an BackendTooManyExceptions exception. If this is Nothing the logger will discard all exceptions. For instance a value of 1 means that an exception is raised when the second exception occurs. A value of 0 means that an exception is raised for each exception.

@since 0.2

_loggerConfigExceptionWait :: !(Maybe Natural)

number of microseconds to wait after an exception from the backend. If this is Nothing the logger won't wait at all after an exception.

@since 0.2

_loggerConfigExitTimeout :: !(Maybe Natural)

timeout in microseconds for the logger to flush the queue and deliver all remaining log messages on termination. If this is Nothing termination of the logger blogs until all mesages are delivered.

@since 0.2

Instances

Eq LoggerConfig

Ord LoggerConfig

Read LoggerConfig

Show LoggerConfig

Generic LoggerConfig

ToJSON LoggerConfig

NFData LoggerConfig

Typeable * LoggerConfig

FromJSON (LoggerConfig -> LoggerConfig)

type Rep LoggerConfig

loggerConfigQueueSize :: Lens' LoggerConfig Natural

loggerConfigThreshold :: Lens' LoggerConfig LogLevel

loggerConfigScope :: Lens' LoggerConfig LogScope

loggerConfigPolicy :: Lens' LoggerConfig LogPolicy

loggerConfigExceptionLimit :: Lens' LoggerConfig (Maybe Natural)

loggerConfigExceptionWait :: Lens' LoggerConfig (Maybe Natural)

loggerConfigExitTimeout :: Lens' LoggerConfig (Maybe Natural)

defaultLoggerConfig :: LoggerConfig

Default Logger configuration

The exception limit for backend exceptions is 10 and the wait time between exceptions is 1000. This means that in case of a defunctioned backend the logger will exist by throwing an exception after at least one second. When the logger is terminated it is granted 1 second to flush the queue and deliver all remaining log messages.

validateLoggerConfig :: ConfigValidation LoggerConfig λ

pLoggerConfig :: MParser LoggerConfig

pLoggerConfig_

Arguments

:: Text

prefix for this and all subordinate command line options.

-> MParser LoggerConfig

A version of pLoggerConfig that takes a prefix for the command line option.

@since 0.2