System.Wlog.IOLogger

Haskell Logging Framework, Primary Interface

Written by John Goerzen, [e-mail]

This module is a modification of System.Log.Logger of hslogger library. Unless proper description is written here, please use the original documentation available on hackage/hslogger.

Basic Types

data Logger

Instances

Generic Logger

Defined in System.Wlog.IOLogger

Associated Types

type Rep Logger :: Type -> Type

Methods

from :: Logger -> Rep Logger x

to :: Rep Logger x -> Logger

type Rep Logger

Defined in System.Wlog.IOLogger

type Rep Logger

Re-Exported from System.Wlog

data Severity

Severity is level of log message importance. It uniquely determines which messages to print.

Constructors

Debug

Debug messages

Info

Information

Notice

Important (more than average) information

Warning

General warnings

Error

General errors/severe errors

Instances

Bounded Severity

Defined in System.Wlog.Severity

Methods

minBound :: Severity

maxBound :: Severity

Enum Severity

Defined in System.Wlog.Severity

Methods

succ :: Severity -> Severity

pred :: Severity -> Severity

toEnum :: Int -> Severity

fromEnum :: Severity -> Int

enumFrom :: Severity -> [Severity]

enumFromThen :: Severity -> Severity -> [Severity]

enumFromTo :: Severity -> Severity -> [Severity]

enumFromThenTo :: Severity -> Severity -> Severity -> [Severity]

Eq Severity

Defined in System.Wlog.Severity

Methods

(==) :: Severity -> Severity -> Bool

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

Ord Severity

Defined in System.Wlog.Severity

Methods

compare :: Severity -> Severity -> Ordering

(<) :: Severity -> Severity -> Bool

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

(>) :: Severity -> Severity -> Bool

(>=) :: Severity -> Severity -> Bool

max :: Severity -> Severity -> Severity

min :: Severity -> Severity -> Severity

Read Severity

Defined in System.Wlog.Severity

Methods

readsPrec :: Int -> ReadS Severity

readList :: ReadS [Severity]

readPrec :: ReadPrec Severity

readListPrec :: ReadPrec [Severity]

Show Severity

Defined in System.Wlog.Severity

Methods

showsPrec :: Int -> Severity -> ShowS

show :: Severity -> String

showList :: [Severity] -> ShowS

Generic Severity

Defined in System.Wlog.Severity

Associated Types

type Rep Severity :: Type -> Type

Methods

from :: Severity -> Rep Severity x

to :: Rep Severity x -> Severity

ToJSON Severity

Defined in System.Wlog.Severity

Methods

toJSON :: Severity -> Value

toEncoding :: Severity -> Encoding

toJSONList :: [Severity] -> Value

toEncodingList :: [Severity] -> Encoding

FromJSON Severity

Defined in System.Wlog.Severity

Methods

parseJSON :: Value -> Parser Severity

parseJSONList :: Value -> Parser [Severity]

type Rep Severity

Defined in System.Wlog.Severity

type Rep Severity = D1 (MetaData "Severity" "System.Wlog.Severity" "log-warper-1.9.0-BcP8iiwzwkw7f22YOoi1Hd" False) ((C1 (MetaCons "Debug" PrefixI False) (U1 :: Type -> Type) :+: C1 (MetaCons "Info" PrefixI False) (U1 :: Type -> Type)) :+: (C1 (MetaCons "Notice" PrefixI False) (U1 :: Type -> Type) :+: (C1 (MetaCons "Warning" PrefixI False) (U1 :: Type -> Type) :+: C1 (MetaCons "Error" PrefixI False) (U1 :: Type -> Type))))

Logging Messages

Basic

logM

Arguments

:: MonadIO m

=> LoggerName

Name of the logger to use

-> Severity

Severity of this message

-> Text

The log text itself

-> m ()

Log a message using the given logger at a given priority.

logMCond :: MonadIO m => LoggerName -> Severity -> Text -> (LogHandlerTag -> Bool) -> m ()

Utility Functions

removeAllHandlers :: MonadIO m => m ()

Allow graceful shutdown. Release all opened fileshandlersetc.

Logger Manipulation

Finding ∨ Creating Loggers

getLogger :: MonadIO m => LoggerName -> m Logger

Returns the logger for the given name. If no logger with that name exists, creates new loggers and any necessary parent loggers, with no connected handlers.

getRootLogger :: MonadIO m => m Logger

Returns the root logger.

rootLoggerName :: LoggerName

The name of the root logger, which is always defined and present on the system.

Modifying Loggers

addHandler :: LogHandler a => a -> Logger -> Logger

Add handler to Logger. Returns a new Logger.

removeHandler :: Logger -> Logger

Remove a handler from the Logger. Handlers are removed in the reverse order they were added, so the following property holds for any LogHandler h:

removeHandler . addHandler h = id

If no handlers are associated with the Logger, it is returned unchanged.

The root logger's default handler that writes every message to stderr can be removed by using this function before any handlers have been added to the root logger:

updateGlobalLogger rootLoggerName removeHandler

setHandlers :: LogHandler a => [a] -> Logger -> Logger

Set the 'Logger'\'s list of handlers to the list supplied. All existing handlers are removed first.

getLevel :: Logger -> Maybe Severities

Returns the "level" of the logger. Items beneath this level will be ignored.

setLevel :: Severities -> Logger -> Logger

Sets the "level" of the Logger. Returns a new Logger object with the new level.

clearLevel :: Logger -> Logger

Clears the "level" of the Logger. It will now inherit the level of | its parent.

Severity settings

setSeverities :: MonadIO m => LoggerName -> Severities -> m ()

Set severities for given logger. By default parent's severities are used.

setSeveritiesMaybe :: MonadIO m => LoggerName -> Maybe Severities -> m ()

Set or clear severities.

Saving Your Changes

saveGlobalLogger :: MonadIO m => Logger -> m ()

Updates the global record for the given logger to take into account any changes you may have made.

updateGlobalLogger

Arguments

:: MonadIO m

=> LoggerName

Logger name

-> (Logger -> Logger)

Function to call

-> m ()

Helps you make changes on the given logger. Takes a function that makes changes and writes those changes back to the global database. Here's an example from above ("s" is a LogHandler):

updateGlobalLogger "MyApp.BuggyComponent"
                   (setLevel DEBUG . setHandlers [s])

setPrefix :: MonadIO m => Maybe FilePath -> m ()

Sets file prefix to LogInternalState.

retrieveLogContent :: MonadIO m => FilePath -> Maybe Int -> m [Text]

Retrieves content of log file(s) given path (w/o _lcFilePrefix, as specified in your config). Example: there's component.log in config, but this function will return [component.log.122, component.log.123] if you want to. Content is file lines newest first.

FYI: this function is implemented to avoid the following problem: log-warper holds open handles to files, so trying to open log file for read would result in IOException.