System.Logger

Small layer on top of fast-logger which adds log-levels and timestamp support and not much more.

Settings

data Settings

defSettings :: Settings

Default settings:

• logLevel = Debug
• output = StdOut
• format = iso8601UTC
• delimiter = ", "
• netstrings = False
• bufSize = defaultBufSize
• name = Nothing

logLevel :: Settings -> Level

setLogLevel :: Level -> Settings -> Settings

logLevelOf :: Text -> Settings -> Maybe Level

Log level of some named logger.

setLogLevelOf :: Text -> Level -> Settings -> Settings

Specify a log level for the given named logger. When a logger is cloned and given a name, the logLevel of the cloned logger will be the provided here.

output :: Settings -> Output

setOutput :: Output -> Settings -> Settings

format :: Settings -> Maybe DateFormat

The time and date format used for the timestamp part of a log line.

setFormat :: Maybe DateFormat -> Settings -> Settings

delimiter :: Settings -> ByteString

Delimiter string which separates log line parts.

setDelimiter :: ByteString -> Settings -> Settings

netstrings :: Settings -> Bool

Whether to use netstring encoding for log lines.

setNetStrings :: Bool -> Settings -> Settings

bufSize :: Settings -> Int

setBufSize :: Int -> Settings -> Settings

name :: Settings -> Maybe Text

setName :: Maybe Text -> Settings -> Settings

Type definitions

data Logger

data Level

Constructors

Trace

Debug

Info

Warn

Error

Fatal

Instances

Eq Level

Ord Level

Read Level

Show Level

data Output

Constructors

StdOut

StdErr

Path FilePath

Instances

Eq Output

Ord Output

Show Output

newtype DateFormat

Constructors

DateFormat

Fields

display :: UnixTime -> ByteString

Instances

IsString DateFormat

iso8601UTC :: DateFormat

ISO 8601 date-time format.

Core API

new :: MonadIO m => Settings -> m Logger

Create a new Logger with the given Settings. Please note that the logLevel can be dynamically adjusted by setting the environment variable LOG_LEVEL accordingly. Likewise the buffer size can be dynamically set via LOG_BUFFER and netstrings encoding can be enabled with LOG_NETSTR=True

Since version 0.11 one can also use LOG_LEVEL_MAP to specify log levels per (named) logger. The syntax uses standard haskell syntax for association lists of type [(Text, Level)]. For example:

$ LOG_LEVEL=Info LOG_LEVEL_MAP='[("foo", Warn), ("bar", Trace)]' cabal repl
> g1 <- new defSettings
> let g2 = clone (Just "foo") g
> let g3 = clone (Just "bar") g
> let g4 = clone (Just "xxx") g
> logLevel (settings g1)
Info
> logLevel (settings g2)
Warn
> logLevel (settings g3)
Trace
> logLevel (settings g4)
Info

create :: MonadIO m => Output -> m Logger

Invokes new with default settings and the given output as log sink.

level :: Logger -> Level

Inspect this logger's threshold.

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

Force buffered bytes to output sink.

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

Closes the logger.

clone :: Maybe Text -> Logger -> Logger

Clone the given logger and optionally give it a name (use Nothing to clear).

If logLevelOf returns a custom Level for this name then the cloned logger will use it for its log messages.

settings :: Logger -> Settings

Logging

log :: MonadIO m => Logger -> Level -> (Msg -> Msg) -> m ()

Logs a message with the given level if greater or equal to the logger's threshold.

trace :: MonadIO m => Logger -> (Msg -> Msg) -> m ()

Abbreviation of log using the corresponding log level.

debug :: MonadIO m => Logger -> (Msg -> Msg) -> m ()

Abbreviation of log using the corresponding log level.

info :: MonadIO m => Logger -> (Msg -> Msg) -> m ()

Abbreviation of log using the corresponding log level.

warn :: MonadIO m => Logger -> (Msg -> Msg) -> m ()

Abbreviation of log using the corresponding log level.

err :: MonadIO m => Logger -> (Msg -> Msg) -> m ()

Abbreviation of log using the corresponding log level.

fatal :: MonadIO m => Logger -> (Msg -> Msg) -> m ()

Abbreviation of log using the corresponding log level.