72 lines
2.1 KiB
Haskell
72 lines
2.1 KiB
Haskell
-- blantantly taken from hakyll
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-- http://hackage.haskell.org/packages/archive/hakyll/3.1.1.0/doc/html/src/Hakyll-Core-Logger.html
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--
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-- | Produce pretty, thread-safe logs
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--
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{-# LANGUAGE BangPatterns #-}
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module Yesod.Logger
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( Logger
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, makeLogger
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, flushLogger
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, timed
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) where
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import Control.Monad (forever)
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import Control.Monad.Trans (MonadIO, liftIO)
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import Control.Applicative ((<$>), (<*>))
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import Control.Concurrent (forkIO)
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import Control.Concurrent.Chan.Strict (Chan, newChan, readChan, writeChan)
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import Control.Concurrent.MVar.Strict (MVar, newEmptyMVar, takeMVar, putMVar)
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import Text.Printf (printf)
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import Data.Time (getCurrentTime, diffUTCTime)
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data Logger = Logger
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{ loggerChan :: Chan (Maybe String) -- Nothing marks the end
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, loggerSync :: MVar () -- Used for sync on quit
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}
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makeLogger :: IO Logger
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makeLogger = do
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logger <- Logger <$> newChan <*> newEmptyMVar
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_ <- forkIO $ loggerThread logger
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return logger
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where
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loggerThread logger = forever $ do
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msg <- readChan $ loggerChan logger
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case msg of
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-- Stop: sync
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Nothing -> putMVar (loggerSync logger) ()
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-- Print and continue
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Just m -> putStrLn m
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-- | Flush the logger (blocks until flushed)
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--
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flushLogger :: Logger -> IO ()
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flushLogger logger = do
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writeChan (loggerChan logger) Nothing
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() <- takeMVar $ loggerSync logger
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return ()
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-- | Send a raw message to the logger
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--
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message :: Logger -> String -> IO ()
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message logger = writeChan (loggerChan logger) . Just
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-- | Execute a monadic action and log the duration
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--
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timed :: MonadIO m
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=> Logger -- ^ Logger
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-> String -- ^ Message
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-> m a -- ^ Action
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-> m a -- ^ Timed and logged action
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timed logger msg action = do
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start <- liftIO getCurrentTime
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!result <- action
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stop <- liftIO getCurrentTime
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let diff = fromEnum $ diffUTCTime stop start
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ms = diff `div` 10 ^ (9 :: Int)
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formatted = printf " [%4dms] %s" ms msg
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liftIO $ message logger formatted
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return result
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