katip-0.3.1.4: A structured logging framework.

Safe HaskellNone
LanguageHaskell2010

Katip.Monadic

Contents

Description

Provides support for treating payloads and namespaces as composable contexts. The common pattern would be to provide a KatipContext instance for your base monad.

Synopsis

Monadic variants of logging functions from Katip.Core

logFM Source

Arguments

:: (Applicative m, KatipContext m) 
=> Severity

Severity of the message

-> LogStr

The log message

-> m () 

Log with full context, but without any code location. Automatically supplies payload and namespace.

logTM :: ExpQ Source

Loc-tagged logging when using template-haskell. Automatically supplies payload and namespace.

$(logTM) InfoS "Hello world"

logLocM :: (Applicative m, KatipContext m) => Severity -> LogStr -> m () Source

Loc-tagged logging when using template-haskell. Automatically supplies payload and namespace.

Same consideration as logLoc applies.

This function does not require template-haskell as it automatically uses implicit-callstacks when the code is compiled using GHC > 7.8. Using an older version of the compiler will result in the emission of a log line without any location information, so be aware of it. Users using GHC <= 7.8 may want to use the template-haskell function logTM for maximum compatibility.

logLocM InfoS "Hello world"

logItemM :: (Applicative m, KatipContext m) => Maybe Loc -> Severity -> LogStr -> m () Source

Log with everything, including a source code location. This is very low level and you typically can use logTM in its place. Automaticallysupplies payload and namespace.

logExceptionM Source

Arguments

:: (KatipContext m, MonadCatch m, Applicative m) 
=> m a

Main action to run

-> Severity

Severity

-> m a 

Perform an action while logging any exceptions that may occur. Inspired by onException.

>>> > error "foo" `logExceptionM` ErrorS

Machinery for merging typed log payloads/contexts

class Katip m => KatipContext m where Source

A monadic context that has an inherant way to get logging context and namespace. Examples include a web application monad or database monad.

data AnyLogContext Source

A wrapper around a log context that erases type information so that contexts from multiple layers can be combined intelligently.

data LogContexts Source

Heterogeneous list of log contexts that provides a smart LogContext instance for combining multiple payload policies. This is critical for log contexts deep down in a stack to be able to inject their own context without worrying about other context that has already been set. Also note that contexts are treated as a sequence and <> will be appended to the right hand side of the sequence. If there are conflicting keys in the contexts, the /right side will take precedence/, which is counter to how monoid works for Map and HashMap, so bear that in mind. The reasoning is that if the user is sequentially adding contexts to the right side of the sequence, on conflict the intent is to overwrite with the newer value (i.e. the rightmost value).

Additional note: you should not mappend LogContexts in any sort of infinite loop, as it retains all data, so that would be a memory leak.

liftPayload :: LogItem a => a -> LogContexts Source

Lift a log context into the generic wrapper so that it can combine with the existing log context.

KatipContextT - Utility transformer that provides Katip and KatipContext instances

newtype KatipContextT m a Source

Provides a simple transformer that defines a KatipContext instance for a fixed namespace and context. You will typically only use this if you are forced to run in IO but still want to have your log context. This is the slightly more powerful version of KatipT in that it provides KatipContext instead of just Katip. For instance:

  threadWithLogging = do
    le <- getLogEnv
    ctx <- getKatipContext
    ns <- getKatipNamespace
    forkIO $ runKatipContextT le ctx ns $ do
      $(logTM) InfoS "Look, I can log in IO and retain context!"
      doOtherStuff

Instances

MonadTrans KatipContextT Source 
MonadTransControl KatipContextT Source 
MonadError e m => MonadError e (KatipContextT m) Source 
MonadReader r m => MonadReader r (KatipContextT m) Source 
MonadState s m => MonadState s (KatipContextT m) Source 
MonadWriter w m => MonadWriter w (KatipContextT m) Source 
MonadBase b m => MonadBase b (KatipContextT m) Source 
MonadBaseControl b m => MonadBaseControl b (KatipContextT m) Source 
Monad m => Monad (KatipContextT m) Source 
Functor m => Functor (KatipContextT m) Source 
MonadFix m => MonadFix (KatipContextT m) Source 
Applicative m => Applicative (KatipContextT m) Source 
Alternative m => Alternative (KatipContextT m) Source 
MonadPlus m => MonadPlus (KatipContextT m) Source 
MonadIO m => MonadIO (KatipContextT m) Source 
MonadThrow m => MonadThrow (KatipContextT m) Source 
MonadMask m => MonadMask (KatipContextT m) Source 
MonadCatch m => MonadCatch (KatipContextT m) Source 
MonadIO m => Katip (KatipContextT m) Source 
MonadIO m => KatipContext (KatipContextT m) Source 
type StT KatipContextT a = StT (ReaderT KatipContextTState) a Source 
type StM (KatipContextT m) a = ComposeSt KatipContextT m a Source 

katipAddNamespace :: Monad m => Namespace -> KatipContextT m a -> KatipContextT m a Source

Append a namespace segment to the current namespace for the given monadic action, then restore the previous state afterwards.

katipAddContext :: (LogItem i, Monad m) => i -> KatipContextT m a -> KatipContextT m a Source

Append some context to the current context for the given monadic action, then restore the previous state afterwards. Important note: be careful using this in a loop. If you're using something like forever or replicateM_ that does explicit sharing to avoid a memory leak, youll be fine as it will *sequence* calls to katipAddNamespace, so each loop will get the same context added. If you instead roll your own recursion and you're recursing in the action you provide, you'll instead accumulate tons of redundant contexts and even if they all merge on log, they are stored in a sequence and will leak memory.

katipNoLogging :: Monad m => KatipContextT m a -> KatipContextT m a Source

Disable all scribes for the given monadic action, then restore them afterwards.