katip-0.5.3.0: A structured logging framework.

Safe HaskellNone
LanguageHaskell2010

Katip

Contents

Description

Includes all of the APIs youll need to use Katip. Be sure to check out the included examples directory for an example of usage.

Here's a basic example:

import Control.Exception
import Katip

main :: IO ()
main = do
  handleScribe <- mkHandleScribe ColorIfTerminal stdout InfoS V2
  let makeLogEnv = registerScribe "stdout" handleScribe defaultScribeSettings =<< initLogEnv MyApp "production"
  -- closeScribes will stop accepting new logs, flush existing ones and clean up resources
  bracket makeLogEnv closeScribes $ le -> do
    let initialContext = () -- this context will be attached to every log in your app and merged w/ subsequent contexts
    let initialNamespace = "main"
    runKatipContextT le initialContext initialNamespace $ do
      $(logTM) InfoS "Hello Katip"
      -- This adds a namespace to the current namespace and merges a piece of contextual data into your context
      katipAddNamespace "additional_namespace" $ katipAddContext (sl "some_context" True) $ do
        $(logTM) WarningS "Now we're getting fancy"
      katipNoLogging $ do
        $(logTM) DebugS "You will never see this!"

Another common case that you have some sort of App monad that's based on ReaderT with some Config state. This is a perfect place to insert read-only katip state:

import Katip as K

data Config = Config {
  logNamespace :: K.Namespace
, logContext :: K.LogContexts
, logEnv :: K.LogEnv
-- whatever other read-only config you need
}

newtype App m a = App {
  unApp :: ReaderT Config m a
} deriving (Functor, Applicative, Monad) -- more instances as needed


-- These instances get even easier with lenses!
instance (MonadIO m) => K.Katip (App m) where
  getLogEnv = asks logEnv
  -- with lens:
  -- getLogEnv = view logEnv
  localLogEnv f (App m) = App (local (\s -> s { logEnv = f (logEnv s)}) m)
  -- with lens:
  -- localLogEnv f (App m) = App (local (over logEnv f) m)


instance (MonadIO m) => K.KatipContext (App m) where
  getKatipContext = asks logContext
  -- with lens:
  -- getKatipContext = view logContext
  localKatipContext f (App m) = App (local (\s -> s { logContext = f (logContext s)}) m)
  -- with lens:
  -- localKatipContext f (App m) = App (local (over logContext f) m)
  getKatipNamespace = asks logNamespace
  -- with lens:
  -- getKatipNamespace = view logNamespace
  localKatipNamespace f (App m) = App (local (\s -> s { logNamespace = f (logNamespace s)}) m)
  -- with lens:
  -- localKatipNamespace f (App m) = App (local (over logNamespace f) m)

To get up and running, the workflow is generally:

  • Set up a LogEnv using initLogEnv.
  • Add Scribes using registerScribe.
  • Either use KatipT or KatipContextT for a pre-built transformer stack or add Katip and KatipContext instances to your own transformer stack. If you do the latter, you may want to look in the examples dir for some tips on composing contexts and namespaces.
  • Define some structured log data throughout your application and implement ToObject and LogItem for them.
  • Begin logging with logT, logTM, etc.
  • Define your own Scribe if you need to output to some as-yet unsupported format or service. If you think it would be useful to others, consider releasing your own package.

Synopsis

Framework Types

newtype Namespace Source #

Represents a heirarchy of namespaces going from general to specific. For instance: ["processname", "subsystem"]. Note that single-segment namespaces can be created using IsString/OverloadedStrings, so "foo" will result in Namespace ["foo"].

Constructors

Namespace 

Fields

Instances

Eq Namespace Source # 
Ord Namespace Source # 
Read Namespace Source # 
Show Namespace Source # 
IsString Namespace Source # 
Generic Namespace Source # 

Associated Types

type Rep Namespace :: * -> * #

Semigroup Namespace Source # 
Monoid Namespace Source # 
Lift Namespace Source # 

Methods

lift :: Namespace -> Q Exp #

ToJSON Namespace Source # 
FromJSON Namespace Source # 
type Rep Namespace Source # 
type Rep Namespace = D1 * (MetaData "Namespace" "Katip.Core" "katip-0.5.3.0-2PEEU0mPhx1AjhH3VYo7Lw" True) (C1 * (MetaCons "Namespace" PrefixI True) (S1 * (MetaSel (Just Symbol "unNamespace") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 * [Text])))

newtype Environment Source #

Application environment, like prod, devel, testing.

Constructors

Environment 

Fields

Instances

Eq Environment Source # 
Ord Environment Source # 
Read Environment Source # 
Show Environment Source # 
IsString Environment Source # 
Generic Environment Source # 

Associated Types

type Rep Environment :: * -> * #

ToJSON Environment Source # 
FromJSON Environment Source # 
type Rep Environment Source # 
type Rep Environment = D1 * (MetaData "Environment" "Katip.Core" "katip-0.5.3.0-2PEEU0mPhx1AjhH3VYo7Lw" True) (C1 * (MetaCons "Environment" PrefixI True) (S1 * (MetaSel (Just Symbol "getEnvironment") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 * Text)))

data Severity Source #

Constructors

DebugS

Debug messages

InfoS

Information

NoticeS

Normal runtime Conditions

WarningS

General Warnings

ErrorS

General Errors

CriticalS

Severe situations

AlertS

Take immediate action

EmergencyS

System is unusable

Instances

Bounded Severity Source # 
Enum Severity Source # 
Eq Severity Source # 
Ord Severity Source # 
Read Severity Source # 
Show Severity Source # 
Generic Severity Source # 

Associated Types

type Rep Severity :: * -> * #

Methods

from :: Severity -> Rep Severity x #

to :: Rep Severity x -> Severity #

Lift Severity Source # 

Methods

lift :: Severity -> Q Exp #

ToJSON Severity Source # 
FromJSON Severity Source # 
type Rep Severity Source # 
type Rep Severity = D1 * (MetaData "Severity" "Katip.Core" "katip-0.5.3.0-2PEEU0mPhx1AjhH3VYo7Lw" False) ((:+:) * ((:+:) * ((:+:) * (C1 * (MetaCons "DebugS" PrefixI False) (U1 *)) (C1 * (MetaCons "InfoS" PrefixI False) (U1 *))) ((:+:) * (C1 * (MetaCons "NoticeS" PrefixI False) (U1 *)) (C1 * (MetaCons "WarningS" PrefixI False) (U1 *)))) ((:+:) * ((:+:) * (C1 * (MetaCons "ErrorS" PrefixI False) (U1 *)) (C1 * (MetaCons "CriticalS" PrefixI False) (U1 *))) ((:+:) * (C1 * (MetaCons "AlertS" PrefixI False) (U1 *)) (C1 * (MetaCons "EmergencyS" PrefixI False) (U1 *)))))

data Verbosity Source #

Verbosity controls the amount of information (columns) a Scribe emits during logging.

The convention is: - V0 implies no additional payload information is included in message. - V3 implies the maximum amount of payload information. - Anything in between is left to the discretion of the developer.

Constructors

V0 
V1 
V2 
V3 

Instances

Enum Verbosity Source # 
Eq Verbosity Source # 
Ord Verbosity Source # 
Read Verbosity Source # 
Show Verbosity Source # 
Generic Verbosity Source # 

Associated Types

type Rep Verbosity :: * -> * #

Lift Verbosity Source # 

Methods

lift :: Verbosity -> Q Exp #

type Rep Verbosity Source # 
type Rep Verbosity = D1 * (MetaData "Verbosity" "Katip.Core" "katip-0.5.3.0-2PEEU0mPhx1AjhH3VYo7Lw" False) ((:+:) * ((:+:) * (C1 * (MetaCons "V0" PrefixI False) (U1 *)) (C1 * (MetaCons "V1" PrefixI False) (U1 *))) ((:+:) * (C1 * (MetaCons "V2" PrefixI False) (U1 *)) (C1 * (MetaCons "V3" PrefixI False) (U1 *))))

class ToObject a where Source #

Katip requires JSON objects to be logged as context. This typeclass provides a default instance which uses ToJSON and produces an empty object if toJSON results in any type other than object. If you have a type you want to log that produces an Array or Number for example, you'll want to write an explicit instance here. You can trivially add a ToObject instance for something with a ToJSON instance like:

instance ToObject Foo

Methods

toObject :: a -> Object Source #

toObject :: ToJSON a => a -> Object Source #

class ToObject a => LogItem a where Source #

Payload objects need instances of this class. LogItem makes it so that you can have very verbose items getting logged with lots of extra fields but under normal circumstances, if your scribe is configured for a lower verbosity level, it will only log a selection of those keys. Furthermore, each Scribe can be configured with a different Verbosity level. You could even use registerScribe, unregisterScribe, and clearScribes to at runtime swap out your existing scribes for more verbose debugging scribes if you wanted to.

When defining payloadKeys, don't redundantly declare the same keys for higher levels of verbosity. Each level of verbosity automatically and recursively contains all keys from the level before it.

Minimal complete definition

payloadKeys

Methods

payloadKeys :: Verbosity -> a -> PayloadSelection Source #

List of keys in the JSON object that should be included in message.

data Item a Source #

This has everything each log message will contain.

Instances

Functor Item Source # 

Methods

fmap :: (a -> b) -> Item a -> Item b #

(<$) :: a -> Item b -> Item a #

Eq a => Eq (Item a) Source # 

Methods

(==) :: Item a -> Item a -> Bool #

(/=) :: Item a -> Item a -> Bool #

Show a => Show (Item a) Source # 

Methods

showsPrec :: Int -> Item a -> ShowS #

show :: Item a -> String #

showList :: [Item a] -> ShowS #

Generic (Item a) Source # 

Associated Types

type Rep (Item a) :: * -> * #

Methods

from :: Item a -> Rep (Item a) x #

to :: Rep (Item a) x -> Item a #

ToJSON a => ToJSON (Item a) Source # 
FromJSON a => FromJSON (Item a) Source # 
type Rep (Item a) Source # 
type Rep (Item a) = D1 * (MetaData "Item" "Katip.Core" "katip-0.5.3.0-2PEEU0mPhx1AjhH3VYo7Lw" False) (C1 * (MetaCons "Item" PrefixI True) ((:*:) * ((:*:) * ((:*:) * (S1 * (MetaSel (Just Symbol "_itemApp") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 * Namespace)) (S1 * (MetaSel (Just Symbol "_itemEnv") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 * Environment))) ((:*:) * (S1 * (MetaSel (Just Symbol "_itemSeverity") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 * Severity)) ((:*:) * (S1 * (MetaSel (Just Symbol "_itemThread") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 * ThreadIdText)) (S1 * (MetaSel (Just Symbol "_itemHost") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 * HostName))))) ((:*:) * ((:*:) * (S1 * (MetaSel (Just Symbol "_itemProcess") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 * ProcessID)) ((:*:) * (S1 * (MetaSel (Just Symbol "_itemPayload") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 * a)) (S1 * (MetaSel (Just Symbol "_itemMessage") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 * LogStr)))) ((:*:) * (S1 * (MetaSel (Just Symbol "_itemTime") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 * UTCTime)) ((:*:) * (S1 * (MetaSel (Just Symbol "_itemNamespace") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 * Namespace)) (S1 * (MetaSel (Just Symbol "_itemLoc") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 * (Maybe Loc))))))))

data Scribe Source #

Scribes are handlers of incoming items. Each registered scribe knows how to push a log item somewhere.

Guidelines for writing your own Scribe

Scribes should always take a Severity and Verbosity.

Severity is used to *exclude log messages* that are < the provided Severity. For instance, if the user passes InfoS, DebugS items should be ignored. Katip provides the permitItem utility for this.

Verbosity is used to select keys from the log item's payload. Each LogItem instance describes what keys should be retained for each Verbosity level. Use the payloadObject utility for extracting the keys that should be permitted.

There is no built-in mechanism in katip for telling a scribe that its time to shut down. unregisterScribe merely drops it from the LogEnv. This means there are 2 ways to handle resources as a scribe:

  1. Pass in the resource when the scribe is created. Handle allocation and release of the resource elsewhere. This is what the Handle scribe does.
  2. Return a finalizing function that tells the scribe to shut down. katip-elasticsearch's mkEsScribe returns an IO (Scribe, IO ()). The finalizer will flush any queued log messages and shut down gracefully before returning. This can be hooked into your application's shutdown routine to ensure you never miss any log messages on shutdown.

Constructors

Scribe 

Fields

  • liPush :: forall a. LogItem a => Item a -> IO ()
     
  • scribeFinalizer :: IO ()

    Provide a *blocking* finalizer to call when your scribe is removed. If this is not relevant to your scribe, return () is fine.

data LogEnv Source #

Constructors

LogEnv 

Fields

data SimpleLogPayload Source #

Instances

Semigroup SimpleLogPayload Source # 
Monoid SimpleLogPayload Source # 
ToJSON SimpleLogPayload Source #

A built-in convenience log payload that won't log anything on V0, but will log everything in any other level of verbosity. Intended for easy in-line usage without having to define new log types.

Construct using sl and combine multiple tuples using <> from Monoid.

LogItem SimpleLogPayload Source # 
ToObject SimpleLogPayload Source # 

sl :: ToJSON a => Text -> a -> SimpleLogPayload Source #

Construct a simple log from any JSON item.

defaultScribeSettings :: ScribeSettings Source #

Reasonable defaults for a scribe. Buffer size of 4096.

lens-compatible Lenses

itemApp :: forall a. Lens' (Item a) Namespace Source #

itemHost :: forall a. Lens' (Item a) HostName Source #

itemPayload :: forall a a. Lens (Item a) (Item a) a a Source #

itemMessage :: forall a. Lens' (Item a) LogStr Source #

itemTime :: forall a. Lens' (Item a) UTCTime Source #

itemLoc :: forall a. Lens' (Item a) (Maybe Loc) Source #

A Built-in Monad For Simple Logging

newtype KatipT m a Source #

A concrete monad you can use to run logging actions. Use this if you prefer an explicit monad transformer stack and adding layers as opposed to implementing Katip for your monad.

Constructors

KatipT 

Fields

Instances

MonadTrans KatipT Source # 

Methods

lift :: Monad m => m a -> KatipT m a #

MonadTransControl KatipT Source # 

Associated Types

type StT (KatipT :: (* -> *) -> * -> *) a :: * #

Methods

liftWith :: Monad m => (Run KatipT -> m a) -> KatipT m a #

restoreT :: Monad m => m (StT KatipT a) -> KatipT m a #

MonadBase b m => MonadBase b (KatipT m) Source # 

Methods

liftBase :: b α -> KatipT m α #

MonadBaseControl b m => MonadBaseControl b (KatipT m) Source # 

Associated Types

type StM (KatipT m :: * -> *) a :: * #

Methods

liftBaseWith :: (RunInBase (KatipT m) b -> b a) -> KatipT m a #

restoreM :: StM (KatipT m) a -> KatipT m a #

Monad m => Monad (KatipT m) Source # 

Methods

(>>=) :: KatipT m a -> (a -> KatipT m b) -> KatipT m b #

(>>) :: KatipT m a -> KatipT m b -> KatipT m b #

return :: a -> KatipT m a #

fail :: String -> KatipT m a #

Functor m => Functor (KatipT m) Source # 

Methods

fmap :: (a -> b) -> KatipT m a -> KatipT m b #

(<$) :: a -> KatipT m b -> KatipT m a #

Applicative m => Applicative (KatipT m) Source # 

Methods

pure :: a -> KatipT m a #

(<*>) :: KatipT m (a -> b) -> KatipT m a -> KatipT m b #

liftA2 :: (a -> b -> c) -> KatipT m a -> KatipT m b -> KatipT m c #

(*>) :: KatipT m a -> KatipT m b -> KatipT m b #

(<*) :: KatipT m a -> KatipT m b -> KatipT m a #

MonadIO m => MonadIO (KatipT m) Source # 

Methods

liftIO :: IO a -> KatipT m a #

MonadThrow m => MonadThrow (KatipT m) Source # 

Methods

throwM :: Exception e => e -> KatipT m a #

MonadCatch m => MonadCatch (KatipT m) Source # 

Methods

catch :: Exception e => KatipT m a -> (e -> KatipT m a) -> KatipT m a #

MonadMask m => MonadMask (KatipT m) Source # 

Methods

mask :: ((forall a. KatipT m a -> KatipT m a) -> KatipT m b) -> KatipT m b #

uninterruptibleMask :: ((forall a. KatipT m a -> KatipT m a) -> KatipT m b) -> KatipT m b #

generalBracket :: KatipT m a -> (a -> KatipT m ignored1) -> (a -> SomeException -> KatipT m ignored2) -> (a -> KatipT m b) -> KatipT m b #

MonadUnliftIO m => MonadUnliftIO (KatipT m) Source # 

Methods

askUnliftIO :: KatipT m (UnliftIO (KatipT m)) #

withRunInIO :: ((forall a. KatipT m a -> IO a) -> IO b) -> KatipT m b #

MonadIO m => Katip (KatipT m) Source # 
(Monad m, KatipContext m) => KatipContext (KatipT m) Source # 
type StT KatipT a Source # 
type StT KatipT a = a
type StM (KatipT m) a Source # 
type StM (KatipT m) a = ComposeSt KatipT m a

runKatipT :: LogEnv -> KatipT m a -> m a Source #

Execute KatipT on a log env.

Initializing Loggers

initLogEnv Source #

Arguments

:: Namespace

A base namespace for this application

-> Environment

Current run environment (e.g. prod vs. devel)

-> IO LogEnv 

Create a reasonable default InitLogEnv. Uses an AutoUdate with the default settings as the timer. If you are concerned about timestamp precision or event ordering in log outputs like ElasticSearch, you should replace the timer with getCurrentTime

registerScribe Source #

Arguments

:: Text

Name the scribe

-> Scribe 
-> ScribeSettings 
-> LogEnv 
-> IO LogEnv 

Add a scribe to the list. All future log calls will go to this scribe in addition to the others.

Dropping scribes temporarily

unregisterScribe Source #

Arguments

:: Text

Name of the scribe

-> LogEnv 
-> LogEnv 

Remove a scribe from the environment. This does *not* finalize the scribe. This mainly only makes sense to use with something like MonadReader's local function to temporarily disavow a single logger for a block of code.

clearScribes :: LogEnv -> LogEnv Source #

Unregister *all* scribes. Note that this is *not* for closing or finalizing scribes, use closeScribes for that. This mainly only makes sense to use with something like MonadReader's local function to temporarily disavow any loggers for a block of code.

Finalizing scribes at shutdown

closeScribes :: LogEnv -> IO LogEnv Source #

Call this at the end of your program. This is a blocking call that stop writing to a scribe's queue, waits for the queue to empty, finalizes each scribe in the log environment and then removes it. Finalizers are all run even if one of them throws, but the exception will be re-thrown at the end.

closeScribe Source #

Arguments

:: Text

Name of the scribe

-> LogEnv 
-> IO LogEnv 

Finalize a scribe. The scribe is removed from the environment, its finalizer is called and it can never be written to again. Note that this will throw any exceptions yoru finalizer will throw, and that LogEnv is immutable, so it will not be removed in that case.

Logging Functions

newtype LogStr Source #

Log message with Builder underneath; use <> to concat in O(1).

Constructors

LogStr 

Fields

Instances

Eq LogStr Source # 

Methods

(==) :: LogStr -> LogStr -> Bool #

(/=) :: LogStr -> LogStr -> Bool #

Show LogStr Source # 
IsString LogStr Source # 

Methods

fromString :: String -> LogStr #

Generic LogStr Source # 

Associated Types

type Rep LogStr :: * -> * #

Methods

from :: LogStr -> Rep LogStr x #

to :: Rep LogStr x -> LogStr #

Semigroup LogStr Source # 
Monoid LogStr Source # 
FromJSON LogStr Source # 
type Rep LogStr Source # 
type Rep LogStr = D1 * (MetaData "LogStr" "Katip.Core" "katip-0.5.3.0-2PEEU0mPhx1AjhH3VYo7Lw" True) (C1 * (MetaCons "LogStr" PrefixI True) (S1 * (MetaSel (Just Symbol "unLogStr") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 * Builder)))

logStr :: StringConv a Text => a -> LogStr Source #

Pack any string-like thing into a LogStr. This will automatically work on String, ByteString, Text and any of the lazy variants.

ls :: StringConv a Text => a -> LogStr Source #

Shorthand for logStr

showLS :: Show a => a -> LogStr Source #

Convert any showable type into a LogStr.

Katip LoggingFunctions

These logging functions use the basic Katip constraint and thus will require varying degrees of explicit detail such as Namespace and individual log items to be passed in. These can be described as the primitives of Katip logging. If you find yourself making multiple log statements within a logical logging context for your app, you may want to look into the KatipContext family of logging functions like logFM and logTM. KatipContext in most applications should be considered the default. Here's an example of the pain point:

doDatabaseThings = do
  connId <- getConnectionId
  logF (ConnectionIDContext connId) "database" InfoS "Doing database stuff"
  -- ...
  logF (ConnectionIDContext connId) "database" InfoS "Wow, passing in the same context is getting tedious"

Another pain point to look out for is nesting actions that log in each other. Let's say you were writing a web app. You want to capture some detail such as the user's ID in the logs, but you also want that info to show up in doDatabaseThings' logs so you can associate those two pieces of information:

webRequestHandler = do
  uid <- getUserId
  logF (UserIDContext uid) "web" InfoS "Starting web request"
  doDatabaseThings

In the above example, doDatabaseThings would overwrite that UserIDContext with its own context and namespace. Sometimes this is what you want and that's why logF and other functions which only require Katip exist. If you are interested in combining log contexts and namespaces, see KatipContext.

class MonadIO m => Katip m where Source #

Monads where katip logging actions can be performed. Katip is the most basic logging monad. You will typically use this directly if you either don't want to use namespaces/contexts heavily or if you want to pass in specific contexts and/or namespaces at each log site.

For something more powerful, look at the docs for KatipContext, which keeps a namespace and merged context. You can write simple functions that add additional namespacing and merges additional context on the fly.

localLogEnv was added to allow for lexically-scoped modifications of the log env that are reverted when the supplied monad completes. katipNoLogging, for example, uses this to temporarily pause log outputs.

Minimal complete definition

getLogEnv, localLogEnv

Methods

getLogEnv :: m LogEnv Source #

localLogEnv :: (LogEnv -> LogEnv) -> m a -> m a Source #

Instances

Katip m => Katip (MaybeT m) Source # 
Katip m => Katip (ResourceT m) Source # 
MonadIO m => Katip (KatipT m) Source # 
MonadIO m => Katip (NoLoggingT m) Source # 
MonadIO m => Katip (KatipContextT m) Source # 
Katip m => Katip (ExceptT s m) Source # 

Methods

getLogEnv :: ExceptT s m LogEnv Source #

localLogEnv :: (LogEnv -> LogEnv) -> ExceptT s m a -> ExceptT s m a Source #

(Katip m, Monoid s) => Katip (WriterT s m) Source # 

Methods

getLogEnv :: WriterT s m LogEnv Source #

localLogEnv :: (LogEnv -> LogEnv) -> WriterT s m a -> WriterT s m a Source #

Katip m => Katip (StateT s m) Source # 

Methods

getLogEnv :: StateT s m LogEnv Source #

localLogEnv :: (LogEnv -> LogEnv) -> StateT s m a -> StateT s m a Source #

Katip m => Katip (StateT s m) Source # 

Methods

getLogEnv :: StateT s m LogEnv Source #

localLogEnv :: (LogEnv -> LogEnv) -> StateT s m a -> StateT s m a Source #

(Katip m, Monoid s) => Katip (WriterT s m) Source # 

Methods

getLogEnv :: WriterT s m LogEnv Source #

localLogEnv :: (LogEnv -> LogEnv) -> WriterT s m a -> WriterT s m a Source #

Katip m => Katip (ReaderT * s m) Source # 

Methods

getLogEnv :: ReaderT * s m LogEnv Source #

localLogEnv :: (LogEnv -> LogEnv) -> ReaderT * s m a -> ReaderT * s m a Source #

(Katip m, Monoid w) => Katip (RWST r w s m) Source # 

Methods

getLogEnv :: RWST r w s m LogEnv Source #

localLogEnv :: (LogEnv -> LogEnv) -> RWST r w s m a -> RWST r w s m a Source #

(Katip m, Monoid w) => Katip (RWST r w s m) Source # 

Methods

getLogEnv :: RWST r w s m LogEnv Source #

localLogEnv :: (LogEnv -> LogEnv) -> RWST r w s m a -> RWST r w s m a Source #

logF Source #

Arguments

:: (Applicative m, LogItem a, Katip m) 
=> a

Contextual payload for the log

-> Namespace

Specific namespace of the message.

-> Severity

Severity of the message

-> LogStr

The log message

-> m () 

Log with full context, but without any code location.

logMsg :: (Applicative m, Katip m) => Namespace -> Severity -> LogStr -> m () Source #

Log a message without any payload/context or code location.

logT :: ExpQ Source #

Loc-tagged logging when using template-haskell.

$(logT) obj mempty InfoS "Hello world"

logItem :: (Applicative m, LogItem a, Katip m) => a -> Namespace -> Maybe Loc -> Severity -> LogStr -> m () Source #

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

logException Source #

Arguments

:: (Katip m, LogItem a, MonadCatch m, Applicative m) 
=> a

Log context

-> Namespace

Namespace

-> Severity

Severity

-> m b

Main action being run

-> m b 

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

>>> > logException () mempty ErrorS (error "foo")

KatipContext: Logging With Context

These logging functions use the KatipContext constraint which is a superclass of Katip that also has a mechanism for keeping track of the current context and namespace. This means a few things:

  1. Functions that use KatipContext like logFM and logTM do not require you to pass in LogItems or Namespaces, they pull them from the monadic environment.
  2. It becomes easy to add functions which add namespaces and/or contexts to the current stack of them. You can (and should) make that action scoped to a monadic action so that when it finishes, the previous context and namespace will be automatically restored.

KatipContextT provides a simple, ReaderT-based implementation of the KatipContext typeclass, and provides katipAddContext and katipAddNamespace functions to append to the context for the duration of a block:

main = do
  le <- initLogEnv MyApp "production"
  -- set up scribes here
  runKatipContext le () "main" $ do
    katipAddNamespace "nextlevel" $ do
      $(logTM) InfoS "Logs here will have namespace MyApp.main.nextlevel"

    katipAddContext TrivialContext $ do
      $(logTM) InfoS "Logs here will have context from TrivialContext"

      katipAddContext AnotherContext $ do
        $(logTM) InfoS "Logs here will have context from TrivialContext *merged with* context from AnotherContext!"

    $(logTM) InfoS "Log context restored to () and namespace to MyApp.main"

katipAddNamespace and katipAddContext are one-liners, implemented in terms of local from MonadReader. If you have a custom monad transformer stack and want to add your own version of these, check out <https://github.com/Soostone/katip/tree/master/katip/examples these examples>.

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. The local variants are just like local from Reader and indeed you can easily implement them with local if you happen to be using a Reader in your monad. These give us katipAddNamespace and katipAddContext that works with *any* KatipContext, as opposed to making users have to implement these functions on their own in each app.

Methods

getKatipContext :: m LogContexts Source #

localKatipContext :: (LogContexts -> LogContexts) -> m a -> m a Source #

Temporarily modify the current context for the duration of the supplied monad. Used in katipAddContext

getKatipNamespace :: m Namespace Source #

localKatipNamespace :: (Namespace -> Namespace) -> m a -> m a Source #

Temporarily modify the current namespace for the duration of the supplied monad. Used in katipAddNamespace

Instances

(KatipContext m, Katip (ListT m)) => KatipContext (ListT m) Source # 
(KatipContext m, Katip (MaybeT m)) => KatipContext (MaybeT m) Source # 
(KatipContext m, Katip (ResourceT m)) => KatipContext (ResourceT m) Source # 
(Monad m, KatipContext m) => KatipContext (KatipT m) Source # 
MonadIO m => KatipContext (NoLoggingT m) Source # 
MonadIO m => KatipContext (KatipContextT m) Source # 
(KatipContext m, Katip (IdentityT * m)) => KatipContext (IdentityT * m) Source # 
(KatipContext m, Katip (ExceptT e m)) => KatipContext (ExceptT e m) Source # 
(Monoid w, KatipContext m, Katip (WriterT w m)) => KatipContext (WriterT w m) Source # 
(KatipContext m, Katip (StateT s m)) => KatipContext (StateT s m) Source # 
(KatipContext m, Katip (StateT s m)) => KatipContext (StateT s m) Source # 
(Monoid w, KatipContext m, Katip (WriterT w m)) => KatipContext (WriterT w m) Source # 
(KatipContext m, Katip (ReaderT * r m)) => KatipContext (ReaderT * r m) Source # 
(Monoid w, KatipContext m, Katip (RWST r w s m)) => KatipContext (RWST r w s m) Source # 
(Monoid w, KatipContext m, Katip (RWST r w s m)) => KatipContext (RWST r w s m) Source # 

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"

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. Automatically supplies 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

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.

Temporarily Changing Logging Behavior

katipAddNamespace :: KatipContext m => Namespace -> m a -> m a Source #

Append a namespace segment to the current namespace for the given monadic action, then restore the previous state afterwards. Works with anything implementing KatipContext.

katipAddContext :: (LogItem i, KatipContext m) => i -> m a -> 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. Works with anything implementing KatipContext.

katipNoLogging :: Katip m => m a -> m a Source #

Disable all scribes for the given monadic action, then restore them afterwards. Works in any Katip monad.

Included Scribes

mkHandleScribe :: ColorStrategy -> Handle -> Severity -> Verbosity -> IO Scribe Source #

Logs to a file handle such as stdout, stderr, or a file. Contexts and other information will be flattened out into bracketed fields. For example:

[2016-05-11 21:01:15][MyApp][Info][myhost.example.com][1724][ThreadId 1154][main:Helpers.Logging Helpers/Logging.hs:32:7] Started
[2016-05-11 21:01:15][MyApp.confrabulation][Debug][myhost.example.com][1724][ThreadId 1154][confrab_factor:42.0][main:Helpers.Logging Helpers/Logging.hs:41:9] Confrabulating widgets, with extra namespace and context
[2016-05-11 21:01:15][MyApp][Info][myhost.example.com][1724][ThreadId 1154][main:Helpers.Logging Helpers/Logging.hs:43:7] Namespace and context are back to normal

Returns the newly-created Scribe. The finalizer flushes the handle. Handle mode is set to LineBuffering automatically.

mkFileScribe :: FilePath -> Severity -> Verbosity -> IO Scribe Source #

A specialization of mkHandleScribe that takes a FilePath instead of a Handle. It is responsible for opening the file in AppendMode and will close the file handle on 'closeScribe'/'closeScribes'. Does not do log coloring. Sets handle to LineBuffering mode.

data ColorStrategy Source #

Constructors

ColorLog Bool

Whether to use color control chars in log output

ColorIfTerminal

Color if output is a terminal

Tools for implementing Scribes

permitItem :: Severity -> Item a -> Bool Source #

Should this item be logged given the user's maximum severity?

payloadObject :: LogItem a => Verbosity -> a -> Object Source #

Constrain payload based on verbosity. Backends should use this to automatically bubble higher verbosity levels to lower ones.

itemJson :: LogItem a => Verbosity -> Item a -> Value Source #

Convert log item to its JSON representation while trimming its payload based on the desired verbosity. Backends that push JSON messages should use this to obtain their payload.

KatipContextT - Utility transformer that provides Katip and KatipContext instances

data KatipContextT m a Source #

Provides a simple transformer that defines a KatipContext instance for a fixed namespace and context. Just like KatipT, you should use this if you prefer an explicit transformer stack and don't want to (or cannot) define KatipContext for your monad . 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 # 

Methods

lift :: Monad m => m a -> KatipContextT m a #

MonadTransControl KatipContextT Source # 

Associated Types

type StT (KatipContextT :: (* -> *) -> * -> *) a :: * #

Methods

liftWith :: Monad m => (Run KatipContextT -> m a) -> KatipContextT m a #

restoreT :: Monad m => m (StT KatipContextT a) -> KatipContextT m a #

MonadBase b m => MonadBase b (KatipContextT m) Source # 

Methods

liftBase :: b α -> KatipContextT m α #

MonadBaseControl b m => MonadBaseControl b (KatipContextT m) Source # 

Associated Types

type StM (KatipContextT m :: * -> *) a :: * #

MonadWriter w m => MonadWriter w (KatipContextT m) Source # 

Methods

writer :: (a, w) -> KatipContextT m a #

tell :: w -> KatipContextT m () #

listen :: KatipContextT m a -> KatipContextT m (a, w) #

pass :: KatipContextT m (a, w -> w) -> KatipContextT m a #

MonadState s m => MonadState s (KatipContextT m) Source # 

Methods

get :: KatipContextT m s #

put :: s -> KatipContextT m () #

state :: (s -> (a, s)) -> KatipContextT m a #

MonadReader r m => MonadReader r (KatipContextT m) Source # 

Methods

ask :: KatipContextT m r #

local :: (r -> r) -> KatipContextT m a -> KatipContextT m a #

reader :: (r -> a) -> KatipContextT m a #

MonadError e m => MonadError e (KatipContextT m) Source # 

Methods

throwError :: e -> KatipContextT m a #

catchError :: KatipContextT m a -> (e -> KatipContextT m a) -> KatipContextT m a #

Monad m => Monad (KatipContextT m) Source # 

Methods

(>>=) :: KatipContextT m a -> (a -> KatipContextT m b) -> KatipContextT m b #

(>>) :: KatipContextT m a -> KatipContextT m b -> KatipContextT m b #

return :: a -> KatipContextT m a #

fail :: String -> KatipContextT m a #

Functor m => Functor (KatipContextT m) Source # 

Methods

fmap :: (a -> b) -> KatipContextT m a -> KatipContextT m b #

(<$) :: a -> KatipContextT m b -> KatipContextT m a #

MonadFix m => MonadFix (KatipContextT m) Source # 

Methods

mfix :: (a -> KatipContextT m a) -> KatipContextT m a #

Applicative m => Applicative (KatipContextT m) Source # 

Methods

pure :: a -> KatipContextT m a #

(<*>) :: KatipContextT m (a -> b) -> KatipContextT m a -> KatipContextT m b #

liftA2 :: (a -> b -> c) -> KatipContextT m a -> KatipContextT m b -> KatipContextT m c #

(*>) :: KatipContextT m a -> KatipContextT m b -> KatipContextT m b #

(<*) :: KatipContextT m a -> KatipContextT m b -> KatipContextT m a #

Alternative m => Alternative (KatipContextT m) Source # 
MonadPlus m => MonadPlus (KatipContextT m) Source # 
MonadIO m => MonadIO (KatipContextT m) Source # 

Methods

liftIO :: IO a -> KatipContextT m a #

MonadThrow m => MonadThrow (KatipContextT m) Source # 

Methods

throwM :: Exception e => e -> KatipContextT m a #

MonadCatch m => MonadCatch (KatipContextT m) Source # 

Methods

catch :: Exception e => KatipContextT m a -> (e -> KatipContextT m a) -> KatipContextT m a #

MonadMask m => MonadMask (KatipContextT m) Source # 

Methods

mask :: ((forall a. KatipContextT m a -> KatipContextT m a) -> KatipContextT m b) -> KatipContextT m b #

uninterruptibleMask :: ((forall a. KatipContextT m a -> KatipContextT m a) -> KatipContextT m b) -> KatipContextT m b #

generalBracket :: KatipContextT m a -> (a -> KatipContextT m ignored1) -> (a -> SomeException -> KatipContextT m ignored2) -> (a -> KatipContextT m b) -> KatipContextT m b #

MonadUnliftIO m => MonadUnliftIO (KatipContextT m) Source # 

Methods

askUnliftIO :: KatipContextT m (UnliftIO (KatipContextT m)) #

withRunInIO :: ((forall a. KatipContextT m a -> IO a) -> IO b) -> KatipContextT m b #

MonadIO m => Katip (KatipContextT m) Source # 
MonadIO m => KatipContext (KatipContextT m) Source # 
type StT KatipContextT a Source # 
type StM (KatipContextT m) a Source #