Safe Haskell	None
Language	Haskell2010

Control.Monad.Trace.Class

Contents

Types
Generating traces
Annotating traces

Description

This module exposes the generic MonadTrace class.

Synopsis

data Span = Span {
- spanName :: !Name
- spanContext :: !Context
- spanReferences :: !(Set Reference)
- spanSamplingDecision :: !SamplingDecision
}
spanIsSampled :: Span -> Bool
spanIsDebug :: Span -> Bool
data Context = Context {
- contextTraceID :: !TraceID
- contextSpanID :: !SpanID
- contextBaggages :: !(Map Key ByteString)
}
newtype TraceID = TraceID ByteString
decodeTraceID :: Text -> Maybe TraceID
encodeTraceID :: TraceID -> Text
newtype SpanID = SpanID ByteString
decodeSpanID :: Text -> Maybe SpanID
encodeSpanID :: SpanID -> Text
data Reference
- = ChildOf !SpanID
- | FollowsFrom !Context
class Monad m => MonadTrace m where
- trace :: Builder -> m a -> m a
- activeSpan :: m (Maybe Span)
- addSpanEntry :: Key -> Value -> m ()
data Builder = Builder {
- builderName :: !Name
- builderTraceID :: !(Maybe TraceID)
- builderSpanID :: !(Maybe SpanID)
- builderReferences :: !(Set Reference)
- builderTags :: !(Map Key Value)
- builderBaggages :: !(Map Key ByteString)
- builderSamplingPolicy :: !(Maybe SamplingPolicy)
}
type Name = Text
builder :: Name -> Builder
rootSpan :: MonadTrace m => SamplingPolicy -> Name -> m a -> m a
rootSpanWith :: MonadTrace m => (Builder -> Builder) -> SamplingPolicy -> Name -> m a -> m a
childSpan :: MonadTrace m => Name -> m a -> m a
childSpanWith :: MonadTrace m => (Builder -> Builder) -> Name -> m a -> m a
data SamplingDecision
- = Always
- | Never
- | Debug
type SamplingPolicy = IO SamplingDecision
alwaysSampled :: SamplingPolicy
neverSampled :: SamplingPolicy
sampledWithProbability :: Double -> SamplingPolicy
sampledWhen :: Bool -> SamplingPolicy
debugEnabled :: SamplingPolicy
type Key = Text
data Value
tagDoubleValue :: Double -> Value
tagInt64Value :: Integral a => a -> Value
tagTextValue :: Text -> Value
logValue :: ToJSON a => a -> Value
logValueAt :: ToJSON a => POSIXTime -> a -> Value

Types

data Span Source #

A part of a trace.

Constructors

Span
Fields spanName :: !Name spanContext :: !Context spanReferences :: !(Set Reference) spanSamplingDecision :: !SamplingDecision

spanIsSampled :: Span -> Bool Source #

Returns whether the span is sampled.

spanIsDebug :: Span -> Bool Source #

Returns whether the span has debug enabled.

data Context Source #

A fully qualified span identifier, containing both the ID of the trace the span belongs to and the span's ID.

Constructors

Context
Fields contextTraceID :: !TraceID contextSpanID :: !SpanID contextBaggages :: !(Map Key ByteString)

Instances

Instances details

Eq Context Source #
Instance details Defined in Control.Monad.Trace.Internal Methods (==) :: Context -> Context -> Bool # (/=) :: Context -> Context -> Bool #
Ord Context Source #
Instance details Defined in Control.Monad.Trace.Internal Methods compare :: Context -> Context -> Ordering # (<) :: Context -> Context -> Bool # (<=) :: Context -> Context -> Bool # (>) :: Context -> Context -> Bool # (>=) :: Context -> Context -> Bool # max :: Context -> Context -> Context # min :: Context -> Context -> Context #
Show Context Source #
Instance details Defined in Control.Monad.Trace.Internal Methods showsPrec :: Int -> Context -> ShowS # show :: Context -> String # showList :: [Context] -> ShowS #

newtype TraceID Source #

A 128-bit trace identifier.

Constructors

TraceID ByteString

Instances

Instances details

Eq TraceID Source #
Instance details Defined in Control.Monad.Trace.Internal Methods (==) :: TraceID -> TraceID -> Bool # (/=) :: TraceID -> TraceID -> Bool #
Ord TraceID Source #
Instance details Defined in Control.Monad.Trace.Internal Methods compare :: TraceID -> TraceID -> Ordering # (<) :: TraceID -> TraceID -> Bool # (<=) :: TraceID -> TraceID -> Bool # (>) :: TraceID -> TraceID -> Bool # (>=) :: TraceID -> TraceID -> Bool # max :: TraceID -> TraceID -> TraceID # min :: TraceID -> TraceID -> TraceID #
Show TraceID Source #
Instance details Defined in Control.Monad.Trace.Internal Methods showsPrec :: Int -> TraceID -> ShowS # show :: TraceID -> String # showList :: [TraceID] -> ShowS #
ToJSON TraceID Source #
Instance details Defined in Control.Monad.Trace.Internal Methods toJSON :: TraceID -> Value # toEncoding :: TraceID -> Encoding # toJSONList :: [TraceID] -> Value # toEncodingList :: [TraceID] -> Encoding #
FromJSON TraceID Source #
Instance details Defined in Control.Monad.Trace.Internal Methods parseJSON :: Value -> Parser TraceID # parseJSONList :: Value -> Parser [TraceID] #

decodeTraceID :: Text -> Maybe TraceID Source #

Decodes a traced ID from a hex-encoded string.

encodeTraceID :: TraceID -> Text Source #

Hex-encodes a trace ID.

newtype SpanID Source #

A 64-bit span identifier.

Constructors

SpanID ByteString

Instances

Instances details

Eq SpanID Source #
Instance details Defined in Control.Monad.Trace.Internal Methods (==) :: SpanID -> SpanID -> Bool # (/=) :: SpanID -> SpanID -> Bool #
Ord SpanID Source #
Instance details Defined in Control.Monad.Trace.Internal Methods compare :: SpanID -> SpanID -> Ordering # (<) :: SpanID -> SpanID -> Bool # (<=) :: SpanID -> SpanID -> Bool # (>) :: SpanID -> SpanID -> Bool # (>=) :: SpanID -> SpanID -> Bool # max :: SpanID -> SpanID -> SpanID # min :: SpanID -> SpanID -> SpanID #
Show SpanID Source #
Instance details Defined in Control.Monad.Trace.Internal Methods showsPrec :: Int -> SpanID -> ShowS # show :: SpanID -> String # showList :: [SpanID] -> ShowS #
ToJSON SpanID Source #
Instance details Defined in Control.Monad.Trace.Internal Methods toJSON :: SpanID -> Value # toEncoding :: SpanID -> Encoding # toJSONList :: [SpanID] -> Value # toEncodingList :: [SpanID] -> Encoding #
FromJSON SpanID Source #
Instance details Defined in Control.Monad.Trace.Internal Methods parseJSON :: Value -> Parser SpanID # parseJSONList :: Value -> Parser [SpanID] #

decodeSpanID :: Text -> Maybe SpanID Source #

Decodes a span ID from a hex-encoded string.

encodeSpanID :: SpanID -> Text Source #

Hex-encodes a span ID.

data Reference Source #

A relationship between spans.

There are currently two types of references, both of which model direct causal relationships between a child and a parent. More background on references is available in the opentracing specification: https://github.com/opentracing/specification/blob/master/specification.md.

Constructors

ChildOf !SpanID	`ChildOf` references imply that the parent span depends on the child span in some capacity. Note that this reference type is only valid within a single trace.
FollowsFrom !Context	If the parent does not depend on the child, we use a `FollowsFrom` reference.

Instances

Instances details

Eq Reference Source #
Instance details Defined in Control.Monad.Trace.Internal Methods (==) :: Reference -> Reference -> Bool # (/=) :: Reference -> Reference -> Bool #
Ord Reference Source #
Instance details Defined in Control.Monad.Trace.Internal Methods compare :: Reference -> Reference -> Ordering # (<) :: Reference -> Reference -> Bool # (<=) :: Reference -> Reference -> Bool # (>) :: Reference -> Reference -> Bool # (>=) :: Reference -> Reference -> Bool # max :: Reference -> Reference -> Reference # min :: Reference -> Reference -> Reference #
Show Reference Source #
Instance details Defined in Control.Monad.Trace.Internal Methods showsPrec :: Int -> Reference -> ShowS # show :: Reference -> String # showList :: [Reference] -> ShowS #

Generating traces

Individual spans

class Monad m => MonadTrace m where Source #

A monad capable of generating and modifying trace spans.

This package currently provides two instances of this class:

TraceT, which emits spans for each trace in IO and is meant to be used in production.
Identity, where tracing is a no-op and allows testing traced functions without any overhead or complex setup.

Minimal complete definition

trace

Methods

trace :: Builder -> m a -> m a Source #

Trace an action, wrapping it inside a new span. If the action isn't currently being traced, trace should be a no-op. Otherwise, the new span should share the active span's trace ID, sampling decision, and baggages unless overridden by the input Builder.

activeSpan :: m (Maybe Span) Source #

Extracts the currently active span, or Nothing if the action is not being traced.

default activeSpan :: (MonadTrace n, MonadTrans t, m ~ t n) => m (Maybe Span) Source #

addSpanEntry :: Key -> Value -> m () Source #

Adds information to the active span, if present.

default addSpanEntry :: (MonadTrace n, MonadTrans t, m ~ t n) => Key -> Value -> m () Source #

Instances

Instances details

MonadTrace Identity Source #
Instance details Defined in Control.Monad.Trace.Class Methods trace :: Builder -> Identity a -> Identity a Source # activeSpan :: Identity (Maybe Span) Source # addSpanEntry :: Key -> Value -> Identity () Source #
(MonadIO m, MonadBaseControl IO m) => MonadTrace (TraceT m) Source #
Instance details Defined in Control.Monad.Trace Methods trace :: Builder -> TraceT m a -> TraceT m a Source # activeSpan :: TraceT m (Maybe Span) Source # addSpanEntry :: Key -> Value -> TraceT m () Source #
MonadTrace m => MonadTrace (ExceptT e m) Source #
Instance details Defined in Control.Monad.Trace.Class Methods trace :: Builder -> ExceptT e m a -> ExceptT e m a Source # activeSpan :: ExceptT e m (Maybe Span) Source # addSpanEntry :: Key -> Value -> ExceptT e m () Source #
(MonadTrace m, Monoid w) => MonadTrace (WriterT w m) Source #
Instance details Defined in Control.Monad.Trace.Class Methods trace :: Builder -> WriterT w m a -> WriterT w m a Source # activeSpan :: WriterT w m (Maybe Span) Source # addSpanEntry :: Key -> Value -> WriterT w m () Source #
MonadTrace m => MonadTrace (StateT s m) Source #
Instance details Defined in Control.Monad.Trace.Class Methods trace :: Builder -> StateT s m a -> StateT s m a Source # activeSpan :: StateT s m (Maybe Span) Source # addSpanEntry :: Key -> Value -> StateT s m () Source #
MonadTrace m => MonadTrace (ReaderT r m) Source #
Instance details Defined in Control.Monad.Trace.Class Methods trace :: Builder -> ReaderT r m a -> ReaderT r m a Source # activeSpan :: ReaderT r m (Maybe Span) Source # addSpanEntry :: Key -> Value -> ReaderT r m () Source #
MonadTrace m => MonadTrace (StateT s m) Source #
Instance details Defined in Control.Monad.Trace.Class Methods trace :: Builder -> StateT s m a -> StateT s m a Source # activeSpan :: StateT s m (Maybe Span) Source # addSpanEntry :: Key -> Value -> StateT s m () Source #
(MonadTrace m, Monoid w) => MonadTrace (WriterT w m) Source #
Instance details Defined in Control.Monad.Trace.Class Methods trace :: Builder -> WriterT w m a -> WriterT w m a Source # activeSpan :: WriterT w m (Maybe Span) Source # addSpanEntry :: Key -> Value -> WriterT w m () Source #
(MonadTrace m, Monoid w) => MonadTrace (RWST r w s m) Source #
Instance details Defined in Control.Monad.Trace.Class Methods trace :: Builder -> RWST r w s m a -> RWST r w s m a Source # activeSpan :: RWST r w s m (Maybe Span) Source # addSpanEntry :: Key -> Value -> RWST r w s m () Source #
(MonadTrace m, Monoid w) => MonadTrace (RWST r w s m) Source #
Instance details Defined in Control.Monad.Trace.Class Methods trace :: Builder -> RWST r w s m a -> RWST r w s m a Source # activeSpan :: RWST r w s m (Maybe Span) Source # addSpanEntry :: Key -> Value -> RWST r w s m () Source #

data Builder Source #

A span builder.

Builder has an IsString instance, producing a span with the given string as name, no additional references, tags, or baggages. This allows convenient creation of spans via the OverloadedStrings pragma.

Constructors

Builder

Fields

builderName :: !Name
Name of the generated span.
builderTraceID :: !(Maybe TraceID)
The trace ID of the generated span. If unset, the active span's trace ID will be used if present, otherwise a new ID will be generated.
builderSpanID :: !(Maybe SpanID)
The ID of the generated span, otherwise the ID will be auto-generated.
builderReferences :: !(Set Reference)
Span references.
builderTags :: !(Map Key Value)
Initial set of tags.
builderBaggages :: !(Map Key ByteString)
Span context baggages.
builderSamplingPolicy :: !(Maybe SamplingPolicy)
How the span should be sampled. If unset, the active's span sampling will be used if present, otherwise the span will not be sampled.

Instances

Instances details

IsString Builder Source #
Instance details Defined in Control.Monad.Trace.Class Methods fromString :: String -> Builder #

type Name = Text Source #

The name of a span.

builder :: Name -> Builder Source #

Returns a Builder with the given input as name and all other fields empty.

Structured traces

rootSpan :: MonadTrace m => SamplingPolicy -> Name -> m a -> m a Source #

Starts a new trace. For performance reasons, it is possible to customize how frequently tracing information is collected. This allows fine-grain control on the overhead induced by tracing. For example, you might only want to sample 1% of a very actively used call-path with sampledWithProbability 0.01.

rootSpanWith :: MonadTrace m => (Builder -> Builder) -> SamplingPolicy -> Name -> m a -> m a Source #

Starts a new trace, customizing the span builder. Note that the sampling input will override any sampling customization set on the builder.

childSpan :: MonadTrace m => Name -> m a -> m a Source #

Extends a trace: the active span's ID will be added as a reference to a newly created span and both spans will share the same trace ID. If no span is active, childSpan is a no-op.

childSpanWith :: MonadTrace m => (Builder -> Builder) -> Name -> m a -> m a Source #

Extends a trace, same as childSpan but also customizing the builder.

Sampling

data SamplingDecision Source #

A span's sampling decision.

Constructors

Always
Never
Debug

Instances

Instances details

Enum SamplingDecision Source #
Instance details Defined in Control.Monad.Trace.Internal Methods succ :: SamplingDecision -> SamplingDecision # pred :: SamplingDecision -> SamplingDecision # toEnum :: Int -> SamplingDecision # fromEnum :: SamplingDecision -> Int # enumFrom :: SamplingDecision -> [SamplingDecision] # enumFromThen :: SamplingDecision -> SamplingDecision -> [SamplingDecision] # enumFromTo :: SamplingDecision -> SamplingDecision -> [SamplingDecision] # enumFromThenTo :: SamplingDecision -> SamplingDecision -> SamplingDecision -> [SamplingDecision] #
Eq SamplingDecision Source #
Instance details Defined in Control.Monad.Trace.Internal Methods (==) :: SamplingDecision -> SamplingDecision -> Bool # (/=) :: SamplingDecision -> SamplingDecision -> Bool #
Ord SamplingDecision Source #
Instance details Defined in Control.Monad.Trace.Internal Methods compare :: SamplingDecision -> SamplingDecision -> Ordering # (<) :: SamplingDecision -> SamplingDecision -> Bool # (<=) :: SamplingDecision -> SamplingDecision -> Bool # (>) :: SamplingDecision -> SamplingDecision -> Bool # (>=) :: SamplingDecision -> SamplingDecision -> Bool # max :: SamplingDecision -> SamplingDecision -> SamplingDecision # min :: SamplingDecision -> SamplingDecision -> SamplingDecision #
Show SamplingDecision Source #
Instance details Defined in Control.Monad.Trace.Internal Methods showsPrec :: Int -> SamplingDecision -> ShowS # show :: SamplingDecision -> String # showList :: [SamplingDecision] -> ShowS #

type SamplingPolicy = IO SamplingDecision Source #

An action to determine how a span should be sampled.

alwaysSampled :: SamplingPolicy Source #

Returns a SamplingPolicy which always samples.

neverSampled :: SamplingPolicy Source #

Returns a SamplingPolicy which never samples.

sampledWithProbability :: Double -> SamplingPolicy Source #

Returns a SamplingPolicy which randomly samples spans.

sampledWhen :: Bool -> SamplingPolicy Source #

Returns a SamplingPolicy which samples a span iff the input is True. It is equivalent to:

sampledWhen b = if b then alwaysSampled else neverSampled

debugEnabled :: SamplingPolicy Source #

Returns a debug SamplingPolicy. Debug spans are always sampled.

Annotating traces

Note that not all annotation types are supported by all backends. For example Zipkin only supports string tags (refer to Monitor.Tracing.Zipkin for the full list of supported span metadata).

type Key = Text Source #

The type of annotations' keys.

Keys starting with double underscores are reserved and should not be used.

data Value Source #

Metadata attached to a span.

tagDoubleValue :: Double -> Value Source #

Generates a tag value from a double.

tagInt64Value :: Integral a => a -> Value Source #

Generates a 64-bit integer tag value from any integer.

tagTextValue :: Text -> Value Source #

Generates a Unicode text tag value.

logValue :: ToJSON a => a -> Value Source #

Generates a log value with the time of writing as timestamp. Note that the value may be written later than it is created. For more control on the timestamp, use logValueAt.

logValueAt :: ToJSON a => POSIXTime -> a -> Value Source #

Generates a log value with a custom time.