OpenTelemetry.Context

The ability to correlate events across service boundaries is one of the principle concepts behind distributed tracing. To find these correlations, components in a distributed system need to be able to collect, store, and transfer metadata referred to as context.

A context will often have information identifying the current span and trace, and can contain arbitrary correlations as key-value pairs.

Propagation is the means by which context is bundled and transferred in and across services, often via HTTP headers.

Together, context and propagation represent the engine behind distributed tracing.

Documentation

data Key a

Keys are used to allow cross-cutting concerns to control access to their local state. They are unique such that other libraries which may use the same context cannot accidentally use the same key. It is recommended that concerns mediate data access via an API, rather than provide direct public access to their keys.

newKey :: MonadIO m => Text -> m (Key a)

data Context

A Context is a propagation mechanism which carries execution-scoped values across API boundaries and between logically associated execution units. Cross-cutting concerns access their data in-process using the same shared Context object

Instances

Monoid Context

Defined in OpenTelemetry.Context.Types

Methods

mempty :: Context

mappend :: Context -> Context -> Context

mconcat :: [Context] -> Context

Semigroup Context

Defined in OpenTelemetry.Context.Types

Methods

(<>) :: Context -> Context -> Context

sconcat :: NonEmpty Context -> Context

stimes :: Integral b => b -> Context -> Context

class HasContext s where

Methods

contextL :: Lens' s Context

empty :: Context

lookup :: Key a -> Context -> Maybe a

insert :: Key a -> a -> Context -> Context

adjust :: (a -> a) -> Key a -> Context -> Context

delete :: Key a -> Context -> Context

union :: Context -> Context -> Context

insertSpan :: Span -> Context -> Context

lookupSpan :: Context -> Maybe Span

removeSpan :: Context -> Context

insertBaggage :: Baggage -> Context -> Context

lookupBaggage :: Context -> Maybe Baggage

removeBaggage :: Context -> Context