Class W3CTraceContextPropagator

java.lang.Object

io.opentelemetry.api.trace.propagation.W3CTraceContextPropagator

All Implemented Interfaces:

TextMapPropagator

@Immutable
public final class W3CTraceContextPropagator
extends Object
implements TextMapPropagator

Implementation of the W3C TraceContext propagation protocol. See W3C Trace Context.

This is the default propagator for SpanContexts. The SpanContext type is designed to support all the data propagated via W3C propagation natively.

Method Summary

Modifier and Type	Method	Description
<C> Context	extract(Context context, C carrier, TextMapGetter<C> getter)	Extracts data from upstream.
Collection<String>	fields()	The propagation fields defined.
static W3CTraceContextPropagator	getInstance()	Returns a singleton instance of a TextMapPropagator implementing the W3C TraceContext propagation.
<C> void	inject(Context context, C carrier, TextMapSetter<C> setter)	Injects data for downstream consumers, for example as HTTP headers.
String	toString()

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Details

getInstance

public static W3CTraceContextPropagator getInstance()

Returns a singleton instance of a TextMapPropagator implementing the W3C TraceContext propagation.

fields

public Collection<String> fields()

Description copied from interface: TextMapPropagator

The propagation fields defined. If your carrier is reused, you should delete the fields here before calling TextMapPropagator.inject(Context, Object, TextMapSetter) )}.

For example, if the carrier is a single-use or immutable request object, you don't need to clear fields as they couldn't have been set before. If it is a mutable, retryable object, successive calls should clear these fields first.

Some use cases for this are:

• Allow pre-allocation of fields, especially in systems like gRPC Metadata
• Allow a single-pass over an iterator

Specified by:

fields in interface TextMapPropagator

Returns:

the fields that will be used by this formatter.

inject

public <C> void inject(Context context,
 @Nullable
 C carrier,
 TextMapSetter<C> setter)

Description copied from interface: TextMapPropagator

Injects data for downstream consumers, for example as HTTP headers. The carrier may be null to facilitate calling this method with a lambda for the TextMapSetter, in which case that null will be passed to the TextMapSetter implementation.

Specified by:

inject in interface TextMapPropagator

Type Parameters:

C - carrier of propagation fields, such as an http request

Parameters:

context - the Context containing the value to be injected.

carrier - holds propagation fields. For example, an outgoing message or http request.

setter - invoked for each propagation key to add or remove.

extract

public <C> Context extract(Context context,
 @Nullable
 C carrier,
 TextMapGetter<C> getter)

Description copied from interface: TextMapPropagator

Extracts data from upstream. For example, from incoming http headers. The returned Context should contain the extracted data, if any, merged with the data from the passed-in Context.

If the incoming information could not be parsed, implementations MUST return the original Context, unaltered.

Specified by:

extract in interface TextMapPropagator

Type Parameters:

C - the type of carrier of the propagation fields, such as an http request.

Parameters:

context - the Context used to store the extracted value.

carrier - holds propagation fields. For example, an outgoing message or http request.

getter - invoked for each propagation key to get data from the carrier.

Returns:

the Context containing the extracted data.

toString

public String toString()

Overrides:

toString in class Object