Package io.opentelemetry.api.incubator.propagation

Class PassThroughPropagator

java.lang.Object
io.opentelemetry.api.incubator.propagation.PassThroughPropagator
All Implemented Interfaces:
TextMapPropagator
public final class PassThroughPropagator extends Object implements TextMapPropagator
A TextMapPropagator which can be configured with a set of fields, which will be extracted and stored in Context. If the Context is used again to inject, the values will be injected as-is. This TextMapPropagator is appropriate for a service that does not need to participate in telemetry in any way and provides the most efficient way of propagating incoming context to outgoing requests. In almost all cases, you will configure this single TextMapPropagator when using OpenTelemetry.propagating(ContextPropagators) to create an OpenTelemetry that only propagates. Similarly, you will never need this when using the OpenTelemetry SDK to enable telemetry.

  • Field Details

  • Constructor Details

    • PassThroughPropagator

      private PassThroughPropagator(List<String> fields)

  • Method Details

    • create

      public static TextMapPropagator create(String... fields)
      Returns a TextMapPropagator which will propagate the given fields from extraction to injection.

    • create

      public static TextMapPropagator create(Iterable<String> fields)
      Returns a TextMapPropagator which will propagate the given fields from extraction to injection.

    • 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