Package io.opentelemetry.api.incubator.propagation

Class PassThroughPropagator

  • All Implemented Interfaces:
    TextMapPropagator
    public final class PassThroughPropagator
extends java.lang.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 Detail

      • EXTRACTED_KEY_VALUES

        private static final ContextKey<java.util.List<java.lang.String>> EXTRACTED_KEY_VALUES

      • fields

        private final java.util.List<java.lang.String> fields

    • Constructor Detail

      • PassThroughPropagator

        private PassThroughPropagator​(java.util.List<java.lang.String> fields)

    • Method Detail

      • create

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

      • create

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

      • fields

        public java.util.Collection<java.lang.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 java.lang.String toString()
        Overrides:
        toString in class java.lang.Object