Package brave.propagation

Interface Propagation<K>

Type Parameters:

K - Usually, but not always a String

All Known Implementing Classes:

B3Propagation, ExtraFieldPropagation

public interface Propagation<K>

Injects and extracts trace identifiers as text into carriers that travel in-band across process boundaries. Identifiers are often encoded as messaging or RPC request headers.

Propagation example: Http

When using http, the carrier of propagated data on both the client (injector) and server (extractor) side is usually an http request. Propagation is usually implemented via library- specific request interceptors, where the client-side injects span identifiers and the server-side extracts them.

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static class	Propagation.Factory
static interface	Propagation.Getter<C,K>	Gets the first value of the given propagation key or returns null
static interface	Propagation.KeyFactory<K>	Creates keys for use in propagated contexts
static interface	Propagation.Setter<C,K>	Replaces a propagated key with the given value

Field Summary

Fields

Modifier and Type	Field	Description
static Propagation<String>	B3_STRING

Method Summary

Modifier and Type	Method	Description
<C> TraceContext.Extractor<C>	extractor(Propagation.Getter<C,K> getter)
<C> TraceContext.Injector<C>	injector(Propagation.Setter<C,K> setter)	Replaces a propagated field with the given value.
List<K>	keys()	The propagation fields defined.

Field Detail

B3_STRING

static final Propagation<String> B3_STRING

Method Detail

keys

List<K> keys()

The propagation fields defined. If your carrier is reused, you should delete the fields here before calling Propagation.Setter.put(Object, Object, String).

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.

injector

<C> TraceContext.Injector<C> injector(Propagation.Setter<C,K> setter)

Replaces a propagated field with the given value. Saved as a constant to avoid runtime allocations. For example, a setter for an HttpURLConnection would be the method reference URLConnection.addRequestProperty(String, String)

Parameters:

setter - invoked for each propagation key to add.

extractor

<C> TraceContext.Extractor<C> extractor(Propagation.Getter<C,K> getter)

Parameters:

getter - invoked for each propagation key to get.