Propagation (Brave 5.8.0 API)

Type Parameters:

K - Usually, but not always a String

All Known Implementing Classes:

B3Propagation, B3SinglePropagation, 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<java.lang.String> B3_SINGLE_STRING

static Propagation<java.lang.String> B3_STRING

Method Summary

All Methods Instance Methods Abstract Methods
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.
`java.util.List<K>`	`keys()`	The propagation fields defined.

- Field Detail
  - B3_STRING
```
static final Propagation<java.lang.String> B3_STRING
```
  - B3_SINGLE_STRING
```
static final Propagation<java.lang.String> B3_SINGLE_STRING
```
- Method Detail
  - keys
```
java.util.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.
    Note: If your implementation carries "extra fields", such as correlation IDs, do not return the names of those fields here. If you do, they will be deleted, which can interfere with user headers.
  - 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.