Moving active span interaction To Trace Context Utilities

CHANGELOG.md

@@ -56,6 +56,8 @@ Updates:
   ([#911](https://github.com/open-telemetry/opentelemetry-specification/pull/911))
 - Explicitly specify the SpanContext APIs IsValid and IsRemote as required
   ([#914](https://github.com/open-telemetry/opentelemetry-specification/pull/914))
+- Move active span interaction in the Trace API to a separate class
+  ([#923](https://github.com/open-telemetry/opentelemetry-specification/pull/923))
 
 ## v0.6.0 (07-01-2020)
 

spec-compliance-matrix.md

@@ -15,6 +15,9 @@ status of the feature is not known.
 |Create TracerProvider                         | + | +  | + | +    | +  | +    | + | +  | + | +  |
 |Get a Tracer                                  | + | +  | + | +    | +  | +    | + | +  | + | +  |
 |Safe for concurrent calls                     | + | +  | + |      | +  | +    | + | +  | + | +  |
+|[Tracing Context Utilities](https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/trace/api.md#tracing-context-utilities)|
+|Get active Span                               |   |    |   | +    |    |      |   |    |   |    |
+|Set active Span                               |   |    |   | +    |    |      |   |    |   |    |
 |[Tracer](https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/trace/api.md#tracer-operations)|
 |Create a new Span                             | + | +  | + | +    | +  | +    | + | +  | + | +  |
 |Get active Span                               | + | +  | + | +    | +  | +    | + | +  | + | +  |

specification/trace/api.md

@@ -11,6 +11,7 @@ Table of Contents
     * [Duration](#duration)
 * [TracerProvider](#tracerprovider)
   * [TracerProvider operations](#tracerprovider-operations)
+* [Tracing Context Utilities](#tracing-context-utilities)
 * [Tracer](#tracer)
   * [Tracer operations](#tracer-operations)
 * [SpanContext](#spancontext)
@@ -129,6 +130,22 @@ the tracer could, for example, do a look-up with its name+version in a map in
 the `TracerProvider`, or the `TracerProvider` could maintain a registry of all
 returned `Tracer`s and actively update their configuration if it changes.
 
+## Tracing Context Utilities
+
+`Tracing Context Utilities` contains all operations within tracing that
+modify the [`Context`](../context/context.md).
+
+As these utilities operate solely on the context API, they MAY be exposed
+as static methods on the trace module instead of a class.
+
+The `Tracing Context Utilities` MUST provide the following functions:
+
+- Get the currently active span
+- Set the currently active span
+
+The above methods MUST be equivalent to a single parameterized method call of
+the [`Context`](../context/context.md) management system.
+
 ## Tracer
 
 The tracer is responsible for creating `Span`s.
@@ -142,17 +159,12 @@ The `Tracer` MUST provide functions to:
 
 - [Create a new `Span`](#span-creation) (see the section on `Span`)
 
-The `Tracer` SHOULD provide methods to:
+The `Tracer` MAY provide functions to:
 
-- Get the currently active `Span`
-- Mark a given `Span` as active
+- Get the currently active span
+- Set the currently active span
 
-The `Tracer` MUST delegate to the [`Context`](../context/context.md) to perform
-these tasks, i.e. the above methods MUST do the same as a single equivalent
-method of the Context management system.
-In particular, this implies that the active span MUST not depend on the `Tracer`
-that it is queried from/was set to, as long as the tracers were obtained from
-the same `TracerProvider`.
+These functions MUST delegate to the `Tracing Context Utilities`.
 
 ## SpanContext