refactor(tracer) use Context instead of SpanContext

To maintain OpenTelemetry API compliance, this commit changes the
InstanaTracer to use OTel's `Context` instead of the Instana's
`SpanContext` as `context` parameter for `start_as_current_span()` and
`start_span()`. methods.

This commit fixes #847.

Signed-off-by: Paulo Vital <paulo.vital@ibm.com>
Co-authored-by: Varsha GS <varsha.gs@ibm.com>

Author: pvital

src/instana/span/span.py

@@ -241,7 +241,7 @@ def assure_errored(self) -> None:
 INVALID_SPAN = NonRecordingSpan(INVALID_SPAN_CONTEXT)
 
 
-def get_current_span(context: Optional[Context] = None) -> InstanaSpan:
+def get_current_span(context: Optional[Context] = None) -> Union[InstanaSpan, Span]:
     """Retrieve the current span.
 
     Args:
@@ -252,6 +252,6 @@ def get_current_span(context: Optional[Context] = None) -> InstanaSpan:
         The Span set in the context if it exists. INVALID_SPAN otherwise.
     """
     span = get_value(_SPAN_KEY, context=context)
-    if span is None or not isinstance(span, InstanaSpan):
+    if span is None or not isinstance(span, (InstanaSpan, Span)):
         return INVALID_SPAN
     return span

src/instana/tracer.py

@@ -3,7 +3,6 @@
 
 
 import time
-from contextlib import contextmanager
 from typing import TYPE_CHECKING, Iterator, Mapping, Optional, Type, Union
 
 from opentelemetry.context.context import Context
@@ -16,6 +15,7 @@
     use_span,
 )
 from opentelemetry.util import types
+from opentelemetry.util._decorator import _agnosticcontextmanager
 
 from instana.agent.host import HostAgent
 from instana.log import logger
@@ -32,6 +32,8 @@
 from instana.util.ids import generate_id
 
 if TYPE_CHECKING:
+    from opentelemetry.trace import Span
+
     from instana.agent.base import BaseAgent
     from instana.propagators.base_propagator import BasePropagator, CarrierT
 
@@ -108,17 +110,15 @@ def exporter(self) -> Optional[Type["BaseAgent"]]:
     def start_span(
         self,
         name: str,
-        span_context: Optional[SpanContext] = None,
+        context: Optional[Context] = None,
         kind: SpanKind = SpanKind.INTERNAL,
         attributes: types.Attributes = None,
         links: _Links = None,
         start_time: Optional[int] = None,
         record_exception: bool = True,
         set_status_on_exception: bool = True,
     ) -> InstanaSpan:
-        parent_context = (
-            span_context if span_context else get_current_span().get_span_context()
-        )
+        parent_context = get_current_span(context).get_span_context()
 
         if parent_context and not isinstance(parent_context, SpanContext):
             raise TypeError("parent_context must be an Instana SpanContext or None.")
@@ -136,22 +136,22 @@ def start_span(
 
         return span
 
-    @contextmanager
+    @_agnosticcontextmanager
     def start_as_current_span(
         self,
         name: str,
-        span_context: Optional[SpanContext] = None,
+        context: Optional[Context] = None,
         kind: SpanKind = SpanKind.INTERNAL,
         attributes: types.Attributes = None,
         links: _Links = None,
         start_time: Optional[int] = None,
         record_exception: bool = True,
         set_status_on_exception: bool = True,
         end_on_exit: bool = True,
-    ) -> Iterator[InstanaSpan]:
+    ) -> Iterator["Span"]:
         span = self.start_span(
             name=name,
-            span_context=span_context,
+            context=context,
             kind=kind,
             attributes=attributes,
             links=links,
@@ -167,7 +167,9 @@ def start_as_current_span(
         ) as span:
             yield span
 
-    def _create_span_context(self, parent_context: SpanContext) -> SpanContext:
+    def _create_span_context(
+        self, parent_context: Optional[SpanContext] = None
+    ) -> SpanContext:
         """Creates a new SpanContext based on the given parent context."""
 
         if parent_context and parent_context.is_valid: