[Bug]: start_as_current_span() missing OpenTelemetry 'context' parameter

[1mike1451]

Problem Description

InstanaTracer.start_as_current_span() and start_span() use a non-standard span_context parameter instead of the OpenTelemetry-required context parameter, causing TypeError when called by OpenTelemetry-compliant libraries.

This regression was introduced in commit c4d4251, which changed from context to span_context for architectural simplification. Discovered with FastMCP but affects any OpenTelemetry-compliant library.

Current Implementation (tracer.py:140-151):

def start_as_current_span(
    self,
    name: str,
    span_context: Optional[SpanContext] = None,  # Non-standard parameter
    ...
)

Expected per OpenTelemetry Spec:

def start_as_current_span(
    self,
    name: str,
    context: Optional[Context] = None,  # Required by OpenTelemetry spec
    ...
)

Root Cause:

Instana's SpanContext has 10 custom fields beyond OpenTelemetry's base. The _create_span_context() method needs direct access to these fields.

Proposed Solution:

def start_as_current_span(
    self,
    name: str,
    context: Optional[Context] = None,  # Add for OpenTelemetry compliance
    span_context: Optional[SpanContext] = None,  # Keep for backward compatibility
    kind: SpanKind = SpanKind.INTERNAL,
    ...
) -> Iterator[InstanaSpan]:
    if context is not None and span_context is None:
        span_context = get_current_span(context).get_span_context()
    
    span = self.start_span(name=name, span_context=span_context, ...)

Benefits: Restores OpenTelemetry compliance, preserves Instana's custom fields, follows kind parameter pattern, maintains backward compatibility.

Minimal, Complete, Verifiable, Example

from instana.tracer import InstanaTracer

tracer = InstanaTracer()
with tracer.start_as_current_span("test-span", context=None):
    pass

# Error: TypeError: InstanaTracer.start_as_current_span() got an unexpected keyword argument 'context'

Python Version

3.9

Python Modules

instana (main branch)
opentelemetry-api>=1.27.0
fastmcp>=0.1.0 (where issue was discovered)

Python Environment

No special environment variables required. Issue occurs in any environment where OpenTelemetry-compliant code uses the Instana tracer with the standard `context` parameter.

[1mike1451]

By the way, I would like to fix this because FastMCP 3 sets telemetry data by default, and it uses the context parameter. You can see the source code for that project here: https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/telemetry.py#L71

[CagriYonca]

Hey @1mike1451 , thanks for reaching out! Currently, we don't support multiple OpenTelemetry instrumentation packages running simultaneously but we have plans for the future.

Regarding the context parameter, OpenTelemetry's context is different from ours. We have a custom version that offers zero-touch instrumentation with easier usability, so switching to OpenTelemetry's context will likely cause other issues later.

So it seems like the best course of action is to avoid using OpenTelemetry and Instana together until we have a fix for that.