docs(fastapi): add section on environment variables, trace propagation, websockets, logging, and package links

Author: jyotirmayc

instrumentation/opentelemetry-instrumentation-fastapi/README.rst

@@ -20,7 +20,37 @@ Installation
     pip install opentelemetry-instrumentation-fastapi
 
 References
-----------
 
 * `OpenTelemetry Project <https://opentelemetry.io/>`_
 * `OpenTelemetry Python Examples <https://github.com/open-telemetry/opentelemetry-python/tree/main/docs/examples>`_
+ 
+ Configuration & Usage Notes
+ --------------------------
+ 
+ **Environment Variables**
+ 
+ OpenTelemetry Python supports standard environment variables for configuration, including:
+ 
+ - ``OTEL_EXPORTER_OTLP_ENDPOINT``
+ - ``OTEL_EXPORTER_OTLP_PROTOCOL``
+ - ``OTEL_SERVICE_NAME``
+ - ``OTEL_TRACES_EXPORTER``, ``OTEL_METRICS_EXPORTER``
+ 
+ These can be set to configure exporters, service name, and other options. See the `OpenTelemetry Python documentation <https://opentelemetry-python.readthedocs.io/en/latest/getting-started.html#environment-variables>`_ for a full list.
+ 
+ **Trace Propagation**
+ 
+ Trace context propagation works automatically for HTTP requests. The instrumentation uses W3C Trace Context and Baggage headers for distributed tracing. No manual intervention is required for standard HTTP requests.
+ 
+ **WebSocket Support**
+ 
+ Automatic trace propagation for WebSocket connections is limited. You may need to manually create and propagate spans for WebSocket handlers in FastAPI applications.
+ 
+ **Logging Integration**
+ 
+ To integrate logs as events in traces, use the ``opentelemetry-instrumentation-logging`` package and configure your logger with OpenTelemetry's logging handler. This allows logs to be attached to traces as events. See the `OpenTelemetry Python logging documentation <https://opentelemetry-python.readthedocs.io/en/latest/instrumentation/logging/logging.html>`_.
+ 
+ **Related Packages**
+ 
+ - `opentelemetry-instrumentation <https://pypi.org/project/opentelemetry-instrumentation/>`_
+ - `opentelemetry-instrumentation-fastapi <https://pypi.org/project/opentelemetry-instrumentation-fastapi/>`_