Merge pull request #280848 from jeremydvoss/sampler

Add sampler back to python attach

Author: prmerger-automator[bot]

articles/azure-monitor/app/azure-web-apps-python.md

@@ -83,6 +83,7 @@ You can configure with [OpenTelemetry environment variables][ot_env_vars] such a
 | `OTEL_TRACES_EXPORTER` | If set to `None`, disables collection and export of distributed tracing telemetry. |
 | `OTEL_BLRP_SCHEDULE_DELAY` | Specifies the logging export interval in milliseconds. Defaults to 5000. |
 | `OTEL_BSP_SCHEDULE_DELAY` | Specifies the distributed tracing export interval in milliseconds. Defaults to 5000. |
+| `OTEL_TRACES_SAMPLER_ARG` | Specifies the ratio of distributed tracing telemetry to be [sampled][application_insights_sampling]. Accepted values range from 0 to 1. The default is 1.0, meaning no telemetry is sampled out. |
 | `OTEL_PYTHON_DISABLED_INSTRUMENTATIONS` | Specifies which OpenTelemetry instrumentations to disable. When disabled, instrumentations aren't executed as part of autoinstrumentation. Accepts a comma-separated list of lowercase [library names](#application-monitoring-for-azure-app-service-and-python-preview). For example, set it to `"psycopg2,fastapi"` to disable the Psycopg2 and FastAPI instrumentations. It defaults to an empty list, enabling all supported instrumentations. |
 
 ### Add a community instrumentation library