update otel tracing doc for serving

Author: dprotaso

config/nav.yml

@@ -183,7 +183,7 @@ nav:
         - Security-Guard example alerts: serving/app-security/security-guard-example-alerts.md
       # Serving - observability
       - Observability:
-        - Request traces: serving/accessing-traces.md
+        - Request traces: serving/observability/accessing-traces.md
         - Collecting logs: serving/observability/logging/collecting-logs.md
         - Configuring logging: serving/observability/logging/config-logging.md
         - Configuring Request logging: serving/observability/logging/request-logging.md

docs/serving/accessing-traces.md

@@ -0,0 +1,46 @@
+---
+audience: administrator
+components:
+  - serving
+function: how-to
+---
+
+# Accessing request traces
+
+Traces give us the big picture of what happens when a request is made to an application. 
+Knative Serving is instrumented with [OpenTelemetry](https://opentelemetry.io/docs/what-is-opentelemetry/) which can emit traces to a multitude of different backends.
+Specifically Serving can be configured to emit traces using the standard [OTLP format](https://opentelemetry.io/docs/specs/otlp/).
+
+## Configuring Traces
+
+You can update the configuration file for tracing in [observability.yaml](https://github.com/knative/serving/blob/main/config/core/configmaps/observability.yaml).
+
+Follow the instructions in the file to set your configuration options. This file includes options such as sample rate (to determine what percentage of requests to trace), export protocol and desired backend.
+
+You can quickly explore and update the ConfigMap object with the following command:
+```bash
+kubectl -n knative-serving edit configmap config-observability
+```
+
+## Jaeger
+
+In order to access request traces, you use the Jaeger visualization tool.
+
+1.  To open the Jaeger UI, enter the following command:
+
+    ```bash
+    kubectl proxy
+    ```
+
+    This command starts a local proxy of Jaeger on port 8001. For security
+    reasons, the Jaeger UI is exposed only within the cluster.
+
+1.  Access the Jaeger UI at the following URL:
+
+    ```
+    http://localhost:8001/api/v1/namespaces/<namespace>/services/jaeger-query:16686/proxy/search/
+    ```
+    Where `<namespace>` is the namespace where Jaeger is deployed, for example, `knative-serving`.
+
+1.  Select the service of interest and click "Find Traces" to see the latest
+    traces. Click on a trace to see a detailed view of a specific call.