Add page for SDK configurations view (#34605)

* Add page for SDK configurations view

* Add to side navigation

* Fix link

* Add additional reason for missing data

* Fix inverted conditions in Missing configuration data section

Two bullets listed conditions where data IS available rather than
conditions where data is MISSING:
- "has not been disabled" → "has been disabled"
- "is accessible" → "is not accessible"

* Fix vale style violations in sdk_configurations.md

- Replace "via" with "through" (2 occurrences)
- Replace temporal "will not be" with "is not"
- Add missing trailing newline

* Remove orphaned reference in troubleshooting _index.md

Remove unused ref [33] pointing to old /configuration_visibility/ path.
Renumber the SDK configurations ref from [34] to [33].

* Move SDK Configurations after existing troubleshooting pages

Place the SDK Configurations entry after Tracer Startup Logs, Tracer
Debug Logs, and Connection Errors in both the nav menu and the
_index.md collapse sections, since those are more commonly used
troubleshooting tools. Restore original nav weights for existing pages.

* Improve Access section and normalize list style in sdk_configurations.md

- Rename "Where to find it" to "Access SDK configurations"
- Add intro sentence and explicit step to navigate to APM > Services
- Move step 3 description out of the numbered list
- Normalize bullet markers from asterisks to hyphens

---------

Co-authored-by: Duncan Hewett <8017759+duncanhewett@users.noreply.github.com>
Co-authored-by: Brett Blue <brett.blue@datadoghq.com>

Author: duncanhewett

config/_default/menus/main.en.yaml

@@ -4470,6 +4470,11 @@ menu:
       identifier: tracing_troubleshooting_connection_errors
       parent: tracing_troubleshooting
       weight: 1603
+    - name: SDK Configurations
+      url: tracing/troubleshooting/sdk_configurations
+      identifier: tracing_troubleshooting_sdk_configurations
+      parent: tracing_troubleshooting
+      weight: 1604
     - name: Agent Rate Limits
       url: tracing/troubleshooting/agent_rate_limits
       identifier: tracing_troubleshooting_rate_limits

content/en/tracing/troubleshooting/_index.md

@@ -316,6 +316,12 @@ During startup, Datadog tracing libraries emit logs that reflect the configurati
 
 {{% /collapse-content %}}
 
+{{% collapse-content title="SDK configurations" level="h4" %}}
+
+Configuration values are automatically reported by the SDKs and can be viewed in the UI. This can be used to troubleshoot instrumentation issues caused by misconfiguration. For details, see the [SDK configurations page][33].
+
+{{% /collapse-content %}}
+
 ## Additional support
 
 If you still need additional support, open a ticket with Datadog Support.
@@ -379,4 +385,4 @@ When you open a [support ticket][1], the Datadog support team may ask for the fo
 [30]: /tracing/services/inferred_services
 [31]: /tracing/trace_pipeline/metrics/#apm-traces-estimated-usage-dashboard
 [32]: https://app.datadoghq.com/services
-
+[33]: /tracing/troubleshooting/sdk_configurations/

content/en/tracing/troubleshooting/sdk_configurations.md

@@ -0,0 +1,51 @@
+---
+title: SDK Configurations
+description: Use the SDK configurations view to validate setup, and troubleshoot instrumentation issues.
+---
+
+## Overview
+
+The SDK Configurations view shows the active configurations of SDKs per service. Configurations are automatically reported from the SDKs. Use the view to:
+
+- Troubleshoot instrumentation issues, including where configurations are inconsistent across instances of a service.
+- Validate that a configuration change was deployed correctly across intended instances.
+- Identify the source of a configuration value to help fix misconfigurations.
+- Discover available configuration options and how they are set.
+
+## Access SDK configurations
+
+To view SDK configurations for a service:
+
+1. Navigate to [**APM** > **Services**][5].
+1. Open the **Service Page** for your service.
+1. Go to **Service Config** > **SDK & Agent Configurations** tab.
+
+The **SDK Configurations** section displays configurations for active instances of the service.
+
+## Configuration sources
+
+The configuration source shows where a given value is configured:
+
+| Source | Description |
+|--------|-------------|
+| **Remote Configuration at Runtime** | Set through the Datadog UI using [Configuration at Runtime][1] |
+| **Code** | Set in application code |
+| **Remote Fleet Automation** | Applied remotely at the host level through [Fleet Automation][2] |
+| **Local environment variable** | Set through an environment variable (or system property) in the runtime environment |
+| **Local file** | Set in a local configuration file |
+| **Default** | Default value provided by the SDK |
+
+## Missing configuration data
+
+Telemetry data is not available in the following situations:
+
+- No service instances have been active in the last 15 minutes.
+- Instrumentation telemetry has been disabled in configuration.
+- The instrumentation telemetry intake endpoint is not accessible (see [Network Destinations][3]).
+- The service name is manually set on spans (a [Service Override][4]).
+
+[1]: /tracing/trace_collection/runtime_config
+[2]: /agent/fleet_automation/remote_management
+[3]: /agent/configuration/network/#destinations
+[4]: /tracing/guide/base_service/#service-overrides
+[5]: https://app.datadoghq.com/software