Update index pages for EDOT troubleshooting documentation (#4184)

## Summary

This PR audits and improves the IA and interlinking of the EDOT
troubleshooting documentation. It rewrites the original index pages and
adds contextual links to improve navigation.

Closes #3426 

## Generative AI disclosure
Did you use a generative AI (GenAI) tool to assist in creating this
contribution?
[x] Yes
[ ] No
If you answered "Yes" to the previous question, please specify the
tool(s) and model(s) used (e.g., Google Gemini, OpenAI ChatGPT-4, etc.).
Tool(s) and model(s) used: Cursor AI (Claude Sonnet 4.5)

Author: alexandra5000

troubleshoot/ingest/opentelemetry/429-errors-motlp.md

@@ -51,7 +51,7 @@ A 429 status means that the rate of requests sent to the Managed OTLP endpoint h
     Refer to the [Rate limiting section](opentelemetry://reference/motlp.md#rate-limiting) in the mOTLP reference documentation for details.
 
 * In {{ech}}, the {{es}} capacity for your deployment might be underscaled for the current ingest rate.
-* In {{serverless-full}}, rate limiting should not result from {{es}} capacity, since the platform automatically scales ingest capacity. If you suspect a scaling issue, [contact Elastic Support](contact-support.md).
+* In {{serverless-full}}, rate limiting should not result from {{es}} capacity, since the platform automatically scales ingest capacity. If you suspect a scaling issue, [contact Elastic Support](/troubleshoot/ingest/opentelemetry/contact-support.md).
 * Multiple Collectors or SDKs are sending data concurrently without load balancing or backoff mechanisms.
 
 ## Resolution
@@ -62,7 +62,7 @@ To resolve 429 errors, identify whether the bottleneck is caused by ingest limit
 
 If you’ve confirmed that your ingest configuration is stable but still encounter 429 errors:
 
-* {{serverless-full}}: [Contact Elastic Support](contact-support.md) to request an increase in ingest limits.
+* {{serverless-full}}: [Contact Elastic Support](/troubleshoot/ingest/opentelemetry/contact-support.md) to request an increase in ingest limits.
 * {{ech}} (ECH): Increase your {{es}} capacity by scaling or resizing your deployment:
   * [Scaling considerations](../../../deploy-manage/production-guidance/scaling-considerations.md)
   * [Resize deployment](../../../deploy-manage/deploy/cloud-enterprise/resize-deployment.md)
@@ -106,7 +106,7 @@ exporters:
       enabled: true
 ```
 
-This ensures the Collector buffers data locally while waiting for the ingest endpoint to recover from throttling.
+This ensures the Collector buffers data locally while waiting for the ingest endpoint to recover from throttling. For more information on export failures and queue configuration, refer to [Export failures when sending telemetry data](/troubleshoot/ingest/opentelemetry/edot-collector/trace-export-errors.md).
 
 ## Best practices
 

troubleshoot/ingest/opentelemetry/connectivity.md

@@ -2,7 +2,7 @@
 navigation_title: Connectivity issues
 description: Troubleshoot connectivity issues between EDOT SDKs, the EDOT Collector, and Elastic.
 applies_to:
-  serverless: all
+  serverless: ga
   product:
       edot_collector: ga  
 products:
@@ -75,14 +75,14 @@ Connectivity errors usually trace back to one of the following issues:
 Errors can look similar whether they come from an SDK or the Collector. Identifying the source helps you isolate the problem.
 
 :::{note}
-Note: Some SDKs support setting a proxy directly (for example, using `HTTPS_PROXY`). Refer to [Proxy settings for EDOT SDKs](../opentelemetry/edot-sdks/proxy.md) for details.
+Note: Some SDKs support setting a proxy directly (for example, using `HTTPS_PROXY`). Refer to [Proxy settings for EDOT SDKs](/troubleshoot/ingest/opentelemetry/edot-sdks/proxy.md) for details.
 :::
 
 #### SDK
 
 Application logs report failures when the SDK cannot send data to the Collector or directly to Elastic. These often appear as `connection refused` or `timeout` messages. If seen, verify that the Collector endpoint is reachable.
 
-For guidance on enabling logs in your SDK, see [Enable SDK debug logging](../opentelemetry/edot-sdks/enable-debug-logging.md).
+For guidance on enabling logs in your SDK, refer to [Enable SDK debug logging](/troubleshoot/ingest/opentelemetry/edot-sdks/enable-debug-logging.md).
 
 Example (Java SDK):
 
@@ -154,6 +154,6 @@ If basic checks and configuration look correct but issues persist, collect more
 
 * Review proxy settings. For more information, refer to [Proxy settings](opentelemetry://reference/edot-collector/config/proxy.md).
 
-* If ports are confirmed open but errors persist, [enable debug logging in the SDK](../opentelemetry/edot-sdks/enable-debug-logging.md) or [in the Collector](../opentelemetry/edot-collector/enable-debug-logging.md) for more detail.
+* If ports are confirmed open but errors persist, [enable debug logging in the SDK](/troubleshoot/ingest/opentelemetry/edot-sdks/enable-debug-logging.md) or [in the Collector](/troubleshoot/ingest/opentelemetry/edot-collector/enable-debug-logging.md) for more detail.
 
 * Contact your network administrator with test results if you suspect firewall restrictions.

troubleshoot/ingest/opentelemetry/contact-support.md

@@ -77,7 +77,7 @@ To help Elastic Support investigate the problem efficiently, please include the
 
 ### Logs and diagnostics
 
-* Recent Collector logs with relevant errors or warning messages
+* Recent Collector logs with relevant errors or warning messages. For guidance on enabling debug logging, refer to [Enable debug logging for the EDOT Collector](/troubleshoot/ingest/opentelemetry/edot-collector/enable-debug-logging.md) or [Enable debug logging for EDOT SDKs](/troubleshoot/ingest/opentelemetry/edot-sdks/enable-debug-logging.md).
 * Output from:
 
   ```bash
@@ -92,7 +92,7 @@ To help Elastic Support investigate the problem efficiently, please include the
 
 ### Data and UI symptoms
 
-* Are traces, metrics, or logs missing from the UI?
+* Are traces, metrics, or logs missing from the UI? For troubleshooting steps, refer to [No data visible in {{kib}}](/troubleshoot/ingest/opentelemetry/no-data-in-kibana.md) or [No application-level telemetry visible in {{kib}}](/troubleshoot/ingest/opentelemetry/edot-sdks/missing-app-telemetry.md).
 * Are you using the [Elastic Managed OTLP endpoint](https://www.elastic.co/docs/observability/apm/otel/managed-otel-ingest/)?
 * If data is missing or incomplete, consider enabling the [debug exporter](https://github.com/open-telemetry/opentelemetry-collector/blob/main/exporter/debugexporter/README.md) to inspect the raw signal data emitted by the Collector. 
 

troubleshoot/ingest/opentelemetry/edot-collector/collector-not-starting.md

@@ -66,7 +66,7 @@ If you're deploying the EDOT Collector in a standalone configuration, try to:
    ./otelcol --set=service.telemetry.logs.level=debug
    ```
 
-   This is especially helpful for diagnosing configuration parsing issues or startup errors.
+   This is especially helpful for diagnosing configuration parsing issues or startup errors. For more information on enabling debug logging, refer to [Enable debug logging](/troubleshoot/ingest/opentelemetry/edot-collector/enable-debug-logging.md).
 
 
 * Confirm required components are defined
@@ -95,7 +95,7 @@ If you're deploying the EDOT Collector in a standalone configuration, try to:
    lsof -i :4317
    ```
 
-   If needed, adjust your configuration or free up the port.
+   If needed, adjust your configuration or free up the port. For network connectivity issues, refer to [Connectivity issues](/troubleshoot/ingest/opentelemetry/connectivity.md).
 
 ### Kubernetes EDOT Collector
 
@@ -117,6 +117,8 @@ If you're deploying the EDOT Collector using the Elastic Helm charts, try to:
 
   Common issues include volume mount errors, image pull failures, or misconfigured environment variables.
 
+If the Collector starts but no data appears in {{kib}}, refer to [No data visible in {{kib}}](/troubleshoot/ingest/opentelemetry/no-data-in-kibana.md) for additional troubleshooting steps.
+
 ## Resources
 
 * [Collector configuration documentation](https://opentelemetry.io/docs/collector/configuration/)

troubleshoot/ingest/opentelemetry/edot-collector/collector-oomkilled.md

@@ -17,6 +17,8 @@ products:
 
 If your EDOT Collector pods terminate with an `OOMKilled` status, this usually indicates sustained memory pressure or potentially a memory leak due to an introduced regression or a bug. You can use the Performance Profiler (`pprof`) extension to collect and analyze memory profiles, helping you identify the root cause of the issue.
 
+If you're running the Collector in Kubernetes and experiencing resource allocation issues, refer to [Insufficient resources in Kubernetes](/troubleshoot/ingest/opentelemetry/edot-collector/insufficient-resources-kubestack.md) for troubleshooting steps.
+
 ## Symptoms
 
 These symptoms typically indicate that the EDOT Collector is experiencing a memory-related failure:
@@ -25,6 +27,8 @@ These symptoms typically indicate that the EDOT Collector is experiencing a memo
 - Memory usage steadily increases before the crash.
 - The Collector's logs don't show clear errors before termination.
 
+For more detailed diagnostics, refer to [Enable debug logging](/troubleshoot/ingest/opentelemetry/edot-collector/enable-debug-logging.md).
+
 ## Resolution
 
 Turn on runtime profiling using the `pprof` extension and then gather memory heap profiles from the affected pod:

troubleshoot/ingest/opentelemetry/edot-collector/enable-debug-logging.md

@@ -88,4 +88,4 @@ Debug logging for the Collector is not currently configurable through {{fleet}}.
 
 ## Resources
 
-To learn how to enable debug logging for the EDOT SDKs, refer to [Enable debug logging for EDOT SDKs](../edot-sdks/enable-debug-logging.md).
+To learn how to enable debug logging for the EDOT SDKs, refer to [Enable debug logging for EDOT SDKs](/troubleshoot/ingest/opentelemetry/edot-sdks/enable-debug-logging.md).

troubleshoot/ingest/opentelemetry/edot-collector/index.md

@@ -13,18 +13,36 @@ products:
 
 # Troubleshoot the EDOT Collector
 
-Perform these checks when troubleshooting common Collector issues:
-
-* Check logs: Review the Collector’s logs for error messages.
-* Validate configuration: Use the `--dry-run` option to test configurations.
-* Enable debug logging: Run the Collector with `--log-level=debug` for detailed logs.
-* Check service status: Ensure the Collector is running with `systemctl status <collector-service>` (Linux) or `tasklist` (Windows).
-* Test connectivity: Use `telnet <endpoint> <port>` or `curl` to verify backend availability.
-* Check open ports: Run netstat `-tulnp or lsof -i` to confirm the Collector is listening.
-* Monitor resource usage: Use top/htop (Linux) or Task Manager (Windows) to check CPU & memory.
-* Validate exporters: Ensure exporters are properly configured and reachable.
-* Verify pipelines: Use `otelctl` diagnose (if available) to check pipeline health.
-* Check permissions: Ensure the Collector has the right file and network permissions.
-* Review recent changes: Roll back recent config updates if the issue started after changes.
-
-For in-depth details on troubleshooting refer to the [OpenTelemetry Collector troubleshooting documentation](https://opentelemetry.io/docs/collector/troubleshooting/).
+Use the topics in this section to troubleshoot issues with the EDOT Collector.
+
+If you're not sure where to start, review the Collector's logs for error messages and validate your configuration using the `--dry-run` option. For more detailed diagnostics, refer to [Enable debug logging](/troubleshoot/ingest/opentelemetry/edot-collector/enable-debug-logging.md).
+
+## Resource issues
+
+* [Collector out of memory](/troubleshoot/ingest/opentelemetry/edot-collector/collector-oomkilled.md): Diagnose and resolve out-of-memory issues in the EDOT Collector using Go's Performance Profiler.
+
+* [Insufficient resources in {{k8s}}](/troubleshoot/ingest/opentelemetry/edot-collector/insufficient-resources-kubestack.md): Troubleshoot resource allocation issues when running the EDOT Collector in {{k8s}} environments.
+
+## Configuration issues
+
+* [Collector doesn't start](/troubleshoot/ingest/opentelemetry/edot-collector/collector-not-starting.md): Resolve startup failures caused by invalid configuration, port conflicts, or missing components.
+
+* [Missing or incomplete traces due to Collector sampling](/troubleshoot/ingest/opentelemetry/edot-collector/misconfigured-sampling-collector.md): Troubleshoot missing or incomplete traces caused by sampling configuration.
+
+* [Collector doesn't propagate client metadata](/troubleshoot/ingest/opentelemetry/edot-collector/metadata.md): Learn why the Collector doesn't extract custom attributes and how to propagate such values using EDOT SDKs.
+
+## Connectivity and export issues
+
+* [Export failures when sending telemetry data](/troubleshoot/ingest/opentelemetry/edot-collector/trace-export-errors.md): Resolve export failures caused by `sending_queue` overflow and {{es}} exporter timeouts.
+
+## Debugging
+
+* [Enable debug logging](/troubleshoot/ingest/opentelemetry/edot-collector/enable-debug-logging.md): Learn how to enable debug logging for the EDOT Collector in supported environments.
+
+## See also
+
+* [EDOT SDKs troubleshooting](/troubleshoot/ingest/opentelemetry/edot-sdks/index.md): For end-to-end issues that may involve both the Collector and SDKs.
+
+* [Troubleshoot EDOT](/troubleshoot/ingest/opentelemetry/index.md): Overview of all EDOT troubleshooting resources.
+
+For in-depth details on troubleshooting, refer to the contrib [OpenTelemetry Collector troubleshooting documentation](https://opentelemetry.io/docs/collector/troubleshooting/).

troubleshoot/ingest/opentelemetry/edot-collector/insufficient-resources-kubestack.md

@@ -25,6 +25,8 @@ These symptoms are common when the Kube-Stack chart is deployed with insufficien
 - Cluster or Daemon pods are unable to export data to the Gateway collector due being `OOMKilled` (high memory usage). 
 - Pods have logs similar to: `error	internal/queue_sender.go:128	Exporting failed. Dropping data.`
 
+For detailed diagnostics on OOMKilled issues, refer to [Collector out of memory](/troubleshoot/ingest/opentelemetry/edot-collector/collector-oomkilled.md). For more information on enabling debug logging, refer to [Enable debug logging](/troubleshoot/ingest/opentelemetry/edot-collector/enable-debug-logging.md).
+
 ## Resolution
 
 Follow these steps to resolve the issue.

troubleshoot/ingest/opentelemetry/edot-collector/metadata.md

@@ -62,7 +62,7 @@ This will not work, as the Collector doesn't automatically extract such values f
 
 ## Resolution
 
-If you want to propagate customer IDs or project names into spans or metrics, you must instrument this in your code using one of the SDKs.
+If you want to propagate customer IDs or project names into spans or metrics, you must instrument this in your code using one of the SDKs. For SDK-specific troubleshooting guidance, refer to [EDOT SDKs troubleshooting](/troubleshoot/ingest/opentelemetry/edot-sdks/index.md).
 
 Use `span.set_attribute` in your application code, where OpenTelemetry spans are created. For example:
 

troubleshoot/ingest/opentelemetry/edot-collector/misconfigured-sampling-collector.md

@@ -2,7 +2,7 @@
 navigation_title: Collector sampling issues
 description: Learn how to troubleshoot missing or incomplete traces in the EDOT Collector caused by sampling configuration.
 applies_to:
-  serverless: all
+  serverless: ga
   product:
     edot_collector: ga  
 products:
@@ -12,11 +12,11 @@ products:
 
 # Missing or incomplete traces due to Collector sampling
 
-If traces or spans are missing in {{kib}}, the issue might be related to the Collector’s sampling configuration. 
+If traces or spans are missing in {{kib}}, the issue might be related to the Collector's sampling configuration. For general troubleshooting when no data appears in {{kib}}, refer to [No data visible in {{kib}}](/troubleshoot/ingest/opentelemetry/no-data-in-kibana.md). 
 
 {applies_to}`stack: ga 9.2` Tail-based sampling (TBS) allows the Collector to evaluate entire traces before deciding whether to keep them. If TBS policies are too strict or not aligned with your workloads, traces you expect to see may be dropped.
 
-Both Collector-based and SDK-level sampling can lead to gaps in telemetry if not configured correctly. See [Missing or incomplete traces due to SDK sampling](../edot-sdks/misconfigured-sampling-sdk.md) for more information.
+Both Collector-based and SDK-level sampling can lead to gaps in telemetry if not configured correctly. Refer to [Missing or incomplete traces due to SDK sampling](/troubleshoot/ingest/opentelemetry/edot-sdks/misconfigured-sampling-sdk.md) for more information.
 
 ## Symptoms
 
@@ -79,4 +79,4 @@ Follow these steps to resolve sampling configuration issues:
 
 - [Tail sampling processor (Collector)](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/processor/tailsamplingprocessor)
 - [OpenTelemetry sampling concepts - contrib documentation](https://opentelemetry.io/docs/concepts/sampling/) 
-- [Missing or incomplete traces due to SDK sampling](../edot-sdks/misconfigured-sampling-sdk.md)
+- [Missing or incomplete traces due to SDK sampling](/troubleshoot/ingest/opentelemetry/edot-sdks/misconfigured-sampling-sdk.md)