Cherry-pick troubleshooting documentation from main branch (#4078)

Small Update to troubleshooting document (#3346)

* Updatng troubleshooting document

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* Restructure, rename and rewrite various troubleshooting documents

This commit adds the changes I have made thus far to the troubleshooting
section of NGINX Ingress Controller's documentation: there is more to be
done yet, but I am pushing these changes for others to see.

The product naming is inconsistent, as is the layout of the pages -
often, appropriate markdown is not used where it would make sense to,
and formatting is otherwise missing.

I will continue to update the documentation to fix these instances.

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---------

Signed-off-by: Jason Williams - NGIИX <jason.williams14@gmail.com>
Signed-off-by: Alan Dooley <ADubhlaoich@users.noreply.github.com>
Co-authored-by: Jason Williams - NGIИX <jason.williams14@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Luca Comellini <luca.com@gmail.com>

docs/content/troubleshooting/troubleshoot-common.md

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+---
+title: "Troubleshooting Common Issues"
+date: 2021-07-13T21:01:29-06:00
+description: "This page describes how to troubleshoot common problems with NGINX Ingress Controller."
+weight: 100
+draft: false
+toc: true
+tags: [ "docs" ]
+doctypes: ["troubleshooting"]
+aliases:
+ - /content/troubleshooting/troubleshoot-ingress-controller
+---
+
+## Common Problems
+
+The table below shows common problems with NGINX Ingress Controller you may encounter and how to address them. The following section explains how to gather additional information, and there is instruction available on fixing specific issues within the troubleshooting section of documentation.
+
+{{% table %}}
+| Problem Area | Symptom | Troubleshooting Method | Common Cause |
+|-----|-----|-----|-----|
+| Startup | NGINX Ingress Controller fails to start. | Check the logs. | Misconfigured RBAC, a missing default server TLS Secret.|
+| Ingress Resource and Annotations | The configuration is not applied | Check the events of the Ingress resource, check the logs, check the generated config. | Invalid values of annotations. |
+| VirtualServer and VirtualServerRoute Resources | The configuration is not applied. | Check the events of the VirtualServer and VirtualServerRoutes, check the logs, check the generated config. | VirtualServer or VirtualServerRoute is invalid. |
+| Policy Resource | The configuration is not applied. | Check the events of the Policy resource as well as the events of the VirtualServers that reference that policy, check the logs, check the generated config. | Policy is invalid. |
+| ConfigMap Keys | The configuration is not applied. | Check the events of the ConfigMap, check the logs, check the generated config.  | Invalid values of ConfigMap keys. |
+| NGINX | NGINX responds with unexpected responses. | Check the logs, check the generated config, check the live activity dashboard (NGINX Plus only), run NGINX in the debug mode. | Unhealthy backend pods, a misconfigured backend service. |
+{{% /table %}}
+
+## Troubleshooting Methods
+
+The commands in the next sections make the following assumptions:
+* That NGINX Ingress Controller is deployed in the namespace `nginx-ingress`.
+* `<nginx-ingress-pod>` is the name of one of the NGINX Ingress Controller pods.
+
+### Checking NGINX Ingress Controller Logs
+
+To check NGINX Ingress Controller logs, which include both information from NGINX Ingress Controller and NGINX's access and error logs, run the following command:
+
+```shell
+kubectl logs <nginx-ingress-pod> -n nginx-ingress
+```
+
+### Checking the Generated Config
+For each Ingress/VirtualServer resource, NGINX Ingress Controller generates a corresponding NGINX configuration file in the `/etc/nginx/conf.d folder`.
+
+ Additionally, NGINX Ingress Controller generates the main configuration file `/etc/nginx/nginx.conf`, which includes all the configurations files from `/etc/nginx/conf.d`. The configuration for a VirtualServerRoute resource is located in the configuration file of the VirtualServer that references the resource.
+
+You can view the content of the main configuration file by running:
+
+```shell
+kubectl exec <nginx-ingress-pod> -n nginx-ingress -- cat /etc/nginx/nginx.conf
+```
+
+Similarly, you can view the content of any generated configuration file in the `/etc/nginx/conf.d` folder.
+
+You can also print all NGINX configuration files together:
+
+```shell
+kubectl exec <nginx-ingress-pod> -n nginx-ingress -- nginx -T
+```
+
+However, this command will fail if any of the configuration files is not valid.
+
+### Checking the Live Activity Monitoring Dashboard
+
+The live activity monitoring dashboard shows the real-time information about NGINX Plus and the applications it is load balancing, which is helpful for troubleshooting. To access the dashboard, follow the steps from [here](/nginx-ingress-controller/logging-and-monitoring/status-page).
+
+### Enabling debugging for NGINX Ingress Controller
+
+For additional NGINX Ingress Controller debugging, you can enable debug settings to get more verbose logging.
+
+Increasing the debug log levels for NGINX Ingress Controller will also apply to NGINX itself.
+
+There are two settings that need to be set to enable more verbose logging for NGINX Ingress Controller:
+
+1. Command Line Arguments
+2. Configmap Settings
+
+**Command Line Arguments**
+
+When using `manifest` for deployment, use the command line argument `-nginx-debug` in your deployment or daemonset.
+
+If you want to increase the verbosity of the NGINX Ingress Controller process, you can also add the `-v` parameter.
+
+Here is a small snippet of setting these command line arguments in the `args` section of a deployment:
+
+```yaml
+args:
+  - -nginx-configmaps=$(POD_NAMESPACE)/nginx-config
+  - -enable-cert-manager
+  - -nginx-debug
+  - -v=3
+```
+
+**ConfigMap Settings**
+You can configure `error-log-level` in the NGINX Ingress Controller `configMap`:
+
+```yaml
+kind: ConfigMap
+apiVersion: v1
+metadata:
+  name: nginx-config
+  namespace: nginx-ingress
+data:
+  error-log-level: "debug"
+ ```
+
+**Using Helm**
+
+If you are using `helm`, you can adjust these two settings:
+
+```
+controller.nginxDebug = true or false
+controller.loglevel = 1 to 3 value
+```
+
+For example, if using a `values.yaml` file:
+
+```yaml
+  ## Enables debugging for NGINX. Uses the nginx-debug binary. Requires error-log-level: debug in ConfigMap via `controller.config.entries`.
+  nginxDebug: true
+
+  ## The log level of the Ingress Controller.
+  logLevel: 3
+```
+
+This is a more complete `values.yaml` file when using `helm`:
+
+```yaml
+controller:
+  kind: Deployment
+  nginxDebug: true
+  logLevel: 3
+  annotations:
+    nginx: ingress-prod
+  pod:
+    annotations:
+      prometheus.io/scrape: "true"
+      prometheus.io/port: "9113"
+      prometheus.io/scheme: http
+    extraLabels:
+      env: prod-weset
+  nginxplus: plus
+  image:
+    repository: nginx/nginx-ingress
+    tag: 2.4.1
+  # NGINX Configmap
+  config:
+    entries:
+      error-log-level: "debug"
+      proxy_connet_timeout: "5s"
+      http-snippets: |
+        underscores_in_headers on;
+  ingressClass: nginx
+```
+
+By enabling the `nginx-debug` CLI argument and changing the `error-log-level` to `debug`, you can capture more output to use for debugging.
+
+**NOTE**: It is recommended to only enable `nginx-debug` CLI and the `error-log-level` for debugging purposes.
+
+#### Example debug NGINX Ingress Controller Output
+These logs show some of the additional entries when debugging is enabled for NGINX Ingress Controller.
+
+```shell
+I1026 15:39:03.269092       1 manager.go:301] Reloading nginx with configVersion: 1
+I1026 15:39:03.269115       1 utils.go:17] executing /usr/sbin/nginx-debug -s reload -e stderr
+2022/10/26 15:39:03 [notice] 19#19: signal 1 (SIGHUP) received from 42, reconfiguring
+2022/10/26 15:39:03 [debug] 19#19: wake up, sigio 0
+2022/10/26 15:39:03 [notice] 19#19: reconfiguring
+2022/10/26 15:39:03 [debug] 19#19: posix_memalign: 000056362AF0A420:16384 @16
+2022/10/26 15:39:03 [debug] 19#19: add cleanup: 000056362AF0C318
+2022/10/26 15:39:03 [debug] 19#19: posix_memalign: 000056362AF48230:16384 @16
+2022/10/26 15:39:03 [debug] 19#19: malloc: 000056362AF00DE0:4096
+2022/10/26 15:39:03 [debug] 19#19: read: 46, 000056362AF00DE0, 3090, 0
+2022/10/26 15:39:03 [debug] 19#19: posix_memalign: 000056362AF58670:16384 @16
+2022/10/26 15:39:03 [debug] 19#19: malloc: 000056362AF12440:4280
+2022/10/26 15:39:03 [debug] 19#19: malloc: 000056362AF13500:4280
+2022/10/26 15:39:03 [debug] 19#19: malloc: 000056362AF145C0:4280
+2022/10/26 15:39:03 [debug] 19#19: malloc: 000056362AF5C680:4280
+2022/10/26 15:39:03 [debug] 19#19: malloc: 000056362AF5D740:4280
+2022/10/26 15:39:03 [debug] 19#19: malloc: 000056362AF5E800:4280
+2022/10/26 15:39:03 [debug] 19#19: posix_memalign: 000056362AF5F8C0:16384 @16
+2022/10/26 15:39:03 [debug] 19#19: malloc: 000056362AF41500:4096
+2022/10/26 15:39:03 [debug] 19#19: malloc: 000056362AF638D0:8192
+2022/10/26 15:39:03 [debug] 19#19: include /etc/nginx/mime.types
+2022/10/26 15:39:03 [debug] 19#19: include /etc/nginx/mime.types
+2022/10/26 15:39:03 [debug] 19#19: malloc: 000056362AF658E0:4096
+2022/10/26 15:39:03 [debug] 19#19: malloc: 000056362AF668F0:5349
+2022/10/26 15:39:03 [debug] 19#19: read: 47, 000056362AF658E0, 4096, 0
+2022/10/26 15:39:03 [debug] 19#19: malloc: 000056362AF67DE0:4096
+2022/10/26 15:39:03 [debug] 19#19: read: 47, 000056362AF658E1, 1253, 4096
+2022/10/26 15:39:03 [debug] 19#19: posix_memalign: 000056362AF68DF0:16384 @16
+2022/10/26 15:39:03 [debug] 19#19: posix_memalign: 000056362AF6CE00:16384 @16
+2022/10/26 15:39:03 [debug] 19#19: malloc: 000056362AF70E10:524288
+2022/10/26 15:39:03 [debug] 19#19: malloc: 000056362AFF0E20:524288
+2022/10/26 15:39:03 [debug] 19#19: malloc: 000056362B070E30:524288
+2022/10/26 15:39:03 [debug] 19#19: malloc: 000056362B0F0E40:400280
+```
+
+Once you have completed your debugging process, you can change the values back to the original values.

docs/content/troubleshooting/troubleshoot-configmap-policy.md

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+---
+title: Troubleshooting Policy Resources
+description: "This page describes how to troubleshoot NGINX Ingress Controller Policy Resources."
+weight: 200
+doctypes: [""]
+toc: true
+---
+
+## Policy Resources
+
+After you create or update a Policy resource, you can use `kubectl describe` to check whether or not NGINX Ingress Controller accepted the policy:
+
+```shell
+kubectl describe pol webapp-policy
+
+Events:
+  Type    Reason          Age   From                      Message
+  ----    ------          ----  ----                      -------
+  Normal  AddedOrUpdated  11s   nginx-ingress-controller  Policy default/webapp-policy was added or updated
+```
+
+The events section has a *Normal* event with the *AddedOrUpdated reason*, indicating the policy was successfully accepted.
+
+However, the fact that a policy was accepted doesn’t guarantee that the NGINX configuration was successfully applied.
+
+To verify the configuration applied, check the events of the [VirtualServer and VirtualServerRoute resources](/nginx-ingress-controller/troubleshooting/troubleshoot-virtualserver) that reference the policy.
+
+## ConfigMap Resources
+After you update the ConfigMap resource, you can immediately check if the configuration was successfully applied by NGINX:
+
+```shell
+kubectl describe configmap nginx-config -n nginx-ingress
+Name:         nginx-config
+Namespace:    nginx-ingress
+Labels:       <none>
+
+Events:
+  Type    Reason   Age                From                      Message
+  ----    ------   ----               ----                      -------
+  Normal  Updated  11s (x2 over 26m)  nginx-ingress-controller  Configuration from nginx-ingress/nginx-config was updated
+```
+
+Similar to *Policies*, the events section has a *Normal* event with the *AddedOrUpdated reason*, indicating the policy was successfully accepted.