Merge branch 'docs/monitoring-index' into 'master'

Link Monitor docs to the front page

Closes #45006

See merge request gitlab-org/gitlab-ce!18314

doc/README.md

@@ -159,8 +159,12 @@ applications are always responsive and available. GitLab collects and displays
 performance metrics for deployed apps using Prometheus so you can know in an
 instant how code changes impact your production environment.
+- [GitLab Prometheus](administration/monitoring/prometheus/index.md): Configure the bundled Prometheus to collect various metrics from your GitLab instance.
+- [Prometheus project integration](user/project/integrations/prometheus.md): Configure the Prometheus integration per project and monitor your CI/CD environments.
+- [Prometheus metrics](user/project/integrations/prometheus_library/metrics.md): Let Prometheus collect metrics from various services, like Kubernetes, NGINX, NGINX ingress controller, HAProxy, and Amazon Cloud Watch.
+- [GitLab Performance Monitoring](administration/monitoring/performance/index.md): Use InfluxDB and Grafana to monitor the performance of your GitLab instance (will be eventually replaced by Prometheus).
+- [Health check](user/admin_area/monitoring/health_check.md): GitLab provides liveness and readiness probes to indicate service health and reachability to required services.
 - [GitLab Cycle Analytics](user/project/cycle_analytics.md): Cycle Analytics measures the time it takes to go from an [idea to production](https://about.gitlab.com/2016/08/05/continuous-integration-delivery-and-deployment-with-gitlab/#from-idea-to-production-with-gitlab) for each project you have.
-- [GitLab Performance Monitoring](administration/monitoring/performance/index.md)
 ## Getting started with GitLab

doc/user/project/integrations/prometheus_library/cloudwatch.md

@@ -6,7 +6,7 @@ GitLab has support for automatically detecting and monitoring AWS resources, sta
 ## Requirements
-The [Prometheus service](../prometheus/index.md) must be enabled.
+The [Prometheus service](../prometheus.md) must be enabled.
 ## Metrics supported

doc/user/project/integrations/prometheus_library/haproxy.md

@@ -5,7 +5,7 @@ GitLab has support for automatically detecting and monitoring HAProxy. This is p
 ## Requirements
-The [Prometheus service](../prometheus/index.md) must be enabled.
+The [Prometheus service](../prometheus.md) must be enabled.
 ## Metrics supported

doc/user/project/integrations/prometheus_library/metrics.md

 # Prometheus Metrics library
+
 > [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/8935) in GitLab 9.0
 GitLab offers automatic detection of select [Prometheus exporters](https://prometheus.io/docs/instrumenting/exporters/). Currently supported exporters are:
@@ -15,7 +16,7 @@ We have tried to surface the most important metrics for each exporter, and will
 GitLab retrieves performance data from the configured Prometheus server, and attempts to identifying the presence of known metrics. Once identified, GitLab then needs to be able to map the data to a particular environment.
 In order to isolate and only display relevant metrics for a given environment, GitLab needs a method to detect which labels are associated. To do that,
-GitLab uses the defined queries and fills in the environment specific variables. Typically this involves looking for the [$CI_ENVIRONMENT_SLUG](https://docs.gitlab.com/ee/ci/variables/#predefined-variables-environment-variables), but may also include other information such as the project's Kubernetes namespace. Each search query is defined in the [exporter specific documentation](#prometheus-metrics-library).
+GitLab uses the defined queries and fills in the environment specific variables. Typically this involves looking for the [$CI_ENVIRONMENT_SLUG](../../../../ci/variables/README.md#predefined-variables-environment-variables), but may also include other information such as the project's Kubernetes namespace. Each search query is defined in the [exporter specific documentation](#prometheus-metrics-library).
 ## Adding to the library

doc/user/project/integrations/prometheus_library/nginx.md

@@ -6,7 +6,7 @@ GitLab has support for automatically detecting and monitoring NGINX. This is pro
 ## Requirements
-The [Prometheus service](../prometheus/index.md) must be enabled.
+The [Prometheus service](../prometheus.md) must be enabled.
 ## Metrics supported

doc/user/project/integrations/prometheus_library/nginx_ingress.md

@@ -6,7 +6,7 @@ GitLab has support for automatically detecting and monitoring the Kubernetes NGI
 ## Requirements
-[Prometheus integration](../prometheus/index.md) must be active.
+[Prometheus integration](../prometheus.md) must be active.
 ## Metrics supported
@@ -27,7 +27,7 @@ For other deployments, there is [some configuration](#manually-setting-up-nginx-
 ### About managed NGINX Ingress deployments
-NGINX Ingress is deployed into the `gitlab-managed-apps` namespace, using the [official Helm chart](https://github.com/kubernetes/charts/tree/master/stable/nginx-ingress). NGINX Ingress will be [externally reachable via the Load Balancer's IP](https://docs.gitlab.com/ce/user/project/clusters/index.html#getting-the-external-ip-address).
+NGINX Ingress is deployed into the `gitlab-managed-apps` namespace, using the [official Helm chart](https://github.com/kubernetes/charts/tree/master/stable/nginx-ingress). NGINX Ingress will be [externally reachable via the Load Balancer's IP](../../clusters/index.md#getting-the-external-ip-address).
 NGINX is configured for Prometheus monitoring, by setting:
 * `enable-vts-status: "true"`, to export Prometheus metrics
@@ -51,4 +51,4 @@ Managing these settings depends on how NGINX ingress has been deployed. If you h
 In order to isolate and only display relevant metrics for a given environment, GitLab needs a method to detect which labels are associated. To do this, GitLab will search for metrics with appropriate labels. In this case, the `upstream` label must be of the form `<KUBE_NAMESPACE>-<CI_ENVIRONMENT_SLUG>-*`.
-If you have used [Auto Deploy](https://docs.gitlab.com/ee/ci/autodeploy/index.html) to deploy your app, this format will be used automatically and metrics will be detected with no action on your part.
+If you have used [Auto Deploy](../../../../topics/autodevops/index.md#auto-deploy) to deploy your app, this format will be used automatically and metrics will be detected with no action on your part.