Adds guidance docs to upgrade from old metrics

Author: jmckulk

docs/content/Upgrade/metrics.md

@@ -0,0 +1,78 @@
+---
+title: Monitoring Upgrade Guidance
+date:
+draft: false
+weight: 100
+---
+
+# Upgrade Guidance for PostgreSQL Operator Monitoring
+
+## Migration to Upstream Containers
+
+The Crunchy PostgreSQL Monitoring infrastructure now uses upstream Prometheus and Grafana
+containers. By default the installers will deploy the monitoring infrastructure using
+images from Docker Hub but can easily be updated to point to a Red Hat certified
+container repository. The Red Hat certified image catalog can be found
+[here](https://catalog.redhat.com/software/containers/explore) and the Docker Hub
+images can be found at the following links:
+
+- https://hub.docker.com/r/prom/prometheus
+- https://hub.docker.com/r/grafana/grafana
+- https://hub.docker.com/r/prom/alertmanager
+
+These containers are configurable through Kubernetes ConfigMaps and the updated
+PostgreSQL Operator Monitoring installers. Once deployed Prometheus and Grafana
+will be populated with resource data from metrics-enabled PostgreSQL clusters.
+
+## New Monitoring Features
+
+### Alerting
+The updated PostgreSQL Operator Monitoring Infrastructure supports deployment of
+Prometheus Alertmanager. This deployment uses upstream Prometheus
+Alertmanager images that can be installed and configured with the metrics
+installers and Kubernetes ConfigMaps.
+
+### Updated pgMonitor
+Prometheus and Grafana have been updated to include a default configuration from
+[pgMonitor](https://github.com/CrunchyData/pgmonitor) that is tailored for
+container-based PostgreSQL deployments. This updated configuration will show
+container specific resource information from your metrics-enabled PostgreSQL
+clusters. By default the metrics infrastructure will include:
+
+- New Grafana dashboards tailored for container-based PostgreSQL deployments
+- Container specific operating system metrics
+- General PostgreSQL alerting rules.
+
+### Updated Monitoring Installer
+The installer for the PostgreSQL Operating Monitoring infrastructure has been 
+split out into a separate set of installers. With each installer
+([Ansible]({{< relref "/installation/metrics/other/ansible" >}}),
+a [Kubectl job]({{< relref "installation/metrics/postgres-operator-metrics" >}}),
+or [Helm]({{< relref "/installation/metrics/other/helm-metrics" >}}))
+you will be able to apply custom configurations through Kubernetes
+ConfigMaps. This includes:
+
+- Custom Grafana dashboards and datasources
+- Custom Prometheus scrape configuration
+- Custom Prometheus alerting rules
+- Custom Alertmanager notification configuration
+
+## Updating from Pre-4.5.0 Monitoring
+
+Ensure that you have a copy of any install or custom configurations you have
+applied to your previous metrics install.
+
+You can upgrade the Grafana and Prometheus deployments in place by using the new
+installers. After you have updated the PostgreSQL Operator and configured the
+`values.yaml`, run the
+[metrics update]({{< relref "/installation/metrics/other/ansible/updating-metrics" >}}).
+This will replace the old deployments while keeping your pvcs in place.
+
+{{% notice tip %}}
+To make use of the updated exporter queries you must update
+the PostgreSQL Operator and
+[upgrade]({{< relref "/upgrade/automatedupgrade" >}})
+your cluster.
+{{% /notice %}}
+
+