Monitoring docs (#209)

* Added docs for monitoring.

* Added links in monitoring docs.

* Added grafana dashboard image for monitoring docs, reordered how to's side menu.

* Moved grafana_dashboard.png to solve markdown path problem.

* Fixed metric names in docs.

* Test moving grafana_dashboard.png

* Fixed grafana_dashboard.png path in markdowns.

docs/howtos/clusterautoscaling.md

@@ -2,7 +2,7 @@
 layout: default
 title: Cluster Autoscaling
 parent: How to's
-nav_order: 5
+nav_order: 6
 ---
 
 # Cluster Autoscaling

docs/howtos/monitoring.md

@@ -0,0 +1,89 @@
+---
+layout: default
+title: Monitoring
+parent: How to's
+nav_order: 5
+---
+
+# Monitoring
+
+Thundernetes is able to export game server related metrics to a [Prometheus](https://prometheus.io/docs/introduction/overview/) server, and these can also be imported
+to a [Grafana](https://grafana.com/docs/grafana/latest/introduction/) server for easy and intuitive visualizations.
+
+[![Grafana Dasboard Example](../assets/images/grafana_dashboard.png)](../assets/images/grafana_dashboard.png)
+
+Prometheus uses a pull model to retrieve data, and needs apps to implement an endpoint that responds to its HTTP requests. For this, Thundernetes exposes the following endpoints:
+
+* **{controller manager service IP}:8080/metrics**
+* **{nodeagent service IP}:56001/metrics**
+
+## Install Thundernetes with Prometheus and Grafana
+
+While it's possible to create and manage your own Prometheus and Grafana instances to consume the endpoints described above, it is also possible to install both into your K8s cluster using very few steps thanks to the [kube-prometheus](https://github.com/prometheus-operator/kube-prometheus) project. This will install the prometheus-operator and Grafana, and will connect them automatically. For this, follow these steps:
+
+```bash
+# clone the kube-prometheus repository
+git clone https://github.com/prometheus-operator/kube-prometheus.git
+
+cd prometheus-operator/
+
+# install kube-prometheus' CRDs
+kubectl create -f manifests/setup
+until kubectl get servicemonitors --all-namespaces ; do date; sleep 1; echo ""; done
+kubectl create -f manifests/
+```
+
+After this, you can install Thundernetes using the install files "with monitoring", these automatically create Prometheus ServiceMonitors that crawl the endpoints described above.
+
+```bash
+kubectl apply -f https://github.com/PlayFab/thundernetes/main/installfiles/operator_with_monitoring.yaml
+```
+
+## Check the data in Prometheus and Grafana
+
+To test this, you can install the netcore Game Server Build sample, this is a basic application that uses GSDK to send information to Thundernetes. You should also allocate a server so you can see the data.
+
+```bash
+kubectl apply -f https://github.com/PlayFab/thundernetes/main/samples/netcore/sample-requestslimits.yaml
+```
+This will create a Game Server Build with 2 standby Game Servers, you can check they were successfully created like this:
+
+```bash
+# check the build
+kubectl get gsb
+
+# check the servers
+kubectl get gs
+```
+ To allocate a server, you need to have access to the thundernetes-controller-manager IP, in an AKS cluster you can get that like this:
+ ```bash
+ export IP=$(kubectl get svc -n thundernetes-system thundernetes-controller-manager -o jsonpath='{.status.loadBalancer.ingress[0].ip}')
+ ```
+
+ Then allocate the server. The buildId must be the same than the one in the YAML file of the netcore sample, and the sessionId is used to identify the session:
+ ```bash
+curl -H 'Content-Type: application/json' -d '{"buildID":"85ffe8da-c82f-4035-86c5-9d2b5f42d6f6","sessionID":"ac1b7082-d811-47a7-89ae-fe1a9c48a6da"}' http://${IP}:5000/api/v1/allocate
+ ```
+
+You can check the data exported in Prometheus, to access the Prometheus instance in your cluster use  port forwarding and open localhost:9090 in your browser:
+```bash
+kubectl --namespace monitoring port-forward svc/prometheus-k8s 9090
+```
+
+You can check the same data in Grafana and create a custom dashboard, to access the Grafana instance in your cluster use port forwarding and open localhost:3000 in your browser:
+```bash
+kubectl --namespace monitoring port-forward svc/grafana 3000
+```
+There is a custom Grafana dashboard example that visualizes some of this data in the [samples/grafana](https://github.com/PlayFab/thundernetes/tree/main/samples/grafana) directory.
+
+## List of exported Prometheus metrics
+| Metric name | Metric type | Source |
+| --- | --- | --- |
+| gameserver_states | Gauge | nodeagent |
+| connected_players | Gauge | nodeagent |
+| gameservers_current_state_per_build | Gauge | controller-manager |
+| gameservers_created_total | Counter | controller-manager |
+| gameservers_sessionended_total | Counter | controller-manager |
+| gameservers_crashed_total | Counter | controller-manager |
+| gameservers_deleted_total | Counter | controller-manager |
+| allocations_total | Counter | controller-manager |

docs/howtos/upgradebuild.md

@@ -2,7 +2,7 @@
 layout: default
 title: Upgrading your game server
 parent: How to's
-nav_order: 8
+nav_order: 9
 ---
 
 # Upgrading your game server

samples/grafana/readme.md

@@ -1,5 +1,5 @@
 # Sample Grafana Dashboard
 
-![example dashboard image](./ExampleDashboard.jpg)
+[![Grafana Dasboard Example](../../docs/assets/images/grafana_dashboard.png)](../../docs/assets/images/grafana_dashboard.pnggrafana_dashboard.png)
 
 The `dashboard.json` file in this folder can be imported to grafana to provide a simple example of retrieving metrics from the Thundernetes Controller. It makes the assumption that the Prometheus data source is named `Prometheus`, so you may need to edit the json file before importing if your Grafana installation uses a different name.