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Requests per Second Demo

This repository contains a demo that shows how to use custom metrics to autoscale an Application. When combined with Virtual Kubelet, this lets you scale quickly to virtual nodes where you'll pay only for the container instance runtime. This repository will guide you through first installing the Prometheus Operator, followed by creating a Prometheus instance and installing the Prometheus Metric Adapter. With these in place, the provided Helm chart will install our demo application, along with supporting monitoring components, like a ServiceMonitor for Prometheus, a Horizontal Pod Autoscaler, and a custom container that will count the instances of the application and expose them to Prometheus.

The container counter can be found at https://github.com/jeremyrickard/prometheus-containercounter

Install Prometheus Operator

We will use the Prometheus Operator to create the Prometheus cluster and to create the relevant configuration to monitor our app. So first, install the operator:

kubectl apply -f https://raw.githubusercontent.com/coreos/prometheus-operator/master/bundle.yaml

This will create a number of CRDs, Service Accounts and RBAC things. Once it's finished, you'll have the Prometheus Operator, but not a Prometheus instance. You'll need to create one of those next.

Create a Prometheus instance

kubectl apply -f prometheus-config/prometheus

This will create a single replica Prometheus instance.

Expose a Service for Prometheus instance

kubectl expose pod prometheus-prometheus-0 --port 9090 --target-port 9090

Deploy The Adopt Dog App

You will need your Virtual Kubelet node name to install the app. The app will install a counter that will get the pod count for the application and provide a metric for pods on Virtual Kubelet and pods on all other nodes.

$ kubectl get nodes
AME                       STATUS    ROLES     AGE       VERSION
aks-nodepool1-30440750-0   Ready     agent     27d       v1.10.6
aks-nodepool1-30440750-1   Ready     agent     27d       v1.10.6
aks-nodepool1-30440750-2   Ready     agent     27d       v1.10.6
virtual-kubelet            Ready     agent     16h       v1.8.3

In this case, it's Virtual Kubelet. If you've installed with the ACI Connector, you may have a node name like virtual-kubelet-aci-connector-linux-westcentralus.

Export the node name to an environment variable

$ export VK_NODE_NAME=<your_node_name>

```bash
helm install ./charts/adoptdog --name rps-prom --set counter.specialNodeName=$VK_NODE_NAME

This will deploy with an ingress and should create the HPA, Prometheus ServiceMonitor and everything else needed, except the adapter. Do that next.

Change the values.yaml as needed (especially for ingress)

Deploy the Prometheus Metric Adapter

helm install stable/prometheus-adapter --name prometheus-adaptor -f prometheus-config/prometheus-adapter/values.yaml

NOTE: if you have the Azure application insights adapter installed, you'll need to remove that first.

There might be some lag time between when you create the adapter and when the metrics are available.

kubectl get --raw /apis/custom.metrics.k8s.io/v1beta1/namespaces/default/pod/*/requests_per_second | jq .

This should show metrics if everything is setup correctly. Example:

$ kubectl get --raw /apis/custom.metrics.k8s.io/v1beta1/namespaces/default/pod/*/requests_per_second | jq .
{
  "kind": "MetricValueList",
  "apiVersion": "custom.metrics.k8s.io/v1beta1",
  "metadata": {
    "selfLink": "/apis/custom.metrics.k8s.io/v1beta1/namespaces/default/pod/%2A/requests_per_second"
  },
  "items": [
    {
      "describedObject": {
        "kind": "Pod",
        "namespace": "default",
        "name": "rps-prom-adoptdog-8684976576-7hvc9",
        "apiVersion": "/__internal"
      },
      "metricName": "requests_per_second",
      "timestamp": "2018-09-05T03:57:44Z",
      "value": "0"
    },
    {
      "describedObject": {
        "kind": "Pod",
        "namespace": "default",
        "name": "rps-prom-adoptdog-8684976576-p6wm7",
        "apiVersion": "/__internal"
      },
      "metricName": "requests_per_second",
      "timestamp": "2018-09-05T03:57:44Z",
      "value": "0"
    }
  ]
}

Hit it with some Load

I've been using Hey

export GOPATH=~/go
export PATH=$GOPATH/bin:$PATH
go get -u github.com/rakyll/hey
hey -z 20m http://<whatever-the-ingress-url-is>

Watch it scale

$ kubectl get hpa rps-prom-adoptdog -w
NAME                REFERENCE                      TARGETS   MINPODS   MAXPODS   REPLICAS   AGE
rps-prom-adoptdog   Deployment/rps-prom-adoptdog   0 / 10    2         10        2          4m
rps-prom-adoptdog   Deployment/rps-prom-adoptdog   128500m / 10   2         10        2         4m
rps-prom-adoptdog   Deployment/rps-prom-adoptdog   170500m / 10   2         10        4         5m
rps-prom-adoptdog   Deployment/rps-prom-adoptdog   111500m / 10   2         10        4         5m
rps-prom-adoptdog   Deployment/rps-prom-adoptdog   95250m / 10   2         10        4         6m
rps-prom-adoptdog   Deployment/rps-prom-adoptdog   141 / 10   2         10        4         6m

Overtime, this should go up.

Some Prometheus Queries

Rounded average requests per second per container

round(avg(irate(request_durations_histogram_secs_count[1m])))

Rounded total requests per second

round(sum(irate(request_durations_histogram_secs_count[1m])))

Individual number of data points, should correspond to number of containers

count(irate(request_durations_histogram_secs_count[1m]))

The number of containers running, per the counter

running_containers

Average response time in seconds:

avg(request_durations_histogram_secs_sum / request_durations_histogram_secs_count)