Horizontal Pod Autoscaling

With Horizontal Pod Autoscaling, Kubernetes automatically scales the number of pods in a replication controller, deployment, or replica set based on observed CPU utilization (or, with alpha support, on some other, application-provided metrics).

The current stable version, which only includes support for CPU autoscaling, can be found in the autoscaling/v1 API version. The alpha version, which includes support for scaling on memory and custom metrics, can be found in autoscaling/v2beta1 (and autoscaling/v2beta2 in 1.12 and later).

kOps can assist in setting up HPA. Relevant reading you will need to go through:

• Extending the Kubernetes API with the aggregation layer
• Configure The Aggregation Layer
• Horizontal Pod Autoscaling

While the above links go into details on how Kubernetes needs to be configured to work with HPA, a lot of that work is already done for you by kOps. Specifically:

• Enable the Aggregation Layer via the following kube-apiserver flags:
• --requestheader-client-ca-file=<path to aggregator CA cert>
• --requestheader-allowed-names=aggregator
• --requestheader-extra-headers-prefix=X-Remote-Extra-
• --requestheader-group-headers=X-Remote-Group
• --requestheader-username-headers=X-Remote-User
• --proxy-client-cert-file=<path to aggregator proxy cert>
• --proxy-client-key-file=<path to aggregator proxy key>
• Enable Horizontal Pod Scaling … set the appropriate flags for kube-controller-manager:
• --horizontal-pod-autoscaler-use-rest-clients should be true.
• --kubeconfig <path-to-kubeconfig>

Cluster Configuration

Support For Multiple Metrics

To enable the resource metrics API for scaling on CPU and memory, install metrics-server (installation instruction here). The compatibility matrix is as follows:

Support For Custom Metrics

To enable the custom metrics API, register it via the API aggregation layer. If you’re using Prometheus, checkout the custom metrics adapter for Prometheus.