Autoscaling
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The Horizontal Pod Autoscaling (HPA) system offers a smart solution, enabling automatic extension of the Pod quantity based on CPU usage or an application's custom metrics. It seamlessly supports replication controllers, deployments and replica sets.
Monitor managers survey the resource usage of the metrics every 15 seconds (adjustable via --horizontal-pod-autoscaler-sync-period)
It can work with three types of metrics:
Predefined metrics (like Pod's CPU) are calculated as a ratio or usage rate
Custom Pod metrics are calculated as raw value amounts
Custom object metrics
Metrics can be retrieved using Heapster or the customized REST API
It is capable of managing multiple metrics
Do note that the extent of our discussion here is limited to Pod's automatic scaling; to comprehend Node's automatic scaling, refer to . Before using the HPA, further, it is necessary to ensure that the is properly deployed.
v1.5+
autoscaling/v1
CPU
v1.6+
autoscaling/v2beta1
Memory and Custom
The snippet above walks you through an example; from creating a pod and service, generating an autoscaler, increasing loads to finally witnessing the reduction of load and automatic reduction of pod quantity. This offers an illustrative explanation of how the autoscaling functions.
For example, HorizontalPodAutoscaler promises that each Pod will consume 50% of the CPU, 1000pps, and 10,000 requests per second:
Looking for a smoother scaling experience? Follow these best practices:
Set CPU Requests for Containers
Adjust HPA target appropriately, aiming for 30% reserve for applications and containers
Maintain robust Pods and Nodes to avoid frequent rebuilding of Pods
Implement user request load balancing
Monitor resource usage with kubectl top node and kubectl top pod
The control manager can be enabled and configured with --horizontal-pod-autoscaler-use-rest-clients and --master or --kubeconfig respectively. Custom metrics API, such as and , should be registered in the API Server Aggregator. For reference, you can check out to develop your custom metrics API server.
For more in-depth understanding on this topic, refer to .