kubernetes cluster metrics
- When you run a pod, some load is laid on the node that runs it.
- The pod consume some of the memory and cpu power of that node.
- We'll use a tool called
metrics-server to inspect resources.
- For minikube, the resource-server is available as an
addon.
Here's how to install it (my profile is called five):
1$> kubectl top pods
2error: Metrics API not available
3$> minikube addons -p five enable metrics-server
4💡 metrics-server is an addon maintained by Kubernetes. For any concerns contact minikube on GitHub.
5You can view the list of minikube maintainers at: https://github.com/kubernetes/minikube/blob/master/OWNERS
6 ▪ Using image registry.k8s.io/metrics-server/metrics-server:v0.7.1
7🌟 The 'metrics-server' addon is enabled
8$> kubectl top pods
9error: Metrics API not available
10
11(**STILL GETTING ERRORS BECAUSE IT IS NOT READY**)
12
13$> kubectl top pods
14NAME CPU(cores) MEMORY(bytes)
15envvar-pod 0m 0Mi
16volume-pod 0m 0Mi
17$>
Memory Size Units
- Memory is generally measured in
bytes
- There are Decimal and Binary systems for memory multiple-byte unit.
- For example:
- 103 = 1000 bytes is called kilobyte (short kB)
- 210 = 1024 bytes is called kibibyte (short KiB)
- See a list of these units
here
CPU load Units
- CPU is measure in
CPU resource units
- In Kubernetes, 1 CPU unit is equivalent to 1 physical cpu core, or 1 virtual core, depending on whether the node is a physical host or a virtual machine running inside a physical machine
- Fractional units (so fractions of 1 CPU) are allowed.
- For example, 100m is the same as 0.1, which is 1/10 of a single cpu
- Another example: 0.5m is 5/1000 or 1/2 of a mili-cpu
The top command
- Here's an example:
We are creating a pod, exec into it, them run a script to create some load in this pod.
It may take 2-3 minutes until you'll see this reflected in the metrics:
1$>
2$> kubectl apply -f pod.yaml
3pod/my-pod created
4$> kubectl get pods
5NAME READY STATUS RESTARTS AGE
6my-pod 1/1 Running 0 10s
7$> kubectl exec -it my-pod -- sh
8/ #
9/ # for i in 1 2 3 4; do while : ; do : ; done & done
10/ #
11/ # exit
12$>
13$>
14$> kubectl top pods
15NAME CPU(cores) MEMORY(bytes)
16my-pod 1m 0Mi
17$> kubectl top pods
18NAME CPU(cores) MEMORY(bytes)
19my-pod 1m 0Mi
20$>
21$> kubectl top pods
22NAME CPU(cores) MEMORY(bytes)
23my-pod 3582m 1Mi
24$>
25$> kubectl top pods
26NAME CPU(cores) MEMORY(bytes)
27my-pod 3978m 1Mi
28$> kubectl top pods
29NAME CPU(cores) MEMORY(bytes)
30my-pod 3978m 1Mi
31$>