Kubernetes/Monitoring
Monitor cluster resources
Metric-server
In order to get cluster resources you need a metric collector plugin. Popular one is heapster that exposes metric-server service. The below commands relay on its API to get data:
Install metrics-server
git clone https://github.com/kubernetes-incubator/metrics-server.git kubectl apply -f ~/metrics-server/deploy/1.8+/
Get metrics
# verify metrics server API kubectl get --raw /apis/metrics.k8s.io/ kubectl top node # CPU,memory utilization of the nodes in your cluster kubectl top pods # CPU,memory utilization of the pods in your cluster kubectl top pods -A # CPU,memory of pods in all namespaces kubectl top pod -l run=<label> # CPU and memory of pods with a label selector: kubectl top pod <pod-name> # CPU,memory of a specific pod kubectl top pods group-context --containers # CPU,memory of the containers inside the pod
cAdvisor deprecated in v1.11
Every node in a Kubernetes cluster has a Kubelet process. Within each Kubelet is a cAdvisor process. The cAdvisor is continuously gathering metrics about the state of the cluster. It's always available
minikube start --extra-config=kubelet.CAdvisorPort=4194 kubectl proxy & # open a proxy to the Kubernetes API port open $(minikube ip):4194 # cAdvisor also serves up the metrics is a helpful HTML format # Each node provide statistics that are provided by cAdvisor. Access the node stats curl localhost:8001/api/v1/nodes/$(kubectl get nodes -o=jsonpath="{.items[0].metadata.name}")/proxy/stats/ # Kubernetes API also gather the cAdvisor metrics at /metrics curl localhost:8001/metrics
Liveness and Readiness probes
Check this Visual explanation
Get service endpoints. Only healthy and ready pods will be added to the endpoint
kubectl get endpoint
Liveness and rediness probes in both Pod and Deployment manifests are at .spec.containers.image
level
apiVersion: v1 kind: Pod metadata: name: liveness-readiness-pod spec: containers: - image: nginx name: main livenessProbe: httpGet: path: /healthz # not all containers have this endpoint port: 8081 readinessProbe: httpGet: path: / port: 80
Logs
Container logs
Containerized applications usually write their logs to STDOUT and STDERR instead of writing their logs to files. Docker then redirects those streams to files. You can retrieve those files with the kubectl logs
These are stored on nodes in /var/log/
directory and contain everything containers send to STDOUT.
/var/log/containers/
contains container logs, these are symlinks to../pods/
/var/log/containers/
contains directory per each pod in form<namespace-<rs|deployment>/<pod-name>/0.log(logfile)
0.log
it's a symlink to/var/lib/docker/containers/uid-part1/uid-part2-json.log
$ ls -l /var/log/containers total 56 lrwxrwxrwx 1 root root 101 Oct 7 06:51 coredns-5644d7b6d9-hztth_kube-system_coredns-9de9395495186177f5112d795ca950dd0227e6f025f40c83ddf2a99c56802939.log -> /var/log/pods/kube-system_coredns-5644d7b6d9-hztth_5da159b3-64e7-48e4-b9f8-003f9623481d/coredns/0.log ...
In case your container logs multiple files, it will be difficult to distinguish them using kubectl logs
command. Therefore you can introduce sidecars containers that tail individual logs and access them like that:
kubectl logs <pod> container-log-1
kubectl logs <pod> container-log-2
kubelet
runs as a process therefore writes logs to system location
/var/log
journalctl -u kubelet.service
</source>
Retrieve logs
kubectl logs <pod> <container> # container name is optional for a single container pods kubectl logs <pod> <container> --previous | -p flag # in case the container has crashed kubectl logs <pod> --all-containers=true kubectl logs --since=10m <pod> kubectl logs deployment/<pod> -c <container> # view the logs from a container within a pod within a deployment kubectl logs --tail=20 haproxy # tail x lines kubectl logs -l app=haproxy # logs from containers matching a label
Termination message
WKubernetes allows to write a custom message to a custom file on termination. This message can be view directly using kubectl describe
in Last State: Termination, Message: <custom message>
apiVersion: v1 kind: Pod metadata: name: pod2 spec: containers: - image: busybox name: main command: - sh - -c - 'echo "I say that this container has been terminated at $(date)" > /var/termination-reason ; exit 1' terminationMessagePath: /var/termination-reason
Troubelshooting
# get a yaml without status information (almost clean yaml manifest) kubectl -n web pod <failing-pod> -oyaml --export
References
- debug-application K8s docs
- Logging K8s docs
- Logs K8s docs