CHECK_KUBERNETES

Nagios-style checks against Kubernetes API. Designed for usage with Nagios, Icinga, Zabbix... Whatever.

Dependencies

jq
openssl

Script usage

Usage ./check_kubernetes.sh [-m <MODE>|-h] [-o <TIMEOUT>] [-H <APISERVER> [-T <TOKEN>|-t <TOKENFILE>]] [-K <KUBE_CONFIG>]
         [-N <NAMESPACE>] [-n <NAME>] [-w <WARN>] [-c <CRIT>]

Options are:
  -m MODE          Which check to perform
  -H APISERVER     API URL to query, kubectl is used if this option is not set
  -T TOKEN         Authorization token for API
  -t TOKENFILE     Path to file with token in it
  -K KUBE_CONFIG   Path to kube-config file for kubectl utility
  -N NAMESPACE     Optional namespace for some modes. By default all namespaces will be used
  -n NAME          Optional deployment name or pod app label depending on the mode being used. By default all objects will be checked
  -o TIMEOUT       Timeout in seconds; default is 15
  -w WARN          Warning threshold for TLS expiration days and for pod restart count (in pods mode); default is 30 for both days and restart count
-c CRIT          Critical threshold for pod restart count (in pods mode); default is 150
-b               Brief mode (more suitable for Zabbix)
  -h               Show this help and exit

Modes are:
  apiserver        Not for kubectl, should be used for each apiserver independently
  components       Check for health of k8s components (etcd, controller-manager, scheduler etc.)
  nodes            Check for active nodes
  pods             Check for restart count of containters in the pods
  deployments      Check for deployments availability
  daemonsets       Check for daemonsets readiness
  replicasets      Check for replicasets readiness
  statefulsets     Check for statefulsets readiness
  tls              Check for tls secrets expiration dates

Examples:

Check apiserver health using tokenfile:

./check_kubernetes.sh -m apiserver -H https://<...>:6443 -t /path/to/tokenfile
OK. Kuberenetes apiserver health is OK

Check whether all deployments are available using token:

./check_kubernetes.sh -m deployments -H https://<...>:6443 -T eYN6...
OK. 27 deploymens are available

Check one definite deployment using kubectl:

./check_kubernetes.sh -m deployments -H https://<...>:6443 -K /path/to/kube_config -N ingress-nginx -n nginx-ingress-controller
OK. Deployment available

Check nodes using kubectl with default kube config:

./check_kubernetes.sh -m nodes -H https://<...>:6443
OK. 4 nodes are Ready

Check pods (by the restarts count):

./check_kubernetes.sh -m pods -H https://<...>:6443 -N kube-system -w 5
WARNING. Container kube-system/calico-node-5kc4n/calico-node: 6 restarts. 22 pods ready, 0 pods not ready

Check daemonstets (compare number of desired and number of ready pods):

./check_kubernetes.sh -m daemonsets -K ~/.kube/cluster -N monitoring
OK. Daemonset monitoring/node-exporter 5/5 ready

Check replicasets (compare number of desired and number of ready pods):

./check_kubernetes.sh -m replicasets -K ~/.kube/cluster -N monitoring
OK. Replicaset monitoring/node-exporter 5/5 ready

Check statefulsets (compare number of desired and number of ready pods):

./check_kubernetes.sh -m statefulsets -K ~/.kube/cluster -N monitoring
OK. Statefulset monitoring/node-exporter 5/5 ready

Check TLS certs:

./check_kubernetes.sh -m tls -H https://<...>:6443 -T $TOKEN -N kube-system
kube-system/k8s-local-cert is about to expire in 18 days

Brief mode

All modes support the -b brief option. In this mode, a single numerical output is returned. The number is positive on success and zero or negative on error.

For boolean checks, 1 is returned on success and 0 on error.

For numerical checks, the number is returned on success and zero or a negative number on error. For example, when used with pods, the number of pods is returned, but minus the number of restarts if it exceeds the warning threshold (so if 3 pods are ok and 1 failed, 3 is returned, but if 4 pods are ok with none failed but 157 restarts with default settings, -157 is returned). Sometimes positivity suffices, sometimes you need to monitor the exact number.

ServiceAccount and token

All the needed objects (ServiceAccount, ClusterRole, RoleBinding) can be created with this command:

kubectl apply -f https://raw.githubusercontent.com/agapoff/check_kubernetes/master/account.yaml

You may also prefer to revise and tighten the RBAC role if you're not going to use all modes. For example you may get rid of secrets permission if you have no need to check the TLS certs.

Then in order to get the token just issue this command:

kubectl -n monitoring get secret "$(kubectl -n monitoring get serviceaccount monitoring -o 'jsonpath={.secrets[0].name}')" -o "jsonpath={.data.token}" | openssl enc -d -base64 -A

Example configuration for Icinga

Command:

object CheckCommand "check-kubernetes" {
  import "plugin-check-command"

  command = [ PluginDir + "/check_kubernetes.sh" ]

  arguments = {
                "-H" = "$kube_scheme$://$host.address$:$kube_port$"
                "-m" = "$kube_mode$"
                "-o" = "$kube_timeout$"
                "-T" = "$kube_pass$"
                "-t" = "$kube_tokenfile$"
                "-K" = "$kube_config$"
                "-N" = "$kube_ns$"
                "-n" = "$kube_name$"
                "-w" = "$kube_warn$"
                "-c" = "$kube_crit$"
  }
}

Services:

apply Service "k8s apiserver health" {
  import "generic-service"
  check_command = "check-kubernetes"
  vars.kube_mode = "apiserver"
  assign where "k8s-master" in host.vars.roles
}

apply Service "k8s components health" {
  import "generic-service"
  check_command = "check-kubernetes"
  vars.kube_mode = "components"
  assign where "k8s-api" in host.vars.roles
}

apply Service "k8s nodes" {
  import "generic-service"
  check_command = "check-kubernetes"
  vars.kube_mode = "nodes"
  assign where "k8s-api" in host.vars.roles
}

apply Service "k8s deployments" {
  import "generic-service"
  check_command = "check-kubernetes"
  vars.kube_mode = "deployments"
  assign where "k8s-api" in host.vars.roles
}

apply Service "k8s daemonsets" {
  import "generic-service"
  check_command = "check-kubernetes"
  vars.kube_mode = "daemonsets"
  assign where "k8s-api" in host.vars.roles
}

apply Service "k8s replicasets" {
  import "generic-service"
  check_command = "check-kubernetes"
  vars.kube_mode = "replicasets"
  assign where "k8s-api" in host.vars.roles
}

apply Service "k8s TLS certs" {
  import "generic-service"
  check_command = "check-kubernetes"
  vars.kube_mode = "tls"
  assign where "k8s-api" in host.vars.roles
}

apply Service "k8s pods" {
  import "generic-service"
  check_command = "check-kubernetes"
  vars.kube_mode = "pods"
  assign where "k8s-api" in host.vars.roles
}

apply Service "k8s ingress controller" {
  import "generic-service"
  check_command = "check-kubernetes"
  vars.kube_mode = "deployments"
  vars.kube_ns = "ingress-nginx"
  vars.kube_name = "nginx-ingress-controller"
  assign where "k8s-api" in host.vars.roles
}

Host template:

template Host "k8s-host" {
  import "generic-host"

  vars.kube_pass = "..."
  vars.kube_scheme = "https"
  vars.kube_port = 6443
}

Hosts:

# VIP address of the API     
object Host "k8s-api" {
  import "k8s-host"
  address = "<...>"
  vars.roles = [ "k8s-api" ]
}

object Host "k8s-master1" {
  import "linux-host"
  import "k8s-host"
  address = "<...>"
  vars.roles = [ "k8s-master" ]
}

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