Created
August 19, 2024 13:48
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Kubernetes Skew calculator
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| ### This script attempts to calculate the skew of the population of pods across the nodes in a Kubernetes cluster. | |
| ### It takes taints into account, but does not consider pod labels. | |
| NAMESPACE="app" | |
| _all_nodes=$(kubectl get nodes | wc -l) | |
| _all_nodes=$(( _all_nodes - 1 )) | |
| for deployment_name in $(kubectl get -n ${NAMESPACE} deployment --template='{{range.items}}{{.metadata.name}}{{"\n"}}{{end}}'); do | |
| _deployment=$(kubectl get -n app -o json deployment ${deployment_name} | jq -c '.') | |
| _nodeTaintsPolicy=$(echo "${_deployment}" | jq -r '.spec.template.spec.topologySpreadConstraints[0].nodeAffinityPolicy') | |
| if [ "${_nodeTaintsPolicy}" == "Honor" ]; then | |
| _compatible_nodes="" | |
| for deployment_toleration in $(echo "${_deployment}" | jq -c '.spec.template.spec.tolerations[]') | |
| do | |
| _filter="" | |
| _key=$(echo "${deployment_toleration}" | jq -r 'if(.key == null) then empty else .key end') | |
| [ "${_key}" != "" ] && _filter=".key == \"${_key}\" and" | |
| _operator=$(echo "${deployment_toleration}" | jq -r 'if(.operator == null) then empty else .operator end') | |
| if [ "${_operator}" == "Exists" ]; then | |
| _value="" | |
| else | |
| _value=$(echo "${deployment_toleration}" | jq -r 'if(.value == null) then empty else .value end') | |
| fi | |
| [ "${_value}" != "" ] && _filter="${_filter} .value == \"${_value}\" and" | |
| _effect=$(echo "${deployment_toleration}" | jq -r 'if(.effect == null) then empty else .effect end') | |
| [ "${_effect}" != "" ] && _filter="${_filter} .effect == \"${_effect}\" and" | |
| _filter=$(echo "${_filter}" | sed 's/ and$//') | |
| _new_nodes=$(kubectl get nodes -o json | jq -r '.items[] | select(.spec.taints != null) | select(.spec.taints[] | '"${_filter}"') | .metadata.name') | |
| _compatible_nodes=$(echo ${_compatible_nodes}" "${_new_nodes}) | |
| done | |
| _number_of_compatible_nodes=$(echo "${_compatible_nodes}" | sort -u | tr ' ' '\n' | wc -l) | |
| else | |
| _number_of_compatible_nodes=$(kubectl get nodes | wc -l) | |
| fi | |
| _population=$(kubectl get pods -n app -l app.kubernetes.io/name=${deployment_name} --template='{{range .items}}{{.spec.nodeName}}{{"\n"}}{{end}}' | sort | uniq -c | awk '{print $1}' | sort -n) | |
| _population_size=$(echo "${_population}" | wc -l) | |
| _max_population=$(echo "${_population}" | tail -n 1) | |
| _replicas=$(echo "${_deployment}" | jq -r '.spec.replicas') | |
| if [[ "${_replicas}" > "${_all_nodes}" ]] && [[ "${_population_size}" != "${_all_nodes}" ]]; then | |
| _min_population="0" | |
| else | |
| _min_population=$(echo "${_population}" | head -n 1) | |
| fi | |
| _skew="$((_max_population-_min_population))" | |
| echo "${deployment_name} skew: $_skew" | |
| done |
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