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kubectl-fields

Kubectl resources hierarchy parsing tool

Kubectl-fields is a cli tool to parse kubectl explain --recursive output to match given field and print its parental hierarchy in one-liner format.

Installation

Installing with krew

kubectl krew install fields

Installing with wget

wget https://github.com/rewanthtammana/kubectl-fields/releases/download/v1.2.0-beta/kubectl-fields-Linux-x86_64.tar.gz
sudo tar xvf kubectl-fields-Linux-x86_64.tar.gz -C /usr/bin/

Developer build

Build from Makefile

make build

Build only for Linux

make build-linux

Build with go

go get ./...
go build -o kubectl-fields main.go
mv kubectl-fields /usr/bin

Cross platform builds with go

go get ./...
GOOS=windows GOARCH=amd64 go build -o kubectl-fields.exe main.go

Usage

rewanth@ubuntu:~/go/src/kubectl-fields$ kubectl fields -h
kubectl-fields parses specified kubectl resources to match given pattern(s).
It prints matched fields parental hierarchy in one-liner format.

More info: https://github.com/rewanthtammana/kubectl-fields

Usage:
  kubectl-fields [flags]

Examples:
Find resource field hierarchy:
$ kubectl fields svc affinity
spec.sessionAffinity
spec.sessionAffinityConfig

Find resource field hierarchy (case sensitive match):
$ kubectl fields po.spec.volumes -I Ver
downwardAPI.items.fieldRef.apiVersion
projected.sources.downwardAPI.items.fieldRef.apiVersion

Flags:
  -I, --case-sensitive   Case sensitive pattern match
  -h, --help             help for kubectl-fields
      --no-color         Do not print colored output
      --stdin            Expects input via pipes

Examples

Default match

default-match

Case sensitive match

case-sensitive-match

Multi pattern match

combo

Output on windows cmd

windows-all

Pipeline

This application uses drone CI for building and running all test cases.

All the test cases are associated with kubectl. But as of now we cannot run kubectl inside containers. As a way around, all the kubectl data required for running test cases is pre-saved into text files. All the test cases are executed from pre-saved data against fresh built binary executable to check its robustness.

Why to use

CKA and CKAD are time-constrained exams. The default kubectl explain recursive command consumes lot of time to find the exact hierarchical order. This tool is built to ease the process of finding hierarchial structure for a given parameter.

It is difficult to lookup for exact hierarchical structure using kubectl explain recursive command. This tool solves this particular problem by printing the output in a easy readable one-liner format.

This tool has tremendous advantage over grep for this use case.

Problem statement

For ex, in CKA/CKAD exam you are asked to add SYS_ADMIN capabilities to a given pod. Finding the exact hierarchial order using kubectl explain command is time consuming and tiresome.

Current solution approach

Let's say you know that capabilities exist inside po.spec. You can apply recursive loop directly on po.spec instead of running it globally on po.

You can try to grep for string, "capabilities". The output is as follows:

rewanth@ubuntu:~/go/src/kubectl-fields$ kubectl explain --recursive po.spec | grep capabilities
         capabilities   <Object>
         capabilities   <Object>

In case if you need to find "version" attribute in services, then the below command is executed.

$ kubectl explain --recursive svc | grep -i version
VERSION:  v1
   apiVersion	<string>
            apiVersion	<string>
               resourceVersion	<string>
         apiVersion	<string>
         apiVersion	<string>
      resourceVersion	<string>

But it doesn't show the hierarchial order of attribute. It just shows the matching lines. You can use advanced grep functions and try to find the parent hierarchy of capabilities attribute.

rewanth@ubuntu:~/go/src/kubectl-fields$ kubectl explain --recursive po.spec | grep capabilities -C 5
      resources <Object>
         limits <map[string]string>
         requests       <map[string]string>
      securityContext   <Object>
         allowPrivilegeEscalation       <boolean>
         capabilities   <Object>
            add <[]string>
            drop        <[]string>
         privileged     <boolean>
         procMount      <string>
         readOnlyRootFilesystem <boolean>
--
      resources <Object>
         limits <map[string]string>
         requests       <map[string]string>
      securityContext   <Object>
         allowPrivilegeEscalation       <boolean>
         capabilities   <Object>
            add <[]string>
            drop        <[]string>
         privileged     <boolean>
         procMount      <string>
         readOnlyRootFilesystem <boolean>

But still it doesn't show the complete parent hierarchy order. The full list need to be printed, scrolled and analyzed to find the exact hierarchical structure.

Not only it will take so much time to scroll up and down to find parent of an element in terminal, the process is very tedious.

kubectl explain --recursive po.spec (click to expand 624 lines output) 
rewanth@ubuntu:~/go/src/kubectl-fields$ kubectl explain --recursive po.spec
KIND:     Pod
VERSION:  v1

RESOURCE: spec <Object>

DESCRIPTION:
     Specification of the desired behavior of the pod. More info:
     https://git.k8s.io/community/contributors/devel/api-conventions.md#spec-and-status

     PodSpec is a description of a pod.

FIELDS:
   activeDeadlineSeconds	<integer>
   affinity	<Object>
      nodeAffinity	<Object>
         preferredDuringSchedulingIgnoredDuringExecution	<[]Object>
            preference	<Object>
               matchExpressions	<[]Object>
                  key	<string>
                  operator	<string>
                  values	<[]string>
               matchFields	<[]Object>
                  key	<string>
                  operator	<string>
                  values	<[]string>
            weight	<integer>
         requiredDuringSchedulingIgnoredDuringExecution	<Object>
            nodeSelectorTerms	<[]Object>
               matchExpressions	<[]Object>
                  key	<string>
                  operator	<string>
                  values	<[]string>
               matchFields	<[]Object>
                  key	<string>
                  operator	<string>
                  values	<[]string>
      podAffinity	<Object>
         preferredDuringSchedulingIgnoredDuringExecution	<[]Object>
            podAffinityTerm	<Object>
               labelSelector	<Object>
                  matchExpressions	<[]Object>
                     key	<string>
                     operator	<string>
                     values	<[]string>
                  matchLabels	<map[string]string>
               namespaces	<[]string>
               topologyKey	<string>
            weight	<integer>
         requiredDuringSchedulingIgnoredDuringExecution	<[]Object>
            labelSelector	<Object>
               matchExpressions	<[]Object>
                  key	<string>
                  operator	<string>
                  values	<[]string>
               matchLabels	<map[string]string>
            namespaces	<[]string>
            topologyKey	<string>
      podAntiAffinity	<Object>
         preferredDuringSchedulingIgnoredDuringExecution	<[]Object>
            podAffinityTerm	<Object>
               labelSelector	<Object>
                  matchExpressions	<[]Object>
                     key	<string>
                     operator	<string>
                     values	<[]string>
                  matchLabels	<map[string]string>
               namespaces	<[]string>
               topologyKey	<string>
            weight	<integer>
         requiredDuringSchedulingIgnoredDuringExecution	<[]Object>
            labelSelector	<Object>
               matchExpressions	<[]Object>
                  key	<string>
                  operator	<string>
                  values	<[]string>
               matchLabels	<map[string]string>
            namespaces	<[]string>
            topologyKey	<string>
   automountServiceAccountToken	<boolean>
   containers	<[]Object>
      args	<[]string>
      command	<[]string>
      env	<[]Object>
         name	<string>
         value	<string>
         valueFrom	<Object>
            configMapKeyRef	<Object>
               key	<string>
               name	<string>
               optional	<boolean>
            fieldRef	<Object>
               apiVersion	<string>
               fieldPath	<string>
            resourceFieldRef	<Object>
               containerName	<string>
               divisor	<string>
               resource	<string>
            secretKeyRef	<Object>
               key	<string>
               name	<string>
               optional	<boolean>
      envFrom	<[]Object>
         configMapRef	<Object>
            name	<string>
            optional	<boolean>
         prefix	<string>
         secretRef	<Object>
            name	<string>
            optional	<boolean>
      image	<string>
      imagePullPolicy	<string>
      lifecycle	<Object>
         postStart	<Object>
            exec	<Object>
               command	<[]string>
            httpGet	<Object>
               host	<string>
               httpHeaders	<[]Object>
                  name	<string>
                  value	<string>
               path	<string>
               port	<string>
               scheme	<string>
            tcpSocket	<Object>
               host	<string>
               port	<string>
         preStop	<Object>
            exec	<Object>
               command	<[]string>
            httpGet	<Object>
               host	<string>
               httpHeaders	<[]Object>
                  name	<string>
                  value	<string>
               path	<string>
               port	<string>
               scheme	<string>
            tcpSocket	<Object>
               host	<string>
               port	<string>
      livenessProbe	<Object>
         exec	<Object>
            command	<[]string>
         failureThreshold	<integer>
         httpGet	<Object>
            host	<string>
            httpHeaders	<[]Object>
               name	<string>
               value	<string>
            path	<string>
            port	<string>
            scheme	<string>
         initialDelaySeconds	<integer>
         periodSeconds	<integer>
         successThreshold	<integer>
         tcpSocket	<Object>
            host	<string>
            port	<string>
         timeoutSeconds	<integer>
      name	<string>
      ports	<[]Object>
         containerPort	<integer>
         hostIP	<string>
         hostPort	<integer>
         name	<string>
         protocol	<string>
      readinessProbe	<Object>
         exec	<Object>
            command	<[]string>
         failureThreshold	<integer>
         httpGet	<Object>
            host	<string>
            httpHeaders	<[]Object>
               name	<string>
               value	<string>
            path	<string>
            port	<string>
            scheme	<string>
         initialDelaySeconds	<integer>
         periodSeconds	<integer>
         successThreshold	<integer>
         tcpSocket	<Object>
            host	<string>
            port	<string>
         timeoutSeconds	<integer>
      resources	<Object>
         limits	<map[string]string>
         requests	<map[string]string>
      securityContext	<Object>
         allowPrivilegeEscalation	<boolean>
         capabilities	<Object>
            add	<[]string>
            drop	<[]string>
         privileged	<boolean>
         procMount	<string>
         readOnlyRootFilesystem	<boolean>
         runAsGroup	<integer>
         runAsNonRoot	<boolean>
         runAsUser	<integer>
         seLinuxOptions	<Object>
            level	<string>
            role	<string>
            type	<string>
            user	<string>
         windowsOptions	<Object>
            gmsaCredentialSpec	<string>
            gmsaCredentialSpecName	<string>
      stdin	<boolean>
      stdinOnce	<boolean>
      terminationMessagePath	<string>
      terminationMessagePolicy	<string>
      tty	<boolean>
      volumeDevices	<[]Object>
         devicePath	<string>
         name	<string>
      volumeMounts	<[]Object>
         mountPath	<string>
         mountPropagation	<string>
         name	<string>
         readOnly	<boolean>
         subPath	<string>
         subPathExpr	<string>
      workingDir	<string>
   dnsConfig	<Object>
      nameservers	<[]string>
      options	<[]Object>
         name	<string>
         value	<string>
      searches	<[]string>
   dnsPolicy	<string>
   enableServiceLinks	<boolean>
   hostAliases	<[]Object>
      hostnames	<[]string>
      ip	<string>
   hostIPC	<boolean>
   hostNetwork	<boolean>
   hostPID	<boolean>
   hostname	<string>
   imagePullSecrets	<[]Object>
      name	<string>
   initContainers	<[]Object>
      args	<[]string>
      command	<[]string>
      env	<[]Object>
         name	<string>
         value	<string>
         valueFrom	<Object>
            configMapKeyRef	<Object>
               key	<string>
               name	<string>
               optional	<boolean>
            fieldRef	<Object>
               apiVersion	<string>
               fieldPath	<string>
            resourceFieldRef	<Object>
               containerName	<string>
               divisor	<string>
               resource	<string>
            secretKeyRef	<Object>
               key	<string>
               name	<string>
               optional	<boolean>
      envFrom	<[]Object>
         configMapRef	<Object>
            name	<string>
            optional	<boolean>
         prefix	<string>
         secretRef	<Object>
            name	<string>
            optional	<boolean>
      image	<string>
      imagePullPolicy	<string>
      lifecycle	<Object>
         postStart	<Object>
            exec	<Object>
               command	<[]string>
            httpGet	<Object>
               host	<string>
               httpHeaders	<[]Object>
                  name	<string>
                  value	<string>
               path	<string>
               port	<string>
               scheme	<string>
            tcpSocket	<Object>
               host	<string>
               port	<string>
         preStop	<Object>
            exec	<Object>
               command	<[]string>
            httpGet	<Object>
               host	<string>
               httpHeaders	<[]Object>
                  name	<string>
                  value	<string>
               path	<string>
               port	<string>
               scheme	<string>
            tcpSocket	<Object>
               host	<string>
               port	<string>
      livenessProbe	<Object>
         exec	<Object>
            command	<[]string>
         failureThreshold	<integer>
         httpGet	<Object>
            host	<string>
            httpHeaders	<[]Object>
               name	<string>
               value	<string>
            path	<string>
            port	<string>
            scheme	<string>
         initialDelaySeconds	<integer>
         periodSeconds	<integer>
         successThreshold	<integer>
         tcpSocket	<Object>
            host	<string>
            port	<string>
         timeoutSeconds	<integer>
      name	<string>
      ports	<[]Object>
         containerPort	<integer>
         hostIP	<string>
         hostPort	<integer>
         name	<string>
         protocol	<string>
      readinessProbe	<Object>
         exec	<Object>
            command	<[]string>
         failureThreshold	<integer>
         httpGet	<Object>
            host	<string>
            httpHeaders	<[]Object>
               name	<string>
               value	<string>
            path	<string>
            port	<string>
            scheme	<string>
         initialDelaySeconds	<integer>
         periodSeconds	<integer>
         successThreshold	<integer>
         tcpSocket	<Object>
            host	<string>
            port	<string>
         timeoutSeconds	<integer>
      resources	<Object>
         limits	<map[string]string>
         requests	<map[string]string>
      securityContext	<Object>
         allowPrivilegeEscalation	<boolean>
         capabilities	<Object>
            add	<[]string>
            drop	<[]string>
         privileged	<boolean>
         procMount	<string>
         readOnlyRootFilesystem	<boolean>
         runAsGroup	<integer>
         runAsNonRoot	<boolean>
         runAsUser	<integer>
         seLinuxOptions	<Object>
            level	<string>
            role	<string>
            type	<string>
            user	<string>
         windowsOptions	<Object>
            gmsaCredentialSpec	<string>
            gmsaCredentialSpecName	<string>
      stdin	<boolean>
      stdinOnce	<boolean>
      terminationMessagePath	<string>
      terminationMessagePolicy	<string>
      tty	<boolean>
      volumeDevices	<[]Object>
         devicePath	<string>
         name	<string>
      volumeMounts	<[]Object>
         mountPath	<string>
         mountPropagation	<string>
         name	<string>
         readOnly	<boolean>
         subPath	<string>
         subPathExpr	<string>
      workingDir	<string>
   nodeName	<string>
   nodeSelector	<map[string]string>
   preemptionPolicy	<string>
   priority	<integer>
   priorityClassName	<string>
   readinessGates	<[]Object>
      conditionType	<string>
   restartPolicy	<string>
   runtimeClassName	<string>
   schedulerName	<string>
   securityContext	<Object>
      fsGroup	<integer>
      runAsGroup	<integer>
      runAsNonRoot	<boolean>
      runAsUser	<integer>
      seLinuxOptions	<Object>
         level	<string>
         role	<string>
         type	<string>
         user	<string>
      supplementalGroups	<[]integer>
      sysctls	<[]Object>
         name	<string>
         value	<string>
      windowsOptions	<Object>
         gmsaCredentialSpec	<string>
         gmsaCredentialSpecName	<string>
   serviceAccount	<string>
   serviceAccountName	<string>
   shareProcessNamespace	<boolean>
   subdomain	<string>
   terminationGracePeriodSeconds	<integer>
   tolerations	<[]Object>
      effect	<string>
      key	<string>
      operator	<string>
      tolerationSeconds	<integer>
      value	<string>
   volumes	<[]Object>
      awsElasticBlockStore	<Object>
         fsType	<string>
         partition	<integer>
         readOnly	<boolean>
         volumeID	<string>
      azureDisk	<Object>
         cachingMode	<string>
         diskName	<string>
         diskURI	<string>
         fsType	<string>
         kind	<string>
         readOnly	<boolean>
      azureFile	<Object>
         readOnly	<boolean>
         secretName	<string>
         shareName	<string>
      cephfs	<Object>
         monitors	<[]string>
         path	<string>
         readOnly	<boolean>
         secretFile	<string>
         secretRef	<Object>
            name	<string>
         user	<string>
      cinder	<Object>
         fsType	<string>
         readOnly	<boolean>
         secretRef	<Object>
            name	<string>
         volumeID	<string>
      configMap	<Object>
         defaultMode	<integer>
         items	<[]Object>
            key	<string>
            mode	<integer>
            path	<string>
         name	<string>
         optional	<boolean>
      csi	<Object>
         driver	<string>
         fsType	<string>
         nodePublishSecretRef	<Object>
            name	<string>
         readOnly	<boolean>
         volumeAttributes	<map[string]string>
      downwardAPI	<Object>
         defaultMode	<integer>
         items	<[]Object>
            fieldRef	<Object>
               apiVersion	<string>
               fieldPath	<string>
            mode	<integer>
            path	<string>
            resourceFieldRef	<Object>
               containerName	<string>
               divisor	<string>
               resource	<string>
      emptyDir	<Object>
         medium	<string>
         sizeLimit	<string>
      fc	<Object>
         fsType	<string>
         lun	<integer>
         readOnly	<boolean>
         targetWWNs	<[]string>
         wwids	<[]string>
      flexVolume	<Object>
         driver	<string>
         fsType	<string>
         options	<map[string]string>
         readOnly	<boolean>
         secretRef	<Object>
            name	<string>
      flocker	<Object>
         datasetName	<string>
         datasetUUID	<string>
      gcePersistentDisk	<Object>
         fsType	<string>
         partition	<integer>
         pdName	<string>
         readOnly	<boolean>
      gitRepo	<Object>
         directory	<string>
         repository	<string>
         revision	<string>
      glusterfs	<Object>
         endpoints	<string>
         path	<string>
         readOnly	<boolean>
      hostPath	<Object>
         path	<string>
         type	<string>
      iscsi	<Object>
         chapAuthDiscovery	<boolean>
         chapAuthSession	<boolean>
         fsType	<string>
         initiatorName	<string>
         iqn	<string>
         iscsiInterface	<string>
         lun	<integer>
         portals	<[]string>
         readOnly	<boolean>
         secretRef	<Object>
            name	<string>
         targetPortal	<string>
      name	<string>
      nfs	<Object>
         path	<string>
         readOnly	<boolean>
         server	<string>
      persistentVolumeClaim	<Object>
         claimName	<string>
         readOnly	<boolean>
      photonPersistentDisk	<Object>
         fsType	<string>
         pdID	<string>
      portworxVolume	<Object>
         fsType	<string>
         readOnly	<boolean>
         volumeID	<string>
      projected	<Object>
         defaultMode	<integer>
         sources	<[]Object>
            configMap	<Object>
               items	<[]Object>
                  key	<string>
                  mode	<integer>
                  path	<string>
               name	<string>
               optional	<boolean>
            downwardAPI	<Object>
               items	<[]Object>
                  fieldRef	<Object>
                     apiVersion	<string>
                     fieldPath	<string>
                  mode	<integer>
                  path	<string>
                  resourceFieldRef	<Object>
                     containerName	<string>
                     divisor	<string>
                     resource	<string>
            secret	<Object>
               items	<[]Object>
                  key	<string>
                  mode	<integer>
                  path	<string>
               name	<string>
               optional	<boolean>
            serviceAccountToken	<Object>
               audience	<string>
               expirationSeconds	<integer>
               path	<string>
      quobyte	<Object>
         group	<string>
         readOnly	<boolean>
         registry	<string>
         tenant	<string>
         user	<string>
         volume	<string>
      rbd	<Object>
         fsType	<string>
         image	<string>
         keyring	<string>
         monitors	<[]string>
         pool	<string>
         readOnly	<boolean>
         secretRef	<Object>
            name	<string>
         user	<string>
      scaleIO	<Object>
         fsType	<string>
         gateway	<string>
         protectionDomain	<string>
         readOnly	<boolean>
         secretRef	<Object>
            name	<string>
         sslEnabled	<boolean>
         storageMode	<string>
         storagePool	<string>
         system	<string>
         volumeName	<string>
      secret	<Object>
         defaultMode	<integer>
         items	<[]Object>
            key	<string>
            mode	<integer>
            path	<string>
         optional	<boolean>
         secretName	<string>
      storageos	<Object>
         fsType	<string>
         readOnly	<boolean>
         secretRef	<Object>
            name	<string>
         volumeName	<string>
         volumeNamespace	<string>
      vsphereVolume	<Object>
         fsType	<string>
         storagePolicyID	<string>
         storagePolicyName	<string>
         volumePath	<string>

Proposed solution approach

kubectl-fields is the solution. This tool fixes the problem by parsing the kubectl explain --recursive output and returns a one-liner hierarchial structure instead of tree type hierarchy. This makes it easier for developers/users to analyze the resources hierarchy.

To find capabilities order in po.spec resources, the following command can be executed.

rewanth@ubuntu:~/go/src/kubectl-fields$ kubectl fields po.spec capabilities
containers.securityContext.capabilities
initContainers.securityContext.capabilities

Similarly to find "version" attribute structure in services resource, the below command can be executed.

rewanth@ubuntu:~/go/src/kubectl-fields$ kubectl fields svc -i version
apiVersion
metadata.initializers.result.apiVersion
metadata.initializers.result.metadata.resourceVersion
metadata.managedFields.apiVersion
metadata.ownerReferences.apiVersion
metadata.resourceVersion

Author

Rewanth Cool

Todo

  • Document the basic usage for README
  • Build pipeline to run testcases
  • Release the tool as krew package
  • Write documentation according to godoc standards
  • Release the tool as golang package
  • Release the tool as a debian package

Contribution and support

Ways to contribute

  • Suggest a feature
  • Report a bug
  • Fix something and open a pull request
  • Fix documentation
  • Spread the word
  • Like this tool? Star and fork