kubernetes: strategic patch: "unrecognized type" error not informative enough

What happened: Given a wrong type, e.g. string where int was expected in a large yaml, oc apply as well as the underlying kubectl patch --type=strategic gives an error that’s hard to act upon (if patch is large).

$ cluster/kubectl.sh patch --type=strategic -p '{"spec": {"replicas": 1}}'  deployment/sise
deployment.extensions/sise patched (no change)
$ cluster/kubectl.sh patch --type=strategic -p '{"spec": {"replicas": "1"}}'  deployment/sise
Error from server: unrecognized type: int32

1. The wording sounds like the problem was an unexpected integer, but actually it means it expected integer but got something else. Worse, there are 2 code paths (FromUnstructured, ToUnstructured) giving exactly same error for different directions!
2. No indication where in the patch the problem was. In above example the patch is tiny but using kubectl apply it’s easy to get lost in a huge patch. apply gives more info, but the error on last line is still same error from patch:

$ oc apply -f deployment.yaml
deployment.apps/sise configured
$ oc apply -f deployment-string.yaml
Error from server: error when applying patch:
{"metadata":{"annotations":{"kubectl.kubernetes.io/last-applied-configuration":"{\"apiVersion\":\"apps/v1\",\"kind\":\"Deployment\",\"metadata\":{\"annotations\":{\"deployment.kubernetes.io/revision\":\"1\"},\"creationTimestamp\":null,\"generation\":1,\"labels\":{\"run\":\"sise\"},\"name\":\"sise\",\"namespace\":\"default\"},\"spec\":{\"replicas\":\"1\",\"selector\":{\"matchLabels\":{\"run\":\"sise\"}},\"strategy\":{\"rollingUpdate\":{\"maxSurge\":1,\"maxUnavailable\":1},\"type\":\"RollingUpdate\"},\"template\":{\"metadata\":{\"creationTimestamp\":null,\"labels\":{\"run\":\"sise\"}},\"spec\":{\"containers\":[{\"image\":\"mhausenblas/simpleservice:0.5.0\",\"imagePullPolicy\":\"IfNotPresent\",\"name\":\"sise\",\"ports\":[{\"containerPort\":9876,\"protocol\":\"TCP\"}],\"resources\":{},\"terminationMessagePath\":\"/dev/termination-log\",\"terminationMessagePolicy\":\"File\"}],\"dnsPolicy\":\"ClusterFirst\",\"restartPolicy\":\"Always\",\"schedulerName\":\"default-scheduler\",\"securityContext\":{},\"terminationGracePeriodSeconds\":30}}}}\n"},"creationTimestamp":null},"spec":{"replicas":"1"}}
to:
Resource: "apps/v1, Resource=deployments", GroupVersionKind: "apps/v1, Kind=Deployment"
Name: "sise", Namespace: "default"
Object: &{map["apiVersion":"apps/v1" "metadata":map["name":"sise" "namespace":"default" "selfLink":"/apis/apps/v1/namespaces/default/deployments/sise" "creationTimestamp":"2019-02-04T10:57:10Z" "annotations":map["deployment.kubernetes.io/revision":"1" "kubectl.kubernetes.io/last-applied-configuration":"{\"apiVersion\":\"apps/v1\",\"kind\":\"Deployment\",\"metadata\":{\"annotations\":{\"deployment.kubernetes.io/revision\":\"1\"},\"creationTimestamp\":null,\"generation\":1,\"labels\":{\"run\":\"sise\"},\"name\":\"sise\",\"namespace\":\"default\"},\"spec\":{\"replicas\":1,\"selector\":{\"matchLabels\":{\"run\":\"sise\"}},\"strategy\":{\"rollingUpdate\":{\"maxSurge\":1,\"maxUnavailable\":1},\"type\":\"RollingUpdate\"},\"template\":{\"metadata\":{\"creationTimestamp\":null,\"labels\":{\"run\":\"sise\"}},\"spec\":{\"containers\":[{\"image\":\"mhausenblas/simpleservice:0.5.0\",\"imagePullPolicy\":\"IfNotPresent\",\"name\":\"sise\",\"ports\":[{\"containerPort\":9876,\"protocol\":\"TCP\"}],\"resources\":{},\"terminationMessagePath\":\"/dev/termination-log\",\"terminationMessagePolicy\":\"File\"}],\"dnsPolicy\":\"ClusterFirst\",\"restartPolicy\":\"Always\",\"schedulerName\":\"default-scheduler\",\"securityContext\":{},\"terminationGracePeriodSeconds\":30}}}}\n"] "uid":"9ee94b73-286b-11e9-9a60-68f728fac3ab" "resourceVersion":"424" "generation":'\x01' "labels":map["run":"sise"]] "spec":map["replicas":'\x01' "selector":map["matchLabels":map["run":"sise"]] "template":map["metadata":map["creationTimestamp":<nil> "labels":map["run":"sise"]] "spec":map["terminationGracePeriodSeconds":'\x1e' "dnsPolicy":"ClusterFirst" "securityContext":map[] "schedulerName":"default-scheduler" "containers":[map["name":"sise" "image":"mhausenblas/simpleservice:0.5.0" "ports":[map["containerPort":'\u2694' "protocol":"TCP"]] "resources":map[] "terminationMessagePath":"/dev/termination-log" "terminationMessagePolicy":"File" "imagePullPolicy":"IfNotPresent"]] "restartPolicy":"Always"]] "strategy":map["type":"RollingUpdate" "rollingUpdate":map["maxUnavailable":'\x01' "maxSurge":'\x01']] "revisionHistoryLimit":'\n' "progressDeadlineSeconds":'\u0258'] "status":map["replicas":'\x01' "updatedReplicas":'\x01' "readyReplicas":'\x01' "availableReplicas":'\x01' "conditions":[map["lastTransitionTime":"2019-02-04T10:57:10Z" "reason":"MinimumReplicasAvailable" "message":"Deployment has minimum availability." "type":"Available" "status":"True" "lastUpdateTime":"2019-02-04T10:57:10Z"] map["type":"Progressing" "status":"True" "lastUpdateTime":"2019-02-04T10:57:12Z" "lastTransitionTime":"2019-02-04T10:57:10Z" "reason":"NewReplicaSetAvailable" "message":"ReplicaSet \"sise-5fc86787d8\" has successfully progressed."]] "observedGeneration":'\x01'] "kind":"Deployment"]}
for: "deployment-string.yaml": unrecognized type: int32

What you expected to happen:

• tell me I gave string “1” but expected an int.
• ideally, tell me problem was in spec.replicas.

How to reproduce it (as minimally and precisely as possible): https://gist.github.com/cben/9bbb982fb8fcf3d88c2c875d04e3a42c

1. kubectl apply -f deployment.yaml
2. kubectl patch --type=strategic -p '{"spec": {"replicas": "1"}}' deployment/sise
3. kubectl apply -f deployment-string.yaml

Anything else we need to know?: Originally I experienced this on OpenShift 3.11, where the UX is even worse: first create/apply is in some cases tolerant and accepts string instead of int (at least for containerPort), while subsequent apply/patch rejects it! But on upstream k8s master I see errors from first create/apply too so not relevant here.

Other patch formats use a different code path, giving a very informative error:

• JSON Merge Patch

  $ cluster/kubectl.sh patch --type=merge -p '{"spec": {"replicas": 1}}'  deployment/sise
  deployment.extensions/sise patched
  $ cluster/kubectl.sh patch --type=merge -p '{"spec": {"replicas": "1"}}'  deployment/sise
  Error from server: v1beta1.Deployment.Spec: v1beta1.DeploymentSpec.Replicas: readUint32: unexpected character: �, error found in #10 byte of ...|eplicas":"1","revisi|..., bigger context ...|"spec":{"progressDeadlineSeconds":600,"replicas":"1","revisionHistoryLimit":10,"selector":{"matchLab|...
  

• JSON Patch

  $ cluster/kubectl.sh patch --type=json -p '[{"op": "replace", "path": "/spec/replicas", "value": 1}]'  deployment/sise
  deployment.extensions/sise patched (no change)
  $ cluster/kubectl.sh patch --type=json -p '[{"op": "replace", "path": "/spec/replicas", "value": "1"}]'  deployment/sise
  Error from server: v1beta1.Deployment.Spec: v1beta1.DeploymentSpec.Replicas: readUint32: unexpected character: �, error found in #10 byte of ...|eplicas":"1","revisi|..., bigger context ...|"spec":{"progressDeadlineSeconds":600,"replicas":"1","revisionHistoryLimit":10,"selector":{"matchLab|...
  

kubectl edit also sometimes shows this error, see https://github.com/kubernetes/kubernetes/issues/26050#issuecomment-460228598

Environment:

• Kubernetes version (use kubectl version): built from master today:

  Client Version: version.Info{Major:"1", Minor:"14+", GitVersion:"v1.14.0-alpha.2.230+cdfb9126d334ee-dirty", GitCommit:"cdfb9126d334eea722e34f3a895904bb152d53f0", GitTreeState:"dirty", BuildDate:"2019-02-04T10:49:37Z", GoVersion:"go1.11.4", Compiler:"gc", Platform:"linux/amd64"}
  Server Version: version.Info{Major:"1", Minor:"14+", GitVersion:"v1.14.0-alpha.2.230+cdfb9126d334ee-dirty", GitCommit:"cdfb9126d334eea722e34f3a895904bb152d53f0", GitTreeState:"dirty", BuildDate:"2019-02-04T10:49:37Z", GoVersion:"go1.11.4", Compiler:"gc", Platform:"linux/amd64"}
  

• Cloud provider or hardware configuration: ThinkPad T450s laptop
• OS (e.g. from /etc/os-release): Fedora 29
• Kernel (e.g. uname -a): Linux 4.19.15-300.fc29.x86_64 #1 SMP Mon Jan 14 16:32:35 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux