Kubernetes-client: Yaml containing aliases rejected due to FasterXML bug

[rittneje]

There is a long-standing bug in the way that FasterXML handles yaml containing aliases. https://github.com/FasterXML/jackson-dataformats-text/issues/98

As a consequence, anyone using perfectly valid yaml containing aliases (which may have been automatically generated via SnakeYaml) will get a mysterious error message like this:

15:26:16  hudson.remoting.ProxyException: com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `java.util.LinkedHashMap` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('id001')
15:26:16   at [Source: (BufferedInputStream); line: 49, column: 17] (through reference chain: io.fabric8.kubernetes.api.model.Pod["spec"]->io.fabric8.kubernetes.api.model.PodSpec["containers"]->java.util.ArrayList[1]->io.fabric8.kubernetes.api.model.Container["resources"]->io.fabric8.kubernetes.api.model.ResourceRequirements["requests"])
15:26:16    at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:63)
15:26:16    at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1455)
15:26:16    at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1081)
15:26:16    at com.fasterxml.jackson.databind.deser.ValueInstantiator._createFromStringFallbacks(ValueInstantiator.java:371)
15:26:16    at com.fasterxml.jackson.databind.deser.ValueInstantiator.createFromString(ValueInstantiator.java:258)
15:26:16    at com.fasterxml.jackson.databind.deser.std.MapDeserializer.deserialize(MapDeserializer.java:357)
15:26:16    at com.fasterxml.jackson.databind.deser.std.MapDeserializer.deserialize(MapDeserializer.java:29)
15:26:16    at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:129)
15:26:16    at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:293)
15:26:16    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:156)
15:26:16    at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:129)
15:26:16    at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:293)
15:26:16    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:156)
15:26:16    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:291)
15:26:16    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:250)
15:26:16    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:27)
15:26:16    at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:129)
15:26:16    at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:293)
15:26:16    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:156)
15:26:16    at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:129)
15:26:16    at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:293)
15:26:16    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:156)
15:26:16    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4524)
15:26:16    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3511)
15:26:16    at io.fabric8.kubernetes.client.utils.Serialization.unmarshal(Serialization.java:246)

Is the use of FasterXML strictly required? Would it be possible to simply use SnakeYaml directly for parsing, which seems to handle aliases properly?

[manusa]

I've personally bumped into a few issues when serializing and deserializing content from the client. It seems that YAML produced/serialzied by Jackson can't be deserialized again in some circumstances (another example is deserializing YAMLs double curly brackets >> Helm chart template variables).

This is something we'll need to look into.

[manusa]

Hi @rittneje

Could you provide a sample of the YAML content that's failing for you so we can create specific tests for this issue before we proceed with a fix?

[rittneje]

apiVersion: v1
kind: Pod
spec:
  nodeSelector:
    workload: build
  tolerations:
  - key: nodeType
    operator: Equal
    value: build
    effect: NoSchedule
  securityContext:
    runAsUser: 1000
    runAsGroup: 1000
  containers:
  - name: ubuntu
    image: ubuntu:bionic
    imagePullPolicy: Always
    command:
    - cat
    tty: true
    resources:
      requests: &id001
        cpu: 100m
  - name: python3
    image: python:3.7
    imagePullPolicy: Always
    command:
    - cat
    tty: true
    resources:
      requests: *id001