K
Q

mapping values are not allowed in this context

6/2/2017

I'm a novice regarding YAML format and kubernetes.

The following is a dep_prom.yml file.

---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  labels:
    name: prometheus-deployment
  name: prometheus
  #namespace: prometheus
spec:
  replicas: 1
  template:
    metadata:
      labels:
        app: prometheus
    spec:
      containers:
      - image: prom/prometheus:master
        name: prometheus
        command:
        - "/bin/prometheus"
        args:
        - "-config.file=/etc/prometheus/prometheus.yml"
        - "-storage.local.path=/prometheus"
        - "-storage.local.retention=24h"
        ports:
        - containerPort: 9090
          protocol: TCP
        volumeMounts:
        - mountPath: "/prometheus"
          name: data
        - mountPath: "/etc/prometheus"
          name: config-volume
        resources:
          requests:
            cpu: 100m
            memory: 100Mi
          limits:
            cpu: 500m
            memory: 2500Mi
      volumes:
      - name: data
        hostPath:
          path: /data/prometheus
      - name: config-volume
        configMap:
          name: prometheus
      nodeSelector: westporch-kubeminion-1
        kubernetes.io/hostname: 10.0.24.52
---

However... When I executed kubectl create -f dep_prom.yml

error: error converting YAML to JSON: yaml: line 47: mapping values are not allowed in this context

Line 47 is nodeSelector: westporch-kubeminion-1

I think that YAML file format is normal.

What is causing this error?

-- Westporch
kubectl
kubernetes
yaml

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4 Answers

6/2/2017

As mentioned, nodeSelector cannot have a value like that. It is to specify a map of key-value pairs. You can read more about the specific usage here. For instance, a proper usage of nodeSelector might be:

    nodeSelector:
       disktype: ssd
-- jzeef
Source: StackOverflow
11/3/2018

You indicate you think the YAML format is normal, but it is not. This is a YAML error caused by the line at the end of the first document, starting with kubernetes.io/hostname being indented relative to the one before it. Because these are both key-value pair lines (i.e. item pairs of a block-style mapping) instead of

      nodeSelector: westporch-kubeminion-1
        kubernetes.io/hostname: 10.0.24.52

you either need to do:

      nodeSelector: westporch-kubeminion-1
      kubernetes.io/hostname: 10.0.24.52

but it might be that nodeSelector needs a mapping as argument instead of the scalar westporch-kubeminion-1 it has now.

      nodeSelector:
        kubernetes.io/hostname: 10.0.24.52

This error might mask a second one in the file, depending on how lenient kubernetes is. The --- is the end-of-directives marker and since the directives are optional it can occur at the start of a YAML document. The one at the bottom of your example indicates the start of a new document. Once you address the first error, you might get a warning about single documents based on that. (The end-of-document marker consists of three dots: ... at the beginning of a line followed by whitespace.

Of course any changes you make should confirm to what kubernetes is expecting, but the above stream is clearly non-valid as YAML in itself.

-- Anthon
Source: StackOverflow
7/13/2017

By default, 'kubernetes.io/hostname' is a well known label that contains the Node's name instead of its IP address. This can be checked by running $ kubectl get nodes --show-labels. As such, I recommend to make the following changes:

  nodeSelector: 
    kubernetes.io/hostname: westporch-kubeminion-1
-- Irina
Source: StackOverflow
11/2/2018

Most of the time when you get an error like this (speaking in general and meaningful terms) it is either because of :-

1). A syntax error (in your case it is not) in the yaml file.

2). Or like the error says "mapping values are not allowed in this context". It means that the keys/values you have used in the yaml, may be syntactically right but not semantically.

For example, in you case the context is "deployment" which belongs to "apiversion: extensions/v1beta1", and it expects the node selector to be like below:-

nodeSelector:
  kubernetes.io/hostname: 10.0.24.52

Ideally, you should never use IP like above but a key-value pair like this:- topologyKey: failure-domain.beta.kubernetes.io/zone OR in your case it can be something like this:- kubernetes.io/hostname: zone-a-node

-- Suhas Chikkanna
Source: StackOverflow