mapping values are not allowed in this context

Question

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?

Answer 1

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.