Unexpected content added to yaml file

[dmitchsplunk]

I'm trying to update the opentelemetry-demo.yaml file with yq, which includes multiple documents. Specifically, I'd like to add the following environment variable to each container:

- name: NODE_IP
  valueFrom:
    fieldRef:
      fieldPath: status.hostIP

I tried using the following command for this:

    yq eval -i '(.spec.template.spec.containers[].env) += {
      "name": "NODE_IP",
      "valueFrom": {
        "fieldRef": {
          "fieldPath": "status.hostIP"
        }
      }
    }
    ' opentelemetry-demo.yaml

That works fine for documents in the file that include .spec.template.spec.containers[].env. For example:

spec:
  replicas: 1
  selector:
    matchLabels:
      opentelemetry.io/name: opentelemetry-demo-paymentservice
  template:
    metadata:
      labels:
        opentelemetry.io/name: opentelemetry-demo-paymentservice
        app.kubernetes.io/instance: opentelemetry-demo
        app.kubernetes.io/component: paymentservice
        app.kubernetes.io/name: opentelemetry-demo-paymentservice
    spec:
      serviceAccountName: opentelemetry-demo
      containers:
        - name: paymentservice
          image: 'ghcr.io/open-telemetry/demo:1.6.0-paymentservice'
          imagePullPolicy: IfNotPresent
          ports:
            - containerPort: 8080
              name: service
          env:
            - name: OTEL_SERVICE_NAME
              valueFrom:
                fieldRef:
                  apiVersion: v1
                  fieldPath: metadata.labels['app.kubernetes.io/component']
            - name: OTEL_COLLECTOR_NAME
              value: 'opentelemetry-demo-otelcol'
            - name: OTEL_EXPORTER_OTLP_METRICS_TEMPORALITY_PREFERENCE
              value: cumulative
            - name: PAYMENT_SERVICE_PORT
              value: "8080"
            - name: OTEL_EXPORTER_OTLP_ENDPOINT
              value: http://$(OTEL_COLLECTOR_NAME):4317
            - name: OTEL_RESOURCE_ATTRIBUTES
              value: service.name=$(OTEL_SERVICE_NAME),service.namespace=opentelemetry-demo
            - name: NODE_IP
              valueFrom:
                fieldRef:
                  fieldPath: status.hostIP

But it's also adding .spec.template.spec.containers[] to documents that didn't have it before. For example:

apiVersion: v1
kind: ServiceAccount
metadata:
  labels:
    app.kubernetes.io/name: grafana
    app.kubernetes.io/instance: opentelemetry-demo
    app.kubernetes.io/version: "10.1.5"
  name: opentelemetry-demo-grafana
  namespace: otel-demo
spec:
  template:
    spec:
      containers: []

How do I ensure that the new environment variable is only added to documents that already include .spec.template.spec.containers[].env?

[mikefarah]

Just add a select first to only select documents that you want updated.

It'll be something like:

 yq eval -i '(select(.spec.template.spec.containers) | .spec.template.spec.containers[].env) += {
      "name": "NODE_IP",
      "valueFrom": {
        "fieldRef": {
          "fieldPath": "status.hostIP"
        }
      }
    }
    ' opentelemetry-demo.yaml

You can put boolean expression in select to check for length and other things too - similar to this example here: https://mikefarah.gitbook.io/yq/recipes#find-and-update-items-in-an-array

[dmitchsplunk]

Thanks @mikefarah, that works!