How does the agents.volumes parameter supposed to work in Datadog Helm Chart

Question

I'm attempting to mount a filepath into my datadog agent container, which is being provisioned into a kubernetes cluster via Datadog Helm Chart.

I'm using agents.volumes value to pass in. which the docs describe as "Specify additional volumes to mount in the dd-agent container".

Based on the syntax found in the Datadog/helm-charts repo - I'm using:

  agents:
    volumes:
      - hostPath:
          path: /var/log/cloud-init.log
        name: cloud-init

But when I apply that change to my cluster, I don't see any evidence that this path has been mounted anywhere on my agent container. I'm not seeing any great explanation of mount a volume from my host container into the datadog agent container.

Answer 1

I see that value is only used to declare the volumes on the DaemonSet pod definition, not to mount them.

agents.volumes is for defining custom volumes on the agent but this is used on the DaemonSet definition, specifically on spec.template.spec.volumes look here.

apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: {{ template "datadog.fullname" . }}
  namespace: {{ .Release.Namespace }}
  ...
spec:
    ...
    spec:
      ...
      volumes:
      ...
{{- if .Values.agents.volumes }}
{{ toYaml .Values.agents.volumes | indent 6 }}
{{- end }}

To actually use those volumes you have to define the variable agents.volumeMounts which is used here.

{{- define "container-agent" -}}
- name: agent
  image: "{{ include "image-path" (dict "root" .Values "image" .Values.agents.image) }}"
  ...
  volumeMounts:
    ...
{{- if .Values.agents.volumeMounts }}
{{ toYaml .Values.agents.volumeMounts | indent 4 }}
{{- end }}
...
{{- end -}}

So you most likely want to define your values like this:

agents:
  volumes:
    - hostPath:
        path: /var/log/cloud-init.log
      name: cloud-init
  volumeMounts:
    - name: cloud-init
      mountPath: /some/path
      readOnly: true