Overview

The Datadog Admission Controller is a component of the Datadog Cluster Agent. The main benefit of the Admission Controller is to simplify your application Pod configuration. For that, it has two main functionalities:

• Inject environment variables (DD_AGENT_HOST, DD_TRACE_AGENT_URL and DD_ENTITY_ID) to configure DogStatsD and APM tracer libraries into the user’s application containers.
• Inject Datadog standard tags (env, service, version) from application labels into the container environment variables.

Datadog’s Admission Controller is MutatingAdmissionWebhook type. For more details on admission controllers, see the Kubernetes guide on admission controllers.

Requirements

• Datadog Cluster Agent v7.40+

Configuration

apiVersion: datadoghq.com/v2alpha1
kind: DatadogAgent
metadata:
  name: datadog
spec:
  #(...)
  features:
    admissionController:
      enabled: true
      mutateUnlabelled: false

#(...)
clusterAgent:
  #(...)
  ## @param admissionController - object - required
  ## Enable the admissionController to automatically inject APM and
  ## DogStatsD config and standard tags (env, service, version) into
  ## your pods
  #
  admissionController:
    enabled: true

    ## @param mutateUnlabelled - boolean - optional
    ## Enable injecting config without having the pod label:
    ## admission.datadoghq.com/enabled="true"
    #
    mutateUnlabelled: false

- apiGroups:
  - admissionregistration.k8s.io
  resources:
  - mutatingwebhookconfigurations
  verbs: ["get", "list", "watch", "update", "create"]
- apiGroups: [""]
  resources: ["secrets"]
  verbs: ["get", "list", "watch", "update", "create"]
- apiGroups: ["batch"]
  resources: ["jobs", "cronjobs"]
  verbs: ["get"]
- apiGroups: ["apps"]
  resources: ["statefulsets", "replicasets", "deployments"]
  verbs: ["get"]

apiVersion: v1
kind: Service
metadata:
  name: datadog-cluster-agent-admission-controller
  labels:
    app: "datadog"
    app.kubernetes.io/name: "datadog"
spec:
  selector:
    app: datadog-cluster-agent
  ports:
  - port: 443
    targetPort: 8000

- name: DD_ADMISSION_CONTROLLER_ENABLED
  value: "true"
- name: DD_ADMISSION_CONTROLLER_SERVICE_NAME
  value: "datadog-cluster-agent-admission-controller"

# Uncomment this to configure APM tracers automatically (see below)
# - name: DD_ADMISSION_CONTROLLER_MUTATE_UNLABELLED
#   value: "true"

Instrumentation library injection

You can configure the Cluster Agent (version 7.39 and higher) to inject instrumentation libraries. Read Instrumentation library injection with Admission Controller for more information.

APM and DogStatsD

To configure DogStatsD clients or other APM libraries that do not support library injection, inject the environment variables DD_AGENT_HOST and DD_ENTITY_ID by doing one of the following:

• Add the label admission.datadoghq.com/enabled: "true" to your Pod.
• Configure the Cluster Agent admission controller by setting mutateUnlabelled (or DD_ADMISSION_CONTROLLER_MUTATE_UNLABELLED, depending on your configuration method) to true.

Adding a mutateUnlabelled: true Agent config in the Helm chart causes the Cluster Agent to attempt to intercept every unlabelled Pod.

To prevent Pods from receiving environment variables, add the label admission.datadoghq.com/enabled: "false". This works even if you set mutateUnlabelled: true.

If mutateUnlabelled is set to false, the Pod label must be set to admission.datadoghq.com/enabled: "true".

Possible options:

Order of priority

The Datadog Admission Controller does not inject the environment variables DD_VERSION, DD_ENV, or DD_SERVICE if they already exist.

When these environment variables are not set, the Admission Controller uses standard tags value in the following order (highest first):

• Labels on the Pod
• Labels on the ownerReference (ReplicaSets, DaemonSets, Deployments, etc.)

Configure APM and DogstatsD communication mode

Starting from Datadog Cluster Agent v1.20.0, the Datadog Admission Controller can be configured to inject different modes of communication between the application and Datadog agent.

This feature can be configured by setting admission_controller.inject_config.mode or by defining a Pod-specific mode using the admission.datadoghq.com/config.mode Pod label.

Possible options:

Note: Pod-specific mode takes precedence over the global mode defined at the Admission Controller level.

Troubleshooting

See Admission Controller Troubleshooting.

Further Reading

Documentation, liens et articles supplémentaires utiles:

Troubleshooting the Datadog Cluster AgentDOCUMENTATION Troubleshooting the Admission ControllerDOCUMENTATION Use library injection to auto-instrument tracing for Kubernetes applications with Datadog APMBLOG