k8s-image-availability-exporter

k8s-image-availability-exporter (or k8s-iae for short) is a Prometheus exporter that warns you proactively about images that are defined in Kubernetes objects (e.g., an image field in the Deployment) but are not available in the container registry (such as Docker Registry, etc.).

Receiving alerts when container images related to running Kubernetes controllers are missing helps you to solve the problem before it manifests itself. For more details on the reasons behind k8s-iae and how it works, please read this article.

• Deploying / Installing k8s-iae in your Kubernetes cluster
  • Prometheus integration to scrape metrics
  • Alerting based on k8s-iae metrics
• Configuration
  • CLI options
• Metrics for Prometheus provided by k8s-iae
• Compatibility

Deploying

Container image

Ready-to-use container images are available in the Deckhouse registry:

docker pull registry.deckhouse.io/k8s-image-availability-exporter/k8s-image-availability-exporter:latest

Helm Chart

The helm chart is available on artifacthub. Follow instructions on the page to install it.

Prometheus integration

Here's how you can configure Prometheus or prometheus-operator to scrape metrics from k8s-image-availability-exporter.

Prometheus

- job_name: image-availability-exporter
  honor_labels: true
  metrics_path: '/metrics'
  scheme: http
  kubernetes_sd_configs:
  - role: pod
    namespaces:
      names:
      - kube-system
  relabel_configs:
  - source_labels: [__meta_kubernetes_pod_label_app]
    regex: image-availability-exporter
    action: keep

prometheus-operator

apiVersion: monitoring.coreos.com/v1
kind: PodMonitor
metadata:
  name: image-availability-exporter
  namespace: kube-system
spec:
  podMetricsEndpoints:
  - port: http-metrics
    scheme: http
    honorLabels: true
    scrapeTimeout: 10s
  selector:
    matchLabels:
      app: image-availability-exporter
  namespaceSelector:
    matchNames:
    - kube-system

Alerting

Here's how to alert based on these metrics:

Prometheus

groups:
  - alert: DeploymentImageUnavailable
    expr: |
      max by (namespace, name, container, image) (
        k8s_image_availability_exporter_available{kind="deployment"} == 0
      )
    annotations:
      message: >
        Image {{`{{ $labels.image }}`}} from container {{`{{ $labels.container }}`}}
        in deployment {{`{{ $labels.name }}`}}
        from namespace {{`{{ $labels.namespace }}`}}
        is not available in docker registry.
    labels:
      severity: critical
  - alert: StatefulSetImageUnavailable
    expr: |
      max by (namespace, name, container, image) (
        k8s_image_availability_exporter_available{kind="statefulset"} == 0
      )
    annotations:
      message: >
        Image {{`{{ $labels.image }}`}} from container {{`{{ $labels.container }}`}}
        in statefulSet {{`{{ $labels.name }}`}}
        from namespace {{`{{ $labels.namespace }}`}}
        is not available in docker registry.
    labels:
      severity: critical
  - alert: DaemonSetImageUnavailable
    expr: |
      max by (namespace, name, container, image) (
        k8s_image_availability_exporter_available{kind="daemonset"} == 0
      )
    annotations:
      message: >
        Image {{`{{ $labels.image }}`}} from container {{`{{ $labels.container }}`}}
        in daemonSet {{`{{ $labels.name }}`}}
        from namespace {{`{{ $labels.namespace }}`}}
        is not available in docker registry.
    labels:
      severity: critical
  - alert: CronJobImageUnavailable
    expr: |
      max by (namespace, name, container, image) (
        k8s_image_availability_exporter_available{kind="cronjob"} == 0
      )
    annotations:
      message: >
        Image {{`{{ $labels.image }}`}} from container {{`{{ $labels.container }}`}}
        in cronJob {{`{{ $labels.name }}`}}
        from namespace {{`{{ $labels.namespace }}`}}
        is not available in docker registry.
    labels:
      severity: critical

Configuration

Command-line options

Usage of k8s-image-availability-exporter:
  -allow-plain-http
        whether to fallback to HTTP scheme for registries that don't support HTTPS
  -bind-address string
        address:port to bind /metrics endpoint to (default ":8080")
  -capath value
        path to a file that contains CA certificates in the PEM format
  -check-interval duration
        image re-check interval (default 1m0s)
  -default-registry string
        default registry to use in absence of a fully qualified image name, defaults to "index.docker.io"
  -force-check-disabled-controllers value
        comma-separated list of controller kinds for which image is forcibly checked, even when workloads are disabled or suspended. Acceptable values include "Deployment", "StatefulSet", "DaemonSet", "Cronjob" or "*" for all kinds (this option is case-insensitive)
  -ignored-images string
        tilde-separated image regexes to ignore, each image will be checked against this list of regexes
  -namespace-label string
        namespace label for checks
  -skip-registry-cert-verification
        whether to skip registries' certificate verification

Metrics

The following metrics for Prometheus are provided:

• k8s_image_availability_exporter_available — non-zero indicates successful image check.
• k8s_image_availability_exporter_absent — non-zero indicates an image's manifest absence from container registry.
• k8s_image_availability_exporter_bad_image_format — non-zero indicates incorrect image field format.
• k8s_image_availability_exporter_registry_unavailable — non-zero indicates general registry unavailiability, perhaps, due to network outage.
• k8s_image_availability_exporter_authentication_failure — non-zero indicates authentication error to container registry, verify imagePullSecrets.
• k8s_image_availability_exporter_authorization_failure — non-zero indicates authorization error to container registry, verify imagePullSecrets.
• k8s_image_availability_exporter_unknown_error — non-zero indicates an error that failed to be classified, consult exporter's logs for additional information.

Each metric has the following labels:

• namespace - namespace name
• container - container name
• image - image URL in the registry
• kind - Kubernetes controller kind, namely deployment, statefulset, daemonset or cronjob
• name - controller name

Compatibility

k8s-image-availability-exporter is compatible with Kubernetes 1.15+ and Docker Registry V2 compliant container registries.

Since the exporter operates as a Deployment, it does not support container registries that should be accessed via authorization on a node.