Kubernetes mutating admission webhook to automatically annotate pods.

Features:

• Automatically annotate new pods with certain labels
• YAML-based configuration for multiple rules
• Built-in Prometheus metrics exporter

Configurations:

• LOG_FORMAT: json/text
• LOG_LEVEL: trace/debug/info/warning/error/fatal/panic
• RULES_FILE: path to config.yaml
• TLS_ENABLED: must be true when running inside Kubernetes cluster as admission controller
• TLS_CRT: path to certfile for TLS config
• TLS_KEY: path to keyfile for TLS config

Rules config sample:

# config.yaml
- selector:
    app: http-service
  annotations:
    log.config.scalyr.com/include: true
- selector:
    app: postgresql
  annotations:
    log.config.scalyr.com/include: false

Setup:

1. Make sure the cluster support admission controller (at least Kubernetes 1.9)
2. Prepare TLS certificate (see Medium post below, you need cluster-admin permission)
3. Create kubernetes resources (see examples directory, please read the comments especially about CA bundle and certificates)
4. Label the namespace you want to enable (kubectl label namespace ${namespace} kube-annotate=enabled)

TODO:

• bind internal endpoints (health, metrics) to separate port
• proper request/response logging
• prometheus exporter
• helm chart for easier setup

References:

• https://medium.com/ibm-cloud/diving-into-kubernetes-mutatingadmissionwebhook-6ef3c5695f74
• https://github.com/morvencao/kube-mutating-webhook-tutorial