ngerakines / k8s-consul-mutator-rs

A mutating webhook that writes consul key checksums to k8s resources.

k8s-consul-mutator-rs

A Kubernetes mutating webhook that patches resources with checksums of consul keys.

Configuration

This application uses the following environment variables:

• RUST_LOG - Sets logging configuration. The default value is k8s_consul_mutator_rs=debug,tower_http=debug.
• PORT - Setting PORT to 0 disables the insecure (HTTP) interface. The default value is 8080.
• SECURE_PORT - Setting SECURE_PORT to 0 disables the secure (HTTPS) interface. The default value is 8443.
• CERTIFICATE - Both the CERTIFICATE and CERTIFICATE_KEY values must be set to file path values in order for the secure (HTTPS) interface to start.
• CERTIFICATE_KEY
• CONSUL_HTTP_ADDR - The CONSUL_HTTP_ADDR environment variable is used to configure which consul endpoint is used for key subscriptions. The default value is http://127.0.0.1:8500.
• CONSUL_HTTP_TOKEN
• CONSUL_HTTP_SSL_VERIFY
• UPDATE_DEBOUNCE - The amount of time to wait before making updates to deployments when checksums change.
• WATCH_DISPATCHER_FIRST_RECONCILE - The amount of time to wait when the application starts before performing deployment reconciliation.
• WATCH_DISPATCHER_RECONCILE - The amount of time to wait inbetween deployment reconcillation.
• WATCH_DISPATCHER_DEBOUNCE - The amount of time to wait for consul watch create and delete actions to settle.
• CHECK_KEY_TIMEOUT - The amount of time to poll consul for key updates.
• CHECK_KEY_IDLE - The amount of time to allow the consul key watcher to idle before shutting down.
• CHECK_KEY_ERROR_WAIT - The amount of time to skip in between cycles when an error is encountered polling consul keys.
• SET_DEPLOYMENT_ANNOTATIONS - Adds the checksum annotations to deployments if set to true. Default true.
• SET_DEPLOYMENT_SPEC_ANNOTATIONS - Adds the checksum annotations to deployment specs if set to true. Default true.
• SET_DEPLOYMENT_TIMESTAMP - Adds the last-updated annotation to deployments if set to true. Default true.
• SET_DEPLOYMENT_SPEC_TIMESTAMP - Adds the last-updated annotation to deployment specs if set to true. Default false.

The default values are ideal for a verbose and insecure production environment. For production use, start with the following and tune them accordingly:

RUST_LOG=k8s_consul_mutator_rs=warning
PORT=0
CERTIFICATE=/path/to/your/certificate.crt
CERTIFICATE_KEY=/path/to/your/certificate.key
CONSUL_HTTP_ADDR=https://consul.consul.svc:8501
CONSUL_HTTP_TOKEN=68a1a640-96d9-4c33-8074-5b49378aa881
CONSUL_HTTP_SSL_VERIFY=true
UPDATE_DEBOUNCE=60
WATCH_DISPATCHER_FIRST_RECONCILE=120
WATCH_DISPATCHER_RECONCILE=600
WATCH_DISPATCHER_DEBOUNCE=60
CHECK_KEY_TIMEOUT=10s
CHECK_KEY_IDLE=600
CHECK_KEY_ERROR_WAIT=30

It is important to understand how these values will impact shutdown time. Specifically, the CHECK_KEY_ERROR_WAIT introduces an async sleep for that number of seconds. That means, if an error occurs with consul and a shutdown is initiated, shutdown will be blocked for at least that amount of time.

Usage

This Kubernetes mutating webhook will write the checksum of a Consul key into into a resource annotation.

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: app
  annotations:
    k8s-consul-mutator.io/key-config: app/config

The above annotation for the app deployment would result in the following mutation.

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: app
  annotations:
    k8s-consul-mutator.io/key-config: app/config
    k8s-consul-mutator.io/checksum-config: md5-e80ca0bfa6b0c57f6360e22f1aebabc5
    k8s-consul-mutator.io/last-updated: 2023-02-17T21:51:13.479453+00:00
spec:
  template:
    metadata:
      annotations:
        k8s-consul-mutator.io/checksum-config: md5-e80ca0bfa6b0c57f6360e22f1aebabc5
        k8s-consul-mutator.io/last-updated: 2023-02-17T21:51:13.479453+00:00

Disclosures

GitHub Copilot contributed to code in this repository.

Commits that were influenced by GitHub Copilot will have the [copilot] tag appended.

Roadmap

• Project stubbed out
• HTTP endpoint for status
• HTTP endpoint for mutate
• Key manager for checksums
• Consul configuration at start
• Background workers for polling consul kv reads
• Track kubernetes resources to update
• Update kubernetes resources on consul kv change
• Stop consul watchers for keys that are no longer used
• Start consul watchers for existing deployments
• Support sha checksums
• Support fnv checksums
• Populate background workers at startup
• Configuration for consul tokens
• Configuration for default checksum type
• Configuration validation on start
• Helm chart