configmap-reload

What is configmap-reload?

The configmap-reload image provides a lightweight sidecar utility designed to monitor Kubernetes ConfigMaps and Secrets. When it detects changes, it triggers an application reload by sending a signal (such as SIGHUP) or making an HTTP request to a specified endpoint.

It is commonly used with applications that support hot-reloading of configuration, such as Prometheus, Alertmanager, or other monitoring tools. By running alongside these applications, configmap-reload ensures that configuration updates are applied without restarting the entire pod.

This image is widely adopted because it is simple, reliable, and purpose-built for dynamic configuration management in Kubernetes.

How to use this image

The configmap-reload image is typically run as a sidecar container alongside the main application.

Examples:

apiVersion: v1
kind: Pod
metadata:
  name: prometheus
spec:
  containers:
    - name: prometheus
      image: prom/prometheus:latest
      args:
        - "--config.file=/etc/prometheus/prometheus.yml"
      volumeMounts:
        - name: config
          mountPath: /etc/prometheus
    - name: configmap-reload
      image: jimmidyson/configmap-reload:v0.12.0
      args:
        - --volume-dir=/etc/prometheus
        - --webhook-url=http://localhost:9090/-/reload
      volumeMounts:
        - name: config
          mountPath: /etc/prometheus
  volumes:
    - name: config
      configMap:
        name: prometheus-config

In this example, when the Prometheus ConfigMap is updated, configmap-reload automatically calls the Prometheus reload endpoint to apply the changes.

Image variants

The configmap-reload image is generally published under jimmidyson/configmap-reload and available in these forms:

configmap-reload:<version>

Version-pinned images (e.g., configmap-reload:v0.12.0). Recommended for production use to ensure consistent behavior.

configmap-reload:latest

Tracks the most recent stable release. Useful for quick testing but less predictable for long-term deployments.

configmap-reload:canary / dev

Cut from the development branch. Intended for contributors or teams testing unreleased features.