Kubernetes Init Container - Dependency Checker

This repository provides a Python script designed to be used as a Kubernetes Init Container. The script ensures that all necessary dependencies are available before the main application starts. It checks connections to PostgreSQL, Redis, RabbitMQ, and HashiCorp Consul, and verifies environment variables retrieved from Consul.

Features

• Validates PostgreSQL database connection.
• Checks Redis availability.
• Confirms RabbitMQ connection.
• Fetches and verifies environment variables from HashiCorp Consul.
• Waits until all dependencies are ready before proceeding.

Requirements

• Python 3.8+
• Kubernetes cluster
• HashiCorp Consul
• Access to the required services (PostgreSQL, Redis, RabbitMQ, and Consul).

Environment Variables

The script uses the following environment variables to configure connections:

Variable	Description	Type	Default
CONSUL_HOST	Hostname or IP of the Consul server.	str	localhost
CONSUL_PORT	Port number of the Consul server.	int	8500
CONSUL_PREFIX	The prefix used for Consul keys.	str	None
CONSUL_MANDATORY_KEYS	Mandatory Consul keys.	list	None
CONSUL_OPTIONAL_KEYS	Optional Consul keys.	list	""
CONSUL_CONNECTION_CHECK_KEY	An Arbitrary Key has to be set in Consul, to check the Consul its own connectivity.	str	""
DB_HOST	Hostname or IP of the PostgreSQL server.	str	DATABASE_HOST
DB_PORT	Port number of the PostgreSQL server.	str	DATABASE_PORT
DB_USER	Username for PostgreSQL authentication.	str	DATABASE_USER
DB_PASS	Password for PostgreSQL authentication.	str	DATABASE_PASS
DB_NAME	Name of the PostgreSQL database.	str	DATABASE_NAME
REDIS_HOST	Hostname or IP of the Redis server.	str	localhost
REDIS_PORT	Port number of the Redis server.	str	6379
RABBITMQ_HOSTNAME	Hostname or IP of the RabbitMQ server.	str	localhost
RABBITMQ_PORT	Port number of the RabbitMQ server.	str	5672
RABBITMQ_USERNAME	Username for RabbitMQ authentication.	str	DEFAULT_USERNAME
RABBITMQ_PASSWORD	Password for RabbitMQ authentication.	str	DEFAULT_PASSWORD

Usage

Kubernetes Deployment Example

apiVersion: apps/v1
kind: Deployment
metadata:
  name: example-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      app: example-app
  template:
    metadata:
      labels:
        app: example-app
    spec:
      initContainers:
      - name: dependency-checker
        image: your-image:tag
        env:
        - name: CONSUL_HOST
          value: "consul.example.com"
        - name: CONSUL_PORT
          value: "8500"
        - name: CONSUL_PREFIX
          value: "config/"
        - name: CONSUL_MANDATORY_KEYS
          value: "redis,postgresql"
        - name: CONSUL_OPTIONAL_KEYS
          value: "rabbitmq"
        # This below key,value has to be set in Consul
        - name: CONSUL_CONNECTION_CHECK_KEY
          value: "consul_connection_key"

      containers:
      - name: example-app
        image: example-app:latest

Docker Build and Push Example

docker build -t your-image:tag .
docker push your-image:tag

Dependencies

• py-consul - HashiCorp Consul client.
• psycopg - PostgreSQL client.
• psycopg[binary] - contains the optional optimization for PostgreSQL client.
• redis - Redis client.
• pika - RabbitMQ client.

pip install -r requirements.txt

License

MIT

Author Information

Created and maintained by Ali Mehraji [email protected]