Waiter

Waiter is a tiny application that will wait for a set of services to become available and then exit cleanly when they are all available. This is ideal for with init-containers in Kubernetes so your application will only start when all its service dependencies are available.

It supports the following services:

• MySQL - wait for a MySQL server to become available and for a specific table to have been created.
• Redis - wait for a Redis server to be available.

Usage

This is most useful when used as an init container within a Kubernetes pod. You can add individual init containers for each service or configure multiple services within the same container to reduce (the small) overhead in starting individual containers.

initContainers:
  - name: waiter
    image: ghcr.io/adamcooke/waiter:v1
    env:
      - name: SERVICES
        value: mysql
      - name: MYSQL_HOST
        value: mysql.default.svc.cluster.local
      - name: MYSQL_USERNAME
        value: root
      - name: MYSQL_PASSWORD
        valueFrom:
          secretKeyRef:
            name: mysql-credentials
            key: password
      - name: MYSQL_DATABASE
        value: my_database

Alternatively, you can use this directly within Docker if you wish.

docker run --rm -e SERVICES=mysql -e MYSQL_HOST=mysql -e MYSQL_USERNAME=root -e MYSQL_PASSWORD=secret -e MYSQL_DATABASE=my_database ghcr.io/adamcooke/waiter:v1

Configuration

All configuration is provided through environment variables. The following variables are available:

General configuration

• SERVICES - an array of service types (seperated by commas) to wait for (options: mysql, redis)
• INTERVAL - the length of time to wait between checks in seconds (default: 2)

MySQL configuration

• MYSQL_HOST - the hostname or IP of a MySQL
• MYSQL_PORT - the MySQL port (default: 3306)
• MYSQL_USERNAME - the MySQL username (default: root)
• MYSQL_PASSWORD - the MySQL password
• MYSQL_DATABASE - the MySQL database to check presence of
• MYSQL_TABLE - the MySQL table (within above database) to check presence of

RediS configuration

• REDIS_HOST - the hostname or IP of a Redis
• REDIS_PORT - the Redis port (default 6379)
• REDIS_PASSWORD - the Redis server password