ruready

ruready is an application that exposes an HTTP endpoint to allow you to check if a machine is ready. It can be used in conjunction with docker-compose to make one container wait for another one to be ready. The ready state is determined by a command passed as argument.

Downloads

• The latest compiled version is available on the releases page
• To compile from sources, build the repository using go

Full working example

The client container waits for mysql on the db container to become available.

Create a file called docker-compose.yml with the content below:

version: '2'
services:
  db:
    image: "mysql"
    environment:
        - MYSQL_ROOT_PASSWORD=1q2w3e
    ports:
     - "8099:8099"
    command: bash -c "apt-get update && apt-get -y install curl && curl -L https://github.com/victorhurdugaci/ruready/releases/download/1.0.0-alpha.1/ruready > ruready && chmod +x ruready && (./ruready -c mysql -- --host=localhost --port=3306 --user=root --password=1q2w3e --execute=quit & ./entrypoint.sh mysqld)"
    
  client:
    image: "busybox"
    command: sh -c "while [ true ]; do wget -q -O - http://db:8099/ready && break; echo 'Not ready...'; sleep 1s; done; echo 'Ready!';"

Run docker-compose up in the folder where you created the file.

Command line arguments

Argument	Required	Default	Description
-c/--command	Yes		The command that checks if the machine is ready
-t/--cachetime	No	3	Number of seconds to cache the result of the command before reinvoking
-p/--port	No	8099	Server port
-v/--version	No		Shows version information
--	No		Anything that follows -- is passed as argument to command

Examples

• ruready -c ls -- ./opt/app/started.txt Waits for the file ./opt/app/started.txt to exist. Endpoint <hostname>:8099/ready

• ruready -p 3000 -c ls -- ./opt/app/started.txt Waits for the file ./opt/app/started.txt to exist. Endpoint <hostname>:3000/ready

Response

• If the machine is ready, /ready endpoint returns 200 (OK) and the message ruready: Ready
• If the machine is not ready, /ready endpoint returns 503 (Service Unavailable) and the message ruready: Not Ready

Checking if the machine is available

• curl: while [ true ]; do curl -I http://<host>:8099/ready && break; echo 'Not ready...'; sleep 1s; done;
• wget: while [ true ]; do wget -q -O - http://<host>:8099/ready && break; echo 'Not ready...'; sleep 1s; done;