Readyator

Waits for specified urls or ports on localhost to be ready before running a supplied command.

Features

• More reliable than sleep: Actually checks if services are responding
• Faster execution: Continues as soon as ready (no fixed wait)
• Better error handling: Fails fast if services don't start
• More professional: Industry-standard approach for service dependencies

Pratical Example

Before:

./dev/up
sleep 5  # Hope services are ready
npm test

After:

./dev/up readyator 5555,5556,3000,5558 "npm test"

Installation

npm

npm install readyator

Yarn

yarn add readyator

Usage

Preface

• Addresses (ports or urls) must be separated by comma if you want to check for multiple services to be ready ( returning a successful HTTP status code).
• Your command must be surrounded by quotes so that it can be properly parsed.
• The default check interval is 1s (1000ms) but can be changed.

Wait for ports

Command:

readyator [ports] [command]

Example:

readyator 8080,8081 "npm run start"

If you're not looking to perform any specific actions but simply want to determine when the service is available, use this command:

readyator 8080,8081 "exit 0"

Wait for URLs

Command:

readyator [urls] [command]

Example:

readyator https://www.google.com/,http://localhost:8081/ "npm run start"

Change check interval

Command:

readyator [urls] [command] [interval_in_millis]

Example:

readyator https://www.google.com/ "npm run start" 5000

Wait for healthy Docker container

Command:

readyator-docker [container_name] [interval_in_millis]

Example:

readyator-docker my_docker_container 1000

Node.js API

You can use readyator also through its Node.js API:

import readyator from 'readyator';

await readyator([8080, 8081], 'npm run start');

It also supports executing a callback function:

import readyator from 'readyator';

const callback = () => {
  console.log('System is online!');
};

readyator([8080, 8081], callback);

Readyator's programmatic interface can also be used to listen for Docker containers to become healthy:

import {runWhenHealthy} from 'readyator';

await runWhenHealthy('my_docker_container');

Development

Here is how you can easily test the readyator from your development environment when checking out the code:

npm start https://www.google.com/ "npm run exit"