Docker Host URL

URL host resolver for Docker applications

This library provides URL resolving helpers that resolve URLs that contain the domain host.docker.internal. On Mac and Linux hosts this resolves differently, and this library is designed to handle both types of hosts.

You can pass a variety of values to the resolution functions that will detect and replace host.docker.internal:

• HTTP/HTTPS URLs: http://host.docker.internal/some/page
• Other protocols: ftp://host.docker.internal/dir
• Just the domain: host.docker.internal
• URLs with credentials: mysql://user:[email protected]:3306/dbname

Installation

Install this library as a dependency to use in any environment:

npm install docker-host-url --save

Usage

Consider an internal application URL like http://host.docker.internal:8080/api/resource - when being requested from inside a Docker application this may not resolve correctly. Using this library, a call like the following would be able to resolve it to an IP address:

import { resolveURL } from "docker-host-url";

// ...

const url = await resolveURL("http://host.docker.internal:8080/api/resource");
// url = http://172.17.0.1:8080/api/resource

Whereas URLs not containing host.docker.internal will not be changed:

const url = await resolveURL("https://test.com:8080/api/resource");
// url = https://test.com:8080/api/resource

This difference allows you to continue using this library in production as it will have no effect on other domains.

Sync usage

This library makes async calls to resolve the host.docker.internal domain, so sync use is not possible without first performing some async call. In situations where you're able to run some async task before the application properly starts, you can call the init function to resolve the domain early, allowing you to later call resolveURLSync synchronously.