App Runner Router

This is an optional extension to AppRunner that allows for horizontal scaling of AppRunner instances. The basic idea is that you can start multiple, independent AppRunners on different machines, and then have the App Runner Router act as a reverse proxy, sending requests to the various instances it knows about.

Installation and configuration

Download the jar, create a log config, and start it. There is an example in the local directory of this repo. (Alternatively, build your own package by using the app-runner-router-lib - see the app-runner-router module in this repo for an example that builds it as an uber-jar.)

To register App Runner instances with the router, first start them, then POST information to the router.

For example, if the router is running at apprunner.example.org and you have an app runner instance at some-host.example.org:8080, then make the following request:

POST http://apprunner.example.org/api/v1/runners
Form parameters:
    id: a unique identifier for the app runner instance, for example some-host
    url: the URL of the instance, e.g. http://some-host.example.org:8080
    maxApps: the maximum number of applications that can be added to an instance

Example curl command: curl --data 'id=some-name&maxApps=20&url=https://some-host.exaple.org' -X POST https://apprunner.example.org/api/v1/runners

Aside from the extra operations in /api/v1/runners, the router has the same REST API as an app-runner instance. In general, it will simply proxy requests to the correct instance, with a couple of exemptions: GET /api/v1/apps returns an aggregation of all apps across all instances, and POST /api/v1/apps will first pick an instance to create the app in, and send it there.

The router can also proxy direct to instances via the /api/v1/runner-proxy/{runnerid} endpoint. For example, if you have a runner with the ID myrunner on https://myrunner.example/ then a call to /api/v1/runner-proxy/myrunner/api/v1/system will get proxied to https://myrunner.example/api/v1/system

Running locally

Clone the repo and then run mvn compile, and then run the main method in RunLocal.java

This will start two App Runner instances (with different versions) and register all the sample apps against it, and then open a browser to the API. You can then run something like App Runner Home locally against your local router.

Change log

• 1.10.3 Fixed UDP publishing of responses, removed access logs (for now) and added more stats to the system API.
• 1.8.0 When creating an app with a POST to /api/v1/apps you can now ask the router to exclude a runner by putting its ID in the X-Excluded-Runner header (multiple headers allowed).
• 1.6.0 If some app runner instances are unavailable, the /apps and /system calls will still return and will include details about the errors.
• 1.5.2 Added optional config for handling proxy timeouts: apprunner.proxy.idle.timeout (default 30000ms) apprunner.proxy.total.timeout (default 20 mins).
• 1.5.1 The REST API is now gzipped. Also added a favicon.
• 1.5.0 Added optional publishing of request metrics over UDP.
• 1.4.0 Changed the runners API to allow PUTing changes to runner instances (and POSTing to an existing one returns a 409) plus added appCount to the runners API.
• 1.3.0 Added appCount to apps api and fixed X-Forwarded-* headers.
• 1.2.0 Fixed streaming, missing CORS headers, added full runner info the systems API, and increased response timeouts.
• 1.1.4 Fixed bugs where the router is HTTPS and an instance is HTTP.