Lightbend Activator

Finagle quickstart

Finagle quickstart

April 21, 2014
scala finagle http quickstart

Activator template for Finagle.

How to get "Finagle quickstart" on your computer

There are several ways to get this template.

Option 1: Choose finagle-quickstart in the Lightbend Activator UI.

Already have Lightbend Activator (get it here)? Launch the UI then search for finagle-quickstart in the list of templates.

Option 2: Download the finagle-quickstart project as a zip archive

If you haven't installed Activator, you can get the code by downloading the template bundle for finagle-quickstart.

  1. Download the Template Bundle for "Finagle quickstart"
  2. Extract the downloaded zip file to your system
  3. The bundle includes a small bootstrap script that can start Activator. To start Lightbend Activator's UI:

    In your File Explorer, navigate into the directory that the template was extracted to, right-click on the file named "activator.bat", then select "Open", and if prompted with a warning, click to continue:

    Or from a command line:

     C:\Users\typesafe\finagle-quickstart> activator ui 
    This will start Lightbend Activator and open this template in your browser.

Option 3: Create a finagle-quickstart project from the command line

If you have Lightbend Activator, use its command line mode to create a new project from this template. Type activator new PROJECTNAME finagle-quickstart on the command line.

Option 4: View the template source

The creator of this template maintains it at

Option 5: Preview the tutorial below

We've included the text of this template's tutorial below, but it may work better if you view it inside Activator on your computer. Activator tutorials are often designed to be interactive.

Preview the tutorial


Finagle is an extensible RPC system for the JVM, used to construct high-concurrency servers. Finagle implements uniform client and server APIs for several protocols, and is designed for high performance and concurrency. Most of Finagle’s code is protocol agnostic, simplifying the implementation of new protocols.

This example demonstrates a simple server and client communicating over HTTP.

For more information, see the full documentation.


A Finagle server defines services and filters. Services are functions from a request type (HttpRequest) to a Future of a response type (HttpResponse). Put another way: given a request, we must promise a response some time in the future. In the example app, we just return a trivial HTTP-200 with a message in the body and a custom HTTP header, using the same version of HTTP with which the request was dispatched.

Filters are also simple functions used to implement additional behavior. In this case, we check for a custom header provided by the client and add it if it's not provided. Filters and services compose with the andThen method.


Finagle clients work the other way around: we’re given a Service to use. In the example app, the client is a Service to which we can dispatch HTTP requests and in return receive a Future[HttpResponse] — the promise of an HttpResponse (or an error) some time in the future. We construct 2 HTTP requests, one with a custom header and one without.