Typesafe Activator

Event Driven Redis Twitter Clone

Event Driven Redis Twitter Clone

pkinsky
Source
November 16, 2014
playframework angularjs redis scredis scala akka websockets

A Redis-backed event-driven Twitter clone built using the Play Framework, Akka, AngularJS and websockets.

How to get "Event Driven Redis Twitter Clone" on your computer

There are several ways to get this template.

Option 1: Choose redis-twitter-clone in the Typesafe Activator UI.

Already have Typesafe Activator (get it here)? Launch the UI then search for redis-twitter-clone in the list of templates.

Option 2: Download the redis-twitter-clone project as a zip archive

If you haven't installed Activator, you can get the code by downloading the template bundle for redis-twitter-clone.

  1. Download the Template Bundle for "Event Driven Redis Twitter Clone"
  2. Extract the downloaded zip file to your system
  3. The bundle includes a small bootstrap script that can start Activator. To start Typesafe 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\redis-twitter-clone> activator ui 
    This will start Typesafe Activator and open this template in your browser.

Option 3: Create a redis-twitter-clone project from the command line

If you have Typesafe Activator, use its command line mode to create a new project from this template. Type activator new PROJECTNAME redis-twitter-clone on the command line.

Option 4: View the template source

The creator of this template maintains it at https://github.com/pkinsky/ClockworkSemaphore#master.

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

Introduction

This project is an implementation of the Redis-based Twitter clone described in this case study

" In this article I'll describe the design and implementation of a simple clone of Twitter written using PHP with Redis as the only database. The programming community has traditionally considered key-value stores as a special purpose database that couldn't be used as a drop in replacement for a relational database for the development of web applications. This article will try to correct this impression. Our Twitter clone, called Retwis, is structurally simple, has very good performance, and can be distributed among any number of web and Redis servers with very little effort. "



I encourage you to read the above case study, which describes the redis schema used in detail. The following tutorial pages contain links to the major components of this app, with short descriptions of their role. The bulk of the documentation is inline, in the form of comments.

Main page

Users can view their personal feed, view the global feed, post tweets and favorite/unfavorite other users from here. This page is made up of several components.
  • index.scala.html: presentation layer of the main page. Uses AngularJS bindings to encapsulate presentation logic.
  • main.js: AngularJS controller for the main page.
  • SocketActor.scala: Akka actor which handles the server side of the Websocket connection. Uses Redis PubSub to listen for tweets of interest to users with active websocket connections.
  • App.scala: controller which constructs and serves the main page to authorized users.
  • Websocket.scala: controller which provides a Websocket connection to authorized users.
  • Api.scala: controller which handles API requests from authorized users to follow and un-follow other users.
  • Auth.scala: Request builders used to ensure only authorized users can access the above components. Encapsulates authorization logic.

Landing page

Users without authorization cookies are redirected to this static page, where they can either login to their existing accounts or register a new account.

Redis

The Redis service provides nonblocking interaction with Redis.
  • RedisService.scala: Global object which encapsulates interaction with Redis. All methods are fully nonblocking.
  • RedisSchema.scala: Base trait containing strings used as Redis keys and functions for converting domain objects (UserId, PostId, etc.) into Redis keys.
  • RedisConfig.scala: Base trait which encapsulates Redis configuration and initialization of Redis clients.
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