A Sinatra and Redis app - does one Twitter user follow another?
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Who Follows?


A simple Sinatra/Redis app - does one Twitter user follow another?

This is a refactored and improved version of the app built for RailsConf 2011 by Charles Lee.

There is an example deployed at http://twhofollows.cfapps.io


This example uses:

It demonstrates:

  • setting the location of static content with Sinatra
  • the use of layout templates
  • how a Cloud Foundry manifest can be used for deployment

Deployment to Cloud Foundry

First, fork the project. Then run:

git clone git@github.com:<your_name>/sinatra-cf-twitter.git whofollows
cd whofollows
cp manifest.yml.example manifest.yml
vi manifest.yml

Edit the application name in the manifest file to be a unique value (an appname must be a unique name across all applications running on a Cloud Foundry instance); enter a Redis service instance name; enter your Twitter app API keys; then save the file.

bundle install
cf create-service rediscloud 25mb <service-name>
cf push

Visit http://appname.cfapps.io and run some queries.

To see the use of multiple instances, refresh the page (the initial manifest specifies 2 instances). The port displayed at the end of the page will vary.

To modify, run cf scale -i n (where n is the number of instances of the app to create), and then reload the page. Repeat with a lower value of n to reduce the number.

To clear the database cache, hit the /cleardb endpoint.


The following issues are known:

  • lack of strong error handling -> currently if one or both user IDs don't exist, a "page does not exist" error is shown
  • Twitter API limits only return the first (100?) users in the list of friends/followers, so if a user has many thousands of followers it may not work (Ruby gem and Twitter API hard limits)

Future enhancements

A few areas could be tided up:

  • better error handling
  • no real need for the query to direct to a separate page, make this dynamic
  • add a static page with some background information on how it works
  • nicer mobile support (hide fork me banner)