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:
- Twitter Ruby gem
- Sinatra as the framework
- Redis as a cache/datastore
- Bootstrap for visual loveliness
- the latest version of the cf CLI
- 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 email@example.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
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)
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)