dcsimg
LinkedIn
Google+
Twitter
RSS Feed
Download our iPhone app
TODAY'S HEADLINES  |   ARTICLE ARCHIVE  |   FORUMS  |   TIP BANK
Browse DevX
Sign up for e-mail newsletters from DevX

By submitting your information, you agree that devx.com may send you DevX offers via email, phone and text message, as well as email offers about other products and services that DevX believes may be of interest to you. DevX will process your information in accordance with the Quinstreet Privacy Policy.


advertisement
 

Move Over Rails. Here Comes Merb. : Page 3

Merb is potentially much faster than Rails, and the combination of Merb and Ruby can provide the performance most web apps require. Find out how Merb can deliver a 2-4X speed increase over Rails and why that makes it better for certain applications.


advertisement

WEBINAR:

On-Demand

Building the Right Environment to Support AI, Machine Learning and Deep Learning


Using DataMapper and a Database for Rendered Feed Data
To read all of the seed RSS URLs and fetch the RSS feed XML for each seed RSS URL, I created a model class FeedDataManager that reads the feed_sources database table using the DataMapper-generated class FeedSource. You can look at the source file app/models/feed_data_manager.rb for the full implementation, but the following few code snippets show how you fetch and process RSS data:

feed_sources = FeedSource.all.collect {|f| f.url} feed_sources.each {|source| puts "\n* * processing #{source}" begin rss = SimpleRSS.parse(open(source)) rss.items.each {|item| puts " link: #{item.link} title: #{item.title} feed title: #{rss.feed.title}" # item.context # all content text # save data to database feed = Feed.new feed.url = item.link feed.title = item.title feed.content = item.content feed.feed_name = rss.feed.title feed.posted_date = Time.now feed.save! puts "* saved #{feed}" } rescue print "Error: #{$!}" end }

Running this periodically in the background, the ideal implementation, is relatively easy. Merb has built-in support for running background tasks from controllers, but I wanted to do something different: start a work thread as soon as all application code has loaded. To do this, I edited the config/init.rb file by adding a statement to the run after loading block:



Merb::BootLoader.after_app_loads do # This will get executed after your app's classes have been loaded. DataMapper.setup(:default, "sqlite3://#{Dir.pwd}/dev.db") # Start up the background work thread: Thread.new { FeedDataManager.new } end

The initialize method for class FeedDataManager never returns. Rather, it initializes instance data and enters a long loop that fetches feeds, and then the thread sleeps for five hours before re-fetching the feeds.

Now you need a controller to get the feed data for a view (note that I have removed the unnecessary controller methods that merb-gen resource feeds ... created):

class Feeds < Application # provides :xml, :yaml, :js ## do not need to handle web service clients def index @feeds = Feed.all display @feeds ## make available to the view end end

My initial edits for the app/views/feeds/index.html.erb were:

<h1>Latest Ruby Blog Entries</h1> <% @feeds.each {|feed| %> <h4> <%= feed.title %> </h4> <a href="<%=feed.url%>" target="new">link</a> <%= feed.content[0..70]%> <br/><br/> <% } %>

Finally, before running the first implementation, I wanted to set the method index in the controller class Feeds to be the default route for the web application in config/router.rb:

match('/').to(:controller => 'feeds', :action =>'index')

That is pretty much bare bones, but you now have a complete web application (that you will improve) for fetching feeds and displaying them.

One thing that surprised me when I first ran this prototype was its speed. It was fast without caching and despite database fetches for the data it would display. I ran the Apache Benchmark utility and discovered that this prototype provided 44 page renders per second on my MacBook:

ab -n 5 http://localhost:4000/

The next section explains how you can change the design of the demo application to incorporate in-memory storage.



Comment and Contribute

 

 

 

 

 


(Maximum characters: 1200). You have 1200 characters left.

 

 

Sitemap
Thanks for your registration, follow us on our social networks to keep up-to-date