A talk by Jacob Maine about collecting, analyzing and presenting very large amounts of data. Introduces the problems of big data, mentions some of the relevant technologies and gives a bit of advice about designing solutions.
Urban Dictionary is a Ruby on Rails application and the 109th most visited site in the country according to Quantcast. Today it runs entirely in the cloud — on Heroku, AWS and Akamai — and per-user costs are lower than ever. Founder Aaron Peckham discusses recent infrastructure changes to the site, the costs and benefits of each change, and tricks to minimize risk while making changes to a large site.
Dart is more than a new structured web programming language. Google’s Dart Developer Advocate, Seth Ladd, talks about the philosophy and motivation for this new open source developer platform. There’s an overview of the language, libraries, and tools that help developers from all platforms build apps for the modern web.
Responsive web design is about a lot more than the size of your screen. Kyle Neath, Director of Design for GitHub, talks about about how GitHub handles links, the url bar, partial page updates, and explains why he thinks the HTML5 history API is the most important thing to happen to front end development since Firebug.
Agile brings the idea that when designing a product, collaboration produces better results than conflict, but all too often a familiar us-vs-them war breaks out between developers and operations. Devops is a buzzword, but in reduction it means putting the people in charge of writing the code in charge of keeping it running. Pivot Matthew Kocher attempts to convince you that you want to run your own site, and teaches you a little bit about how to do it.
Pivotal is proud to announce the release of the databasedotcom gem. Developed in partnership with Heroku and Salesforce, this gem wraps the Force.com REST API in familiar Ruby idioms, making it a snap to create web applications that integrate with your existing Salesforce instance, or even straight Ruby apps that do offline analysis of your Salesforce data.
I will be giving a session at Dreamforce on Tuesday, August 30, introducing the gem and demonstrating how easy it is to integrate into a Rails application. The session is entitled Building and Deploying Great Applications with Salesforce, Ruby, and Heroku, and takes place in Moscone West Room 2008 from 5:00 pm – 6:00 pm.
Hope to see you there!
The Ugly Truth
On a recent project, we had an ActiveRecord model that declared some relationships and callbacks like so:
belongs_to :credit_card before_create :build_credit_card
The intent was that
build_credit_card would build the associated
CreditCard instance, and ActiveRecord’s default
:autosave feature on the
belongs_to would save it.
What we discovered was that no
CreditCard object was being persisted. We confirmed that
:autosave is on by default for
belongs_to relationships, so we couldn’t immediately understand why the new
CreditCard wasn’t being created.
Googling proved futile, so we dove right in to the ActiveRecord source- and boy did we have a good laugh about 10 minutes later.
What we found was that the
:autosave option works by simply declaring a
before_save callback- that makes perfect sense.
In our case, however, we were building the object to be autosaved in a
before_create callback, which ActiveRecords runs after the
before_save callbacks (cf. the callback ordering docs).
So our first problem was that we needed to move the call to
build_credit_card from a
before_create callback to a
before_save :on => :create callback.
Did you catch that? There is a difference between
before_save :on => :create. A big difference.
While I understand the how and why of this, the semantics don’t make it obvious. So beware!
Now with our declarations changed to
belongs_to :credit_card before_save :build_credit_card, :on => :create
We ran our tests again, and, still, no love. Ahhh, we’ve still got an ordering problem. In addition to the ordering semantics detailed in the docs, ActiveRecord also runs callbacks within a single group in the order in which they are declared. So, even though we changed the call to
build_credit_card to occur in a
before_save, it was still occurring after the
before_save callback, because of the declaration order.
Finally, we changed our declarations to
before_save :build_credit_card, :on => :create belongs_to :credit_card
and our tests were happy.
autosavewith any ActiveRecord association, be very careful of callback ordering if you are building or modifying the inverse objects using ActiveRecord callbacks.
before_createisn’t ever the same thing as
before_save :on => :create, even if it sounds like it should be.
Since this article was written, version 1.7.0 of WebMock has been released, which includes WebMock.disable! functionality, as well as fixes the problem with selenium-webdriver. So please use that, instead of webmock-disabler.
Recently, one of my projects ran into a problem where our integration tests would intermittently fail with weird timeout errors and complaints about page elements that couldn’t be found.
A little googling revealed that we weren’t the only ones having this problem.
Apparently, WebMock, Selenium, and WebDriver don’t play nicely together, even if you tell WebMock to allow the outgoing connections necessary to drive the browser.
Some Gemfile hacking revealed that it was the mere presence of WebMock that caused the error. If we removed WebMock from our Gemfile, our integration tests ran fine, but then of course all of our tests that actually needed WebMock failed.
At that point, we could have decided to run our integration tests separately from the rest of the tests, but we really liked the idea of having all the tests run in the same VM, to avoid the duplicate VM startup time.
What we really needed was a way to turn WebMock on and off selectively for different types of tests.
With some gnarly monkey patching and offensive use of
alias_method, I have created webmock-disabler, a gem which provides new
WebMock.enable! methods. You can use these methods in individual tests, or on classes of tests as shown in the README.
We’re now able to run our tests that need WebMock in the same VM as those that would otherwise break if we didn’t do
RSpec 2.5, Capybara, and Selenium
:js => true option.
However, doing do requires the very latest Capybara, so be sure to specify the
:git option in your Gemfile.
Ryan Bates has done an excellent RailsCasts episode on just this.