A high-performance proxy server is less than a hundred lines of Ruby code and it is an indispensable tool for anyone who knows how to use it. In this session we will walk through the basics of event-driven architectures and high-performance network programming in Ruby using the EventMachine framework.
Ben Stein of Mobile Commons is giving a talk on Cross-platform Mobile App development. They hadn’t done any client mobile work, but lately clients have been asking “what about iPhone?,” “what about Android?” and the like. Whether or not this question of navigating the mobile client world is important to you now, Ben predicts it will soon be, as that’s where we’re headed.
Thoughts and experiences from Mobile Commons’ first mobile client apps:
Mobile give you capabilities not available elsewhere:
- Accelerometer & Orientation
- Phone & Contacts
- Sound & Vibrate
This is a big list – serious stuff.
Uncool things about mobile
- Unreliable network connectivity
- Java, Objective-C
- Memory Management
Options for mobile
- Maybe your Rails Web app is good enough
- A mobile-formatted version of the web site
- A client app
- alternate stylesheets
- separate mobile subdomain
- No cool mobile features
- No app store distribution
** have to bookmark, no $$
iui, iPhone, Rails
- iui & rails-iui: gives you stylesheet and typical iPhone ajaxy interaction
- Mime::Type.register ‘text/html’, :iphone
- Rich User experience
- Cool device features
- App store distributions
Native Apps: Cons
- New technologies
- Different technologies
- Frameworks to learn
“There are only so many hours in the day to learn new technologies.”
Alternative Tech Stack
- Webkit rendering engine (HTML/CSS)
- Business logic in web application
(accelerometer, location, phone, &c.)
- HTML5 Client-Side Storage (SQLite + JS)
- Proposed 6 years ago, working group started in 2007. Implementations emerging, particularly in Webkit, which is the common mobile renderer.
- Video Tag
- Client-side Storage
- and more…
3 Types of Storage
- Structured Storage
- Client Database
HTML5: App Cache
Also defines a mechanism for enabling intelligent client-side caching.
- Defines an interface for client-side databases
Ben then demos a sticky-note app which works currently in Safari, and works with client-side persistent storage.
Security & Privacy
This makes cookie resurrection easy, so the designers include a same-domain policy in the spec, to reduce access.
GMail on the iPhone
Currently uses the app-cache and asynchronous updates to enable offline access.
- Open-source Project by Nitobi
jQuery minus all the browser compatibility code, optimized for Webkit & Mobile phones.
Don’t use Curl to test these apps, use HttpClient, which deals with much of the basics, including authentication
The phone number is linked with the a ‘tel:// ‘ URI which then allows initiating a call from within the phone.
These projects can be built and managed out of eclipse for Android and XCode for iPhone.
- Apps don’t quite feel native. A bit slower, not quite as polished.
- Not good for graphics, games, &c.
- App store policies? Reports that some apps have been rejected for using these frameworks.
- HTML5 spec not yet finalized
- Tons of fun work to add HTML5 functionality to Rails
Q & A
What about Migrations?
There’s no easy answer, this is one of the reasons we switched to Web development, because we have more control and the easy ability to push updates. Client migration support is also theoretically possible, but has yet to be implemented.
Have you ever tried to catch a train running at a million miles an hour? Jumping into the traffic stream at Wikipedia is an insane adventure I’ve been going through. Exactly how do you launch a new platform that could instantly have millions of hits in a few hours? How do you do that and not spend 3 years researching? A fun tour of how I got Ruby at Wikipedia and did it with confidence, bravado, and alcohol. There will be cussing and lots of funny stories that should be highly educating and an insight into my technical philosophies.
This talk will present the TrustTheVote project and the “I count!” movement. It will cover the technology roadmap, progress so far, and next steps, including expansion of development efforts and opportunities for involvement in design and construction of trustworthy voting technology that everyone will be able to see, touch, and try—technology that will be fully federally certified and have the endorsement of the States’ elections directors through a unique approach that can ensure widespread adoption. If you have ever wanted to know what you can do to make a difference in our electoral process, then this talk is for you.
- Single Responsibility
- Open Closed
- Liskov Substitution
- Interface Segregation
- Dependency Inversion
All of Sandi’s code is available here.
Fact: your application is going to change. How will your application handle that change?
Robert Martin says your app can behave a couple of different ways:
- Rigid: Making a change somewhere will break something somewhere else.
- Fragile: You can’t predict where that break will be.
- Immobile: It’s hard to change your code.
- Viscous: It’s easier to do the wrong thing than to fix things.
In the beginning, though, your app was perfect. “Dependencies are killing you!”
Design might save you.
The Design Stamina Hypothesis says that, after a certain point, you’ll have done better if you had designed first.
“Skip design, if you want your app to fail.”
To avoid dependencies, your design should be:
- Loosely coupled
- Highly cohesive
- Easily composable
- Context independent
SOLID principles we can ignore in ruby:
Really only a problem for statically-typed, compiled languages. Because we’re in Ruby, we don’t have this problem! Win!
“Dynamic languages obey this rule in the most extreme way possible: duck typing.”
When you design, don’t break the contract of the superclass in the subclass.
Sandi draws her examples of applicatoin change from the source code at: http://skmetz.home.mindspring.com/img28.html.
Lesson #1: Resistance is a Resource.
- Don’t be attached to your first idea
- Embrace the friction
- Fix the problem
If testing seems hard, examine your design. Tests depend upon the design of the code. “TDD will punish you if you don’t understand design.”
During refactoring, ask yourself:
- Is it DRY?
- Does it have one responsibility?
- Does everything in it change at the same time?
- Does it depend on things that change less often than it does?
The answers should all be ‘yes’.
Sandi references her code to demonstrate when and how to mock and use dependency injection to achieve Single Responsibility, in which a class both downloads and acts upon the downloaded data.
She urges developers to do the simplest possible refactoring when extracting responsibilities from a class.
“Refactor, not because you know the abstraction, but because you want to find it.”
Sandi uses a very interesting example of building a Config class which behaves differently in different Rails environments. The first version had a lot of smell, and with a combination of hash parameters, YAML file, and metaprogamming, she demonstrates how to be open for extension, but closed for modification.
Sandi explains that paying attention to your classes’ dependencies is important. If a relatively static class is dependent on a class that changes more often, that’s a smell! Use dependency injection to avoid Dependency Inversion.
“TDD, BDD and DRY are all good, but they are not enough.”
“Design because you expect your app to succeed, and the future to come.”
Sandi recommends reading:
In this session, David Stevenson explores how to run untrusted code inside a ruby application using a sandbox. With this powerful technique, users can upload code that integrates as part of a larger application, making it ideal for custom business rules, dynamic games (think SecondLife), and science/math applications. Ruby’s english-like syntax and ease of creating DSLs makes it a good scripting candidate for non-technical people.
Sinatra has been getting a lot of attention lately as the next great (micro-)framework. In writing apps, diving in, and contributing the reasons for its existence have become more clear. Sinatra is not just a toy or a neat trick, its the best way to create simple and non-obtrusive web interfaces to sit on top of a new or existing Ruby codebase. I’ll walk through the whats, whys, and tools for getting started with Sinatra.
Over lunch with Jake, I’d wondered aloud “where are all the wide-eyed optimistic presentations?” and Jake starts by saying he’s sorry that this will not be one of those talks.
We’ve been programming in Rails for several years now, and now more than ever we’re left with the problem of how to deal with, maintain and correct projects which may be riddled with out-dated thinking, mistaken ideas and problematic implementations.
In other skilled enterprises there are core ideas which are repeated by for practice and for their general utility. In martial arts, these are called “katas,” in programming, we have “patterns.” Patterns are general, reusable solutions to common problems in software engineering, which are often arrived at through emergent design. Anti-patterns, likewise, emerge in the general work on a project, but their presence is harmful. They’re the mistakes we make again and again in our projects.
Jake then laid out a few patterns and anti-patterns for your consideration:
1. Know your APIs
Some of the most egregious anti-patterns come from simple ignorance about the APIs available, and the consequential re-implementation of basic Ruby or Rails functionality. The Rails and Ruby APIs are both well-documented and important to your work. There’s no excuse not to know them.
2. script/plugin and gem installitus
While we must install a plugin or gem to use it, often we move on without doing the important job of cleaning up after ourselves.
- if not self.value.nil?
People litter ‘self’ all over the place. The only place you need self is on assignment. And all this could be replaced with the simple line:
- @value = 600 if @value.nil?
@value ||= 600
- some_value == nil?
What does this even mean? ‘nil?’ is false unless inside NilClass
- IRB-driven Design
Occasionally we hack away in IRB and, once we get the results we’re looking for, drop the code into our app without a second thought. This can produce some very buggy, obtuse, far-from-minimal code. Once we discover a mechanism, better to revisit the problem and produce the code in a more stable context.
Confusing. Not to be used outside of a predicate method.
4. Planning is Hard
Will you remember what your boss tells you to do a year ago? Will you unknowingly violate these past decisions and understandings? To avoid doing so it’s important to maintain active specs against your app.
Jake recommends Cucumber + Webrat for carrying this out.
5. How Bad Is It?
There’s a gem called metric_fu, a gem full of analytics. One in particular is known as Reek, which sniffs out code smells.
Run reek against your app, and it will find long methods, for example, and return all of the methods that are longer than 5 lines. And you can make your tests fail on the existence of these methods, to keep yourself and your team in check.
Orphans are methods, models, views or controllers, or any other bit of functionality which is disconnected from the rest of your app. Like un-used plugins or gems, orphan code is noise which keeps your code from being easily maintainable.
We can look to the more modular, merb-style project organization as a way of better structuring our projects. Likewise the Fat-model, Thin-controller design pattern helps us to create easily-testable, well-organized apps.
- The valueless test
assert_equal 2, User.count
This test fixtures, and activerecord, and its very presence hinders us by interfering with our view of more meaningful tests.
- The slow test
Any slow test has a cost of both slowing the testing feedback loop and making it less likely that we’ll run the tests as often as we should.
- The coupled test
Coupled tests mean that a test depends on the side-effects of other tests, or on the effects of an outside service or application. Instead we can mock out the outside web service or operation
- Complex tests mean complex code
9. Make Decisions and Document Them
Discuss your code conventions and style with the team, settle on a set of best practices, and write them down. Store them in a style guide in the project root or document directory.
10. Continuous Integration
Jake recommends using Integrity Continuous Integration Server. Whether you use that or Cruise Control, or any other option, continuos integration insures your specs and tests are frequently and consistently run.
11. Build Artifacts
Generating and maintaining build artifacts, such as statistics reports from your reek run or performance tests can enable you to track your progress over time. In addition, you put minimal expectations on these
12. Reviews and Retrospectives
Taking time every few months to review your recent progress, and discuss problems and progress.
Q & A
Someone mentions a particularly egregious example of a test which deleted its own application code in the process of running.
Jake responds that in cases where tmp deletion and file generation, it may be appropriate to have a safe version of the test which runs locally, and a separate exhaustive test which runs in a sandbox staging environment. This allows you to exercise the more dangerous tests in a safe environment.
Yehuda mentions one way to do this is to mock in the safe version, and turn of that mock in the sandbox environment.
Jake then shows a 45-line login method and points out how difficult it is to immediately grok. Newer-code built in the REST-ful style is much simpler to work with.
By discussing these approaches with old-hands and newbies alike, we can all improve the quality of our code, spend less time dealing with bugs or code comprehension, and more time building out the next great Rails projects.
A Brief History
Ruby web development came of age with MVC and Rails. Later, people who didn’t need a full MVC invented Sinatra and other frameworkes. Which brings us to today, and …
Waves can do simple apps in just a few lines of code. And by using “foundations”, developers can build more advanced apps with MVC-like functionality. You can build your own foundation for whatever web framework you envision (there are several for MVC and REST).
Waves supports rack::cache and JRuby. It’s Actually In Production(tm)!
Web as Services
As more rich browser apps use AJAX and COMET, server-side APIs are becoming more important. This is where REST shines.
“HTTP isn’t MVC, but our frameworks think in MVC.”
REST and ROA
“REST” shouldn’t be applied to things that are “REST-influenced” (just ask Roy). Dan likes to use “Resource-Oriented” for these situations.
HTTP-based ROA uses the existing infrastructure, and has proven scalability. HTTP defines a protocol for a distributed hash table:
- put(key, value)
Q: “What about post?” A: “Post is for ‘everything else’.” Some things aren’t clearly RESTful, and post is the catch-all for other operations.
What’s in the hash? Resources, and keys are the URIs.
What’s the point? Platform-neutral distributed objects! RDF can be used to describe discoverable resources.
ROA in action:
rss/atom. It’s one link to a resource describing your blog. “Boom! Podcasts for free.” Dan describes this as the law of “unintended consequences,” in a good way.
Edge caching is another big win for HTTP-based ROA.
How Does Waves Help?
Waves makes it easier to write resourceful applications like this today. New foundations will make it even easier going forward.
You can check out Waves at http://rubywaves.com, and on their Google Group.
Eleanor McHugh, a physicist by training, will be talking about how to make *nix systems work naturally within the Ruby environment.
The Unix Way
Eleanor actually hates Unix, but recognizes that it’s a very effective operating system for getting things done. It’s DRY: build little things, build them well, don’t build them twice. There’s a natural marriage between agile Ruby and the Unix philosophy.
Unix provides basic services which make it a very useful OS to “muck about with”:
- virtual memory
- process management
- hierarchical file system
- user permissions
- interprocess communication
Ruby provides some “really lovely” utilities:
However, if you’re doing a lot of IO, you end up doing a lot of
select()s and keeping a lot of file descriptors open.
System Calls with Ruby DL
DL, which Ruby delivers out of the box, is a way to wrap a C library with a Ruby call. This is a nice way to access the underlying kernel system calls without relying on the Ruby IO implementations.
This is superior to Ruby’s
syscall, in that you can actually get results back from the function call.
mmap allows you to do much faster memory reads, rather than do slower file reads.
inotify allows you to build evented ruby (like EventMachine, but without EventMachine).
Using pipes allows you to build efficient IPC.
The drawback is that using DL means more verbose code, and more error prone code. (Pointer math FTL!) So, for things like sockets, use the Ruby API unless you specifically need kernel-level eventing.
The lack of real thread support in Ruby can be addressed by using multiple processes, held together with IPC (sockets, pipes, memory mapped files). This is the traditional “Unix way” for handling multiple processes.
Moving to 1.9
On Ruby 1.8, strings are sequences of bytes. On Ruby 1.9, strings are proper characters (not bytes!). Even if your app only speaks “American”, you still need to be aware of this to handle data properly. Plus, some of the new syntax in 1.9 is not backwards compatible with 1.8.
Recommended steps for upgrading from 1.8 to 1.9:
- make sure you have good test coverage!
- make sure your test are checking the output (some end-result validation)
- run on 1.9
- hammer on your code until the tests pass
- decide whether to continue to support 1.8
Prawn only officially supports 1.8.6 and 1.9.1 to make life easier, but if support more versions is necessary for your project, check out ZenTest’s multiruby features.
Greg recommends using conditional-execution blocks to make version-dependent code look nicer:
if RUBY_VERSION < "1.9" def ruby18 yield end else def ruby18 end end
Greg opines that moving to Ruby 1.9 is not a magic bullet, but has lots of advantages, so try it out!
Ruby 1.8.6 is a workhorse (insert image of beat-up pickup truck). Ruby 1.9 is a Lamborghini (we think). “What the hell is 1.8.7?”
Answer: 1.8.7’s patch set is largely 1.9 backports. It’s a platypus!
However, this doesn’t mean that code written for 1.9 will magically work on 1.8.7. Or that code written for 1.8.7 will work on 1.8.6.
What should authors be doing? Should we release for 1.8.6 or 1.8.7? Greg recommends releasing for 1.9, especially if you’re writing a Ruby book (wink wink).
FFI (Foreign Function Interface) is supported “all over the place”, and is an alternative to writing a C extension. FFI works across implementations (JRuby, Rubinius, and MRI).
On Windows, Greg proclaims that JRuby is the easiest way to wrap a C library. “WTF?”
Oversimplified Explanations of Ruby Variations
According to Greg. (Not all of the nuance may be captured here, since Greg was moving pretty quickly. Blame me, not him.)
- 1.8.6 is ubiquitous, and may be slowing adoption of other, better interpreters.
- YARV (1.9) is faster than Matz’s implementation and is the only complete m17n implementation of Ruby.
- Ruby Enterprise has a great installer!
- JRuby is great and new, but requires C extensions to be rewritten
- Rubinius is what created the RubySpec project and FFI, and is very innovative.
- MacRuby is, um, Ruby for Macs.
We have a winner in the Pivotal Tracker GoRuCo Haiku Contest.
Collin Miller submitted the winning entry:
Rivers of Action
Clearly Sculpt a Way Forward
My Path is Now Clear
We thank everyone for participating. There were a number of great entries, but this piece really stood out.
Collin, come on down tomorrow and say hi. I’ll be there all day enjoying the conference with some other folks from Pivotal Labs and demoing Pivotal Tracker for anyone who doesn’t know it already. Congratulations on your win!