how to build single page html5 apps that scale
DESCRIPTION
Developing large apps is difficult. Ensuring that code is consistent, well structured, tested, maintainable and has an architecture that encourages enhancement is essential. When it comes to large server-focused apps, solutions to this problem have been tried and tested. But, how do you achieve this when building HTML5 single page apps? In this talk we’ll cover the signs to watch out for as your HTML5 SPA grows and provide examples of some of the tooling types that can contribute-to as well as ease the growing pains. Finally, we’ll demonstrate how tooling can be used to support a set of conventions, practices and principles that enable a productive developer workflow where the first line of code is feature code, features can be developed in isolation, code conflicts are avoided by grouping assets by feature and features are composed into apps. The demonstrations will use BladeRunnerJS, an open source developer toolkit written in Java, but the concepts are widely applicable.TRANSCRIPT
@leggetter#HTML5AtScale
How to Build Single Page HTML5 Apps that Scale
Phil Leggetter @leggetter Caplin Systems
@leggetter#HTML5AtScale
bladerunnerjs.org
Open Source
What is a large-scale Single Page HTML5 App?
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–Addy Osmani, Patterns For Large-Scale JavaScript Application Architecture
In my view, large-scale JavaScript apps are non-trivial applications requiring significant developer effort to maintain, where most heavy lifting of data
manipulation and display falls to the browser.
Large CodebaseMore functionality === More code
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Caplin Trader• SDK:
• ~1,000 JavaScript files
• ~131,000 LoC
• ~131 lines per file
• ~650 test files
• ~95,000 test LoC
• Typical Apps:
• ~425 JavaScript files
• ~50,000 LoC
• ~117 lines per file
• ~200 test files
• ~21,000 test LoC
Complexity
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Gmail & Caplin Trader• Large Single Page Apps (SPAs)
• Complex functionality
• Complex interactions
• User
• Technology
• Leave open all day
Features: Change, Come & Go
Feature Progression
ContributorsThe Human Factor
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Who contributes to an app?• Front-end devs
• Back-end devs
• Designers
• QA
• Infrastructure and release engineers
• Technical authors
• Multiple teams
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Maintainable?1. Massive codebase
2. Architecture
3. Contributor harmony
4. Promote quality
5. Productive developer experience
6. ^All complimentary
The Solutions
1. Components/Widgets/Modules/Features
2. A Services Layer
3. MV*
4. Efficient Testing
5. Tools to Support Workflow
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Prov
e it!
Feature ==> Blade
Finding assets is hard
/assets /feature-name
Long App Reloads
Image of app partially workingWho Broke the App?
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Features• Can run in isolation
• Unaffected by breaking changes elsewhere
• Fast reload times
• Easy to find & change assets
Compose Components/Modules
into Apps
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Adding features to Apps
Services
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What is a service?• Use services to access shared resources
• In-app inter-component messaging
• Persistence Service
• RESTful Service
• Realtime Service
• Services are a Contract/Protocol/Interface
Setting & Getting Services• Use a unique identifier for each service i.e. a simple string
• Register (code or config). Code example:
!
• Get
http://martinfowler.com/articles/injection.html#ADynamicServiceLocator
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Why use services?
• Features should not directly communicate
• Easily change implementation
• Implementations can be injected for different scenarios:
• Workbench / Test / App
Fake Services
Fake/Stub/Mock Services
Real Services
Efficient Testing (We’ll get to MV*)
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~2009 Testing Requirements• Cross-browser IE6+*, Firefox 3.5*+ & Chrome
• Class-level Unit Tests
• Application Acceptance Tests
* Remember this was 2009
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Application ATs• Selenium Tests
• Selenium User-Extensions
• Actions, Accessors/Assertions & Locators
• VM infrastructure for CI
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AT Process
3
3. Launch browser + App
1
1. Pair Browser + Backend VM2
2. Reset & restart backend services
5
5. Record results
4
4. Execute ATs6
6. Reset backend services
8. Execute next test…
8
7
7. Restart/refresh browser
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Test Results• ~1300 UTs
• ~500 ATs
• 50 VM infrastructure to run tests concurrently
• 8 Hours
• Test results highly unreliable
• We could only run a full suite of tests once per day - at night
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Inefficient Testing!• Resetting back end services is too slow
• Lots of moving parts. Things can go wrong.
• Services don’t start = app won’t work. Not code but environment failure.
• We want to avoid IO
• … and querying the DOM
Don’t Touch that DOM
MVVM
End-to-End Module Testing
• Testing features in isolation
• Change view model and assert against mocked Service
• Inject fake service, make calls and assert View Model
Need Proof?Our full suite Caplin Trader
testing time went from
>8 Hours
< 30 minutes
Much less for a single feature
Tooling & Developer Workflow Focus on Features
What tooling offers?
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Automation
• Define workflow & promote consistency
• Scaffolding
• Dev Server
• Builds/Bundling
• Tests
Intelligence
Compliance
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Knowledge of Runtime Scenarios
• Workbench (dev-mode)
• Test
• App
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Dependency Analysis
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Customisation
• Augment workflow
• Identify allowable change to workflow
• Automation commands
• Builds/Bundling
• Test Runner
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Prov
en!
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Proven!1. Massive codebase - features
2. Architecture - features, services & MVVM
3. Contributor harmony - separation of concerns; codebase structure, features & architecture
4. Promote quality - features, services & MVVM
5. Productive developer experience - tooling
6. ^All complimentary - Yep!
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Thanks / Questions
•Phil @leggetter
•BladeRunnerJS
•@BladeRunnerJS
•bladerunnerjs.org