from nasa to startups to big commerce
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FROM NASA TO STARTUPS TO BIG COMMERCEBuilding Maintainable, Scalable Projects
DANIEL GREENFELD
SUCCESS!!!SUCCESS!!!SUCCESS!!!SUCCESS!!!
FAILURE.
Let’s get
started
I ❤ aerospace
(you’ve been warned)
BIGPLANS
http://en.wikipedia.org/wiki/Soyuz_(spacecraft)
The Reality
http://en.wikipedia.org/wiki/Conestoga_(rocket)
ConestegaFirst
commercial rocket!
1996!
https://www.flickr.com/photos/archer10/2215343914/
Early Design Mistakes
Early Design Mistakes
• Not understanding or knowing the requirements
• Over or under architecting
• Choosing the wrong tools
• Premature Optimization
• Management fiat made with ignorance or bad data
Technical
Debt
Loan Against the Future
• Get it done fast!
• Grouping data poorly
• Hardcoding
• Upcoming technology will fix it
• Leave testing and documentation for later
Technical Debt
Hard to Maintain Enhance Scale Projects
2006
Get It Done!!!
https://www.djangopackages.com/
Bad Practices@ PyCon 2011
https://www.flickr.com/photos/pydanny/5670716870/
Had mistakes at start
We insisted on rebuildReje
cted
Rebuilt and works great
Electronic Giftcards
Epic Volume
Our Challenge
Refactor
SUCCESS!!!SUCCESS!!!SUCCESS!!!
Challenges
Great Engineering Team
Scaling?
no-name projects
can go
viral
But even
So Many Things to Get Wrong
is a constant
Failure
But that’s okay
How Do We Build for the
Future?
Starting a Project
Greenfield Projects
http://commons.wikimedia.org/wiki/File:A_Green_field_in_the_countryside_-_geograph.org.uk_-_193455.jpg
Greenfield Projects
Or Greenfeld Projects?
Greenfield Projectshttp://commons.wikimedia.org/wiki/File:Green_fields_in_Gramado.jpg
Starting Basics
Kelly JohnsonReknowned and prolific aircraft design engineer
Invented Seriously Awesome Planes!!!
P-38 Lightning
http://en.wikipedia.org/wiki/Lockheed_P-38_Lightning#mediaviewer/File:Lockheed_P-38J_Lightning_-_1.jpg
U-2
http://commons.wikimedia.org/wiki/File:Usaf.u2.750pix.jpg
SR-71
http://commons.wikimedia.org/wiki/File:Lockheed_SR-71_Blackbird.jpg
Kelly JohnsonReknowned and prolific aircraft design engineer
AREA 51
Invented Seriously Awesome Planes!!!
Kelly JohnsonReknowned and prolific aircraft design engineer
AREA 51
Invented Seriously Awesome Planes!!!
Really Good Manager
Keep It Simple, Stupid
Kelly Johnson Said:
KISS
Kelly Johnson Said:
Keep It Simple, Stupid
Keep it Simple Stupid
Keep It Simple, Stupid
KISS
Kelly Johnson Said:
Keep it Simple Stupid
If Kelly Johnson kept it simple,
why can’t we?
Simple != Simplistic
Needless Complexity
is Bad
Bad ComplexitySwap two position values in a list
Simplicity is a VirtueFoundations: Simple
But not Simplistic
Feature Construction: Simple
Bug Fixes: Simple
Be careful with databases that make simplistic approaches easy.
JSON => SQL
Pro-Tip:
Keep management of data relations out of the code!
http://en.wikipedia.org/wiki/File:Map_of_USA_with_state_names_2.svg
http://upload.wikimedia.org/wikipedia/commons/thumb/b/b2/CourtGavel.JPG/600px-CourtGavel.JPG
http://commons.wikimedia.org/wiki/File:Benz-velo.jpg
Reasons to consider Non-Relational Databases
• Ephemeral Data (caching)
• Hierarchical Data
• Other data structures that don’t easily map to relations
• Seating charts (Eventbrite!)
• Organization charts in dysfunctional companies
Pro-TipWould it work in a spreadsheet?
relational databaseYES!
No! non-relational database
Simplicity isn’t always the answer
Sometimes you do need complexity
Right at the Beginning
Valid Reason for Complexity:
Database Transactions
Transactions aren’t complex, but engineers often think they are.Note:
http://commons.wikimedia.org/wiki/File:WinonaSavingsBankVault.JPG
http://commons.wikimedia.org/wiki/File:Okayama_Red_Cross_Hospital.jpg
Database transactions protect
finances and
lives
Valid Cause of Complexity
transactionsIf one operation fails,
revertrevertrevert
Don’t code solutions to handle
transactions
Use databases with transactions
PostgreSQL MySQL
Avoiding Database Transactions is Simplistic
You have to build special workarounds to make things reliable
You have to build special workarounds to make things reliable
Avoiding Database Transactions is Simplistic
You have to build special workarounds to make things reliable
Avoiding Database Transactions is Simplistic
Is a simplistic approach to avoid complexity…
A) Bad Design Decision? !
B) Technical Debt?
Answer
• Plan to fix later?
• Otherwise:
Technical DebtBad Design Decision?
More Thoughts
on Complexity
Complex Foundations: Harder to maintain
Complexity2=
Complex Foundations
Complex Business+
Complexity2=
Hard to Debug
Hard to Enhance+
Complex Code Causes Edge Cases
• Are you testing all the BRANCH (if/switch) statements?
• How do you test that ‘brilliant’ class heirarchy?
Your business logic is going to be enough complexity
Building finance project?
Spend your time making it make money?
Fighting the project’s design?
Don’t Get Fancy• Build a solid foundation first.
• “prototype” projects often aren’t.
• Beware virality
• No money
• Fancy stuff can come later.
Choosing Tools
Choosing Tools is
HardHardHard
Do it the Right Way
Management Fiat
Don’t Use Management Fiat
with ignorance or bad data
Mistake: Management FiatChoosing Enterprise Software
because it’s expensive
Your engineer’s recommendations !
!
!
!
!
vs
Expensive White Papers written by well-paid mostly non-technical analysts that
either state the obvious, expensive, or non-sensical
Mistake: Management Fiat
HIPAAHealth Insurance and
Accountability Act
Mistake: Management FiatWrong advice for
Your engineer’s recommendations
vs
Anything in a business management
magazine.
Mistake: Management Fiat
Salesperson’
vsThat person you just met who might
possibly has a vested financial interest in what they are recommending.
Your engineer’s recommendations
Mistake: Management Fiat
Your engineer’s recommendations when they constantly tell you how smart they are.
!vs
Burning your money in a fire.
Same result, but faster
Mistake: Management Fiat
http://commons.wikimedia.org/wiki/File:Burning-money-and-yuanbao-at-the-cemetery-3249.JPG
Your engineer’s recommendations when they want to continue using a 10+ year old legacy platform
vs
The Bus Factor
Mistake: Management Fiat
http://en.wikipedia.org/wiki/File:GMBus.jpg
http://en.wikipedia.org/wiki/Bus_factorBus Factor!
http://commons.wikimedia.org/wiki/File:Arriva_T6_nearside.JPG
Is documented?
Does the job?
Has traction?
Choosing tools
• Ignore corporate marketing hype
• Even for corporate open source projects
• Unless…
Choosing tools
It’s software for popular proprietary hardware
Toolkit Ecosystems
Is there an Ecosystem?
• Python, Django, Flask, et al
• Python package Index
• Django Packages
• Language + Framework means lots of optimized packages already exist to do much of the work.
Tools with traction have extendable components
Case Study:
5000+ for Django
46000+ for Python
Parallels
78K+
83K+
Don’t Reinvent the Wheel
http://commons.wikimedia.org/wiki/File:London-Eye-2009.JPG
Example: CMSDon’t build your own!
Unless your project is about reinventing wheels
http://commons.wikimedia.org/wiki/File:Triple_Rotacaster_commercial_industrial_omni_wheel.jpg
Pro-Tip #1Toolkit Ecosystems and Engineers
If engineers don’t know that tool ecosystems exist, consider them junior.
http://commons.wikimedia.org/wiki/File:Fawnpuppy.jpg
Educate them!
Pro-Tip #2Toolkit Ecosystems and Engineers
If engineers refuse to work with an ecosystem, !
don’t waste your time with them.
They purposefully lower the Bus Factor
http://commons.wikimedia.org/wiki/File:Keiseibus-twinbus-20071013.jpg
Best Practices
Insist on Best Practices
Cleaner Consistent Stronger Elegant CODE
Easier to Debug
Easier to Add Features
New Staff Ramp Up
FasterFasterFaster
How to Best PracticeResearch and find the common consensus
PEP-8
PEP-20
Example: Python
Find ReferencesResearch and find the common consensus
Research and find the common consensus
Find References
Research and find the common consensus
• MySQL
• PostgreSQL
• MongoDB
• Redis
• CouchDB
• Cassandra
• BigTable
Find References
Management Pro-Tip Part 1
If your engineers consistently refuse to follow defined best practices…
They purposefully lower the Bus Factor
http://commons.wikimedia.org/wiki/File:B43OleBillatIWMLondon.jpg
Management Pro-Tip Part 2
Get new ones
Tests
Always have them!
Even some coverage is better than no coverage.
Always have a working test harness
And a few tests that check really obvious things.
Add a test for every bug fix.
Every Programming Tool has Test Harnesses
Management Pro-Tip
Engineers who consistently refuse to write tests lower their bus factor to 1.
Prepare to keep them forever
http://commons.wikimedia.org/wiki/File:Ride_On_5312_at_Glenmont.jpg
Version Control
Works on every operating system
Tutorials and books everywhere
Just start with it or add it
We have no excuses not to use it!
Version Control Pro-Tips
Pro-Tip #1
Dropbox is NOT software-project-acceptable
version control!
Pro-Tip #2
An FTP server for backing up files isn’t either
Pro-Tip #3
Most good engineers won’t work on a project that doesn’t
have version control
Pro-Tip #4
Most good engineers won’t work at companies
without version control
Scaling
Scaling usually isn’t a problem
97% ChanceYou Ain’t Gonna Need it
A 3% Case
“Register here”
http://commons.wikimedia.org/wiki/File:President_Barack_Obama.jpg
Other 3% CasesA major celebrity tweets about your project
You are launching the official site for a blockbuster movie
You just go viral
What if your foundations are bad?
Bad Foundations
are Fixable
W. Lloyd MacKenzie, via Flickr @ http://www.flickr.com/photos/saffron_blaze/
With enough engineers, money, and headaches, you can fix anything
Two Quick Scaling Fixes
Based on the fact that the early scaling problems are almost always database-related.
It’s almost always about the data
First Fix: Caching
The first healthcare.gov patch implemented by their tiger team
added caching.
Second Fix: Indexing
Almost every datastore supports indexes.
Apply them to places with the most data reads.
The Big Scaling Mistake
to Avoid
Switching Tools Too Early
• Changing to the unusual datastore de-jour
• Trying a new programming language
• Switching out template languages.
• Changing Application Frameworks
before attempting to improve the database
Careful of the hypeReplacing Tools
mobile site
Went from Rails to Node.js. Giant Improvements!
!(A coincidence, perhaps?)
Node.js was just part of the story
They also modernized servers and added more.
Replacing ToolsCareful of the hype
Replacing FrameworksBut recognize excitement
Clearly Linkedin Engineers were excited to work with Node.js
Engineer interest in tools is important. It inspires us to do great things.
Management Pro-Tip
Uninspired Engineers don’t do the best work and are much more prone to leave.
Don’t Optimize Prematurely
Instead…
Follow Best Practices
By following best practices, you are laying a foundation that
makes scaling a project easier.
Long Term Scaling Fixes
Add More Servers
DevOps!
DevOps!Ansible
Puppet
Chef
Docker
Salt Stack
DevOps!
Catch: Devops != Cheap
Ansible
PuppetChef
Docker
Salt Stack
Pro-TipUndocumented DevOps lowers the bus factor of operations staff.
Prepare to keep them forever
http://commons.wikimedia.org/wiki/File:E85bus.jpg
Software as a Service
Heroku
Engineyard Google App Engine
Firebase
Various AWS Products
Gets Expensive
Software as a Service
Vendor Lock-In
Software as a Service
How to replace tools safely
Don’t switch all at once!
Version 4
Language Switches
Identify bottlenecks in the code
Try applying new language there.
Example Switches
Aim for giant speed boosts
• Numpy
• Scipy
• Pandas
Move slow big data/scientific calculations to:
More Example Switches
Port components to compiled languages such as:
• PyPy
• Go
• C
• Java
Aim for giant speed boosts
Maintenance Over Time
Case Study: Every Project
• Your project has been around for a while
• Problems
• Fixing bugs is hard
• Adding features is hard
Why is it harder?• Project is no longer the bright and shiny
• Adding features adds to complexity
• Bugs caused by unforeseen edge cases
• Not enough tests make catching developer introduced bugs harder
• Mistakes at the beginning are really starting to show
Original Engineer(s) was an Idiot
Original Engineer(s) are always idiots
I’ve yet to join a project where I didn’t feel like
ranting all the time
Rant Time!• Why use a relational database?
• Why not use a non-relational database?
• Why this programming language?
• Why not use OO or functional programming techniques?
• Why use OO or functional programming techniques?
• What the heck is this programming pattern anyway?
Caveat: The Constant of the Worst Code
Ever
Hindsight is 20/20
• No one predicts with 100% accuracy
• Not on software projects
• It’s easy with hindsight for us to complain about the decisions made.
Reality Check
• Making accurate predictions is hard
• Projects grow organically
• At least you are getting paid to work on this, right?
Be Understanding
• Don’t be a jerk.!
• Try to understand why things evolved the way they did.
• Forgive your predecessor
• They can provide useful information!
• Circumstances can and will be reversed
Maintenance Over Time
Why is it harder?• Project is no longer the bright and shiny
• Adding features adds to complexity
• Bugs caused by unforeseen edge cases
• Not enough tests make catching developer introduced bugs harder
• Mistakes at the beginning are really starting to show
Original Engineer(s) was an IdiotHOW DO WE FIX THIS?
The Basics
Maintenance Over Time
The BasicsMake engineer setup and system config as fast/easy as possible
Vagrant DockerChef
PuppetAnsible
Salt Stack
More Basics: TestsNo more code changes without tests.
New code releases must maintain test coverage or increase it.
More Basics: Document!
Document everything as you come across it
Markdown, RestructuredText, Google Docs, even Wikis
Don’t use Word or Pages!
Refactor Mercilessly
Once the basics are in place…
Reward Successful Refactoring
Give them a gnome!
Courtesy Daniel Roy Greenfeld
Code Reduction Gnome
Courtesy Daniel Roy Greenfeld
New code must follow best practices
Basic: Follow Best Practices
Bug-fixed code might be moved to best practices
Embrace Code
Reuse
3+ Identical Lines of Code in the same place?
Stick it in a function or method!
Write a test for that function or method!
Any place this function or method is used…
Write a test!
Release Early and Often
• Rather than do massive updates periodically
• Do incremental releases constantly
• Users respond more favorably
• Bug management is easier
Use Feature Flags• Turn new features off and on as needed
• Libraries can help you
• Use it for A/B testing
• In use at Eventbrite and others
http://en.wikipedia.org/wiki/Falcon_9
Summary
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