Implementing a command line client to

GitHub in GoOwen Ou

@JingwenOwenOu

Agenda

• Automating Git/GitHub workflows with gh

• Introduction to Go

• What I learnt from implementing gh with Go

What’s gh?

• a command line tool that makes working with GitHub easier

• gh pull

• gh ci

• gh fork

• etc.

A broken workflow• git checkout -b new_feature

• some code changes...

• git add .

• git commit -m “A comment”

• git push origin HEAD

• check CI status, oops..context switch

• create a pull request, oops...context switch

An optimized workflow• git checkout -b new_feature

• some code changes...

• git add .

• git commit -m “A comment”

• git push origin HEAD

• gh ci # prints build status

• gh pull # creates a pull request

Demo

Implementation of gh

• Implemented in Go

• Fast (40% faster than Hub)

• A single, statically linked binary with no dependencies (no VM needed!)

• Unix, e.g., gh pull -b integration -h new_feature

What’s Go?

• Imperative

• Object-oriented like

• Concurrent

• Compile to machine code

• Created at 2009, v1.1.1

Ken Thompson

• Founding father of Unix, see “Coders at work”

• Bring in regular expression to computing

• Created grep in an evening

• Designed UTF-8 on a diner placemat

Robert Griesemer

• Native code generation for V8

• Java HotSpot VM

• Strongtalk VM (inspires the Dart VM)

Rob Pike• First window system for

Unix at Bell Labs

• Plan 9

• Co-Authors of “The Unix Programming Environment” & “The Practice of Programming” with Brian Kernighan

• Newsqueak, Limbo: implementations of Tony Hoare’s CSP

Why Go?

• Why Learn Go? An interview with Rob Pike: http://www.youtube.com/watch?v=FTl0tl9BGdc

Hello Go

More about Go

• Compilation is very fast, gh has 1581 LOC, the build time is 0.77s

• Static typing & type inference

• Low level primitives uint, float64

• Garbage collected

• Pointers without pointer arithmetic

Interfaces

The C10K Problem

• The problem of optimizing socket server software to handle a large number of clients at the same time

• C10k = concurrent ten thousand connections

• Linux pthreads (8MB), Windows (1MB), Coroutines (4k, e.g., Ruby Fibers)

Goroutines

• Coroutines in Go, 4K, light weight threads

• Segmented stacks (a double linked lists)

• No stack-overflow

• Automatically scale to multiple-cores

• In the future, scale to multiple machines

Goroutines

Channels

Learning from gh• Right tool for the job - building a Unix tool

• Go’s compiler is freaking fast!

• Clarity and simplicity, less is more

• Go fmt

• Fast startup time, low memory usage

• Deploy a static library (making deployment so much simpler!)

• Goroutines & channels (higher level APIs in net/http)

References• gh: https://github.com/jingweno/gh

• Code examples: https://gist.github.com/jingweno/c00e973ade6d66b827fd

• Go at Google: http://www.infoq.com/presentations/Go-Google

• Concurrency is not Parallelism: http://vimeo.com/49718712

• Real world Go: https://gist.github.com/ungerik/3731476

Q&A