2011 june-kuala-lumpur-gtug-hackathon

Google App Engine
Ikai Lan
Kuala Lumpur, GTUG Hackathon
Twitter: @ikai
June 18, 2011

Saturday, June 18, 2011

About the speaker
• Developer Relations at Google based out
of San Francisco, CA
• Primarily work in Java and Python
nowadays; lots of experience with Ruby,
JavaScript, PHP <5.3
• Focus: Cloud products
• Twitter: @ikai

Agenda

• What is Google App Engine?
• Various features of GAE
• How to get started
• Introduction to Go
• Important tools + some tips


Software

Platform

Infrastructure

Source: Gartner AADI Summit Dec 2009


• Easy to build
• Easy to manage
• Easy to scale


“We wear pagers so
you don’t have to”


>90K Developers

>130K Apps

>700M daily pageviews


SDK & “The Cloud”

Hardware

Networking

Operating system

Application runtime

Java, Python, Go

Static file serving

20


Development Cycle

• Write code locally
• Test, push to Google Servers
• Administer via a web interface - http://
appengine.google.com


Admin Console


Duke, the Java mascot
Go Gopher Copyright © Sun Microsystems Inc., all rights reserved.


Extended Language support
through JVM
• Java
• Scala
• JRuby (Ruby)
• Groovy Duke, the Java mascot
Copyright © Sun Microsystems Inc., all rights reserved.

• Quercus (PHP)
• Rhino (JavaScript)
• Jython (Python)
• Clojure


Core APIs
Memcache Datastore URL Fetch

Mail XMPP Task Queue

Images Blobstore User Service


High Replication

• Strongly consistent, multi-datastore, multi-
data center serving solution
• Write once, have your data be available in a
highly consistent manner
• No data loss, no datastore outages


Other APIs

• High performance image serving
• App Engine Map Reduce
• Prospective Search API
• Pipeline API
• OAuth provider


Prospective Search
• Matches a high rate of incoming documents
• 100,000 matches a second
• Think: How might we build something like
Google Alerts?
• http://code.google.com/appengine/docs/
python/prospectivesearch/


A basic Python app

• 2 ﬁles: app.yaml and main.py
• Easier to use when Python SDK is in your
system path
• Start server with dev_appserver.py
• Deploy via appcfg.py


app.yaml


main.py


Getting started with
Java

• Servlets API
• Google Plugin for Eclipse will generate a
skeleton project: http://code.google.com/
eclipse/beta/docs/download.html


Go: why I like it
• “The next version of C, brought to you by
the guys who didn’t bring you C++”
• Modern, type safe compiled language (stdlib
includes: json parsing, web server)
• Functions as ﬁrst class objects
• Concurrency baked in via goroutines and
channels
• Very fast compilation times

Flexible interfaces
// This is an interface declaration
type myInterface interface {
set(i int)
}

// This is a Type declaration. Note that it is a type, not a class
type myType struct {
i int
}

// This is how we define a function where myType is a receiver
// With an instance of myType we can call myType.set(123)
func (p *myType) set(i int) {
p.i = i
}

// Because myType defines a function with the signature set(int i) method,
// we can use it anywhere myInterface is accepted!
func setToThousand(x myInterface) {
myInterface.set(1000)
}


First class functions
package main
import "fmt"

// Make a function that returns a new function
func makeAdd(increment int) (counter func(int) int) {
return func(v int) int {
return v + increment;
}
}

func main() {
fmt.Printf("value of makeAdd(100)(1) is %vn", makeAdd(100)(1));
fmt.Printf("value of makeAdd(200)(2) is %vn", makeAdd(200)(2));
}

// Outputs:
// value of makeAdd(100)(1) is 101
// value of makeAdd(200)(2) is 202


Goroutines and
package main
Channels
import (
"fmt"
"time"
)

func doLotsOfWork(until int, ch chan int) {
c := 0
for i := 0; i < until; i++ {
c += i
time.Sleep(1000)
}
ch <- c
}

func main() {
ch := make(chan int)

// First the work off into the background
go doLotsOfWork(5, ch)

// Do more work here while we wait for this process to complete

// Block until doLotsOfWork sends data back on this channel
i := <- ch
fmt.Printf("Final value: %vn", i)
}


It runs on App Engine!
• Currently requires whitelisting
• Experimental status
• Goroutines allow for concurrency within
request; concurrent requests coming
• Demo app: http://moustach-io.appspot.com/
• Source: https://code.google.com/p/
appengine-go/source/browse/example/


Mustachio


General tips
• The datastore is built on top of BigTable. It
is non-relational!

• Be aware of limits: 30 second requests, 10
minute tasks queues/cron jobs, whitelisted
classes
• Python 2.5 compatible (but can use 2.6 or
2.7 locally)


Useful Python tools
• Tipfy: http://www.tipfy.org/
• Django non-rel: http://
www.allbuttonspressed.com/projects/
django-nonrel
• Testbed API: http://code.google.com/
appengine/docs/python/tools/
localunittesting.html


Java tips
• Use low-level datastore API or third party
API: http://code.google.com/p/objectify-
appengine/
• Start with servlets API - will have to do
some work to make your favorite
framework work. Slim3 is a good GAE
speciﬁc framework


Summary

• Hopefully people here are interested in
hacking on App Engine
• Java, Python and Go
• Ask me if you have general questions, I will
be around all weekend


Questions?

• Twitter: @ikai
• App Engine: http://code.google.com/
appengine


2011 june-kuala-lumpur-gtug-hackathon

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