Google App Engine - Java Style

Google App Engine Java style Peter Sönnergren Lind GTUG Stockholm 2010-01-14

whoami
Java dev since like 1999
Ruby enthusiast
Consultant @ Devoteam Quaint
Owner and CTO @ Pockus
A book club that doesn't suck
http://www.pockus.se

App Engine 101
Googles Cloud offering
Run your web apps on Google's infrastructure
Platform As A Service
Unique Selling Point - Scalability on demand
Instances are added when needed
Two flavors
Python since spring 2008
Java since spring 2009
Technology preview :S

The first hit is always free
App quotas
Free to start, 5 million pageviews/month
10 apps per user
Can enable billing
AdWords payment model
$32 worth of resources/month
http://yourapp.appspot.com
http://www.yourapp.com using Google Apps for Domains

GAE/J in a nutshell
A place to run Java Servlets (2.5 API)
Meaning support for
Servlets/JSP
Web Frameworks (Spring MVC/Wicket/Tapestry/Struts ...)
In a sandbox
All apps in isolation
Subset of the JRE
Jetty customized
Don't use the Jetty features, this might change

Limitations
JRE White List
No threads
Cron jobs
Task queues
No outgoing connections (except mail/http/xmpp)
Read-only FS
30 second request limit, no push (upcoming?)
App spin-up time
No SLA available

Datastore - BigTable
NoSQL
Stores “entities”
Parent-Child relationships
Add “properties” at will (beware of restrictions in queries)
GQL to query
Transactions – but not global like in databases
!= for one column only
Max number of entities returned is 1000

Services – using standard APIs
Datastore (BigTable)
JDO
JPA
Memcache – javax.cache
URL Fetch – java.net
Mail – javax.mail
Low-level APIs are available

Services – Google APIs
Google Accounts
XMPP
Image manipulation
Task Queues
Blobstore
Cron jobs

Teh awesome
Scalability is job #1
On demand
Easy to get started
No sysadm work needed
An App Engine app is built to scale
No long running requests
NoSQL
Move processing out of persistence layer

Getting started
Sign up using phone nr (for verification sms)
Create app id
Download Eclipse plugin
Or use SDK with scripts
Generate app
Push to cloud

Development
dev_appserver.sh
User service
Datastore
Et al, but no cron or tasks
Generates indexes for Datastore
Blacklist/whitelist emulation
Eclipse plugin (official)
Netbeans, IntelliJ
Support for mocking the environment for testing

Administration
https://appengine.google.com
One app can have several developers
Concurrent versions
http://<version>.latest.appspot.com
Manage billing settings
Bandwidth/CPU time/storage/mail
Logs
Datastore viewer

Language support
App Engine accepts Java byte code, not source code
Permissive with reflection magic, creating classloaders etc
App Engine team works together with JVM Lang implementors
http://lotrepls.appspot.com/
beanshell, clojure, groovy, javascript, jython, jruby, scala, scheme
PHP through Caucho/Quercus

Vendor lock-in?
Use standard Java APIs
Demoed on IBM Websphere
http://code.google.com/p/appscale/
http://code.google.com/p/typhoonae/
Python only
http://arachnid.github.com/bdbdatastore/
Use dev_appserver with alternative datastore

Demo Your first cloud application in a few minutes!

Resources
http://code.google.com/appengine/
http://googleappengine.blogspot.com/
Programming Google App Engine
On O'Reilly
Written by a Googler
Google Groups
http://code.google.com/appengine/community.html

Contact
mailto:peter@lind.be
http://github.com/peterlind
http://twitter.com/peter_lind

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Google App Engine - Java Style

by Peter Lind on Jan 14, 2010

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