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Google App Engine:Java TechnologyIn The Cloud
Toby Reyelts, Max Ross, Don SchwarzGoogle
1Thursday, 4 June 2009
Goals
> Google App Engine> Java on App Engine> The App Engine Datastore> Demo> Questions
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2Thursday, 4 June 2009
What Is Google App Engine?
> A cloud-computing platform> Run your web apps on Google’s infrastructure> We provide the container and services (PaaS)
• Hardware, connectivity• Operating system• JVM• Servlet container• Software services
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3Thursday, 4 June 2009
Key Features
> No need to install or maintain your own stack> We scale for you> Use Google’s scalable services via standard APIs> Charge only for actual usage
• Always free to get started> Built-in application management console
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4Thursday, 4 June 2009
App Engine Architecture
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Incoming Requests
5Thursday, 4 June 2009
App Engine Architecture
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Incoming Requests
App Engine Front End
App Engine Front End
App Engine Front End
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App Engine Architecture
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AppServer AppServer AppServer
Incoming Requests
App Engine Front End
App Engine Front End
App Engine Front End
5Thursday, 4 June 2009
App Engine Architecture
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AppServer AppServer AppServer
Incoming Requests
App Engine Front End
App Engine Front End
App Engine Front End
Load Balancer
5Thursday, 4 June 2009
App Engine Architecture
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AppServer AppServer AppServer
Incoming Requests
App Engine Front End
App Engine Front End
App Engine Front End
Load Balancer
AppServer
API Layer
Other Google Infrastructure
- Bigtable
- Google Accounts
- Memcache
- Image manipulation
App App App
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When To Use Google App Engine
> Targeting web applications• Serve HTTP requests, limited to 30 seconds• No long-running background processes• No server push
> Sandboxed environment• No threads• Read-only file system
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6Thursday, 4 June 2009
WebHooks (coming soon)
> Incoming email> XMPP> Google Wave> Task Queues
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7Thursday, 4 June 2009
Java Support
> Servlets> Software services> Sandboxing> DevAppServer> Deployment> Tooling
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8Thursday, 4 June 2009
Servlet API
> Full Servlet 2.5 Container• HTTP Session• JSP
> Uses Jetty and Jasper• Powered by Google’s HTTP stack• No Jetty-specific features• Subject to change
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9Thursday, 4 June 2009
Software Services
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Service Java Standard Google InfrastructureAuthentication Servlet API Google Accounts
Datastore JPA, JDO Bigtable
Caching javax.cache memcacheg
E-mail javax.mail Gmail gateway
URLFetch URLConnection Caching HTTP proxy
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Sandboxing
> What do we do?• Restrict JVM permissions• WhiteList classes
> Why is it necessary?• Clustering - JVMs come and go• Protect applications from one another
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Sandboxing Restrictions
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Restriction Alternative
Threads Async and Queue API (Soon!)
Direct network connections URLConnection
Direct file system writes Memory, memcache, datastore
Java2D Images APISoftware rendering
Native code Pure Java libraries
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Flexible Sandboxing
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13Thursday, 4 June 2009
Flexible Sandboxing
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JVM Permissions often too coarse.
13Thursday, 4 June 2009
Flexible Sandboxing
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JVM Permissions often too coarse.They either provide a cramped sandbox.
13Thursday, 4 June 2009
Flexible Sandboxing
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JVM Permissions often too coarse.They either provide a cramped sandbox.
Or they hand over the nuclear launch codes.
13Thursday, 4 June 2009
Flexible Sandboxing
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JVM Permissions often too coarse.They either provide a cramped sandbox.
Or they hand over the nuclear launch codes.
App Engine delivers a happy medium.
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Flexible Sandboxing - Reflection
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14Thursday, 4 June 2009
Flexible Sandboxing - Reflection
> Access private fields, call private methods• suppressAccessChecks• accessDeclaredMembers
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14Thursday, 4 June 2009
Flexible Sandboxing - Reflection
> Access private fields, call private methods• suppressAccessChecks• accessDeclaredMembers
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Field f = String.class.getDeclaredField(“count”);f.setAccessible(true);
f.set(“Hello World”, 2);
Bad!
14Thursday, 4 June 2009
Flexible Sandboxing - Reflection
> Access private fields, call private methods• suppressAccessChecks• accessDeclaredMembers
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Field f = String.class.getDeclaredField(“count”);f.setAccessible(true);
f.set(“Hello World”, 2);
Field f = MyClass.class.getDeclaredField(“foo”);f.setAccessible(true);
f.set(myObj, aFoo);
Bad!
Good!
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Flexible Sandboxing - Class Loading
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15Thursday, 4 June 2009
Flexible Sandboxing - Class Loading
> Create user-controlled ClassLoaders• createClassLoader
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15Thursday, 4 June 2009
Flexible Sandboxing - Class Loading
> Create user-controlled ClassLoaders• createClassLoader
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Bad!ClassLoader myClassLoader = new URLClassLoader() {
public PermissionsCollection getPermissions(CodeSource cs) {
// return AllPermission;
}
};
15Thursday, 4 June 2009
Flexible Sandboxing - Class Loading
> Create user-controlled ClassLoaders• createClassLoader
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Bad!ClassLoader myClassLoader = new URLClassLoader() {
public PermissionsCollection getPermissions(CodeSource cs) {
// return AllPermission;
}
};
Good!ClassLoader myClassLoader = new URLClassLoader() {
public Class findClass(String className) {
// define and load some newly generated bytecode
}
};
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Flexible Sandboxing - Compatibility
> Dependency Injection Frameworks• Guice, Spring
> Aspect Oriented Programming• AspectJ, Spring AOP
> Web Frameworks• GWT, Tapestry, BlazeDS (Flex), Grails!
> Alternate JVM languages• Scala, Rhino, JRuby, Jython, Clojure, Groovy, PHP
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16Thursday, 4 June 2009
DevAppServer
> Emulates the production environment> Customized Jetty server> Local implementation of services
• LRU memcache• Disk-backed datastore• HttpClient-backed URLFetch
> Some sandbox restrictions difficult to emulate
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17Thursday, 4 June 2009
Deployment
> Your app lives at • <app_id>.appspot.com, or• Custom domain with Google Apps for your Domain
> Command line and IDE tools> Admin Console
• Dashboards• Manage multiple versions• View logs (java.util.logging)
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18Thursday, 4 June 2009
Quotas and Billing
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Resource Provided Free Additional CostCPU 6.5 hours/day $0.10/hour
Bandwidth In 1GByte/day $0.10/GByte
Bandwidth Out 1GByte/day $0.12/GByte
Stored Data 1 GB $0.005/GB-day
Emails sent 2000/day to users5000/day to admins $0.0001/email
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Tooling
> SDK Tools API• Command-line tools, Ant, and IDE plugins
> Provides• Deployment• DevAppServer• WhiteList• XML validation
> Google Eclipse Plugin, Intellij Plugin
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20Thursday, 4 June 2009
The Datastore Is...
> Transactional> Natively Partitioned> Hierarchical> Schema-less> Based on Bigtable> Not a relational db> Not a SQL engine
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Wow. That isone big table.
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Simplifying Storage
> Simplify development of apps> Simplify management of apps> App Engine services build on Google’s strengths> Scale always matters
• Request volume• Data volume
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22Thursday, 4 June 2009
Datastore Storage Model
> Basic unit of storage is an Entity consisting of• Kind (table)• Key (pk)• Entity Group (top level ancestor)
• Has locking implications
• 0..N typed Properties (columns)
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23Thursday, 4 June 2009
Interesting Datastore Modeling Features
> Ancestor> Multi-value properties> Variable properties> Heterogenous property types
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Kind PersonEntity Group /Person:EthelKey /Person:EthelAge Int64: 30Hobbies String: Tennis
Kind PersonEntity Group /Person:EthelKey /Person:Ethel/Person:JaneAge Double: 3.5Pets Key:/Turtle:Sam Key:/Dog:Ernie
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Datastore Transactions
> Transactions apply to a single Entity Group• Global transactions are feasible
> get(), put(), delete() are transactional> Queries are not transactional (yet)
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/Person:Ethel/Person:Jane
/Person:Ethel
/Person:Max
Transaction
25Thursday, 4 June 2009
Standards-based Persistence
> JDO or JPA (your choice)• Established apis and existing tooling• Easier porting• Mappable (mostly) to the datastore• Soft schemas
> DataNucleus App Engine plugin> Why not a JDBC driver instead?
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26Thursday, 4 June 2009
@Entity
class Person {
// ...
@OneToMany
List<Pet> pets;
}
Transparent Entity Group Management
> Entity Group layout is important• Write throughput• Atomicity of updates
> Ownership implies co-location within Entity Group
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Kind PetEntity Group /Person:EthelKey /Person:Ethel/Pet:Sam
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Demo!
28Thursday, 4 June 2009
Demo - Login
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29Thursday, 4 June 2009
Demo - Question
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30Thursday, 4 June 2009
Demo - Question Result
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31Thursday, 4 June 2009
Demo - Scoreboard
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Demo - Code!
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http://java-demo.appspot.com
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Toby Reyelts, Max Ross,Don Schwarztobyr@google.com maxr@google.comschwardo@google.com
http://code.google.com/appengineGoogle Group: google-appengine-java
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