GAE Overview

1. CS569 Selected Topics in Software EngineeringSpring 2012 GAE Overview

2. Start installation in parallel with this presentation • Oracle JDK 1.6 (already installed on Macs) • Eclipse Galileo • http://eclipse.org/galileo/ • GAE plugins • http://code.google.com/appengine/downloads.html

3. Google App Engine (GAE)is a Platform-as-a-service • Infrastructure-as-a-service (IaaS) • Virtual (and physical ) machines on demand • E.g., Rackspace • Platform-as-a-service (PaaS) • Scalable servers with rich but restrictive APIs • E.g., Google App Engine (GAE) • Software-as-a-service (SaaS) • Servers with customizable web apps you can lease • E.g., SalesForce.net

4. Google App Engine (GAE)core functionality • Serving up custom web sites (Servlets API) • Storing data for you (JDO and JPA APIs) • Other APIs • UI Toolkit (GWT) • Asynchronous tasks • Retrieving web content • Caching • Image processing • …

5. Reasons to start with GAE • Free to start • Uses a language you probably know • Integrated with tools you probably know • Provides exposure to cloud funkiness • No support for inner joins • Automatic load balancing • Non-DBMS transactions • Sandboxing

6. Languages supported by GAE • Java • This is what I will use in this class • Mainly thanks to its nice Eclipse integration • Python • Somewhat richer API and command-line tools • Feel free to use this instead of Java if you like • (But I do not know Python, FYI) • Go • New Google language with built-in concurrency • Feel free to use it (but FYI, I don’t know Go)

7. Still other languages • As long as you can compile it to Java 1.6-compatible bytecode • JRuby • Scala • Rhino-compatible JavaScript • … • Feel free to use these • I know JavaScript and have briefly used Rhino but haven’t used the Rhino compiler to Java

8. Serving up custom web sites • GAE implements the Java servlet specification • Your Eclipse project implements a web site • Servlets: • Handlers for URLs of the form “/myservlet” • An XML document maps URLs to servlets • JSPs: • Text files that mix HTML and Java • Automatically converted to servlets • Feel free to use either one

9. Storing data for you • Java Data Objects (JDO) • A standardized way of storing objects • Create an object, store it, load it later • No need to mess around with INSERT statements • Java Persistence API (JPA) • Another standardized way of storing objects • JPA is basically a refinement of JDO • As well supported in GAE as JDO • Low-level APIs • Which are more powerful and easier to misuse

10. Other APIs: UI Toolkit • Google Web Toolkit (GWT) • Define your application’s UI in Java • Code looks very similar to what you’d write to create a desktop GUI • Compiles to JavaScript • Support for multiple targets • Desktop browser • Mobile browsers • Available for you to investigate as a How-To

11. Other APIs: Asynchronous tasks • Very similar to “cron” jobs • Create a task • Pass it some parameters • Schedule to run at a certain time if you like • Put it on a queue • Very handy for… • Loading data • Generating reports • Performing sophisticated transactions

12. Other APIs: Retrieving web content • Your application can retrieve data from other servers • Retrieve XML from remote web services • Retrieve zip files, uncompress them, store data • Very handy for… • Loading data • Integrating with other systems

13. Other APIs: Caching • GAE provides a distributed RAM cache • Server RAM is copied to all the other computers • Very very fast data access (versus JDO) • Still can take advantage of using multiple servers • Caveat: it has only a limited capacity • You can’t cache everything • Stuff can disappear (similar to Java “weak references”) • Effective caching and asynchronous computation are two of the most important concepts for achieving high-performance cloud applications

14. A few of the other APIs • Image Processing • Good for manipulating photos • Channels • Persistent socket-like connection to browser • Emails • Implements the JavaMail specification • Can send attachments • XMPP • For sending messages between applications

15. Limitations • Functional • Due to the architecture • Sandbox • You can’t access all Java SDK APIs • Quotas and timeouts • You can’t use unlimited resources

16. Functional limitations • Data are copied and stored on many servers • Sometimes servers fail • Sometimes servers have inconsistent data • Certain data manipulations are not tractable • E.g., GAE cannot do DB table joins like you’re used to • Servers start and stop to meet your load • Servers might lose in-memory state at any time • You can’t write to an individual server’s files • You can’t have a server all to yourself

17. Sandbox limitations • No writing to file system or DBMS • Serialize to the data store via JDO instead • No spawning threads • Use asynchronous tasks instead • No killing the JVM • Just return from servlet; no need to kill anyone • No loading native code • Put it on another server, invoke via web service • … And several other less important limitations

18. Quotas and timeouts • Free tier (last time I checked) • Max request size: 32MB • Max response size: 32MB • Max handler time per server hit: 60 seconds • Max stored data: 1GB • Max outbound bandwith: 1GB/day, 56 MB/minute • Max incoming bandwidth: ditto • And many other limitations • If you want to raise quotas, pay $$ (optional)

19. Basic steps for creating app • Create new project in Eclipse • Implement, test browser-based app locally • Push to GAE and test remotely • Test + refine performance, reliability, security • Expose refined functionality via web services • Implement mobile app • Test + refine usability, security

20. Hello, world Creating a simple GAE application

21. A few words about the How-To • Part 1: Cloud platform • Can cover IaaS, PaaS, or Saas, as long as there’s a way to demonstrate the stuff below • Part 1A: Specify the steps required to install and configure the platform • Part 1B: Specify the steps required to read data from the browser and store the data away • Part 1C: Specify the steps required to retrieve data from its storage location and send to the browser

22. Suitable cloud platforms(feel free to suggest others) • Windows Azure (I have some free licenses) • Amazon EC2 • HP Cloud Services • RackspaceIaaS • SalesForceSaaS • Oracle Public Cloud • … more every day

23. More words about the How-To • Part 2: Mobile platform • Can be a binary platform or a web-based platform (i.e., can be for making native apps or for making web apps that look good on a mobile device) • Part 2A: Specify the steps required to install and configure the platform • Part 2B: Specify the steps required to retrieve an XML document from a remote server • Part 2C: Specify the steps required to display some text from some XML elements to the user

24. Suitable mobile platforms(feel free to suggest others) • Google Web Toolkit • jQTouch • PhoneGap • Adobe Air • Windows mobile SDK • Rhodes • … more every day

25. More information • Each How-To part only needs to explain how to use platforms on one operating system • Windows/Mac/Linux for cloud • iOS/Android/Blackberry/Windows for mobile • Probably should be only 6-10 pages long • You get to work on this in groups of ~ 4 people • Maybe working in pairs on cloud and mobile parts

26. Don’t turn this into a really big deal.An example… • These 3 pages from the GAE “Getting started” guide” would make a great Part 1 • http://code.google.com/appengine/docs/java/gettingstarted/installing.html • http://code.google.com/appengine/docs/java/gettingstarted/usingjsps.html • http://code.google.com/appengine/docs/java/gettingstarted/usingdatastore.html • These parts of the Titanium “Quick start” would make a great Part 2. • https://wiki.appcelerator.org/display/guides/Quick+Start • Mobile SDK Installation and Configuration • Installing and configuring Titanium Studio • Hello World! • And relevant pages from the API docs, e.g., Titanium.Network.HTTPClient, Titanium.UI.Label

27. Next steps for you… • As a group, start trying to install and configure a cloud platform for your How-To • Strongly encouraged • Buy the textbooks (available at bookstore) • Read GAE Book, chapters 1 and 2 this weekend • Bring your laptop to every class