Google App Engine at a glance .

1. Google App Engine at a glance


2. Introduction
• PaaS
• Running own Apps in Google infrastructure
• Supports different runtime environments – Java ( JRE 6 with limitations, standard APIs like JDO, JPA, JavaMail) – Python ( 2.5.2, standard library)
• App runs in sandbox
• Automatic scaling and load balancing


3. Architecture - Overview Internet Internet http://(version).(appid>).appspot.com/some/path Loadbalancer Frontend … Frontend Static File Server … Static File Server Application Server … Application Server static files resource files program files static files resource files program files


4. Architecture - Application Server URLFetcher Application Mail Internet Internet XMPP Application sandbox /Runtime Environment External Services Authentication Memcache Datastore Blobstore Logging Image Tasks Internal Services Google App Engine Bigtable memcache Google Infrastructure


5. Services / Capabilities
• Sandbox
• Runtime Environment / Servlet Container – Java Interpreter – Read only filesystem – Memory
• Data Store • Services – User authentication – URL Fetch – Mail – XMPP – Memcache – Image Manipulation – Scheduled tasks / Task Queues – Blobstore – Logging


6. Limitations
• Programming Model – Application runs in sandbox and can not
• Write to filesystem • Make arbitary network connections
• Use multiple threads/processes
• Perform long-lasting processing
• Permissions
• Know about other instances/applications – Sandbox restrictions are implemented as JVM
• Quotas (Requests, In/Out bandwidth, CPU time, API calls) – Billable Quotas
• Set by the application owner to keep in budget – Fixed Quotas
• Set by GAE to ensure integrity of the system


7. Development Environment
• Tools – Development Server – Application lifecycle management – Eclipse plugins / Firefox plugin (GWT) – Local unit testing / debugging


8. Deployment Environment
• Application is deployed as war which contains: – Static files – Resource Files – Program Files – Deployment Descriptor
• Rich Admin web console
• Deployment is integrated in IDE
• Deploy multiple version of the application at the same time


9. GWT-RPC Client Server Framework RemoteServiceServlet ServiceDefTarget RemoteService extends related implements OurServiceImpl OurServiceAsync OurService implements Our stuff implements ProxyService GWT framework (autogenerated)


10. App Engine Datastore Entity key “data” Application ID Property * Kind name Value * ID / Name
• Non-relational Data-
• Distribution, replication, store load balancing behind
• Stores data as entities the scene
• APIs:
• Based on Bigtable / GFS – JDO / JPA – Low Level API


11. Using Email/XMPP
• Create Servlet for handling incoming messages
• Ensure proper url configuration ins deployment descriptor
• Configure as inbound service
• XMPP – implementation supports no Group Chat – App-id@appspot.com / anything@version.latest.app-id.appspotchat.com


12. Logging
• Java.util.logging.Logger
• View in Administration Console
• Download logfiles
• Standard output / standard error are written to the logs


13. Local Unit Testing
• LocalTestServiceHelper provides – local test environment including GAE services
• Datastore
• XMPP/Mail
• User Management – Capability to use JUnit framework


14. Memcache Service
• Distributed in memory cache
• Configurable expiration time but • Unreliable might be vanished at any time
• Supported Interfaces : – JACHE (JSR 107: JCACHE – Java Temporary Caching API) – The Low-Level Memcache API (documentation)


15. User Management – Google Accounts
• Optional feature
• Utilize Google Authentication system in your own application -> focus on business logic
• Access to Google account data -> email, id
• Access constraints based on roles – Declarative in deployment descriptor (URL based) – programmatically


16. Managing Applications
• Administration Console @http://appengine.google.com/a/yourdomai n.com – Application Dashboard – Multiple application versions – Analyzing log files (including admin) – Analyzing resource usage


17. Further Readings
• Google App Engine documentation
• GWT documentation
• “Beginning Java Google App” – Kyle Roche, Jeff Douglas
• “Programming Google App Engine” – Dan Sanderson.



For see the Presentation Transcript about this post and more info visit :
Google Appengine At A Glance.

-- by Stefan Christoph