Google App Engine for Beginners

A deck used to introduce Google App Engine at an Appsterdam Guru Session. It features an overview of the features provided by App Engine, two hands on examples and a peek on advanced features.

Transcript

1. Google App Engine for beginners ...and a peek on experimental features Alessandro Bahgat @abahgat Appsterdam Guru Session, June 25th 2013
2. What is Google App Engine? Google App Engine is a complete development stack that uses familiar technologies to build and host applications on the same infrastructure used at Google. @abahgat, #appsterdam “ ” 2/46
3. Four runtime environments Python Java Go PHP @abahgat, #appsterdam 3/46
4. Your code runs in a sandbox http://www.flickr.com/photos/damongman/5623130732/
5. The Sandbox Secure environment that provides limited access to the underlying operating system. The sandbox allows App Engine to @abahgat, #appsterdam distribute web requests across multiple servers start and stop servers to meet traffic demands isolate apps in a secure, reliable environment abstract hardware, operating system and physical location of the web server · · · · 5/46
6. Sandbox limitations @abahgat, #appsterdam outbound connections: only through the provided URL fetch and email services or the experimental Socket API. inbound connections: only HTTP(s) on ports 80/443. filesystem access: writing files is not allowed. An application can read only files uploaded with the application code. no native code: libraries that depend on native code are generally not available. time limits: app code must terminate within given time limits. (60s for web requests, 10m for tasks but unlimited time for backend jobs) · · · · · 6/46
7. Storing data Three options for data storage App Engine Datastore a NoSQL schemaless data storage built in GAE Google Cloud SQL: a relational SQL database service similar to MySQL Google Cloud Storage: file based storage @abahgat, #appsterdam 7/46
8. No fixed costs: pay only for what you use... http://www.flickr.com/photos/jasonalley/5039425430
9. ...with generous free quotas http://www.flickr.com/photos/toddle_email_newsletters/7002322316
10. Getting app & running See it in action
11. Download the SDK Go to https://developers.google.com/appengine/downloads and grab the Python installer. You should also have Python by now, but in case you do not, grab it from here. (Your platform might offer smarter ways to install it.) @abahgat, #appsterdam 11/46
12. Start up the launcher @abahgat, #appsterdam 12/46
13. Create a sample application @abahgat, #appsterdam 13/46
14. Run! http://www.flickr.com/photos/nihonbunka/46324600
15. Let's dive into code Basics of the Python Runtime
16. Application Configuration All configuration settings are stored in a file called a p p . y m l @abahgat, #appsterdam a p p l i c a t i o n : e x a m p l e v e r s i o n : 1 r u n t i m e : p y t h o n 2 7 a p i _ v e r s i o n : 1 t h r e a d s a f e : y e s h a n d l e r s : - u r l : . * s c r i p t : m a i n . a p p l i b r a r i e s : - n a m e : w e b a p p 2 v e r s i o n : " 2 . 5 . 2 " Y A M L 16/46
17. A self sufficient web application App Engine supports webapp2 by default: In addition to webapp2, the environment includes WebOb and Django. @abahgat, #appsterdam i m p o r t w e b a p p 2 c l a s s M a i n H a n d l e r ( w e b a p p 2 . R e q u e s t H a n d l e r ) : d e f g e t ( s e l f ) : n a m e = s e l f . r e q u e s t . g e t ( ' n a m e ' ) s e l f . r e s p o n s e . w r i t e ( ' H e l l o % s ! ' % n a m e ) a p p = w e b a p p 2 . W S G I A p p l i c a t i o n ( [ ( ' / ' , M a i n H a n d l e r ) ] , d e b u g = T r u e ) P Y T H O N 17/46
18. Datastore(s) @abahgat, #appsterdam There are two implementations of datastore The original one is implemented in g o o g l e . a p p e n g i n e . e x t . d b The new one is called NDB and it is implemented in g o o g l e . a p p e n g i n e . e x t . n d b They are very similar but not identical We will cover NDB · · · · · 18/46
19. Datastore Creating an entity type is as easy as creating a Python class. @abahgat, #appsterdam f r o m g o o g l e . a p p e n g i n e . e x t i m p o r t n d b c l a s s C o n t a c t ( n d b . M o d e l ) : n a m e = n d b . S t r i n g P r o p e r t y ( ) e m a i l = n d b . S t r i n g P r o p e r t y ( ) b i r t h _ d a t e = n d b . D a t e P r o p e r t y ( ) P Y T H O N 19/46
20. Querying the Datastore The Datastore API is Object Oriented. @abahgat, #appsterdam f r o m g o o g l e . a p p e n g i n e . e x t i m p o r t n d b d e f S t o r e s B y C i t y ( c i t y , l i m i t ) : q u e r y = S t o r e . q u e r y ( S t o r e . c i t y = = c i t y ) . o r d e r ( S t o r e . n a m e ) r e t u r n q u e r y . f e t c h ( l i m i t , p r o j e c t i o n = [ S t o r e . n a m e , S t o r e . a d d r e s s ] ) P Y T H O N Queries are objects Filters and projections are specified by calling methods Make sure you know the limits! (Read the docs) · · · 20/46
21. Querying the Datastore with GQL You can write queries with GQL, a SQL-like language. GQL is translated to NDB's native query API. (This is the opposite of what traditional ORM libraries do!) @abahgat, #appsterdam f r o m g o o g l e . a p p e n g i n e . e x t i m p o r t n d b q r y = n d b . g q l ( " S E L E C T * F R O M A c c o u n t W H E R E b a l a n c e < : 1 " , 1 0 0 ) P Y T H O N 21/46
22. View templates If you use webapp2, Django templates are supported by default. Alternatively, App Engine ships with jinja2, too. @abahgat, #appsterdam < h t m l > < b o d y > { % f o r c o n t a c t i n c o n t a c t s % } { % i f c o n t a c t . n a m e % } < b > { { c o n t a c t . n a m e } } < / b > { % e l s e % } U n n a m e d c o n t a c t { % e n d i f % } < { { c o n t a c t . e m a i l } } > { % e n d f o r % } < a h r e f = " { { u r l } } " > { { u r l _ l i n k t e x t } } < / a > < / b o d y > < / h t m l > H T M L 22/46
23. Dispatch to view templates Here is how to render a template in with webapp2: @abahgat, #appsterdam d e f r e n d e r _ t e m p l a t e ( s e l f , v i e w _ f i l e n a m e , p a r a m s = N o n e ) : i f n o t p a r a m s : p a r a m s = { } p a t h = o s . p a t h . j o i n ( o s . p a t h . d i r n a m e ( _ _ f i l e _ _ ) , ' v i e w s ' , v i e w _ f i l e n a m e ) s e l f . r e s p o n s e . o u t . w r i t e ( t e m p l a t e . r e n d e r ( p a t h , p a r a m s ) ) P Y T H O N 23/46
24. Memcache Memcache is a high-performance, distributed memory object caching system. Can be used to minimize hits to the Datastore or to save transient state information. @abahgat, #appsterdam f r o m g o o g l e . a p p e n g i n e . a p i i m p o r t m e m c a c h e d e f g e t _ d a t a ( ) : d a t a = m e m c a c h e . g e t ( ' k e y ' ) i f d a t a i s n o t N o n e : r e t u r n d a t a e l s e : d a t a = s e l f . q u e r y _ f o r _ d a t a ( ) m e m c a c h e . a d d ( ' k e y ' , d a t a , 6 0 ) r e t u r n d a t a P Y T H O N 24/46
25. Hands-on exercises You will have to do some work now ;)
26. Preparation @abahgat, #appsterdam Download the boilerplate code from here Uncompress it Open it up in a text editor/IDE you are familiar with Take some time to familiarize with it · · · · 26/46
27. Exercise 1 (Quasi) Real Time Communication
28. Implement a backend for the page below
29. Your mission @abahgat, #appsterdam Use the Channel API to show the cursor position of every visitor's mouse. Update the cursor position whenever users move their mouse. Remove cursor icons when visitors leave the page. Complete the code in the c h a n n e l directory of the package you downloaded earlier and implement the missing methods. Point your browser to h t t p : / / l o c a l h o s t : $ A P P _ P O R T / c h a n n e l to test your server. · · · · · 29/46
30. Channel API A channel connects two ends: @abahgat, #appsterdam A client, which A server, which · connects to a channel, listen for updates, sends messages to the server. - - - · maintains a registry of open channels, notifies clients of state changes. - - 30/46
31. The role of the Server There is a service for that! Enable presence in your a p p . y a m l and implement two handlers that can respond to P O S T at @abahgat, #appsterdam The server needs to keep track of the connected clients, you can keep that information in memcache but for this example, it is necessary to be notified of connections and disconnections. · · · i n b o u n d _ s e r v i c e s : - c h a n n e l _ p r e s e n c e Y A M L / _ a h / c h a n n e l / c o n n e c t e d / / _ a h / c h a n n e l / d i s c o n n e c t e d / · · 31/46
32. Creating a Channel Requires action on both ends. The server sends a token to the client: The client uses the token to create a channel @abahgat, #appsterdam d e f g e t ( s e l f ) : c l i e n t _ i d = u u i d . u u i d 4 ( ) . h e x t o k e n = c h a n n e l . c r e a t e _ c h a n n e l ( c l i e n t _ i d ) t e m p l a t e _ v a l u e s = { ' c l i e n t ' : c l i e n t _ i d , ' t o k e n ' : t o k e n } s e l f . _ r e n d e r _ t e m p l a t e ( t e m p l a t e _ v a l u e s ) P Y T H O N v a r c l i e n t = " { { c l i e n t } } " ; v a r c h a n n e l = n e w g o o g . a p p e n g i n e . C h a n n e l ( ' { { t o k e n } } ' ) ; f u n c t i o n s e t U p C h a n n e l ( ) { v a r s o c k e t = c h a n n e l . o p e n ( ) ; s o c k e t . o n m e s s a g e = o n M e s s a g e ; } J A V A S C R I P T 32/46
33. Using the Channel The client can only read messages from the client. It can send data to the server via HTTP requests: @abahgat, #appsterdam f u n c t i o n o n M e s s a g e ( m e s s a g e ) { d a t a = $ . p a r s e J S O N ( m e s s a g e . d a t a ) ; / * d o s o m e t h i n g w i t h d a t a * / } J A V A S C R I P T f u n c t i o n s e n d C o o r d i n a t e s ( ) { $ . p o s t ( ' / c h a n n e l ' , { x : c u r r e n t _ x , y : c u r r e n t _ y , c l i e n t : c l i e n t } ) ; } J A V A S C R I P T 33/46
34. Exercise 2 Building an API Backend
35. Implement a backend for the page below
36. Your mission @abahgat, #appsterdam Complete the code in the e n d p o i n t s directory of the package you downloaded earlier and implement the missing methods. Point your browser to h t t p : / / l o c a l h o s t : $ A P P _ P O R T / e n d p o i n t s to test your server. · · 36/46
37. Google Cloud Endpoints (experimental) Google Cloud Endpoints consists of tools, libraries and capabilities that allow you to generate APIs and client libraries from an App Engine application. @abahgat, #appsterdam 37/46
38. Create a service Annotate the API implementation class with the endpoints decorators, create an API server instance, and map the instance to the API URL @abahgat, #appsterdam @ e n d p o i n t s . a p i ( n a m e = ' m y a p i ' , v e r s i o n = ' v 1 ' , d e s c r i p t i o n = ' M y N e w A P I ' ) c l a s s M y N e w A p i ( r e m o t e . S e r v i c e ) : . . . P Y T H O N a p p l i c a t i o n = e n d p o i n t s . a p i _ s e r v e r ( [ M y N e w A p i ] , r e s t r i c t e d = F a l s e ) P Y T H O N h a n d l e r s : # E n d p o i n t s h a n d l e r - u r l : / _ a h / s p i / . * s c r i p t : s e r v i c e s . a p p l i c a t i o n Y A M L 38/46
39. Define the API methods Annotate methods with @abahgat, #appsterdam @ e n d p o i n t s . m e t h o d ( R e q u e s t M e s s a g e C l a s s , R e s p o n s e M e s s a g e C l a s s , n a m e = ' f o o . b a r ' , p a t h = ' / b a r ' , h t t p _ m e t h o d = ' G E T ' , . . . ) d e f b a r ( s e l f , r e q u e s t ) : . . . P Y T H O N R e q u e s t M e s s a g e C l a s s and R e s p o n s e M e s s a g e C l a s s are ProtoRPC definitions of the request and response classes, p a t h is the URL path of the endpoint, h t t p _ m e t h o d allows to map different functions to different HTTP methods · · · 39/46
40. Some closing notes on Endpoints @abahgat, #appsterdam Apps that use Cloud Endpoints expose discovery services at h t t p s : / / y o u r _ a p p _ i d . a p p s p o t . c o m / _ a h / a p i / d i s c o v e r y / v 1 / a p i s You can also use the APIs Explorer to experiment with your API by visiting h t t p s : / / y o u r _ a p p _ i d . a p p s p o t . c o m / _ a h / a p i / e x p l o r e r You can use the SDK to generate JavaScript, Android and iOS clients for your service, Endpoints can authenticate clients using OAuth 2.0, If you want to build a REST API, check out Endpoints Proto Datastore, and if you work with Android applications, check out the Mobile Backend Starter. · · · · · · 40/46
41. There's more
42. A few more advanced APIs @abahgat, #appsterdam XMPP – Integrate your app with Google Talk and Instant Message Clients. Search (experimental) – Build indexes for fast search over sets of document (which can be any object your app manipulates. Supports full text search and distance-based geographical search out of the box. Prospective Search (experimental) – Analyze a real-time feed of documents and be notified when anything matches one of your searches. · · · 42/46
43. Take your app to the next level http://www.flickr.com/photos/msimdottv/4339697089
44. Time for a Challenge Using the Search API to build a map-based application
45. Advanced Search @abahgat, #appsterdam Using the Search API, build a location aware system. Search for all the points that are closer than 10km from my position. Run a full text search on the items descriptions. · · · 45/46
46. <Thank You!> g+ plus.google.com/107973517098181615920 twitter @abahgat www www.abahgat.com github github.com/abahgat