Video and slides synchronized, mp3 and slide download available at URL http://bit.ly/1gtG0yb. Jafar Husain explains how Netflix uses reactive programming to build and consume REST endpoints, and how they work around the limitations of the HTTP protocol to create high-performance REST APIs. Filmed at qconsf.com. Jafar Husain has been working as a software developer for 16 years. He's developed software for companies like GE, Microsoft, and Netflix. He specializes in building web servers and clients using functional reactive programming, and was the first user of the Reactive Extensions Framework. He's also responsible for "Falkor", a RESTful data access framework that powers most Netflix clients.

1. +
JSONG
JSONGPath
HTTP
Path Evaluators
Reactive REST
RESTful API for Application Data

2. Watch the video with slide
synchronization on InfoQ.com!
http://www.infoq.com/presentations
/netflix-reactive-rest
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Highlights
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4. +
The is the story…
…of how we freed REST from HTTP...
…and discovered it was even more
Powerful than we thought it was.

5. +
Netflix

6. +
Question
What’s the most successful distributed system designed for
information browsing?

7. +
Answer

8. +
WWW Caching
index.html
Browser
Cache
index.html
index.html
cnn.com

9. +
REST

Unique ID for every resource

Idempotent VERBS

GET

PUT

10. +
REST Benefits

Cache Transparency

Cache Coherence

11. +
REST + HTTP: Two great tastes

Unique ID for every resource (URL)

Idempotent VERBS



GET
PUT
Cache Control Headers for Invalidation

12. +
Netflix is a web application…
Why not use the browser cache for our data?

13. +
Why not the Browser Cache?
http://netflix.com/videos/234234
http://netflix.com/videos/234234/rating
http://netflix.com/videos/54325
http://netflix.com/videos/54325/rating
http://netflix.com/videos/12356/name
http://netflix.com/videos/12356/rating
http://netflix.com/videos/876456/name
http://netflix.com/videos/876456/rating
Too many HTTP requests!

14. +
Challenge
Can we build a high-performance REST API for our data?

15. +
Introducing Falkor

RESTful Query API for Data

Coherent, Transparent, Managed Cache

Efficient bulk data transfer over HTTP

Query Optimization

16. +
Netflix Domain Model

17. +
Netflix Domain Model
http://netflix.com/user
{
videoLists: [
[
{
name: “Die hard”,
rating: 4.0
},
// more titles
],
[
{
name: “Die hard”,
rating: 4.0
},
// more titles
],
// more lists…
]
}

18. +
RESTful Data Access API
var userModel = {
videoLists: {
“0”: {
“name”: “Thrillers”,
“0”: {
id: 2654,
name: “Die hard”,
rating: 4.0
},
// more titles
length: 74,
}
}
}
userModel[‘videoLists’][0][0][‘name’]
[‘videoLists’, 0, 0, ‘name’]

19. +
Building a Proxy for a Remote Model
// Create a proxy or the current user’s domain model
var remoteModel =
new RemotePathEvaluator(“http://netflix.com/user”);
Server Path Evaluator
Falkor Server
Remote Path Evaluator

20. +
Retrieving Data from the Server
// Retrieve the name of the first title in the first genre list.
var remoteModel.
get([“videoLists”,0,0,”name”]).
forEach(function(pathBoundValue) {
console.log(pathBoundValue);
});
[“videoLists”,0,0,”name”]
{
path: [“videoLists”,0,0,”name”],
value: “Die Hard”
}
netflix.com/user

21. +
Retrieving Sub Graph
// Retrieve the names of the first 10 title in the first
// 10 genre lists.
var remoteModel.
get([“videoLists”,{from:0,to:9},{from:0,to:9},”name”]).
forEach(function(pathBoundValue) {
console.log(pathBoundValue);
});
>
>
>
>
>
{path: [“videoLists”,0,0,”name”],
{path: [“videoLists”,0,1,”name”],
// snip
{path: [“videoLists”,9,8,”name”],
{path: [“videoLists”,9,9,”name”],
value: “Die Hard”}
value: “Amelie”}
value: “The New Guys”}
value: “Animal House”}

22. +
Caching Data
// Create a proxy or the current user’s domain model
var remoteModel =
new RemotePathEvaluator(“http://netflix.com/user”);
// Create a path evaluator for a local, in-memory cache.
// Cache uses LRU to ensure size stays < 10000.
var localModel = new SizedMemoryPathEvaluator(10000, {});
// Create a cached path evaluator, using the remoteModel as the
// source and the in-memory model as the cache.
var cachedModel = remoteModel.cache(localModel);

23. +
Caching Data on the Client
Client Memory
Server Path Evaluator
Falkor Server
Sized Memory Path Evaluator
Remote Path Evaluator
Cached Path Evaluator

24. +
Retrieving Cached Data
var cachedModel.
get([“videoLists”,0,0,”name”]).
forEach(function(pathBoundValue) {
console.log(pathBoundValue.value);
});
[“videoLists”,0,0,”name”]
{
path: [“videoLists”,0,0,”name”],
value: “Die Hard”
}
Local
Cache
Cache
[“videoLists”,0,0,”name”]

25. +
Retrieving Cached Data
var cachedModel.
get([“videoLists”,0,0,”name”]).
forEach(function(pathBoundValue) {
console.log(pathBoundValue.value);
});
[“videoLists”,0,0,”name”]
{
path: [“videoLists”,0,0,”name”],
value: “Die Hard”
}
Local
Cache
Cache

26. +
Query Optimization
// Query for another video property can be optimized!
var cachedModel.
get([“videoLists”,0,0,”rating”]).
forEach(function(pathBoundValue) {
console.log(pathBoundValue.value);
});
Query is transparently optimized!
[“videoLists”,0,0,”rating”]
{
path: [“videoLists”,0,0,”rating”],
value: “Die Hard”
}
Local
Cache
Cache
[“videos”,234234,”rating”]

27. +
Question
So how does it work?

28. +
Features

Efficient data transfer over HTTP

Cache Coherence

Cache Transparency

Query Optimization

29. +
One Resource/One Domain Model
http://netflix.com/videos/234234/name
http://netflix.com/videos/234234/rating
http://netflix.com/videos/54325/name
http://netflix.com/user?path=[“videos”,234,”name”]&path=…
http://netflix.com/videos/54325/rating
http://netflix.com/videos/12356/name
http://netflix.com/videos/12356/rating
http://netflix.com/videos/876456/name
http://netflix.com/videos/876456/rating

30. +
Features

Efficient data transfer over HTTP

Cache Coherence

Cache Transparency

Query Optimization

31. +
Netflix Domain Model
http://netflix.com/user
{
videoLists: {
“0”: {
“name”: “Thrillers”,
“0”: {
name: “Die hard”,
rating: 4.0
},
// more titles
length: 74,
},
“1”: {
“name”: “Action Movies”,
“0”: {
name: “Die hard”,
rating: 4.0
},
// more titles
length: 74
}, // more lists…
length: 25
}
}

32. +
What’s wrong with JSON?
“videoLists”
“0”
“0”
“name”
“Die Hard”
“1”
“0”
Same movie appears
twice in the same message!
“name”
“Die Hard”

33. +
The Problem
How to model a graph in JSON?

34. +
Introducing JSON Graph (JSONG)

35. +
JSONG

Graph representation language in JSON

Two types:
1.
Maps
2.
Values (includes Arrays)

36. +
JSONG Benefits

Serializable

Partitionable

37. +
JSON
http://netflix.com/user
{
videoLists: {
“0”: {
“name”: “Thrillers”,
“0”: {
id: 2654,
name: “Die hard”,
rating: 4.0
},
// more titles
length: 74,
},
“1”: {
“name”: “Action Movies”,
“0”: {
id: 2654,
name: “Die hard”,
rating: 4.0
},
// more titles
length: 74
}, // more lists…
length: 25
}
}

38. +
JSONG
http://netflix.com/user
{
videoLists: {
“0”: {
“name”: “Thrillers”,
“0”: [“videos”, 2654],
// more titles
length: 74,
},
“1”: {
“name”: “Action Movies”,
“0”: [“videos”, 2654],
// more titles
length: 74
}, // more lists…
length: 25
},
videos: {
2654: {
name: “Die hard”,
rating: 4.0
}
}
}

39. +
Okay so we’ve got a graph…
…now we need a convenient API for querying data.

40. +
Hierarchical API
var userModel = {
videoLists: {
“0”: {
“name”: “Thrillers”,
“0”: {
id: 2654,
name: “Die hard”,
rating: 4.0
},
// more titles
length: 74,
}
}
}
JSONG Path
userModel[‘videoLists’][0][0][‘name’]
[‘videoLists’, 0, 0, ‘name’]

41. +
JSONG Path Evaluation
var netflixUser = {
videoLists: {
“0”: {
name: “Thrillers”,
“0”: [“videos”,234],
// more videos…
length: 75
},
“1”: {
name: “Action Movies”,
“0”: [“videos”,234],
// more videos…
length: 75
},
// more lists…
length: 15
},
videos: {
234: {name: “Die Hard”, rating:5}
}
}
[“videoLists”,0,0,”name”]

42. +
JSONG Path Evaluation
var netflixUser = {
videoLists: {
“0”: {
name: “Thrillers”,
“0”: [“videos”,234],
// more videos…
length: 75
},
“1”: {
name: “Action Movies”,
“0”: [“videos”,234],
// more videos…
length: 75
},
// more lists…
length: 15
},
videos: {
234: {name: “Die Hard”, rating:5}
}
}
[“videoLists”,0,0,”name”]

43. +
JSONG Path Evaluation
var netflixUser = {
videoLists: {
“0”: {
name: “Thrillers”,
“0”: [“videos”,234],
// more videos…
length: 75
},
“1”: {
name: “Action Movies”,
“0”: [“videos”,234],
// more videos…
length: 75
},
// more lists…
length: 15
},
videos: {
234: {name: “Die Hard”, rating:5}
}
}
[“videoLists”,0,0,”name”]

44. +
JSONG Path Evaluation
var netflixUser = {
videoLists: {
“0”: {
name: “Thrillers”,
“0”: [“videos”,234],
// more videos…
length: 75
},
“1”: {
name: “Action Movies”,
“0”: [“videos”,234],
// more videos…
length: 75
},
// more lists…
length: 15
},
videos: {
234: {name: “Die Hard”, rating:5}
}
}
[“videoLists”,0,0,”name”]

45. +
JSONG Path Evaluation
var netflixUser = {
videoLists: {
“0”: {
name: “Thrillers”,
“0”: [“videos”,234],
// more videos…
length: 75
},
“1”: {
name: “Action Movies”,
“0”: [“videos”,234],
// more videos…
length: 75
},
// more lists…
length: 15
},
videos: {
234: {name: “Die Hard”, rating:5}
}
}
Array found before last key
evaluated…
[“videoLists”,0,0,”name”]

46. +
JSONG Path Evaluation
var netflixUser = {
videoLists: {
“0”: {
name: “Thrillers”,
“0”: [“videos”,234],
// more videos…
length: 75
},
“1”: {
name: “Action Movies”,
“0”: [“videos”,234],
// more videos…
length: 75
},
// more lists…
length: 15
},
videos: {
234: {name: “Die Hard”, rating:5}
}
}
Array must be a path!
[“videoLists”,0,0,”name”]

47. +
JSONG Path Evaluation
var netflixUser = {
videoLists: {
“0”: {
name: “Thrillers”,
“0”: [“videos”,234],
// more videos…
length: 75
},
“1”: {
name: “Action Movies”,
“0”: [“videos”,234],
// more videos…
length: 75
},
// more lists…
length: 15
},
videos: {
234: {name: “Die Hard”, rating:5}
}
}
Array must be a path!
[“videos”,234,”name”]

48. +
JSONG Path Evaluation
var netflixUser = {
videoLists: {
“0”: {
name: “Thrillers”,
“0”: [“videos”,234],
// more videos…
length: 75
},
“1”: {
name: “Action Movies”,
“0”: [“videos”,234],
// more videos…
length: 75
},
// more lists…
length: 15
},
videos: {
234: {name: “Die Hard”, rating:5}
}
}
Rewrite path, and start
evaluating from top node.
[“videos”,234,”name”]

49. +
JSONG Path Evaluation
var netflixUser = {
videoLists: {
“0”: {
name: “Thrillers”,
“0”: [“videos”,234],
// more videos…
length: 75
},
“1”: {
name: “Action Movies”,
“0”: [“videos”,234],
// more videos…
length: 75
},
// more lists…
length: 15
},
videos: {
234: {name: “Die Hard”, rating:5}
}
}
[“videos”,234,”name”]

50. +
JSONG Path Evaluation
var netflixUser = {
videoLists: {
“0”: {
name: “Thrillers”,
“0”: [“videos”,234],
// more videos…
length: 75
},
“1”: {
name: “Action Movies”,
“0”: [“videos”,234],
// more videos…
length: 75
},
// more lists…
length: 15
},
videos: {
234: {name: “Die Hard”, rating:5}
}
}
[“videos”,234,”name”]

51. +
JSONG Path Evaluation
var netflixUser = {
videoLists: {
“0”: {
name: “Thrillers”,
“0”: [“videos”,234],
// more videos…
length: 75
},
“1”: {
name: “Action Movies”,
“0”: [“videos”,234],
// more videos…
length: 75
},
// more lists…
length: 15
},
videos: {
234: {name: “Die Hard”, rating:5}
}
}
[“videos”,234,”name”]

52. +
Okay…
…how do we make this process transparent to the developer?

53. +
Features

Efficient data transfer over HTTP

Cache Coherence

Cache Transparency

Query Optimization

54. +
Path Evaluator
Path Evaluator
get(Observable<Path>): Observable<PathBoundValue>
set(Observable<PathBoundValue>): Observable<PathBoundValue>
delete(Observable<Path>): Observable<PathBoundValue>

55. +
Observable
 Object
 Open
that represents stream of data
Source Reactive Extensions Library
 Ported
to
 Javascript
 .NET
C
 Java (Netflix)

56. +
Observable.forEach
// “subscribe”
var subscription =
remoteModel.get([“videoLists”,0,0,”name”]).
forEach(
event => console.log(event),error
error => console.error(error),
() => console.log(“done”));
// “unsubscribe”
subscription.dispose();
optional

57. +
Path Evaluator

Proxy for a JSONG Model

Idempotent Operations:


Set


Get
Delete
Composable

58. +
Path Evaluator Implementations

RemotePathEvaluator

SizedMemoryPathEvaluator

CachedPathEvaluator

LocalStoragePathEvaluator?

etc

59. +
Accessing Data on the Client
// Create a Proxy path evaluator for the server JSONG domain model
var remoteModel =
new RemotePathEvaluator(“http://netflix.com/tvui/user”);`

60. +
Accessing Data on the Client
// Create a Proxy path evaluator for the server JSONG domain model
var remoteModel =
new RemotePathEvaluator(“http://netflix.com/tvui/user”);`
Server Path Evaluator
Remote Path Evaluator

61. +
Accessing Data on the Client
// Create a Proxy path evaluator for the server JSONG domain model
var remoteModel =
new RemotePathEvaluator(“http://netflix.com/tvui/user”);
remoteModel.get([“videoLists”,{to:5},{to:10},”name”]).
forEach(function(pathBoundValue) { /* do something */ });
Server Path Evaluator
[videoLists,{to:5},{to:10},’name’]
Remote Path Evaluator

62. +
Accessing Data on the Client
// Create a Proxy path evaluator for the server JSONG domain model
var remoteModel =
new RemotePathEvaluator(“http://netflix.com/tvui/user”);
remoteModel.get([“videoLists”,{to:5},{to:10},”name”]).
forEach(function(pathBoundValue) { /* do something */ });
Server Path Evaluator
{ path: [“videoLists”,0,0,”name”], value: {…} }
{ path: [“videoLists”,0,1,”name”], value: {…} }
…
{ path: [“videoLists”,5,10,”name”], value: {…} }
Remote Path Evaluator

63. +
Caching Data on the Client
// Create a Proxy path evaluator for the server JSONG domain model
var remoteModel =
new RemotePathEvaluator(“http://netflix.com/tvui/user”);
// Create a path evaluator for a local, in-memory cache.
// Cache stores the fragments of the remote model and stays within
// size of 10000.
var localModelCache = new SizedMemoryPathEvaluator(10000, {});
Client Memory
Server Path Evaluator
Sized Memory Path Evaluator
Remote Path Evaluator

64. +
Sized Memory Path Evaluator

Works like a web browser cache!

Caches resources by path

Removes least-recently used resources

65. +
Caching Data on the Client
// Create a Proxy path evaluator for the server JSONG domain model
var remoteModel =
new RemotePathEvaluator(“http://netflix.com/tvui/user”);
// Create a path evaluator for a local, in-memory cache.
// Cache stores the fragments of the remote model and stays within
// size of 10000.
var localModel = new SizedMemoryPathEvaluator(10000, {});
// Create a cached path evaluator, using the remoteModel as the
// source and the in-memory model as the cache.
var cachedModel = remoteModel.cache(localModel);

66. +
Caching Data on the Client
Client Memory
Server Path Evaluator
Falkor Server
Sized Memory Path Evaluator
Remote Path Evaluator
Cached Path Evaluator
[videoLists,{to:5},{to:10},’name’]

67. +
Caching Data on the Client
Client Memory
Server Path Evaluator
Falkor Server
Sized Memory Path Evaluator
Remote Path Evaluator
Cached Path Evaluator

68. +
Caching Data on the Client
Client Memory
Server Path Evaluator
Falkor Server
Sized Memory Path Evaluator
Remote Path Evaluator
[videoLists,{to:5},{to:10},’name’]`
Cached Path Evaluator

69. +
Caching Data on the Client
Client Memory
Server Path Evaluator
Falkor Server
Sized Memory Path Evaluator
Remote Path Evaluator
Nothing
Cached Path Evaluator

70. +
Caching Data on the Client
Client Memory
Server Path Evaluator
Falkor Server
Sized Memory Path Evaluator
Remote Path Evaluator
[videoLists,{to:5},{to:10},’name’]
Cached Path Evaluator

71. +
Caching Data on the Client
Client Memory
Server Path Evaluator
Falkor Server
Sized Memory Path Evaluator
Remote Path Evaluator
{ path: [“videoLists”,0,0,”name”], value: {…} }
{ path: [“videoLists”,0,1,”name”], value: {…} }
…
{ path: [“videoLists”,5,10,”name”], value: {…} }
Cached Path Evaluator

72. +
Caching Data on the Client
Client Memory
Server Path Evaluator
Falkor Server
Sized Memory Path Evaluator
Remote Path Evaluator
{ path: [“videoLists”,0,0,”name”], value: {…} }
{ path: [“videoLists”,0,1,”name”], value: {…} }
…
{ path: [“videoLists”,5,10,”name”], value: {…} }
Cached Path Evaluator

73. +
Caching Data on the Client
Client Memory
var netflixMember = {
videoLists: {
name: “Action Movies”,
“0”: [“lists”, 54354334],
// more lists…
“length: 15
},
“videos”: {
“34123432”:
{ … }
}
}
Server Path Evaluator
Falkor Server
Sized Memory Path Evaluator
Remote Path Evaluator
Cached Path Evaluator
{ path: [“videoLists”,0,0,”name”], value: {…} }
{ path: [“videoLists”,0,1,”name”], value: {…} }
…
{ path: [“videoLists”,5,10,”name”], value: {…} }

74. +
Features

Efficient data transfer over HTTP

Cache Coherence

Cache Transparency

Query Optimization

75. +
Query Optimization

76. +
Query Optimization
Client Memory
Server Path Evaluator
var netflixMember = {
videoLists: {
name: “Action Movies”,
“0”: [“lists”, 54354334],
// more lists…
“length: 15
},
“videos”: {
“34123432”:
{ … }
}
}
TV Path Evaluator
Falkor Server
Sized Memory Path Evaluator
Remote Path Evaluator
Cached Path Evaluator
[videoLists,1,3,’rating’]

77. +
Query Optimization
Client Memory
Server Path Evaluator
var netflixMember = {
videoLists: {
name: “Action Movies”,
“0”: [“lists”, 54354334],
// more lists…
“length: 15
},
“videos”: {
“34123432”:
{ … }
}
}
TV Path Evaluator
Falkor Server
Sized Memory Path Evaluator
Remote Path Evaluator
Cached Path Evaluator
[videoLists,1,3,’rating’]

78. +
Query Optimization
Client Memory
Server Path Evaluator
var netflixMember = {
videoLists: {
name: “Action Movies”,
“0”: [“lists”, 54354334],
// more lists…
“length: 15
},
“videos”: {
“34123432”:
{ … }
}
}
TV Path Evaluator
Falkor Server
Sized Memory Path Evaluator
Remote Path Evaluator
[videoLists,1,3,’rating’]
Cached Path Evaluator
[videoLists,1,3,’rating’]

79. +
Query Optimization
Client Memory
Server Path Evaluator
var netflixMember = {
videoLists: {
name: “Action Movies”,
“0”: [“lists”, 54354334],
// more lists…
“length: 15
},
“videos”: {
“34123432”:
{ … }
}
}
TV Path Evaluator
Falkor Server
Sized Memory Path Evaluator
Remote Path Evaluator
{path: [videoLists,1], value: [lists,23432] }
{path: [lists,23432,0], value: [movies,234234] }
Cached Path Evaluator
[videoLists,1,3,’rating’]

80. +
Query Optimization
Client Memory
Server Path Evaluator
var netflixMember = {
videoLists: {
name: “Action Movies”,
“0”: [“lists”, 54354334],
// more lists…
“length: 15
},
“videos”: {
“34123432”:
{ … }
}
}
TV Path Evaluator
Falkor Server
Sized Memory Path Evaluator
Remote Path Evaluator
[movies,234234,rating]
Cached Path Evaluator
Path optimized!!

81. +
Query Optimization

Path partially evaluated in the cache

Path is rewritten and optimized before it is sent to server

82. +
Query Optimization Rocks!
Same API for local and remote data!

83. +
Features

Efficient data transfer over HTTP

Cache Coherence

Cache Transparency

Query Optimization

84. +
Roadmap

Currently Internal Software

Defensive Patent Filed

Plan to open-source 2014

85. +
Questions?

86. Watch the video with slide synchronization on
InfoQ.com!
http://www.infoq.com/presentations/netflixreactive-rest