Talk i gave at Nosqlday with Giordano Scalzo on March 25th 2011. It's about how CouchDB can replace a full serverside mvc stack making development of simple web apps a piece of cake Also http://federico.galassi.net/ http://www.nosqlday.it/ http://couchdb.apache.org/ Follow me on Twitter! https://twitter.com/federicogalassi

1. CouchApps: Requiem for
Accidental Complexity
Federico Galassi Giordano Scalzo

2. We have a problem...

3. Writing software is
really hard...

4. A little bit of history

5. It wasn’t easy

6. A little bit better

7. Something happened

8. A different way of programming

9. Two tiers architecture
Business Logic + Data
Presentation

10. Three tiers architecture
Presentation Business Logic Data

11. Tim Berners Lee
invented the world wide web

12. Three tiers internet style
View
+ Model
Controller
Thin client

13. Evolution of
MVC Web App

14. Browser is a
thin client

15. Talking to a
smart server

16. It all starts with
an HTTP request
GET / HTTP/1.1
Host: example.org

17. It hits the
Controller

18. Web server parses it
Controller

19. Dispatch to
front controller
Controller

20. Routing
Controller

21. Custom action
Controller

22. Gets data
from Model

23. Query on
model objects
Model

24. ORM fits into SQL
Model

25. Hits a RDBMS
Model

26. Populates a
View

27. Template engine
View

28. HTML back to
the server
View

29. HTML back to
the client
HTTP/1.1 200 OK

30. That’s MVC
Model
View
Controller

31. A little bit old school

32. We love AJAX speed

33. Just need an API
Model
View Json View
Controller Api Action

34. And some
javascript on client
Model
View Json View
Javascript View
Controller Api Action

35. Nice
one ring to rule ‘em all

36. No
contraindications ?

37. Accidental
complexity

38. Every change
touches the server

39. Hard to scale
We must
add another
serveeeeerrrr

40. Last technology cycle
WE WERE HERE
MVC peak of
inflated
expectation
Visibility
productivity
disillusionment obsolescence
technology
trigger
maturity

41. Last technology cycle
peak of
inflated
expectation
NOW HERE
Visibility
productivity
disillusionment obsolescence
technology
trigger
maturity

42. Last technology cycle
peak of
inflated
expectation
IF YOU’RE
Visibility
AT THIS CONF
productivity
YOU MAY BE
ALREADY HERE
disillusionment obsolescence
technology
trigger
maturity

43. Next technology to save us?
?
Visibility
maturity

44. It’s a cycle
but we know one thing ...
Visibility
maturity

45. Specialization
is
Good

48. Very opinionated
document DB

49. Very good for
some problems

50. A document DB
{
"company": "CleanCode",
"members": [
{ "name": "Gabriele Lana", "role": "software craftsman"},
{ "name": "Federico Galassi", "role": "software craftsman"},
{ "name": "Giordano Scalzo", "role": "software craftsman"}
]
}

51. Self contained data
INS
J O
NO

52. Schema-less data
DATA
YO UR
VO LVE
E

53. Incremental
Reduce: sum(checkouts)
Map/Reduce
430
Re-reduce
142 288
Reduce 100 42 215 73
{ { { {
Map "id": 1,
"day": 20100123,
"checkout": 100
"id": 2,
"day": 20100123,
"checkout": 42
"id": 3,
"day": 20100123,
"checkout": 215
"id": 4,
"day": 20100123,
"checkout": 73
} } } }

54. Multi-Version
Concurrency Control

55. Crash-only
architecture
lucky by design

56. A distributed DB

57. Eventual
consistency

58. Incremental replication

59. Automatic conflict
resolution

60. Built of the Web
“Django may be built for the Web,
but CouchDB is built of the Web.
I’ve never seen software that so
Jacob Kaplan-Moss
completely embraces the Co-creator of Django
philosophies behind HTTP.”

61. Restful API
GET / Returns MOTD
GET /_all_dbs List of databases
POST /_restart Restart the server
GET /_log Tail of the server’s log
GET /_config Entire server config
GET /_config/<section>/<key> Single config value
PUT /_config/<section>/<key> Set a single config value
GET /<db> Database info
PUT /<db> Create new database
DELETE /<db> Delete database
GET /<db>/<doc> Latest revision of the document
PUT /<db>/<doc> Insert a new revision of the document
... and everything else

62. Javascript to
program
// MAP
function(doc) {
if(doc.date && doc.title) {
emit(doc.date, doc.title);
}
}

63. JSON to
exchange data
{
"_id":"hello-­‐world",
"_rev":"43FBA4E7AB",
"title":"Hello World",
"body":"Well hello and welcome to my new blog...",
"date":"2009/01/15 15:52:20"
}

64. Applications
are
documents

65. Replication
as
deploy

66. A modern web
application server

67. CouchApps are
javascript and html5
applications served
directly from CouchDB

68. Problem
Model
View Json View
Javascript View
Controller Api Action

69. Simple Solution
HTTP
Javascript View

70. Experiment:
5 minutes comet chat

71. The couchapp tool

72. Generate the app

73. Configure the app

74. Deploy the app

75. That’s it

76. That’s it

77. User can post a message
Add form elements

78. User can post a message
On click POST message to couch

79. User can post a message
Yes!

80. User gets a stream of messages
Add messages container

81. User gets a stream of messages

82. User gets a stream of messages
Yes!

83. Validation?

84. Authentication?

85. Authentication?
Create a user

86. Authentication?
Add Form Elements

87. Authentication?
HTTP Basic Auth

88. Authentication?
If it goes wrong

89. Authentication?
Check sender is the authenticated user

90. Authentication?
{ sender: “whitehouse” } // spoofing

91. Authentication?
Yes!

92. BASIC HTTP ?????
No SSL
Yes cookie auth
via _session api

93. UGLY URLS ?????
Rewrites and
Virtual hosts

94. Easy eh?

95. But it’s not that ring

96. Very good for
CRUD/small/simple
web

98. federico.galassi@cleancode.it giordano.scalzo@cleancode.it
twitter.com/federicogalassi twitter.com/giordanoscalzo
slideshare.net/fgalassi slideshare.net/giordano