Introduction to CouchDB presented by Jonathan Weiss at BarCampRuhr4

1. CouchDB
A Database for the Web
Jonathan Weiss

2. Who am I?
Working for Peritor in Berlin, Germany
Written, maintain, or involved in
 Webistrano
 Capistrano
 SimplyStored
 Happening
 The great fire of London
http://github.com/jweiss
@jweiss
2

3. Scalarium
Amazon EC2 Cluster Management
 Auto-config
 Self-Healing
 Auto-Scaling
 One-click-deployment
www.scalarium.com
3

4. Database Requirements
High Availability
Easy Replication
Clustering
Robustness
Short Recovery Time
4

5. 5

6. CouchDB
Build for the Web
Scales
Replication built-in
Embracing offline
Flexible schema – document DB
6

7. ”CouchDB is built of the Web“
Jacob Kaplan-Moss
7

8. Web Technologies
HTTP
the access protocol
JavaScript
the query language
JSON
the storage format
8

9. JSON Document
{
"_id": "BCCD12CBB",
"_rev": "1-AB764C",
"type": "person",
"name": "Darth Vader",
"age": 63,
"headware": ["Helmet", "Sombrero"],
"dark_side": true,
"weapons": {
"right_arm": "light_saber",
"left_arm": null
}
}
9

10. JSON Document
{
"_id": "BCCD12CBB",
"_rev": "1-AB764C",
"type": "person",
"name": "Darth Vader",
"age": 63,
"headware": ["Helmet", "Sombrero"],
"dark_side": true,
"weapons": {
"right_arm": "light_saber",
"left_arm": null
}
}
10

11. JSON Document
{
"_id": "BCCD12CBB",
"_rev": "1-AB764C",
"type": "person",
"name": "Darth Vader",
"age": 63,
"headware": ["Helmet", "Sombrero"],
"dark_side": true,
"weapons": {
"right_arm": "light_saber",
"left_arm": null
}
}
11

12. No Tables or Namespaces
12

13. No Tables or Namespaces
13

14. Manual Namespacing
{
"_id": "BCCD12CBB",
"_rev": "1-AB764C",
"type": "person",
"name": "Darth Vader",
"age": 63,
"headware": ["Helmet", "Sombrero"],
"dark_side": true,
"weapons": {
"right_arm": "light_saber",
"left_arm": null
}
}
14

15. Interacting with CouchDB
JSON
HTTP Client
PUT /dbname/ID
15

16. Interacting with CouchDB
GET /dbname/ID
HTTP Client
JSON
16

17. Interacting with CouchDB
DELETE /dbname/ID
HTTP Client
17

18. Views
18

19. Design Document
{
"id": "_design/hats”,
"_rev": "431212AB4”,
"language": "javascript”,
"views": {
"all": {
"map": "function(doc){ .... }”,
"reduce": "function(doc){ .... }”
},
"by_manufacturer": {
"map": "function(doc){ .... }”,
"reduce": "function(doc){ .... }”
}
}
} 19

20. Design Document
{ Document ID
"id": "_design/hats”, –
"_rev": "431212AB4”, prefixed by “_design/”
"language": "javascript”,
"views": {
"all": {
"map": "function(doc){ .... }”,
"reduce": "function(doc){ .... }”
},
"by_manufacturer": {
"map": "function(doc){ .... }”,
"reduce": "function(doc){ .... }”
}
}
} 20

21. Design Document
{
"id": "_design/hats”,
"_rev": "431212AB4”,
"language": "javascript”,
"views": {
"all": { Hash of Views
"map": "function(doc){ .... }”,
"reduce": "function(doc){ .... }”
},
"by_manufacturer": {
"map": "function(doc){ .... }”,
"reduce": "function(doc){ .... }”
}
}
} 21

22. Design Document
{
"id": "_design/hats”,
"_rev": "431212AB4”,
"language": "javascript”,
"views": {
"all": { Hash of Views
"map": "function(doc){ .... }”, Every view has map &
"reduce": "function(doc){ .... }” reduce function
},
"by_manufacturer": {
"map": "function(doc){ .... }”,
"reduce": "function(doc){ .... }”
}
}
} 22

23. Map
function(doc) {
if (doc.headware) {
for (var hat in doc.headware) {
emit(hat, 1);
}
}
}
23

24. Map
Passed every
document in the DB
function(doc) {
if (doc.headware) {
for (var hat in doc.headware) {
emit(hat, 1);
}
}
}
24

25. Map
function(doc) {
if (doc.headware) {
Inspects
for (var hat in doc.headware) { & Decides
emit(hat, 1);
}
}
}
25

26. Map
function(doc) {
if (doc.headware) {
for (var hat in doc.headware) {
emit(hat, 1);
}
} Emits result
} for index
26

27. Reduce
function(keys, values, rereduce) {
return sum(values);
}
27

28. Reduce
Passed map result
(or partial reduce result)
function(keys, values, rereduce) {
return sum(values);
}
28

29. Reduce
function(keys, values, rereduce) {
return sum(values);
}
Aggregates
(count, sum, average, …)
29

30. Example Map Result
Map functions are similar to SQL indices
ID KEY VALUE
51ABFA211 Cap 1
ABC123456 Cappy 1
BCCD12CBB Helmet 1
BCCD12CBB Sombrero 1
Sorted by the key
Key can also be an array
Value can be complex JSON and/or reference to other document
30

31. Query a view
GET /dbname/_design/hats/_view/all
HTTP Client
{"total_rows":348,"offset":0,"rows”:[
{"id":"A","key":"A","value":1},
{"id":"B","key":"B","value":1},
]}
31

32. Query a view
GET /dbname/_design/hats/_view/all?
include_docs=true
HTTP Client
32

33. View Query
Filter by
 key=ABC123
 startkey=123 & endkey=9
 limit=100
 descending=true
 group=true
 reduce=true
 Include_docs=true
33

34. SQL vs. JavaScript
Vs.
34

35. Using Couch from PHP
Several options available
 PHPillow:
http://arbitracker.org/phpillow.html (LGPL 3)
 PHP Object_Freezer:
https://github.com/sebastianbergmann/php-object-freezer/tree (BSD)
 PHP On Couch:
http://github.com/dready92/PHP-on-Couch/tree/master (GPLv2 or v3)
 PHP CouchDB Extension:
http://www.topdog.za.net/php_couchdb_extension (PHP License 3.0)
 Sag for CouchDB:
http://www.saggingcouch.com/ (Apache License 2.0)
35

36. 36

37. 37

38. 38

39. 39

40. SimplyStored
CouchDB convenience Layer for Ruby
 Models & Associations
 Validations
 Callbacks BSD-licensed on
 Dynamic finder http://github.com/peritor/simply_stored
 S3 attachments On top of CouchPotato, CouchRest & RestClient
 Paranoid delete
 ActiveModel compliant
40

41. Many more
Or just build your own using HTTP!
41

42. Database Requirements
High Availability
Easy Replication
Clustering
Robustness
Short Recovery Time
42

43. Replication
B-Tree
XXXXX
Photo by Mathias Meyer
43

44. B-Tree
Append only
Concurrency (MVCC)
Crash resistant
Hot backups
Compaction
44

45. Replication
45

46. CouchDB Replication
POST /_replicate
POST /_replicate
Eventually consistent & conflict resolution
46

47. Load Balancing
Replication
HTTP Client HTTP Load
Balancer
47

48. Caching
HTTP Client HTTP Cache
Varnish
Apache
…
48

49. Multi-Master
49

50. BigCouch
 Clustered CouchDB:
Many CouchDBs appear as one
 Modeled after Amazon Dynamo
 Scalability like Cassandra or Riak
 github.com/cloudant/bigcouch
50

51. Q – No. of partitions
BigCouch
N – No. of replicas
R – Read quorum
W – Write quorum
51

52. Various
CouchApps
Validations
Filtered replication
Changes feed
List functions
Futon
Geo
Fulltext-Search with embedded Lucene
Different experimental View-Server
52

53. Q&A
Peritor GmbH
Blücherstr. 22, Hof III Aufgang 6
10961 Berlin
Tel.: +49 (0)30 69 20 09 84 0
Fax: +49 (0)30 69 20 09 84 9
Internet: www.peritor.com
E-Mail: info@peritor.com
© Peritor GmbH - Alle Rechte vorbehalten