The document discusses MongoDB and Spring Data integration. It provides examples of creating, querying, and commenting on documents using Spring Data and MongoDB. It also covers topics like replication, sharding, and eventual consistency in MongoDB.

1. MongoDB and Spring Data
Chris Harris
Twitter : cj_harris5
Email : charris@10gen.com
© 2012 SpringOne 2GX. All rights reserved. Do not distribute without permission.

2. About Me
Solution Architect at 10gen (the company behind MongoDB)
- Previous Roles:
• EMEA Architect at SpringSource
• EMEA Principal JBoss Consultant at RedHat
22

3. http://images.mirror.co.uk/upl/m4/mar2009/0/2/satnav-cliff-hanger-pic-ross-parry-
image-3-213726463.jpg

4. http://www.simpleadhdexpert.com/wp-content/uploads/2009/08/frustration.jpg

5. http://daddytypes.com/archive/duct_tape_baby_mianro.jpg

6. Is there a better way?

7. Terminology
RDBMS MongoDB
Table Collection
Row(s) JSON Document
Index Index
Join Embedding & Linking
Partition Shard
Partition Key Shard Key

8. As simple as possible, but no simpler
Memcached
Key / Value
Scalability & Performance
MongoDB
RDBMS
Depth of functionality

9. Lets build a Spring Data MongoDB App!

10. Welcome to Dev News
• User Story 1:
– As a user I should be able to create “News Articles”

11. What is a News Article?
{
title: “What is new in 2.2 MongoDB”,
date : new Date(),
author : “Fred”
text : “.......”
}

12. Example 1 - Create

13. Welcome to MongoDB News Dev
• User Story 1:
– As a user I should be able to create “News Articles”
• User Story 2:
– As a user I should be able to find a “News Articles” by Name

14. Example 2 - Query

15. Example 3 - Repo

16. Welcome to MongoDB News Dev
• User Story 1:
– As a user I should be able to create “News Articles”
• User Story 2:
– As a user I should be able to find a “News Articles” by Name
• User Story 3:
– As a user I should be able to comment on “News Articles”

17. What is a Comment?
{
title: “What is new in 2.2 MongoDB”,
date : new Date(),
author : “Fred”
text : “.......”
tags : [“mongodb”, “nosql”]
comments : [
{author : “chris”, text: “this is great” , date : new Date()},
{author : “tom”, text: “rock on”, date : new Date()}
]
}

18. Example 4 - Comments

19. Welcome to MongoDB News Dev
• User Story 1:
– As a user I should be able to create “News Articles”
• User Story 2:
– As a user I should be able to find a “News Articles” by Name
• User Story 3:
– As a user I should be able to comment on “News Articles”
• User Story 4:
–As a user I want to know how many comments are on a “Articles”

20. What is a Comment?
{
title: “What is new in 2.2 MongoDB”,
....
comments : [
{author : “chris”, text: “this is great” , date : new Date()},
{author : “tom”, text: “rock on”, date : new Date()}
],
comments: count : 2
}

21. Example 5 - Inc

22. “MongoDB lost my data!!”

23. Data: 125647383885969795743

24. Least durability - Don't use!
Driver MongoDB
write
apply in memory

25. Wait for Journal Sync - Same as RDBMS
Driver MongoDB
write
apply in memory
j:true
Write to journal

26. Replication
http://www.flickr.com/photos/10335017@N07/4570943043

27. Replica Set
• Data Protection
• Multiple copies of the data
• Spread across Data Centers, AZs
• High Availability
• Automated Failover
• Automated Recovery

28. Replica Sets
Write
Primary
Asynchronous Replication
Read
Java App Secondary
Secondary

29. Replica Sets
Write
Primary
Read
Java App Secondary
Secondary

30. Replica Sets
Primary
Write Automatic Election of new
Java App Primary Primary
Read
Secondary

31. Replica Sets
Recovering
Write New primary serves data
Java App Primary
Read
Secondary

32. Replica Sets
Secondary
Write
Java App Primary
Read
Secondary

33. Durability Summary Other Data
Memory Journal Secondary Center
RDBMS
Default
"Fire & Forget"
w=1
w=1
j=true
w="majority"
w=n
w="myTag"
Less More

34. Example 6 - Write Concern

35. Eventual Consistency
• http://www.flickr.com/photos/26095468@N04/3779692985

36. Understanding Eventual Consistency
Thread #1 Primary Secondary
Insert v1

37. Understanding Eventual Consistency
Thread #1 Primary Secondary
Insert v1
v1

38. Understanding Eventual Consistency
Thread #1 Primary Secondary
Insert v1
Read
v1

39. Understanding Eventual Consistency
Thread #1 Primary Secondary
Insert v1
reads v1 Read
v1

40. Understanding Eventual Consistency
Thread #1 Primary Secondary
Insert v1
reads v1 Read
v1
Update v2

41. Understanding Eventual Consistency
Thread #1 Primary Secondary
Insert v1
reads v1 Read
v1
Update v2
v2

42. Understanding Eventual Consistency
Thread #1 Primary Secondary
Insert v1
reads v1 Read
v1
Update v2
Read v2

43. Understanding Eventual Consistency
Thread #1 Primary Secondary
Insert v1
reads v1 Read
v1
Update v2
reads v2 Read v2

44. Understanding Eventual Consistency
Thread #1 Primary Secondary Thread #2
Insert v1
Read
v1
Update v2
Read v2

45. Understanding Eventual Consistency
Thread #1 Primary Secondary Thread #2
Insert v1
Read
v1
Update v2
Read v2

46. Understanding Eventual Consistency
Thread #1 Primary Secondary Thread #2
Insert v1
v1 does not
exist on
Read Secondary
v1
Update v2
Read v2

47. Understanding Eventual Consistency
Thread #1 Primary Secondary Thread #2
Insert v1
v1 does not
exist on
Read Secondary
v1
Update v2
Reads v1 but
Primary at v2
Read v2
Read v2

48. Example 7 - Eventual Consistency

49. http://community.qlikview.com/cfs-filesystemfile.ashx/__key/CommunityServer.Blogs.Components.WeblogFiles/theqlikviewblog/Cutting-Grass-with-Scissors-_2D00_-2.jpg

50. http://www.bitquill.net/blog/wp-content/uploads/2008/07/pack_of_harvesters.jpg

51. MongoDB Sharding
• Automatic partitioning and management
• Range based
• Convert to sharded system with no downtime
• Fully consistent

52. How mongoDB Sharding works
> db.runCommand({addshard: "shard1"});
> db.runCommand({shardCollection: "mydb.users",
key: {age: 1}})
-∞ +∞
• Range keys from -∞ to +∞
• Ranges are stored as "chunks"

53. How mongoDB Sharding works
> db.users.save({age: 40})
-∞ +∞
-∞ 40 41 +∞
• Data in inserted
• Ranges are split into more "chunks"

54. How mongoDB Sharding works
> db.users.save({age: 40})
> db.users.save({age: 50})
> db.users.save({age: 60})
-∞ +∞
-∞ 40 41 +∞
41 50 51 +∞
51 60 61 +∞

55. How mongoDB Sharding works
> db.runCommand({addshard: "shard2"});
> db.runCommand({addshard: "shard3"});
-∞ 40
41 50
51 60
61 +∞

56. How mongoDB Sharding works
> db.runCommand({addshard: "shard2"});
> db.runCommand({addshard: "shard3"});
shard1
-∞ 40
41 50
51 60
61 +∞

57. How mongoDB Sharding works
> db.runCommand({addshard: "shard2"});
> db.runCommand({addshard: "shard3"});
shard1 shard2 shard3
-∞ 40
41 50
51 60
61 +∞

58. Architecture
app app
Config Servers
mongos mongos
C1
C2
C3
Replica Set
mongod mongod mongod mongod
mongod mongod mongod mongod
mongod mongod mongod mongod
Shard 1 Shard 2 Shard 3 Shard 4

59. Balancing
mongos config
mongos
balancer
config
config
Data inserted
Imbalance all in a range
1 2 3 4
5 6 7 8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Shard 1 Shard 2 Shard 3 Shard 4

60. Balancing
mongos config
mongos
balancer
config
config
Move chunk 1
to Shard 2
1 2 3 4
5 6 7 8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Shard 1 Shard 2 Shard 3 Shard 4

61. Balancing
mongos config
balancer
config
config
1 2 3 4
5 6 7 8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Shard 1 Shard 2 Shard 3 Shard 4

62. Balancing
mongos config
balancer
config
config
2 3 4
5 6 7 8 1
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Shard 1 Shard 2 Shard 3 Shard 4

63. Balancing
mongos config
mongos
balancer
config
config
2 3 4
5 6 7 8 1
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Shard 1 Shard 2 Shard 3 Shard 4

64. Example 8 - Sharding

65. Questions
• MongoDB 2.2
– Improved concurrency
– Tag-aware sharding
– Aggregation framework
– TTL collections
• Free online MongoDB training
– Develop
– Deploy
– Classes start Oct. 2012