This slides was presented at Mydbops Database Meetup 4 on Aug-03 2019 by Vinodh Krishnaswamy ( Percona ). This talk focuses on when to go for sharing topology in MongoDB and their benefits and impact.

1. © 2019 Percona1
Vinodh Krishnaswamy
MongoDB Sharded Cluster - How to
design your topology
Support Engineer - MongoDB & MySQL
Percona

2. © 2019 Percona2
◆ Started as MySQL DB DBA
◆ Support for MongoDB
◆ Trainer
◆ Scripting, Reading, Driving
◆ “Guruji” - who shares knowledge
◆ Now here I am - Perconian!!!
Who am I

3. © 2019 Percona3
Agenda
▪ Sharded Cluster - components
▪ Ranged Sharding
▪ Hashed Sharding
▪ Zones / Tags

4. © 2019 Percona4
Agenda
▪ ReplicaSet - Key points
▪ Topology
▪ Q&A

5. © 2019 Percona5
Sharded Cluster

6. © 2019 Percona6
Sharded Cluster
▪ Horizontal Scaling
• Data across multiple nodes
• Reduce stress for larger working set
• Ability to add more servers
• HA

7. © 2019 Percona7
Architecture
mongos

8. © 2019 Percona8
Sharded Cluster
▪ Shard Key
▪ Chunks
▪ Balancer - Chunk distribution

9. © 2019 Percona9
POINTS TO NOTE
TARGET vs BROADCAST

10. © 2019 Percona10
Primary Shard
A
A

11. © 2019 Percona11
Primary Shard
sh.status()

12. © 2019 Percona12
Primary Shard
▪ Routing - sharded vs unsharded
▪ Keep at right shard
db.adminCommand( { movePrimary:
<databaseName>, to: <newPrimaryShard> } )

13. © 2019 Percona13
Ranged Sharding

14. © 2019 Percona14
Strategy
▪ Ranged Sharding

15. © 2019 Percona15
Strategy
▪ Ranged Sharding
sh.shardCollection( "database.collection", { <shard
key> } )
Example:
sh.shardCollection( "vinodh.testData", { empNo: 1 } )

16. © 2019 Percona16
Monotonically Changing Shard Key

17. © 2019 Percona17
Ranged Sharding
▪ Contiguous ranges determined by Shard Key
▪ Default method
▪ Efficient when
• High cardinality
• Low Shard Key frequency
• Non-Monotonically Changing Shard key

18. © 2019 Percona18
Hashed Sharding

19. © 2019 Percona19
Strategy
▪ Hashed Sharding

20. © 2019 Percona20
Strategy
▪ Hashed Sharding uses hashed index
sh.shardCollection( "database.collection", {
<field> : “hashed” } )
Example:
sh.shardCollection( "vinodh.testData",
{ UUIDfield: “hashed” } )

21. © 2019 Percona21
Monotonically Changing Shard Key - Hash

22. © 2019 Percona22
Hashed Sharding
▪ Provides equal distribution
▪ Target vs Broadcast operations
▪ Ideal for fields that changes monotonically like
ObjectID, timestamp etc

23. © 2019 Percona23
Zones

24. © 2019 Percona24
Why Zones?
▪ Isolate data set
▪ Geographically closest
▪ Route data to desired Shard h/w
▪ Distribute Writes based on DC

25. © 2019 Percona25
How to...
▪ First create tagRange with Shards
sh.addShardTag("shard01", "tag1")
sh.addShardTag("shard02", "tag2")
▪ Assign tagRanges to collections
sh.addTagRange( "<database>.<collection>",
{ "gender" : "Male", "userid" : MinKey },
{ "gender" : "Male", "userid" : MaxKey },
"tag1")

26. © 2019 Percona26
Zone

27. © 2019 Percona27
Zone

28. © 2019 Percona28
ReplicaSet - Key Points

29. © 2019 Percona29
Replicaset

30. © 2019 Percona30
Replicaset

31. © 2019 Percona31
Replicaset - ARBITER

32. © 2019 Percona32
Replicaset - Election+Priority
ELECTION - VOTING & CHOOSING
Priority: 5Priority: 1
Priority: 1 Priority: 5

33. © 2019 Percona33
Points to Note
▪ Set proper {Priority:n} to elect a member as
Primary
• Avoid setting Priority for all members
▪ Set {writeConcern:majority} to avoid data loss
▪ Set readPreference for reads

34. © 2019 Percona34
Topology- Application Servers

35. © 2019 Percona35
Applications and mongos in one server

36. © 2019 Percona36
mongos/router in each Application servers

37. © 2019 Percona37
Sharded Cluster in Private network

38. © 2019 Percona38
Topology- Shards

39. © 2019 Percona39
Shard instances deployed in dedicated servers design

40. © 2019 Percona40
Multiple Shard members in each Server + HA design

41. © 2019 Percona41
Production DC and DR DC + HA design

42. © 2019 Percona42
Using Zones / Tags + HA design

43. © 2019 Percona43
Points to Note

44. © 2019 Percona44
POINTS TO NOTE
▪ SHARD KEY - Pain Point!
• Monotonically increased key
• Do your tests!
▪ SHARD EARLY!
▪ ZONES

45. © 2019 Percona45
POINTS TO NOTE
BACKUP + RESTORE
https://www.percona.com/blog/2018/12/13/mong
odb-backup-how-and-when-to-use-psmdb-hotbac
kup-and-mongodb_consistent_backup/

46. © 2019 Percona46
Question?
vinodh.krishnaswamy@percona.com
https://in.linkedin.com/in/vinodhkrish

47. © 2019 Percona47
THANK YOU