The document introduces sharding as a method of partitioning large databases into manageable parts called shards, supported by Vitess, an open-source database management system that enables horizontal scaling of MySQL databases. It highlights Vitess's architecture, including lightweight proxy servers, traffic routing, and metadata storage, while also mentioning its adoption by major platforms like YouTube, JD.com, and Slack. The document outlines steps for implementing sharding, including necessary prerequisites and various configurations through YAML files.

1. Sharding MySQL with Vitess
Harun Küçük

2. What is Sharding?
Sharding is a type of database partitioning that separates very large databases
into smaller,faster and more easily managed parts called data shards.

3. • Non-Scalable Master
Why we need Sharding?
Sample Traditional MySQL Replication
• Scalable App Layer
• Scalable Replicas

4. Vitess
• Started 2010 , youtube https://vitess.io/
• Open source since 2011 https://github.com/vitessio/vitess
• Incubating project in CNCF https://www.cncf.io/projects/

5. Vitess Architecture
• Lightweight proxy server
• Routes traffic to correct vttablet
• Returns consolidated results back to the clients

6. Vitess Architecture
• Proxy server that sits in front of MySQL instance
• Protect MySQL from harmful queries
• Connection Pooling
• Query rewriting
• Hot row protection

7. Vitess Architecture
• Stores metadata (running servers,sharding schema,Replication Graph)
• Etcd, Apache Zookeeper or consul could be used for topology

8. Vitess Architecture
• Vtctl is command line tool, Vtctld is an HTTP server that lets
you browse the information stored in the topology.

9. Vitess Architecture
• Replica tablets: candidates for master tablet ,
Readonly tables: for batch jobs, resharding,bigdata,backups etc.

10. Vitess Key Adaptors
• Started 2010 at Youtube and It has been serving all Youtube
database traffic since 2011. Youtube had 256 shards and each
shards had between 80 and 120 replicas across 20 datacenters
all around the world. (Approx. 256K instance)
• JD.com is the 2nd largest retailer company in China. JD.com has
more than 10.000 instance (master,replicas) in Vitess on
kubernetes cluster
• Square Cash App fully runs on Vitess. Square has more than 64
shards.
• Slack migrated 40% database traffic to Vitess and their goal is
100%
• Pinterest’s all of advertising campaign management fully runs
on Vitess

11. Example: Sakila DVD Rental Company Database
Lets suppose we have a DVD rental company and our database diagram live below

12. Day 1: Table Rows
Query:

13. 30 days later…
Query:

14. 6 months later…
Query:

15. 2 years later…
Query:

16. Entity Group for Sharding
Payment,Rental and Customer
tables have customer_id column.
So these three tables should be
sharded horizontally by
customer_id

17. Step 1: Vertical Sharding

18. Step 2: Horizontal Sharding

19. Step 3: Resharding

20. Prerequisites for Demo
• Vitess (https://github.com/vitessio/vitess)
• Kubernetes Cluster or Minicube
• Etcd operator for topology cluster
• Helm for vitess helm charts (vitess/helm/vitess)
• NFS client provisioner for persistent NFS volumes
(https://github.com/helm/charts/tree/master/stable/nfs-client-provisioner)

21. 1.) initiate new cluster, Concepts
File: initial_cluster.yaml
• Cell : Zone, availability zone, datacenter
• KeySpace : Logical Database
• Vschema : Vitess Schema, contains
metadata about how tables are organized
across keyspaces and shards
• Vindex : index to find shards

22. 1.) initiate new cluster
File: initial_cluster.yaml

23. 1.) initiate new cluster

24. 2.) Create New Keyspace
File:create_keyspace.yaml

25. 2.) Create New Keyspace
File:create_keyspace.yaml

26. 3.) Split Keyspace Schema
File:split_keyspace_schema.yaml

27. 3.) Split Keyspace Schema
File:split_keyspace_schema.yaml

28. 3.) Split KeySpace Schema

29. 4.) Vertical Split Clone
File:vertical_split_clone.yaml

30. 4.) Vertical Split Clone
File:vertical_split_clone.yaml

31. 4.) Vertical Split Clone

32. 4.) Migrate
File: migrate_readonly_replica.yaml
migrate_master.yaml

33. 4.) Migrate ReadOnly and Replica

34. 4.) Migrate Master

35. 5.) Drop Blacklisted Tables

36. VtGate Quey Routing

37. VtGate Quey Routing

38. Horizontal Sharding

39. 6.) Primary Vindex for Horizontal Sharding
File: create_vindex.yaml

40. Sharding by Hash Function

41. Sharding by Hash Function
1001
1000
1002
1003
1004
1005
1006
1007

42. Vitess Hash Algorithm (3des hash)
4000 = 4000000000000000
8000 = 8000000000000000

43. Vitess Hash Based Sharding (3des hash)
264 combination. theoretically allows us to have an infinite number
of shards

44. Vitess Hash Based Sharding (3des hash)

45. 7.) Create Horizontal Shards
File: create_horizontal_shards.yaml

46. 7.) Create Horizontal Shards

47. 7.) Horizontal SplitClone
File: horizontal_split_clone.yaml

48. 7.) Horizontal SplitClone
File: horizontal_split_clone.yaml

49. 7.) Horizontal SplitClone
File: horizontal_split_clone.yaml

50. 8.) Migrate RdOnly,Replica and Master
File: 13_migrate_readonly_replica.yaml
14_migrate_master.yaml

51. 8.) Migrate RdOnly,Replica and Master
File: 13_migrate_readonly_replica.yaml
14_migrate_master.yaml

52. Querying Vitess Cluster - Counts

53. Querying Vitess Cluster - Routing

54. Querying Vitess Cluster - Routing

55. Querying Vitess Cluster – @replica,@rdonly

56. Querying Vitess Cluster – Cross Shard Join

57. Querying Vitess Cluster – Cross Shard Join

58. Querying Vitess Cluster – Cross Shard Join
= +
N *
N = row count of 2. query’s result
1
2
3

59. VReplication
Files:copy_schema_shard.sh,vreplication.sh,ap
ply_routing_rules.sh,add_reference_table.sh

60. Querying Vitess Cluster –Cross Shard
Join,VReplication

61. Querying Vitess Cluster –Scatter Query

62. Querying Vitess Cluster –Scatter Query
LookupVindex

63. Drawbacks: Application Transactions
• Best Effort Commit -> Consistency Problems
• 2 Phase Commit -> Performance Cost

64. Drawbacks: Distributed Deadlocks
Shard Level Deadlock

65. Drawbacks: Distributed Deadlocks
Database Level Deadlock

66. Application Transactions

67. Q&A
github.com/vitessio/vitess
vitess.io
vitess.slack.com

68. Thank You