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![• Multiple machines for better scalability
Node 1 Node 2
[Read] Scale
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Uploaded bySveta Smirnova
How Safe is Asynchronous Master-Master Setup?
The document discusses the safety and setup of asynchronous active-active configurations in MySQL, outlining potential issues that can arise with two active nodes, such as duplicate key errors and synchronization penalties. It emphasizes the importance of writing to one server at a time to avoid conflicts and suggests methods for structuring databases and tables to maintain system integrity. Additionally, techniques for achieving geographical distribution and optimal performance in active-active setups are highlighted.
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How Safe is Asynchronous Master-Master Setup?
- 1. How Safe isAsynchronous Active-Active Setup in MySQL September 10, 2020 Sveta Smirnova
- 2. • MySQL Supportengineer • Author of • MySQL Troubleshooting • JSON UDF functions • FILTER clause for MySQL • Speaker • Percona Live, OOW, Fosdem, DevConf, HighLoad... Sveta Smirnova 2
- 3. •What Happens with2 Active Nodes? •Why to Write to Multiple Nodes? •Galera, PXC, InnoDB Cluster •How to Setup Safe Active-Active Table of Contents 3
- 4. Source Replica ← Initiates AsynchronousBuilt-In Replication 4
- 5. Source Replica ← Initiates ←Requests a packet Asynchronous Built-In Replication 4
- 6. Source Sends the packet→ Replica ← Initiates ← Requests a packet Asynchronous Built-In Replication 4
- 7. Source Sends the packet→ Replica ← Initiates ← Requests a packet ... ? Asynchronous Built-In Replication 4
- 8. Node1 Initiates → Node2 ← Initiates AsynchronousTwo Active Nodes 5
- 9. Node1 Initiates → Requests apacket → Node2 ← Initiates ← Requests a packet Asynchronous Two Active Nodes 5
- 10. Node1 Initiates → Requests apacket → Sends the packet → Node2 ← Initiates ← Requests a packet ← Sends the packet Asynchronous Two Active Nodes 5
- 11. Node1 Initiates → Requests apacket → Sends the packet → ... ? Node2 ← Initiates ← Requests a packet ← Sends the packet ... ? Asynchronous Two Active Nodes 5
- 12. What Happens with2 Active Nodes?
- 13. Node1 INSERT SET id=42 Node2 INSERTSET id=42 INSERT 7
- 14. Node1 INSERT SET id=42 Sendsthe update → Node2 INSERT SET id=42 ← Sends the update INSERT 7
- 15. Node1 INSERT SET id=42 Sendsthe update → Receives update → Node2 INSERT SET id=42 ← Sends the update ← Receives the update INSERT 7
- 16. Node1 INSERT SET id=42 Sendsthe update → Receives update → Duplicate key error! Node2 INSERT SET id=42 ← Sends the update ← Receives the update Duplicate key error! INSERT 7
- 17. Node1 DELETE WHERE id=42 Node2 DELETEWHERE id=42 DELETE 8
- 18. Node1 DELETE WHERE id=42 Sendsthe update → Node2 DELETE WHERE id=42 ← Sends the update DELETE 8
- 19. Node1 DELETE WHERE id=42 Sendsthe update → Receives update → Node2 DELETE WHERE id=42 ← Sends the update ← Receives the update DELETE 8
- 20. Node1 DELETE WHERE id=42 Sendsthe update → Receives update → Key not found error! Node2 DELETE WHERE id=42 ← Sends the update ← Receives the update Key not found error! DELETE 8
- 21. Node1 UPDATE SET i=42 Node2 UPDATESET i=25 UPDATE 9
- 22. Node1 UPDATE SET i=42 Sendsthe update → Node2 UPDATE SET i=25 ← Sends the update UPDATE 9
- 23. Node1 UPDATE SET i=42 Sendsthe update → Receives update → Node2 UPDATE SET i=25 ← Sends the update ← Receives the update UPDATE 9
- 24. Node1 UPDATE SET i=42 Sendsthe update → Receives update → i=25 Node2 UPDATE SET i=25 ← Sends the update ← Receives the update i=42 UPDATE 9
- 25. Why to Writeto Multiple Nodes?
- 26. • Each nodefor its own purpose Application 1 Application 2 Data Distribution 11
- 27. • Multiple machinesfor better scalability Node 1 Node 2 [Read] Scale 12
- 28. • Nodes indifferent geographical regions Belgium Brazil GEO Distribution 13
- 29. • Waits whenthe active node dies • Then accepts writes Active Hot Standby Hot Standby 14
- 30. Galera, PXC, InnoDBCluster
- 31.
- 32. Node1 UPDATE ... Sends thepacket → Node2,3,... Fully Synchronous Cluster 16
- 33. Node1 UPDATE ... Sends thepacket → Waits Node2,3,... ← Receives the packet Fully Synchronous Cluster 16
- 34. Node1 UPDATE ... Sends thepacket → Waits Waits Node2,3,... ← Receives the packet Applies changes Fully Synchronous Cluster 16
- 35. Node1 UPDATE ... Sends thepacket → Waits Waits Waits Node2,3,... ← Receives the packet Applies changes ← Confirms Fully Synchronous Cluster 16
- 36. Node1 UPDATE ... Sends thepacket → Waits Waits Waits Receives answer → Node2,3,... ← Receives the packet Applies changes ← Confirms Fully Synchronous Cluster 16
- 37. Node1 UPDATE ... Sends thepacket → Waits Waits Waits Receives answer → Ready for new update Node2,3,... ← Receives the packet Applies changes ← Confirms Fully Synchronous Cluster 16
- 38. • Speed ofthe slowest member Synchronization Penalty 17
- 39. • Speed ofthe slowest member • Writes or reads should wait Synchronization Penalty 17
- 40. • Speed ofthe slowest member • Writes or reads should wait • Tunable Synchronization Penalty 17
- 41. • Speed ofthe slowest member • Writes or reads should wait • Tunable • Galera • wsrep sync wait • InnoDB Cluster • group replication consistency Synchronization Penalty 17
- 42. • Synchronization takestoo much time • Nodes often disconnect GEO Replication is Painful 18
- 43. How to SetupSafe Active-Active
- 44. • Business logic •Servers • Databases • Tables • Rows Divide and Rule 20
- 45. • Write onlyto one server at a time Node 1 (Active) Node 2 (Hot Standby) Servers 21
- 46. • Write onlyto one server at a time • Switch when needed Node 1 (Dead) Node 2 (Active) Servers 21
- 47. • Write onlyto one server at a time • Switch when needed Node 1 (Hot Standby) Node 2 (Active) Servers 21
- 48. • Each serverwrites to its own set of tables Node 1 Node 2 D1 D2 D3 D4 D1 D2 D3 D4 Databases and Tables 22
- 49. • Agreement onwhich rows Node 1 Node 2 Row 1 Row 2 Row 3 Row 4 Row 1 Row 2 Row 3 Row 4 Rows 23
- 50. • Agreement onwhich rows • E.g. AUTO INCREMENT • auto increment increment=NUMBER OF SERVERS • auto increment offset = server id • Custom index • Create your own unique pattern for each node Rows 23
- 51. • Hot Standby •Easy to setup and maintain • Separating writes by database/table • Comparatively easy to setup and maintain • Separating writes by row • Should be used very carefully Conclusion 24
- 52. MySQL User ReferenceManual Why MySQL Replication Fails, and How... MySQL High Availability More information 25
- 53.