The saying goes that there are only two hard things in Computer Science: cache invalidation, and naming things. Well, turns out the first one is solved actually ;) Join us for this session to learn how to keep read views of your data in distributed caches close to your users, always kept in sync with your primary data stores change data capture. You will learn how to - Implement a low-latency data pipeline for cache updates based on Debezium, Apache Kafka, and Infinispan - Create denormalized views of your data using Kafka Streams and make them accessible via plain key look-ups from a cache cluster close by - Propagate updates between cache clusters using cross-site replication We'll also touch on some advanced concepts, such as detecting and rejecting writes to the system of record which are derived from outdated cached state, and show in a demo how all the pieces come together, of course connected via Apache Kafka.

1. Image © Nathalie https://flic.kr/p/21Ghf2g (CC BY 2.0)
Keep Your Cache Always Fresh With Debezium!
Gunnar Morling
Software Engineer, Red Hat
@gunnarmorling

2. #Debezium @gunnarmorling
… Multi-site application with shared system-of-record database
… With local, denormalized read views (CQRS)
... Automatically kept in sync after writes
Today’s Mission
🤔
Explore How to Build a…

3. #Debezium @gunnarmorling
Agenda
Demo!
Learn Learn

4. #Debezium @gunnarmorling
● Open source software engineer at Red Hat
○ Debezium
○ Quarkus
● Spec Lead for Bean Validation 2.0
● kcctl, ModiTect, MapStruct
● Java Champion
● @gunnarmorling
Gunnar Morling

5. #Debezium @gunnarmorling
The Challenge
■ 90% read requests
■ Complex queries
Multi-site Application With Shared Database

6. #Debezium @gunnarmorling
The Idea
Caching to the Rescue!

7. #Debezium @gunnarmorling
The Idea
Caching to the Rescue!

8. https://flic.kr/p/PFDvkY Public Domain, Angelo Brathot

9. #Debezium @gunnarmorling
Infinispan
100% Open-source In-Memory Distributed Data Store
Interoperability
Resilient
Fault Tolerant Data
Clustered Processing Query
ACID Tx

10. #Debezium @gunnarmorling
Infinispan Deployment
Local Cache
App
Data
5, Peter

11. #Debezium @gunnarmorling
App 1
Data
App 2
Data
1, Maria
2, Jenny
5, Peter
5, Peter
App 3
Data
Put
4, Mike
Remove
5 Peter
Get
2, Null
Infinispan Deployment
Local Cache

12. #Debezium @gunnarmorling
App 1
Data
App 2
Data
1, Maria
2, Jenny
1, Maria
2, Jenny
App 3
Data
1, Maria
2, Jenny
Infinispan Deployment
Replicated Cache

13. #Debezium @gunnarmorling
App 1
Data
App 2
Data
1, Maria
2, Jenny
1, Maria
2, Jenny
App 3
Data
1, Maria
2, Jenny
Put
3, Juan
3, Juan
Infinispan Deployment
Replicated Cache

14. #Debezium @gunnarmorling
App 1
Data
App 2
Data
1, Maria
2, Jenny
3, Juan
1, Maria
2, Jenny
3, Juan
App 3
Data
1, Maria
2, Jenny
3, Juan
Infinispan Deployment
Replicated Cache

15. #Debezium @gunnarmorling
App 1
Data
App 2
Data
1, Maria 2, Jenny
App 3
Data
3, Juan
Infinispan Deployment
Distributed Cache (One Owner)

16. #Debezium @gunnarmorling
App 1
Data
App 2
Data
1, Maria 2, Jenny
App 3
Data
3, Juan
Get 2
Jenny
Get 2
Jenny
Infinispan Deployment
Distributed Cache (One Owner)

17. #Debezium @gunnarmorling
App 1
Data
App 2
Data
1, Maria 2, Jenny
App 3
Data
3, Juan
Infinispan Deployment
Distributed Cache (One Owner)

18. #Debezium @gunnarmorling
App 1
Data
App 2
Data
1, Maria
2, Jenny
2, Jenny
3, Juan
App 3
Data
1, Maria
3, Juan
Infinispan Deployment
Distributed Cache (Two Owners)

19. #Debezium @gunnarmorling
App 1
Data
App 2
Data
1, Maria
2, Jenny
2, Jenny
3, Juan
App 3
Data
1, Maria
3, Juan
Put 4 Will Put 4 Will
Infinispan Deployment
Distributed Cache (Two Owners)

20. #Debezium @gunnarmorling
App 1
Data
App 2
Data
1, Maria
2, Jenny
4, Will
2, Jenny
3, Juan
4, Will
App 3
Data
1, Maria
3, Juan
Infinispan Deployment
Distributed Cache (Two Owners)

21. #Debezium @gunnarmorling

22. #Debezium @gunnarmorling
Microservice 1
Microservice 2
Microservice 3
Stateless App 1
Data

23. #Debezium @gunnarmorling
Infinispan
Client/Server
Service 1
Service 2
Binary
(hot rod)
REST
...
Service 3
Data
Infinispan Cluster
Data
Data

24. #Debezium @gunnarmorling
Infinispan Cross-Site Replication
AWS (LON)
GCP (NYC)
Load Balancer
APP
APP
Service
APP
APP
Service
Shared
State
Shared
State
Shared
State
Shared
State
Data
Data
Data NYC
Data LON
RELAY2

25. #Debezium @gunnarmorling
The Question
How To Keep The Cache In Sync?

26. https://flic.kr/p/PFDvkY Public Domain, Angelo Br

27. #Debezium @gunnarmorling
Debezium in a Nutshell
Open-Source Change Data Capture
● A CDC Platform
○ Based on transaction logs
○ Snapshotting, filtering, etc.
○ Outbox support
○ Web-based UI
● Fully open-source, very active
community
● Large production deployments

28. #Debezium @gunnarmorling
Query-based Log-based
All data changes are
captured -
No polling delay or
overhead -
Transparent to writing
applications and models -
Can capture deletes and
old record state -
Simple
Installation/Configuration -
Debezium
Log-based vs. Query-based CDC

29. #Debezium @gunnarmorling
Solution Overview
Capturing Changes From the Database

30. #Debezium @gunnarmorling
● Stable
○ MySQL
○ Postgres
○ SQL Server
○ MongoDB
○ Db2
○ Oracle
● Incubating: Vitess, Cassandra
● Community: ScyllaDB, Yugabyte
Debezium
Supported Databases

31. #Debezium @gunnarmorling
Debezium: Connectors
Becoming the De-Facto CDC Standard
https://debezium.io/blog/2021/09/22/deep-dive-into-a-debezium-community-connector-scylla-cdc-source-connector/

32. #Debezium @gunnarmorling
Change Data Capture
Liberation for Your Data

33. #Debezium @gunnarmorling
● Can’t update filter list
● Long-running snapshots can’t be paused/resumed
● Can’t stream changes until snapshot completed
● Can’t re-snapshot selected tables
��
Detour: What’s New in Debezium?
Incremental Snapshotting

34. #Debezium @gunnarmorling
Incremental Snapshotting
● “DBLog: A Watermark Based
Change-Data-Capture
Framework”, by Andreas Andreakis
and Ioannis Papapanagiotou
● Key idea: interleave snapshot events
and events from TX log
https://arxiv.org/pdf/2010.12597v1.pdf
Detour: What’s New in Debezium?

35. #Debezium @gunnarmorling
Incremental Snapshotting
Detour: What’s New in Debezium?

36. #Debezium @gunnarmorling
Support for pg_logical_emit_message()
Detour: What’s New in Debezium?
● Directly writing arbitrary messages to the WAL
● No need for an outbox table

37. #Debezium @gunnarmorling
Multi-DB Support
Detour: What’s New in Debezium?

38. https://flic.kr/p/PFDvkY Public Domain, Angelo Brathot
Demo

40. #Debezium @gunnarmorling
● Fast start-up, low memory consumption
● Developer joy
● Imperative and Reactive
● Best-of-breed libraries
● Run via HotSpot and GraalVM native binaries
Quarkus - Supersonic Subatomic Java
A Stack for Building Cloud-native Apps

41. https://flic.kr/p/PFDvkY Public Domain, Angelo Brathot
Demo

42. #Debezium @gunnarmorling
… Multi-site application with shared system-of-record database ✅
… With local, denormalized read views (CQRS) ✅
... Automatically kept in sync after writes ✅
Today’s Mission
🤩
Explore How to Build a…

43. #Debezium @gunnarmorling
● Partial Updates, Multimap support
● Debezium embedded into Infinispan
● Kafka Connect sink connector for Infinispan
○ https://github.com/infinispan/infinispan-kafka/
● CDC connector for Infinispan?
Outlook

44. #Debezium @gunnarmorling
● Infinispan: @infinispan | https://infinispan.org/
● Debezium: @debezium | https://debezium.io/
● Demo: https://github.com/debezium/debezium-examples/ →
distributed-caching
● kcctl 🧸: https://github.com/kcctl/kcctl/
Learn More

45. #Debezium @gunnarmorling
Q & A
gunnar@hibernate.org
@gunnarmorling
📧
Thank You!