This document discusses the architecture and features of reactive data access in Spring Data modules, focusing on how it differs from traditional synchronous data access methods. Various reactive drivers for databases like MongoDB, Redis, Apache Cassandra, and Couchbase are presented, along with their non-blocking characteristics and lifecycle management. Additionally, it touches on future developments and resources for further learning in the field of reactive programming.

1. Under the Hood of
Reactive Data Access
Mark Paluch
@mp911de
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2. Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons
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Spring Data Modules
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JPA

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Reactive Spring Data Modules
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JPA

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JDBC
Fully-blocking API
Non-blocking API announced (JDK-8188051)
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http://mail.openjdk.java.net/pipermail/jdbc-spec-discuss/ • JDK-8188051: http://hg.openjdk.java.net/jdk10/sandbox/jdk/rev/a31057bda7c5

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Relational Databases
Limited scalability
Resource synchronization
Transactions
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Query by time
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Transport

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Synchronous Data Access
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Data store
App
Data store
App
Data store

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Reactive Data Access
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Data store
App
Data store Data store Data store
App
🎉

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Differences to imperative Data Access
Drivers require threading infrastructure
Timeout handling different
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10. Reactive NoSql drivers

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Reactive drivers
End-to-end nonblocking
Asynchronous request-response processing
Non-blocking pooling
Non-blocking connect
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12. Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons
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Application Driver Application
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Request Server selection
Queueing
Write Response decoding
Response buffering
Request completion Response

13. Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons
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MongoDB
Reactive-over-async driver
Cursor lifecycle
Pluggable I/O
Pooled connections
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14. Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons
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Query by time
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Request
Response
(chunk)
Response
(complete)
Prefetch
(cont.d)
Query
Emit
elements
Result
processing

15. Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons
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MongoDB Driver Fetching
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OperatorMongoDB Subscriber
request(Long.MAX_VALUE)request(Long.MAX_VALUE)

16. Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons
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MongoDB Driver Fetching
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FilterMongoDB Subscriber
request(Long.MAX_VALUE)request(Long.MAX_VALUE)

17. Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons
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MongoDB Driver Fetching
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Operator
(filter)
MongoDB Subscriber
request(1)
Dropped element
request(Long.MAX_VALUE)

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Specific Features
Tailable Cursors (@Tailable)
MongoDB 3.6: Change Streams
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Cursor size derived from demand

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Redis
Reactive driver (Lettuce 5)
Based on Netty and Project Reactor
Singleton connection
Pooled connections
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Command by time
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Request
Command
Command
(subscription)
Response
(chunk)
Response
(complete)

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Specifics
Use ByteBuffer instead byte[]
@null handling: Emission of empty buffers
Suspend reading if no demand
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22. Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons
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Apache Cassandra
Reactive bridge over async driver
Netty-based driver (Datastax)
Pooled connections
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23. Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons
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Query by time
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Request
Response
(chunk)
Response
(complete)
Query
Emit
elements
Result processing
Next page

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Outlook
Cassandra driver 4.0 in the works
Likely support for reactive execution model
Emit items as they are received
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https://github.com/datastax/java-driver/tree/4.x • https://datastax-oss.atlassian.net/browse/JAVA-1505

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Couchbase
Reactive driver driver
Based on Netty and RxJava 1
Multiple connection schemes
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26. Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons
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Couchbase Fetching
Key-Value, DCP
1. Request
2. Response
3. Emit results
Search, Query, View
1. Request
2. Response streaming
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Command by time
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Request
Command
Command
(subscription)
Response
(chunk)
Response
(complete)

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Outlook
Couchbase driver likely to move to RxJava 2
• No tickets/decisions yet
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29. Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons
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Resources
Slides – mp911.de/s1p-hood-slides
Example Code – mp911.de/s1p-hood-code
Spring Data Examples – Repository @ Github
Find us on Gitter!
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30. Feedback welcome

31. Learn More. Stay Connected.
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#springone@s1p

32. Disclaimer

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