Slides of a talk given on 18 September 2014 at Strange Loop, St Louis, MO.
Databases are global, shared, mutable state. That’s the way it has been since the 1960s, and no amount of NoSQL has changed that. However, most self-respecting developers have got rid of mutable global variables in their code long ago. So why do we tolerate databases as they are?
A more promising model, used in some systems, is to think of a database as an always-growing collection of immutable facts. You can query it at some point in time — but that’s still old, imperative style thinking. A more fruitful approach is to take the streams of facts as they come in, and functionally process them in real-time.
This talk introduces Apache Samza, a distributed stream processing framework developed at LinkedIn. At first it looks like yet another tool for computing real-time analytics, but it’s more than that. Really it’s a surreptitious attempt to take the database architecture we know, and turn it inside out.
At its core is a distributed, durable commit log, implemented by Apache Kafka. Layered on top are simple but powerful tools for joining streams and managing large amounts of data reliably.
What we have to gain from turning the database inside out? Simpler code, better scalability, better robustness, lower latency, and more flexibility for doing interesting things with data. After this talk, you’ll see the architecture of your own applications in a completely new light.
References / further reading
• Martin Kleppmann: “Rethinking caching in web apps.” 1 October 2012. http://
• Martin Kleppmann: “Designing data-intensive applications.” O’Reilly, to appear in 2015. http://
• Jay Kreps: “The Log: What every software engineer should know about real-time data's unifying
abstraction.” 16 December 2013. http://engineering.linkedin.com/distributed-systems/log-what-
• Jay Kreps: “Questioning the Lambda Architecture.” 2 July 2014. http://radar.oreilly.com/2014/07/
• Jay Kreps: “Why local state is a fundamental primitive in stream processing.” 31 July 2014. http://
• Nathan Marz and James Warren: “Big Data: Principles and best practices of scalable realtime data
systems.” Manning MEAP, to appear January 2015. http://manning.com/marz/
• Apache Samza documentation. http://samza.incubator.apache.org/
• Alexandros Labrinidis, Qiong Luo, Jie Xu, and Wenwei Xue: “Caching and Materialization for Web
Databases,” Foundations and Trends in Databases, volume 2, number 3, pages 169–266, March 2010.
• Stefano Ceri, Georg Gottlob, and Letizia Tanca: “What You Always Wanted to Know About Datalog
(And Never Dared to Ask),” IEEE Transactions on Knowledge and Data Engineering, volume 1, number
1, pages 146–166, March 1989.