1. Distributed Counters
with Riak on EC2
Hackover 2012 - hackathon.ro
Andrei Savu - asavu@axemblr.com
Twitter: @andreisavu

2. Me
• Co-Founder of Axemblr.com
• Co-Organiser of Bucharest JUG (bjug.ro)
• OSS contributor (Apache Whirr, jclouds)
• Connect with me on LinkedIn

4. ... with Riak on AWS
(for fun and profit - real-time analytics)

5. Riak
• Distributed Database (Key-Value)
• Focused on: Availability, Fault-Tolerance,
Operation Simplicity, Scalability
• Each node is the same (no master)
• Erlang (OTP)

6. Consistent Hashing

7. Riak - More Features
• Consistent Hashing
• Replication (including cross DC)
• Automatic load-balancing
• Hinted Handoff
• Client-side conflict resolution

8. Riak Control

9. Amazon Cloud
• Infrastructure as a Service (IaaS) provider
• Services I use:
• EC2 (compute)
• ELB (load balancing)
• Route53 (smart dns)
• CloudWatch (monitoring)

10. Service API
• GET /counters/<id>
• POST /counters/<id> <value>

11. Eventual Consistency
• ... and counters
• Client side conflict resolution
• counter => {last: 0, step: 0}

12. Basic Algorithm
• {last: 1, step: 0}
• +2 => {last: 1+0, step: 2}
• Partition 1 • Partition 2
• +3 => {last: 1+2, step: 3} • +4 => {last: 1+2, step: 4}
• Fixed • Fixed
• 1+(2 + 3 + 4) = 6 • read: {last: 3, step: 3 + 4}

13. Architecture
US
API
ELB
Riak w/ cross DC
+
replication
Route53 UE
API

14. Demo Time
Local Machine and on Amazon EC2 (two regions)

15. Demo Resources
• riak-ec2-launcher
https://github.com/andreisavu/riak-ec2-
cluster-launcher
• riak-dt
https://github.com/basho/riak_dt

16. Resources #1
• PoC for Convergent Data Types
https://github.com/basho/riak_dt
• Study on Convergent Data Types
http://hal.inria.fr/docs/00/55/55/88/PDF/
techreport.pdf
• Gist: https://gist.github.com/882055

17. Resources #2
• statebox - state "monad" for automated
conflict resolution
https://github.com/mochi/statebox
• Convergent Replicated Data Types
https://github.com/aphyr/meangirls
• Strong Eventual Consistency and Conflict-free
Replicated Data Types
http://research.microsoft.com/apps/video/
default.aspx?id=153540

18. Resources #3
• Cassandra Counters
http://wiki.apache.org/cassandra/Counters
• Convergent Replicated Data Types - SRC
Fringe
https://speakerdeck.com/bryce/convergent-
replicated-data-types-src-fringe
• http://amattn.com/2012/09/07/
riaks_two_contentions_and_crdts.html

20. Thanks! Questions?
Andrei Savu - asavu@axemblr.com
Twitter: @andreisavu