CAP Theorem Basics

Slides for Ruby Talks (workshops at PGS Software). Simple explaination of the CAP theorem,

Transcript

1. CAP THEOREM OR: YOU CANNOT HAVE EVERYTHING Maciej Rząsa
2. DISTRIBUTED SYSTEM A distributed system is a so ware system in which components located on networked computers communicate and coordinate their actions by passing messages.
3. REALLY? WHERE DO I USE IT? ssh/ p ssh/ p email web mobile apps
4. ASSUMPTIONS system that stores data asynchronous network
5. THREE FEATURES Consistency Availability Partition tolerance
6. A read sees all previously completed writes CONSISTENCY
7. Reads and writes always succeed. AVAILABILITY
8. Guaranteed properties are maintained even when network failures prevent some machines from communicating with others. PARTITION TOLERANCE
9. In a distributed system connected with an asynchronous network you can pick two. Why? Consider two clients attached to nodes without network connection. CAP: CHOOSE TWO
10. WHERE IS IT USEFUL? web forms: fetch data, wait and send it mobile apps: offline mode distributed databases: mongo, redis, elastic search what about the project you develop?
11. http://blog.nahurst.com/visual-guide-to-nosql-systems
12. ALLOWING PARTITIONS YOU MUST CHOOSE AVAILABILITY OR CONSISTENCY