1. Chase Holland Edward Norris CS387 3/18/2014 LOAD BALANCING

2. Controlling information flow amongst a set of computational resources Information Homogeneous: All tasks are identical Heterogeneous: Tasks are different Clusters Homogeneous: All resources are identical in architecture and performance Heterogeneous: Not all resources are identical

3. Algorithms for homogeneous clusters Round Robin Random Algorithms for heterogeneous clusters Load Sensitive Diffusion LEACH PP-GMCP

4. ROUND ROBIN – IDENTICAL TASKS Classical (Static) Round Robin Weighted Round Robin

5. ROUND ROBIN II – DIFFERENT TASKS Dynamic Round Robin Load sensitive Static heuristics Dynamic heuristics

6. LEACH

7. Low Energy Adaptive Clustering Heirarchy

8. PP-GMCP Probabilistic Preferred Gray Markov Chain Prediction Similar to Round Robin, but make predictions about incoming data trends DIFFUSION When there is a single, central master that distributes tasks, what if there are many small tasks coming in from many different locations? Master becomes I/O bound and a bottleneck

9. DIFFUSION

10. 6 THINGS YOU NEED IN YOUR LOAD BALANCER

11. INTO THE WILD!

12. ROUND ROBIN DNS Available from many DNS providers such as AWS’ Route 53 Very basic, round-robin scheduling

13. HAPROXY High Availability Proxy Open source: GNU GPL v2 Used by: Stack Overflow Reddit Tumblr Twitter AWS’ OpsWorks

14. HAPROXY Written in C Active development since 2000 Proxies TCP and HTTP-based applications Configurable algorithm via balance option Round Robin Static Round Robin Least Connections Source IP hash URI/URL hash

15. LINUX-HA Heartbeat: Message passing layer Pacemaker: Cluster manager Glue Local Resource Manager STONITH (kills off dead nodes) hb_report: advanced error reporting

16. NGINX Upstream Module Configurable algorithm: Round Robin Static Round Robin Least Connections Source IP hash URI/URL hash

17. HARDWARE & COMMERCIAL LOAD BALANCERS

18. AMAZON AWS’ ELB Elastic Load Balancer Very easy to configure Uses a health-check URL Automatically scales SSL offloading, sticky sessions Distributes across availability zones Excellent web management tools

19. AMAZON AWS’ ELB Insanely expensive Pricing $0.025/hour per instance to run + instance fees $0.008 per GB transferred (in or out)

20. CITRIX NETSCALER Most likely what AWS’ ELB is based on Also available as a virtual machine Endorsed by Cisco®

21. KEMP LOAD BALANCERS Offers a wide variety of hardware load balancers Several big-brand clients

22. QUESTIONS?