CSC364 Lecture 13

Introduction to Networked, Distributed, and Parallel Computing
Pull vs Pull
(202602)

Transcript

1. Dr. Javier Gonzalez-Sanchez javiergs@calpoly.edu www.javiergs.info o ffi ce: 14 -227 CSC 364 Introduction to Networked, Distributed, and Parallel Computing Lecture 13. Push vs Pull Models 1
2. Distributed Computing • Multiple independent computers (often c a lled nodes) work together over a network to solve a problem th a t would be di ff icult, slow, or impossible for a single m a chine to h a ndle a lone. • T a sks a re divided into sm a ller pieces a nd distributed a cross di ff erent m a chines, which process them concurrently a nd coordin a te through mess a ge p a ssing or sh a red d a t a protocols. • Addresses ch a llenges such a s synchroniz a tion, f a ult toler a nce, consistency, communic a tion l a tency, a nd resource m a n a gement. • Distributed computing underlies m a ny modern technologies, including cloud computing pl a tforms, l a rge-sc a le web services, distributed d a t a b a ses, blockch a in networks, a nd p a r a llel scienti f ic simul a tions. 2
3. Push Model publish(job) Workers p a ssively receive. Ch a r a cteristics: • Simple • Low coordin a tion • No control over distribution • No n a tur a l b a ckpressure 3 jobObject 1 5 7 #0
4. Pull Model Workers Request Work publish("csc364/work/request", workerId) Outsourcers respond publish("csc364/work/ a ssign/{workerId}", job) Workers control f low. 4 jobObject 1 5 7 #0
5. Step 1 — Work Request Topic csc364/work/request { "workerId": "W1", "c a p a city": 1 } C a p a city could be: • number of free thre a ds • queue size rem a ining • simple “re a dy” 5
6. Step 2 — Outsourcer Maintains Job Queue Outsourcer: • Subscribes to request topic • M a int a ins intern a l queue • Assigns jobs only when requested 6
7. Step 3 — Direct Assignment Topic • Inste a d of: csc364/jobs • Use: csc364/work/ a ssign/{workerId} • Now job is sent only to th a t worker. 7
8. Problem • Wh a t if worker cr a shes a fter requesting but before completing job? • Outsourcer m a int a ins: Map<JobId, WorkerId> inFlight; • If no result within timeout → re a ssign. 8
9. Tools
10. 10 Test Yourselves https://www.hivemq.com/demos/ websocket-client/
11. https://www.hivemq.com/demos/websocket-client/ 11
12. MQTTX 12
13. Questions 13
14. Lab.
15. Distributed Scenario 15
16. CSC 364 Introduction to Introduction to Networked, Distributed, and Parallel Computing Javier Gonzalez-Sanchez, Ph.D. javiergs@calpoly.edu Winter 2026 Copyright. These slides can only be used as study material for the class CSC 364 at Cal Poly. They cannot be distributed or used for another purpose. 16