Pub/sub-based Web Applications

Walter WongHIIT & NomadicLab

01.03.2010

AgendaCurrent data delivery in the Web

Pub/sub-based content delivery

Implementation

Evaluation

Conclusion

Pull-based modelClient Server

HTTP Get

HTTP 200 OK

HTTP Get

HTTP 200 OK

+ Servers don’t save state- Clients constantly poll for data- Entire page download- No real time delivery capabilities

:

Push-basedHTTP long-polling

+ Clients request and wait+ Almost real-time delivery+ Servers send just the updated data (AJAX)- Servers keep open TCP connections- Clients request again after data delivery

Client Server

HTTP GetHTTP 200 OK

XHR Get (long poll)

HTTP 200 OKXHR Get (long poll)

update!

:

Pub/sub-based for Web content delivery

Objectives

Real-time data delivery capabilities in the Web

Lower network bandwidth consumption (simple delivery channel - no TCP)

Lower hardware requirements (no connection maintenance)

Lower energy consumption (portable devices)

Pub/sub ModelSubscriber Publisher

Subscribe(data)

Publish(data)+ Servers don’t save state+ Partial page download+ Real time delivery Capabilities+ Consumes less energy

Publish(data)

Publish(data)

Pub/sub-based for Web content delivery

PSIRP Firefox plug-in

Evaluation network

PSIRP Firefox plug-in vs. HTTP long-polling

ConclusionPull and push-based systems hinder real-time content delivery in the Web

Waste of resources mainly due to the host-centric client/server model

Publish/subscribe provides real-time content delivery with lower overhead

Implementation shows that pub/sub is simpler, requires lower hardware requirements and reduces the overall network traffic

Questions?

• Comments?

• Thanks!