1. 2014 Building Resilience within Mobile Commerce Apps Sonali Kamat Oct 10,2014 #GHC14 2014

2. Mobile : Desktop ratio in the US

3. 2014 Mobile : Desktop ratio in India

4. 2014 Rapid growth in online shopping in India

5. 2014 Network in India  Wifi traffic is 20%. The remaining 80% spread equally across 2G and 3G.  2G continues to grow even in urban areas. 3G subscribers encounter a lot of 2G coverage.  Network speeds across providers and locations 2G ranges from 21 to 97 Kpbs 3G from 400 to 2310 Kbps  High jitter experienced on Mobile Networks.  Local PaaS deployments of global providers not there (yet). Takeaway: Large standard deviation in latencies as a function of the network. Global cloud providers are not local enough.

6. 2014 Availability Client App NetworkServer Keep a user-centric view of availability

7. 2014 Being resilient means ….  Higher tolerance to instability in a rapidly changing environment In spite of −Network variances −Server side intermittent failures −Fast pace of feature changes / events

8. 2014 Techniques  Resilience to network instability −Building for intermittent connectivity −Reducing data footprint  Resilience to rapid feature build out / events −Pacing # of client releases  Resilience to serverside changes −Isolation of services −Fallback strategies −Caching – for predictable SLAs and avoiding spikes to corresponding services  Exploiting domain semantics

9. 2014 Techniques Resilience to network instability

10. 2014 Building for Intermittent Connectivity  Data model resident on client, but with dual origin.  Different characteristics of elements within model −Server originated – slow to volatile (e.g. prices) Fine-grained TTL Hierarchical cache – server has the final say. −Client originated Local commit – push in background. Transactional data – as “immediate” as possible. Some flows unavoidably real-time (payments) - so just propagate signal (not data).

11. 2014 Reducing data footprint  Wide screen size distribution. Top 5 screen sizes ~ 70%.  Index image resource or HTTP-Content-Negotiate using: −pixel sizes −Dpi −network “quality” ( ~ q: )  App fetches appropriate image from CDN

12. 2014 Techniques Flexibility towards rapid experiments

13. 2014 Resilience to experimentation / events  Native experiences adaptive to server-side controls −Layout of pages, styles, themes −Server driven, yet uses “native” mobile apis −Changes continually – in response to programs, and events.(e.g. weekend sale on furnishings)

14. 2014 Client – JSON

15. 2014 Client – “css” within json

16. 2014 Techniques Resilience to intermittent service failures

17. 2014 Resilience: a core architectural construct on serverside AND Logic implies uptime ~ 1 – (1-x)^N For a Mobile API stack depending on 30 services each that have 99.99% uptime = 2+ hours downtime/month. source: https://github.com/Netflix/Hystrix/wiki

18. 2014 Isolation of dependencies  Isolation of every single dependency  Fault tolerance techniques −separate threads for network bound dependencies with per-dependency thread pools −semaphores (non-blocking) −timeouts −circuit breakers Shed Load Reduce user request latency when failure is expected −fallbacks

19. 2014 Fallback Strategies  Service-provided fallback −In-place alternates offered by dependency service −Tightly integrated with original dependency service  Caller-provided fallback −Invoke fallback for partially completed scatter- gather as a function of response vector.

20. 2014 Caching Strategies

21. 2014 Caching – pro-active refreshes

22. 2014 Techniques Exploiting domain semantics

23. 2014 Desired service response time could be relaxed!  Example −re-seller fraud detection for physical products. −flash sale of Mi3 phone -> token issuance workflow.

24. 2014 Summary - Techniques  Resiliency to network instability −Building for intermittent connectivity −Reducing data footprint  Resilience to rapid feature build out / events −Pacing # of client releases  Resiliency to serverside changes −Isolation of services −Fallback strategies −Caching strategies  Exploiting domain semantics

25. 2014 References  http://gs.statcounter.com/#desktop+mobile+tablet-comparison-IN-monthly-201202-201402 http://gs.statcounter.com/#desktop+mobile+tablet-comparison-IN-monthly-201202-201402  http://techblog.netflix.com/2012/11/hystrix.html http://techblog.netflix.com/2012/11/hystrix.html  https://www.dartlang.org/docs/tutorials/futures/ https://www.dartlang.org/docs/tutorials/futures/  http://trai.gov.in/WriteReaddata/ConsultationPaper/Document/Consultation%20Paper%20on%20a mendment%20to%20wireless%20data%20regln%2021042014.pdf http://trai.gov.in/WriteReaddata/ConsultationPaper/Document/Consultation%20Paper%20on%20a mendment%20to%20wireless%20data%20regln%2021042014.pdf  http://www.thehindubusinessline.com/features/smartbuy/india-is-still-low-on-the-4g-curve- vodafone/article5797060.ece http://www.thehindubusinessline.com/features/smartbuy/india-is-still-low-on-the-4g-curve- vodafone/article5797060.ece  http://tech-blog.flipkart.net/ http://tech-blog.flipkart.net/

26. 2014 Got Feedback? Sonali.km8@gmail.com Rate and Review the session using the GHC Mobile App To download visit www.gracehopper.orgwww.gracehopper.org

27. 2014 Contact Me Sonali.km8@gmail.com (+91)-9980056436