engineering real world problems - at toki alumni meeting

Software Engineering:

The Real WorldDerianto Kusuma

traveloka.com

Flight graph

Shortest path from MES to AMQ?

K shortest routes from MES to AMQ?GA 123 MES-CGK 14.40-16.20JT 124 CGK-UPG 19.00-22.15JT 125 UPG-AMQ 23.45-02.00

JT 50 MES-SUB 07.50-10.05JT 52 SUB-AMQ 16.30-19.30

? ≤ N ≤ ?? ≤ V ≤ ? ? ≤ E ≤ ? Time limit: ? sec

Max memory?Number of test cases?

80 airports, 1,000 daily flight100,000 queries / day, peak at 5-9 pm(10 queries / sec)20% CPU time 20 ms / query

Some routes change schedule by dayIn the long term, routes changePrice changes every ???Data sources for routes & prices?

Data source unreliable Route search must still be reliablePrice always changing reasonable accuracy

What is K shortest routes from A to B at date D, with reasonable price accuracy?

(Constraints: all above)

New problems

Lesson 1

- Functional - Real-time correctness- Architectural - Load / performance - Reliability - Scalability, etc.

1. Web scraping2. Route search

Web scraping10-20 airport pairs / query 5-15 sec / airport pair !!!

Multithreading10 query / sec x 20 scrape / query x 5 sec / scrape = 1000 concurrent threads!Run out of RAM

AsynchronouscallAsync(param1, param2, param3, Callback<T> callback)Backed by selector-based HttpClient

Cachingttl = ? on failure? on timeout?Fetching synchronization?

Route searchPruning?Caching at airport pair level?

New solutions

Lesson 2

User:“Just give me cheap tickets, b*tch”“And don’t make me wait too long”

Am I answering the right question?

“Wrong Question”

Cheap price- reasonable coverage- limited precomputed routes

Speed / “perception of speed”- Aggressive pruning- Polling- Prefetching- UI tricks

Source: hipmunk.com

What user really wants- Tomorrow is cheaper?- Don’t give me that X airlines!- I can’t wake up that early!

What user really wants- I’m actually looking for trains!

Business contexts matter

Lesson 3

Flight search component

Flight searchFlight search

Direct route search

Direct route search

Indirect route search

Indirect route search

ScrapingScrapingRoute

predictorRoute

predictor

Airlines websitesAirlines

websites

Per airline cache

Per airline cache

Per route cache

Per route cache

FeatureFeature FeatureFeature FeatureFeature

Other data sources

Other data sources

......

Route DB

Route DB

Component diagram

Flight searchFlight search

Backend common libBackend common lib

Frontend common libFrontend common lib

FrontendFrontend Control dashboard

Control dashboard

3rd party libraries3rd party libraries

User accountsUser accounts

Common dataCommon data

BackendBackend

FrontendFrontend

BackendBackend

FrontendFrontend

Scraping library

Scraping library

Deployment diagram

Frontend nodesFrontend nodes Backend nodesBackend nodesVIPVIP

Misc serviceMisc service

DBDBDistributed

cacheDistributed

cache

VIPVIPClientsClients

CDNCDN

System builder, not only coder

Lesson 4

Site operationsCode push? Maintenance mode?Configuration? Control? Monitoring?

Dev operationsSource control? Build system? Testing? Staging? Release process?

MaintainabilityCode quality? Loose coupling? Portability? Backward compatibility?

The real world needs to operate

Lesson 5

Software Engineering:

The real world

1. New problems

2. New solutions

3. Business context

4. System design

5. Operation

Thanks for listening!Q & A