Dealing with Unreliable Networks

Director, TwitterJess Garms

Dealing with Unreliable Networks

1.Reliability2.Resiliency3.Performance4.Empathy

Networks Around the World

Reliability

Tweet

What if that network call fails?

Solution: Retry

iOS:- (BOOL)shouldRetryRequestWithError:(NSError *)error{ if ([error.domain isEqualToString:NSURLErrorDomain]) { if (... code from NSURLError.h should be retried ...) { return YES; } } else if ([error.domain isEqualToString:NSPOSIXErrorDomain]) { if (... code from errno.h should be retried ...) { return YES; } } return NO;}

Android:

try { readResponse()} catch (IOException ioe) { markForRetry();}

Idempotency

Resiliency

Performance

Objectivevs

Perceived

Points of Presence (POPs)

HTTP/2 & SPDYHTTP/1.1

HTTP/2

WebP

Progressive JPEG

Low-res Images

Waiting for requests

Request Prioritization1. User actions2. Foreground API requests3. Images4. Background API requests5. Prefetching and Polling

Communicate Network

Status

Network Forecasting

Empathy

Measure!

Grey Box Times

Network Debugging

Network Simulation

1. Never rely on a network call succeeding quickly2. No silver bullet: many separate fixes

Conclusions

https://about.twitter.com/careers

Interested in working on these problems?