Learn more about Russian war crimes in Ukraine.

FOSDEM: The Challenges and Secrets of the Realtime World


This is a simple, high-level introduction to “realtime”. Many apps have “realtime” aspects: Periscope, Gett (taxis), various IoT things, drones. How can we do realtime? Not by polling!! There are many “realtime protocols” - HTTP streaming, HTTP long polling, HTTP/2, Kafka, WebSocket, XMPP. The common element is TCP - they are all a layer on top of a TCP socket. HTTP long polling is very popular. In usual implementation, the client makes a request signalling interest in something, and the server only responds once an interesting thing happens. The client then immediately makes another request. To avoid dropping messages, the re-request should include a timestamp or sequence number. This also accounts for connectivity issues - especially on mobile, connections drop frequently, and ideally should be re-connected transparently. Most/all of these have a concept of “channels”, or “topics”, or “interests” - a thing which clients can “publish” and “subscribe” to. Scaling pub/sub (in PubNub’s case) means operating multiple servers, and connecting clients to their closest server using GeoDNS. You then need some way to communicate publishes between those servers.

What can computers do? What are the limits of mathematics? And just how busy can a busy beaver be? This year, I’m writing Busy Beavers, a unique interactive book on computability theory. You and I will take a practical and modern approach to answering these questions — or at least learning why some questions are unanswerable!

It’s only $19, and you can get 50% off if you find the discount code ... Not quite. Hackers use the console!

After months of secret toil, I and Andrew Carr released Everyday Data Science, a unique interactive online course! You’ll make the perfect glass of lemonade using Thompson sampling. You’ll lose weight with differential equations. And you might just qualify for the Olympics with a bit of statistics!

It’s $29, but you can get 50% off if you find the discount code ... Not quite. Hackers use the console!

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