The Hardfork combinator is a remarkable piece of technology, which plays a central role in the deployment of Cardano Shelley, created to allow us to transition from Byron to Shelley in an orderly manner. Here’s a tech demo showing it being tested so you can see the process for yourself.
So despite the name, it’s purpose is to avoid an actual hard fork, as you might know them from other blockchain systems. In those cases, disagreement between the different entities running nodes on the network can lead to the system diverging, and creating different versions of the protocol that evolve separately and independently of one another. Perhaps we could have called it the ‘hard fork preventer’, but hindsight is a beautiful thing…
The hard fork combinator gives us the capability for a node to speak multiple protocols (though only one at once!). While running the first protocol (i.e. Byron), it can be triggered by a special on-chain update whereupon it manages the smooth transition to running the next protocol (i.e. Shelley).
This code has now been successfully tested against a number of mainnet candidates in ‘dry runs’ and as I type, we’re readying it for deployment on the Byron mainnet right now. In this video, Philipp Kant will walk you through the whole process, so you can see for yourself how everything works. For more background info on this ‘magical’ piece of engineering, check out our recent blog from Duncan Coutts and Edsko de Vries. Enjoy the video!