Handle fork (1/3+ byzantine failure) gracefully

[Latrasis]

Hello, i was wondering if tendermint has an option to store orphaned blocks or if it utilizes uncle blocks similar to Ethereum?

[ebuchman]

Nope! There is no such thing as an orphaned block in tendermint. Once a block is committed, it is final! An orphan implies two or more competing chains and that is simply not possible unless a third or more validators are byzantine

[Latrasis]

So from my understanding, if more than 1/3 are byzantine - what happens? Do the other nodes delete their data? Is there any way to track or log that a conflict occured before they delete it?

[ebuchman]

good question. we haven't defined this behaviour yet, but we are working on what this should look like. the software will panic before anything is overwritten, but it will keep a log of having received eg conflicting proposals, so that someone can come in and take a look. really we need to boot into a "recovery mode" protocol so validators can publish evidence, find out who shit the bed, kick them out and restart, but this is very much work to do. want to help?!

[jackzampolin]

Closing this as we prefer safety over liveness. Chain will halt in this scenario. Please reopen if I'm wrong.

[ebuchman]

In the event of +1/3 but -2/3 attacking the network, we should do something intelligent, ie. a "fork accountability" protocol, which Zarko and others are working on - see https://github.com/tendermint/tendermint/issues/1466. Maybe we keep this open until it's implemented.

[jackzampolin]

Sounds good! Thank you for the info @ebuchman

[melekes]

Closing in favor of #4189