Multi-chain Tendermint

[tac0turtle]

Tendermint has been at the forefront of allowing developers to spawn their own chains. This comes with a downside, node operator have to run many sentry nodes, many validators consuming way more bandwidth and disk space than what is needed. The idea of running one instance of Tendermint for many chains has come up in the past, now with the introduction of IBC and cross-chain-validation a multi-chain Tendermint provides a simple way for validators to participate in multiple networks without the need to spawn new Tendermints.

There are multiple approaches this can be accomplished. The two that come to mind are:

1. A single tendermint instance running multiple app instances through ABCI. To start this could use a gossip network to get the needed signatures and later on use a more directed network.

2. Separate block formation & state execution from consensus. This allows validators to not need an instance of the application. This complicates the network topology but gives more freedom to validators signing blocks from various networks.

I am in favor of 2. The reason why I like 2 is that a validator should be concerned with coming to consensus on a block. Not what's in the block. This should be handed off to a secondary node type. This is similar the flow architecture design.