The round was usable to build the current clock in an accumulated
fashion, relative to the previous round. The end time is the absolute
metric of it, which can be used to calculate the round number (with all
previous end times).
Substrate now builds off the best block, not genesis, using the end time
included in the justification to start its machine in a synchronized
state.
Knowing the end time of a round, or the round in which block was
committed to, is necessary for nodes to sync up with Tendermint.
Encoding it in the commit ensures it's long lasting and makes it readily
available, without the load of an entire transaction.
The machine reset to the end time of the current round. For a delayed
network connection, a machine may move ahead in rounds and only later
realize a prior round succeeded. Despite acknowledging that round's
success, it would maintain its delay when moving to the next block,
bricking it.
Done by tracking the end time for each round as they occur.
Unfortunately, this immediately makes Tendermint machine capable of
deployment as crate since it uses a git reference. In the future, a
Cargo.toml patch section for serai/substrate should be investigated.
This is being done regardless as it's the quickest way forward and this
is for Serai.
1) Commit didn't include the round, leaving the clock in question.
2) Machines started with a local time, instead of a proper start time.
3) Machines immediately started the next block instead of waiting for
the block time.
For a hash, which is fixed-size, these should be the same yet this helps
move past the dependency on SCALE. It also, for any type where the two
values are different, smooths integration.
Ideally, this would be generic. Unfortunately, the generic API serde
doesn't natively support borsh, nor SCALE, and while there is a serde
SCALE crate, it's old. While it may be complete, it's not worth working
with.
While we could still grab bincode, and a variety of other formats, it
wasn't worth it to go custom and for Serai, we'll be using SCALE almost
everywhere anyways.
