[Feature]: time based upgrades

[tac0turtle]

Summary

Upgrades are currently only done via block height, but this is a hard thing to estimate and many times users see the time being off by a couple hours. In the past we did time based upgrades but ran into issues, in the past we didnt have capacity to dive into the issue.

Problem Definition

Height based upgrades can be mislead expected times

Proposal

add time based upgrades for users

[alexanderbez]

I believe this was due to wall clock skew and the fact that proposers could tweak time. I do recall @ethanfrey having good context on this issue.

Perhaps PBTS might alleviate concerns to an extent.

[ValarDragon]

Something we've wanted to do in Osmosis is allow upgrades to specify an approximate time target. Then the first block 24 hours before upgrade, we "Lock in" the upgrade block height using a trailing X avg block height.

Granted this may not be needed if theres no spooky edge cases around time, or we accept the 'couple second delay' (which I think should be fine)

[ethanfrey]

I believe this was due to wall clock skew and the fact that proposers could tweak time. I do recall @ethanfrey having good context on this issue.

Perhaps PBTS might alleviate concerns to an extent.

In "theory" it should work and be safe, via PBFT time. I believe we tried that on an early prototype when I was with Regen. However, there were a few failed upgrades (I think even app-hash-mismatch halts) when people tried with time. AFAIK, no one found the real cause, but removed this path as it was buggy.

It would be good to ask the regen team about this and if they had found a real issue, or couldn't track down the cause of the bug and removed it instead. AFAIK, it sometimes worked with time-based upgrade. Those are the most annoying bugs... ones that "sometimes" work.

[aaronc]

We never tracked down the cause unfortunately and removed the functionality.