feat: add minimum commission rate to x/staking

[youngjoon-lee]

Important

This PR is based on the v0.42-panacea branch which points to the v0.42.11 tag. Although the current panacea-core v2.0.2 uses cosmos-sdk v0.42.9, I thought it's okay to use cosmos-sdk v0.42.11 because there's no serious breaking changes. Also, if we decided to implement this feature based on v0.42.9, the branch strategy may become complicated.

Changes

• Added a new min_commission_rate genesis param of the x/staking module.
• Modified the logic CreateValidator and UpdateValidator to check if the desired commission rate is >= min_commission_rate.
• Added a special function for updating validator commissions without checking max_commission_change_rate.
  • Our chain upgrade strategy is updating the commission rate of all validators whose commission rate is smaller than min_commission_rate. In normal mode, this logic can cause an error: commission change rate cannot be more than the max rate. That's why we need a special function which doesn't ignore the max_commission_change_rate param.

Tips for reviewers

You don't need to review changes which are displayed as Some generated files are not rendered because those file are generated by make proto-gen. Unfortunately, Cosmos guys didn't execute make proto-gen after modifying proto files. That's why so many unexpected .pb.go files have been regenerated in this PR.

References

• osmosis-labs@c3f499c
• osmosis-labs@7dd164f
• osmosis-labs@07832f2
• My change is slightly different from Osmosis' change (especially MustUpdateValidatorCommission()). I've considered more corner cases when upgrading the chain with updating commission rates.

What's next?

Please jump to medibloc/panacea-core#291.

[youngjoon-lee]

I specified the version explicitly because the buf > 0.56.0 has so many CLI breaking changes. It's safe to use 0.56.0 since this Makefile was written when the latest version of buf was 0.56.0.

[gyuguen]

LGTM 👍

[gyuguen]

Ah, I have one question.
It seems that this min commission is not supported by cosmos-sdk.
Should this change be applied later when upgrading the cosmos-sdk version?

[youngjoon-lee]

@gyuguen

It seems that this min commission is not supported by cosmos-sdk.

Yeah. That's why I forked cosmos/cosmos-sdk as medibloc/cosmos-sdk.

Should this change be applied later when upgrading the cosmos-sdk version?

After merging this PR, we will release the v0.42.11-panacea tag from this medibloc/cosmos-sdk repository. Then, we will change the cosmos-sdk dependency of panacea-core from cosmos/cosmos-sdk v0.42.9 to medibloc/cosmos-sdk v0.42.11-panacea. That have been already done in the PR medibloc/panacea-core#291.
If you're worried about the data market protocol that is being developed in the master branch of panacea-core, it would be all good if we use medibloc/cosmos-sdk v0.42.11-panacea in the master branch as well.
In fact, we have to use the medibloc/cosmos-sdk instead of cosmos/cosmos-sdk forever as Osmosis does.

[youngjoon-lee]

I merged this PR even though I got only one approval, in order to submit the software upgrade gov proposal soon.
But, please revisit this PR if you have any question or suggestion.

[youngjoon-lee]

As Osmosis does in their osmosis-labs/cosmos-sdk forked repo, it would be okay to not update the CHANGELOG.md because of potential merge-conflicts with the upstream repo. Instead, I will write the release note in detail at GitHub Release pages.