[cosmos-sdk](x/staking/delegation) limit voting power logic

[kien6034]

x/staking/keeper/delegation.go/

	if ctx.ChainID() == ColumbusChainID {
		// Get the last Total Power of the validator set
		lastPower := k.GetLastTotalPower(ctx)

		// Get the power of the current validator power
		validatorLastPower := sdk.TokensToConsensusPower(validator.Tokens, k.PowerReduction(ctx))

		// Get the new power of the validator if delegated the bond amount
		validatorNewPower := validatorLastPower + sdk.TokensToConsensusPower(bondAmt, k.PowerReduction(ctx))

		// Compute what the Total Consensus Power would be if this Delegation goes through
		newTotalPower := lastPower.Int64() + sdk.TokensToConsensusPower(bondAmt, k.PowerReduction(ctx))

		// Compute what the new Validator voting power would be in relation to the new total power
		// validatorIncreasedDelegationPercent := float32(validatorNewPower) / float32(newTotalPower)
		validatorIncreasedDelegationPercent := sdk.NewDec(validatorNewPower).QuoInt64(newTotalPower)

		// If Delegations are allowed, and the Delegation would have increased the Validator to over 20% of the staking power, do not allow the Delegation to proceed
		if validatorIncreasedDelegationPercent.GT(sdk.NewDecWithPrec(20, 2)) {
			panic("validator power is over the allowed limit")
		}
	}

Solution

We can introduce the AfterDelegationModifed hooks, which check the validator power < 20%

https://github.com/classic-terra/cosmos-sdk/blob/v0.47.10-terra.1/x/staking/keeper/delegation.go#L731-L733

Commit: 372f6f8