The default priority mechanism should be based on gas price rather than fee

[yihuang]

Summary of Bug

Currently the default priority mechanism is based on tx fee amount: https://github.com/cosmos/cosmos-sdk/blob/release/v0.46.x/x/auth/ante/validator_tx_fee.go#L54, I think it's more reasonable to based on price instead, fee = price * gas limit.

Version

main and 0.46

Steps to Reproduce

[tac0turtle]

would you not need an oracle to get price of the asset?

[yihuang]

would you not need an oracle to get price of the asset?

I mean the gas price specified in the tx, gas price = fee / gas limit, and use the amount of the price as the priority.
Otherwise, a tx that uses more gas will have a higher priority, even with the same gas price.

[yihuang]

It's also a workaround for this issue: informalsystems/hermes#2350
Because currently relayer is always configured with a static gas price, and with this change, it'll always get a static priority, which prevents the relayer msgs from reorder.

[alexanderbez]

I mean we can base it on gas price, but what does this buy us if the fee is based on the gas price? Also, the idea is that apps write their own priority AnteHandler.

Otherwise, a tx that uses more gas will have a higher priority, even with the same gas price.

Correct, but why is this a bad thing? Are you saying it's to give them equal/fair ranking?

[yihuang]

I mean we can base it on gas price, but what does this buy us if the fee is based on the gas price? Also, the idea is that apps write their own priority AnteHandler.

One concrete positivity is that the default setting won't break the IBC relayers, because currently they always set a static gas price, and they don't want their transactions to get reordered.

Otherwise, a tx that uses more gas will have a higher priority, even with the same gas price.

Correct, but why is this a bad thing? Are you saying it's to give them equal/fair ranking?

Yeah, it seems fairer to me, that's how ethereum has always been doing before EIP-1559.

[alexanderbez]

Ok, I don't see this as a problem actually. Makes sense. Wanna submit a quick PR @yihuang? :)

[yihuang]

Ok, I don't see this as a problem actually. Makes sense. Wanna submit a quick PR @yihuang? :)

sure, submitted.

[robert-zaremba]

One thing to note is that by default transactions are not charged based on the gas used but by the specified fee. So the fee equals gas_price * gas_limit (when gas price is provided)