Support dynamic fees for chains with fee market (EIP-1559)

[ertemann]

Summary

With Osmosis and other chains adopting the Skip Block SDK and EIP1559 the gas fees are now no longer stagnant. We have had 2 times already where our relayer stopped because the on-chain feel went above our configured amount.

We would love a feature that allows to make the fee dynamic based on the on-chain endpoint: lcd.osmosis.zone/osmosis/txfees/v1beta1/cur_eip_base_fee

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[ljoss17]

Hi @ertemann thanks for opening this issue. I have the following proposal as a solution which will need some investigation from our side:

Proposal

Depending on what data Hermes has access there are two possible solutions:

1. Hermes is able to retrieve the base_fee when simulating the Tx
2. Hermes can query the base_fee

For both solutions, once the base_fee has been retrieved the behaviour would then be similar to what is being done for gas amount:

1. Try to retrieve the base_fee
   a. If it succeeds, use that value
   b. If it fails use a fallback value default_gas_price
2. Check that the base_fee is not higher than a configured max_gas_price
3. Relay Tx

[romac]

We are planning to implement proper support for dynamic gas price based on the upcoming EIP-1559 FeeMarket module provided by the Skip SDK.

Until then, for Osmosis one can use this fork of Hermes by Osmosis which adapts the gas price dynamically based on the osmosis/txfees/v1beta1/cur_eip_base_fee endpoint.