MIP-52: Aptos Gas Pool

  • Description: Introduces implementation specification for the Gas Pool in the Aptos Framework
  • Authors: Liam Monninger
  • Desiderata: MD-38

Abstract

We propose a means of implementing a Gas Pool in Aptos to satisfy the token recirculation requirements indicated in MD-38. This solution will allow for gas used to be stored in the pool. The re-use of said gas is not a subject of this MIP. However, MIP-44, MIP-41, et al. provide suggestions to this end.

Motivation

The introduction of a Gas Pool in Aptos will allow for the recirculation of gas used in the Aptos Framework based ecosystem. This ensures the supply can remain fixed and the gas can be re-used for purposes such as rewarding.

Specification

Aptos pays gas in the epilogue of a transaction dispatching to epilogue_gas_payer. Depending on the validator reward setting, epilogue_gas_payer will either call transaction_fee::collect_fee or transaction_fee::burn_fee.

At the time of writing the transaction_fee::collect_fee path is still experimental.

transaction_fee::burn_fee internally calls coin::burn_from which can be replaced with a transfer.

We thus suggest two paths to implement the Gas Pool in Aptos:

  • Custom Rewards Collection
  • Burn Replacement

Custom Rewards Collection

The custom rewards collection approach replaces Aptos’ experimental transaction_fee::collect_fee with a custom rewards collection mechanism. This mechanism calls coin::transfer_from to move the gas to the Gas Pool at a known address.

Coin burning logic can be kept in place and a similar features-based approach can be used to determine ensure the transaction_fee::collect_fee approach is used.

Burn Replacement

The burn replacement approach replaces the coin::burn_from call in transaction_fee::burn_fee with a coin::transfer_from call to the Gas Pool.

Verification

Outstanding:

  • Verify that the AptosVM does not validate burns. Otherwise, there may be logic outside of the framework epilogue_gas_payer path which needs to be updated.
  • Identify any sponsorship or other gas payment mechanisms which may need to be updated to use the Gas Pool.

Appendix

Changelog