Crate pallet_dynamic_evm_base_fee

Dynamic Evm Base Fee Pallet

Overview

The pallet is responsible for calculating Base Fee Per Gas value, according to the current system parameters. This is not like EIP-1559, instead it’s intended for Astar and Astar-like networks, which allow both Substrate native transactions (which in Astar case reuse Polkadot transaction fee approach) and EVM transactions (which use Base Fee Per Gas).

For a more detailed description, reader is advised to refer to Astar Network forum post about Tokenomics 2.0.

Approach

The core formula this pallet tries to satisfy is:

base_fee_per_gas = adjustment_factor * weight_factor * 25 / 98974

Where:

• adjustment_factor - is a value that changes in-between the blocks, related to the block fill ratio.
• weight_factor - fixed constant, used to convert consumed weight to fee.

The implementation doesn’t make any hard requirements on these values, and only requires that a type implementing Get<_> provides them.

Implementation

The core logic is implemented in on_finalize hook, which is called at the end of each block. This pallet’s hook should be called AFTER whichever pallet’s hook is responsible for updating adjustment factor.

The hook will calculate the ideal new base_fee_per_gas value, and then clamp it in between the allowed limits.

Interface

Pallet provides an implementation of FeeCalculator trait. This makes it usable directly in pallet-evm.

A root-only extrinsic is provided to allow setting the base_fee_per_gas value manually.

Practical Remarks

According to the proposed Tokenomics 2.0, max amount that adjustment factor will be able to change on live networks in-between blocks is:

adjustment_new = adjustment_old * (1 + adj + adj^2/2)

adj = v * (s - s*) –> recommended v value: 0.000_015 –> largest ‘s’ delta: (1 - 0.25) = 0.75

(for variable explanation please check the linked forum post above) (in short: v - variability factor, s - current block fill ratio, s* - ideal block fill ratio)

adj = 0.000015 * (1 - 0.25) = 0.000_011_25 (1 + 0.000_011_25 + 0.000_011_25^2/2) = (1 + 0.000_011_25 + 0.000_000_000_063_281) = 1,000_011_250_063_281

Discarding the 1, and only considering the decimals, this can be expressed as ratio: Expressed as ratio: 11_250_063_281 / 1_000_000_000_000_000. This is a much smaller change compared to the max step limit ratio we’ll use to limit bfpg alignment. This means that once equilibrium is reached (fees are aligned), the StepLimitRatio will be larger than the max possible adjustment, essentially eliminating its effect.

Re-exports

• pub use weights::WeightInfo;
• pub use self::pallet::*;

Modules

• pallet
  The pallet module in each FRAME pallet hosts the most important items needed to construct this pallet.
• weights
  Autogenerated weights for pallet_dynamic_evm_base_fee