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Overview

The SystemConfig is updated to allow for dynamic EIP-1559 parameters.

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ConfigUpdate

When the configuration is updated, a ConfigUpdate event MUST be emitted with the following parameters:
versionupdateTypedataUsage
uint256(0)uint8(4)abi.encode((uint256(_denominator) << 32) | _elasticity)Modifies the EIP-1559 denominator and elasticity
Note that the above encoding is the format emitted by the SystemConfig event, which differs from the format in extraData from the block header.

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Initialization

The following actions should happen during the initialization of the SystemConfig:
  • emit ConfigUpdate.BATCHER
  • emit ConfigUpdate.FEE_SCALARS
  • emit ConfigUpdate.GAS_LIMIT
  • emit ConfigUpdate.UNSAFE_BLOCK_SIGNER
Intentionally absent from this is emit ConfigUpdate.EIP_1559_PARAMS. As long as these values are unset, the default values will be used. Requiring 1559 parameters to be set during initialization would add a strict requirement that the L2 hardforks before the L1 contracts are upgraded, and this is complicated to manage in a world of many chains.

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Modifying EIP-1559 Parameters

A new SystemConfig UpdateType is introduced that enables the modification of EIP-1559 parameters. This allows for the chain operator to modify the BASE_FEE_MAX_CHANGE_DENOMINATOR and the ELASTICITY_MULTIPLIER.

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Interface

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EIP-1559 Params

setEIP1559Params
This function MUST only be callable by the chain governor. 
function setEIP1559Params(uint32 _denominator, uint32 _elasticity)
The _denominator and _elasticity MUST be set to values greater to than 0. It is possible for the chain operator to set EIP-1559 parameters that result in poor user experience.
eip1559Elasticity
This function returns the currently configured EIP-1559 elasticity. 
function eip1559Elasticity()(uint32)
eip1559Denominator
This function returns the currently configured EIP-1559 denominator. 
function eip1559Denominator()(uint32)