EIP-7799: System logs

Per-block logs without associated transactions

Abstract

This EIP defines an extension for eth_getLogs to provide logs for events that are not associated with a given transaction, such as block rewards and withdrawals.

Motivation

With EIP-7708 wallets gain the ability to use eth_getLogs to track changes to their ETH balance. However, the ETH balance may change without an explicit transaction, through block production and withdrawals. By having such operations emit block-level system logs, eth_Logs provides a complete picture of ETH balance changes.

Specification

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “NOT RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in RFC 2119 and RFC 8174.

System logs list

A new list is introduced to track all block level logs emitted from system interactions. The definition uses the Log SSZ type from EIP-6466.

system_logs = List[Log, MAX_LOGS_PER_RECEIPT](
    log_0, log_1, log_2, ...)

Priority fee processing

EIP-1559 priority fees SHALL no longer be credited after each individual transaction. Instead, they SHALL be summed up and credited after all transactions of a block are processed but before EIP-4895 withdrawals are processed.

A log SHALL be appended to the system logs list to reflect this credit of priority fees.

Withdrawal processing

A log SHALL be appended to the system logs list on every EIP-4895 withdrawal.

Genesis processing

A log SHALL be appended to the system logs list when generating genesis blocks for networks that adopt this EIP from the beginning.

Execution block header changes

The execution block header is extended with a new field, system-logs-root.

block_header.system_logs_root = system_logs.hash_tree_root()

JSON-RPC API

Block header objects in the context of the JSON-RPC API are extended to include:

• systemLogsRoot: DATA, 32 Bytes

Log objects in the context of the JSON-RPC API are updated as follows:

• logIndex: QUANTITY - The additional system logs are indexed consecutively after the existing logs from transaction receipts
• transactionIndex: QUANTITY - null is also used for system logs; pending logs can still be identified by checking the blockHash for null
• transactionHash: DATA, 32 Bytes - null is also used for system logs

Engine API

In the engine API, the ExecutionPayload for versions corresponding to forks adopting this EIP is extended to include:

• systemLogsRoot: DATA, 32 Bytes

As part of engine_forkchoiceUpdated, Execution Layer implementations SHALL verify that systemLogsRoot for each block matches the actual value computed from local processing. This extends on top of existing receiptsRoot validation.

Consensus ExecutionPayload changes

The consensus ExecutionPayload type is extended with a new field to store the system logs root.

class ExecutionPayload(Container):
    ...
    system_logs_root: Root

Rationale

Together with EIP-7708 this EIP provides the ability for wallets to compute the exact ETH balance from logs without requiring download of every single block header and all withdrawals.

The block reward from priority fees no longer has to be summed up by processing all receipts and can be obtained from the system logs root, making it efficiently provable.

Batched crediting of priority fees improves parallel execution of transactions, as a transaction can no longer start with insufficient fees and only become eligible for execution after incremental priority fees have been credited.

Alternatives / Future

• Instead of combining the priority fees into a single payment, each transaction could emit the priority fee payment as a separate log. A per-transaction fee log is needed anyway for the fee burn. One could extend the payload of that as 2 sets of uint256, one for the burn, and one for the priority fee, instead of a combined fee; and also add the fee recipient as an additional topic to these logs so that it is indexed for eth_getLogs search. However, that would prevent parallel execution benefits as every transaction would continue to require an exclusive lock on the fee recipient’s account to credit the fee, and the total priority fees earned by a block would not be efficiently provable as it would require processing all of the receipts within the block.

• The information from withdrawals is now duplicated across both the withdrawals list and the system logs. Maybe the information could be massaged into the emitted Withdrawal log data, allowing the existing withdrawals list to be retired. The current list design requires the wallet to obtain all block headers and all withdrawals to ensure they obtained all data pertaining to the observed account. Allowing them to be queried using eth_getLogs is more in line with how deposits are being tracked.

• The log definitions themselves are subject to change. Aligning them with ERC-20 for plain credits provides consistency. For withdrawals, the log data could match the form of deposit logs and EIP-7685 request logs.

Backwards Compatibility

The fee recipient now receives priority fees at the end of the block rather than incrementally after each transaction, making it only possible to spend them in the next block. This may require updates to block builder infrastructure and change liquidity requirements for MEV use cases.

Security Considerations

The emitted logs use SYSTEM_ADDRESS as their address which cannot conflict with user controlled smart contracts.

Copyright

Copyright and related rights waived via CC0.

Citation

Please cite this document as:

Etan Kissling (@etan-status), Gajinder Singh (@g11tech), "EIP-7799: System logs [DRAFT]," Ethereum Improvement Proposals, no. 7799, October 2024. [Online serial]. Available: https://eips.ethereum.org/EIPS/eip-7799.