EIP-7840: Add blob schedule to EL config files

Include a per-fork schedule of max and target blob counts in client configuration files

Abstract

Add a new object to client configuration files blobSchedule which lists the target blob count per block and max blob count per block for each fork.

Motivation

• ensure there is a way to dynamically adjust the target and max blob counts per block
• avoid complex handshake over engine API

Specification

Extend the client configuration files with the object blobSchedule with the following shape:

"blobSchedule": {
  "cancun": {
    "target": 3,
    "max": 6
  },
  "prague": {
    "target": 6,
    "max": 9
  }
}

When there is no explicit configuration for the current fork, use the last specified fork value. If no last value is specified, set both to zero.

Rationale

Although maintaining the target and max blob only in the consensus client is desirable, we acknowledge the reality that execution clients need these values for various activities. For example, the eth_feeHistory RPC method returns a field blobGasUsedRatio that does require the max, even though the core protocol doesn’t specifically need such value. Passing this value over the engine API every block seem overkill so we believe a configuration value is a good middle ground.

Backwards Compatibility

No backward compatibility issues found.

Test Cases

TODO

Security Considerations

Needs discussion.

Copyright

Copyright and related rights waived via CC0.

Citation

Please cite this document as:

lightclient (@lightclient), "EIP-7840: Add blob schedule to EL config files [DRAFT]," Ethereum Improvement Proposals, no. 7840, December 2024. [Online serial]. Available: https://eips.ethereum.org/EIPS/eip-7840.