execution

README

Go Execution EVM

This repository implements the execution.Executor interface from github.com/rollkit/rollkit/core/execution (currently on feature branch feature/exec_api). It provides a pure Engine API-based execution client for Rollkit.

PureEngineClient Implementation

The PureEngineClient is a 100% Engine API compatible implementation of the execution.Executor interface. It connects to an Ethereum execution client (like Reth) and uses both the Engine API and standard Ethereum JSON-RPC API to execute transactions.

Genesis and initial height

In the context of the EVM, the genesis block is designated as a unique block with the block number 0. To ensure compatibility with both rollkit and the EVM, the only permissible initial height is 1. During InitChain EVM genesis block is acknowledged (at height 0), and empty block is created (at height 1). This approach ensures that the block numbers between the EVM and rollkit remain consistent and synchronized.

Genesis Requirements

Since the PureEngineClient relies on the Engine API, the genesis configuration must properly enable it with the correct hardfork settings:

1. The genesis file must include post-merge hardfork configurations
2. terminalTotalDifficulty must be set to 0
3. terminalTotalDifficultyPassed must be set to true
4. Hardforks like mergeNetsplitBlock, shanghaiTime, and cancunTime should be properly configured

Example of required genesis configuration:

{
  "config": {
    "chainId": 1234,
    "homesteadBlock": 0,
    "eip150Block": 0,
    "eip155Block": 0,
    "eip158Block": 0,
    "byzantiumBlock": 0,
    "constantinopleBlock": 0,
    "petersburgBlock": 0,
    "istanbulBlock": 0,
    "berlinBlock": 0,
    "londonBlock": 0,
    "mergeNetsplitBlock": 0,
    "terminalTotalDifficulty": 0,
    "terminalTotalDifficultyPassed": true,
    "shanghaiTime": 0,
    "cancunTime": 0
  }
}

Without these settings, the Engine API will not be available, and the PureEngineClient will not function correctly.

PayloadID Storage

The PureEngineClient maintains the payloadID between calls:

1. During InitChain, a payload ID is obtained from the Engine API via engine_forkchoiceUpdatedV3
2. This payload ID is stored in the client instance as c.payloadID
3. The stored payload ID is used in subsequent calls to GetTxs to retrieve the current execution payload
4. After each ExecuteTxs call, a new payload ID is obtained and stored for the next block

Payload as First Transaction

The PureEngineClient implements a unique approach to transaction execution:

1. In GetTxs, the entire execution payload is serialized to JSON and returned as the first transaction
2. In ExecuteTxs, this first transaction is deserialized back into an execution payload
3. The remaining transactions are added to the payload's transaction list
4. The complete payload is then submitted to the execution client via engine_newPayloadV3

This approach ensures that:

• The execution payload structure is preserved between calls
• All execution happens within the EVM
• It's not possible to create a payload outside of the EVM
• Transactions cannot be selected or ordered outside of the EVM

How Eth API is Used

The PureEngineClient uses the standard Ethereum JSON-RPC API for:

1. Retrieving block information (via HeaderByNumber)
2. Reading the genesis block hash and state root
3. Getting gas limits and other block parameters

This allows the client to interact with the execution layer for read operations while using the Engine API for write operations.

Deployment Architecture

graph LR
    subgraph Rollkit Binary
        RollkitCore[Rollkit Core]
        PureEngineClient[PureEngineClient]
    end

    %% Connections
    RollkitCore --> PureEngineClient
    PureEngineClient -->|Engine API| Reth
    PureEngineClient -->|Eth API| Reth

Development and Testing

Running Reth in Docker

cd docker
docker compose up -d

Reading Genesis Information

If you've modified the genesis file, you can read the genesis hash and state root using the Ethereum JSON-RPC API:

# Get genesis block hash
curl -X POST -H "Content-Type: application/json" --data '{"jsonrpc":"2.0","method":"eth_getBlockByNumber","params":["0x0", false],"id":1}' http://localhost:8545 | jq -r '.result.hash'

# Get genesis state root
curl -X POST -H "Content-Type: application/json" --data '{"jsonrpc":"2.0","method":"eth_getBlockByNumber","params":["0x0", false],"id":1}' http://localhost:8545 | jq -r '.result.stateRoot'

Documentation

Index

• Variables
• type PureEngineClient
  • func NewPureEngineExecutionClient(ethURL, engineURL string, jwtSecret string, genesisHash common.Hash, ...) (*PureEngineClient, error)
  • func (c *PureEngineClient) ExecuteTxs(ctx context.Context, txs [][]byte, blockHeight uint64, timestamp time.Time, ...) (updatedStateRoot []byte, maxBytes uint64, err error)
  • func (c *PureEngineClient) GetTxs(ctx context.Context) ([][]byte, error)
  • func (c *PureEngineClient) InitChain(ctx context.Context, genesisTime time.Time, initialHeight uint64, ...) ([]byte, uint64, error)
  • func (c *PureEngineClient) SetFinal(ctx context.Context, blockHeight uint64) error

Variables

var (
	// ErrNilPayloadStatus indicates that PayloadID returned by EVM was nil
	ErrNilPayloadStatus = errors.New("nil payload status")
	// ErrInvalidPayloadStatus indicates that EVM returned status != VALID
	ErrInvalidPayloadStatus = errors.New("invalid payload status")
)

Types

type PureEngineClient

type PureEngineClient struct {
	// contains filtered or unexported fields
}

PureEngineClient represents a client that interacts with an Ethereum execution engine through the Engine API. It manages connections to both the engine and standard Ethereum APIs, and maintains state related to block processing.

func NewPureEngineExecutionClient

func NewPureEngineExecutionClient(
	ethURL,
	engineURL string,
	jwtSecret string,
	genesisHash common.Hash,
	feeRecipient common.Address,
) (*PureEngineClient, error)

NewPureEngineExecutionClient creates a new instance of EngineAPIExecutionClient

func (*PureEngineClient) ExecuteTxs

func (c *PureEngineClient) ExecuteTxs(ctx context.Context, txs [][]byte, blockHeight uint64, timestamp time.Time, prevStateRoot []byte) (updatedStateRoot []byte, maxBytes uint64, err error)

ExecuteTxs executes the given transactions at the specified block height and timestamp

func (*PureEngineClient) GetTxs

func (c *PureEngineClient) GetTxs(ctx context.Context) ([][]byte, error)

GetTxs retrieves transactions from the current execution payload

func (*PureEngineClient) InitChain

func (c *PureEngineClient) InitChain(ctx context.Context, genesisTime time.Time, initialHeight uint64, chainID string) ([]byte, uint64, error)

InitChain initializes the blockchain with the given genesis parameters

func (*PureEngineClient) SetFinal

func (c *PureEngineClient) SetFinal(ctx context.Context, blockHeight uint64) error

SetFinal marks the block at the given height as finalized