engine

kona-engine

An extensible implementation of the OP Stack rollup node engine client.

Overview

The kona-engine crate provides a task-based engine client for interacting with Ethereum execution layers. It implements the Engine API specification and manages the execution layer state through a priority-driven task queue system.

Key Components

• Engine - Main task queue processor that executes engine operations atomically
• EngineClient - HTTP client for Engine API communication with JWT authentication
• EngineState - Tracks the current state of the execution layer
• Task Types - Specialized tasks for different engine operations:
  • InsertTask - Insert new payloads into the execution engine
  • BuildTask - Build new payloads with automatic forkchoice synchronization
  • ConsolidateTask - Consolidate unsafe payloads to advance the safe chain
  • FinalizeTask - Finalize safe payloads on L1 confirmation
  • SynchronizeTask - Internal task for execution layer forkchoice synchronization

Architecture

The engine implements a task-driven architecture where forkchoice synchronization is handled automatically:

• Automatic Forkchoice Handling: The BuildTask automatically performs forkchoice updates during block building, eliminating the need for explicit forkchoice management in user code.
• Internal Synchronization: SynchronizeTask handles internal execution layer synchronization and is primarily used by other tasks rather than directly by users.
• Priority-Based Execution: Tasks are executed in priority order to ensure optimal sequencer performance and block processing efficiency.

Engine API Compatibility

The crate supports multiple Engine API versions with automatic version selection based on the rollup configuration:

• Engine Forkchoice Updated: V2, V3
• Engine New Payload: V2, V3, V4
• Engine Get Payload: V2, V3, V4

Version selection follows Optimism hardfork activation times (Bedrock, Canyon, Delta, Ecotone, Isthmus).

Features

• metrics - Enable Prometheus metrics collection (optional)