Abstract

This HIP describes initial support of JSON-RPC Relay and Mirror Node APIs for handling EVM transaction debugging requests.

Motivation

Ethereum nodes can be configured to enable support for debugging historical transactions and thus producing a detailed output log with information related to the transaction execution.

Hedera’s current architecture consists of three types of nodes:

• JSON-RPC Relay nodes expose the same JSON-RPC API that Ethereum nodes use and handle user requests by either forwarding them to a Consensus node or Mirror node.
• Consensus nodes execute transactions, produce transaction records, and maintain the world state.
• Mirror nodes ingest the record files produced by the consensus nodes, maintain a “mirror” of the world state, and provide an API for queries and simulations which can work with the current, or a historical state.

Ongoing user experience work needs EVM execution to enable debugging historical transactions. Enhancing Mirror Archive Node with debug calls would allow users to replay historical transactions and inspect and analyse them by having detailed information for the execution based on a tracer type that is specified in the request. In addition, this enhancement would improve Hedera interoperability with different ethereum tools and providers, including Remix, Hardhat, Ganache, Geth, Alchemy, etc.

Rationale

Add support of debug_traceTransaction in the JSON-RPC Relay which returns detailed information for a historical transaction that was executed in the past.

The JSON-RPC Relay will make a request to the Mirror Node REST API which will be enhanced with a couple of new endpoints that return debug logs.

In order to enable trace calls, we should meet some requirements:

• Support EVM versioning, so that we use the appropriate EVM version for a specific historical block.
• Use full mirror node, keeping state from the genesis block and configured with enabled ingest of CONTRACT_BYTECODE , CONTRACT_STATE_CHANGE and CONTRACT_ACTION sidecar types.
• Re-execute historical transactions using the information for state values read from the downloaded CONTRACT_STATE_CHANGE sidecar record files.

User stories

1. As a user, I want to perform debug_traceTransaction calls to explore the op code traces for a historical transaction.
2. As a user, I want to perform debug_traceTransaction calls to explore the sub calls that were executed for a historical transaction.

Specification

JSON-RPC Relay Trace API

The JSON-RPC Relay will be enhanced with a debug_traceTransaction endpoint. The endpoint has one required parameter - transactionHash - and also accepts list of properties - a tracer, and a list of configuration flags.

Example payload: