Kakarot RPC

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Table of Contents

• Report a Bug
• Request a Feature
• About
• Architecture
  • High level
  • Low level
• Getting Started
  • Prerequisites
• Installation
  • Setup the project
  • Build from source
  • Environment variables
  • Dev mode with Katana
  • Building a Docker Image
  • Sending transactions to RPC using forge script
  • Configuration
• Running a Node in Various Environments
  • Local Environment
  • Staging Environment
  • Production Environment
  • Potential Pitfalls, Caveats, and Requirements
    • Requirements
    • Potential Pitfalls
    • Caveats
  • API
• Testing
  • Rust tests
  • Apibara indexer tests
  • Hive
• Project assistance
• Contributing
• Glossary
• Authors & contributors
• Security
• License
• Acknowledgements
• Benchmarks
• Contributors ✨

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About

Kakarot RPC fits in the three-part architecture of the Kakarot zkEVM rollup (Kakarot EVM Cairo Programs, Kakarot RPC, Kakarot Indexer). It is the implementation of the Ethereum JSON-RPC specification made to interact with Kakarot zkEVM in a fully Ethereum-compatible way.

The Kakarot RPC layer's goal is to receive and output EVM-compatible payloads & calls while interacting with an underlying StarknetOS client. This enables Kakarot zkEVM to interact with the usual Ethereum tooling: Metamask, Hardhat, Foundry, etc.

Note that this is necessary because Kakarot zkEVM is implemented as a set of Cairo Programs that run on an underlying CairoVM (so-called StarknetOS) chain.

This adapter layer is based on:

• The Ethereum JSON-RPC spec
• The Starknet JSON-RPC spec
• And their differences

Architecture

High level

Here is a high level overview of the architecture of Kakarot RPC.

Low level

Below is a lower level detailed overview of the internal architecture.

Getting Started

TL;DR:

• Run make setup to build dependencies.
• Run cargo build to build Kakarot RPC.
• Test with make test.
• Run Kakarot RPC in dev mode:
  • Run dev RPC: make run-dev (you'll need a StarknetOS instance running in another process and Kakarot contracts deployed)
• Run with Docker Compose:
  • make local-rpc-up
  • To kill these processes, make docker-down
• Build the docker image for the RPC:
  • make docker-build

Prerequisites

• Rust: The codebase is written in Rust to ensure high performance, maintainability, and a developer-friendly experience.
• Docker: Required for containerizing and running the various services and components in a consistent environment.
• Python: Used primarily for interacting with and building our Kakarot programs.
• UV: An extremely fast Python package and project manager, written in Rust. Used for managing the dependencies of our Kakarot programs.
• Deno: A JavaScript runtime used for our indexing service, based on the Apibara third-party service.
• Make: Utilized to interact with the Makefile for running commands such as building the project or executing tests.

Installation

Setup the project

To set up the repository (pulling git submodule and building Cairo dependencies), run:

make setup

Caveats:

1. the setup make command uses linux (MacOs compatible) commands to allow running the ./scripts/extract_abi.sh. This script is used to use strongly typed Rust bindings for Cairo programs. If you encounter problems when building the project, try running ./scripts/extract_abi.sh.
2. the kakarot submodule uses Python to build and deploy Kakarot contracts. If you don't have the right version available, we recommend to use pyenv to install it.
3. We use a pre-commit hook to ensure code quality and consistency. The hook are managed and automatically installed by trunk.

Build from source

To build the project from source (in release mode):

cargo build --release

Note that there are sometimes issues with some dependencies (notably scarb or cairo related packages, there are sometimes needs to cargo clean and cargo build)

Environment variables

Copy the .env.example file to a .env file and populate each variable

cp .env.example .env

Meanwhile you can just use unit tests to dev.

make test

The binaries will be located in target/release/.

Dev mode with Katana

To run a local Starknet sequencer, you can use Katana. Katana, developed by the Dojo team, is a sequencer designed to aid in local development. It allows you to perform all Starknet-related activities in a local environment, making it an efficient platform for development and testing. To run Katana and deploy the Kakarot zkEVM (a set of Cairo smart contracts implementing the EVM):

make run-katana

This command will install Katana and generate a genesis file at .katana/genesis.json. Katana's genesis configuration feature is a way to define the initial state and settings of the Kakarot blockchain network locally, providing a customizable starting point for the chain. Among other things, it allows you to:

• Specify the token used for network fees.
• Allocate initial token balances to accounts.
• Pre-declare classes at the start of the chain.
• Pre-deploy smart contracts at the start of the chain.

To deploy Kakarot Core EVM (set of Cairo Programs):

 make deploy-kakarot

To run the Kakarot RPC pointing to this local devnet:

STARKNET_NETWORK=katana make run-dev

Some notes on this local devnet:

• this will run a devnet by running katana, with contracts automatically deployed, so you don't have to do them manually (see in ./lib/kakarot/kakarot_scripts/deploy_kakarot.py for the list of contracts).

• the deployments and declarations for the devnet will be written to the deployments/katana folder inside your project root after a successful run of the make deploy-kakarot command.

Building a Docker Image

In order to build a Docker Image for the RPC, you can run the below command which will setup the local environment and compile the binary:

make docker-build

Sending transactions to RPC using forge script

An example script to run which uses a pre-funded EOA account with private key EVM_PRIVATE_KEY

forge script scripts/PlainOpcodes.s.sol --broadcast --legacy --slow

Configuration

Kakarot RPC is configurable through environment variables. Check out .env.example file to see the environment variables.

Running a Node in Various Environments

This section outlines how to run a complete node in different environments: local, staging, and production. Running a node involves several critical components to ensure the system operates effectively:

• Starknet Engine: Interacts with the Starknet ecosystem and processes transactions.
• Kakarot Programs: Implement the EVM logic using Cairo.
• RPC Node: Manages the Ethereum RPC logic, facilitating smooth interaction with the Kakarot chain.
• Apibara Service: Monitors the Kakarot chain and indexes its data.
• MongoDB: Serves as the database for storing transactions after indexing and acts as the core component for fetching information.

By correctly configuring these components, you can ensure that the node functions as a robust part of the system.

In the following sections we have tried to provide the most important parameters useful for understanding and configuring the node. However for the sake of brevity, certain parameters deemed less important are omitted and can all be found in the corresponding Docker compose files:

• Local: docker-compose.yaml
• Staging: docker-compose.staging.yaml
• Production: docker-compose.prod.yaml

Local Environment

To start the entire infrastructure locally, use the following command:

make local-rpc-up

This command will use the docker-compose.yaml file to set up the whole infrastructure locally utilizing the following elements:

• Katana (local sequencer):

  • Fees disabled (ETH and STRK gas price set to 0).
  • Maximum steps for account validation logic set to 16,777,216.
  • Maximum steps for account execution logic set to 16,777,216.
  • Chain ID set to KKRT (0x4b4b5254 in ASCII).

• Kakarot EVM Programs:

  • Prefunded Katana account with:
    • Account address: 0xb3ff441a68610b30fd5e2abbf3a1548eb6ba6f3559f2862bf2dc757e5828ca.
    • Private key: 0x2bbf4f9fd0bbb2e60b0316c1fe0b76cf7a4d0198bd493ced9b8df2a3a24d68a.
  • Anvil (local Ethereum node):
    • Private key: 0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80.
  • Katana RPC URL: http://starknet:5050.
  • Network: STARKNET_NETWORK=katana.

• Kakarot RPC Node on port 3030:

  • MongoDB connection string: MONGO_CONNECTION_STRING=mongodb://mongo:mongo@mongo:27017.
  • Database name: MONGO_DATABASE_NAME=kakarot-local.
  • Max calldata felts: 30,000.
  • Pending transactions stored in MongoDB, with a retry service running every second.
  • Currently, Kakarot does not support pre-EIP-155 transactions, except for a whitelist of specific transaction hashes that can be found in the corresponding Docker compose file.

• Apibara Indexer Service on port 7171:

  • Uses the Starknet node URL for RPC.
  • Configured with MongoDB and Kakarot addresses.

• MongoDB with Mongo Express on port 27017 for data management.

• Blockscout on port 4000, provides a web interface for exploring and analyzing blockchain data.

Staging Environment

To start the entire infrastructure in the staging environment, use the following command:

make staging-rpc-up

This command will use the docker-compose.staging.yaml file to set up the whole infrastructure in the staging configuration utilizing the following elements:

• Starknet Full-Node (Juno) on port 6060:

  • Pending block is synced to the head of the chain every second.
  • Ethereum node websocket endpoint to be specified by env variable ETH_NODE_WS (for example ETH_NODE_WS=wss://eth-sepolia.g.alchemy.com/v2/YOUR_API_KEY).
  • Network configuration:
    • Network name: KKRT_BETA.
    • Network feeder URL: https://gateway-beta.kakarot.sw-dev.io/feeder_gateway/.
    • Network gateway URL: https://gateway-beta.kakarot.sw-dev.io/gateway/.
    • L1 chain ID: 11155111 (Ethereum Sepolia).
    • L2 chain ID: kkrt.
    • Core contract address: 0xc7c9ea7fD0921Cb6EDd9a3184F88cF1b821aA82B.
    • Network range of blocks to skip hash verifications: 0 to 0.

• Starknet Explorer on port 4000:

  • RPC API hosts.
  • Database connection details for Postgres.
  • Secret key base for security.
  • Listener enabled for synchronizing with the Starknet node.

• Starknet Explorer Database (Postgres) on port 5432.

• Kakarot RPC Node on port 3030:

  • Starknet network URL: http://starknet:6060.
  • MongoDB connection string: mongodb://mongo:mongo@mongo:27017.
  • Database name: kakarot-local.
  • Kakarot address: 0x2824d6ed6759ac4c4a54a39b78d04c0e48be8937237026bf8c3bf46a8bea722.
  • Uninitialized account class hash: 0x600f6862938312a05a0cfecba0dcaf37693efc9e4075a6adfb62e196022678e.
  • Max calldata felts: 30,000.
  • Pending transactions stored in MongoDB, with a retry service running every 10 second.
  • Whitelisted pre-EIP-155 transaction hashes (see the corresponding Docker compose file).

• Apibara DNA Indexer Service on port 7171:

  • Uses the Starknet node URL for RPC.
  • Configured with MongoDB and Kakarot addresses.

• MongoDB with Mongo Express on port 27017 for data management.

• Blockscout on port 4001, provides a web interface for exploring and analyzing blockchain data.

Production Environment

To start the entire infrastructure in the production environment, use the following command:

make testnet-rpc-up

This command will use the docker-compose.prod.yaml file to set up the whole infrastructure in the production configuration utilizing the following elements:

• Starknet Full-Node (Juno) on port 6060:

  • Synchronizes pending blocks to the head of the chain every second.
  • Ethereum node websocket endpoint specified by ETH_NODE_WS (for example ETH_NODE_WS=wss://eth-sepolia.g.alchemy.com/v2/YOUR_API_KEY).
  • Network configuration:
    • Network name: kakarot-sepolia.
    • Network feeder URL: https://gateway.kakarot.sw-dev.io/feeder_gateway/.
    • Network gateway URL: https://gateway.kakarot.sw-dev.io/gateway/.
    • L1 chain ID: 11155111 (Ethereum Sepolia).
    • L2 chain ID: kkrt.
    • Core contract address: 0x74Ca1aC5BD4c3c97006d2B7b9375Dd3B6C17ACcD.
    • Network range of blocks to skip hash verifications: 0 to 1000000.

• Starknet Explorer on port 4000:

  • RPC API hosts.
  • Database connection details for Postgres.
  • Secret key base for security.
  • Listener enabled for synchronizing with the Starknet node.

• Starknet Explorer Database (Postgres) on port 5432.

• Kakarot RPC Node on port 3030:

  • Starknet network URL: http://starknet:6060.
  • MongoDB connection string: mongodb://mongo:mongo@mongo:27017.
  • Database name: kakarot-local.
  • Kakarot address: 0x11c5faab8a76b3caff6e243b8d13059a7fb723a0ca12bbaadde95fb9e501bda.
  • Uninitialized account class hash: 0x600f6862938312a05a0cfecba0dcaf37693efc9e4075a6adfb62e196022678e.
  • Account contract class hash: 0x1276d0b017701646f8646b69de6c3b3584edce71879678a679f28c07a9971cf.
  • Max calldata felts: 30,000.
  • Pending transactions stored in MongoDB, with a retry service running every 10 seconds.
  • Whitelisted pre-EIP-155 transaction hashes (see local environment).

• Apibara DNA Indexer Service on port 7171:

  • Uses the Starknet node URL for RPC.
  • Configured with MongoDB and Kakarot addresses.

• MongoDB with Mongo Express on port 27017 for data management.

• Blockscout on port 4001, provides a web interface for exploring and analyzing blockchain data.

Potential Pitfalls, Caveats, and Requirements

When setting up the Kakarot node in any environment, it's important to be aware of the following:

Requirements

• Hardware: Ensure your system meets the necessary hardware requirements for running Docker containers efficiently. A modern multi-core CPU, at least 16GB of RAM, and ample storage space are recommended.
• Software: Install the latest versions of Docker and Docker Compose to ensure compatibility with the provided configuration.
• Network: Stable internet connection for downloading images and communicating with remote services if needed. We have noticed difficulties on networks with low bandwidth.

Potential Pitfalls

• Resource Limits: Docker containers might consume significant system resources. Monitor system performance and consider adjusting container resource limits if necessary.
• Network Configuration: Ensure no port conflicts on your local machine, especially with ports 3030, 5050, 6060, 7171, 27017... used by the services.
• Volume Persistence: Docker volumes are used for data persistence. Ensure they are properly managed and backed up to prevent data loss.

Caveats

• Pre-EIP-155 Transactions: Kakarot does not natively support pre-EIP-155 transactions, except for those whitelisted. Be cautious about transaction compatibility.
• Environment Configuration: Double-check environment variables and their values, particularly those related to security, such as private keys and database credentials.
• Service Dependencies: The order of service initialization is crucial. Dependencies between services must be respected to avoid runtime errors.

API

You can take a look at rpc-call-examples directory. Please note the following:

• sendRawTransaction.hurl: the raw transaction provided allows to call the inc() function for the Counter contract. However, given that this transaction is signed for the EOA's nonce at the current devnet state (0x2), the call will only work once. If you want to keep incrementing (or decrementing) the counter, you need to regenerate the payload for the call with an updated nonce using the provided python script.

Testing

Rust tests

In order to execute the Rust tests, follow the below instructions:

• Run make setup in order to setup the project.
• Run make test which will create a Genesis test file for Kakarot and launch tests.
• If you which to only run a specific test, be sure to first at least run make katana-genesis once, then run make test-target TARGET=test_you_want_to_run.

Apibara indexer tests

In order to run the Typescript unit tests, you will need to have Deno installed. Then you can run KAKAROT_ADDRESS=ADDRESS_YOU_WANT_TO_USE_FOR_KAKAROT deno test --allow-env.

Hive

The Hive end-to-end test suite is set up in the Github Continuous Integration (CI) flow of the repository. This ensures a safe guard when modifying the current RPC implementation and/or the execution layer.

Due to the current existing differences between the Kakarot EVM implementation which aims to be a type 2 ZK-EVM (see the blog post from Vitalik for more details), some of the Hive tests need to be skipped or slightly modified in order to pass.

For the hive rpc tests, all the websockets related tests are skipped as websockets aren't currently supported by the Kakarot RPC.

For the hive rpc compatibility tests, the following tests are skipped:

• debug_getRawBlock/get-block-n: the Kakarot implementation currently doesn't compute the block hash following EVM standards.
• debug_getRawBlock/get-genesis: see debug_getRawBlock/get-block-n.
• debug_getRawHeader/get-block-n: debug API is currently not supported by the Kakarot RPC.
• debug_getRawHeader/get-genesis: debug API is currently not supported by the Kakarot RPC.
• debug_getRawHeader/get-invalid-number: debug API is currently not supported by the Kakarot RPC.
• debug_getRawTransaction/get-invalid-hash: the Kakarot implementation of the debug_getRawTransaction endpoint uses alloy_primitives::B256 type when deserializing the hash. This test is expected to fail as the provided hash in the query doesn't start with 0x. As this test doesn't bring much, we decide to skip it.
• eth_createAccessList/create-al-multiple-reads: the createAccessList endpoint is currently not supported by the Kakarot RPC.
• eth_createAccessList/create-al-simple-contract: the createAccessList endpoint is currently not supported by the Kakarot RPC.
• eth_createAccessList/create-al-simple-transfer: the createAccessList endpoint is currently not supported by the Kakarot RPC.
• eth_feeHistory/fee-history: the Kakarot implementation doesn't currently set the block gas limit dynamically, which causes some disparity in the returned data. Additionally, the rewards of the blocks aren't available.
• eth_getBalance/get-balance-blockhash: see debug_getRawBlock/get-block-n.
• eth_getBlockByHash/get-block-by-hash: see debug_getRawBlock/get-block-n.
• eth_getBlockReceipts/get-block-receipts-by-hash: see debug_getRawBlock/get-block-n.
• eth_getBlockTransactionCountByHash/get-block-n: see debug_getRawBlock/get-block-n.
• eth_getBlockTransactionCountByHash/get-genesis: see debug_getRawBlock/get-block-n.
• eth_getProof/get-account-proof-blockhash: the getProof endpoint is currently not supported by the Kakarot RPC.
• eth_getProof/get-account-proof-with-storage: the getProof endpoint is currently not supported by the Kakarot RPC.
• eth_getProof/get-account-proof: the getProof endpoint is currently not supported by the Kakarot RPC.
• eth_getStorage/get-storage-invalid-key-too-large: the Kakarot implementation of the eth_getStorage endpoint uses alloy_primitives::U256 type when deserializing the number. This test is expected to fail as the provided block number in the query doesn't start with exceeds 32 bytes. As this test doesn't bring much, we decide to skip it.
• eth_getStorage/get-storage-invalid-key: the Kakarot implementation uses the jsonrpsee crate's macro rpc in order to generate the server implementation of the ETH API. This test passes an invalid block hash 0xasdf and expects the server to return with an error code -32000 which corresponds to an invalid input error. The code derived from the rpc macro returns an error code of -32602 which corresponds to an invalid parameters error, whenever it encounters issues when deserializing the input. We decide to ignore this test as the only issue is the error code returned.
• eth_getTransactionByBlockHashAndIndex/get-block-n: see debug_getRawBlock/get-block-n.

In addition to the tests we skip, some of the objects fields need to be ignored in the passing tests:

• For blocks: the hash, parent hash, timestamp, base fee per gas, difficulty, gas limit, miner, size, state root, total difficulty and withdrawals are all skipped. Due to the difference between a type 1 and a type 2 ZK-EVM, these fields are currently not computed according to the EVM specifications and need to be skipped.
• For receipts, transactions and logs: the block hash is skipped.

If you which to run our hive test suite locally, the following steps should be taken:

• Set up the repo: make setup.

• Build a local docker image of the RPC. Check the hive Dockerfile for the values for xxx and yyy:

  docker build --build-arg APIBARA_STARKNET_BIN_DIR=xxx --build-arg APIBARA_SINK_BIN_DIR=yyy  -t hive . -f docker/hive/Dockerfile

• Checkout the Kakarot fork of hive: git clone https://github.com/kkrt-labs/hive

• Build the hive binary: go build hive.go

• Run the full rpc test suite against Kakarot: ./hive --sim "ethereum/rpc" --client kakarot

• Additional filtering can be provided using --sim.limit if you which to run a certain limited set of tests.

Project assistance

If you want to say thank you or/and support active development of Kakarot RPC:

• Add a GitHub Star to the project.
• Tweet about the Kakarot RPC: https://x.com/KakarotZkEvm.

Contributing

First off, thanks for taking the time to contribute! Contributions are what make the open-source community such an amazing place to learn, inspire, and create. Any contributions you make will benefit everybody else and are greatly appreciated.

Please read our contribution guidelines, and thank you for being involved!

Glossary

• StarknetOS chain: also called CairoVM chain, or Starknet appchain, it is a full-node (or sequencer) that is powered by the Cairo VM (Cairo smart contracts can be deployed to it). It a chain that behaves in most ways similarly to Starknet L2.
• Kakarot Core EVM: The set of Cairo Programs that implement the Ethereum Virtual Machine instruction set.
• Katana: A StarknetOS sequencer developed by the Dojo team. Serves as the underlying StarknetOS client for Kakarot zkEVM locally. It is built with speed and minimalism in mind.
• Madara: A StarknetOS sequencer and full-node developed by the Madara (e.g. Pragma Oracle, Deoxys, etc.) and Starkware exploration teams. Based on the Substrate framework, it is built with decentralization and robustness in mind.
• Kakarot zkEVM: the entire system that forms the Kakarot zkRollup: the core EVM Cairo Programs and the StarknetOS chain they are deployed to, the RPC layer (this repository), and the Kakarot Indexer (the backend service that ingests Starknet data types and formats them in EVM format for RPC read requests).

Authors & contributors

For a full list of all authors and contributors, see the contributors page.

Security

Kakarot RPC follows good practices of security, but 100% security cannot be assured. Kakarot RPC is provided "as is" without any warranty. Use at your own risk.

For more information and to report security issues, please refer to our security documentation.

License

This project is licensed under the MIT license.

See LICENSE for more information.

Acknowledgements

We warmly thank all the people who made this project possible.

• Reth (Rust Ethereum), Thank you for providing open source libraries for us to reuse.
• jsonrpsee
• Starkware and its exploration team, thank you for helping and providing a great test environment with Madara.
• Lambdaclass
• Dojo, thank you for providing great test utils.
• starknet-rs, thank you for a great SDK.
• All our contributors. This journey wouldn't be possible without you.

Benchmarks

For now, Kakarot RPC provides a minimal benchmarking methodology. You'll need Bun installed locally.

• Run a Starknet node locally (Katana or Madara), e.g. katana --block-time 6000 --disable-fee if you have the dojo binary locally, or make madara-rpc-up for Madara.
• Deploy the Kakarot smart contract (make deploy-kakarot)
• Run the Kakarot RPC binary (make run-dev)
• Run make benchmark-katana or make benchmark-madara

Contributors ✨

Thanks goes to these wonderful people (emoji key):

Abdel @ StarkWare 💻	etash 💻	Mentor Reka 💻	Flydexo 💻	Elias Tazartes 💻	greged93 💻	Harsh Bajpai 💻
ftupas 💻	Clément Walter 💻	johann bestowrous 💻	danilowhk 💻	Iris 💻	Aniket Prajapati 💻	Trunks @ Carbonable 💻
Alex Sumner 💻	Raphaël Deknop 💻	Bhavya Gosai 💻	apoorvsadana 💻	Paul-Henry Kajfasz 💻	Khaeljy 💻	Tristan 💻
glihm 💻	omahs 💻	valdo.carbonaboyz.stark 💻	Damián Piñones 💻	zarboq 💻	Santiago Galván (Dub) 💻	Oak 💻
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