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C-Chain Exchange Integration

Overview​

The objective of this document is to provide a brief overview of how to integrate with the EVM-Compatible Metal C-Chain. For teams that already support ETH, supporting the C-Chain is as straightforward as spinning up an Metal node (which has the same API as go-ethereum) and populating Metal’s ChainID (381931) when constructing transactions.

Additionally, Metallicus maintains an implementation of the Rosetta API for the C-Chain called metal-rosetta. You can learn more about this standardized integration path on the attached Rosetta API website.

Integration Using EVM Endpoints​

Running a Metal Blockchain Node​

If you want to build your node form source or include it in a docker image, reference the MetalGo GitHub repository. To quickly get up and running, you can use the node installation script that automates installing and updating MetalGo node as a systemd service on Linux, using prebuilt binaries.

Configuring a Metal Blockchain Node​

All configuration options and their default values are described here.

You can supply configuration options on the command line, or use a config file, which can be easier to work with when supplying many options. You can specify the config file location with —config-file=config.json, where config.json is a JSON file whose keys and values are option names and values.

Individual chains, including the C-Chain, have their own configuration options which are separate from the node-level options. These can also be specified in a config file. For more details, see here.

The C-Chain config file should be at $HOME/.metalgo/configs/chains/C/config.json. You can also tell MetalGo to look somewhere else for the C-Chain config file with option --chain-config-dir. An example C-Chain config file:

caution

If you need Ethereum Archive Node functionality, you need to disable C-Chain pruning, which has been enabled by default since MetalGo v1.4.10. To disable pruning, include "pruning-enabled": false in the C-Chain config file as shown below.

{
  "snowman-api-enabled": false,
  "coreth-admin-api-enabled": false,
  "local-txs-enabled": true,
  "pruning-enabled": false,
  "eth-apis": [
    "internal-eth",
    "internal-blockchain",
    "internal-transaction",
    "internal-tx-pool",
    "internal-account",
    "internal-personal",
    "debug-tracer",
    "web3",
    "eth",
    "eth-filter",
    "admin",
    "net"
  ]
}

Interacting with the C-Chain​

Interacting with the C-Chain is identical to interacting with go-ethereum. You can find the reference material for C-Chain API here.

Please note that personal_ namespace is turned off by default. To turn it on, you need to pass the appropriate command line switch to your node, like in the above config example.

Integration Using Rosetta​

Rosetta is an open-source specification and set of tools that makes integrating with different blockchain networks easier by presenting the same set of APIs for every network. The Rosetta API is made up of 2 core components, the Data API and the Construction API. Together, these APIs allow for anyone to read and write to blockchains in a standard format over a standard communication protocol. The specifications for these APIs can be found in the rosetta-specifications repository.

You can find the Rosetta server implementation for Metal C-Chain here, all you need to do is install and run the server with proper configuration. It comes with a Dockerfile that packages both the server and the Metal client. Detailed instructions can be found in the linked repository.

Constructing Transactions​

Metal C-Chain transactions are identical to standard EVM transactions with 2 exceptions:

  • They must be signed with Metal’s ChainID (381931).
  • The detailed dynamic gas fee can be found here.

For development purposes, Metal supports all the popular tooling for Ethereum, so developers familiar with Ethereum and Solidity can feel right at home. We have tutorials and repositories for several popular development environments:

Ingesting On-Chain Data​

You can use any standard way of ingesting on-chain data you use for Ethereum network.

Determining Finality​

Avalanche consensus, implemented on the Metal Blockchain, provides fast and irreversible finality with 1-2 seconds. To query the most up-to-date finalized block, query any value (that is block, balance, state, etc) with the latest parameter. If you query above the last finalized block (that is eth_blockNumber returns 10 and you query 11), an error will be thrown indicating that unfinalized data cannot be queried (as of metalgo@v1.3.2).

(Optional) Custom Golang SDK​

If you plan on extracting data from the C-Chain into your own systems using Golang, we recommend using our custom ethclient. The standard go-ethereum Ethereum client does not compute block hashes correctly (when you call block.Hash()) because it doesn't take into account the added ExtDataHash header field in Metal C-Chain blocks, which is used move METAL between chains (X-Chain and P-Chain).

If you plan on reading JSON responses directly or use web3.js (doesn't recompute hash received over the wire) to extract on-chain transaction data/logs/receipts, you shouldn't have any issues!

Support​

If you have any problems or questions, reach out either directly to our developers, or on our public Telegram server.