Broker API

The Broker API is a standalone client that exposes Broker functionality via a JSON API interface.

Brokers need to run the client for the API themselves, as the Broker holds keys used to sign extrinsics and collect any fees set for Deposit Channels. The API client works by pointing it to an RPC node — also run by the same Broker, ideally.

Command line arguments and defaults

The state_chain.ws_endpoint should point at a synced Chainflip State Chain RPC node. The default is ws://localhost:9944assuming it is run locally.
The state_chain.signing_key_file should be the Broker's private key for their on-chain account. The account should be funded (opens in a new tab). The account type should be set to Broker. The default is /etc/chainflip/keys/signing_key_file.
The port is the port on which the Broker will listen for connections. Use 0 to assign a random port. The default is 80.

./chainflip-broker-api --help

chainflip-broker-api
 
USAGE:
    chainflip-broker-api [OPTIONS]
 
OPTIONS:
    -h, --help
            Print help information
 
        --port <PORT>
            The port number on which the broker will listen for connections. Use 0 to assing a
            random port. [default: 80]
 
        --state_chain.signing_key_file <SIGNING_KEY_FILE>
            A path to a file that contains the broker's secret key for signing extrinsics.
            [default: /etc/chainflip/keys/signing_key_file]
 
        --state_chain.ws_endpoint <WS_ENDPOINT>
            The state chain node's rpc endpoint. [default: ws://localhost:9944]
 
    -v, --version 
            Print the version of the API

RPC Methods

`broker_request_swap_deposit_address`

Parameters:

source_asset: Source asset.
destination_asset: Egress asset.
destination_address: Egress Address.
broker_commission_bps: Broker Commission in basis points (100th of a percent). Broker operators can choose to charge a fee for the use of their endpoint, and can be set at any value from 1 basis point to 1000 basis points.
channel_metadata: (Optional) Cross-chain message metadata as a JSON object: {"gas_budget": <amount>, "message":<hex_string>, "cf_parameters": <hex_string>}. Where message and cf_parameters are hex encoded strings.

Return:

deposit address.

`broker_register_account`

Parameters:

None

Return:

null if successful, otherwise an error.

Working Example

This example assumes the node that is exposing the Statechain RPC's is funded.

Open a terminal and run:

./chainflip-broker-api \
    --state_chain.ws_endpoint=ws://localhost:9944 \
    --state_chain.signing_key_file /path/to/my/signing_key \
    --port 62378 # or whatever port you want to use

It will print 🎙 Server is listening on 0.0.0.0:62378. and continue to run.

Open another terminal and run: Register as a broker if you are not already.

curl -H "Content-Type: application/json" \
    -d '{"id":1, "jsonrpc":"2.0", "method": "broker_register_account"}' \
    http://localhost:62378

Request a swap deposit address:

curl -H "Content-Type: application/json" \
    -d '{"id":1, "jsonrpc":"2.0", "method": "broker_request_swap_deposit_address", "params": ["ETH", "FLIP","0xabababababababababababababababababababab", 0]}' \
    http://localhost:62378

The result is the hex encoded deposit address, channel id, expiry block, and the issued block:

{
    "jsonrpc":"2.0",
    "result":{
        "address":"0xe720e23f62efc931d465a9d16ca303d72ad6c0bc",
        "issued_block":5418,
        "channel_id":6,
        "source_chain_expiry_block":2954
    },
    "id":1
}

Limitations

It doesn't seem to work with wss, so make sure the address is specified with ws. It should be ok since we're not going to expose this externally.

Reference

Assets

Assets are specified as a { chain, asset } object, where the chain is as described below, and the asset is an upper-case string.

Where the chain is unambiguous (for example for the native currencies), the asset can be submitted simply as the upper-case string.

For example, for BTC, "BTC" and { chain: "Bitcoin", asset: "BTC" } are both valid and resolve to the same asset.

Assets returned from the RPCs will always take the explicit form, for example { chain: "Ethereum", asset: "ETH" }

Chains

Chains are specified as the full name of the chain, capitalised, for example "Ethereum", "Bitcoin", "Polkadot".

Addresses

Addresses should be encoded according to their host chains:

Ethereum addresses should be encoded as Hex strings, for example "0xfa36e03defc6e4d140cc61fcaab9d1fbef18642f".
Polkadot addresses can be encoded using SS58 or Hex strings, for example: "13zyEWmmLDx63Y99TL9SkxBe1DqPVCrcjXytxM3ZHGRyEJV5" or "0x84aec0876dbb3cb7391eeded2eef5fbcf0d1a34f7c9f86f9af205f944b461761"
Bitcoin addresses should be encoded using the appropriate bitcoin standard for the address type. For example "tb1qw508d6qejxtdg4y5r3zarvary0c5xw7kxpjzsx" is a valid bech32 address on Bitcoin testnet.

Running a Broker Broker Working Example