Blockchain Connection String

Blockchain connection string is a way to pass connection information to a light-weight blockchain provider in a single string akin to database connection string.

Specification

It is common to connect to blockchain node via API. With it come the following considerations:

1. There are multiple blockchains, which is important for blockchain-agnostic applications.
2. There are multiple transports: HTTP OpenRPC, WebSocket OpenRPC, gRPC, GraphQL.
3. A transport might require its own set of additional properties, e.g. bearer token for Infura.
4. Often an application requires different providers or transports based on environment: HTTP provider with private key while developing, WebSocket provider while in production.
5. Often API endpoint comes as an environment variable as per The Twelve Factor App.

Often selection of blockchain connection mechanism is re-invented for every app. We strive to solve this by providing a universal connection string format, based on which an application could deterministically select an appropriate provider.

Blockchain connection string is based on URL specification defined in RFC 3986. The goal of blockchain connection string is to unify blockchain API connection across:

• different blockchains,
• different messaging protocols,
• different transport protocols,
• different key material.

Blockchain part helps to select appropriate connector in a blockchain-agnostic application. Transport and messaging protocols are present here separately to avoid ambiguity. GraphQL and OpenRPC messages could be transmitted over HTTP and WebSocket transports both.

Syntax

blockchain_connection_string = scheme ":" endpoint [ "?" options ]
scheme = known-transport | chain "+" messaging "+" transport
chain = scheme-part
transport = scheme-part
messaging = scheme-part
scheme-part = ALPHA *( ALPHA / DIGIT / "-" / "." )
endpoint = hier-part
options = query
known-transport = "http" | "https" | "ws" | "wss"

See RFC 3986 for definitions of hier-part and query.

Semantics

Each connection string starts with scheme, which contains three parts, separated by + sign:

• chain identifies blockchain family, like eip155, bip122, cosmos, lip9, polkadot.
• transport represents transport protocol, like grpc, http, or ws,
• messaging represents messaging protocol, like graphql, openrpc.

To maintain compatibility with currently used HTTP API endpoints, known transport protocols could be used instead of full scheme.

endpoint is a usual host-port pair. options are connection-specific pairs of key-value elements, as in URL query.

Test Cases

Manually composed examples are below:

# Ethereum OpenRPC connection to Infura via HTTPS, read only
eip155+openrpc+https://mainnet.infura.io/
eip155+openrpc+https://mainnet.infura.io/

# Ethereum OpenRPC connection to Infura via WebSocket, using key material for signing
eip155+openrpc+wss://mainnet.infura.io?mnemonic=enemy boat gauge orphan column malbolge prepare cave only first limb garlic&path=m/44'/60'/0'/0/0

Usage

const connectionString = ConnectionString.build(`eip155+openrpc+https://mainnet.infura.io/?mnemonic=enemy boat gauge orphan column malbolge prepare cave only first limb garlic&path=m/44'/60'/0'/0/0`)
connectionString.chain #= eip155
connectionString.messagingProtocol #= openrpc
connectionString.transportProtocol #= https
connectionString.transport #= https://mainnet.infura.io/
connectionString.options #= {mnemonic: "enemy boat gauge orphan column malbolge prepare cave only first limb garlic", path: "m/44'/60'/0'/0/0"}