Substrate Node Template

A new FRAME-based Substrate node, ready for hacking 🚀

Local Development

Follow these steps to prepare a local Substrate development environment 🛠️

Setup

Setup instructions can be found at the
Substrate Developer Hub.

Build

Once the development environment is set up, build the node template. This command will build the
Wasm and
native code:

WASM_BUILD_TOOLCHAIN=nightly-2020-10-05 cargo build --release

Run

Single Node Development Chain

Purge any existing dev chain state:

./target/release/node-template purge-chain --dev

Start a dev chain:

./target/release/node-template --dev

Or, start a dev chain with detailed logging:

RUST_LOG=debug RUST_BACKTRACE=1 ./target/release/node-template -lruntime=debug --dev

Multi-Node Local Testnet

If you want to see the multi-node consensus algorithm in action, refer to
our Start a Private Network tutorial.

Template Structure

A Substrate project such as this consists of a number of components that are spread across a few
directories.

Node

A blockchain node is an application that allows users to participate in a blockchain network.
Substrate-based blockchain nodes expose a number of capabilities:

• Networking: Substrate nodes use the libp2p networking stack to allow the
  nodes in the network to communicate with one another.
• Consensus: Blockchains must have a way to come to
  consensus on the state of the
  network. Substrate makes it possible to supply custom consensus engines and also ships with
  several consensus mechanisms that have been built on top of
  Web3 Foundation research.
• RPC Server: A remote procedure call (RPC) server is used to interact with Substrate nodes.

There are several files in the node directory - take special note of the following:

• chain_spec.rs: A
  chain specification is a
  source code file that defines a Substrate chain's initial (genesis) state. Chain specifications
  are useful for development and testing, and critical when architecting the launch of a
  production chain. Take note of the development_config and testnet_genesis functions, which
  are used to define the genesis state for the local development chain configuration. These
  functions identify some
  well-known accounts
  and use them to configure the blockchain's initial state.
• service.rs: This file defines the node implementation. Take note of
  the libraries that this file imports and the names of the functions it invokes. In particular,
  there are references to consensus-related topics, such as the
  longest chain rule,
  the Aura block authoring
  mechanism and the
  GRANDPA finality
  gadget.

After the node has been built, refer to the embedded documentation to learn more about the
capabilities and configuration parameters that it exposes:

./target/release/node-template --help

Runtime

In Substrate, the terms
"runtime" and
"state transition function"
are analogous - they refer to the core logic of the blockchain that is responsible for validating
blocks and executing the state changes they define. The Substrate project in this repository uses
the FRAME framework to construct a
blockchain runtime. FRAME allows runtime developers to declare domain-specific logic in modules
called "pallets". At the heart of FRAME is a helpful
macro language that makes it easy to
create pallets and flexibly compose them to create blockchains that can address
a variety of needs.

Review the FRAME runtime implementation included in this template and note
the following:

• This file configures several pallets to include in the runtime. Each pallet configuration is
  defined by a code block that begins with impl $PALLET_NAME::Trait for Runtime.
• The pallets are composed into a single runtime by way of the
  construct_runtime!
  macro, which is part of the core
  FRAME Support
  library.

Pallets

The runtime in this project is constructed using many FRAME pallets that ship with the
core Substrate repository and a
template pallet that is defined in the pallets directory.

A FRAME pallet is compromised of a number of blockchain primitives:

• Storage: FRAME defines a rich set of powerful
  storage abstractions that makes
  it easy to use Substrate's efficient key-value database to manage the evolving state of a
  blockchain.
• Dispatchables: FRAME pallets define special types of functions that can be invoked (dispatched)
  from outside of the runtime in order to update its state.
• Events: Substrate uses events to
  notify users of important changes in the runtime.
• Errors: When a dispatchable fails, it returns an error.
• Trait: The Trait configuration interface is used to define the types and parameters upon which
  a FRAME pallet depends.

Run in Docker

First, install Docker and
Docker Compose.

Then run the following command to start a single node development chain.

./scripts/docker_run.sh

This command will firstly compile your code, and then start a local development network. You can
also replace the default command (cargo build --release && ./target/release/node-template --dev --ws-external)
by appending your own. A few useful ones are as follow.

# Run Substrate node without re-compiling
./scripts/docker_run.sh ./target/release/node-template --dev --ws-external

# Purge the local dev chain
./scripts/docker_run.sh ./target/release/node-template purge-chain --dev

# Check whether the code is compilable
./scripts/docker_run.sh cargo check