jasl / cumulus

Write Parachains on Substrate

Cumulus ☁️

This repository contains both the Cumulus SDK and also specific chains implemented on top of this SDK.

Cumulus SDK

A set of tools for writing Substrate-based Polkadot parachains. Refer to the included overview for architectural details, and the Cumulus tutorial for a guided walk-through of using these tools.

It's easy to write blockchains using Substrate, and the overhead of writing parachains' distribution, p2p, database, and synchronization layers should be just as low. This project aims to make it easy to write parachains for Polkadot by leveraging the power of Substrate.

Cumulus clouds are shaped sort of like dots; together they form a system that is intricate, beautiful and functional.

Consensus

parachain-consensus is a consensus engine for Substrate that follows a Polkadot relay chain. This will run a Polkadot node internally, and dictate to the client and synchronization algorithms which chain to follow, finalize, and treat as best.

Collator

A Polkadot collator for the parachain is implemented by the polkadot-parachain binary (previously called polkadot-collator).

Statemint 🪙

This repository also contains the Statemint runtime (as well as the canary runtime Statemine and the test runtime Westmint). Statemint is a common good parachain providing an asset store for the Polkadot ecosystem.

Build & Launch a Node

To run a Statemine or Westmint node (Statemint is not deployed, yet) you will need to compile the polkadot-parachain binary:

cargo build --release --locked -p polkadot-parachain

Once the executable is built, launch the parachain node via:

CHAIN=westmint # or statemine
./target/release/polkadot-parachain --chain $CHAIN

Refer to the setup instructions below to run a local network for development.

Contracts 📝

See the contracts-rococo readme for details.

Rococo 👑

Rococo is becoming a Community Parachain Testbed for parachain teams in the Polkadot ecosystem. It supports multiple parachains with the differentiation of long-term connections and recurring short-term connections, to see which parachains are currently connected and how long they will be connected for see here.

Rococo is an elaborate style of design and the name describes the painstaking effort that has gone into this project.

Build & Launch Rococo Collators

Collators are similar to validators in the relay chain. These nodes build the blocks that will eventually be included by the relay chain for a parachain.

To run a Rococo collator you will need to compile the following binary:

cargo build --release --locked -p polkadot-parachain

Otherwise you can compile it with Parity CI docker image:

docker run --rm -it -w /shellhere/cumulus \
                    -v $(pwd):/shellhere/cumulus \
                    paritytech/ci-linux:production cargo build --release --locked -p polkadot-parachain
sudo chown -R $(id -u):$(id -g) target/

If you want to reproduce other steps of CI process you can use the following guide.

Once the executable is built, launch collators for each parachain (repeat once each for chain tick, trick, track):

./target/release/polkadot-parachain --chain $CHAIN --validator

Parachains

• Statemint
• Contracts on Rococo
• RILT

The network uses horizontal message passing (HRMP) to enable communication between parachains and the relay chain and, in turn, between parachains. This means that every message is sent to the relay chain, and from the relay chain to its destination parachain.

Local Setup

Launch a local setup including a Relay Chain and a Parachain.

Launch the Relay Chain

# Clone
git clone https://github.com/paritytech/polkadot
cd polkadot

# Compile Polkadot with the real overseer feature
cargo build --release

# Generate a raw chain spec
./target/release/polkadot build-spec --chain rococo-local --disable-default-bootnode --raw > rococo-local-cfde.json

# Alice
./target/release/polkadot --chain rococo-local-cfde.json --alice --tmp

# Bob (In a separate terminal)
./target/release/polkadot --chain rococo-local-cfde.json --bob --tmp --port 30334

Launch the Parachain

# Clone
git clone https://github.com/paritytech/cumulus
cd cumulus

# Compile
cargo build --release

# Export genesis state
./target/release/polkadot-parachain export-genesis-state > genesis-state

# Export genesis wasm
./target/release/polkadot-parachain export-genesis-wasm > genesis-wasm

# Collator1
./target/release/polkadot-parachain --collator --alice --force-authoring --tmp --port 40335 --ws-port 9946 -- --execution wasm --chain ../polkadot/rococo-local-cfde.json --port 30335

# Collator2
./target/release/polkadot-parachain --collator --bob --force-authoring --tmp --port 40336 --ws-port 9947 -- --execution wasm --chain ../polkadot/rococo-local-cfde.json --port 30336

# Parachain Full Node 1
./target/release/polkadot-parachain --tmp --port 40337 --ws-port 9948 -- --execution wasm --chain ../polkadot/rococo-local-cfde.json --port 30337

Register the parachain

Containerize

After building polkadot-parachain with cargo or with Parity CI image as documented in this chapter, the following will allow producing a new docker image where the compiled binary is injected:

./docker/scripts/build-injected-image.sh

Alternatively, you can build an image with a builder pattern:

docker build --tag $OWNER/$IMAGE_NAME --file ./docker/polkadot-parachain_builder.Containerfile .

You may then run your new container:

```bash
docker run --rm -it $OWNER/$IMAGE_NAME --collator --tmp --execution wasm --chain /specs/westmint.json