Cumulus

A set of tools for writing Polkadot parachains that are based on Substrate.

It's easy to write blockchains using Substrate, and the overhead of writing parachains' distribution, p2p, database, and synchronization layers is generally high and should be reusable. 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 and are up in the air, like this project (as it is an initial prototype -- expect a rename when it gets cooler.)

cumulus-consensus

For now, this is only project contained in this repo. cumulus-consensus is a consensus engine for Substrate which 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.

cumulus-runtime

A planned wrapper around substrate runtimes to turn them into parachain validation code and to provide proof-generation routines.

cumulus-collator

A planned Polkadot collator for the parachain.

Running a collator

1. Checkout polkadot at bkchr-cumulus-branch.

2. Run Alice and Bob:

   cargo run --release -- --chain=${CUMULUS_REPO}/test/parachain/res/polkadot_chainspec.json --base-path=cumulus_relay_chain_node_0 --alice

   cargo run --release -- --chain=${CUMULUS_REPO}/test/parachain/res/polkadot_chainspec.json --base-path=cumulus_relay_chain_node_1 --bob --port 50666

   Where CUMULUS_REPO is the path to the checkout of Cumulus.

3. Switch back to this repository and generate the parachain genesis state:

   cargo run --release -p cumulus-test-parachain-collator -- export-genesis-state genesis-state

4. Run the collator:

   cargo run --release -p cumulus-test-parachain-collator -- --base-path cumulus_collator_path -- --bootnodes=/ip4/127.0.0.1/tcp/30333/p2p/PEER_ID_${NAME} --bootnodes=/ip4/127.0.0.1/tcp/50666/p2p/PEER_ID_${NAME}

   PEER_ID_${NAME} needs to be replaced with the peer id of the polkadot validator that uses ${NAME} as authority. The -- after --base-path cumulus_collator_path is important, it tells the CLI to pass these arguments to the relay chain node that is running inside of the collator.

5. Open https://polkadot.js.org/apps/#/sudo and register the parachain by calling Registrar > RegisterPara

   id: 100

   ParaInfo: Always

   code: CUMULUS_REPO/target/release/wbuild/cumulus-test-parachain-runtime/cumulus_test_parachain_runtime.compact.wasm

   initial_head_data: Use the file you generated in step 3. (name: genesis-state)

   Now your parachain should be registered and the collator should start building blocks and sending them to the relay chain.

6. Now the collator should build blocks and the relay-chain should include them. You can check that the parachain-header for parachain 100 is changing.