Getting with a Celestia Lottery rollup

Learn celestia (https://docs.celestia.org/concepts/how-celestia-works/introduction/) and its rollup (https://blog.celestia.org/sovereign-rollup-chains/)

introduction

We are going to demo a dAPP (Lottery) deployed on a local ethermintd integrated with rollkit (https://rollkit.dev/docs/intro/). Blocks will be submitted to the Celesia DA layer via a local light node connected to the blockspace race.

A working version running on BSR as of 13th May 2023 is available here : http://celestia-rollup-lottery.pops.one:3000/

Requirements

• Foundry
• Celestia fork ethermind https://github.com/celestiaorg/ethermint.git
• rollkit https://rollkit.dev/docs/intro/
• nodejs v14.x, npm, reactjs
• metamask

Build your light node

There are many guide out there and a good place to start building your light node is to follow the blockspace race incentivized testnet (ITN) tasks https://docs.celestia.org/nodes/itn-deploy-light/

Do not forget to fund the account used by the light node

Run your local Ethermintd/rollkit

install golang v1.19.1

ver="1.19.1" 
cd $HOME 
wget "https://golang.org/dl/go$ver.linux-amd64.tar.gz" 
sudo rm -rf /usr/local/go 
sudo tar -C /usr/local -xzf "go$ver.linux-amd64.tar.gz" 
rm "go$ver.linux-amd64.tar.gz"
echo "export PATH=$PATH:/usr/local/go/bin:$HOME/go/bin" >> $HOME/.profile
source $HOME/.bashrc

Install Ethermintd/rollkit

git clone https://github.com/celestiaorg/ethermint.git
cd ethermint
make install

Run it !

# init your local blockchain
bash init.sh

# generate
RPC=https://rpc-blockspacerace.pops.one
NAMESPACE_ID=$(openssl rand -hex 8)
DA_BLOCK_HEIGHT=$(curl $RPC/block | jq -r '.result.block.header.height')

# start local ethermint
ethermintd start --rollkit.aggregator true --rollkit.da_layer celestia --rollkit.da_config='{"base_url":"http://localhost:26659","timeout":60000000000,"gas_limit":6000000,"fee":6000}' --rollkit.namespace_id $NAMESPACE_ID --rollkit.da_start_height $DA_BLOCK_HEIGHT 

Do not forget to fund the account used by the light node

You will the below error message if you haven't

9:26AM ERR DA layer submission failed error="rpc error: code = NotFound desc = account celestia14x0uurpx4gqcelp7tc28lp43sw5u9mr5tkfted not found" attempt=1 module=BlockManager

Deploy your lottery contract

Install foundry

curl -L https://foundry.paradigm.xyz | bash
source ~/.bashrc
foundryup 

Extract the private key

PRIVATE_KEY=$(ethermintd keys unsafe-export-eth-key mykey --keyring-backend test)

The key will be used to deploy the contract

Deploy the contract

cd $HOME
git clone https://github.com/P-OPSTeam/Celestia-rollup-Lottery.git
cd Celestia-rollup-Lottery
forge install foundry-rs/forge-std
# ignore the error with lib The following paths are ignored by one of your .gitignore files: lib
forge script script/Lottery.s.sol:ContractScript --rpc-url http://localhost:8545 --private-key $PRIVATE_KEY --broadcast

Copy the contrat address

CONTRACT_ADDRESS=<contract_address from previous output>

Test the contract

cast call $CONTRACT_ADDRESS "ticketMax()" --rpc-url http://localhost:8545
0x0000000000000000000000000000000000000000000000000000000000000019

0x19 is 25 in decimal

Build the frontend

install the dependencies of project

# install nodejs 14.x
curl -sL https://deb.nodesource.com/setup_14.x | sudo bash -
sudo apt update
sudo apt -y install nodejs

# check node version
node  -v

# install project dependencies
npm install

replace the contract address with yours

sed -i -e "s/0x7950626960596b0fbdd66381a5e88c6b5b7a0849/$CONTRACT_ADDRESS/g" src/config.js

Update contract manifest

if you updated and build a different contract you will need to copy the new contract manifest

cp out/Lottery.s.sol/Lottery.sol src/

else you can skip this part

run the frontend

npm run start

Metamask network configuration

you will need to add a custom network pointing to your own ethermintd/rollit RPC endpoint

• Network Name : My Ethermintd
• New RPC URL : http://<yourip>:8545
• Chain ID : 9000
• Currency symbol : TEVMOS

You can now import the $PRIVATE_KEY into metamask.

For testing, create another account and transfer EVMOS to that new account !!

Enjoy !!

Troubleshooting

For an unknown reason, it seems the first purchase can't be done via the webUI, however using command line seems to fix it

cast send $CONTRACT_ADDRESS "buyTicket(uint16)" 2 --rpc-url http://localhost:8545 --private-key $PRIVATE_KEY_USR --value 5000000000000000000

And subsequent purchase via UI works well !

Credits

Thanks to Nagaganesh Jaladanki .