Using Celestia as DA

🌞 Introduction

This tutorial serves as a comprehensive guide for deploying your rollup on Celestia's data availability (DA) network. From the Rollkit perspective, there's no difference in posting blocks to Celestia's testnets or Mainnet Beta.

Before proceeding, ensure that you have completed the quick start tutorial, which covers installing the rollkit CLI and running a rollup against a local DA network.

🪶 Running a Celestia light node

Before you can start your rollup node, you need to initiate, sync, and fund a light node on one of Celestia's networks:

• Arabica Devnet
• Mocha Testnet
• Mainnet Beta

The main difference lies in how you fund your wallet address: using testnet TIA or TIA for Mainnet Beta.

After successfully starting a light node, it's time to start posting the batches of blocks of data that your rollup generates to Celestia.

🏗️ Prerequisites

• rollkit CLI installed from the quick start tutorial.

🛠️ Configuring flags for DA

Now that we are posting to the Celestia DA instead of the local DA, the rollkit start command requires three DA configuration flags:

• --rollkit.da_start_height
• --rollkit.da_auth_token
• --rollkit.da_namespace

TIP

Optionally, you could also set the --rollkit.da_block_time flag. This should be set to the finality time of the DA layer, not its actual block time, as Rollkit does not handle reorganization logic. The default value is 15 seconds.

Let's determine which values to provide for each of them.

First, let's query the DA layer start height using our light node.

DA_BLOCK_HEIGHT=$(celestia header network-head | jq -r '.result.header.height')
echo -e "\n Your DA_BLOCK_HEIGHT is $DA_BLOCK_HEIGHT \n"

The output of the command above will look similar to this:

 Your DA_BLOCK_HEIGHT is 2127672

Now, let's obtain the authentication token of your light node using the following command:

Arabica Devnet

AUTH_TOKEN=$(celestia light auth write --p2p.network arabica)
echo -e "\n Your DA AUTH_TOKEN is $AUTH_TOKEN \n"

Mocha Testnet

AUTH_TOKEN=$(celestia light auth write --p2p.network mocha)
echo -e "\n Your DA AUTH_TOKEN is $AUTH_TOKEN \n"

Mainnet Beta

AUTH_TOKEN=$(celestia light auth write)
echo -e "\n Your DA AUTH_TOKEN is $AUTH_TOKEN \n"

The output of the command above will look similar to this:

 Your DA AUTH_TOKEN is eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJBbGxvdyI6WyJwdWJsaWMiLCJyZWFkIiwid3JpdGUiXX0.cSrJjpfUdTNFtzGho69V0D_8kyECn9Mzv8ghJSpKRDE

Next, let's set up the namespace to be used for posting data on Celestia:

DA_NAMESPACE=00000000000000000000000000000000000000000008e5f679bf7116cb

TIP

00000000000000000000000000000000000000000008e5f679bf7116cb is a default namespace for Mocha testnet. You can set your own by using a command similar to this (or, you could get creative 😎):

openssl rand -hex 10

Replace the last 20 characters (10 bytes) in 00000000000000000000000000000000000000000008e5f679bf7116cb with the newly generated 10 bytes.

Learn more about namespaces.

Lastly, set your DA address for your light node, which by default runs at port 26658:

DA_ADDRESS=http://localhost:26658

🔥 Running your rollup connected to Celestia light node

Finally, let's initiate the rollup node with all the flags:

rollkit start \
    --rollkit.aggregator \
    --rollkit.da_auth_token $AUTH_TOKEN \
    --rollkit.da_namespace $DA_NAMESPACE \
    --rollkit.da_start_height $DA_BLOCK_HEIGHT \
    --rollkit.da_address $DA_ADDRESS

Now, the rollup is running and posting blocks (aggregated in batches) to Celestia. You can view your rollup by using your namespace or account on one of Celestia's block explorers.

For example, here on Celenium for Arabica.

Other explorers:

• Arabica testnet
• Mocha testnet
• Mainnet Beta

🎉 Next steps

Congratulations! You've built a local rollup that posts data to Celestia's DA layer. Well done! Now, go forth and build something great! Good luck!