Spin up batcher

After you have spun up your sequencer, you need to configure a batcher to submit L2 transaction batches to L1.

Step 3 of 5: This tutorial is designed to be followed step-by-step. Each step builds on the previous one.

Automated Setup Available

For a complete working setup with all components, check out the automated approach (opens in a new tab) in the code directory.

Understanding the batcher's role

The batcher (op-batcher) serves as a crucial component that bridges your L2 chain data to L1. Its primary responsibilities include:

Batch submission: Collecting L2 transactions and submitting them as batches to L1
Data availability: Ensuring L2 transaction data is available on L1 for verification
Cost optimization: Compressing and efficiently packing transaction data to minimize L1 costs
Channel management: Managing data channels for optimal batch submission timing

The batcher reads transaction data from your sequencer and submits compressed batches to the BatchInbox contract on L1.

Prerequisites

Before setting up your batcher, ensure you have:

Running infrastructure:

An operational sequencer node
Access to a L1 RPC endpoint

Network information:

Your L2 chain ID and network configuration
L1 network details (chain ID, RPC endpoints)
BatchInbox contract address from your deployment

For setting up the batcher, we recommend using Docker as it provides a consistent and isolated environment. Building from source is also available for more advanced users.

If you prefer containerized deployment, you can use the official Docker images and do the following:

Set up directory structure and copy configuration files

# Create your batcher directory inside rollup
cd ../    # Go back to rollup directory if you're in sequencer
mkdir batcher
cd batcher
 
# Copy configuration files from deployer
cp ../deployer/.deployer/state.json .
 
# Extract the BatchInbox address
BATCH_INBOX_ADDRESS=$(cat state.json | jq -r '.opChainDeployments[0].systemConfigProxyAddress')
echo "BatchInbox Address: $BATCH_INBOX_ADDRESS"

Create environment variables file

OP Stack Standard Variables

The batcher uses OP Stack standard environment variables following the OP Stack conventions. These are prefixed with OP_BATCHER_ for batcher-specific settings.

# Create .env file with your actual values
cat > .env << 'EOF'
# L1 Configuration - Replace with your actual RPC URLs
OP_BATCHER_L1_RPC_URL=https://sepolia.infura.io/v3/YOUR_ACTUAL_INFURA_KEY
# Private key - Replace with your actual private key
OP_BATCHER_PRIVATE_KEY=YOUR_ACTUAL_PRIVATE_KEY
 
# L2 Configuration - Should match your sequencer setup
OP_BATCHER_L2_ETH_RPC=http://op-geth:8545
OP_BATCHER_ROLLUP_RPC=http://op-node:8547
 
# Contract addresses - Extract from your op-deployer output
OP_BATCHER_BATCH_INBOX_ADDR=YOUR_ACTUAL_BATCH_INBOX_ADDRESS
 
# Batcher configuration
OP_BATCHER_POLL_INTERVAL=1s
OP_BATCHER_SUB_SAFETY_MARGIN=6
OP_BATCHER_NUM_CONFIRMATIONS=1
OP_BATCHER_SAFE_ABORT_NONCE_TOO_LOW_COUNT=3
OP_BATCHER_MAX_CHANNEL_DURATION=1
OP_BATCHER_DATA_AVAILABILITY_TYPE=calldata
 
# RPC configuration
OP_BATCHER_RPC_PORT=8548
EOF

Important: Replace ALL placeholder values (YOUR_ACTUAL_*) with your real configuration values.

Create a docker-compose.yml file

This configuration assumes your sequencer is running in a Docker container named sequencer-node on the same op-stack network. Make sure your sequencer is running before starting the batcher.

 
services:
  op-batcher:
    image: us-docker.pkg.dev/oplabs-tools-artifacts/images/op-batcher:v1.13.2
    volumes:
      - .:/workspace
    working_dir: /workspace
    ports:
      - "8548:8548"
    env_file:
      - .env
    networks:
      - sequencer-node_default
    command: >
      op-batcher
      --rpc.addr=0.0.0.0
      --rpc.enable-admin
      --resubmission-timeout=30s
      --log.level=info
      --log.format=json
    restart: unless-stopped
 
networks:
  sequencer-node_default:
    external: false

Start the batcher service

# Make sure your sequencer network exists
# Start the batcher
docker-compose up -d
 
# View logs
docker-compose logs -f op-batcher

Verify batcher is running

# Check container status
docker-compose ps

Final directory structure

rollup/
├── deployer/            # From previous step
│   └── .deployer/      # Contains genesis.json and rollup.json
├── sequencer/          # From previous step
└── batcher/           # You are here
    ├── state.json     # Copied from deployer
    ├── .env           # Environment variables
    └── docker-compose.yml # Docker configuration

Your batcher is now operational and will continuously submit L2 transaction batches to L1!

Understanding common startup messages

When starting your batcher, you might see various log messages:

Added L2 block to local state: Normal operation, shows the batcher processing blocks
SetMaxDASize RPC method unavailable: Expected if the op-geth version used doesn't support this method.
context canceled errors during shutdown: Normal cleanup messages
Failed to query L1 tip: Can occur during graceful shutdowns

Most of these messages are part of normal operation. For detailed explanations of configuration options and troubleshooting, see the Batcher configuration reference.

What's Next?

Excellent! Your batcher is publishing transaction data to L1. The next step is to set up the proposer to submit state root proposals.

Spin up proposer →

Need Help?

Community Support: Join the Optimism Discord (opens in a new tab)
Batcher Configuration: op-batcher Configuration Reference
Monitoring Guide: Chain Monitoring