Optimism Documentation

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 AvailableFor a complete working setup with all components, check out the automated approach 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.

Use docker
Build from source

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 VariablesThe 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!

To ensure you’re using the latest compatible versions of OP Stack components, always check the official releases page.Look for the latest op-batcher/v* release that’s compatible with your sequencer setup.

This guide uses op-batcher/v1.13.2 which is compatible with op-node/v1.13.3 and op-geth/v1.101511.1 from the sequencer setup. Always check the release notes for compatibility information.

Clone and build op-batcher

# If you don't already have the optimism repository from the sequencer setup
git clone https://github.com/ethereum-optimism/optimism.git
cd optimism

# Checkout the latest release tag
git checkout op-batcher/v1.13.2

# Build op-batcher
cd op-batcher
just

# Binary will be available at ./bin/op-batcher

Verify installation

Run this command to verify the installation:

./bin/op-batcher --version

Configuration setup

For advanced configuration options and fine-tuning your batcher, including:

Batch submission policies
Channel duration settings
Data availability types (blobs vs calldata)
Transaction throttling
Network timeouts

Check out the Batcher Configuration Reference. This will help you optimize your batcher’s performance and cost-efficiency.

Organize your workspace

Create your batcher working directory:

# Create batcher directory inside rollup
cd ../    # Go back to rollup directory
mkdir batcher
cd batcher

# Create scripts directory
mkdir scripts

Your final directory structure should look like:

rollup/
├── deployer/              # From previous step
│   └── .deployer/        # Contains state.json
├── optimism/             # Contains op-batcher binary
├── sequencer/           # From previous step
└── batcher/            # You are here
    ├── state.json      # Copied from deployer
    ├── .env           # Environment variables
    └── scripts/       # Startup scripts
  └── start-batcher.sh

Extract BatchInbox address

Extract the BatchInbox contract address from your op-deployer output:

# Make sure you're in the rollup/batcher directory
cd rollup/batcher

# Copy the deployment state file 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"

The batcher submits transaction batches to the BatchInbox contract on L1. This contract is responsible for accepting and storing L2 transaction data.

Set up environment variables

Create your .env file with the actual values:

# Create .env file with your actual values
# L1 Configuration - Replace with your actual RPC URL
L1_RPC_URL=https://sepolia.infura.io/v3/YOUR_ACTUAL_INFURA_KEY

# L2 Configuration - Should match your sequencer setup
      L2_RPC_URL=http://op-geth:8545
    ROLLUP_RPC_URL=http://op-node:8547

# Contract addresses - Extract from your op-deployer output
BATCH_INBOX_ADDRESS=YOUR_ACTUAL_BATCH_INBOX_ADDRESS

# Private key - Replace with your actual private key
BATCHER_PRIVATE_KEY=YOUR_ACTUAL_PRIVATE_KEY

# Batcher configuration
POLL_INTERVAL=1s
SUB_SAFETY_MARGIN=6
NUM_CONFIRMATIONS=1
SAFE_ABORT_NONCE_TOO_LOW_COUNT=3
RESUBMISSION_TIMEOUT=30s
MAX_CHANNEL_DURATION=25

# RPC configuration
BATCHER_RPC_PORT=8548

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

Get your private key

Get a private key from your wallet that will be used for submitting batches to L1. This account needs sufficient ETH to pay for L1 gas costs.

The batcher account needs to be funded with ETH on L1 to pay for batch submission transactions. Monitor this account’s balance regularly as it will consume ETH for each batch submission.

Batcher configuration

Create scripts/start-batcher.sh in the same directory:

#!/bin/bash

source .env

# Path to the op-batcher binary we built
../../optimism/op-batcher/bin/op-batcher \
  --l2-eth-rpc=$L2_RPC_URL \
  --rollup-rpc=$ROLLUP_RPC_URL \
  --poll-interval=$POLL_INTERVAL \
  --sub-safety-margin=$SUB_SAFETY_MARGIN \
  --num-confirmations=$NUM_CONFIRMATIONS \
  --safe-abort-nonce-too-low-count=$SAFE_ABORT_NONCE_TOO_LOW_COUNT \
  --resubmission-timeout=$RESUBMISSION_TIMEOUT \
  --rpc.addr=0.0.0.0 \
  --rpc.port=$BATCHER_RPC_PORT \
  --rpc.enable-admin \
  --max-channel-duration=$MAX_CHANNEL_DURATION \
  --l1-eth-rpc=$L1_RPC_URL \
  --private-key=$BATCHER_PRIVATE_KEY \
  --batch-type=1 \
  --data-availability-type=blobs \
  --log.level=info

Batcher parameters explained

--poll-interval: How frequently the batcher checks for new L2 blocks to batch
--sub-safety-margin: Number of confirmations to wait before considering L1 transactions safe
--max-channel-duration: Maximum time (in L1 blocks) to keep a channel open
--batch-type: Type of batch encoding (1 for span batches, 0 for singular batches)
--data-availability-type: Whether to use blobs or calldata for data availability

Starting the batcher

Start the batcher

# Make the script executable
chmod +x scripts/start-batcher.sh

# Start the batcher
./scripts/start-batcher.sh

For detailed cost analysis and optimization strategies, refer to the Transaction fees documentation.

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

Understanding common startup messagesWhen 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 →

Next: Configure and start op-proposer to submit L2 state roots to L1 for withdrawal verification.

Need Help?

Monitoring Guide: Chain Monitoring

​Understanding the batcher’s role

​Prerequisites

​Batcher configuration

​Batcher parameters explained

​Starting the batcher

​Start the batcher

​What’s Next?

Spin up proposer →

​Need Help?

Understanding the batcher’s role

Prerequisites

Batcher configuration

Batcher parameters explained

Starting the batcher

Start the batcher

What’s Next?

Need Help?