Run an Indexer

Indexers are the first step in the cross-chain flow. They monitor for cross-chain transfer events, verify proofs, and relay user assets to the user's Smart Account on the destination chain.

What Indexers Do

1. MONITOR SOURCE CHAIN
   └── Watch for burn events (TokenMessenger.DepositForBurn)

2. WAIT FOR ATTESTATION
   └── Verify cross-chain proof

3. RECEIVE ASSETS
   └── Deliver assets to user's Smart Account on destination chain

4. EARN FEE
   └── Indexer fee paid when message is indexed

Requirements

Requirement	Minimum	Recommended
CPU	2 cores	4 cores
RAM	2 GB	4 GB
Storage	10 GB	20 GB
Network	10 Mbps	100 Mbps
ETH (destination)	0.1 ETH	0.5 ETH

Quick Start

1. Clone Repository

git clone https://github.com/pons-network/resolver
cd resolver
npm install

2. Configure Environment

cp .env.example .env

Edit .env:

# Mode
OPERATOR_MODE=indexer

# Wallet (NEVER use your main wallet)
PRIVATE_KEY=your_private_key_here

# Chain Configuration (Sepolia → Arc Testnet)
SOURCE_CHAIN_ID=11155111
DESTINATION_CHAIN_ID=88991

# RPC Endpoints
SOURCE_RPC_URL=https://eth-sepolia.g.alchemy.com/v2/YOUR_KEY
DESTINATION_RPC_URL=https://rpc.testnet.arc.network

# Fee Configuration
MIN_INDEXER_FEE=100000    # Minimum fee to process (in token units)

3. Run Indexer

# Development
npm run start -- --mode indexer

# Production (with PM2)
pm2 start npm --name "pons-indexer" -- run start -- --mode indexer

# Docker
docker-compose up -d indexer

Configuration Reference

Core Settings

# Required
PRIVATE_KEY=           # Operator wallet (funded with ETH)
SOURCE_RPC_URL=        # Source chain RPC
DESTINATION_RPC_URL=   # Destination chain RPC

# Chain IDs
SOURCE_CHAIN_ID=11155111       # Sepolia
DESTINATION_CHAIN_ID=88991     # Arc Testnet

Fee Settings

# Minimum fee to process a transaction
MIN_INDEXER_FEE=100000         # Minimum fee (in token units)

# Skip transactions with fees below this
# Set higher in high-gas conditions

Performance Settings

# Concurrent processing
MAX_CONCURRENT_JOBS=5          # Parallel transactions

# Polling intervals
SOURCE_POLL_INTERVAL_MS=10000  # How often to check source chain
ATTESTATION_POLL_INTERVAL_MS=30000  # How often to poll Circle

Historical Scanning

# Catch missed messages after restarts
HISTORICAL_SCAN_ENABLED=true
HISTORICAL_TIME_WINDOW_MS=3600000   # Look back 1 hour
HISTORICAL_SCAN_INTERVAL_MS=300000  # Re-scan every 5 min

Docker Deployment

docker-compose.yml

version: '3.8'

services:
  indexer:
    build: .
    command: ["npm", "run", "start", "--", "--mode", "indexer"]
    env_file:
      - .env
    restart: unless-stopped
    deploy:
      resources:
        limits:
          cpus: '2'
          memory: 2G
    logging:
      driver: json-file
      options:
        max-size: "10m"
        max-file: "3"

Run

docker-compose up -d indexer
docker-compose logs -f indexer

Monitoring

Health Check

# Check if process is running
pm2 status pons-indexer

# View logs
pm2 logs pons-indexer --lines 100

Key Metrics

Monitor these values:

Metric	Healthy	Action if Unhealthy
Messages indexed/hour	>0	Check RPC connection
Success rate	>95%	Check wallet balance
Wallet balance	>0.05 ETH	Refill wallet
Error rate	Less than 5%	Check logs

Log Messages

✅ Good:
[INFO] Indexer started, monitoring source chain
[INFO] Found burn event: 0xabc...
[INFO] Attestation received for message
[INFO] Message indexed successfully, earned indexer fee

⚠️ Warning:
[WARN] Low wallet balance: 0.04 ETH

❌ Error:
[ERROR] Failed to index message: insufficient gas
[ERROR] RPC connection failed

Troubleshooting

"Insufficient gas"

# Check balance
cast balance $WALLET_ADDRESS --rpc-url $DESTINATION_RPC_URL

# Fund wallet with more ETH
# Sepolia: use faucet
# Mainnet: transfer from exchange

"Attestation not found"

• Normal for cross-chain transfers (wait for proof)
• If persists, check cross-chain protocol status

"Already indexed"

• Another indexer processed this message first
• This is normal competition behavior
• Increase uptime to catch more messages

"RPC rate limited"

# Use a better RPC provider or run your own node
SOURCE_RPC_URL=https://your-own-node.com

Profitability

Costs

Item	Estimated Cost
Gas per index	~0.002 ETH
Server (VPS)	~$10-50/month

Revenue

Volume	Monthly Transactions	Earnings Potential
Low	~3,000/month	Covers server costs
Medium	~15,000/month	Profitable
High	~30,000/month	Strong returns

Break-even

• Earnings depend on fee rates and network volume
• Server costs: ~$20-50/month
• Gas costs: ~$6/month (100 txn * $0.002)
• Net profit: ~$250/month

Best Practices

Wallet Management

• Use a dedicated wallet (never your main wallet)
• Start with small amounts
• Set up balance alerts
• Withdraw earnings regularly

Uptime

• Use PM2 or Docker with auto-restart
• Set up health monitoring
• Use reliable RPC providers
• Consider running multiple instances

Security

• Never expose private key
• Run behind firewall
• Keep software updated
• Monitor for suspicious activity

Next Steps

• Run a Resolver: Add resolver to earn more fees
• Security Guide: Production security best practices