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Overview

The Filler Bot is a keeper bot that matches orders against resting liquidity on the Drift protocol. It performs three main functions:
  1. Swift Order Matching: Matches swift orders (fast, off-chain signed orders) against resting limit orders in the orderbook
  2. Auction Order Filling: Fills on-chain auction orders by finding the best available liquidity
  3. Limit Order Uncrossing: Identifies and executes crossed limit orders where bid prices exceed ask prices
The bot subscribes to real-time updates via gRPC and Pyth price feeds, maintains a decentralized limit order book (DLOB) in memory, and continuously searches for profitable fill opportunities.

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How It Works

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Event Flow

The Filler Bot operates through several concurrent event streams:
  • gRPC Slot Updates: Triggers periodic orderbook scanning for crosses
  • gRPC Account Updates: Updates the DLOB with new/modified orders
  • Swift Order Stream: Receives new swift orders via websocket
  • Pyth Price Feeds: Provides real-time oracle price updates
When a fillable order is detected, the bot builds a transaction with:
  • Appropriate compute unit limits
  • Dynamic priority fees (based on current network conditions)
  • Fill instructions with optimal maker-taker matching

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Transaction Lifecycle

  1. Detection: Cross or fillable order identified
  2. Building: Transaction constructed with fill instructions
  3. Sending: Signed transaction sent to Solana network
  4. Confirmation: Transaction status monitored via gRPC updates
  5. Metrics: Performance tracked (fills, revenue, competition)

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Running the Filler Bot

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Basic Usage

RUST_LOG=filler=info,dlob=info,swift=info \
    cargo run --release -- --mainnet --filler

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Fill Specific Markets

# Fill only SOL-PERP (market 0) and BTC-PERP (market 1)
cargo run --release -- --mainnet --filler --market-ids "0,1"

# Fill all available markets
cargo run --release -- --mainnet --filler --all-markets

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Configuration

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CLI Flags

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--filler
boolean
default:"true"
Enable the filler bot mode. This is the default mode when no other bot flag is specified.
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--all-markets
boolean
default:"false"
Fill orders for all available markets. When enabled, this overrides the --market-ids flag and the bot will monitor all perpetual markets (excluding bet markets and uninitialized markets).
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--market-ids
string
default:"0,1,2"
Comma-separated list of perpetual market indices to fill orders for. Can also be set via the MARKET_IDS environment variable.Example: --market-ids "0,1,2,3,4" to fill SOL, BTC, ETH, APT, and ARB markets.
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--swift-cu-limit
u32
default:"364000"
Compute unit limit for swift order fill transactions. Swift fills typically require more compute units due to signature verification and off-chain order validation.
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--fill-cu-limit
u32
default:"256000"
Compute unit limit for regular auction and limit order fill transactions. Standard fills generally require fewer compute units than swift fills.
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--priority-fee
u64
default:"512"
Base priority fee in microlamports per compute unit. The actual priority fee may be dynamically adjusted based on network congestion and recent transaction data.
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--mainnet
boolean
default:"true"
Connect to Solana mainnet-beta. When set to false, connects to devnet. Can also be set via the MAINNET environment variable.
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--dry
boolean
default:"false"
Enable dry-run mode. Transactions are simulated but not actually sent to the network. Useful for testing configuration and strategy without risking funds. Can also be set via the DRY_RUN environment variable.
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--sub-account-id
u16
default:"0"
Sub-account ID to use for the bot’s Drift account. Allows running multiple bots with different sub-accounts from the same wallet.

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Environment Variables

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Required

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BOT_PRIVATE_KEY
string
required
Base58-encoded private key for the bot’s Solana wallet. This wallet should have sufficient SOL for transaction fees and USDC for settling trades.
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RPC_URL
string
required
Solana RPC endpoint URL. Use a high-performance RPC provider for best results.Example: https://api.mainnet-beta.solana.com
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GRPC_ENDPOINT
string
required
Drift gRPC endpoint for real-time account and slot updates.Example: https://api.rpcpool.com
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GRPC_X_TOKEN
string
required
Authentication token for the gRPC endpoint.
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PYTH_LAZER_TOKEN
string
required
Pyth Lazer access token for real-time price feeds. The bot uses Pyth for accurate oracle price data.

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Optional

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METRICS_PORT
number
default:"9898"
Port for the Prometheus metrics HTTP server. Metrics include fill counts, revenue, transaction success rates, and more.
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MARKET_IDS
string
default:"0,1,2"
Default market IDs to fill. Can be overridden by the --market-ids CLI flag.

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Monitoring

The Filler Bot exposes several HTTP endpoints for monitoring:
  • http://localhost:9898/metrics - Prometheus metrics
  • http://localhost:9898/health - Health check endpoint
  • http://localhost:9898/dashboard - Human-readable dashboard

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Key Metrics

  • Fills: Total number of successful fills
  • Revenue: Profit from maker rebates and taker fees
  • Transaction Success Rate: Percentage of sent transactions that confirmed successfully
  • Competition: Orders that were filled by others before us
  • Order DNE: “Order Does Not Exist” errors (order was cancelled or already filled)

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Performance Tuning

Compute Unit Limits: If you see transactions failing with “Compute Unit Exceeded” errors, increase the --swift-cu-limit or --fill-cu-limit values.
Priority Fees: During high network congestion, increase the --priority-fee to improve transaction landing rates. The bot uses dynamic priority fee calculation, but the base fee serves as a minimum.
Market Selection: Start with fewer markets (--market-ids "0,1") to reduce compute requirements and focus on high-volume markets like SOL and BTC.

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Common Issues

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Order Does Not Exist Errors

This is normal and indicates healthy competition. It means another keeper filled the order before your transaction landed. Monitor the order_dne_count metric to understand competition levels.

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Transaction Timeouts

If transactions frequently timeout:
  1. Verify your RPC endpoint is reliable and low-latency
  2. Increase priority fees
  3. Check network congestion on Solana

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No Fills

If the bot is running but not executing fills:
  1. Verify the markets you’re monitoring have active orderbook activity
  2. Check that oracle prices are updating (look for gRPC slot updates in logs)
  3. Ensure your wallet has sufficient USDC balance for settling trades
  4. Verify gRPC and Pyth subscriptions are connected (check logs for “subscribed” messages)

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Source Code Reference

The Filler Bot implementation can be found in src/filler.rs. Key components:
  • FillerBot struct (src/filler.rs:47): Main bot structure
  • FillerBot::new (src/filler.rs:62): Initialization and subscription setup
  • FillerBot::run (src/filler.rs:144): Main event loop
  • Config struct (src/main.rs:27): CLI configuration options

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