Boltz API

🚢Backend Deployment

Deploying Boltz backend has to be done with great care since it will have full control over the Lightning Node it is connected to. With great power comes great responsibility.

Prerequisites:

  • The latest Node.js LTS and npm installed. We recommend using nvm to manage npm installs: nvm install --lts

  • rsync (needed to compile the TypeScript code)

Boltz Backend requires a synced Bitcoin Core Instance to connect to the Bitcoin mainchain. Similarly, Elements Core to connect to the Liquid sidechain etc. Bitcoin/Elements Core must:

  • Have the transaction index enabled: txindex=1

  • Enable ZeroMQ streams for raw blocks and raw transactions: (zmqpubrawblock=tcp://<host>:<port> and zmqpubrawtx=tcp://<host>:<port>)

Boltz requires a LND or CLN node running on Bitcoin to be present. For LND, no special configuration is needed, all official release binaries are compatible.

Config Sample

configpath = "/home/boltz/.boltz/boltz.conf"
dbpath = "/home/boltz/.boltz/boltz.db"
logpath = "/home/boltz/.boltz/boltz.log"
datadir = "/home/boltz/.boltz"

# This mnemonic is not for the wallet that holds the onchain coins
# but the claim and refund keys are derived from it
mnemonicpath = "/home/boltz/.boltz/seed.dat"

# Possible values are: error, warning, info, verbose, debug, silly
loglevel = "debug"

# The backend needs a PostgreSQL database
[postgres]
host = "127.0.0.1"
port = 5432
database = "boltz"
username = "boltz"
password = "boltz"

# Logs can be sent to a Loki log aggregator
# lokiHost = "http://127.0.0.1:3100"
# lokiNetwork = "regtest"

# This value configures the type of the lockup address of normal Submarine Swaps:
#   - false: P2SH nested P2WSH
#   - true: P2WSH
swapwitnessaddress = false

# Enables the prepay minerfee Reverse Submarine Swap procotol
# If this value is "true", an invoice for the miner fee has to be paid
# before hold invoice of the Revese Swap
prepayminerfee = false

# This is the REST API that should be exposed to the public
# It does not support HTTPS but only plaintext HTTP. A reverse
# proxy should be setup with a web server like Nginx
[api]
host = "127.0.0.1"
port = 9_001

# Configure CORS headers set by the backend
# "" to disable
cors = "*"

# The backend can expose a metrics endpoint about swap count, volume, etc
# [prometheus]
# host = "127.0.0.1"
# port = 9_092

# And this the gRPC API that is used by the boltz-cli executable
[grpc]
host = "127.0.0.1"
port = 9_000
certpath = "/home/boltz/.boltz/tls.cert"
keypath = "/home/boltz/.boltz/tls.key"

# The interval in seconds at which new rates for pairs that
# do not have a hardcoded rate should be updates
[rates]
interval = 1

# Boltz Backend allows for backing up LND SCBs and
# the database to a S3 API compatible storage
[backup]
# Cron interval at which a new backup should be uploaded. The default value is daily
interval = "0 0 * * *"

  [backup.simpleStorage]
  bucket = ""
  endpoint = ""
  port = 443
  useSSL = true
  accessKey = ""
  secretKey = ""

# Boltz backend supports sending messages to Mattermost after successful and
# failed Swaps and if the wallet or channel balance is below a configurable threshold
[notification]
mattermostUrl = ""
token = ""
channel = ""
# A string to prefix all messages with
prefix = "mainnet"
# Optionally, important alerts can be sent to a different channel
# channelAlerts = ""

prefix = ""
# Interval in minutes at which the wallet and channel balances should be checked
interval = 1

[swap]
# Chains on which claim transactions should be deferred
# Deferring means not broadcasting claim transactions immediately,
# but waiting for cooperative key path spend of the client
# or batching a script path spend
deferredClaimSymbols = ["BTC", "L-BTC"]

# Interval at which batched script path spends of deferred claim transactions should be done
batchClaimInterval = '*/15 * * * *'

# Tolerance in minutes before swap expiry for a claim transaction to be eligible for batching
expiryTolerance = 120

    # Cost of claim transaction * multiplier = minimial swap size
    [swap.minSwapSizeMultipliers]
    reverse = 7
    reverse = 6
    chain = 6


# The array "pairs" configures the trading pairs that Boltz should support
# A pair can have the following options:
# - "base" (required): base currency
# - "quote" (required): quote currency
# - "timeoutDelta": after how many minutes a Swap of that pair should timeout
# - "rate": the rate for a pair can be hardcoded (only sensible for same currency pairs);
#           if the rate is not hardcoded the mean value from these exchanges will be used:
#             - Binance
#             - Bitfinex
#             - Coinbase Pro
#             - Kraken
#             - Poloniex
# - "fee": percentage of the swapped amount that should be charged as fee
# - "swapInFee" (optional): same as "fee" but for swaps from onchain to lightning; defaults to "fee" if not set
[[pairs]]
base = "BTC"
quote = "BTC"
rate = 1

maxSwapAmount = 10_000_000
minSwapAmount = 10_000

# Whether the pair should be available in the legacy v1 API
# Defaults to false
isLegacy = true

# Expiry of the invoices generated for reverse swaps of this pair
# If not set, half of the expiry time of the reverse swap will be used
invoiceExpiry = 7200

    # Timeouts in minutes
    [pairs.timeoutDelta]
    reverse = 1440
    swapMinimal = 1440
    swapMaximal = 2880
    swapTaproot = 10080

[[pairs]]
base = "L-BTC"
quote = "BTC"
rate = 1
fee = 0.5
swapInFee = 0.2

maxSwapAmount = 1_000_000
minSwapAmount = 100_000

# Which swap types to enable for the pair, by default all are enabled
# Possible types:
# - submarine
# - reverse
# - chain
swapTypes = ["submarine", "reverse", "chain"]

    [pairs.chainSwap]
    # If not set, the "fee" will be used
    buyFee = 0.1
    sellFee = 0.15

    # Overrides min and max swap amounts for chain swaps of this pair
    minSwapAmount = 100_000
    maxSwapAmount = 10_000_000

    [pairs.timeoutDelta]
    chain = 1440
    reverse = 1440
    swapMinimal = 1440
    swapMaximal = 2880
    swapTaproot = 10080

[[pairs]]
base = "L-BTC"
quote = "BTC"
fee = 0.25
swapInFee = 0.1
rate = 1

maxSwapAmount = 4_294_967
minSwapAmount = 10_000

    [pairs.timeoutDelta]
    reverse = 1440
    swapMinimal = 1400
    swapMaximal = 2880
    swapTaproot = 10080

# The array "currencies" configures the chain and LND clients for the "pairs"
# Not configuring the LND client is possible but will cause that chain not to support Lightning
# The values are pretty self-explainatory apart from: "minWalletBalance" and "minChannelBalance" which trigger
# a Mattermost notification
[[currencies]]
symbol = "BTC"
network = "bitcoinTestnet"
minWalletBalance = 10_000_000
minChannelBalance = 10_000_000

# Maximal 0-conf amount *per swap*
maxZeroConfAmount = 100_000

# Maximal 0-conf amount for the currency
maxZeroConfRisk = 1_000_000

# Onchain wallet provider
# Options: "core" or "lnd"
# Defaults to "lnd"
# preferredWallet = "core"

# Can be set to alert about the balance of an unused wallet being more than a certain threshold
# maxUnusedWalletBalance = 100_000

    [currencies.chain]
    host = "127.0.0.1"
    port = 18_332

    # The requests to Bitcoin Core like clients can be authenticated with cookie files or user/password
    # If both are configured, cookie files are preferred
    cookie = ""

    user = "bitcoin"
    password = "bitcoin"

    # When there is more than one wallet loaded, the name of the wallet that should be used needs to be specified
    # wallet = "boltz"

    # Optional API endpoint of a MempoolSpace instance running on the chain of the configured client
    mempoolSpace = "https://mempool.space/api"

    # The ZMQ endpoints for a chain can be configured here
    # If they are not set, those endpoints are fetched via the "getzmqnotifications" RPC method of the node
    zmqpubrawtx = "tcp://0.0.0.0:29000"
    zmqpubrawblock = "tcp://0.0.0.0:29001"

    # hashblock is not required and should only be used as fallback in case rawblock is not available
    # zmqpubhashblock = ""

    [currencies.lnd]
    host = "127.0.0.1"
    port = 10_009
    certpath = "/home/boltz/.lnd/bitcoin/tls.cert"
    macaroonpath = "/home/boltz/.lnd/bitcoin/admin.macaroon"
    maxPaymentFeeRatio = 0.03

    # A CLN node can be connected via its gRPC interface
    [currencies.cln]
    host = "127.0.0.1"
    port = 9291
    rootCertPath = "/home/boltz/.lightning/testnet/ca.pem"
    privateKeyPath = "/home/boltz/.lightning/testnet/client-key.pem"
    certChainPath = "/home/boltz/.lightning/testnet/client.pem"

        # The Boltz hold invoice plugin is required: https://github.com/BoltzExchange/boltz-backend/tree/master/tools/plugins/hold
        [currencies.cln.hold]
        host = "127.0.0.1"
        port = 9292
        rootCertPath = "/home/boltz/.lightning/testnet/hold/ca.pem"
        privateKeyPath = "/home/boltz/.lightning/testnet/hold/client-key.pem"
        certChainPath = "/home/boltz/.lightning/testnet/hold/client.pem"

        # Optionally, mpay (https://github.com/BoltzExchange/boltz-backend/tree/master/tools/plugins/mpay) can be used to pay invoices
        [currencies.cln.mpay]
        host = "127.0.0.1"
        port = 9293
        rootCertPath = "/home/boltz/.lightning/testnet/mpay/ca.pem"
        privateKeyPath = "/home/boltz/.lightning/testnet/mpay/client-key.pem"
        certChainPath = "/home/boltz/.lightning/testnet/mpay/client.pem"

[liquid]
symbol = "L-BTC"
network = "liquidTestnet"

maxSwapAmount = 4_294_967
minSwapAmount = 10_000

minWalletBalance = 100_000_000

# Time to wait in milliseconds before accepting a lowball 0-conf transaction
# and checking "testmempoolaccept" on the public node
zeroConfWaitTime = 1_000

    # API endpoint to check for reliable 0-conf acceptance
    # Disables "zeroConfWaitTime"
    [liquid.zeroConfTool]
    endpoint = ""

    # Interval in milliseconds at which calls to the endpoint should be retried
    # interval = 100

    # How often calls to the endpoint should be retried before
    # giving up 0-conf for that transaction
    # maxRetries = 60

    [liquid.chain]
    host = "127.0.0.1"
    port = 18884
    cookie = "/home/boltz/.elements/liquidv1/.cookie"

    # When there is more than one wallet loaded, the name of the wallet that should be used needs to be specified
    # wallet = "boltz"

Database migrations

To migrate from an SQLite database to PostgreSQL, use the following script with pgloader:

load database
    from sqlite://<path>
    into pgsql://<user>:<password>>@<host>/<database>

with quote identifiers, data only, reset sequences

set work_mem to '16MB', maintenance_work_mem to '512 MB';
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