RegisterSpendNtfn

RegisterSpendNtfn is a synchronous response-streaming RPC that registers an intent for a client to be notification once a spend request has been spent by a transaction that has confirmed on-chain.

A client can specify whether the spend request should be for a particular outpoint or for an output script by specifying a zero outpoint.

Source: chainrpc/chainnotifier.proto

gRPC

info

This is a server-streaming RPC

rpc RegisterSpendNtfn (SpendRequest) returns (stream SpendEvent);

REST

HTTP Method	Path
POST	/v2/chainnotifier/register/spends

Code Samples

gRPC

Javascript

const fs = require('fs');
const grpc = require('@grpc/grpc-js');
const protoLoader = require('@grpc/proto-loader');

const GRPC_HOST = 'localhost:10009'
const MACAROON_PATH = 'LND_DIR/data/chain/bitcoin/regtest/admin.macaroon'
const TLS_PATH = 'LND_DIR/tls.cert'

const loaderOptions = {
  keepCase: true,
  longs: String,
  enums: String,
  defaults: true,
  oneofs: true,
};
const packageDefinition = protoLoader.loadSync(['lightning.proto', 'chainrpc/chainnotifier.proto'], loaderOptions);
const chainrpc = grpc.loadPackageDefinition(packageDefinition).chainrpc;
process.env.GRPC_SSL_CIPHER_SUITES = 'HIGH+ECDSA';
const tlsCert = fs.readFileSync(TLS_PATH);
const sslCreds = grpc.credentials.createSsl(tlsCert);
const macaroon = fs.readFileSync(MACAROON_PATH).toString('hex');
const macaroonCreds = grpc.credentials.createFromMetadataGenerator(function(args, callback) {
  let metadata = new grpc.Metadata();
  metadata.add('macaroon', macaroon);
  callback(null, metadata);
});
let creds = grpc.credentials.combineChannelCredentials(sslCreds, macaroonCreds);
let client = new chainrpc.ChainNotifier(GRPC_HOST, creds);
let request = {
  outpoint: <Outpoint>,
  script: <bytes>,
  height_hint: <uint32>,
};
let call = client.registerSpendNtfn(request);
call.on('data', function(response) {
  // A response was received from the server.
  console.log(response);
});
call.on('status', function(status) {
  // The current status of the stream.
});
call.on('end', function() {
  // The server has closed the stream.
});
// Console output:
//  {
//    "spend": <SpendDetails>,
//    "reorg": <Reorg>,
//  }

Python

import codecs, grpc, os
# Generate the following 2 modules by compiling the chainrpc/chainnotifier.proto with the grpcio-tools.
# See https://github.com/lightningnetwork/lnd/blob/master/docs/grpc/python.md for instructions.
import chainnotifier_pb2 as chainrpc, chainnotifier_pb2_grpc as chainnotifierstub

GRPC_HOST = 'localhost:10009'
MACAROON_PATH = 'LND_DIR/data/chain/bitcoin/regtest/admin.macaroon'
TLS_PATH = 'LND_DIR/tls.cert'

# create macaroon credentials
macaroon = codecs.encode(open(MACAROON_PATH, 'rb').read(), 'hex')
def metadata_callback(context, callback):
  callback([('macaroon', macaroon)], None)
auth_creds = grpc.metadata_call_credentials(metadata_callback)
# create SSL credentials
os.environ['GRPC_SSL_CIPHER_SUITES'] = 'HIGH+ECDSA'
cert = open(TLS_PATH, 'rb').read()
ssl_creds = grpc.ssl_channel_credentials(cert)
# combine macaroon and SSL credentials
combined_creds = grpc.composite_channel_credentials(ssl_creds, auth_creds)
# make the request
channel = grpc.secure_channel(GRPC_HOST, combined_creds)
stub = chainnotifierstub.ChainNotifierStub(channel)
request = chainrpc.SpendRequest(
  outpoint=<Outpoint>,
  script=<bytes>,
  height_hint=<uint32>,
)
for response in stub.RegisterSpendNtfn(request):
  print(response)
# {
#    "spend": <SpendDetails>,
#    "reorg": <Reorg>,
# }

REST

Javascript

const fs = require('fs');
const request = require('request');

const REST_HOST = 'localhost:8080'
const MACAROON_PATH = 'LND_DIR/data/chain/bitcoin/regtest/admin.macaroon'

let requestBody = {
  outpoint: <object>, // <Outpoint> 
  script: <string>, // <bytes> (base64 encoded)
  height_hint: <integer>, // <uint32> 
};
let options = {
  url: `https://${REST_HOST}/v2/chainnotifier/register/spends`,
  // Work-around for self-signed certificates.
  rejectUnauthorized: false,
  json: true,
  headers: {
    'Grpc-Metadata-macaroon': fs.readFileSync(MACAROON_PATH).toString('hex'),
  },
  form: JSON.stringify(requestBody),
}
request.post(options, function(error, response, body) {
  console.log(body);
});
// Console output:
//  {
//    "spend": <object>, // <SpendDetails> 
//    "reorg": <object>, // <Reorg> 
//  }



// --------------------------
// Example with websockets:
// --------------------------
const WebSocket = require('ws');
const fs = require('fs');

const REST_HOST = 'localhost:8080'
const MACAROON_PATH = 'LND_DIR/data/chain/bitcoin/regtest/admin.macaroon'

let ws = new WebSocket(`wss://${REST_HOST}/v2/chainnotifier/register/spends?method=POST`, {
  // Work-around for self-signed certificates.
  rejectUnauthorized: false,
  headers: {
    'Grpc-Metadata-Macaroon': fs.readFileSync(MACAROON_PATH).toString('hex'),
  },
});
let requestBody = {
  outpoint: <Outpoint>, // <Outpoint> 
  script: <bytes>, // <bytes> (base64 encoded)
  height_hint: <uint32>, // <uint32> 
};
ws.on('open', function() {
    ws.send(JSON.stringify(requestBody));
});
ws.on('error', function(err) {
    console.log('Error: ' + err);
});
ws.on('message', function(body) {
    console.log(body);
});
// Console output:
//  {
//    "spend": <object>, // <SpendDetails>
//    "reorg": <object>, // <Reorg>
//  }

Python

import base64, codecs, json, requests

REST_HOST = 'localhost:8080'
MACAROON_PATH = 'LND_DIR/data/chain/bitcoin/regtest/admin.macaroon'
TLS_PATH = 'LND_DIR/tls.cert'

url = f'https://{REST_HOST}/v2/chainnotifier/register/spends'
macaroon = codecs.encode(open(MACAROON_PATH, 'rb').read(), 'hex')
headers = {'Grpc-Metadata-macaroon': macaroon}
data = {
  'outpoint': <Outpoint>,
  'script': base64.b64encode(<bytes>),
  'height_hint': <uint32>,
}
r = requests.post(url, headers=headers, stream=True, data=json.dumps(data), verify=TLS_PATH)
for raw_response in r.iter_lines():
  json_response = json.loads(raw_response)
  print(json_response)
# {
#    "spend": <SpendDetails>,
#    "reorg": <Reorg>,
# }

Shell

# There is no CLI command for this RPC

Messages

chainrpc.SpendRequest

Source: chainrpc/chainnotifier.proto

Field	gRPC Type	REST Type	REST Placement
outpoint The outpoint for which we should request a spend notification for. If set to a zero outpoint, then the spend notification will be requested for the script instead. A zero or nil outpoint is not supported for Taproot spends because the output script cannot reliably be computed from the witness alone and the spent output script is not always available in the rescan context. So an outpoint must always be specified when registering a spend notification for a Taproot output.	Outpoint	object	body
script The output script for the outpoint above. This will be used by light clients to match block filters. If the outpoint is set to a zero outpoint, then a spend notification will be requested for this script instead.	bytes	string	body
height_hint The earliest height in the chain for which the outpoint/output script could have been spent. This should in most cases be set to the broadcast height of the outpoint/output script.	uint32	integer	body

chainrpc.SpendEvent

Source: chainrpc/chainnotifier.proto

Field	gRPC Type	REST Type
spend An event that includes the details of the spending transaction of the request (outpoint/output script).	SpendDetails	object
reorg An event sent when the spending transaction of the request was reorged out of the chain.	Reorg	object

Nested Messages

chainrpc.Outpoint

Field	gRPC Type	REST Type
hash The hash of the transaction.	bytes	string
index The index of the output within the transaction.	uint32	integer

chainrpc.SpendDetails

Field	gRPC Type	REST Type
spending_outpoint The outpoint was that spent.	Outpoint	object
raw_spending_tx The raw bytes of the spending transaction.	bytes	string
spending_tx_hash The hash of the spending transaction.	bytes	string
spending_input_index The input of the spending transaction that fulfilled the spend request.	uint32	integer
spending_height The height at which the spending transaction was included in a block.	uint32	integer

chainrpc.Reorg

note

This response has no parameters.