RegisterBlockEpochNtfn

RegisterBlockEpochNtfn is a synchronous response-streaming RPC that registers an intent for a client to be notified of blocks in the chain. The stream will return a hash and height tuple of a block for each new/stale block in the chain. It is the client's responsibility to determine whether the tuple returned is for a new or stale block in the chain.

A client can also request a historical backlog of blocks from a particular point. This allows clients to be idempotent by ensuring that they do not missing processing a single block within the chain.

Source: chainrpc/chainnotifier.proto

gRPC

info

This is a server-streaming RPC

rpc RegisterBlockEpochNtfn (BlockEpoch) returns (stream BlockEpoch);

REST

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

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 = {
  hash: <bytes>,
  height: <uint32>,
};
let call = client.registerBlockEpochNtfn(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:
//  {
//    "hash": <bytes>,
//    "height": <uint32>,
//  }

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.BlockEpoch(
  hash=<bytes>,
  height=<uint32>,
)
for response in stub.RegisterBlockEpochNtfn(request):
  print(response)
# {
#    "hash": <bytes>,
#    "height": <uint32>,
# }

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 = {
  hash: <string>, // <bytes> (base64 encoded)
  height: <integer>, // <uint32> 
};
let options = {
  url: `https://${REST_HOST}/v2/chainnotifier/register/blocks`,
  // 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:
//  {
//    "hash": <string>, // <bytes> (base64 encoded)
//    "height": <integer>, // <uint32> 
//  }



// --------------------------
// 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/blocks?method=POST`, {
  // Work-around for self-signed certificates.
  rejectUnauthorized: false,
  headers: {
    'Grpc-Metadata-Macaroon': fs.readFileSync(MACAROON_PATH).toString('hex'),
  },
});
let requestBody = {
  hash: <bytes>, // <bytes> (base64 encoded)
  height: <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:
//  {
//    "hash": <string>, // <bytes>
//    "height": <integer>, // <uint32>
//  }

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/blocks'
macaroon = codecs.encode(open(MACAROON_PATH, 'rb').read(), 'hex')
headers = {'Grpc-Metadata-macaroon': macaroon}
data = {
  'hash': base64.b64encode(<bytes>),
  'height': <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)
# {
#    "hash": <bytes>,
#    "height": <uint32>,
# }

Shell

# There is no CLI command for this RPC

Messages

chainrpc.BlockEpoch

Source: chainrpc/chainnotifier.proto

Field	gRPC Type	REST Type	REST Placement
hash The hash of the block.	bytes	string	body
height The height of the block.	uint32	integer	body

chainrpc.BlockEpoch

Source: chainrpc/chainnotifier.proto

Field	gRPC Type	REST Type
hash The hash of the block.	bytes	string
height The height of the block.	uint32	integer