lnd: lnd hangs at “waiting for chain backend to finish sync, start_height=521042”

lnd with bitcoind backend never gets past “waiting for chain backend to finish sync”, even though bitcoind is fully synced.

• version of lnd: 0.4.1-beta
• which operating system: Windows Server 2012 Core (no GUI)
• version of bitcoind backend: 0.16.0

I’m using Lightning Networks’ lnd 0.4.1-beta node in Windows, with a Bitcoin Core bitcoind full node backend. The bitcoind full node has the --txindex option, and is fully synced according to bitnodes.earn.com

I’ve configured bitcoind to use ZMQ, and indeed netstat -a -b shows bitcoind is listening on 28332 for ZMQ connections. Bitcoin.conf is configured with:

txindex=1
zmqpubrawblock=tcp://127.0.0.1:28332
zmqpubrawtx=tcp://127.0.0.1:28332
zmqpubhashblock=tcp://127.0.0.1:28332
zmqpubhashtx=tcp://127.0.0.1:28332
server=1

lnd.conf has the following

debuglevel=debug
logdir=E:\lnd\data\logs
lnddir=E:\lnd
datadir=E:\lnd\data
bitcoin.active=1
bitcoin.mainnet-1
bitcoin.node=bitcoind
bitcoin.chaindir=E:\lnd\data\bitcoin-chain
bitcoind.dir=E:\data
bitcoind.rpchost=localhost
bitcoind.rpcuser=<username>
bitcoind.rpcpass=<password>
bitcoind.zmqpath=tcp://127.0.0.1:28332
autopilot.active=1
externalip=<x.x.x.x>

(needless to say, the user/pass and externalip are not literally those values listed).

lnd.log shows:

2018-05-03 09:12:22.305 [INF] LTND: Version 0.4.1-beta commit=
2018-05-03 09:12:22.308 [INF] LTND: Active chain: Bitcoin (network=mainnet)
2018-05-03 09:12:22.311 [INF] CHDB: Checking for schema update: latest_version=0, db_version=0
2018-05-03 09:12:22.312 [INF] RPCS: Generating TLS certificates...
2018-05-03 09:12:22.376 [INF] RPCS: Done generating TLS certificates
2018-05-03 09:12:22.396 [INF] RPCS: password RPC server listening on 127.0.0.1:10009
2018-05-03 09:12:22.397 [INF] RPCS: password gRPC proxy started at 127.0.0.1:8080
2018-05-03 09:12:22.399 [INF] LTND: Waiting for wallet encryption password. Use `lncli create` to create wallet, or `lncli unlock` to unlock already created wallet.
2018-05-03 09:13:34.681 [INF] LNWL: Opened wallet
2018-05-03 09:13:34.785 [INF] LTND: Primary chain is set to: bitcoin
2018-05-03 09:13:34.786 [INF] LTND: Initializing bitcoind backed fee estimator
2018-05-03 09:13:36.624 [INF] LNWL: Opened wallet
2018-05-03 09:13:37.651 [INF] LNWL: Started listening for blocks via ZMQ on tcp://127.0.0.1:28332
2018-05-03 09:13:39.340 [INF] LNWL: The wallet has been unlocked without a time limit
2018-05-03 09:13:39.343 [INF] LTND: LightningWallet opened
2018-05-03 09:13:43.946 [INF] LNWL: Started rescan from block 0000000099c744455f58e6c6e98b671e1bf7f37346bfd4cf5d0274ad8ee660cb (height 10000) for 0 addresses
2018-05-03 09:13:44.237 [INF] LNWL: Starting rescan from block 0000000099c744455f58e6c6e98b671e1bf7f37346bfd4cf5d0274ad8ee660cb
2018-05-03 09:13:47.219 [INF] HSWC: Restoring in-memory circuit state from disk
2018-05-03 09:13:47.221 [INF] HSWC: Payment circuits loaded: num_pending=0, num_open=0
2018-05-03 09:13:47.233 [INF] RPCS: RPC server listening on 127.0.0.1:10009
2018-05-03 09:13:47.235 [INF] RPCS: gRPC proxy started at 127.0.0.1:8080
2018-05-03 09:13:49.243 [INF] LTND: Waiting for chain backend to finish sync, start_height=521042

The lnd daemon has been sitting at Waiting for chain backend to finish sync, start_height=521042 for 20 minutes, no change. bitcoind now reports it has just received block 521051.

Expected behaviour

lnd should work correctly or report an error if it cannot reliably connect to ZMQ at bitcoind.

Actual behaviour

lnd simply hangs at this point. lncli stop hangs as well. The only way to get lnd to stop is CTRL-C in the daemon window or “end task” via Task Manager.

Question has also been asked at https://bitcoin.stackexchange.com/questions/74687/lightning-node-daemon-hangs-at-waiting-for-chain-backend-to-finish-sync-start