From 5044cd64689f3ec0abf58c77d35b903ae7ef9ed3 Mon Sep 17 00:00:00 2001
From: Olaoluwa Osuntokun <laolu32@gmail.com>
Date: Tue, 12 Sep 2017 17:11:21 +0200
Subject: [PATCH] chainntnfs/btcdnotify: recognize JSON-RPC error in
 RegisterSpendNtfn
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

This commit fixes a prior bug in the logic for registering a new spend
notification. Previously, if the transaction wasn’t found in the
mempool or already confirmed within the chain, then
GetRawTransactionVerbose would return an error which would cause the
function itself to exit with an error.

This issue would then cause the server to be unable to start up as the
breach arbiter would be unable to register for spend notifications for
all the channels that it needed to be watching.

We fix this error simply by recognizing the particular JSON-RPC error
that will be returned in this scenario and treating it as a benign
error.
---
 chainntnfs/btcdnotify/btcd.go | 28 +++++++++++++++++++---------
 1 file changed, 19 insertions(+), 9 deletions(-)

diff --git a/chainntnfs/btcdnotify/btcd.go b/chainntnfs/btcdnotify/btcd.go
index b928def9..a6b305af 100644
--- a/chainntnfs/btcdnotify/btcd.go
+++ b/chainntnfs/btcdnotify/btcd.go
@@ -506,6 +506,8 @@ func (b *BtcdNotifier) notifyBlockEpochs(newHeight int32, newSha *chainhash.Hash
 		go func(ntfnChan chan *chainntnfs.BlockEpoch, cancelChan chan struct{},
 			clientWg *sync.WaitGroup) {
 
+			// TODO(roasbeef): move to goroutine per client, use sync queue
+
 			defer clientWg.Done()
 			defer b.wg.Done()
 
@@ -664,18 +666,26 @@ func (b *BtcdNotifier) RegisterSpendNtfn(outpoint *wire.OutPoint,
 	if txout == nil {
 		transaction, err := b.chainConn.GetRawTransactionVerbose(&outpoint.Hash)
 		if err != nil {
-			return nil, err
+			jsonErr, ok := err.(*btcjson.RPCError)
+			switch {
+			case ok && jsonErr.Code == -5:
+			default:
+				return nil, err
+			}
 		}
 
-		blockhash, err := chainhash.NewHashFromStr(transaction.BlockHash)
-		if err != nil {
-			return nil, err
-		}
+		if transaction != nil {
+			blockhash, err := chainhash.NewHashFromStr(transaction.BlockHash)
+			if err != nil {
+				return nil, err
+			}
 
-		ops := []*wire.OutPoint{outpoint}
-		if err := b.chainConn.Rescan(blockhash, nil, ops); err != nil {
-			chainntnfs.Log.Errorf("Rescan for spend notification txout failed: %v", err)
-			return nil, err
+			ops := []*wire.OutPoint{outpoint}
+			if err := b.chainConn.Rescan(blockhash, nil, ops); err != nil {
+				chainntnfs.Log.Errorf("Rescan for spend "+
+					"notification txout failed: %v", err)
+				return nil, err
+			}
 		}
 	}