From 4fd1f832d72914742ed1a56cb5b79ff39c0d7a1f Mon Sep 17 00:00:00 2001
From: Olaoluwa Osuntokun <laolu32@gmail.com>
Date: Fri, 4 Jan 2019 14:59:04 -0800
Subject: [PATCH] contractcourt+rpc: use new FetchChannel method instead of
 scanning

In this commit, we modify areas where we need to force close a channel
to use the new FetchChannel method instead of manually scanning. This
dramatically reduces the CPU usage when doing things like closing a
large number of channels within lnd.
---
 contractcourt/chain_arbitrator.go | 15 +-------------
 rpcserver.go                      | 33 ++-----------------------------
 2 files changed, 3 insertions(+), 45 deletions(-)

diff --git a/contractcourt/chain_arbitrator.go b/contractcourt/chain_arbitrator.go
index 696b4636..6652df23 100644
--- a/contractcourt/chain_arbitrator.go
+++ b/contractcourt/chain_arbitrator.go
@@ -224,23 +224,10 @@ func newActiveChannelArbitrator(channel *channeldb.OpenChannel,
 			// With the channels fetched, attempt to locate
 			// the target channel according to its channel
 			// point.
-			dbChannels, err := c.chanSource.FetchAllChannels()
+			channel, err := c.chanSource.FetchChannel(chanPoint)
 			if err != nil {
 				return nil, err
 			}
-			var channel *channeldb.OpenChannel
-			for _, dbChannel := range dbChannels {
-				if dbChannel.FundingOutpoint == chanPoint {
-					channel = dbChannel
-					break
-				}
-			}
-
-			// If the channel cannot be located, then we
-			// exit with an error to the channel.
-			if channel == nil {
-				return nil, fmt.Errorf("unable to find channel")
-			}
 
 			chanMachine, err := lnwallet.NewLightningChannel(
 				c.cfg.Signer, c.cfg.PreimageDB, channel, nil,
diff --git a/rpcserver.go b/rpcserver.go
index f992023d..46be68e8 100644
--- a/rpcserver.go
+++ b/rpcserver.go
@@ -1709,7 +1709,7 @@ func (r *rpcServer) AbandonChannel(ctx context.Context,
 	// With the chanPoint constructed, we'll attempt to find the target
 	// channel in the database. If we can't find the channel, then we'll
 	// return the error back to the caller.
-	dbChan, err := r.fetchOpenDbChannel(*chanPoint)
+	dbChan, err := r.server.chanDB.FetchChannel(*chanPoint)
 	if err != nil {
 		return nil, err
 	}
@@ -1746,42 +1746,13 @@ func (r *rpcServer) AbandonChannel(ctx context.Context,
 	return &lnrpc.AbandonChannelResponse{}, nil
 }
 
-// fetchOpenDbChannel attempts to locate a channel identified by its channel
-// point from the database's set of all currently opened channels.
-func (r *rpcServer) fetchOpenDbChannel(chanPoint wire.OutPoint) (
-	*channeldb.OpenChannel, error) {
-
-	dbChannels, err := r.server.chanDB.FetchAllChannels()
-	if err != nil {
-		return nil, err
-	}
-
-	// With the channels fetched, attempt to locate the target channel
-	// according to its channel point.
-	var dbChan *channeldb.OpenChannel
-	for _, dbChannel := range dbChannels {
-		if dbChannel.FundingOutpoint == chanPoint {
-			dbChan = dbChannel
-			break
-		}
-	}
-
-	// If the channel cannot be located, then we exit with an error to the
-	// caller.
-	if dbChan == nil {
-		return nil, fmt.Errorf("unable to find channel")
-	}
-
-	return dbChan, nil
-}
-
 // fetchActiveChannel attempts to locate a channel identified by its channel
 // point from the database's set of all currently opened channels and
 // return it as a fully populated state machine
 func (r *rpcServer) fetchActiveChannel(chanPoint wire.OutPoint) (
 	*lnwallet.LightningChannel, error) {
 
-	dbChan, err := r.fetchOpenDbChannel(chanPoint)
+	dbChan, err := r.server.chanDB.FetchChannel(chanPoint)
 	if err != nil {
 		return nil, err
 	}