From b424d3644064f8de9c0616c15d70fcbffe2e56bc Mon Sep 17 00:00:00 2001
From: Yuri Shkuro <github@ysh.us>
Date: Wed, 13 Jan 2021 20:01:52 -0500
Subject: [PATCH] cleanup

Signed-off-by: Yuri Shkuro <github@ysh.us>
---
 pkg/discovery/grpcresolver/grpc_resolver.go   | 27 ++++++++++---------
 .../grpcresolver/grpc_resolver_test.go        |  7 +++--
 2 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/pkg/discovery/grpcresolver/grpc_resolver.go b/pkg/discovery/grpcresolver/grpc_resolver.go
index eee40732df4..2329870f7ca 100644
--- a/pkg/discovery/grpcresolver/grpc_resolver.go
+++ b/pkg/discovery/grpcresolver/grpc_resolver.go
@@ -123,22 +123,25 @@ func (r *Resolver) Close() {
 	r.closing.Wait()
 }
 
+// rendezvousHash is the core of the algorithm. It takes input addresses,
+// assigns each of them a hash, sorts them by those hash values, and
+// returns top N of entries from the sorted list, up to minPeers parameter.
 func (r *Resolver) rendezvousHash(addresses []string) []string {
 	hasher := fnv.New32()
-	hosts := hostScores{}
-	for _, address := range addresses {
-		hosts = append(hosts, hostScore{
+	hosts := make(hostScores, len(addresses))
+	for i, address := range addresses {
+		hosts[i] = hostScore{
 			address: address,
 			score:   hashAddr(hasher, []byte(address), r.salt),
-		})
+		}
 	}
 	sort.Sort(hosts)
-	size := min(r.discoveryMinPeers, len(hosts))
-	topAddrs := make([]string, size)
-	for i := 0; i < size; i++ {
-		topAddrs[i] = hosts[i].address
+	n := min(r.discoveryMinPeers, len(hosts))
+	topN := make([]string, n)
+	for i := 0; i < n; i++ {
+		topN[i] = hosts[i].address
 	}
-	return topAddrs
+	return topN
 }
 
 func min(a, b int) int {
@@ -162,9 +165,9 @@ func (r *Resolver) updateAddresses(hostPorts []string) {
 }
 
 func generateAddresses(instances []string) []resolver.Address {
-	var addrs []resolver.Address
-	for _, instance := range instances {
-		addrs = append(addrs, resolver.Address{Addr: instance})
+	addrs := make([]resolver.Address, len(instances))
+	for i, instance := range instances {
+		addrs[i] = resolver.Address{Addr: instance}
 	}
 	return addrs
 }
diff --git a/pkg/discovery/grpcresolver/grpc_resolver_test.go b/pkg/discovery/grpcresolver/grpc_resolver_test.go
index 32fc94b1179..93c32e7c823 100644
--- a/pkg/discovery/grpcresolver/grpc_resolver_test.go
+++ b/pkg/discovery/grpcresolver/grpc_resolver_test.go
@@ -136,10 +136,13 @@ func TestGRPCResolverRoundRobin(t *testing.T) {
 		minPeers    int
 		connections int // expected number of unique connections to servers
 	}{
-		{3, 3}, {5, 5}, {7, 5},
+		{minPeers: 3, connections: 3},
+		{minPeers: 5, connections: 3},
+		// note: test cannot succeed with minPeers < connections because resolver
+		// will never return more than minPeers addresses.
 	}
 	for _, test := range tests {
-		t.Run(fmt.Sprintf("minPeers=%d", test.minPeers), func(t *testing.T) {
+		t.Run(fmt.Sprintf("%+v", test), func(t *testing.T) {
 			res := New(notifier, discoverer, zap.NewNop(), test.minPeers)
 			defer resolver.UnregisterForTesting(res.Scheme())