fixing concurrent map access issue (#415)

Signed-off-by: Aaron Schlesinger <aaron@ecomaz.net>
Co-authored-by: Aaron Wislang <asw101@users.noreply.github.com>

scaler/handlers.go

@@ -73,7 +73,9 @@ func (e *impl) IsActive(
 	)
 	if !ok {
 		err := fmt.Errorf("host '%s' not found in counts", host)
-		allCounts := mergeCountsWithRoutingTable(e.pinger.counts(), e.routingTable)
+		allCounts := e.pinger.mergeCountsWithRoutingTable(
+			e.routingTable,
+		)
 		lggr.Error(err, "Given host was not found in queue count map", "host", host, "allCounts", allCounts)
 		return nil, err
 	}
@@ -173,7 +175,7 @@ func (e *impl) GetMetrics(
 			hostCount = e.pinger.aggregate()
 		} else {
 			err := fmt.Errorf("host '%s' not found in counts", host)
-			allCounts := mergeCountsWithRoutingTable(e.pinger.counts(), e.routingTable)
+			allCounts := e.pinger.mergeCountsWithRoutingTable(e.routingTable)
 			lggr.Error(err, "allCounts", allCounts)
 			return nil, err
 		}

scaler/host_counts.go

@@ -4,22 +4,6 @@ import (
 	"github.com/kedacore/http-add-on/pkg/routing"
 )
 
-// mergeCountsWithRoutingTable ensures that all hosts in routing table
-// are present in combined counts, if count is not present value is set to 0
-func mergeCountsWithRoutingTable(
-	counts map[string]int,
-	table routing.TableReader,
-) map[string]int {
-	mergedCounts := make(map[string]int)
-	for _, host := range table.Hosts() {
-		mergedCounts[host] = 0
-	}
-	for key, value := range counts {
-		mergedCounts[key] = value
-	}
-	return mergedCounts
-}
-
 // getHostCount gets proper count for given host regardless whether
 // host is in counts or only in routerTable
 func getHostCount(

scaler/host_counts_test.go

@@ -14,79 +14,66 @@ type testCase struct {
 	retCounts map[string]int
 }
 
-var cases = []testCase{
-	{
-		name: "empty queue",
-		table: newRoutingTable([]hostAndTarget{
-			{
-				host:   "www.example.com",
-				target: routing.Target{},
+func cases() []testCase {
+	return []testCase{
+		{
+			name: "empty queue",
+			table: newRoutingTable([]hostAndTarget{
+				{
+					host:   "www.example.com",
+					target: routing.Target{},
+				},
+				{
+					host:   "www.example2.com",
+					target: routing.Target{},
+				},
+			}),
+			counts: make(map[string]int),
+			retCounts: map[string]int{
+				"www.example.com":  0,
+				"www.example2.com": 0,
 			},
-			{
-				host:   "www.example2.com",
-				target: routing.Target{},
+		},
+		{
+			name: "one entry in queue, same entry in routing table",
+			table: newRoutingTable([]hostAndTarget{
+				{
+					host:   "example.com",
+					target: routing.Target{},
+				},
+			}),
+			counts: map[string]int{
+				"example.com": 1,
 			},
-		}),
-		counts: make(map[string]int),
-		retCounts: map[string]int{
-			"www.example.com":  0,
-			"www.example2.com": 0,
-		},
-	},
-	{
-		name: "one entry in queue, same entry in routing table",
-		table: newRoutingTable([]hostAndTarget{
-			{
-				host:   "example.com",
-				target: routing.Target{},
+			retCounts: map[string]int{
+				"example.com": 1,
 			},
-		}),
-		counts: map[string]int{
-			"example.com": 1,
 		},
-		retCounts: map[string]int{
-			"example.com": 1,
-		},
-	},
-	{
-		name: "one entry in queue, two in routing table",
-		table: newRoutingTable([]hostAndTarget{
-			{
-				host:   "example.com",
-				target: routing.Target{},
+		{
+			name: "one entry in queue, two in routing table",
+			table: newRoutingTable([]hostAndTarget{
+				{
+					host:   "example.com",
+					target: routing.Target{},
+				},
+				{
+					host:   "example2.com",
+					target: routing.Target{},
+				},
+			}),
+			counts: map[string]int{
+				"example.com": 1,
 			},
-			{
-				host:   "example2.com",
-				target: routing.Target{},
+			retCounts: map[string]int{
+				"example.com":  1,
+				"example2.com": 0,
 			},
-		}),
-		counts: map[string]int{
-			"example.com": 1,
 		},
-		retCounts: map[string]int{
-			"example.com":  1,
-			"example2.com": 0,
-		},
-	},
-}
-
-func TestMergeCountsWithRoutingTable(t *testing.T) {
-
-	for _, tc := range cases {
-		t.Run(tc.name, func(t *testing.T) {
-			r := require.New(t)
-			ret := mergeCountsWithRoutingTable(
-				tc.counts,
-				tc.table,
-			)
-			r.Equal(tc.retCounts, ret)
-		})
 	}
+
 }
-
 func TestGetHostCount(t *testing.T) {
-
-	for _, tc := range cases {
+	for _, tc := range cases() {
 		for host, retCount := range tc.retCounts {
 			t.Run(tc.name, func(t *testing.T) {
 				r := require.New(t)

scaler/queue_pinger.go

@@ -11,6 +11,7 @@ import (
 	"github.com/go-logr/logr"
 	"github.com/kedacore/http-add-on/pkg/k8s"
 	"github.com/kedacore/http-add-on/pkg/queue"
+	"github.com/kedacore/http-add-on/pkg/routing"
 	"github.com/pkg/errors"
 	"golang.org/x/sync/errgroup"
 )
@@ -124,6 +125,23 @@ func (q *queuePinger) counts() map[string]int {
 	return q.allCounts
 }
 
+// mergeCountsWithRoutingTable ensures that all hosts in routing table
+// are present in combined counts, if count is not present value is set to 0
+func (q *queuePinger) mergeCountsWithRoutingTable(
+	table routing.TableReader,
+) map[string]int {
+	q.pingMut.RLock()
+	defer q.pingMut.RUnlock()
+	mergedCounts := make(map[string]int)
+	for _, host := range table.Hosts() {
+		mergedCounts[host] = 0
+	}
+	for key, value := range q.allCounts {
+		mergedCounts[key] = value
+	}
+	return mergedCounts
+}
+
 func (q *queuePinger) aggregate() int {
 	q.pingMut.RLock()
 	defer q.pingMut.RUnlock()

scaler/queue_pinger_test.go

@@ -9,6 +9,7 @@ import (
 	"github.com/kedacore/http-add-on/pkg/k8s"
 	"github.com/kedacore/http-add-on/pkg/queue"
 	"github.com/stretchr/testify/require"
+	"golang.org/x/sync/errgroup"
 	v1 "k8s.io/api/core/v1"
 )
 
@@ -215,3 +216,48 @@ func TestFetchCounts(t *testing.T) {
 	}
 	r.Equal(expectedCounts, cts)
 }
+
+func TestMergeCountsWithRoutingTable(t *testing.T) {
+	for _, tc := range cases() {
+		t.Run(tc.name, func(t *testing.T) {
+			ctx := context.Background()
+			grp, ctx := errgroup.WithContext(ctx)
+			r := require.New(t)
+			const C = 100
+			tickr, q, err := newFakeQueuePinger(
+				ctx,
+				logr.Discard(),
+			)
+			r.NoError(err)
+			defer tickr.Stop()
+			q.allCounts = tc.counts
+
+			retCh := make(chan map[string]int)
+			for i := 0; i < C; i++ {
+				grp.Go(func() error {
+					retCh <- q.mergeCountsWithRoutingTable(tc.table)
+					return nil
+				})
+			}
+
+			// ensure we receive from retCh C times
+			allRets := map[int]map[string]int{}
+			for i := 0; i < C; i++ {
+				allRets[i] = <-retCh
+			}
+
+			r.NoError(grp.Wait())
+
+			// ensure that all returned maps are the
+			// same
+			prev := allRets[0]
+			for i := 1; i < C; i++ {
+				r.Equal(prev, allRets[i])
+				prev = allRets[i]
+			}
+			// ensure that all the returned maps are
+			// equal to what we expected
+			r.Equal(tc.retCounts, prev)
+		})
+	}
+}