Merge pull request #68 from dwelch0/metric-proxy-rw-lock

utilize rwlock to address race condition - add tests

pkg/proxy.go

@@ -14,7 +14,7 @@ type MetricProxyItem struct {
 
 type MetricProxy struct {
 	metrics map[string]*MetricProxyItem
-	mutex   sync.Mutex
+	mutex   sync.RWMutex
 }
 
 func NewMetricProxy() *MetricProxy {
@@ -24,6 +24,8 @@ func NewMetricProxy() *MetricProxy {
 }
 
 func (mp *MetricProxy) GetMetricById(id string) (*MetricProxyItem, error) {
+	mp.mutex.RLock()
+	defer mp.mutex.RUnlock()
 	if m, ok := mp.metrics[id]; ok {
 		if time.Since(m.creationTime).Seconds() > float64(m.ttl) {
 			return nil, errors.New("metric ttl has expired")

pkg/proxy_test.go

@@ -0,0 +1,104 @@
+package pkg
+
+import (
+	"math"
+	"reflect"
+	"testing"
+	"time"
+)
+
+func TestGetMetricById(t *testing.T) {
+	type args struct {
+		mp  *MetricProxy
+		key string
+	}
+	now := time.Now()
+	tests := []struct {
+		name string
+		args args
+		want *MetricProxyItem
+	}{
+		{
+			name: "Attempt retrieving value by providing valid id (key exists)",
+			args: args{
+				mp: &MetricProxy{
+					metrics: map[string]*MetricProxyItem{
+						"valid": &MetricProxyItem{
+							value:        "value",
+							ttl:          math.MaxInt32,
+							creationTime: now,
+						},
+					},
+				},
+				key: "valid",
+			},
+			want: &MetricProxyItem{
+				value:        "value",
+				ttl:          math.MaxInt32,
+				creationTime: now,
+			},
+		},
+		{
+			name: "Attempt retrieving value by providing valid id but ttl expired",
+			args: args{
+				mp: &MetricProxy{
+					metrics: map[string]*MetricProxyItem{
+						"expired": &MetricProxyItem{
+							value:        100,
+							ttl:          1,
+							creationTime: now,
+						},
+					},
+				},
+				key: "expired",
+			},
+			want: nil,
+		},
+	}
+
+	time.Sleep(2 * time.Second) //ensure ttl for second test expires
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got, _ := tt.args.mp.GetMetricById(tt.args.key); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("GetMetricById() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestStoreMetricById(t *testing.T) {
+	type args struct {
+		mp    *MetricProxy
+		key   string
+		value interface{}
+		ttl   int
+	}
+	tests := []struct {
+		name string
+		args args
+		want *MetricProxyItem
+	}{
+		{
+			name: "Attempt storing new metric by id",
+			args: args{
+				mp:    NewMetricProxy(),
+				key:   "new",
+				value: 1,
+				ttl:   math.MaxInt32,
+			},
+			want: &MetricProxyItem{
+				value: 1,
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			tt.args.mp.StoreMetricById(tt.args.key, tt.args.value, tt.args.ttl)
+			if got, err := tt.args.mp.GetMetricById(tt.args.key); got.value != tt.want.value || err != nil {
+				t.Errorf("StoreMetricById() = %v, want %v", got.value, tt.want.value)
+			}
+		})
+	}
+}