Fix: handle invalid endpoint

closest/regions.go

@@ -11,7 +11,8 @@ import (
 const measureRepeats = 5
 
 var (
-	errEndpointsUnavailable = errors.New("service endpoints are unavailable")
+	errAllEndpointsUnavailable            = errors.New("all service endpoints are unavailable")
+	errRegionalServiceEndpointUnavailable = errors.New("regional service endpoint is unavailable")
 
 	httpClient = http.Client{Timeout: 30 * time.Second}
 )
@@ -38,7 +39,7 @@ func (r *Regions) FindClosest(endpoints Endpoints) (string, error) {
 	}
 
 	if len(latencies) == 0 {
-		return "", errEndpointsUnavailable
+		return "", errAllEndpointsUnavailable
 	}
 
 	theRegion, theLatency := r.regionWithLowestLatency(latencies)
@@ -65,6 +66,10 @@ func (r *Regions) measureLatency(endpoint string) (time.Duration, error) {
 			response.Body.Close()
 		}
 	}
+
+	if c == 0 {
+		return -1, errRegionalServiceEndpointUnavailable
+	}
 	return time.Duration(sum / c), nil
 }
 

closest/regions_test.go

@@ -0,0 +1,52 @@
+package closest
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestRegions_FindClosest_ValidEndpoints(t *testing.T) {
+	// given
+	regions := new(Regions)
+	endpoints := Endpoints{}
+	endpoints["slower_endpoint"] = "http://httpbin.org/delay/3"
+	endpoints["slow_endpoint"] = "http://httpbin.org/delay/1"
+	endpoints["slowest_endpoint"] = "http://httpbin.org/delay/5"
+
+	// when
+	region, err := regions.FindClosest(endpoints)
+
+	// then
+	assert.Equal(t, "slow_endpoint", region, "faster region should be reported")
+	assert.Nil(t, err, "no error should be returned")
+}
+
+func TestRegions_FindClosest_BothValidInvalidEndpoints(t *testing.T) {
+	// given
+	regions := new(Regions)
+	endpoints := Endpoints{}
+	endpoints["slow_endpoint"] = "http://httpbin.org/delay/1"
+	endpoints["wrong_endpoint"] = "http://localhost:57585"
+
+	// when
+	region, err := regions.FindClosest(endpoints)
+
+	// then
+	assert.Equal(t, "slow_endpoint", region, "faster region should be reported")
+	assert.Nil(t, err, "no error should be returned")
+}
+
+func TestRegions_FindClosest_InvalidEndpoints(t *testing.T) {
+	// given
+	regions := new(Regions)
+	endpoints := Endpoints{}
+	endpoints["wrong_endpoint"] = "http://localhost:69695"
+
+	// when
+	region, err := regions.FindClosest(endpoints)
+
+	// then
+	assert.NotNil(t, err, "an error should be returned")
+	assert.Empty(t, region, "no endpoint should be returned")
+}