use istio client-go library instead of knative (#1661)

use istio client-go library instead of knative
bump kubernetes dependency version
change code coverage to codecov

vendor/github.com/prometheus/client_golang/api/prometheus/v1/api.go

@@ -11,8 +11,6 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// +build go1.7
-
 // Package v1 provides bindings to the Prometheus HTTP API v1:
 // http://prometheus.io/docs/querying/api/
 package v1
@@ -35,6 +33,7 @@ const (
 
 	apiPrefix = "/api/v1"
 
+	epAlerts          = apiPrefix + "/alerts"
 	epAlertManagers   = apiPrefix + "/alertmanagers"
 	epQuery           = apiPrefix + "/query"
 	epQueryRange      = apiPrefix + "/query_range"
@@ -115,6 +114,8 @@ type Range struct {
 
 // API provides bindings for Prometheus's v1 API.
 type API interface {
+	// Alerts returns a list of all active alerts.
+	Alerts(ctx context.Context) (AlertsResult, error)
 	// AlertManagers returns an overview of the current state of the Prometheus alert manager discovery.
 	AlertManagers(ctx context.Context) (AlertManagersResult, error)
 	// CleanTombstones removes the deleted data from disk and cleans up the existing tombstones.
@@ -142,6 +143,11 @@ type API interface {
 	Targets(ctx context.Context) (TargetsResult, error)
 }
 
+// AlertsResult contains the result from querying the alerts endpoint.
+type AlertsResult struct {
+	Alerts []Alert `json:"alerts"`
+}
+
 // AlertManagersResult contains the result from querying the alertmanagers endpoint.
 type AlertManagersResult struct {
 	Active  []AlertManager `json:"activeAlertManagers"`
@@ -402,6 +408,24 @@ type httpAPI struct {
 	client api.Client
 }
 
+func (h *httpAPI) Alerts(ctx context.Context) (AlertsResult, error) {
+	u := h.client.URL(epAlerts, nil)
+
+	req, err := http.NewRequest(http.MethodGet, u.String(), nil)
+	if err != nil {
+		return AlertsResult{}, err
+	}
+
+	_, body, err := h.client.Do(ctx, req)
+	if err != nil {
+		return AlertsResult{}, err
+	}
+
+	var res AlertsResult
+	err = json.Unmarshal(body, &res)
+	return res, err
+}
+
 func (h *httpAPI) AlertManagers(ctx context.Context) (AlertManagersResult, error) {
 	u := h.client.URL(epAlertManagers, nil)
 
@@ -514,14 +538,7 @@ func (h *httpAPI) Query(ctx context.Context, query string, ts time.Time) (model.
 		q.Set("time", ts.Format(time.RFC3339Nano))
 	}
 
-	u.RawQuery = q.Encode()
-
-	req, err := http.NewRequest(http.MethodGet, u.String(), nil)
-	if err != nil {
-		return nil, err
-	}
-
-	_, body, err := h.client.Do(ctx, req)
+	_, body, err := api.DoGetFallback(h.client, ctx, u, q)
 	if err != nil {
 		return nil, err
 	}
@@ -547,14 +564,7 @@ func (h *httpAPI) QueryRange(ctx context.Context, query string, r Range) (model.
 	q.Set("end", end)
 	q.Set("step", step)
 
-	u.RawQuery = q.Encode()
-
-	req, err := http.NewRequest(http.MethodGet, u.String(), nil)
-	if err != nil {
-		return nil, err
-	}
-
-	_, body, err := h.client.Do(ctx, req)
+	_, body, err := api.DoGetFallback(h.client, ctx, u, q)
 	if err != nil {
 		return nil, err
 	}