CNV-87531: k8s: add Prometheus query layer and GET /alerts

internal/managementrouter/alerts_get.go

@@ -0,0 +1,109 @@
+package managementrouter
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+
+	"github.com/openshift/monitoring-plugin/pkg/k8s"
+)
+
+type GetAlertsResponse struct {
+	Data     GetAlertsResponseData `json:"data"`
+	Warnings []string              `json:"warnings,omitempty"`
+}
+
+type GetAlertsResponseData struct {
+	Alerts []k8s.PrometheusAlert `json:"alerts"`
+}
+
+func (hr *httpRouter) GetAlerts(w http.ResponseWriter, req *http.Request) {
+	state, labels, err := parseStateAndLabels(req.URL.Query())
+	if err != nil {
+		writeError(w, http.StatusBadRequest, err.Error())
+		return
+	}
+	ctx := req.Context()
+
+	alerts, err := hr.managementClient.GetAlerts(ctx, k8s.GetAlertsRequest{
+		Labels: labels,
+		State:  state,
+	})
+	if err != nil {
+		handleError(w, err)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set("Cache-Control", "no-store")
+	w.WriteHeader(http.StatusOK)
+	if err := json.NewEncoder(w).Encode(GetAlertsResponse{
+		Data: GetAlertsResponseData{
+			Alerts: alerts,
+		},
+		Warnings: hr.alertWarnings(ctx),
+	}); err != nil {
+		log.WithError(err).Warn("failed to encode alerts response")
+	}
+}
+
+func (hr *httpRouter) alertWarnings(ctx context.Context) []string {
+	health, ok := hr.alertingHealth(ctx)
+	if !ok {
+		return nil
+	}
+
+	warnings := []string{}
+	if health.UserWorkloadEnabled && health.UserWorkload != nil {
+		warnings = append(warnings, buildRouteWarnings(health.UserWorkload.Prometheus, k8s.UserWorkloadRouteName, "user workload Prometheus")...)
+		warnings = append(warnings, buildRouteWarnings(health.UserWorkload.Alertmanager, k8s.UserWorkloadAlertmanagerRouteName, "user workload Alertmanager")...)
+	}
+
+	return warnings
+}
+
+//nolint:unused // used by the rules listing handler in a subsequent branch
+func (hr *httpRouter) rulesWarnings(ctx context.Context) []string {
+	health, ok := hr.alertingHealth(ctx)
+	if !ok {
+		return nil
+	}
+
+	if health.UserWorkloadEnabled && health.UserWorkload != nil {
+		return buildRouteWarnings(health.UserWorkload.Prometheus, k8s.UserWorkloadRouteName, "user workload Prometheus")
+	}
+
+	return nil
+}
+
+func (hr *httpRouter) alertingHealth(ctx context.Context) (k8s.AlertingHealth, bool) {
+	if hr.managementClient == nil {
+		return k8s.AlertingHealth{}, false
+	}
+
+	health, err := hr.managementClient.GetAlertingHealth(ctx)
+	if err != nil {
+		log.WithError(err).Warn("alerting health unavailable")
+		return k8s.AlertingHealth{}, false
+	}
+
+	return health, true
+}
+
+func buildRouteWarnings(route k8s.AlertingRouteHealth, expectedName string, friendlyName string) []string {
+	if route.Name != "" && route.Name != expectedName {
+		return nil
+	}
+	if route.FallbackReachable {
+		return nil
+	}
+
+	switch route.Status {
+	case k8s.RouteNotFound:
+		return []string{friendlyName + " route is missing"}
+	case k8s.RouteUnreachable:
+		return []string{friendlyName + " route is unreachable"}
+	default:
+		return nil
+	}
+}