create metrics query functions

internal/kubernetes/prometheus/metrics.go

@@ -0,0 +1,79 @@
+package metrics
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	v1 "k8s.io/api/core/v1"
+	"k8s.io/client-go/kubernetes"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+)
+
+// returns the prometheus service name
+func GetPrometheusService(clientset *kubernetes.Clientset) (*v1.Service, bool, error) {
+	services, err := clientset.CoreV1().Services("").List(context.TODO(), metav1.ListOptions{
+		LabelSelector: "app=prometheus,component=server,heritage=Helm",
+	})
+
+	if err != nil {
+		return nil, false, err
+	}
+
+	if len(services.Items) == 0 {
+		return nil, false, nil
+	}
+
+	return &services.Items[0], true, nil
+}
+
+type QueryOpts struct {
+	Metric     string   `json:"metric"`
+	ShouldSum  bool     `json:"should_sum"`
+	PodList    []string `json:"pods"`
+	Namespace  string   `json:"namespace"`
+	StartRange uint     `json:"start_range"`
+	EndRange   uint     `json:"end_range"`
+	Resolution string   `json:"resolution"`
+}
+
+func QueryPrometheus(
+	clientset *kubernetes.Clientset,
+	service *v1.Service,
+	opts *QueryOpts,
+) ([]byte, error) {
+	if len(service.Spec.Ports) == 0 {
+		return nil, fmt.Errorf("prometheus service has no exposed ports to query")
+	}
+
+	podSelector := fmt.Sprintf(`namespace="%s",pod=~"%s",container!="POD",container!=""`, opts.Namespace, strings.Join(opts.PodList, "|"))
+	query := ""
+
+	if opts.Metric == "cpu" {
+		query = fmt.Sprintf("rate(container_cpu_usage_seconds_total{%s}[5m])", podSelector)
+	} else if opts.Metric == "memory" {
+		query = fmt.Sprintf("container_memory_usage_bytes{%s}", podSelector)
+	}
+
+	if opts.ShouldSum {
+		query = fmt.Sprintf("sum(%s)", query)
+	}
+
+	queryParams := map[string]string{
+		"query": query,
+		"start": fmt.Sprintf("%d", opts.StartRange),
+		"end":   fmt.Sprintf("%d", opts.EndRange),
+		"step":  opts.Resolution,
+	}
+
+	resp := clientset.CoreV1().Services(service.Namespace).ProxyGet(
+		"http",
+		service.Name,
+		fmt.Sprintf("%d", service.Spec.Ports[0].Port),
+		"/api/v1/query_range",
+		queryParams,
+	)
+
+	return resp.DoRaw(context.TODO())
+}