more otel

internal/prometheus/client.go

@@ -0,0 +1,103 @@
+// Package prometheus provides optional Prometheus range queries for rollout impact.
+package prometheus
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/url"
+	"os"
+	"strconv"
+	"strings"
+	"time"
+)
+
+type Point struct {
+	Timestamp float64 `json:"timestamp"`
+	Value     string  `json:"value"`
+}
+
+type Client struct {
+	baseURL       string
+	queryTemplate string
+	httpClient    *http.Client
+}
+
+func NewFromEnv() *Client {
+	baseURL := strings.TrimRight(os.Getenv("OTEL_PROMETHEUS_URL"), "/")
+	if baseURL == "" {
+		return nil
+	}
+	query := os.Getenv("OTEL_PROMETHEUS_ERROR_QUERY")
+	if query == "" {
+		query = `sum(rate(http_server_requests_total{service_name=%q,http_response_status_code=~"5.."}[5m]))`
+	}
+	return &Client{baseURL: baseURL, queryTemplate: query, httpClient: &http.Client{Timeout: 10 * time.Second}}
+}
+
+func (c *Client) Configured() bool { return c != nil }
+
+func (c *Client) ErrorRate(ctx context.Context, service, release string, start, end time.Time) ([]Point, error) {
+	if c == nil {
+		return nil, fmt.Errorf("prometheus is not configured")
+	}
+	query := renderQuery(c.queryTemplate, service, release)
+	params := url.Values{
+		"query": {query},
+		"start": {strconv.FormatInt(start.Unix(), 10)},
+		"end":   {strconv.FormatInt(end.Unix(), 10)},
+		"step":  {"300"},
+	}
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, c.baseURL+"/api/v1/query_range?"+params.Encode(), nil)
+	if err != nil {
+		return nil, err
+	}
+	response, err := c.httpClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer response.Body.Close()
+	if response.StatusCode/100 != 2 {
+		return nil, fmt.Errorf("prometheus returned HTTP %s", response.Status)
+	}
+	var payload struct {
+		Status string `json:"status"`
+		Error  string `json:"error"`
+		Data   struct {
+			Result []struct {
+				Values [][]json.RawMessage `json:"values"`
+			} `json:"result"`
+		} `json:"data"`
+	}
+	if err := json.NewDecoder(response.Body).Decode(&payload); err != nil {
+		return nil, err
+	}
+	if payload.Status != "success" {
+		return nil, fmt.Errorf("prometheus query failed: %s", payload.Error)
+	}
+	points := make([]Point, 0)
+	for _, series := range payload.Data.Result {
+		for _, value := range series.Values {
+			if len(value) != 2 {
+				continue
+			}
+			var timestamp float64
+			var sample string
+			if json.Unmarshal(value[0], &timestamp) == nil && json.Unmarshal(value[1], &sample) == nil {
+				points = append(points, Point{Timestamp: timestamp, Value: sample})
+			}
+		}
+	}
+	return points, nil
+}
+
+func renderQuery(template, service, release string) string {
+	values := []string{strconv.Quote(service), strconv.Quote(release)}
+	for _, value := range values {
+		if strings.Contains(template, "%q") {
+			template = strings.Replace(template, "%q", value, 1)
+		}
+	}
+	return template
+}