feat(go): add capacity health check tool

go/vehicle-gateway/cmd/capacity-check/main.go

@@ -0,0 +1,109 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"os"
+	"strings"
+	"time"
+
+	"lingniu-vehicle-ingest/go/vehicle-gateway/internal/capacity"
+)
+
+const defaultEndpoints = "gateway=http://127.0.0.1:20211,history=http://127.0.0.1:20212,stat=http://127.0.0.1:20213,bridge=http://127.0.0.1:20214,realtime=http://127.0.0.1:20200,fast-writer=http://127.0.0.1:20215"
+
+type endpoint struct {
+	Name string
+	URL  string
+}
+
+func main() {
+	var rawEndpoints string
+	var timeout time.Duration
+	flag.StringVar(&rawEndpoints, "endpoints", defaultEndpoints, "comma separated name=url endpoints; /metrics is appended when no path is provided")
+	flag.DurationVar(&timeout, "timeout", 2*time.Second, "per endpoint timeout")
+	flag.Parse()
+
+	ctx, cancel := context.WithTimeout(context.Background(), timeout)
+	defer cancel()
+
+	metricsByService, findings := collectMetrics(ctx, parseEndpoints(rawEndpoints), timeout)
+	report := capacity.Evaluate(metricsByService)
+	report.Findings = append(report.Findings, findings...)
+	if len(report.Findings) > 0 {
+		report.Status = capacity.StatusDegraded
+	}
+	encoder := json.NewEncoder(os.Stdout)
+	encoder.SetIndent("", "  ")
+	_ = encoder.Encode(report)
+	if report.Status != capacity.StatusOK {
+		os.Exit(2)
+	}
+}
+
+func parseEndpoints(value string) []endpoint {
+	var endpoints []endpoint
+	for _, item := range strings.Split(value, ",") {
+		item = strings.TrimSpace(item)
+		if item == "" {
+			continue
+		}
+		name, url, ok := strings.Cut(item, "=")
+		if !ok {
+			continue
+		}
+		name = strings.TrimSpace(name)
+		url = withMetricsPath(strings.TrimSpace(url))
+		if name == "" || url == "" {
+			continue
+		}
+		endpoints = append(endpoints, endpoint{Name: name, URL: url})
+	}
+	return endpoints
+}
+
+func withMetricsPath(value string) string {
+	parsed, err := url.Parse(value)
+	if err != nil || parsed.Scheme == "" || parsed.Host == "" {
+		return value
+	}
+	if parsed.Path == "" || parsed.Path == "/" {
+		parsed.Path = "/metrics"
+	}
+	return parsed.String()
+}
+
+func collectMetrics(ctx context.Context, endpoints []endpoint, timeout time.Duration) (map[string]string, []string) {
+	client := &http.Client{Timeout: timeout}
+	metricsByService := make(map[string]string, len(endpoints))
+	var findings []string
+	for _, ep := range endpoints {
+		request, err := http.NewRequestWithContext(ctx, http.MethodGet, ep.URL, nil)
+		if err != nil {
+			findings = append(findings, fmt.Sprintf("%s metrics request invalid: %v", ep.Name, err))
+			continue
+		}
+		response, err := client.Do(request)
+		if err != nil {
+			findings = append(findings, fmt.Sprintf("%s metrics fetch failed: %v", ep.Name, err))
+			continue
+		}
+		body, readErr := io.ReadAll(response.Body)
+		_ = response.Body.Close()
+		if readErr != nil {
+			findings = append(findings, fmt.Sprintf("%s metrics read failed: %v", ep.Name, readErr))
+			continue
+		}
+		if response.StatusCode < 200 || response.StatusCode >= 300 {
+			findings = append(findings, fmt.Sprintf("%s metrics status %d", ep.Name, response.StatusCode))
+			continue
+		}
+		metricsByService[ep.Name] = string(body)
+	}
+	return metricsByService, findings
+}