introduce metric naming test (#3789)

* introduce metric naming test

Signed-off-by: zounengren <zounengren@cmss.chinamobile.com>

* Update metrics.go

Signed-off-by: zounengren <zounengren@cmss.chinamobile.com>

test/metric_naming_test.go

@@ -0,0 +1,172 @@
+package test
+
+import (
+	"bytes"
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/coredns/coredns/plugin"
+
+	dto "github.com/prometheus/client_model/go"
+	"github.com/prometheus/common/expfmt"
+	"github.com/prometheus/prometheus/util/promlint"
+)
+
+func TestMetricNaming(t *testing.T) {
+
+	walker := validMetricWalker{}
+	err := filepath.Walk("..", walker.walk)
+
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(walker.Metrics) > 0 {
+
+		buf := &bytes.Buffer{}
+		encoder := expfmt.NewEncoder(buf, expfmt.FmtText)
+		for _, mf := range walker.Metrics {
+			if err := encoder.Encode(mf); err != nil {
+				t.Fatalf("Encoding and sending metric family: %s", err)
+			}
+		}
+
+		l := promlint.New(buf)
+		problems, err := l.Lint()
+		if err != nil {
+			t.Fatalf("Link found error: %s", err)
+		}
+
+		if len(problems) > 0 {
+			t.Fatalf("A slice of Problems indicating any issues found in the metrics stream: %s", problems)
+		}
+	}
+
+}
+
+type validMetricWalker struct {
+	Metrics []*dto.MetricFamily
+}
+
+func (w *validMetricWalker) walk(path string, info os.FileInfo, _ error) error {
+	// only for regular files, not starting with a . and those that are go files.
+	if !info.Mode().IsRegular() {
+		return nil
+	}
+	// Is it appropriate to compare the file name equals metrics.go directly？
+	if strings.HasPrefix(path, "../.") {
+		return nil
+	}
+	if strings.HasSuffix(path, "_test.go") {
+		return nil
+	}
+	if !strings.HasSuffix(path, ".go") {
+		return nil
+	}
+
+	fs := token.NewFileSet()
+	f, err := parser.ParseFile(fs, path, nil, parser.AllErrors)
+	if err != nil {
+		return err
+	}
+	l := &metric{}
+	ast.Walk(l, f)
+	if l.Metric != nil {
+		w.Metrics = append(w.Metrics, l.Metric)
+	}
+	return nil
+}
+
+type metric struct {
+	Metric *dto.MetricFamily
+}
+
+func (l metric) Visit(n ast.Node) ast.Visitor {
+	if n == nil {
+		return nil
+	}
+	ce, ok := n.(*ast.CallExpr)
+	if !ok {
+		return l
+	}
+	se, ok := ce.Fun.(*ast.SelectorExpr)
+	if !ok {
+		return l
+	}
+	id, ok := se.X.(*ast.Ident)
+	if !ok {
+		return l
+	}
+	if id.Name != "prometheus" { //prometheus
+		return l
+	}
+	var metricsType dto.MetricType
+	switch se.Sel.Name {
+	case "NewCounterVec", "NewCounter":
+		metricsType = dto.MetricType_COUNTER
+	case "NewGaugeVec", "NewGauge":
+		metricsType = dto.MetricType_GAUGE
+	case "NewHistogramVec", "NewHistogram":
+		metricsType = dto.MetricType_HISTOGRAM
+	case "NewSummaryVec", "NewSummary":
+		metricsType = dto.MetricType_SUMMARY
+	default:
+		return l
+	}
+	// Check first arg, that should have basic lit with capital
+	if len(ce.Args) < 1 {
+		return l
+	}
+	bl, ok := ce.Args[0].(*ast.CompositeLit)
+	if !ok {
+		return l
+	}
+
+	// parse Namespace Subsystem Name Help
+	var subsystem, name, help string
+	for _, elt := range bl.Elts {
+		expr, ok := elt.(*ast.KeyValueExpr)
+		if !ok {
+			continue
+		}
+		object, ok := expr.Key.(*ast.Ident)
+		if !ok {
+			continue
+		}
+		value, ok := expr.Value.(*ast.BasicLit)
+		if !ok {
+			continue
+		}
+		switch object.Name {
+		case "Subsystem":
+			subsystem = value.Value
+		case "Name":
+			name = value.Value
+		case "Help":
+			help = value.Value
+		}
+	}
+
+	// validate metrics field
+	if len(name) == 0 || len(help) == 0 {
+		return l
+	}
+
+	var metricName string
+	if len(subsystem) > 0 {
+		metricName = strings.Join([]string{plugin.Namespace, subsystem, name}, "_")
+	} else {
+		metricName = strings.Join([]string{plugin.Namespace, name}, "_")
+	}
+	l.Metric = &dto.MetricFamily{
+		Name: &metricName,
+		Help: &help,
+		Type: &metricsType,
+	}
+	return l
+}