fix: repeated file generation on every metrics test running (#3077)

* fix: repeated file generation on every metrics test running

Signed-off-by: ShyunnY <[email protected]>

* add comments && fix issues

Signed-off-by: ShyunnY <[email protected]>

---------

Signed-off-by: ShyunnY <[email protected]>

internal/metrics/metrics_test.go

@@ -0,0 +1,274 @@
+// Copyright Envoy Gateway Authors
+// SPDX-License-Identifier: Apache-2.0
+// The full text of the Apache license is available in the LICENSE file at
+// the root of the repo.
+
+package metrics
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+	"reflect"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/exporters/stdout/stdoutmetric"
+	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/metric/metricdata"
+	"go.opentelemetry.io/otel/sdk/resource"
+	semconv "go.opentelemetry.io/otel/semconv/v1.17.0"
+)
+
+var (
+	overrideTestData = flag.Bool("override-testdata", false, "if override the test output data.")
+)
+
+func TestCounter(t *testing.T) {
+
+	name := "counter_metric"
+
+	var writer io.ReadWriter = bytes.NewBuffer(nil)
+	writer, err := exporterWriter(name, writer)
+	require.NoError(t, err)
+
+	counterProvider, err := newTestMetricsProvider("Counter", writer)
+	require.NoError(t, err)
+
+	// simulate a function that builds an indicator and changes its value
+	metricsFunc := []func(){
+		func() {
+			metricName := "ir_updates_total"
+			description := "Total Number of IR updates, by ir type"
+
+			irCounter := NewCounter(
+				metricName,
+				description,
+			)
+
+			// increment on every xds ir update
+			irCounter.With(NewLabel("ir-type").Value("xds")).Increment()
+			// xds ir updates double
+			irCounter.With(NewLabel("ir-type").Value("xds")).Add(2)
+		},
+		func() {
+			name := "watchable_subscribed_total"
+			description := "Total Number of IR updates, by ir type"
+
+			subCounter := NewCounter(
+				name,
+				description,
+			)
+
+			// increment on every xds ir subscribed
+			subCounter.With(NewLabel("ir-type").Value("xds")).Add(2)
+			// xds ir updates double
+			subCounter.With(NewLabel("ir-type").Value("xds")).Add(5)
+		},
+	}
+	for _, f := range metricsFunc {
+		f()
+	}
+
+	// Ensure that metrics data can be flushed by closing the provider
+	err = counterProvider.Shutdown(context.Background())
+	require.NoError(t, err)
+
+	loadMetricsFile(t, name, writer)
+}
+
+func TestGauge(t *testing.T) {
+
+	name := "gauge_metric"
+
+	var writer io.ReadWriter = bytes.NewBuffer(nil)
+	writer, err := exporterWriter(name, writer)
+	require.NoError(t, err)
+
+	gaugeProvider, err := newTestMetricsProvider("Gauge", writer)
+	require.NoError(t, err)
+
+	// simulate a function that builds an indicator and changes its value
+	metricsFunc := []func(){
+		func() {
+			metricName := "current_irs_queue_num"
+			description := "current number of ir in queue, by ir type"
+
+			currentIRsNum := NewGauge(
+				metricName,
+				description,
+			)
+
+			// only the last recorded value (2) will be exported for this gauge
+			currentIRsNum.With(NewLabel("ir-type").Value("xds")).Record(1)
+			currentIRsNum.With(NewLabel("ir-type").Value("xds")).Record(3)
+			currentIRsNum.With(NewLabel("ir-type").Value("xds")).Record(2)
+
+			currentIRsNum.With(NewLabel("ir-type").Value("xds")).Record(1)
+			currentIRsNum.With(NewLabel("ir-type").Value("xds")).Record(3)
+			currentIRsNum.With(NewLabel("ir-type").Value("xds")).Record(2)
+		},
+	}
+	for _, f := range metricsFunc {
+		f()
+	}
+
+	// Ensure that metrics data can be flushed by closing the provider
+	err = gaugeProvider.Shutdown(context.Background())
+	require.NoError(t, err)
+
+	loadMetricsFile(t, name, writer)
+}
+
+func TestHistogram(t *testing.T) {
+
+	name := "histogram_metric"
+
+	var writer io.ReadWriter = bytes.NewBuffer(nil)
+	writer, err := exporterWriter(name, writer)
+	require.NoError(t, err)
+
+	histogramProvider, err := newTestMetricsProvider("Histogram", writer)
+	require.NoError(t, err)
+
+	// simulate a function that builds an indicator and changes its value
+	metricsFunc := []func(){
+		func() {
+			metricName := "sent_bytes_total"
+			description := "Histogram of sent bytes by method"
+
+			sentBytes := NewHistogram(
+				metricName,
+				description,
+				[]float64{10, 50, 100, 1000, 10000},
+				WithUnit(Bytes),
+			)
+
+			// This will hit Bounds of 25,500 and 2500
+			sentBytes.With(NewLabel("method").Value("/request/path/1")).Record(20)
+			sentBytes.With(NewLabel("method").Value("/request/path/1")).Record(458)
+			sentBytes.With(NewLabel("method").Value("/request/path/1")).Record(2000)
+		},
+	}
+	for _, f := range metricsFunc {
+		f()
+	}
+
+	// Ensure that metrics data can be flushed by closing the provider
+	err = histogramProvider.Shutdown(context.Background())
+	require.NoError(t, err)
+
+	loadMetricsFile(t, name, writer)
+}
+
+// newTestMetricsProvider Create an OTEL Metrics Provider for testing use only
+func newTestMetricsProvider(metricType string, writer io.Writer) (*metric.MeterProvider, error) {
+	enc := json.NewEncoder(writer)
+	enc.SetIndent("", "  ")
+
+	stdExp, err := stdoutmetric.New(
+		stdoutmetric.WithEncoder(
+			&jsonEncoderWithoutTime{
+				encoder: enc,
+			},
+		),
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	p := metric.NewMeterProvider(
+		metric.WithReader(metric.NewPeriodicReader(stdExp)),
+		metric.WithResource(resource.NewSchemaless(
+			semconv.ServiceName("test"),
+			attribute.String("metric.type", metricType),
+		)),
+	)
+	otel.SetMeterProvider(p)
+
+	return p, nil
+}
+
+func loadMetricsFile(t *testing.T, name string, reader io.Reader) {
+	if !*overrideTestData {
+		fname := fmt.Sprintf("testdata/%s.json", name)
+
+		// nolint:gosec
+		f, err := os.ReadFile(fname)
+		require.NoError(t, err)
+
+		actual := reader.(*bytes.Buffer).String()
+		// we set the json encoder indent, so we need to remove the "\r" from the read file
+		expect := strings.ReplaceAll(string(f), "\r", "")
+
+		require.Equal(t, expect, actual)
+	}
+}
+
+func exporterWriter(name string, origin io.ReadWriter) (io.ReadWriter, error) {
+	if *overrideTestData {
+		fname := fmt.Sprintf("testdata/%s.json", name)
+
+		// nolint:gosec
+		f, err := os.OpenFile(fname, os.O_CREATE|os.O_RDWR, 0644)
+		if err != nil {
+			return nil, err
+		}
+		return f, nil
+	}
+
+	return origin, nil
+}
+
+// jsonEncoderWithoutTime Is a JSON Encoder that zeroed out the ResourceMetrics time
+// WARNING: This can only be used in the ResourceMetrics serialization when testing a metric!
+type jsonEncoderWithoutTime struct {
+	encoder *json.Encoder
+}
+
+func (enc *jsonEncoderWithoutTime) Encode(v any) error {
+	data, ok := v.(*metricdata.ResourceMetrics)
+	if !ok {
+		return fmt.Errorf("object of type %T is not ResourceMetrics", data)
+	}
+
+	// Since to the presence of time information in metrics, it prevents us from performing comparisons.
+	// In practice, when testing whether metrics are output as expected,
+	// we are not overly concerned with the value of time,
+	// but rather focus on the attributes and values of the metrics.
+	// In serialization, we always set the Time/StartTime fields to zero value.
+	for _, sm := range data.ScopeMetrics {
+		for _, m := range sm.Metrics {
+			val := reflect.ValueOf(m.Data).FieldByName("DataPoints")
+			for i := 0; i < val.Len(); i++ {
+				field := val.Index(i)
+				if exist := func(reflect.Value) bool {
+					var updated bool
+					if !field.FieldByName("Time").IsZero() && field.IsValid() && field.CanSet() {
+						field.FieldByName("Time").Set(reflect.ValueOf(time.Time{}))
+						updated = true
+					}
+					if !field.FieldByName("StartTime").IsZero() && field.IsValid() && field.CanSet() {
+						field.FieldByName("StartTime").Set(reflect.ValueOf(time.Time{}))
+						updated = true
+					}
+					return updated
+				}(field); !exist {
+					return errors.New("failed to set the Time or StartTime field value")
+				}
+
+			}
+		}
+	}
+
+	return enc.encoder.Encode(data)
+}