Don't record data points when metric config is not initialized yet (#1323)

* do not record for empty metric config

* Revert "do not record for empty metric config"

This reverts commit 539a5e4dbb.

* dont record

* add comment

metrics/config.go

@@ -21,6 +21,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"log"
 	"os"
 	"path"
 	"strconv"
@@ -153,7 +154,20 @@ func NewStackdriverClientConfigFromMap(config map[string]string) *StackdriverCli
 // record applies the `ros` Options to each measurement in `mss` and then records the resulting
 // measurements in the metricsConfig's designated backend.
 func (mc *metricsConfig) record(ctx context.Context, mss []stats.Measurement, ros ...stats.Options) error {
-	if mc == nil || mc.recorder == nil {
+	if mc == nil {
+		log.Println(`The metricsConfig has not been initialized yet.
+
+If this is a Go unit test consuming metric.Record(...) or metric.RecordBatch(...) then
+it should add the following import:
+
+import (
+	_ "knative.dev/pkg/metrics/testing"
+)`)
+		// Don't record data points if the metric config is not initialized yet.
+		// At this point, it's unclear whether should record or not.
+		return nil
+	}
+	if mc.recorder == nil {
 		return stats.RecordWithOptions(ctx, append(ros, stats.WithMeasurements(mss...))...)
 	}
 	return mc.recorder(ctx, mss, ros...)

metrics/record_test.go

@@ -58,9 +58,6 @@ func TestRecordServing(t *testing.T) {
 			stackdriverMetricTypePrefix: "knative.dev/unsupported",
 		},
 		measurement: measure.M(3),
-	}, {
-		name:        "empty metricsConfig",
-		measurement: measure.M(4),
 	}}
 	testRecord(t, measure, shouldReportCases)
 }
@@ -87,9 +84,6 @@ func TestRecordEventing(t *testing.T) {
 			stackdriverMetricTypePrefix: "knative.dev/unsupported",
 		},
 		measurement: measure.M(3),
-	}, {
-		name:        "empty metricsConfig",
-		measurement: measure.M(4),
 	}}
 	testRecord(t, measure, shouldReportCases)
 }
@@ -149,6 +143,9 @@ func testRecord(t *testing.T, measure *stats.Int64Measure, shouldReportCases []c
 			},
 		},
 		measurement: measure.M(5),
+	}, {
+		name:        "empty metricsConfig",
+		measurement: measure.M(4),
 	}}
 
 	for _, test := range shouldNotReportCases {