Fix inconsistency with input error counting (#7077)

internal/models/running_input_test.go

@@ -4,6 +4,8 @@ import (
 	"testing"
 	"time"
 
+	"github.com/influxdata/telegraf/selfstat"
+
 	"github.com/influxdata/telegraf"
 	"github.com/influxdata/telegraf/metric"
 	"github.com/influxdata/telegraf/testutil"
@@ -256,6 +258,35 @@ func TestMakeMetricNameSuffix(t *testing.T) {
 	require.Equal(t, expected, m)
 }
 
+func TestMetricErrorCounters(t *testing.T) {
+	ri := NewRunningInput(&testInput{}, &InputConfig{
+		Name: "TestMetricErrorCounters",
+	})
+
+	getGatherErrors := func() int64 {
+		for _, r := range selfstat.Metrics() {
+			tag, hasTag := r.GetTag("input")
+			if r.Name() == "internal_gather" && hasTag && tag == "TestMetricErrorCounters" {
+				errCount, ok := r.GetField("errors")
+				if !ok {
+					t.Fatal("Expected error field")
+				}
+				return errCount.(int64)
+			}
+		}
+		return 0
+	}
+
+	before := getGatherErrors()
+
+	ri.Log().Error("Oh no")
+
+	after := getGatherErrors()
+
+	require.Greater(t, after, before)
+	require.GreaterOrEqual(t, int64(1), GlobalGatherErrors.Get())
+}
+
 type testInput struct{}
 
 func (t *testInput) Description() string                   { return "" }