Added the last binlog file number metric.

collector/binlog.go

@@ -4,6 +4,8 @@ package collector
 
 import (
 	"database/sql"
+	"strconv"
+	"strings"
 
 	"github.com/prometheus/client_golang/prometheus"
 )
@@ -28,6 +30,11 @@ var (
 		"Number of registered binlog files.",
 		[]string{}, nil,
 	)
+	binlogFileNumberDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, binlog, "file_number"),
+		"The last binlog file number.",
+		[]string{}, nil,
+	)
 )
 
 // ScrapeBinlogSize colects from `SHOW BINARY LOGS`.
@@ -71,6 +78,11 @@ func ScrapeBinlogSize(db *sql.DB, ch chan<- prometheus.Metric) error {
 	ch <- prometheus.MustNewConstMetric(
 		binlogFilesDesc, prometheus.GaugeValue, float64(count),
 	)
+	// The last row contains the last binlog file number.
+	value, _ := strconv.ParseFloat(strings.Split(filename, ".")[1], 64)
+	ch <- prometheus.MustNewConstMetric(
+		binlogFileNumberDesc, prometheus.GaugeValue, value,
+	)
 
 	return nil
 }

collector/binlog_test.go

@@ -0,0 +1,52 @@
+package collector
+
+import (
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
+	"github.com/smartystreets/goconvey/convey"
+	"gopkg.in/DATA-DOG/go-sqlmock.v1"
+)
+
+func TestScrapeBinlogSize(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("error opening a stub database connection: %s", err)
+	}
+	defer db.Close()
+
+	mock.ExpectQuery(logbinQuery).WillReturnRows(sqlmock.NewRows([]string{""}).AddRow(1))
+
+	columns := []string{"Log_name", "File_size"}
+	rows := sqlmock.NewRows(columns).
+		AddRow("centos6-bin.000001", "1813").
+		AddRow("centos6-bin.000002", "120").
+		AddRow("centos6-bin.000444", "573009")
+	mock.ExpectQuery(sanitizeQuery(binlogQuery)).WillReturnRows(rows)
+
+	ch := make(chan prometheus.Metric)
+	go func() {
+		if err = ScrapeBinlogSize(db, ch); err != nil {
+			t.Errorf("error calling function on test: %s", err)
+		}
+		close(ch)
+	}()
+
+	counterExpected := []MetricResult{
+		{labels: labelMap{}, value: 574942, metricType: dto.MetricType_GAUGE},
+		{labels: labelMap{}, value: 3, metricType: dto.MetricType_GAUGE},
+		{labels: labelMap{}, value: 444, metricType: dto.MetricType_GAUGE},
+	}
+	convey.Convey("Metrics comparison", t, func() {
+		for _, expect := range counterExpected {
+			got := readMetric(<-ch)
+			convey.So(got, convey.ShouldResemble, expect)
+		}
+	})
+
+	// Ensure all SQL queries were executed
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("there were unfulfilled expections: %s", err)
+	}
+}