Gitlab collector: Database wraparound collector and test (prometheus-community#834)

* Database wraparound collector and test --------- Signed-off-by: Felix Yuan <felix.yuan@reddit.com> Co-authored-by: Joe Adams <github@joeadams.io>

Author: Sticksman

collector/pg_database_wraparound.go

@@ -0,0 +1,115 @@
+// Copyright 2023 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package collector
+
+import (
+"context"
+"database/sql"
+
+"github.com/go-kit/log"
+"github.com/go-kit/log/level"
+"github.com/prometheus/client_golang/prometheus"
+)
+
+const databaseWraparoundSubsystem = "database_wraparound"
+
+func init() {
+registerCollector(databaseWraparoundSubsystem, defaultDisabled, NewPGDatabaseWraparoundCollector)
+}
+
+type PGDatabaseWraparoundCollector struct {
+log log.Logger
+}
+
+func NewPGDatabaseWraparoundCollector(config collectorConfig) (Collector, error) {
+return &PGDatabaseWraparoundCollector{log: config.logger}, nil
+}
+
+var (
+databaseWraparoundAgeDatfrozenxid = prometheus.NewDesc(
+prometheus.BuildFQName(namespace, databaseWraparoundSubsystem, "age_datfrozenxid_seconds"),
+"Age of the oldest transaction ID that has not been frozen.",
+[]string{"datname"},
+prometheus.Labels{},
+)
+databaseWraparoundAgeDatminmxid = prometheus.NewDesc(
+prometheus.BuildFQName(namespace, databaseWraparoundSubsystem, "age_datminmxid_seconds"),
+"Age of the oldest multi-transaction ID that has been replaced with a transaction ID.",
+[]string{"datname"},
+prometheus.Labels{},
+)
+
+databaseWraparoundQuery = `
+SELECT
+datname,
+age(d.datfrozenxid) as age_datfrozenxid,
+mxid_age(d.datminmxid) as age_datminmxid
+FROM
+pg_catalog.pg_database d
+WHERE
+d.datallowconn
+`
+)
+
+func (c *PGDatabaseWraparoundCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
+db := instance.getDB()
+rows, err := db.QueryContext(ctx,
+databaseWraparoundQuery)
+
+if err != nil {
+return err
+}
+defer rows.Close()
+
+for rows.Next() {
+var datname sql.NullString
+var ageDatfrozenxid, ageDatminmxid sql.NullFloat64
+
+if err := rows.Scan(&datname, &ageDatfrozenxid, &ageDatminmxid); err != nil {
+return err
+}
+
+if !datname.Valid {
+level.Debug(c.log).Log("msg", "Skipping database with NULL name")
+continue
+}
+if !ageDatfrozenxid.Valid {
+level.Debug(c.log).Log("msg", "Skipping stat emission with NULL age_datfrozenxid")
+continue
+}
+if !ageDatminmxid.Valid {
+level.Debug(c.log).Log("msg", "Skipping stat emission with NULL age_datminmxid")
+continue
+}
+
+ageDatfrozenxidMetric := ageDatfrozenxid.Float64
+
+ch <- prometheus.MustNewConstMetric(
+databaseWraparoundAgeDatfrozenxid,
+prometheus.GaugeValue,
+ageDatfrozenxidMetric, datname.String,
+)
+
+ageDatminmxidMetric := ageDatminmxid.Float64
+ch <- prometheus.MustNewConstMetric(
+databaseWraparoundAgeDatminmxid,
+prometheus.GaugeValue,
+ageDatminmxidMetric, datname.String,
+)
+}
+if err := rows.Err(); err != nil {
+return err
+}
+return nil
+}

collector/pg_database_wraparound_test.go

@@ -0,0 +1,64 @@
+// Copyright 2023 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package collector
+
+import (
+"context"
+"testing"
+
+"github.com/DATA-DOG/go-sqlmock"
+"github.com/prometheus/client_golang/prometheus"
+dto "github.com/prometheus/client_model/go"
+"github.com/smartystreets/goconvey/convey"
+)
+
+func TestPGDatabaseWraparoundCollector(t *testing.T) {
+db, mock, err := sqlmock.New()
+if err != nil {
+t.Fatalf("Error opening a stub db connection: %s", err)
+}
+defer db.Close()
+inst := &instance{db: db}
+columns := []string{
+"datname",
+"age_datfrozenxid",
+"age_datminmxid",
+}
+rows := sqlmock.NewRows(columns).
+AddRow("newreddit", 87126426, 0)
+
+mock.ExpectQuery(sanitizeQuery(databaseWraparoundQuery)).WillReturnRows(rows)
+
+ch := make(chan prometheus.Metric)
+go func() {
+defer close(ch)
+c := PGDatabaseWraparoundCollector{}
+
+if err := c.Update(context.Background(), inst, ch); err != nil {
+t.Errorf("Error calling PGDatabaseWraparoundCollector.Update: %s", err)
+}
+}()
+expected := []MetricResult{
+{labels: labelMap{"datname": "newreddit"}, value: 87126426, metricType: dto.MetricType_GAUGE},
+{labels: labelMap{"datname": "newreddit"}, value: 0, metricType: dto.MetricType_GAUGE},
+}
+convey.Convey("Metrics comparison", t, func() {
+for _, expect := range expected {
+m := readMetric(<-ch)
+convey.So(expect, convey.ShouldResemble, m)
+}
+})
+if err := mock.ExpectationsWereMet(); err != nil {
+t.Errorf("there were unfulfilled exceptions: %s", err)
+}
+}