feat: add custom collector for statement summary pre-release

Author: alessio-form3

collector/pg_stat_statements_summary.go

@@ -0,0 +1,118 @@
+// 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/prometheus/client_golang/prometheus"
+)
+
+const statStatementsSummarySubsystem = "stat_statements_summary"
+
+func init() {
+	registerCollector(statStatementsSummarySubsystem, defaultDisabled, NewPGStatStatementsSummaryCollector)
+}
+
+type PGStatStatementsSummaryCollector struct {
+	log log.Logger
+}
+
+func NewPGStatStatementsSummaryCollector(config collectorConfig) (Collector, error) {
+	return &PGStatStatementsSummaryCollector{log: config.logger}, nil
+}
+
+var (
+	statSTatementsSummaryCallsTotal = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, statStatementsSubsystem, "calls_total"),
+		"Number of times executed",
+		[]string{"datname"},
+		prometheus.Labels{},
+	)
+	statStatementsSummarySecondsTotal = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, statStatementsSubsystem, "seconds_total"),
+		"Total time spent in the statement, in seconds",
+		[]string{"datname"},
+		prometheus.Labels{},
+	)
+
+	pgStatStatementsSummaryQuery = `SELECT
+  	pg_database.datname,
+  	SUM(pg_stat_statements.calls) as calls_total,
+  	SUM(pg_stat_statements.total_exec_time) / 1000.0 as seconds_total
+  	FROM pg_stat_statements
+  JOIN pg_database
+          ON pg_database.oid = pg_stat_statements.dbid
+  WHERE
+    total_exec_time > (
+    SELECT percentile_cont(0.1)
+            WITHIN GROUP (ORDER BY total_exec_time)
+            FROM pg_stat_statements
+    )
+  GROUP BY pg_database.datname;`
+)
+
+func (PGStatStatementsSummaryCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
+	query := pgStatStatementsSummaryQuery
+
+	db := instance.getDB()
+	rows, err := db.QueryContext(ctx, query)
+
+	if err != nil {
+		return err
+	}
+	defer rows.Close()
+	for rows.Next() {
+		var datname sql.NullString
+		var callsTotal sql.NullInt64
+		var secondsTotal sql.NullFloat64
+
+		if err := rows.Scan(&datname, &callsTotal, &secondsTotal); err != nil {
+			return err
+		}
+
+		datnameLabel := "unknown"
+		if datname.Valid {
+			datnameLabel = datname.String
+		}
+
+		callsTotalMetric := 0.0
+		if callsTotal.Valid {
+			callsTotalMetric = float64(callsTotal.Int64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statSTatementsSummaryCallsTotal,
+			prometheus.CounterValue,
+			callsTotalMetric,
+			datnameLabel,
+		)
+
+		secondsTotalMetric := 0.0
+		if secondsTotal.Valid {
+			secondsTotalMetric = secondsTotal.Float64
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statStatementsSummarySecondsTotal,
+			prometheus.CounterValue,
+			secondsTotalMetric,
+			datnameLabel,
+		)
+	}
+	if err := rows.Err(); err != nil {
+		return err
+	}
+	return nil
+}

collector/pg_stat_statements_summary_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/blang/semver/v4"
+	"github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
+	"github.com/smartystreets/goconvey/convey"
+)
+
+func TestPGStateStatementsSummaryCollector(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, version: semver.MustParse("13.3.7")}
+
+	columns := []string{"datname", "calls_total", "seconds_total"}
+	rows := sqlmock.NewRows(columns).
+		AddRow("postgres", 5, 0.4)
+	mock.ExpectQuery(sanitizeQuery(pgStatStatementsSummaryQuery)).WillReturnRows(rows)
+
+	ch := make(chan prometheus.Metric)
+	go func() {
+		defer close(ch)
+		c := PGStatStatementsSummaryCollector{}
+
+		if err := c.Update(context.Background(), inst, ch); err != nil {
+			t.Errorf("Error calling PGStatStatementsSummaryCollector.Update: %s", err)
+		}
+	}()
+
+	expected := []MetricResult{
+		{labels: labelMap{"datname": "postgres"}, metricType: dto.MetricType_COUNTER, value: 5},
+		{labels: labelMap{"datname": "postgres"}, metricType: dto.MetricType_COUNTER, value: 0.4},
+	}
+
+	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)
+	}
+}