Add Table Sizes to postgresql exporter

Signed-off-by: Moritz Wirth <mw@flanga.io>

Author: mowirth

collector/pg_table.go

@@ -0,0 +1,139 @@
+// Copyright 2024 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 tableSizeSubsystem = "table_size"
+
+func init() {
+	registerCollector(tableSizeSubsystem, defaultEnabled, NewPGTableSizeCollector)
+}
+
+type PGTableSizeCollector struct {
+	log log.Logger
+}
+
+func NewPGTableSizeCollector(config collectorConfig) (Collector, error) {
+	return &PGTableSizeCollector{
+		log: config.logger,
+	}, nil
+}
+
+var (
+	pgTableTotalRelationDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(
+			namespace,
+			tableSizeSubsystem,
+			"total_relation",
+		),
+		"Total Relation Size of the table",
+		[]string{"schemaname", "datname", "relname"}, nil,
+	)
+	pgTableIndexSizeDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(
+			namespace,
+			tableSizeSubsystem,
+			"index",
+		),
+		"Indexes Size of the Table",
+		[]string{"schemaname", "datname", "relname"}, nil,
+	)
+	pgRelationSizeDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(
+			namespace,
+			tableSizeSubsystem,
+			"relation",
+		),
+		"Relation Size of the table",
+		[]string{"schemaname", "datname", "relname"}, nil,
+	)
+	pgTableSizeQuery = `SELECT
+        table_catalog datname,
+        table_name relname,
+        table_schema schemaname,
+        pg_total_relation_size('"'||table_schema||'"."'||table_name||'"') total_relation_size,
+        pg_relation_size('"'||table_schema||'"."'||table_name||'"') relation_size,
+        pg_indexes_size('"'||table_schema||'"."'||table_name||'"')  indexes_size
+    FROM information_schema.tables`
+)
+
+// Update implements Collector and exposes database locks.
+// It is called by the Prometheus registry when collecting metrics.
+func (c PGTableSizeCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
+	db := instance.getDB()
+	// Query the list of databases
+	rows, err := db.QueryContext(ctx, pgTableSizeQuery)
+	if err != nil {
+		return err
+	}
+	defer rows.Close()
+	for rows.Next() {
+		var tableSchema, tableName, databaseName sql.NullString
+		var totalRelationSize, relationSize, indexesSize sql.NullInt64
+
+		if err := rows.Scan(&databaseName, &tableName, &tableSchema, &totalRelationSize, &relationSize, &indexesSize); err != nil {
+			return err
+		}
+
+		if !tableSchema.Valid || !tableName.Valid || !databaseName.Valid {
+			continue
+		}
+
+		totalRelationsSizeMetric := 0.0
+		relationSizeMetric := 0.0
+		indexesSizeMetric := 0.0
+		if totalRelationSize.Valid {
+			totalRelationsSizeMetric = float64(totalRelationSize.Int64)
+		}
+
+		if relationSize.Valid {
+			relationSizeMetric = float64(relationSize.Int64)
+		}
+
+		if indexesSize.Valid {
+			indexesSizeMetric = float64(indexesSize.Int64)
+		}
+
+		ch <- prometheus.MustNewConstMetric(
+			pgTableTotalRelationDesc,
+			prometheus.CounterValue, totalRelationsSizeMetric,
+			tableSchema.String, databaseName.String, tableName.String,
+		)
+
+		ch <- prometheus.MustNewConstMetric(
+			pgRelationSizeDesc,
+			prometheus.CounterValue, relationSizeMetric,
+			tableSchema.String, databaseName.String, tableName.String,
+		)
+
+		ch <- prometheus.MustNewConstMetric(
+			pgTableIndexSizeDesc,
+			prometheus.CounterValue, indexesSizeMetric,
+			tableSchema.String, databaseName.String, tableName.String,
+		)
+	}
+
+	if err := rows.Err(); err != nil {
+		return err
+	}
+
+	return nil
+}

collector/pg_table_test.go

@@ -0,0 +1,54 @@
+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 TestPGTableSizeCollector(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}
+
+	rows := sqlmock.NewRows([]string{"datname", "relname", "schemaname", "total_relation_size", "relation_size", "indexes_size"}).
+		AddRow("test", "testrel", "testschema", 69, 42, 27).
+		AddRow("test2", "testrel2", "testschema2", 14, 10, 2)
+
+	mock.ExpectQuery(sanitizeQuery(pgTableSizeQuery)).WillReturnRows(rows)
+
+	ch := make(chan prometheus.Metric)
+	go func() {
+		defer close(ch)
+		c := PGTableSizeCollector{}
+		if err := c.Update(context.Background(), inst, ch); err != nil {
+			t.Errorf("Error calling PGTableSizeCollector.Update: %s", err)
+		}
+	}()
+
+	expected := []MetricResult{
+		{labels: labelMap{"datname": "test", "relname": "testrel", "schemaname": "testschema"}, value: 69, metricType: dto.MetricType_COUNTER},
+		{labels: labelMap{"datname": "test", "relname": "testrel", "schemaname": "testschema"}, value: 42, metricType: dto.MetricType_COUNTER},
+		{labels: labelMap{"datname": "test", "relname": "testrel", "schemaname": "testschema"}, value: 27, metricType: dto.MetricType_COUNTER},
+		{labels: labelMap{"datname": "test2", "relname": "testrel2", "schemaname": "testschema2"}, value: 14, metricType: dto.MetricType_COUNTER},
+		{labels: labelMap{"datname": "test2", "relname": "testrel2", "schemaname": "testschema2"}, value: 10, metricType: dto.MetricType_COUNTER},
+		{labels: labelMap{"datname": "test2", "relname": "testrel2", "schemaname": "testschema2"}, value: 2, metricType: dto.MetricType_COUNTER},
+	}
+	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)
+	}
+}