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)
+}
+}