Merge pull request #785 from sysadmind/collector-instance

Add the instance struct to handle connections

collector/collector.go

@@ -15,7 +15,6 @@ package collector
 
 import (
 	"context"
-	"database/sql"
 	"errors"
 	"fmt"
 	"sync"
@@ -59,7 +58,7 @@ var (
 )
 
 type Collector interface {
-	Update(ctx context.Context, db *sql.DB, ch chan<- prometheus.Metric) error
+	Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error
 }
 
 type collectorConfig struct {
@@ -92,7 +91,7 @@ type PostgresCollector struct {
 	Collectors map[string]Collector
 	logger     log.Logger
 
-	db *sql.DB
+	instance *instance
 }
 
 type Option func(*PostgresCollector) error
@@ -149,14 +148,11 @@ func NewPostgresCollector(logger log.Logger, excludeDatabases []string, dsn stri
 		return nil, errors.New("empty dsn")
 	}
 
-	db, err := sql.Open("postgres", dsn)
+	instance, err := newInstance(dsn)
 	if err != nil {
 		return nil, err
 	}
-	db.SetMaxOpenConns(1)
-	db.SetMaxIdleConns(1)
-
-	p.db = db
+	p.instance = instance
 
 	return p, nil
 }
@@ -174,16 +170,16 @@ func (p PostgresCollector) Collect(ch chan<- prometheus.Metric) {
 	wg.Add(len(p.Collectors))
 	for name, c := range p.Collectors {
 		go func(name string, c Collector) {
-			execute(ctx, name, c, p.db, ch, p.logger)
+			execute(ctx, name, c, p.instance, ch, p.logger)
 			wg.Done()
 		}(name, c)
 	}
 	wg.Wait()
 }
 
-func execute(ctx context.Context, name string, c Collector, db *sql.DB, ch chan<- prometheus.Metric, logger log.Logger) {
+func execute(ctx context.Context, name string, c Collector, instance *instance, ch chan<- prometheus.Metric, logger log.Logger) {
 	begin := time.Now()
-	err := c.Update(ctx, db, ch)
+	err := c.Update(ctx, instance, ch)
 	duration := time.Since(begin)
 	var success float64
 

collector/instance.go

@@ -0,0 +1,85 @@
+// 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 (
+	"database/sql"
+	"fmt"
+	"regexp"
+
+	"github.com/blang/semver/v4"
+)
+
+type instance struct {
+	db      *sql.DB
+	version semver.Version
+}
+
+func newInstance(dsn string) (*instance, error) {
+	i := &instance{}
+	db, err := sql.Open("postgres", dsn)
+	if err != nil {
+		return nil, err
+	}
+	db.SetMaxOpenConns(1)
+	db.SetMaxIdleConns(1)
+	i.db = db
+
+	version, err := queryVersion(db)
+	if err != nil {
+		db.Close()
+		return nil, err
+	}
+
+	i.version = version
+
+	return i, nil
+}
+
+func (i *instance) getDB() *sql.DB {
+	return i.db
+}
+
+func (i *instance) Close() error {
+	return i.db.Close()
+}
+
+// Regex used to get the "short-version" from the postgres version field.
+// The result of SELECT version() is something like "PostgreSQL 9.6.2 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 6.2.1 20160830, 64-bit"
+var versionRegex = regexp.MustCompile(`^\w+ ((\d+)(\.\d+)?(\.\d+)?)`)
+var serverVersionRegex = regexp.MustCompile(`^((\d+)(\.\d+)?(\.\d+)?)`)
+
+func queryVersion(db *sql.DB) (semver.Version, error) {
+	var version string
+	err := db.QueryRow("SELECT version();").Scan(&version)
+	if err != nil {
+		return semver.Version{}, err
+	}
+	submatches := versionRegex.FindStringSubmatch(version)
+	if len(submatches) > 1 {
+		return semver.ParseTolerant(submatches[1])
+	}
+
+	// We could also try to parse the version from the server_version field.
+	// This is of the format 13.3 (Debian 13.3-1.pgdg100+1)
+	err = db.QueryRow("SHOW server_version;").Scan(&version)
+	if err != nil {
+		return semver.Version{}, err
+	}
+	submatches = serverVersionRegex.FindStringSubmatch(version)
+	if len(submatches) > 1 {
+		return semver.ParseTolerant(submatches[1])
+	}
+	return semver.Version{}, fmt.Errorf("could not parse version from %q", version)
+}

collector/pg_database.go

@@ -15,7 +15,6 @@ package collector
 
 import (
 	"context"
-	"database/sql"
 
 	"github.com/go-kit/log"
 	"github.com/prometheus/client_golang/prometheus"
@@ -66,7 +65,8 @@ var (
 // each database individually. This is because we can't filter the
 // list of databases in the query because the list of excluded
 // databases is dynamic.
-func (c PGDatabaseCollector) Update(ctx context.Context, db *sql.DB, ch chan<- prometheus.Metric) error {
+func (c PGDatabaseCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
+	db := instance.getDB()
 	// Query the list of databases
 	rows, err := db.QueryContext(ctx,
 		pgDatabaseQuery,

collector/pg_database_test.go

@@ -29,6 +29,8 @@ func TestPGDatabaseCollector(t *testing.T) {
 	}
 	defer db.Close()
 
+	inst := &instance{db: db}
+
 	mock.ExpectQuery(sanitizeQuery(pgDatabaseQuery)).WillReturnRows(sqlmock.NewRows([]string{"datname"}).
 		AddRow("postgres"))
 
@@ -39,7 +41,7 @@ func TestPGDatabaseCollector(t *testing.T) {
 	go func() {
 		defer close(ch)
 		c := PGDatabaseCollector{}
-		if err := c.Update(context.Background(), db, ch); err != nil {
+		if err := c.Update(context.Background(), inst, ch); err != nil {
 			t.Errorf("Error calling PGDatabaseCollector.Update: %s", err)
 		}
 	}()

collector/pg_postmaster.go

@@ -15,7 +15,6 @@ package collector
 
 import (
 	"context"
-	"database/sql"
 
 	"github.com/prometheus/client_golang/prometheus"
 )
@@ -47,7 +46,8 @@ var (
 	pgPostmasterQuery = "SELECT pg_postmaster_start_time from pg_postmaster_start_time();"
 )
 
-func (c *PGPostmasterCollector) Update(ctx context.Context, db *sql.DB, ch chan<- prometheus.Metric) error {
+func (c *PGPostmasterCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
+	db := instance.getDB()
 	row := db.QueryRowContext(ctx,
 		pgPostmasterQuery)
 

collector/pg_postmaster_test.go

@@ -29,6 +29,8 @@ func TestPgPostmasterCollector(t *testing.T) {
 	}
 	defer db.Close()
 
+	inst := &instance{db: db}
+
 	mock.ExpectQuery(sanitizeQuery(pgPostmasterQuery)).WillReturnRows(sqlmock.NewRows([]string{"pg_postmaster_start_time"}).
 		AddRow(1685739904))
 
@@ -37,7 +39,7 @@ func TestPgPostmasterCollector(t *testing.T) {
 		defer close(ch)
 		c := PGPostmasterCollector{}
 
-		if err := c.Update(context.Background(), db, ch); err != nil {
+		if err := c.Update(context.Background(), inst, ch); err != nil {
 			t.Errorf("Error calling PGPostmasterCollector.Update: %s", err)
 		}
 	}()

collector/pg_process_idle.go

@@ -15,7 +15,6 @@ package collector
 
 import (
 	"context"
-	"database/sql"
 
 	"github.com/go-kit/log"
 	"github.com/prometheus/client_golang/prometheus"
@@ -42,7 +41,8 @@ var pgProcessIdleSeconds = prometheus.NewDesc(
 	prometheus.Labels{},
 )
 
-func (PGProcessIdleCollector) Update(ctx context.Context, db *sql.DB, ch chan<- prometheus.Metric) error {
+func (PGProcessIdleCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
+	db := instance.getDB()
 	row := db.QueryRowContext(ctx,
 		`WITH
 			metrics AS (

collector/pg_replication_slot.go

@@ -15,7 +15,6 @@ package collector
 
 import (
 	"context"
-	"database/sql"
 
 	"github.com/go-kit/log"
 	"github.com/prometheus/client_golang/prometheus"
@@ -73,7 +72,8 @@ var (
 		pg_replication_slots;`
 )
 
-func (PGReplicationSlotCollector) Update(ctx context.Context, db *sql.DB, ch chan<- prometheus.Metric) error {
+func (PGReplicationSlotCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
+	db := instance.getDB()
 	rows, err := db.QueryContext(ctx,
 		pgReplicationSlotQuery)
 	if err != nil {

collector/pg_replication_slot_test.go

@@ -29,6 +29,8 @@ func TestPgReplicationSlotCollectorActive(t *testing.T) {
 	}
 	defer db.Close()
 
+	inst := &instance{db: db}
+
 	columns := []string{"slot_name", "current_wal_lsn", "confirmed_flush_lsn", "active"}
 	rows := sqlmock.NewRows(columns).
 		AddRow("test_slot", 5, 3, true)
@@ -39,7 +41,7 @@ func TestPgReplicationSlotCollectorActive(t *testing.T) {
 		defer close(ch)
 		c := PGReplicationSlotCollector{}
 
-		if err := c.Update(context.Background(), db, ch); err != nil {
+		if err := c.Update(context.Background(), inst, ch); err != nil {
 			t.Errorf("Error calling PGPostmasterCollector.Update: %s", err)
 		}
 	}()
@@ -68,6 +70,8 @@ func TestPgReplicationSlotCollectorInActive(t *testing.T) {
 	}
 	defer db.Close()
 
+	inst := &instance{db: db}
+
 	columns := []string{"slot_name", "current_wal_lsn", "confirmed_flush_lsn", "active"}
 	rows := sqlmock.NewRows(columns).
 		AddRow("test_slot", 6, 12, false)
@@ -78,7 +82,7 @@ func TestPgReplicationSlotCollectorInActive(t *testing.T) {
 		defer close(ch)
 		c := PGReplicationSlotCollector{}
 
-		if err := c.Update(context.Background(), db, ch); err != nil {
+		if err := c.Update(context.Background(), inst, ch); err != nil {
 			t.Errorf("Error calling PGReplicationSlotCollector.Update: %s", err)
 		}
 	}()

collector/pg_stat_bgwriter.go

@@ -15,7 +15,6 @@ package collector
 
 import (
 	"context"
-	"database/sql"
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
@@ -117,7 +116,8 @@ var (
 	FROM pg_stat_bgwriter;`
 )
 
-func (PGStatBGWriterCollector) Update(ctx context.Context, db *sql.DB, ch chan<- prometheus.Metric) error {
+func (PGStatBGWriterCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
+	db := instance.getDB()
 	row := db.QueryRowContext(ctx,
 		statBGWriterQuery)
 

collector/pg_stat_bgwriter_test.go

@@ -30,6 +30,8 @@ func TestPGStatBGWriterCollector(t *testing.T) {
 	}
 	defer db.Close()
 
+	inst := &instance{db: db}
+
 	columns := []string{
 		"checkpoints_timed",
 		"checkpoints_req",
@@ -57,7 +59,7 @@ func TestPGStatBGWriterCollector(t *testing.T) {
 		defer close(ch)
 		c := PGStatBGWriterCollector{}
 
-		if err := c.Update(context.Background(), db, ch); err != nil {
+		if err := c.Update(context.Background(), inst, ch); err != nil {
 			t.Errorf("Error calling PGStatBGWriterCollector.Update: %s", err)
 		}
 	}()

collector/pg_stat_database.go

@@ -204,7 +204,8 @@ var (
 	)
 )
 
-func (PGStatDatabaseCollector) Update(ctx context.Context, db *sql.DB, ch chan<- prometheus.Metric) error {
+func (PGStatDatabaseCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
+	db := instance.getDB()
 	rows, err := db.QueryContext(ctx,
 		`SELECT
 			datid

collector/pg_stat_statements.go

@@ -15,7 +15,6 @@ package collector
 
 import (
 	"context"
-	"database/sql"
 
 	"github.com/go-kit/log"
 	"github.com/prometheus/client_golang/prometheus"
@@ -92,7 +91,8 @@ var (
 	LIMIT 100;`
 )
 
-func (PGStatStatementsCollector) Update(ctx context.Context, db *sql.DB, ch chan<- prometheus.Metric) error {
+func (PGStatStatementsCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
+	db := instance.getDB()
 	rows, err := db.QueryContext(ctx,
 		pgStatStatementsQuery)
 

collector/pg_stat_statements_test.go

@@ -29,6 +29,8 @@ func TestPGStateStatementsCollector(t *testing.T) {
 	}
 	defer db.Close()
 
+	inst := &instance{db: db}
+
 	columns := []string{"user", "datname", "queryid", "calls_total", "seconds_total", "rows_total", "block_read_seconds_total", "block_write_seconds_total"}
 	rows := sqlmock.NewRows(columns).
 		AddRow("postgres", "postgres", 1500, 5, 0.4, 100, 0.1, 0.2)
@@ -39,7 +41,7 @@ func TestPGStateStatementsCollector(t *testing.T) {
 		defer close(ch)
 		c := PGStatStatementsCollector{}
 
-		if err := c.Update(context.Background(), db, ch); err != nil {
+		if err := c.Update(context.Background(), inst, ch); err != nil {
 			t.Errorf("Error calling PGStatStatementsCollector.Update: %s", err)
 		}
 	}()

collector/pg_stat_user_tables.go

@@ -15,7 +15,6 @@ package collector
 
 import (
 	"context"
-	"database/sql"
 	"time"
 
 	"github.com/go-kit/log"
@@ -179,7 +178,8 @@ var (
 		pg_stat_user_tables`
 )
 
-func (c *PGStatUserTablesCollector) Update(ctx context.Context, db *sql.DB, ch chan<- prometheus.Metric) error {
+func (c *PGStatUserTablesCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
+	db := instance.getDB()
 	rows, err := db.QueryContext(ctx,
 		statUserTablesQuery)