Use persistent connection to postgresql database (#2701)

CHANGELOG.md

@@ -63,6 +63,10 @@
   `use_random_partitionkey` options has been deprecated in favor of the
   `partition` subtable.  This allows for more flexible methods to set the
   partition key such as by metric name or by tag.
+- `postgresql` plugins will now default to using a persistent connection to the database.
+  `Important` In environments TCP connections are terminated when idle for periods shorter than 15 minutes
+  and the collection interval is longer than the termination period then max_lifetime
+  should be set to be less than the collection interval to pervent errors when collecting metrics.
 
 - With the release of the new improved `jolokia2` input, the legacy `jolokia`
   plugin is deprecated and will be removed in a future release.  Users of this

plugins/inputs/postgresql/connect.go

@@ -1,77 +0,0 @@
-package postgresql
-
-import (
-	"fmt"
-	"net"
-	"net/url"
-	"sort"
-	"strings"
-)
-
-// pulled from lib/pq
-// ParseURL no longer needs to be used by clients of this library since supplying a URL as a
-// connection string to sql.Open() is now supported:
-//
-//	sql.Open("postgres", "postgres://bob:secret@1.2.3.4:5432/mydb?sslmode=verify-full")
-//
-// It remains exported here for backwards-compatibility.
-//
-// ParseURL converts a url to a connection string for driver.Open.
-// Example:
-//
-//	"postgres://bob:secret@1.2.3.4:5432/mydb?sslmode=verify-full"
-//
-// converts to:
-//
-//	"user=bob password=secret host=1.2.3.4 port=5432 dbname=mydb sslmode=verify-full"
-//
-// A minimal example:
-//
-//	"postgres://"
-//
-// This will be blank, causing driver.Open to use all of the defaults
-func ParseURL(uri string) (string, error) {
-	u, err := url.Parse(uri)
-	if err != nil {
-		return "", err
-	}
-
-	if u.Scheme != "postgres" && u.Scheme != "postgresql" {
-		return "", fmt.Errorf("invalid connection protocol: %s", u.Scheme)
-	}
-
-	var kvs []string
-	escaper := strings.NewReplacer(` `, `\ `, `'`, `\'`, `\`, `\\`)
-	accrue := func(k, v string) {
-		if v != "" {
-			kvs = append(kvs, k+"="+escaper.Replace(v))
-		}
-	}
-
-	if u.User != nil {
-		v := u.User.Username()
-		accrue("user", v)
-
-		v, _ = u.User.Password()
-		accrue("password", v)
-	}
-
-	if host, port, err := net.SplitHostPort(u.Host); err != nil {
-		accrue("host", u.Host)
-	} else {
-		accrue("host", host)
-		accrue("port", port)
-	}
-
-	if u.Path != "" {
-		accrue("dbname", u.Path[1:])
-	}
-
-	q := u.Query()
-	for k := range q {
-		accrue(k, q.Get(k))
-	}
-
-	sort.Strings(kvs) // Makes testing easier (not a performance concern)
-	return strings.Join(kvs, " "), nil
-}

plugins/inputs/postgresql/postgresql.go

@@ -2,26 +2,21 @@ package postgresql
 
 import (
 	"bytes"
-	"database/sql"
 	"fmt"
-	"regexp"
-	"sort"
 	"strings"
 
 	// register in driver.
 	_ "github.com/jackc/pgx/stdlib"
 
 	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/internal"
 	"github.com/influxdata/telegraf/plugins/inputs"
 )
 
 type Postgresql struct {
-	Address          string
+	Service
 	Databases        []string
 	IgnoredDatabases []string
-	OrderedColumns   []string
-	AllColumns       []string
-	sanitizedAddress string
 }
 
 var ignoredColumns = map[string]bool{"stats_reset": true}
@@ -41,6 +36,15 @@ var sampleConfig = `
   ## to grab metrics for.
   ##
   address = "host=localhost user=postgres sslmode=disable"
+  ## A custom name for the database that will be used as the "server" tag in the
+  ## measurement output. If not specified, a default one generated from
+  ## the connection address is used.
+  # outputaddress = "db01"
+
+  ## connection configuration.
+  ## maxlifetime - specify the maximum lifetime of a connection.
+  ## default is forever (0s)
+  max_lifetime = "0s"
 
   ## A  list of databases to explicitly ignore.  If not specified, metrics for all
   ## databases are gathered.  Do NOT use with the 'databases' option.
@@ -63,24 +67,13 @@ func (p *Postgresql) IgnoredColumns() map[string]bool {
 	return ignoredColumns
 }
 
-var localhost = "host=localhost sslmode=disable"
-
 func (p *Postgresql) Gather(acc telegraf.Accumulator) error {
 	var (
 		err     error
-		db    *sql.DB
 		query   string
+		columns []string
 	)
 
-	if p.Address == "" || p.Address == "localhost" {
-		p.Address = localhost
-	}
-
-	if db, err = sql.Open("pgx", p.Address); err != nil {
-		return err
-	}
-	defer db.Close()
-
 	if len(p.Databases) == 0 && len(p.IgnoredDatabases) == 0 {
 		query = `SELECT * FROM pg_stat_database`
 	} else if len(p.IgnoredDatabases) != 0 {
@@ -91,7 +84,7 @@ func (p *Postgresql) Gather(acc telegraf.Accumulator) error {
 			strings.Join(p.Databases, "','"))
 	}
 
-	rows, err := db.Query(query)
+	rows, err := p.DB.Query(query)
 	if err != nil {
 		return err
 	}
@@ -99,16 +92,12 @@ func (p *Postgresql) Gather(acc telegraf.Accumulator) error {
 	defer rows.Close()
 
 	// grab the column information from the result
-	p.OrderedColumns, err = rows.Columns()
+	if columns, err = rows.Columns(); err != nil {
-	if err != nil {
 		return err
-	} else {
-		p.AllColumns = make([]string, len(p.OrderedColumns))
-		copy(p.AllColumns, p.OrderedColumns)
 	}
 
 	for rows.Next() {
-		err = p.accRow(rows, acc)
+		err = p.accRow(rows, acc, columns)
 		if err != nil {
 			return err
 		}
@@ -116,7 +105,7 @@ func (p *Postgresql) Gather(acc telegraf.Accumulator) error {
 
 	query = `SELECT * FROM pg_stat_bgwriter`
 
-	bg_writer_row, err := db.Query(query)
+	bg_writer_row, err := p.DB.Query(query)
 	if err != nil {
 		return err
 	}
@@ -124,22 +113,17 @@ func (p *Postgresql) Gather(acc telegraf.Accumulator) error {
 	defer bg_writer_row.Close()
 
 	// grab the column information from the result
-	p.OrderedColumns, err = bg_writer_row.Columns()
+	if columns, err = bg_writer_row.Columns(); err != nil {
-	if err != nil {
 		return err
-	} else {
-		for _, v := range p.OrderedColumns {
-			p.AllColumns = append(p.AllColumns, v)
-		}
 	}
 
 	for bg_writer_row.Next() {
-		err = p.accRow(bg_writer_row, acc)
+		err = p.accRow(bg_writer_row, acc, columns)
 		if err != nil {
 			return err
 		}
 	}
-	sort.Strings(p.AllColumns)
+
 	return bg_writer_row.Err()
 }
 
@@ -147,37 +131,20 @@ type scanner interface {
 	Scan(dest ...interface{}) error
 }
 
-var passwordKVMatcher, _ = regexp.Compile("password=\\S+ ?")
+func (p *Postgresql) accRow(row scanner, acc telegraf.Accumulator, columns []string) error {
-
-func (p *Postgresql) SanitizedAddress() (_ string, err error) {
-	var canonicalizedAddress string
-	if strings.HasPrefix(p.Address, "postgres://") || strings.HasPrefix(p.Address, "postgresql://") {
-		canonicalizedAddress, err = ParseURL(p.Address)
-		if err != nil {
-			return p.sanitizedAddress, err
-		}
-	} else {
-		canonicalizedAddress = p.Address
-	}
-	p.sanitizedAddress = passwordKVMatcher.ReplaceAllString(canonicalizedAddress, "")
-
-	return p.sanitizedAddress, err
-}
-
-func (p *Postgresql) accRow(row scanner, acc telegraf.Accumulator) error {
 	var columnVars []interface{}
 	var dbname bytes.Buffer
 
 	// this is where we'll store the column name with its *interface{}
 	columnMap := make(map[string]*interface{})
 
-	for _, column := range p.OrderedColumns {
+	for _, column := range columns {
 		columnMap[column] = new(interface{})
 	}
 
 	// populate the array of interface{} with the pointers in the right order
 	for i := 0; i < len(columnMap); i++ {
-		columnVars = append(columnVars, columnMap[p.OrderedColumns[i]])
+		columnVars = append(columnVars, columnMap[columns[i]])
 	}
 
 	// deconstruct array of variables and send to Scan
@@ -215,6 +182,14 @@ func (p *Postgresql) accRow(row scanner, acc telegraf.Accumulator) error {
 
 func init() {
 	inputs.Add("postgresql", func() telegraf.Input {
-		return &Postgresql{}
+		return &Postgresql{
+			Service: Service{
+				MaxIdle: 1,
+				MaxOpen: 1,
+				MaxLifetime: internal.Duration{
+					Duration: 0,
+				},
+			},
+		}
 	})
 }

plugins/inputs/postgresql/postgresql_test.go

@@ -15,19 +15,18 @@ func TestPostgresqlGeneratesMetrics(t *testing.T) {
 	}
 
 	p := &Postgresql{
-		Address: fmt.Sprintf("host=%s user=postgres sslmode=disable",
+		Service: Service{
-			testutil.GetLocalHost()),
+			Address: fmt.Sprintf(
+				"host=%s user=postgres sslmode=disable",
+				testutil.GetLocalHost(),
+			),
+		},
 		Databases: []string{"postgres"},
 	}
 
 	var acc testutil.Accumulator
-	err := p.Gather(&acc)
+	require.NoError(t, p.Start(&acc))
-	require.NoError(t, err)
+	require.NoError(t, p.Gather(&acc))
-
-	availableColumns := make(map[string]bool)
-	for _, col := range p.AllColumns {
-		availableColumns[col] = true
-	}
 
 	intMetrics := []string{
 		"xact_commit",
@@ -71,39 +70,27 @@ func TestPostgresqlGeneratesMetrics(t *testing.T) {
 	metricsCounted := 0
 
 	for _, metric := range intMetrics {
-		_, ok := availableColumns[metric]
-		if ok {
 		assert.True(t, acc.HasInt64Field("postgresql", metric))
 		metricsCounted++
 	}
-	}
 
 	for _, metric := range int32Metrics {
-		_, ok := availableColumns[metric]
-		if ok {
 		assert.True(t, acc.HasInt32Field("postgresql", metric))
 		metricsCounted++
 	}
-	}
 
 	for _, metric := range floatMetrics {
-		_, ok := availableColumns[metric]
-		if ok {
 		assert.True(t, acc.HasFloatField("postgresql", metric))
 		metricsCounted++
 	}
-	}
 
 	for _, metric := range stringMetrics {
-		_, ok := availableColumns[metric]
-		if ok {
 		assert.True(t, acc.HasStringField("postgresql", metric))
 		metricsCounted++
 	}
-	}
 
 	assert.True(t, metricsCounted > 0)
-	assert.Equal(t, len(availableColumns)-len(p.IgnoredColumns()), metricsCounted)
+	assert.Equal(t, len(floatMetrics)+len(intMetrics)+len(int32Metrics)+len(stringMetrics), metricsCounted)
 }
 
 func TestPostgresqlTagsMetricsWithDatabaseName(t *testing.T) {
@@ -112,15 +99,19 @@ func TestPostgresqlTagsMetricsWithDatabaseName(t *testing.T) {
 	}
 
 	p := &Postgresql{
-		Address: fmt.Sprintf("host=%s user=postgres sslmode=disable",
+		Service: Service{
-			testutil.GetLocalHost()),
+			Address: fmt.Sprintf(
+				"host=%s user=postgres sslmode=disable",
+				testutil.GetLocalHost(),
+			),
+		},
 		Databases: []string{"postgres"},
 	}
 
 	var acc testutil.Accumulator
 
-	err := p.Gather(&acc)
+	require.NoError(t, p.Start(&acc))
-	require.NoError(t, err)
+	require.NoError(t, p.Gather(&acc))
 
 	point, ok := acc.Get("postgresql")
 	require.True(t, ok)
@@ -134,14 +125,18 @@ func TestPostgresqlDefaultsToAllDatabases(t *testing.T) {
 	}
 
 	p := &Postgresql{
-		Address: fmt.Sprintf("host=%s user=postgres sslmode=disable",
+		Service: Service{
-			testutil.GetLocalHost()),
+			Address: fmt.Sprintf(
+				"host=%s user=postgres sslmode=disable",
+				testutil.GetLocalHost(),
+			),
+		},
 	}
 
 	var acc testutil.Accumulator
 
-	err := p.Gather(&acc)
+	require.NoError(t, p.Start(&acc))
-	require.NoError(t, err)
+	require.NoError(t, p.Gather(&acc))
 
 	var found bool
 
@@ -163,14 +158,17 @@ func TestPostgresqlIgnoresUnwantedColumns(t *testing.T) {
 	}
 
 	p := &Postgresql{
-		Address: fmt.Sprintf("host=%s user=postgres sslmode=disable",
+		Service: Service{
-			testutil.GetLocalHost()),
+			Address: fmt.Sprintf(
+				"host=%s user=postgres sslmode=disable",
+				testutil.GetLocalHost(),
+			),
+		},
 	}
 
 	var acc testutil.Accumulator
-
+	require.NoError(t, p.Start(&acc))
-	err := p.Gather(&acc)
+	require.NoError(t, p.Gather(&acc))
-	require.NoError(t, err)
 
 	for col := range p.IgnoredColumns() {
 		assert.False(t, acc.HasMeasurement(col))
@@ -183,15 +181,19 @@ func TestPostgresqlDatabaseWhitelistTest(t *testing.T) {
 	}
 
 	p := &Postgresql{
-		Address: fmt.Sprintf("host=%s user=postgres sslmode=disable",
+		Service: Service{
-			testutil.GetLocalHost()),
+			Address: fmt.Sprintf(
+				"host=%s user=postgres sslmode=disable",
+				testutil.GetLocalHost(),
+			),
+		},
 		Databases: []string{"template0"},
 	}
 
 	var acc testutil.Accumulator
 
-	err := p.Gather(&acc)
+	require.NoError(t, p.Start(&acc))
-	require.NoError(t, err)
+	require.NoError(t, p.Gather(&acc))
 
 	var foundTemplate0 = false
 	var foundTemplate1 = false
@@ -219,15 +221,18 @@ func TestPostgresqlDatabaseBlacklistTest(t *testing.T) {
 	}
 
 	p := &Postgresql{
-		Address: fmt.Sprintf("host=%s user=postgres sslmode=disable",
+		Service: Service{
-			testutil.GetLocalHost()),
+			Address: fmt.Sprintf(
+				"host=%s user=postgres sslmode=disable",
+				testutil.GetLocalHost(),
+			),
+		},
 		IgnoredDatabases: []string{"template0"},
 	}
 
 	var acc testutil.Accumulator
-
+	require.NoError(t, p.Start(&acc))
-	err := p.Gather(&acc)
+	require.NoError(t, p.Gather(&acc))
-	require.NoError(t, err)
 
 	var foundTemplate0 = false
 	var foundTemplate1 = false

plugins/inputs/postgresql/service.go

@@ -0,0 +1,142 @@
+package postgresql
+
+import (
+	"database/sql"
+	"fmt"
+	"net"
+	"net/url"
+	"regexp"
+	"sort"
+	"strings"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/internal"
+)
+
+// pulled from lib/pq
+// ParseURL no longer needs to be used by clients of this library since supplying a URL as a
+// connection string to sql.Open() is now supported:
+//
+//	sql.Open("postgres", "postgres://bob:secret@1.2.3.4:5432/mydb?sslmode=verify-full")
+//
+// It remains exported here for backwards-compatibility.
+//
+// ParseURL converts a url to a connection string for driver.Open.
+// Example:
+//
+//	"postgres://bob:secret@1.2.3.4:5432/mydb?sslmode=verify-full"
+//
+// converts to:
+//
+//	"user=bob password=secret host=1.2.3.4 port=5432 dbname=mydb sslmode=verify-full"
+//
+// A minimal example:
+//
+//	"postgres://"
+//
+// This will be blank, causing driver.Open to use all of the defaults
+func parseURL(uri string) (string, error) {
+	u, err := url.Parse(uri)
+	if err != nil {
+		return "", err
+	}
+
+	if u.Scheme != "postgres" && u.Scheme != "postgresql" {
+		return "", fmt.Errorf("invalid connection protocol: %s", u.Scheme)
+	}
+
+	var kvs []string
+	escaper := strings.NewReplacer(` `, `\ `, `'`, `\'`, `\`, `\\`)
+	accrue := func(k, v string) {
+		if v != "" {
+			kvs = append(kvs, k+"="+escaper.Replace(v))
+		}
+	}
+
+	if u.User != nil {
+		v := u.User.Username()
+		accrue("user", v)
+
+		v, _ = u.User.Password()
+		accrue("password", v)
+	}
+
+	if host, port, err := net.SplitHostPort(u.Host); err != nil {
+		accrue("host", u.Host)
+	} else {
+		accrue("host", host)
+		accrue("port", port)
+	}
+
+	if u.Path != "" {
+		accrue("dbname", u.Path[1:])
+	}
+
+	q := u.Query()
+	for k := range q {
+		accrue(k, q.Get(k))
+	}
+
+	sort.Strings(kvs) // Makes testing easier (not a performance concern)
+	return strings.Join(kvs, " "), nil
+}
+
+// Service common functionality shared between the postgresql and postgresql_extensible
+// packages.
+type Service struct {
+	Address       string
+	Outputaddress string
+	MaxIdle       int
+	MaxOpen       int
+	MaxLifetime   internal.Duration
+	DB            *sql.DB
+}
+
+// Start starts the ServiceInput's service, whatever that may be
+func (p *Service) Start(telegraf.Accumulator) (err error) {
+	const localhost = "host=localhost sslmode=disable"
+
+	if p.Address == "" || p.Address == "localhost" {
+		p.Address = localhost
+	}
+
+	if p.DB, err = sql.Open("pgx", p.Address); err != nil {
+		return err
+	}
+
+	p.DB.SetMaxOpenConns(p.MaxOpen)
+	p.DB.SetMaxIdleConns(p.MaxIdle)
+	p.DB.SetConnMaxLifetime(p.MaxLifetime.Duration)
+
+	return nil
+}
+
+// Stop stops the services and closes any necessary channels and connections
+func (p *Service) Stop() {
+	p.DB.Close()
+}
+
+var kvMatcher, _ = regexp.Compile("(password|sslcert|sslkey|sslmode|sslrootcert)=\\S+ ?")
+
+// SanitizedAddress utility function to strip sensitive information from the connection string.
+func (p *Service) SanitizedAddress() (sanitizedAddress string, err error) {
+	var (
+		canonicalizedAddress string
+	)
+
+	if p.Outputaddress != "" {
+		return p.Outputaddress, nil
+	}
+
+	if strings.HasPrefix(p.Address, "postgres://") || strings.HasPrefix(p.Address, "postgresql://") {
+		if canonicalizedAddress, err = parseURL(p.Address); err != nil {
+			return sanitizedAddress, err
+		}
+	} else {
+		canonicalizedAddress = p.Address
+	}
+
+	sanitizedAddress = kvMatcher.ReplaceAllString(canonicalizedAddress, "")
+
+	return sanitizedAddress, err
+}

plugins/inputs/postgresql_extensible/postgresql_extensible.go

@@ -2,28 +2,23 @@ package postgresql_extensible
 
 import (
 	"bytes"
-	"database/sql"
 	"fmt"
 	"log"
-	"regexp"
 	"strings"
 
 	// register in driver.
 	_ "github.com/jackc/pgx/stdlib"
 
 	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/internal"
 	"github.com/influxdata/telegraf/plugins/inputs"
 	"github.com/influxdata/telegraf/plugins/inputs/postgresql"
 )
 
 type Postgresql struct {
-	Address          string
+	postgresql.Service
-	Outputaddress    string
 	Databases      []string
-	OrderedColumns   []string
-	AllColumns       []string
 	AdditionalTags []string
-	sanitizedAddress string
 	Query          []struct {
 		Sqlquery    string
 		Version     int
@@ -58,14 +53,20 @@ var sampleConfig = `
   ## to grab metrics for.
   #
   address = "host=localhost user=postgres sslmode=disable"
+
+  ## connection configuration.
+  ## maxlifetime - specify the maximum lifetime of a connection.
+  ## default is forever (0s)
+  max_lifetime = "0s"
+
   ## A list of databases to pull metrics about. If not specified, metrics for all
   ## databases are gathered.
   ## databases = ["app_production", "testing"]
   #
-  # outputaddress = "db01"
   ## A custom name for the database that will be used as the "server" tag in the
   ## measurement output. If not specified, a default one generated from
   ## the connection address is used.
+  # outputaddress = "db01"
   #
   ## Define the toml config where the sql queries are stored
   ## New queries can be added, if the withdbname is set to true and there is no
@@ -113,36 +114,25 @@ func (p *Postgresql) IgnoredColumns() map[string]bool {
 	return ignoredColumns
 }
 
-var localhost = "host=localhost sslmode=disable"
-
 func (p *Postgresql) Gather(acc telegraf.Accumulator) error {
 	var (
 		err         error
-		db          *sql.DB
 		sql_query   string
 		query_addon string
 		db_version  int
 		query       string
 		tag_value   string
 		meas_name   string
+		columns     []string
 	)
 
-	if p.Address == "" || p.Address == "localhost" {
-		p.Address = localhost
-	}
-
-	if db, err = sql.Open("pgx", p.Address); err != nil {
-		return err
-	}
-	defer db.Close()
-
 	// Retreiving the database version
 
 	query = `select substring(setting from 1 for 3) as version from pg_settings where name='server_version_num'`
-	err = db.QueryRow(query).Scan(&db_version)
+	if err = p.DB.QueryRow(query).Scan(&db_version); err != nil {
-	if err != nil {
 		db_version = 0
 	}
+
 	// We loop in order to process each query
 	// Query is not run if Database version does not match the query version.
 
@@ -168,7 +158,7 @@ func (p *Postgresql) Gather(acc telegraf.Accumulator) error {
 		sql_query += query_addon
 
 		if p.Query[i].Version <= db_version {
-			rows, err := db.Query(sql_query)
+			rows, err := p.DB.Query(sql_query)
 			if err != nil {
 				acc.AddError(err)
 				continue
@@ -177,15 +167,11 @@ func (p *Postgresql) Gather(acc telegraf.Accumulator) error {
 			defer rows.Close()
 
 			// grab the column information from the result
-			p.OrderedColumns, err = rows.Columns()
+			if columns, err = rows.Columns(); err != nil {
-			if err != nil {
 				acc.AddError(err)
 				continue
-			} else {
-				for _, v := range p.OrderedColumns {
-					p.AllColumns = append(p.AllColumns, v)
-				}
 			}
+
 			p.AdditionalTags = nil
 			if tag_value != "" {
 				tag_list := strings.Split(tag_value, ",")
@@ -195,7 +181,7 @@ func (p *Postgresql) Gather(acc telegraf.Accumulator) error {
 			}
 
 			for rows.Next() {
-				err = p.accRow(meas_name, rows, acc)
+				err = p.accRow(meas_name, rows, acc, columns)
 				if err != nil {
 					acc.AddError(err)
 					break
@@ -210,27 +196,7 @@ type scanner interface {
 	Scan(dest ...interface{}) error
 }
 
-var KVMatcher, _ = regexp.Compile("(password|sslcert|sslkey|sslmode|sslrootcert)=\\S+ ?")
+func (p *Postgresql) accRow(meas_name string, row scanner, acc telegraf.Accumulator, columns []string) error {
-
-func (p *Postgresql) SanitizedAddress() (_ string, err error) {
-	if p.Outputaddress != "" {
-		return p.Outputaddress, nil
-	}
-	var canonicalizedAddress string
-	if strings.HasPrefix(p.Address, "postgres://") || strings.HasPrefix(p.Address, "postgresql://") {
-		canonicalizedAddress, err = postgresql.ParseURL(p.Address)
-		if err != nil {
-			return p.sanitizedAddress, err
-		}
-	} else {
-		canonicalizedAddress = p.Address
-	}
-	p.sanitizedAddress = KVMatcher.ReplaceAllString(canonicalizedAddress, "")
-
-	return p.sanitizedAddress, err
-}
-
-func (p *Postgresql) accRow(meas_name string, row scanner, acc telegraf.Accumulator) error {
 	var (
 		err        error
 		columnVars []interface{}
@@ -241,13 +207,13 @@ func (p *Postgresql) accRow(meas_name string, row scanner, acc telegraf.Accumula
 	// this is where we'll store the column name with its *interface{}
 	columnMap := make(map[string]*interface{})
 
-	for _, column := range p.OrderedColumns {
+	for _, column := range columns {
 		columnMap[column] = new(interface{})
 	}
 
 	// populate the array of interface{} with the pointers in the right order
 	for i := 0; i < len(columnMap); i++ {
-		columnVars = append(columnVars, columnMap[p.OrderedColumns[i]])
+		columnVars = append(columnVars, columnMap[columns[i]])
 	}
 
 	// deconstruct array of variables and send to Scan
@@ -275,7 +241,7 @@ func (p *Postgresql) accRow(meas_name string, row scanner, acc telegraf.Accumula
 	fields := make(map[string]interface{})
 COLUMN:
 	for col, val := range columnMap {
-		log.Printf("D! postgresql_extensible: column: %s = %T: %s\n", col, *val, *val)
+		log.Printf("D! postgresql_extensible: column: %s = %T: %v\n", col, *val, *val)
 		_, ignore := ignoredColumns[col]
 		if ignore || *val == nil {
 			continue
@@ -310,6 +276,14 @@ COLUMN:
 
 func init() {
 	inputs.Add("postgresql_extensible", func() telegraf.Input {
-		return &Postgresql{}
+		return &Postgresql{
+			Service: postgresql.Service{
+				MaxIdle: 1,
+				MaxOpen: 1,
+				MaxLifetime: internal.Duration{
+					Duration: 0,
+				},
+			},
+		}
 	})
 }

plugins/inputs/postgresql_extensible/postgresql_extensible_test.go

@@ -4,22 +4,28 @@ import (
 	"fmt"
 	"testing"
 
+	"github.com/influxdata/telegraf/plugins/inputs/postgresql"
 	"github.com/influxdata/telegraf/testutil"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
-func queryRunner(t *testing.T, q query) (*Postgresql, *testutil.Accumulator) {
+func queryRunner(t *testing.T, q query) *testutil.Accumulator {
 	p := &Postgresql{
-		Address: fmt.Sprintf("host=%s user=postgres sslmode=disable",
+		Service: postgresql.Service{
-			testutil.GetLocalHost()),
+			Address: fmt.Sprintf(
+				"host=%s user=postgres sslmode=disable",
+				testutil.GetLocalHost(),
+			),
+		},
 		Databases: []string{"postgres"},
 		Query:     q,
 	}
 	var acc testutil.Accumulator
+	p.Start(&acc)
 
 	require.NoError(t, acc.GatherError(p.Gather))
-	return p, &acc
+	return &acc
 }
 
 func TestPostgresqlGeneratesMetrics(t *testing.T) {
@@ -27,18 +33,13 @@ func TestPostgresqlGeneratesMetrics(t *testing.T) {
 		t.Skip("Skipping integration test in short mode")
 	}
 
-	p, acc := queryRunner(t, query{{
+	acc := queryRunner(t, query{{
 		Sqlquery:   "select * from pg_stat_database",
 		Version:    901,
 		Withdbname: false,
 		Tagvalue:   "",
 	}})
 
-	availableColumns := make(map[string]bool)
-	for _, col := range p.AllColumns {
-		availableColumns[col] = true
-	}
-
 	intMetrics := []string{
 		"xact_commit",
 		"xact_rollback",
@@ -71,39 +72,27 @@ func TestPostgresqlGeneratesMetrics(t *testing.T) {
 	metricsCounted := 0
 
 	for _, metric := range intMetrics {
-		_, ok := availableColumns[metric]
-		if ok {
 		assert.True(t, acc.HasInt64Field("postgresql", metric))
 		metricsCounted++
 	}
-	}
 
 	for _, metric := range int32Metrics {
-		_, ok := availableColumns[metric]
-		if ok {
 		assert.True(t, acc.HasInt32Field("postgresql", metric))
 		metricsCounted++
 	}
-	}
 
 	for _, metric := range floatMetrics {
-		_, ok := availableColumns[metric]
-		if ok {
 		assert.True(t, acc.HasFloatField("postgresql", metric))
 		metricsCounted++
 	}
-	}
 
 	for _, metric := range stringMetrics {
-		_, ok := availableColumns[metric]
-		if ok {
 		assert.True(t, acc.HasStringField("postgresql", metric))
 		metricsCounted++
 	}
-	}
 
 	assert.True(t, metricsCounted > 0)
-	assert.Equal(t, len(availableColumns)-len(p.IgnoredColumns()), metricsCounted)
+	assert.Equal(t, len(floatMetrics)+len(intMetrics)+len(int32Metrics)+len(stringMetrics), metricsCounted)
 }
 
 func TestPostgresqlQueryOutputTests(t *testing.T) {
@@ -137,7 +126,7 @@ func TestPostgresqlQueryOutputTests(t *testing.T) {
 	}
 
 	for q, assertions := range examples {
-		_, acc := queryRunner(t, query{{
+		acc := queryRunner(t, query{{
 			Sqlquery:   q,
 			Version:    901,
 			Withdbname: false,
@@ -153,7 +142,7 @@ func TestPostgresqlFieldOutput(t *testing.T) {
 		t.Skip("Skipping integration test in short mode")
 	}
 
-	_, acc := queryRunner(t, query{{
+	acc := queryRunner(t, query{{
 		Sqlquery:   "select * from pg_stat_database",
 		Version:    901,
 		Withdbname: false,
@@ -216,13 +205,18 @@ func TestPostgresqlIgnoresUnwantedColumns(t *testing.T) {
 	}
 
 	p := &Postgresql{
-		Address: fmt.Sprintf("host=%s user=postgres sslmode=disable",
+		Service: postgresql.Service{
-			testutil.GetLocalHost()),
+			Address: fmt.Sprintf(
+				"host=%s user=postgres sslmode=disable",
+				testutil.GetLocalHost(),
+			),
+		},
 	}
 
 	var acc testutil.Accumulator
-	require.NoError(t, acc.GatherError(p.Gather))
 
+	require.NoError(t, p.Start(&acc))
+	require.NoError(t, acc.GatherError(p.Gather))
 	assert.NotEmpty(t, p.IgnoredColumns())
 	for col := range p.IgnoredColumns() {
 		assert.False(t, acc.HasMeasurement(col))