Generating metric information dynamically. Makes compatible with postgresql versions < 9.2

plugins/postgresql/postgresql.go

@@ -1,7 +1,10 @@
 package postgresql
 
 import (
+	"bytes"
 	"database/sql"
+	"fmt"
+	"strings"
 
 	"github.com/influxdb/telegraf/plugins"
 
@@ -11,6 +14,7 @@ import (
 type Server struct {
 	Address        string
 	Databases      []string
+	OrderedColumns []string
 }
 
 type Postgresql struct {
@@ -51,6 +55,7 @@ func (p *Postgresql) Description() string {
 }
 
 var localhost = &Server{Address: "sslmode=disable"}
+var ignoredColumns = map[string]bool{"datid": true, "datname": true, "stats_reset": true}
 
 func (p *Postgresql) Gather(acc plugins.Accumulator) error {
 	if len(p.Servers) == 0 {
@@ -69,6 +74,8 @@ func (p *Postgresql) Gather(acc plugins.Accumulator) error {
 }
 
 func (p *Postgresql) gatherServer(serv *Server, acc plugins.Accumulator) error {
+	var query string
+
 	if serv.Address == "" || serv.Address == "localhost" {
 		serv = localhost
 	}
@@ -81,77 +88,69 @@ func (p *Postgresql) gatherServer(serv *Server, acc plugins.Accumulator) error {
 	defer db.Close()
 
 	if len(serv.Databases) == 0 {
-		rows, err := db.Query(`SELECT * FROM pg_stat_database`)
+		query = `SELECT * FROM pg_stat_database`
+	} else {
+		query = fmt.Sprintf(`SELECT * FROM pg_stat_database WHERE datname IN ('%s')`, strings.Join(serv.Databases, "','"))
+	}
+
+	rows, err := db.Query(query)
 	if err != nil {
 		return err
 	}
 
 	defer rows.Close()
 
+	serv.OrderedColumns, err = rows.Columns()
+	if err != nil {
+		return err
+	}
+
 	for rows.Next() {
-			err := p.accRow(rows, acc, serv.Address)
+		err := p.accRow(rows, acc, serv)
 		if err != nil {
 			return err
 		}
 	}
 
 	return rows.Err()
-	} else {
-		for _, name := range serv.Databases {
-			row := db.QueryRow(`SELECT * FROM pg_stat_database WHERE datname=$1`, name)
-
-			err := p.accRow(row, acc, serv.Address)
-			if err != nil {
-				return err
-			}
-		}
-	}
-
-	return nil
 }
 
 type scanner interface {
 	Scan(dest ...interface{}) error
 }
 
-func (p *Postgresql) accRow(row scanner, acc plugins.Accumulator, server string) error {
+func (p *Postgresql) accRow(row scanner, acc plugins.Accumulator, serv *Server) error {
-	var ignore interface{}
+	var columnVars []interface{}
-	var name string
+	var dbname bytes.Buffer
-	var commit, rollback, read, hit int64
-	var returned, fetched, inserted, updated, deleted int64
-	var conflicts, temp_files, temp_bytes, deadlocks int64
-	var read_time, write_time float64
 
-	err := row.Scan(&ignore, &name, &ignore,
+	columnMap := make(map[string]*interface{})
-		&commit, &rollback,
+
-		&read, &hit,
+	for _, column := range serv.OrderedColumns {
-		&returned, &fetched, &inserted, &updated, &deleted,
+		columnMap[column] = new(interface{})
-		&conflicts, &temp_files, &temp_bytes,
+	}
-		&deadlocks, &read_time, &write_time,
+
-		&ignore,
+	for i := 0; i < len(columnMap); i++ {
-	)
+		columnVars = append(columnVars, columnMap[serv.OrderedColumns[i]])
+	}
+
+	err := row.Scan(columnVars...)
 
 	if err != nil {
 		return err
 	}
 
-	tags := map[string]string{"server": server, "db": name}
+	dbnameChars := (*columnMap["datname"]).([]uint8)
+	for i := 0; i < len(dbnameChars); i++ {
+		dbname.WriteString(string(dbnameChars[i]))
+	}
 
-	acc.Add("xact_commit", commit, tags)
+	tags := map[string]string{"server": serv.Address, "db": dbname.String()}
-	acc.Add("xact_rollback", rollback, tags)
+
-	acc.Add("blks_read", read, tags)
+	for col, val := range columnMap {
-	acc.Add("blks_hit", hit, tags)
+		if !ignoredColumns[col] {
-	acc.Add("tup_returned", returned, tags)
+			acc.Add(col, *val, tags)
-	acc.Add("tup_fetched", fetched, tags)
+		}
-	acc.Add("tup_inserted", inserted, tags)
+	}
-	acc.Add("tup_updated", updated, tags)
-	acc.Add("tup_deleted", deleted, tags)
-	acc.Add("conflicts", conflicts, tags)
-	acc.Add("temp_files", temp_files, tags)
-	acc.Add("temp_bytes", temp_bytes, tags)
-	acc.Add("deadlocks", deadlocks, tags)
-	acc.Add("blk_read_time", read_time, tags)
-	acc.Add("blk_write_time", read_time, tags)
 
 	return nil
 }

plugins/postgresql/postgresql_test.go

@@ -117,3 +117,34 @@ func TestPostgresqlDefaultsToAllDatabases(t *testing.T) {
 
 	assert.True(t, found)
 }
+
+func TestPostgresqlIgnoresUnwantedColumns(t *testing.T) {
+	// if testing.Short() {
+	// 	t.Skip("Skipping integration test in short mode")
+	// }
+
+	p := &Postgresql{
+		Servers: []*Server{
+			{
+				Address: fmt.Sprintf("host=%s user=postgres sslmode=disable",
+					testutil.GetLocalHost()),
+			},
+		},
+	}
+
+	var acc testutil.Accumulator
+
+	err := p.Gather(&acc)
+	require.NoError(t, err)
+
+	var found bool
+
+	for _, pnt := range acc.Points {
+		if pnt.Measurement == "datname" || pnt.Measurement == "datid" || pnt.Measurement == "stats_reset" {
+			found = true
+			break
+		}
+	}
+
+	assert.False(t, found)
+}