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postgresql.go
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postgresql.go
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package postgresql
import (
"bytes"
"database/sql"
"fmt"
"strings"
"github.com/influxdb/telegraf/plugins"
_ "github.com/lib/pq"
)
type Server struct {
Address string
Databases []string
OrderedColumns []string
}
type Postgresql struct {
Servers []*Server
}
var ignoredColumns = map[string]bool{"datid": true, "datname": true, "stats_reset": true}
var sampleConfig = `
# specify servers via an array of tables
[[postgresql.servers]]
# specify address via a url matching:
# postgres://[pqgotest[:password]]@localhost[/dbname]?sslmode=[disable|verify-ca|verify-full]
# or a simple string:
# host=localhost user=pqotest password=... sslmode=... dbname=app_production
#
# All connection parameters are optional. By default, the host is localhost
# and the user is the currently running user. For localhost, we default
# to sslmode=disable as well.
#
# Without the dbname parameter, the driver will default to a database
# with the same name as the user. This dbname is just for instantiating a
# connection with the server and doesn't restrict the databases we are trying
# to grab metrics for.
#
address = "sslmode=disable"
# A list of databases to pull metrics about. If not specified, metrics for all
# databases are gathered.
# databases = ["app_production", "blah_testing"]
# [[postgresql.servers]]
# address = "influx@remoteserver"
`
func (p *Postgresql) SampleConfig() string {
return sampleConfig
}
func (p *Postgresql) Description() string {
return "Read metrics from one or many postgresql servers"
}
func (p *Postgresql) IgnoredColumns() map[string]bool {
return ignoredColumns
}
var localhost = &Server{Address: "sslmode=disable"}
func (p *Postgresql) Gather(acc plugins.Accumulator) error {
if len(p.Servers) == 0 {
p.gatherServer(localhost, acc)
return nil
}
for _, serv := range p.Servers {
err := p.gatherServer(serv, acc)
if err != nil {
return err
}
}
return nil
}
func (p *Postgresql) gatherServer(serv *Server, acc plugins.Accumulator) error {
var query string
if serv.Address == "" || serv.Address == "localhost" {
serv = localhost
}
db, err := sql.Open("postgres", serv.Address)
if err != nil {
return err
}
defer db.Close()
if len(serv.Databases) == 0 {
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()
// grab the column information from the result
serv.OrderedColumns, err = rows.Columns()
if err != nil {
return err
}
for rows.Next() {
err = p.accRow(rows, acc, serv)
if err != nil {
return err
}
}
return rows.Err()
}
type scanner interface {
Scan(dest ...interface{}) error
}
func (p *Postgresql) accRow(row scanner, acc plugins.Accumulator, serv *Server) 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 serv.OrderedColumns {
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[serv.OrderedColumns[i]])
}
// deconstruct array of variables and send to Scan
err := row.Scan(columnVars...)
if err != nil {
return err
}
// extract the database name from the column map
dbnameChars := (*columnMap["datname"]).([]uint8)
for i := 0; i < len(dbnameChars); i++ {
dbname.WriteString(string(dbnameChars[i]))
}
tags := map[string]string{"server": serv.Address, "db": dbname.String()}
for col, val := range columnMap {
_, ignore := ignoredColumns[col]
if !ignore {
acc.Add(col, *val, tags)
}
}
return nil
}
func init() {
plugins.Add("postgresql", func() plugins.Plugin {
return &Postgresql{}
})
}