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package main
import (
"database/sql"
"errors"
"fmt"
"math"
"strconv"
"strings"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/common/log"
)
// Query the pg_settings view containing runtime variables
func querySettings(ch chan<- prometheus.Metric, db *sql.DB) error {
log.Debugln("Querying pg_setting view")
// pg_settings docs: https://www.postgresql.org/docs/current/static/view-pg-settings.html
//
// NOTE: If you add more vartypes here, you must update the supported
// types in normaliseUnit() below
query := "SELECT name, setting, COALESCE(unit, ''), short_desc, vartype FROM pg_settings WHERE vartype IN ('bool', 'integer', 'real');"
rows, err := db.Query(query)
if err != nil {
return errors.New(fmt.Sprintln("Error running query on database: ", namespace, err))
}
defer rows.Close() // nolint: errcheck
for rows.Next() {
s := &pgSetting{}
err = rows.Scan(&s.name, &s.setting, &s.unit, &s.shortDesc, &s.vartype)
if err != nil {
return errors.New(fmt.Sprintln("Error retrieving rows:", namespace, err))
}
ch <- s.metric()
}
return nil
}
// pgSetting is represents a PostgreSQL runtime variable as returned by the
// pg_settings view.
type pgSetting struct {
name, setting, unit, shortDesc, vartype string
}
func (s *pgSetting) metric() prometheus.Metric {
var (
err error
name = strings.Replace(s.name, ".", "_", -1)
unit = s.unit // nolint: ineffassign
shortDesc = s.shortDesc
subsystem = "settings"
val float64
)
switch s.vartype {
case "bool":
if s.setting == "on" {
val = 1
}
case "integer", "real":
if val, unit, err = s.normaliseUnit(); err != nil {
// Panic, since we should recognise all units
// and don't want to silently exlude metrics
panic(err)
}
if len(unit) > 0 {
name = fmt.Sprintf("%s_%s", name, unit)
shortDesc = fmt.Sprintf("%s [Units converted to %s.]", shortDesc, unit)
}
default:
// Panic because we got a type we didn't ask for
panic(fmt.Sprintf("Unsupported vartype %q", s.vartype))
}
desc := newDesc(subsystem, name, shortDesc)
return prometheus.MustNewConstMetric(desc, prometheus.GaugeValue, val)
}
// TODO: fix linter override
// nolint: nakedret
func (s *pgSetting) normaliseUnit() (val float64, unit string, err error) {
val, err = strconv.ParseFloat(s.setting, 64)
if err != nil {
return val, unit, fmt.Errorf("Error converting setting %q value %q to float: %s", s.name, s.setting, err)
}
// Units defined in: https://www.postgresql.org/docs/current/static/config-setting.html
switch s.unit {
case "":
return
case "ms", "s", "min", "h", "d":
unit = "seconds"
case "B", "kB", "MB", "GB", "TB", "8kB", "16kB", "32kB", "16MB", "32MB", "64MB":
unit = "bytes"
default:
err = fmt.Errorf("Unknown unit for runtime variable: %q", s.unit)
return
}
// -1 is special, don't modify the value
if val == -1 {
return
}
switch s.unit {
case "ms":
val /= 1000
case "min":
val *= 60
case "h":
val *= 60 * 60
case "d":
val *= 60 * 60 * 24
case "kB":
val *= math.Pow(2, 10)
case "MB":
val *= math.Pow(2, 20)
case "GB":
val *= math.Pow(2, 30)
case "TB":
val *= math.Pow(2, 40)
case "8kB":
val *= math.Pow(2, 13)
case "16kB":
val *= math.Pow(2, 14)
case "32kB":
val *= math.Pow(2, 15)
case "16MB":
val *= math.Pow(2, 24)
case "32MB":
val *= math.Pow(2, 25)
case "64MB":
val *= math.Pow(2, 26)
}
return
}
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