telegraf/plugins/inputs/postgresql/postgresql.go

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package postgresql
import (
"bytes"
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"database/sql"
"fmt"
"strings"
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"github.com/influxdb/telegraf/plugins/inputs"
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_ "github.com/lib/pq"
)
type Postgresql struct {
Address string
Databases []string
OrderedColumns []string
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}
var ignoredColumns = map[string]bool{"datid": true, "datname": true, "stats_reset": true}
var sampleConfig = `
# 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.
#
# 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.
#
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address = "host=localhost user=postgres sslmode=disable"
# A list of databases to pull metrics about. If not specified, metrics for all
# databases are gathered.
# databases = ["app_production", "testing"]
`
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 = "host=localhost sslmode=disable"
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func (p *Postgresql) Gather(acc inputs.Accumulator) error {
var query string
if p.Address == "" || p.Address == "localhost" {
p.Address = localhost
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}
db, err := sql.Open("postgres", p.Address)
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if err != nil {
return err
}
defer db.Close()
if len(p.Databases) == 0 {
query = `SELECT * FROM pg_stat_database`
} else {
query = fmt.Sprintf(`SELECT * FROM pg_stat_database WHERE datname IN ('%s')`,
strings.Join(p.Databases, "','"))
}
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rows, err := db.Query(query)
if err != nil {
return err
}
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defer rows.Close()
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// grab the column information from the result
p.OrderedColumns, err = rows.Columns()
if err != nil {
return err
}
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for rows.Next() {
err = p.accRow(rows, acc)
if err != nil {
return err
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}
}
return rows.Err()
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}
type scanner interface {
Scan(dest ...interface{}) error
}
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func (p *Postgresql) accRow(row scanner, acc inputs.Accumulator) error {
var columnVars []interface{}
var dbname bytes.Buffer
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// this is where we'll store the column name with its *interface{}
columnMap := make(map[string]*interface{})
for _, column := range p.OrderedColumns {
columnMap[column] = new(interface{})
}
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// 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]])
}
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// deconstruct array of variables and send to Scan
err := row.Scan(columnVars...)
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if err != nil {
return err
}
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// 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": p.Address, "db": dbname.String()}
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fields := make(map[string]interface{})
for col, val := range columnMap {
_, ignore := ignoredColumns[col]
if !ignore {
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fields[col] = *val
}
}
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acc.AddFields("postgresql", fields, tags)
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return nil
}
func init() {
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inputs.Add("postgresql", func() inputs.Input {
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return &Postgresql{}
})
}