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Use the pg_settings view to retrieve runtime variable

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Adds all bool/integer/real runtime variables that can be retrieved ths way.

Use the `pg_settings` view to retrieve runtime variables:
https://www.postgresql.org/docs/current/static/view-pg-settings.html

Replaces the use of `SHOW` to retrieve runtime variables.

Only runtime variables with a `vartype` of `bool`, `real`, or `integer`
are currently supported. Uses the `short_desc` field as a description.

This commit deprecates the following metric names:
```
pg_runtime_variable_max_connections
pg_runtime_variable_max_files_per_process
pg_runtime_variable_max_function_args
pg_runtime_variable_max_identifier_length
pg_runtime_variable_max_index_keys
pg_runtime_variable_max_locks_per_transaction
pg_runtime_variable_max_pred_locks_per_transaction
pg_runtime_variable_max_prepared_transactions
pg_runtime_variable_max_standby_archive_delay_milliseconds
pg_runtime_variable_max_standby_streaming_delay_milliseconds
pg_runtime_variable_max_wal_senders
```

They are replaced by equivalent names under `pg_settings` with the exception of
```
pg_runtime_variable_max_standby_archive_delay_milliseconds
pg_runtime_variable_max_standby_streaming_delay_milliseconds
```
which are replaced with
```
pg_settings_max_standby_archive_delay_seconds
pg_settings_max_standby_streaming_delay_seconds
```

Adds approximately 195 new metrics, when considered across all supported
PostgreSQL versions.
This commit is contained in:
Matt Bostock 2017-03-27 22:34:22 +01:00 committed by Will Rouesnel
parent 994be318d4
commit 98ba566322
4 changed files with 331 additions and 75 deletions
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132
pg_setting.go Normal file
View File

@ -0,0 +1,132 @@
package main
import (
"database/sql"
"errors"
"fmt"
"math"
"strconv"
"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()
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 = s.name
unit = s.unit
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)
}
func (s *pgSetting) normaliseUnit() (val float64, unit string, err error) {
val, err = strconv.ParseFloat(s.setting, 64)
if err != nil {
return val, unit, errors.New(fmt.Sprintf("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 "kB", "MB", "GB", "TB", "8kB", "16MB":
unit = "bytes"
default:
err = errors.New(fmt.Sprintf("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 "16MB":
val *= math.Pow(2, 24)
}
return
}

191
pg_setting_test.go Normal file
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@ -0,0 +1,191 @@
// +build !integration
package main
import (
dto "github.com/prometheus/client_model/go"
. "gopkg.in/check.v1"
)
type PgSettingSuite struct{}
var _ = Suite(&PgSettingSuite{})
var fixtures = []fixture{
fixture{
p: pgSetting{
name: "seconds_fixture_metric",
setting: "5",
unit: "s",
shortDesc: "Foo foo foo",
vartype: "integer",
},
n: normalised{
val: 5,
unit: "seconds",
err: "",
},
d: "Desc{fqName: \"pg_settings_seconds_fixture_metric_seconds\", help: \"Foo foo foo [Units converted to seconds.]\", constLabels: {}, variableLabels: []}",
v: 5,
},
fixture{
p: pgSetting{
name: "milliseconds_fixture_metric",
setting: "5000",
unit: "ms",
shortDesc: "Foo foo foo",
vartype: "integer",
},
n: normalised{
val: 5,
unit: "seconds",
err: "",
},
d: "Desc{fqName: \"pg_settings_milliseconds_fixture_metric_seconds\", help: \"Foo foo foo [Units converted to seconds.]\", constLabels: {}, variableLabels: []}",
v: 5,
},
fixture{
p: pgSetting{
name: "eight_kb_fixture_metric",
setting: "17",
unit: "8kB",
shortDesc: "Foo foo foo",
vartype: "integer",
},
n: normalised{
val: 139264,
unit: "bytes",
err: "",
},
d: "Desc{fqName: \"pg_settings_eight_kb_fixture_metric_bytes\", help: \"Foo foo foo [Units converted to bytes.]\", constLabels: {}, variableLabels: []}",
v: 139264,
},
fixture{
p: pgSetting{
name: "16_mb_real_fixture_metric",
setting: "3.0",
unit: "16MB",
shortDesc: "Foo foo foo",
vartype: "real",
},
n: normalised{
val: 5.0331648e+07,
unit: "bytes",
err: "",
},
d: "Desc{fqName: \"pg_settings_16_mb_real_fixture_metric_bytes\", help: \"Foo foo foo [Units converted to bytes.]\", constLabels: {}, variableLabels: []}",
v: 5.0331648e+07,
},
fixture{
p: pgSetting{
name: "bool_on_fixture_metric",
setting: "on",
unit: "",
shortDesc: "Foo foo foo",
vartype: "bool",
},
n: normalised{
val: 1,
unit: "",
err: "",
},
d: "Desc{fqName: \"pg_settings_bool_on_fixture_metric\", help: \"Foo foo foo\", constLabels: {}, variableLabels: []}",
v: 1,
},
fixture{
p: pgSetting{
name: "bool_off_fixture_metric",
setting: "off",
unit: "",
shortDesc: "Foo foo foo",
vartype: "bool",
},
n: normalised{
val: 0,
unit: "",
err: "",
},
d: "Desc{fqName: \"pg_settings_bool_off_fixture_metric\", help: \"Foo foo foo\", constLabels: {}, variableLabels: []}",
v: 0,
},
fixture{
p: pgSetting{
name: "special_minus_one_value",
setting: "-1",
unit: "d",
shortDesc: "foo foo foo",
vartype: "integer",
},
n: normalised{
val: -1,
unit: "seconds",
err: "",
},
d: "Desc{fqName: \"pg_settings_special_minus_one_value_seconds\", help: \"foo foo foo [Units converted to seconds.]\", constLabels: {}, variableLabels: []}",
v: -1,
},
fixture{
p: pgSetting{
name: "unknown_unit",
setting: "10",
unit: "nonexistent",
shortDesc: "foo foo foo",
vartype: "integer",
},
n: normalised{
val: 10,
unit: "",
err: `Unknown unit for runtime variable: "nonexistent"`,
},
},
}
func (s *PgSettingSuite) TestNormaliseUnit(c *C) {
for _, f := range fixtures {
switch f.p.vartype {
case "integer", "real":
val, unit, err := f.p.normaliseUnit()
c.Check(val, Equals, f.n.val)
c.Check(unit, Equals, f.n.unit)
if err == nil {
c.Check("", Equals, f.n.err)
} else {
c.Check(err.Error(), Equals, f.n.err)
}
}
}
}
func (s *PgSettingSuite) TestMetric(c *C) {
defer func() {
if r := recover(); r != nil {
if r.(error).Error() != `Unknown unit for runtime variable: "nonexistent"` {
panic(r)
}
}
}()
for _, f := range fixtures {
d := &dto.Metric{}
m := f.p.metric()
m.Write(d)
c.Check(m.Desc().String(), Equals, f.d)
c.Check(d.GetGauge().GetValue(), Equals, f.v)
}
}
type normalised struct {
val float64
unit string
err string
}
type fixture struct {
p pgSetting
n normalised
d string
v float64
}

71
postgres_exporter.go
View File

@ -95,12 +95,6 @@ const (
DURATION ColumnUsage = iota // This column should be interpreted as a text duration (and converted to milliseconds)
)
// Special case matric mappings
const (
// Which metric mapping should be acquired using "SHOW" queries
SHOW_METRIC = "pg_runtime_variables"
)
// Regex used to get the "short-version" from the postgres version field.
var versionRegex = regexp.MustCompile(`^\w+ (\d+\.\d+\.\d+)`)
var lowestSupportedVersion = semver.MustParse("9.1.0")
@ -147,24 +141,6 @@ type MetricMap struct {
conversion func(interface{}) (float64, bool) // Conversion function to turn PG result into float64
}
// Metric descriptors for dynamically created metrics.
var variableMaps = map[string]map[string]ColumnMapping{
"pg_runtime_variable": {
"max_connections": {GAUGE, "Sets the maximum number of concurrent connections.", nil, nil},
"max_files_per_process": {GAUGE, "Sets the maximum number of simultaneously open files for each server process.", nil, nil},
"max_function_args": {GAUGE, "Shows the maximum number of function arguments.", nil, nil},
"max_identifier_length": {GAUGE, "Shows the maximum identifier length.", nil, nil},
"max_index_keys": {GAUGE, "Shows the maximum number of index keys.", nil, nil},
"max_locks_per_transaction": {GAUGE, "Sets the maximum number of locks per transaction.", nil, nil},
"max_pred_locks_per_transaction": {GAUGE, "Sets the maximum number of predicate locks per transaction.", nil, nil},
"max_prepared_transactions": {GAUGE, "Sets the maximum number of simultaneously prepared transactions.", nil, nil},
//"max_stack_depth" : { GAUGE, "Sets the maximum number of concurrent connections.", nil }, // No dehumanize support yet
"max_standby_archive_delay": {DURATION, "Sets the maximum delay before canceling queries when a hot standby server is processing archived WAL data.", nil, nil},
"max_standby_streaming_delay": {DURATION, "Sets the maximum delay before canceling queries when a hot standby server is processing streamed WAL data.", nil, nil},
"max_wal_senders": {GAUGE, "Sets the maximum number of simultaneously running WAL sender processes.", nil, nil},
},
}
// TODO: revisit this with the semver system
func dumpMaps() {
for name, cmap := range metricMaps {
@ -694,8 +670,6 @@ type Exporter struct {
// Last version used to calculate metric map. If mismatch on scrape,
// then maps are recalculated.
lastMapVersion semver.Version
// Currently active variable map
variableMap map[string]MetricMapNamespace
// Currently active metric map
metricMap map[string]MetricMapNamespace
// Currently active query overrides
@ -726,7 +700,6 @@ func NewExporter(dsn string, userQueriesPath string) *Exporter {
Name: "last_scrape_error",
Help: "Whether the last scrape of metrics from PostgreSQL resulted in an error (1 for error, 0 for success).",
}),
variableMap: nil,
metricMap: nil,
queryOverrides: nil,
}
@ -776,42 +749,6 @@ func newDesc(subsystem, name, help string) *prometheus.Desc {
)
}
// Query the SHOW variables from the query map
// TODO: make this more functional
func queryShowVariables(ch chan<- prometheus.Metric, db *sql.DB, variableMap map[string]MetricMapNamespace) []error {
log.Debugln("Querying SHOW variables")
nonFatalErrors := []error{}
for _, mapping := range variableMap {
for columnName, columnMapping := range mapping.columnMappings {
// Check for a discard request on this value
if columnMapping.discard {
continue
}
// Use SHOW to get the value
row := db.QueryRow(fmt.Sprintf("SHOW %s;", columnName))
var val interface{}
err := row.Scan(&val)
if err != nil {
nonFatalErrors = append(nonFatalErrors, errors.New(fmt.Sprintln("Error scanning runtime variable:", columnName, err)))
continue
}
fval, ok := columnMapping.conversion(val)
if !ok {
nonFatalErrors = append(nonFatalErrors, errors.New(fmt.Sprintln("Unexpected error parsing column: ", namespace, columnName, val)))
continue
}
ch <- prometheus.MustNewConstMetric(columnMapping.desc, columnMapping.vtype, fval)
}
}
return nonFatalErrors
}
// Query within a namespace mapping and emit metrics. Returns fatal errors if
// the scrape fails, and a slice of errors if they were non-fatal.
func queryNamespaceMapping(ch chan<- prometheus.Metric, db *sql.DB, namespace string, mapping MetricMapNamespace, queryOverrides map[string]string) ([]error, error) {
@ -942,11 +879,10 @@ func (e *Exporter) checkMapVersions(ch chan<- prometheus.Metric, db *sql.DB) err
semanticVersion, err := parseVersion(versionString)
// Check if semantic version changed and recalculate maps if needed.
if semanticVersion.NE(e.lastMapVersion) || e.variableMap == nil || e.metricMap == nil {
if semanticVersion.NE(e.lastMapVersion) || e.metricMap == nil {
log.Infoln("Semantic Version Changed:", e.lastMapVersion.String(), "->", semanticVersion.String())
e.mappingMtx.Lock()
e.variableMap = makeDescMap(semanticVersion, variableMaps)
e.metricMap = makeDescMap(semanticVersion, metricMaps)
e.queryOverrides = makeQueryOverrideMap(semanticVersion, queryOverrides)
e.lastMapVersion = semanticVersion
@ -1016,9 +952,8 @@ func (e *Exporter) scrape(ch chan<- prometheus.Metric) {
// Lock the exporter maps
e.mappingMtx.RLock()
defer e.mappingMtx.RUnlock()
// Handle querying the show variables
nonFatalErrors := queryShowVariables(ch, db, e.variableMap)
if len(nonFatalErrors) > 0 {
if err := querySettings(ch, db); err != nil {
log.Infof("Error retrieving settings: %s", err)
e.error.Set(1)
}

12
postgres_exporter_integration_test.go
View File

@ -13,6 +13,7 @@ import (
"database/sql"
"fmt"
_ "github.com/lib/pq"
"github.com/prometheus/client_golang/prometheus"
)
@ -57,13 +58,10 @@ func (s *IntegrationSuite) TestAllNamespacesReturnResults(c *C) {
err = s.e.checkMapVersions(ch, db)
c.Assert(err, IsNil)
// Check the show variables work
nonFatalErrors := queryShowVariables(ch, db, s.e.variableMap)
if !c.Check(len(nonFatalErrors), Equals, 0) {
fmt.Println("## NONFATAL ERRORS FOUND")
for _, err := range nonFatalErrors {
fmt.Println(err)
}
err = querySettings(ch, db)
if !c.Check(err, Equals, nil) {
fmt.Println("## ERRORS FOUND")
fmt.Println(err)
}
// This should never happen in our test cases.