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mattbostockwrouesnel
mattbostock
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wrouesnel
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Use the pg_settings view to retrieve runtime variable
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.
1 parent 994be31 commit 98ba566

4 files changed

+331
-75
lines changed

‎pg_setting.go

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

‎pg_setting_test.go

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

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