Add arbitrary labels on a per-database basis (#287)

* Adding arbitrary per-database labels as per #275
* Adjusting per-DB label assignments:
* Ensuring the list of allConstLabels is part of the exporter now, and it's passed into the Database each time its needed in there.
* Adjusting the format of the label/value from a list of name/value pairs to a map of strings.

Author: neilschelly

README.md

@@ -721,6 +721,12 @@ databases:
     ## Oracle Database Connection pool minimum size
     # poolMinConnections: 15
 
+    ## Arbitrary labels to add to each metric scraped from this database
+    # labels:
+    #   label_name1: label_value1
+    #   label_name2: label_value2
+
+
 metrics:
   ## How often to scrape metrics. If not provided, metrics will be scraped on request.
   # scrapeInterval: 15s
@@ -791,6 +797,16 @@ databases:
     # poolMaxConnections: 15
     ## Oracle Database Connection pool minimum size
     # poolMinConnections: 15
+
+    ### Arbitrary labels to add to each metric scraped from this database
+    ## Any labels configured for one database will be added to metrics from
+    ## every database, because the same metric names must always have the same
+    ## full labelset. If the label isn't set for a particular database, then it
+    ## will just be set to an empty string.
+    # labels:
+    #   label_name1: label_value1
+    #   label_name2: label_value2
+
   db2:
     ## Database username
     username: ${DB2_USERNAME}
@@ -828,6 +844,15 @@ databases:
     ## Oracle Database Connection pool minimum size
     # poolMinConnections: 15
 
+    ### Arbitrary labels to add to each metric scraped from this database
+    ## Any labels configured for one database will be added to metrics from
+    ## every database, because the same metric names must always have the same
+    ## full labelset. If the label isn't set for a particular database, then it
+    ## will just be set to an empty string.
+    # labels:
+    #   label_name1: label_value1
+    #   label_name2: label_value2
+
 metrics:
   ## How often to scrape metrics. If not provided, metrics will be scraped on request.
   # scrapeInterval: 15s

collector/collector.go

@@ -14,6 +14,7 @@ import (
 	"io"
 	"log/slog"
 	"os"
+	"slices"
 	"strconv"
 	"strings"
 	"sync"
@@ -50,6 +51,20 @@ func maskDsn(dsn string) string {
 func NewExporter(logger *slog.Logger, m *MetricsConfiguration) *Exporter {
 	var databases []*Database
 	wg := &sync.WaitGroup{}
+
+	var allConstLabels []string
+	// All the metrics of the same name need to have the same set of labels
+	// If a label is set for a particular database, it must be included also
+	// in the same metrics collected from other databases. It will just be
+	// set to a blank value.
+	for _, dbconfig := range m.Databases {
+		for label, _ := range dbconfig.Labels {
+			if (!slices.Contains(allConstLabels, label)) {
+				allConstLabels = append(allConstLabels, label)
+			}
+		}
+	}
+
 	for dbname, dbconfig := range m.Databases {
 		logger.Info("Initializing database", "database", dbname)
 		database := NewDatabase(logger, dbname, dbconfig)
@@ -91,12 +106,25 @@ func NewExporter(logger *slog.Logger, m *MetricsConfiguration) *Exporter {
 		MetricsConfiguration: m,
 		databases:            databases,
 		lastScraped:          map[string]*time.Time{},
+		allConstLabels:       allConstLabels,
 	}
 	e.metricsToScrape = e.DefaultMetrics()
 
 	return e
 }
 
+func (e *Exporter) constLabels() map[string]string {
+	// All the metrics of the same name need to have the same labels
+	// If a label is set for a particular database, it must be included also
+	// in the same metrics collected from other databases. It will just be
+	// set to a blank value.
+	labels := map[string]string{}
+	for _, label := range e.allConstLabels {
+		labels[label] = ""
+	}
+	return labels
+}
+
 // Describe describes all the metrics exported by the Oracle DB exporter.
 func (e *Exporter) Describe(ch chan<- *prometheus.Desc) {
 	// We cannot know in advance what metrics the exporter will generate
@@ -148,8 +176,8 @@ func (e *Exporter) Collect(ch chan<- prometheus.Metric) {
 	ch <- e.error
 	e.scrapeErrors.Collect(ch)
 	for _, db := range e.databases {
-		ch <- db.DBTypeMetric()
-		ch <- db.UpMetric()
+		ch <- db.DBTypeMetric(e.constLabels())
+		ch <- db.UpMetric(e.constLabels())
 	}
 }
 
@@ -203,7 +231,7 @@ func (e *Exporter) scheduledScrape(tick *time.Time) {
 	metricCh <- e.error
 	e.scrapeErrors.Collect(metricCh)
 	for _, db := range e.databases {
-		metricCh <- db.UpMetric()
+		metricCh <- db.UpMetric(e.constLabels())
 	}
 	close(metricCh)
 	wg.Wait()
@@ -399,7 +427,8 @@ func (e *Exporter) scrapeGenericValues(d *Database, ch chan<- prometheus.Metric,
 	metricsDesc map[string]string, metricsType map[string]string, metricsBuckets map[string]map[string]string,
 	fieldToAppend string, ignoreZeroResult bool, request string, queryTimeout time.Duration) error {
 	metricsCount := 0
-	constLabels := d.constLabels()
+	constLabels := d.constLabels(e.constLabels())
+	e.logger.Debug("labels", constLabels)
 	genericParser := func(row map[string]string) error {
 		// Construct labels value
 		labelsValues := []string{}

collector/config.go

@@ -27,6 +27,7 @@ type DatabaseConfig struct {
 	URL           string `yaml:"url"`
 	ConnectConfig `yaml:",inline"`
 	Vault         *VaultConfig `yaml:"vault,omitempty"`
+	Labels        map[string]string `yaml:"labels,omitempty"`
 }
 
 type ConnectConfig struct {

collector/database.go

@@ -15,25 +15,25 @@ import (
 	"time"
 )
 
-func (d *Database) UpMetric() prometheus.Metric {
+func (d *Database) UpMetric(exporterLabels map[string]string) prometheus.Metric {
 	desc := prometheus.NewDesc(
 		prometheus.BuildFQName(namespace, "", "up"),
 		"Whether the Oracle database server is up.",
 		nil,
-		d.constLabels(),
+		d.constLabels(exporterLabels),
 	)
 	return prometheus.MustNewConstMetric(desc,
 		prometheus.GaugeValue,
 		d.Up,
 	)
 }
 
-func (d *Database) DBTypeMetric() prometheus.Metric {
+func (d *Database) DBTypeMetric(exporterLabels map[string]string) prometheus.Metric {
 	desc := prometheus.NewDesc(
 		prometheus.BuildFQName(namespace, "", "dbtype"),
 		"Type of database the exporter is connected to (0=non-CDB, 1=CDB, >1=PDB).",
 		nil,
-		d.constLabels(),
+		d.constLabels(exporterLabels),
 	)
 	return prometheus.MustNewConstMetric(desc,
 		prometheus.GaugeValue,
@@ -65,20 +65,24 @@ func (d *Database) ping(logger *slog.Logger) error {
 	return nil
 }
 
-func (d *Database) constLabels() map[string]string {
-	return map[string]string{
-		"database": d.Name,
+func (d *Database) constLabels(labels map[string]string) map[string]string {
+	labels["database"] = d.Name
+
+	// configured per-database labels added to constLabels
+	for label, value := range d.Config.Labels {
+		labels[label] = value
 	}
+	return labels
 }
 
 func NewDatabase(logger *slog.Logger, dbname string, dbconfig DatabaseConfig) *Database {
 	db, dbtype := connect(logger, dbname, dbconfig)
 	return &Database{
-		Name:    dbname,
-		Up:      0,
-		Session: db,
-		Type:    dbtype,
-		Config:  dbconfig,
+		Name:            dbname,
+		Up:              0,
+		Session:         db,
+		Type:            dbtype,
+		Config:          dbconfig,
 	}
 }
 

collector/types.go

@@ -24,14 +24,15 @@ type Exporter struct {
 	databases       []*Database
 	logger          *slog.Logger
 	lastScraped     map[string]*time.Time
+	allConstLabels  []string
 }
 
 type Database struct {
-	Name    string
-	Up      float64
-	Session *sql.DB
-	Type    float64
-	Config  DatabaseConfig
+	Name            string
+	Up              float64
+	Session         *sql.DB
+	Type            float64
+	Config          DatabaseConfig
 }
 
 type Config struct {

example-config-multi-database.yaml

@@ -45,6 +45,12 @@ databases:
     # poolMaxConnections: 15
     ## Oracle Database Connection pool minimum size
     # poolMinConnections: 15
+
+    ## Arbitrary labels to add to each metric scraped from this database
+    # labels:
+    #   label_name1: label_value1
+    #   label_name2: label_value2
+
   db2:
     ## Database username
     username: ${DB2_USERNAME}
@@ -82,6 +88,11 @@ databases:
     ## Oracle Database Connection pool minimum size
     # poolMinConnections: 15
 
+    ## Arbitrary labels to add to each metric scraped from this database
+    # labels:
+    #   label_name1: label_value1
+    #   label_name2: label_value2
+
 metrics:
   ## How often to scrape metrics. If not provided, metrics will be scraped on request.
   # scrapeInterval: 15s