server labels are defined as const labels

README.md

@@ -121,9 +121,9 @@ For running it locally on a default Debian/Ubuntu install, this will work (trans
 
     sudo -u postgres DATA_SOURCE_NAME="user=postgres host=/var/run/postgresql/ sslmode=disable" postgres_exporter
 
-Also, you can set a list of sources to scrape different instances from the one exporter setup. Just define a string separated by comma.
+Also, you can set a list of sources to scrape different instances from the one exporter setup. Just define a comma separated string.
 
-    sudo -u postgres DATA_SOURCE_NAME="port=5432, port=6432" postgres_exporter
+    sudo -u postgres DATA_SOURCE_NAME="port=5432,port=6432" postgres_exporter
 
 See the [github.com/lib/pq](http://github.com/lib/pq) module for other ways to format the connection string.
 
@@ -155,7 +155,8 @@ flag. This removes all built-in metrics, and uses only metrics defined by querie
 
 ### Running as non-superuser
 
-To be able to collect metrics from pg_stat_activity and pg_stat_replication as non-superuser you have to create views as a superuser, and assign permissions separately to those.  In PostgreSQL, views run with the permissions of the user that created them so they can act as security barriers.
+To be able to collect metrics from `pg_stat_activity` and `pg_stat_replication` as non-superuser you have to create views as a superuser, and assign permissions separately to those.
+In PostgreSQL, views run with the permissions of the user that created them so they can act as security barriers.
 
 ```sql
 CREATE USER postgres_exporter PASSWORD 'password';

cmd/postgres_exporter/pg_setting.go

@@ -33,7 +33,7 @@ func querySettings(ch chan<- prometheus.Metric, server *Server) error {
 			return fmt.Errorf("Error retrieving rows on %q: %s %v", server, namespace, err)
 		}
 
-		ch <- s.metric(server.String())
+		ch <- s.metric(server.labels)
 	}
 
 	return nil
@@ -45,7 +45,7 @@ type pgSetting struct {
 	name, setting, unit, shortDesc, vartype string
 }
 
-func (s *pgSetting) metric(server string) prometheus.Metric {
+func (s *pgSetting) metric(labels prometheus.Labels) prometheus.Metric {
 	var (
 		err       error
 		name      = strings.Replace(s.name, ".", "_", -1)
@@ -76,8 +76,8 @@ func (s *pgSetting) metric(server string) prometheus.Metric {
 		panic(fmt.Sprintf("Unsupported vartype %q", s.vartype))
 	}
 
-	desc := newDesc(subsystem, name, shortDesc)
-	return prometheus.MustNewConstMetric(desc, prometheus.GaugeValue, val, server)
+	desc := newDesc(subsystem, name, shortDesc, labels)
+	return prometheus.MustNewConstMetric(desc, prometheus.GaugeValue, val)
 }
 
 // TODO: fix linter override

cmd/postgres_exporter/pg_setting_test.go

@@ -3,6 +3,7 @@
 package main
 
 import (
+	"github.com/prometheus/client_golang/prometheus"
 	dto "github.com/prometheus/client_model/go"
 	. "gopkg.in/check.v1"
 )
@@ -25,7 +26,7 @@ var fixtures = []fixture{
 			unit: "seconds",
 			err:  "",
 		},
-		d: `Desc{fqName: "pg_settings_seconds_fixture_metric_seconds", help: "Foo foo foo [Units converted to seconds.]", constLabels: {}, variableLabels: [` + serverLabelName + `]}`,
+		d: `Desc{fqName: "pg_settings_seconds_fixture_metric_seconds", help: "Foo foo foo [Units converted to seconds.]", constLabels: {}, variableLabels: []}`,
 		v: 5,
 	},
 	{
@@ -41,7 +42,7 @@ var fixtures = []fixture{
 			unit: "seconds",
 			err:  "",
 		},
-		d: `Desc{fqName: "pg_settings_milliseconds_fixture_metric_seconds", help: "Foo foo foo [Units converted to seconds.]", constLabels: {}, variableLabels: [` + serverLabelName + `]}`,
+		d: `Desc{fqName: "pg_settings_milliseconds_fixture_metric_seconds", help: "Foo foo foo [Units converted to seconds.]", constLabels: {}, variableLabels: []}`,
 		v: 5,
 	},
 	{
@@ -57,7 +58,7 @@ var fixtures = []fixture{
 			unit: "bytes",
 			err:  "",
 		},
-		d: `Desc{fqName: "pg_settings_eight_kb_fixture_metric_bytes", help: "Foo foo foo [Units converted to bytes.]", constLabels: {}, variableLabels: [` + serverLabelName + `]}`,
+		d: `Desc{fqName: "pg_settings_eight_kb_fixture_metric_bytes", help: "Foo foo foo [Units converted to bytes.]", constLabels: {}, variableLabels: []}`,
 		v: 139264,
 	},
 	{
@@ -73,7 +74,7 @@ var fixtures = []fixture{
 			unit: "bytes",
 			err:  "",
 		},
-		d: `Desc{fqName: "pg_settings_16_kb_real_fixture_metric_bytes", help: "Foo foo foo [Units converted to bytes.]", constLabels: {}, variableLabels: [` + serverLabelName + `]}`,
+		d: `Desc{fqName: "pg_settings_16_kb_real_fixture_metric_bytes", help: "Foo foo foo [Units converted to bytes.]", constLabels: {}, variableLabels: []}`,
 		v: 49152,
 	},
 	{
@@ -89,7 +90,7 @@ var fixtures = []fixture{
 			unit: "bytes",
 			err:  "",
 		},
-		d: `Desc{fqName: "pg_settings_16_mb_real_fixture_metric_bytes", help: "Foo foo foo [Units converted to bytes.]", constLabels: {}, variableLabels: [` + serverLabelName + `]}`,
+		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,
 	},
 	{
@@ -105,7 +106,7 @@ var fixtures = []fixture{
 			unit: "bytes",
 			err:  "",
 		},
-		d: `Desc{fqName: "pg_settings_32_mb_real_fixture_metric_bytes", help: "Foo foo foo [Units converted to bytes.]", constLabels: {}, variableLabels: [` + serverLabelName + `]}`,
+		d: `Desc{fqName: "pg_settings_32_mb_real_fixture_metric_bytes", help: "Foo foo foo [Units converted to bytes.]", constLabels: {}, variableLabels: []}`,
 		v: 1.00663296e+08,
 	},
 	{
@@ -121,7 +122,7 @@ var fixtures = []fixture{
 			unit: "bytes",
 			err:  "",
 		},
-		d: `Desc{fqName: "pg_settings_64_mb_real_fixture_metric_bytes", help: "Foo foo foo [Units converted to bytes.]", constLabels: {}, variableLabels: [` + serverLabelName + `]}`,
+		d: `Desc{fqName: "pg_settings_64_mb_real_fixture_metric_bytes", help: "Foo foo foo [Units converted to bytes.]", constLabels: {}, variableLabels: []}`,
 		v: 2.01326592e+08,
 	},
 	{
@@ -137,7 +138,7 @@ var fixtures = []fixture{
 			unit: "",
 			err:  "",
 		},
-		d: `Desc{fqName: "pg_settings_bool_on_fixture_metric", help: "Foo foo foo", constLabels: {}, variableLabels: [` + serverLabelName + `]}`,
+		d: `Desc{fqName: "pg_settings_bool_on_fixture_metric", help: "Foo foo foo", constLabels: {}, variableLabels: []}`,
 		v: 1,
 	},
 	{
@@ -153,7 +154,7 @@ var fixtures = []fixture{
 			unit: "",
 			err:  "",
 		},
-		d: `Desc{fqName: "pg_settings_bool_off_fixture_metric", help: "Foo foo foo", constLabels: {}, variableLabels: [` + serverLabelName + `]}`,
+		d: `Desc{fqName: "pg_settings_bool_off_fixture_metric", help: "Foo foo foo", constLabels: {}, variableLabels: []}`,
 		v: 0,
 	},
 	{
@@ -169,7 +170,7 @@ var fixtures = []fixture{
 			unit: "seconds",
 			err:  "",
 		},
-		d: `Desc{fqName: "pg_settings_special_minus_one_value_seconds", help: "foo foo foo [Units converted to seconds.]", constLabels: {}, variableLabels: [` + serverLabelName + `]}`,
+		d: `Desc{fqName: "pg_settings_special_minus_one_value_seconds", help: "foo foo foo [Units converted to seconds.]", constLabels: {}, variableLabels: []}`,
 		v: -1,
 	},
 	{
@@ -185,7 +186,7 @@ var fixtures = []fixture{
 			unit: "",
 			err:  "",
 		},
-		d: `Desc{fqName: "pg_settings_rds_rds_superuser_reserved_connections", help: "Sets the number of connection slots reserved for rds_superusers.", constLabels: {}, variableLabels: [` + serverLabelName + `]}`,
+		d: `Desc{fqName: "pg_settings_rds_rds_superuser_reserved_connections", help: "Sets the number of connection slots reserved for rds_superusers.", constLabels: {}, variableLabels: []}`,
 		v: 2,
 	},
 	{
@@ -233,7 +234,7 @@ func (s *PgSettingSuite) TestMetric(c *C) {
 
 	for _, f := range fixtures {
 		d := &dto.Metric{}
-		m := f.p.metric("")
+		m := f.p.metric(prometheus.Labels{})
 		m.Write(d) // nolint: errcheck
 
 		c.Check(m.Desc().String(), Equals, f.d)

cmd/postgres_exporter/postgres_exporter.go

@@ -452,7 +452,7 @@ func addQueries(content []byte, pgVersion semver.Version, server *Server) error
 	}
 
 	// Convert the loaded metric map into exporter representation
-	partialExporterMap := makeDescMap(pgVersion, metricMaps)
+	partialExporterMap := makeDescMap(pgVersion, server.labels, metricMaps)
 
 	// Merge the two maps (which are now quite flatteend)
 	for k, v := range partialExporterMap {
@@ -480,15 +480,15 @@ func addQueries(content []byte, pgVersion semver.Version, server *Server) error
 }
 
 // Turn the MetricMap column mapping into a prometheus descriptor mapping.
-func makeDescMap(pgVersion semver.Version, metricMaps map[string]map[string]ColumnMapping) map[string]MetricMapNamespace {
+func makeDescMap(pgVersion semver.Version, serverLabels prometheus.Labels, metricMaps map[string]map[string]ColumnMapping) map[string]MetricMapNamespace {
 	var metricMap = make(map[string]MetricMapNamespace)
 
 	for namespace, mappings := range metricMaps {
 		thisMap := make(map[string]MetricMap)
 
 		// Get the constant labels.
 		// Server label must be added to each metric.
-		constLabels := []string{serverLabelName}
+		var constLabels []string
 		for columnName, columnMapping := range mappings {
 			if columnMapping.usage == LABEL {
 				constLabels = append(constLabels, columnName)
@@ -526,23 +526,23 @@ func makeDescMap(pgVersion semver.Version, metricMaps map[string]map[string]Colu
 			case COUNTER:
 				thisMap[columnName] = MetricMap{
 					vtype: prometheus.CounterValue,
-					desc:  prometheus.NewDesc(fmt.Sprintf("%s_%s", namespace, columnName), columnMapping.description, constLabels, nil),
+					desc:  prometheus.NewDesc(fmt.Sprintf("%s_%s", namespace, columnName), columnMapping.description, constLabels, serverLabels),
 					conversion: func(in interface{}) (float64, bool) {
 						return dbToFloat64(in)
 					},
 				}
 			case GAUGE:
 				thisMap[columnName] = MetricMap{
 					vtype: prometheus.GaugeValue,
-					desc:  prometheus.NewDesc(fmt.Sprintf("%s_%s", namespace, columnName), columnMapping.description, constLabels, nil),
+					desc:  prometheus.NewDesc(fmt.Sprintf("%s_%s", namespace, columnName), columnMapping.description, constLabels, serverLabels),
 					conversion: func(in interface{}) (float64, bool) {
 						return dbToFloat64(in)
 					},
 				}
 			case MAPPEDMETRIC:
 				thisMap[columnName] = MetricMap{
 					vtype: prometheus.GaugeValue,
-					desc:  prometheus.NewDesc(fmt.Sprintf("%s_%s", namespace, columnName), columnMapping.description, constLabels, nil),
+					desc:  prometheus.NewDesc(fmt.Sprintf("%s_%s", namespace, columnName), columnMapping.description, constLabels, serverLabels),
 					conversion: func(in interface{}) (float64, bool) {
 						text, ok := in.(string)
 						if !ok {
@@ -559,7 +559,7 @@ func makeDescMap(pgVersion semver.Version, metricMaps map[string]map[string]Colu
 			case DURATION:
 				thisMap[columnName] = MetricMap{
 					vtype: prometheus.GaugeValue,
-					desc:  prometheus.NewDesc(fmt.Sprintf("%s_%s_milliseconds", namespace, columnName), columnMapping.description, constLabels, nil),
+					desc:  prometheus.NewDesc(fmt.Sprintf("%s_%s_milliseconds", namespace, columnName), columnMapping.description, constLabels, serverLabels),
 					conversion: func(in interface{}) (float64, bool) {
 						var durationString string
 						switch t := in.(type) {
@@ -725,8 +725,8 @@ func parseDSN(dsn string) (*url.URL, error) {
 // Server describes a connection to Postgres.
 // Also it contains metrics map and query overrides.
 type Server struct {
-	db          *sql.DB
-	fingerprint string
+	db     *sql.DB
+	labels prometheus.Labels
 
 	// Last version used to calculate metric map. If mismatch on scrape,
 	// then maps are recalculated.
@@ -755,8 +755,10 @@ func NewServer(dsn string) (*Server, error) {
 	log.Infof("Established new database connection to %q.", fingerprint)
 
 	return &Server{
-		db:          db,
-		fingerprint: fingerprint,
+		db: db,
+		labels: prometheus.Labels{
+			serverLabelName: fingerprint,
+		},
 	}, nil
 }
 
@@ -784,7 +786,7 @@ func (s *Server) Ping() error {
 
 // String returns server's fingerprint.
 func (s *Server) String() string {
-	return s.fingerprint
+	return s.labels[serverLabelName]
 }
 
 // Scrape loads metrics.
@@ -976,10 +978,10 @@ func (e *Exporter) Collect(ch chan<- prometheus.Metric) {
 	e.userQueriesError.Collect(ch)
 }
 
-func newDesc(subsystem, name, help string) *prometheus.Desc {
+func newDesc(subsystem, name, help string, labels prometheus.Labels) *prometheus.Desc {
 	return prometheus.NewDesc(
 		prometheus.BuildFQName(namespace, subsystem, name),
-		help, []string{serverLabelName}, nil,
+		help, nil, labels,
 	)
 }
 
@@ -1040,9 +1042,8 @@ func queryNamespaceMapping(ch chan<- prometheus.Metric, server *Server, namespac
 
 		// Get the label values for this row.
 		labels := make([]string, len(mapping.labels))
-		labels[0] = server.String() // Server label must be added to each metric.
-		for idx := 1; idx < len(mapping.labels); idx++ {
-			labels[idx], _ = dbToString(columnData[columnIdx[mapping.labels[idx]]])
+		for idx, label := range mapping.labels {
+			labels[idx], _ = dbToString(columnData[columnIdx[label]])
 		}
 
 		// Loop over column names, and match to scan data. Unknown columns
@@ -1133,7 +1134,7 @@ func (e *Exporter) checkMapVersions(ch chan<- prometheus.Metric, server *Server)
 			server.metricMap = make(map[string]MetricMapNamespace)
 			server.queryOverrides = make(map[string]string)
 		} else {
-			server.metricMap = makeDescMap(semanticVersion, e.builtinMetricMaps)
+			server.metricMap = makeDescMap(semanticVersion, server.labels, e.builtinMetricMaps)
 			server.queryOverrides = makeQueryOverrideMap(semanticVersion, queryOverrides)
 		}
 
@@ -1166,10 +1167,10 @@ func (e *Exporter) checkMapVersions(ch chan<- prometheus.Metric, server *Server)
 
 	// Output the version as a special metric
 	versionDesc := prometheus.NewDesc(fmt.Sprintf("%s_%s", namespace, staticLabelName),
-		"Version string as reported by postgres", []string{serverLabelName, "version", "short_version"}, nil)
+		"Version string as reported by postgres", []string{"version", "short_version"}, server.labels)
 
 	ch <- prometheus.MustNewConstMetric(versionDesc,
-		prometheus.UntypedValue, 1, server.String(), versionString, semanticVersion.String())
+		prometheus.UntypedValue, 1, versionString, semanticVersion.String())
 	return nil
 }
 

cmd/postgres_exporter/postgres_exporter_test.go

@@ -10,6 +10,7 @@ import (
 	"os"
 
 	"github.com/blang/semver"
+	"github.com/prometheus/client_golang/prometheus"
 )
 
 // Hook up gocheck into the "go test" runner.
@@ -34,7 +35,7 @@ func (s *FunctionalSuite) TestSemanticVersionColumnDiscard(c *C) {
 
 	{
 		// No metrics should be eliminated
-		resultMap := makeDescMap(semver.MustParse("0.0.1"), testMetricMap)
+		resultMap := makeDescMap(semver.MustParse("0.0.1"), prometheus.Labels{}, testMetricMap)
 		c.Check(
 			resultMap["test_namespace"].columnMappings["metric_which_stays"].discard,
 			Equals,
@@ -55,7 +56,7 @@ func (s *FunctionalSuite) TestSemanticVersionColumnDiscard(c *C) {
 		testMetricMap["test_namespace"]["metric_which_discards"] = discardableMetric
 
 		// Discard metric should be discarded
-		resultMap := makeDescMap(semver.MustParse("0.0.1"), testMetricMap)
+		resultMap := makeDescMap(semver.MustParse("0.0.1"), prometheus.Labels{}, testMetricMap)
 		c.Check(
 			resultMap["test_namespace"].columnMappings["metric_which_stays"].discard,
 			Equals,
@@ -76,7 +77,7 @@ func (s *FunctionalSuite) TestSemanticVersionColumnDiscard(c *C) {
 		testMetricMap["test_namespace"]["metric_which_discards"] = discardableMetric
 
 		// Discard metric should be discarded
-		resultMap := makeDescMap(semver.MustParse("0.0.2"), testMetricMap)
+		resultMap := makeDescMap(semver.MustParse("0.0.2"), prometheus.Labels{}, testMetricMap)
 		c.Check(
 			resultMap["test_namespace"].columnMappings["metric_which_stays"].discard,
 			Equals,