ignore deadtuples if not superuser and ext not installed

gauges/deadtuples.go

@@ -3,6 +3,7 @@ package gauges
 import (
 	"time"
 
+	"github.com/apex/log"
 	"github.com/prometheus/client_golang/prometheus"
 )
 
@@ -18,6 +19,17 @@ func (g *Gauges) DeadTuples() *prometheus.GaugeVec {
 	}
 	var gauge = prometheus.NewGaugeVec(opts, []string{"table"})
 
+	if !g.isSuperuser {
+		g.Errs.Inc()
+		log.Error("postgresql_dead_tuples_pct disabled because pgstattuple requires a superuser")
+		return gauge
+	}
+	if !g.hasExtension("pgstattuple") {
+		g.Errs.Inc()
+		log.Error("postgresql_dead_tuples_pct disabled because pgstattuple extension is not installed")
+		return gauge
+	}
+
 	go func() {
 		for {
 			var tables []Relation

gauges/deadtuples_test.go

@@ -21,3 +21,20 @@ func TestDeadTuples(t *testing.T) {
 	}
 	assertNoErrs(t, gauges)
 }
+
+func TestDeadTuplesWithoutPgstatTuple(t *testing.T) {
+	var assert = assert.New(t)
+	db, gauges, close := prepare(t)
+	defer close()
+	_, err := db.Exec("CREATE TABLE IF NOT EXISTS testtable(id bigint)")
+	assert.NoError(err)
+	_, err = db.Exec("DROP EXTENSION IF EXISTS pgstattuple")
+	assert.NoError(err)
+
+	var metrics = evaluate(t, gauges.DeadTuples())
+	assert.Len(metrics, 1)
+	for _, m := range metrics {
+		assert.Equal(0.0, m.Value)
+	}
+	assertErrs(t, gauges, 1)
+}

gauges/gauge.go

@@ -13,22 +13,25 @@ import (
 )
 
 type Gauges struct {
-	name     string
-	db       *sqlx.DB
-	interval time.Duration
-	labels   prometheus.Labels
-	Errs     prometheus.Gauge
+	name        string
+	db          *sqlx.DB
+	interval    time.Duration
+	labels      prometheus.Labels
+	Errs        prometheus.Gauge
+	isSuperuser bool
 }
 
 func New(name string, db *sql.DB, interval time.Duration) *Gauges {
 	var labels = prometheus.Labels{
 		"database_name": name,
 	}
+	var dbx = sqlx.NewDb(db, "postgres")
 	return &Gauges{
-		name:     name,
-		db:       sqlx.NewDb(db, "postgres"),
-		interval: interval,
-		labels:   labels,
+		name:        name,
+		db:          dbx,
+		interval:    interval,
+		labels:      labels,
+		isSuperuser: isSuperuser(dbx),
 		Errs: prometheus.NewGauge(
 			prometheus.GaugeOpts{
 				Name:        "postgresql_query_errors",
@@ -39,6 +42,25 @@ func New(name string, db *sql.DB, interval time.Duration) *Gauges {
 	}
 }
 
+func isSuperuser(db *sqlx.DB) (super bool) {
+	if err := db.Get(&super, "select usesuper from pg_user where usename = CURRENT_USER"); err != nil {
+		log.WithError(err).Error("failed to detect user privileges")
+	}
+	return
+}
+
+func (g *Gauges) hasExtension(ext string) bool {
+	var count int64
+	if err := g.db.Get(
+		&count,
+		"select count(*) from pg_available_extensions where name = $1",
+		ext,
+	); err != nil {
+		log.WithError(err).Errorf("failed to determine if %s is installed", ext)
+	}
+	return count > 0
+}
+
 func paramsFix(params []string) []interface{} {
 	iparams := make([]interface{}, len(params))
 	for i, v := range params {

gauges/gauge_test.go

@@ -48,6 +48,13 @@ func assertNoErrs(t *testing.T, gauges *Gauges) {
 	assert.Equal(0.0, errs[0].Value)
 }
 
+func assertErrs(t *testing.T, gauges *Gauges, errors int) {
+	var assert = assert.New(t)
+	var errs = evaluate(t, gauges.Errs)
+	assert.Len(errs, 1)
+	assert.Equal(float64(errors), errs[0].Value)
+}
+
 func assertGreaterThan(t *testing.T, expected float64, m Metric) {
 	var assert = assert.New(t)
 	assert.True(