Add test cases for unknown metric parsing.

Author: wrouesnel

postgres_exporter.go

@@ -125,6 +125,7 @@ type MetricMap struct {
 
 // TODO: revisit cu with the semver system
 func dumpMaps() {
+	// TODO: make this function part of the exporter
 	for name, cmap := range builtinMetricMaps {
 		query, ok := queryOverrides[name]
 		if !ok {
@@ -659,6 +660,10 @@ func dbToString(t interface{}) (string, bool) {
 
 // Exporter collects Postgres metrics. It implements prometheus.Collector.
 type Exporter struct {
+	// Holds a reference to the build in column mappings. Currently this is for testing purposes
+	// only, since it just points to the global.
+	builtinMetricMaps map[string]map[string]ColumnMapping
+
 	dsn              string
 	userQueriesPath  string
 	duration         prometheus.Gauge
@@ -685,8 +690,9 @@ type Exporter struct {
 // NewExporter returns a new PostgreSQL exporter for the provided DSN.
 func NewExporter(dsn string, userQueriesPath string) *Exporter {
 	return &Exporter{
-		dsn:             dsn,
-		userQueriesPath: userQueriesPath,
+		builtinMetricMaps: builtinMetricMaps,
+		dsn:               dsn,
+		userQueriesPath:   userQueriesPath,
 		duration: prometheus.NewGauge(prometheus.GaugeOpts{
 			Namespace: namespace,
 			Subsystem: exporter,
@@ -913,7 +919,7 @@ func (e *Exporter) checkMapVersions(ch chan<- prometheus.Metric, db *sql.DB) err
 		log.Infoln("Semantic Version Changed:", e.lastMapVersion.String(), "->", semanticVersion.String())
 		e.mappingMtx.Lock()
 
-		e.metricMap = makeDescMap(semanticVersion, builtinMetricMaps)
+		e.metricMap = makeDescMap(semanticVersion, e.builtinMetricMaps)
 		e.queryOverrides = makeQueryOverrideMap(semanticVersion, queryOverrides)
 		e.lastMapVersion = semanticVersion
 

postgres_exporter_integration_test.go

@@ -95,3 +95,30 @@ func (s *IntegrationSuite) TestInvalidDsnDoesntCrash(c *C) {
 	c.Assert(exporter, NotNil)
 	exporter.scrape(ch)
 }
+
+// TestUnknownMetricParsingDoesntCrash deliberately deletes all the column maps out
+// of an exporter to test that the default metric handling code can cope with unknown columns.
+func (s *IntegrationSuite) TestUnknownMetricParsingDoesntCrash(c *C) {
+	// Setup a dummy channel to consume metrics
+	ch := make(chan prometheus.Metric, 100)
+	go func() {
+		for range ch {
+		}
+	}()
+
+	dsn := os.Getenv("DATA_SOURCE_NAME")
+	c.Assert(dsn, Not(Equals), "")
+
+	exporter := NewExporter(dsn, "")
+	c.Assert(exporter, NotNil)
+
+	// Convert the default maps into a list of empty maps.
+	emptyMaps := make(map[string]map[string]ColumnMapping, 0)
+	for k := range exporter.builtinMetricMaps {
+		emptyMaps[k] = map[string]ColumnMapping{}
+	}
+	exporter.builtinMetricMaps = emptyMaps
+
+	// scrape the exporter and make sure it works
+	exporter.scrape(ch)
+}