Ensure database connections are always closed (#1177)

Signed-off-by: Sam DeHaan <sam.dehaan@grafana.com>
Signed-off-by: Sam DeHaan <dehaansa@gmail.com>
Co-authored-by: Sam DeHaan <sam.dehaan@grafana.com>
Co-authored-by: Sam DeHaan <dehaansa@gmail.com>

cmd/postgres_exporter/server.go

@@ -173,6 +173,7 @@ func (s *Servers) GetServer(dsn string) (*Server, error) {
 			s.servers[dsn] = server
 		}
 		if err = server.Ping(); err != nil {
+			server.Close()
 			delete(s.servers, dsn)
 			time.Sleep(time.Duration(errCount) * time.Second)
 			continue

collector/collector.go

@@ -173,11 +173,11 @@ func (p PostgresCollector) Collect(ch chan<- prometheus.Metric) {
 
 	// Set up the database connection for the collector.
 	err := inst.setup()
+	defer inst.Close()
 	if err != nil {
 		p.logger.Error("Error opening connection to database", "err", err)
 		return
 	}
-	defer inst.Close()
 
 	wg := sync.WaitGroup{}
 	wg.Add(len(p.Collectors))
@@ -190,6 +190,10 @@ func (p PostgresCollector) Collect(ch chan<- prometheus.Metric) {
 	wg.Wait()
 }
 
+func (p *PostgresCollector) Close() error {
+	return p.instance.Close()
+}
+
 func execute(ctx context.Context, name string, c Collector, instance *instance, ch chan<- prometheus.Metric, logger *slog.Logger) {
 	begin := time.Now()
 	err := c.Update(ctx, instance, ch)

collector/probe.go

@@ -76,11 +76,11 @@ func (pc *ProbeCollector) Describe(ch chan<- *prometheus.Desc) {
 func (pc *ProbeCollector) Collect(ch chan<- prometheus.Metric) {
 	// Set up the database connection for the collector.
 	err := pc.instance.setup()
+	defer pc.instance.Close()
 	if err != nil {
 		pc.logger.Error("Error opening connection to database", "err", err)
 		return
 	}
-	defer pc.instance.Close()
 
 	wg := sync.WaitGroup{}
 	wg.Add(len(pc.collectors))