Cherry-pick elastic#12914 to 7.2: Release connections in metricbeat r…

…edis module (elastic#12948)

Release pooled connections in metricbeat redis module when they are not
needed anymore so they can be reused.

(cherry picked from commit b65f05b)

CHANGELOG.next.asciidoc

@@ -40,6 +40,8 @@ https://github.com/elastic/beats/compare/v7.2.0...7.2[Check the HEAD diff]
 
 *Metricbeat*
 
+- Fix connections leak in redis module {pull}12914[12914]
+
 *Packetbeat*
 
 *Winlogbeat*

metricbeat/module/redis/info/info.go

@@ -50,8 +50,11 @@ func New(base mb.BaseMetricSet) (mb.MetricSet, error) {
 
 // Fetch fetches metrics from Redis by issuing the INFO command.
 func (m *MetricSet) Fetch(r mb.ReporterV2) error {
+	conn := m.Connection()
+	defer conn.Close()
+
 	// Fetch default INFO.
-	info, err := redis.FetchRedisInfo("default", m.Connection())
+	info, err := redis.FetchRedisInfo("default", conn)
 	if err != nil {
 		return errors.Wrap(err, "failed to fetch redis info")
 	}

metricbeat/module/redis/key/key.go

@@ -70,6 +70,8 @@ func New(base mb.BaseMetricSet) (mb.MetricSet, error) {
 // Fetch fetches information from Redis keys
 func (m *MetricSet) Fetch(r mb.ReporterV2) error {
 	conn := m.Connection()
+	defer conn.Close()
+
 	for _, p := range m.patterns {
 		if err := redis.Select(conn, p.Keyspace); err != nil {
 			msg := errors.Wrapf(err, "Failed to select keyspace %d", p.Keyspace)

metricbeat/module/redis/keyspace/keyspace.go

@@ -48,8 +48,11 @@ func New(base mb.BaseMetricSet) (mb.MetricSet, error) {
 
 // Fetch fetches metrics from Redis by issuing the INFO command.
 func (m *MetricSet) Fetch(r mb.ReporterV2) error {
+	conn := m.Connection()
+	defer conn.Close()
+
 	// Fetch default INFO.
-	info, err := redis.FetchRedisInfo("keyspace", m.Connection())
+	info, err := redis.FetchRedisInfo("keyspace", conn)
 	if err != nil {
 		return errors.Wrap(err, "Failed to fetch redis info for keyspaces")
 	}