allow tuning *IdleConn* for intra-cluster messages (#8799)

* allow tuning *IdleConn* for inter cluster messages

* default MaxIdleConnsPerHost to 128

config/default.json

@@ -323,7 +323,10 @@
         "UseExperimentalGossip": false,
         "ReadOnlyConfig": true,
         "GossipPort": 8074,
-        "StreamingPort": 8075
+        "StreamingPort": 8075,
+        "MaxIdleConns": 100,
+        "MaxIdleConnsPerHost": 128,
+        "IdleConnTimeoutMilliseconds": 90000
     },
     "MetricsSettings": {
         "Enable": false,

model/config.go

@@ -468,6 +468,9 @@ type ClusterSettings struct {
 	ReadOnlyConfig              *bool
 	GossipPort                  *int
 	StreamingPort               *int
+	MaxIdleConns                *int
+	MaxIdleConnsPerHost         *int
+	IdleConnTimeoutMilliseconds *int
 }
 
 func (s *ClusterSettings) SetDefaults() {
@@ -502,6 +505,18 @@ func (s *ClusterSettings) SetDefaults() {
 	if s.StreamingPort == nil {
 		s.StreamingPort = NewInt(8075)
 	}
+
+	if s.MaxIdleConns == nil {
+		s.MaxIdleConns = NewInt(100)
+	}
+
+	if s.MaxIdleConnsPerHost == nil {
+		s.MaxIdleConnsPerHost = NewInt(128)
+	}
+
+	if s.IdleConnTimeoutMilliseconds == nil {
+		s.IdleConnTimeoutMilliseconds = NewInt(90000)
+	}
 }
 
 type MetricsSettings struct {