disable default pool behavior

- disable default pool behavior to avoid unnecessary connection buildup
- improve connection management for source/target options
- TODO: refactor metadata passing for better connection management

core/sling/task.go

@@ -364,10 +364,17 @@ func (t *TaskExecution) setGetMetadata() (metadata iop.Metadata) {
 }
 
 func (t *TaskExecution) isUsingPool() bool {
-	if val := os.Getenv("SLING_POOL"); val != "" && !cast.ToBool(val) {
-		return false
+	if val := os.Getenv("SLING_POOL"); val != "" {
+		return cast.ToBool(val)
 	}
-	return cast.ToBool(os.Getenv("SLING_CLI")) && t.Config.ReplicationMode()
+	// return cast.ToBool(os.Getenv("SLING_CLI")) && t.Config.ReplicationMode()
+
+	// disabling pool by default connections are opened based on
+	// source/target options, causing opening new connections anyways
+	// this builds up the open connections for each stream.
+	// TODO: refactor the way source/target options and metadata are passed
+	// which is a big refactor.
+	return false
 }
 
 func (t *TaskExecution) getTargetObjectValue() string {