[#51] Add current nodes as external statistics

Signed-off-by: Artem Tataurov <a.tataurov@yadro.com>

pool/pool.go

@@ -2482,8 +2482,12 @@ func (p *Pool) Balance(ctx context.Context, prm PrmBalanceGet) (accounting.Decim
 func (p Pool) Statistic() Statistic {
 	stat := Statistic{}
 	for _, inner := range p.innerPools {
+		nodes := make([]string, 0, len(inner.clients))
 		inner.lock.RLock()
 		for _, cl := range inner.clients {
+			if cl.isHealthy() {
+				nodes = append(nodes, cl.address())
+			}
 			node := NodeStatistic{
 				address:       cl.address(),
 				methods:       cl.methodsStatus(),
@@ -2494,6 +2498,9 @@ func (p Pool) Statistic() Statistic {
 			stat.overallErrors += node.overallErrors
 		}
 		inner.lock.RUnlock()
+		if len(stat.currentNodes) == 0 {
+			stat.currentNodes = nodes
+		}
 	}
 
 	return stat

pool/statistic.go

@@ -9,6 +9,7 @@ import (
 type Statistic struct {
 	overallErrors uint64
 	nodes         []NodeStatistic
+	currentNodes  []string
 }
 
 // OverallErrors returns sum of errors on all connections. It doesn't decrease.
@@ -21,6 +22,12 @@ func (s Statistic) Nodes() []NodeStatistic {
 	return s.nodes
 }
 
+// CurrentNodes returns list of nodes of inner pool that has at least one healthy node.
+// These nodes have the same and the highest priority among the other healthy nodes.
+func (s Statistic) CurrentNodes() []string {
+	return s.currentNodes
+}
+
 // ErrUnknownNode indicate that node with current address is not found in list.
 var ErrUnknownNode = errors.New("unknown node")