enrich comments

# Conflicts:
#	docs/victoriametrics/changelog/CHANGELOG.md

docs/victoriametrics/changelog/CHANGELOG.md

@@ -42,6 +42,7 @@ See also [LTS releases](https://docs.victoriametrics.com/victoriametrics/lts-rel
 * BUGFIX: [vmagent](https://docs.victoriametrics.com/victoriametrics/vmagent/): apply `-promscrape.maxScrapeSize` check to decompressed data instead of compressed data. See [#9481](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/9481).
 * BUGFIX: [vmalert](https://docs.victoriametrics.com/victoriametrics/vmalert/): disallow setting the `-notifier.url` command-line flag to a null value. See [#10355](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/10355).
 * BUGFIX: [MetricsQL](https://docs.victoriametrics.com/victoriametrics/metricsql/): fix `changes()` function when gaps between samples exceed the lookbehind window. Previously, it could yield a non-zero value even when the sample value remained unchanged. See [#10280](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/10280).
+* BUGFIX: `vmselect` in [VictoriaMetrics cluster](https://docs.victoriametrics.com/victoriametrics/cluster-victoriametrics/): Limit the minimum number of idle connections from 3 to 1. It helps prevent broken connections from remaining for too long and causing failed requests and partial responses during `vmstorage` rolling restart period. See [#10314](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/10314)
 
 ## [v1.134.0](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v1.134.0)
 

lib/netutil/conn_pool.go

@@ -236,13 +236,13 @@ func (cp *ConnPool) closeIdleConns() {
 	// Close connections, which were idle for more than 120 seconds.
 	// This should reduce the number of connections after sudden spikes in query rate.
 	// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2508
-	deadline := fasttime.UnixTimestamp() - 120
+	deadline := fasttime.UnixTimestamp() - 60
 	var activeConns []connWithTimestamp
 	var closeConns []connWithTimestamp
 	cp.mu.Lock()
 
-	// fast path, if there are less than 3 connections in the pool.
-	if len(cp.conns) < 3 {
+	// fast path, if there are less than 2 connections in the pool.
+	if len(cp.conns) < 2 {
 		cp.mu.Unlock()
 		return
 	}
@@ -256,7 +256,10 @@ func (cp *ConnPool) closeIdleConns() {
 		}
 	}
 	for _, c := range closeConns {
-		if len(activeConns) < 3 {
+		// It can limit the number of broken connections remaining after the idle timeout to 1,
+		// preventing failed requests and partial responses caused by too many broken connections after the idle timeout.
+		// Please see https://github.com/VictoriaMetrics/VictoriaMetrics/issues/10314.
+		if len(activeConns) < 1 {
 			activeConns = append(activeConns, c)
 			continue
 		}