Merge pull request #61210 from hzxuzhonghu/etcd-random-check

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

check etcd servers by a random order

**What this PR does / why we need it**:

Every time a health check is called on the APIServer via the /healthz endpoint, an etcd healthcheck is performed. Here makes servers check with a random order.

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes #61180

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```

staging/src/k8s.io/apiserver/pkg/storage/etcd3/preflight/checks.go

@@ -18,6 +18,7 @@ package preflight
 
 import (
 	"fmt"
+	"math/rand"
 	"net"
 	"net/url"
 	"time"
@@ -25,12 +26,6 @@ import (
 
 const connectionTimeout = 1 * time.Second
 
-type connection interface {
-	serverReachable(address string) bool
-	parseServerList(serverList []string) error
-	CheckEtcdServers() (bool, error)
-}
-
 // EtcdConnection holds the Etcd server list
 type EtcdConnection struct {
 	ServerList []string
@@ -59,9 +54,11 @@ func parseServerURI(serverURI string) (*url.URL, error) {
 // CheckEtcdServers will attempt to reach all etcd servers once. If any
 // can be reached, return true.
 func (con EtcdConnection) CheckEtcdServers() (done bool, err error) {
-	// Attempt to reach every Etcd server in order
-	for _, serverURI := range con.ServerList {
-		host, err := parseServerURI(serverURI)
+	// Attempt to reach every Etcd server randomly.
+	serverNumber := len(con.ServerList)
+	serverPerms := rand.Perm(serverNumber)
+	for _, index := range serverPerms {
+		host, err := parseServerURI(con.ServerList[index])
 		if err != nil {
 			return false, err
 		}