CA: Fix a data race in framework.NewHandle

Multiple tests can call NewHandle() concurrently, because of
t.Parallel(). NewHandle calls schedulermetrics.InitMetrics()
which modifies global variables, so there's a race.

Wrapped the schedulermetrics.InitMetrics() call in a sync.Once.Do()
so that it's only done once, in a thread-safe manner.

cluster-autoscaler/simulator/framework/handle.go

@@ -19,6 +19,7 @@ package framework
 import (
 	"context"
 	"fmt"
+	"sync"
 
 	"k8s.io/client-go/informers"
 	schedulerconfig "k8s.io/kubernetes/pkg/scheduler/apis/config"
@@ -29,6 +30,10 @@ import (
 	schedulermetrics "k8s.io/kubernetes/pkg/scheduler/metrics"
 )
 
+var (
+	initMetricsOnce sync.Once
+)
+
 // Handle is meant for interacting with the scheduler framework.
 type Handle struct {
 	Framework        schedulerframework.Framework
@@ -50,7 +55,9 @@ func NewHandle(informerFactory informers.SharedInformerFactory, schedConfig *sch
 	}
 	sharedLister := NewDelegatingSchedulerSharedLister()
 
-	schedulermetrics.InitMetrics()
+	initMetricsOnce.Do(func() {
+		schedulermetrics.InitMetrics()
+	})
 	framework, err := schedulerframeworkruntime.NewFramework(
 		context.TODO(),
 		schedulerplugins.NewInTreeRegistry(),