Merge pull request #44404 from bsalamat/config_fix

Automatic merge from submit-queue

Scheduler configurator looks for a specific key in ConfigMap.Data

**What this PR does / why we need it**: Changes scheduler configurator to look for a specific key in ConfigMap.Data instead of the old logic which expected only one entry to exist in the map. The key is a constant whose value is "policy.cfg".

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

**Special notes for your reviewer**:

**Release note**:

```release-note
```

plugin/cmd/kube-scheduler/app/configurator.go

@@ -139,17 +139,13 @@ func (sc schedulerConfigurator) getSchedulerPolicyConfig() (*schedulerapi.Policy
 			return nil, fmt.Errorf("Error getting scheduler policy ConfigMap: %v.", err)
 		}
 		if policyConfigMap != nil {
-			// We expect the first element in the Data member of the ConfigMap to
-			// contain the policy config.
-			if len(policyConfigMap.Data) != 1 {
-				return nil, fmt.Errorf("ConfigMap %v has %v entries in its 'Data'. It must have only one.", sc.policyConfigMap, len(policyConfigMap.Data))
-			}
-			policyConfigMapFound = true
-			// This loop should iterate only once, as we have already checked the length of Data.
-			for _, val := range policyConfigMap.Data {
-				glog.V(5).Infof("Scheduler policy ConfigMap: %v", val)
-				configData = []byte(val)
+			var configString string
+			configString, policyConfigMapFound = policyConfigMap.Data[options.SchedulerPolicyConfigMapKey]
+			if !policyConfigMapFound {
+				return nil, fmt.Errorf("No element with key = '%v' is found in the ConfigMap 'Data'.", options.SchedulerPolicyConfigMapKey)
 			}
+			glog.V(5).Infof("Scheduler policy ConfigMap: %v", configString)
+			configData = []byte(configString)
 		}
 	}
 

plugin/cmd/kube-scheduler/app/options/options.go

@@ -18,6 +18,8 @@ limitations under the License.
 package options
 
 import (
+	"fmt"
+
 	utilfeature "k8s.io/apiserver/pkg/util/feature"
 	"k8s.io/kubernetes/pkg/api"
 	"k8s.io/kubernetes/pkg/apis/componentconfig"
@@ -33,6 +35,10 @@ import (
 	"github.com/spf13/pflag"
 )
 
+// SchedulerPolicyConfigMapKey defines the key of the element in the
+// scheduler's policy ConfigMap that contains scheduler's policy config.
+const SchedulerPolicyConfigMapKey string = "policy.cfg"
+
 // SchedulerServer has all the context and params needed to run a Scheduler
 type SchedulerServer struct {
 	componentconfig.KubeSchedulerConfiguration
@@ -64,7 +70,8 @@ func (s *SchedulerServer) AddFlags(fs *pflag.FlagSet) {
 	fs.StringVar(&s.Address, "address", s.Address, "The IP address to serve on (set to 0.0.0.0 for all interfaces)")
 	fs.StringVar(&s.AlgorithmProvider, "algorithm-provider", s.AlgorithmProvider, "The scheduling algorithm provider to use, one of: "+factory.ListAlgorithmProviders())
 	fs.StringVar(&s.PolicyConfigFile, "policy-config-file", s.PolicyConfigFile, "File with scheduler policy configuration. This file is used if policy ConfigMap is not provided or --use-legacy-policy-config==true")
-	fs.StringVar(&s.PolicyConfigMapName, "policy-configmap", s.PolicyConfigMapName, "Name of the ConfigMap object that contains scheduler's policy configuration. It must exist in the system namespace before scheduler initialization if --use-legacy-policy-config==false")
+	usage := fmt.Sprintf("Name of the ConfigMap object that contains scheduler's policy configuration. It must exist in the system namespace before scheduler initialization if --use-legacy-policy-config==false. The config must be provided as the value of an element in 'Data' map with the key='%v'", SchedulerPolicyConfigMapKey)
+	fs.StringVar(&s.PolicyConfigMapName, "policy-configmap", s.PolicyConfigMapName, usage)
 	fs.StringVar(&s.PolicyConfigMapNamespace, "policy-configmap-namespace", s.PolicyConfigMapNamespace, "The namespace where policy ConfigMap is located. The system namespace will be used if this is not provided or is empty.")
 	fs.BoolVar(&s.UseLegacyPolicyConfig, "use-legacy-policy-config", false, "When set to true, scheduler will ignore policy ConfigMap and uses policy config file")
 	fs.BoolVar(&s.EnableProfiling, "profiling", true, "Enable profiling via web interface host:port/debug/pprof/")

test/integration/scheduler/scheduler_test.go

@@ -99,7 +99,7 @@ func TestSchedulerCreationFromConfigMap(t *testing.T) {
 	policyConfigMap := v1.ConfigMap{
 		ObjectMeta: metav1.ObjectMeta{Namespace: metav1.NamespaceSystem, Name: configPolicyName},
 		Data: map[string]string{
-			"scheduler-policy-config.json": `{
+			options.SchedulerPolicyConfigMapKey: `{
 			"kind" : "Policy",
 			"apiVersion" : "v1",
 			"predicates" : [