cluster-autoscaler: Fix node group auto discovery for AWS not to mix up ASGs from different k8s clusters

cluster-autoscaler/cloudprovider/aws/README.md

@@ -159,8 +159,11 @@ spec:
 
 As of version v0.5.1, docker images including the support for `--node-group-auto-discovery` is not yet published to official repository.
 Please checkout the latest source of this project locally and run `REGISTRY=<your docker repo> make release` to build and push an image yourself.
-Then, a manifest like below would run a cluster-autoscaler which auto-discovers ASGs tagged with `k8s.io/cluster-autoscaler/enabled` to be node groups.
-Please notice that there are no `--nodes` flags passed to cluster-autoscaler in this setup.
+Then, a manifest like below would run a cluster-autoscaler which auto-discovers ASGs tagged with `k8s.io/cluster-autoscaler/enabled` and `kubernetes.io/cluster/<YOUR CLUSTER NAME>` to be node groups.
+Note that:
+ 
+* `kubernetes.io/cluster/<YOUR CLUSTER NAME>` is required when `k8s.io/cluster-autoscaler/enabled` is used across many clusters to prevent ASGs from different clusters recognized as the node groups
+* There are no `--nodes` flags passed to cluster-autoscaler because the node groups are automatically discovered by tags
  
 ```yaml
 ---
@@ -198,7 +201,7 @@ spec:
             - --cloud-provider=aws
             - --skip-nodes-with-local-storage=false
             - --expander=least-waste
-            - --node-group-auto-discovery=asg:tag=k8s.io/cluster-autoscaler/enabled
+            - --node-group-auto-discovery=asg:tag=k8s.io/cluster-autoscaler/enabled,kubernetes.io/cluster/<YOUR CLUSTER NAME>
           env:
             - name: AWS_REGION
               value: us-east-1

cluster-autoscaler/cloudprovider/aws/aws_cloud_provider.go

@@ -67,7 +67,11 @@ func buildAutoDiscoveringProvider(awsManager *AwsManager, spec string) (*awsClou
 	if tag == "" {
 		return nil, fmt.Errorf("Invalid ASG tag for auto discovery specified: ASG tag must not be empty")
 	}
-	asgs, err := awsManager.getAutoscalingGroupsByTag(tag)
+	// Use the k8s cluster name tag to only discover asgs of the cluster denoted by clusterName
+	// See https://github.com/kubernetes/kubernetes/blob/9ef85a7/pkg/cloudprovider/providers/aws/tags.go#L30-L34
+	// for more information about the tag
+	tags := strings.Split(tag, ",")
+	asgs, err := awsManager.getAutoscalingGroupsByTags(tags)
 	if err != nil {
 		return nil, fmt.Errorf("Failed to get ASGs: %v", err)
 	}

cluster-autoscaler/cloudprovider/aws/aws_manager.go

@@ -257,27 +257,33 @@ func (m *AwsManager) getAutoscalingGroupsByNames(names []string) ([]*autoscaling
 	return asgs, nil
 }
 
-func (m *AwsManager) getAutoscalingGroupsByTag(key string) ([]*autoscaling.Group, error) {
-	glog.V(6).Infof("Starting getAutoscalingGroupsByTag with key=%v", key)
+func (m *AwsManager) getAutoscalingGroupsByTags(keys []string) ([]*autoscaling.Group, error) {
+	glog.V(6).Infof("Starting getAutoscalingGroupsByTag with keys=%v", keys)
 
-	tags := []*autoscaling.TagDescription{}
+	numKeys := len(keys)
 
+	// DescribeTags does an OR query when multiple filters on different tags are specified.
+	// In other words, DescribeTags returns [asg1, asg1] for keys [t1, t2] when there's only one asg tagged both t1 and t2.
+	filters := []*autoscaling.Filter{}
+	for _, key := range keys {
+		filter := &autoscaling.Filter{
+			Name:   aws.String("key"),
+			Values: []*string{aws.String(key)},
+		}
+		filters = append(filters, filter)
+	}
 	description, err := m.service.DescribeTags(&autoscaling.DescribeTagsInput{
-		Filters: []*autoscaling.Filter{
-			{
-				Name:   aws.String("key"),
-				Values: []*string{aws.String(key)},
-			},
-		},
+		Filters:    filters,
 		MaxRecords: aws.Int64(maxRecordsReturnedByAPI),
 	})
 	if err != nil {
-		glog.V(4).Infof("Failed to describe ASG tags for key %s : %v", key, err)
+		glog.V(4).Infof("Failed to describe ASG tags for keys %v : %v", keys, err)
 		return nil, err
 	}
 	if len(description.Tags) < 1 {
-		return nil, fmt.Errorf("Unable to find ASGs for tag key %s", key)
+		return nil, fmt.Errorf("Unable to find ASGs for tag keys %v", keys)
 	}
+	tags := []*autoscaling.TagDescription{}
 	tags = append(tags, description.Tags...)
 
 	for description.NextToken != nil {
@@ -286,16 +292,30 @@ func (m *AwsManager) getAutoscalingGroupsByTag(key string) ([]*autoscaling.Group
 			MaxRecords: aws.Int64(maxRecordsReturnedByAPI),
 		})
 		if err != nil {
-			glog.V(4).Infof("Failed to describe ASG tags for key %s: %v", key, err)
+			glog.V(4).Infof("Failed to describe ASG tags for key %v: %v", keys, err)
 			return nil, err
 		}
 		tags = append(tags, description.Tags...)
 	}
 
-	asgNames := []string{}
+	// De-duplicate asg names
+	asgNameOccurrences := map[string]int{}
 	for _, t := range tags {
-		asgName := t.ResourceId
-		asgNames = append(asgNames, *asgName)
+		asgName := *(t.ResourceId)
+		if n, ok := asgNameOccurrences[asgName]; ok {
+			asgNameOccurrences[asgName] = n + 1
+		} else {
+			asgNameOccurrences[asgName] = 1
+		}
+	}
+	// Accordingly to how DescribeTags API works, the result contains ASGs which not all but only subset of tags are associated.
+	// Explicitly select ASGs to which all the tags are associated so that we won't end up calling DescribeAutoScalingGroups API
+	// multiple times on an ASG
+	asgNames := []string{}
+	for asgName, n := range asgNameOccurrences {
+		if n == numKeys {
+			asgNames = append(asgNames, asgName)
+		}
 	}
 
 	asgs, err := m.getAutoscalingGroupsByNames(asgNames)

cluster-autoscaler/main.go

@@ -67,7 +67,7 @@ var (
 	cloudConfig             = flag.String("cloud-config", "", "The path to the cloud provider configuration file.  Empty string for no configuration file.")
 	configMapName           = flag.String("configmap", "", "The name of the ConfigMap containing settings used for dynamic reconfiguration. Empty string for no ConfigMap.")
 	namespace               = flag.String("namespace", "kube-system", "Namespace in which cluster-autoscaler run. If a --configmap flag is also provided, ensure that the configmap exists in this namespace before CA runs.")
-	nodeGroupAutoDiscovery  = flag.String("node-group-auto-discovery", "", "One or more definition(s) of node group auto-discovery. A definition is expressed `<name of discoverer per cloud provider>:[<key>[=<value>]]`. Only the `aws` cloud provider is currently supported. The only valid discoverer for it is `asg` and the valid key is `tag`. For example, specifying `--cloud-provider aws` and `--node-group-auto-discovery asg:tag=cluster-autoscaler/auto-discovery/enabled` resuls in ASGs tagged with `cluster-autoscaler/auto-discovery/enabled` to be considered as target node groups")
+	nodeGroupAutoDiscovery  = flag.String("node-group-auto-discovery", "", "One or more definition(s) of node group auto-discovery. A definition is expressed `<name of discoverer per cloud provider>:[<key>[=<value>]]`. Only the `aws` cloud provider is currently supported. The only valid discoverer for it is `asg` and the valid key is `tag`. For example, specifying `--cloud-provider aws` and `--node-group-auto-discovery asg:tag=cluster-autoscaler/auto-discovery/enabled,kubernetes.io/cluster/<YOUR CLUSTER NAME>` results in ASGs tagged with `cluster-autoscaler/auto-discovery/enabled` and `kubernetes.io/cluster/<YOUR CLUSTER NAME>` to be considered as target node groups")
 	verifyUnschedulablePods = flag.Bool("verify-unschedulable-pods", true,
 		"If enabled CA will ensure that each pod marked by Scheduler as unschedulable actually can't be scheduled on any node."+
 			"This prevents from adding unnecessary nodes in situation when CA and Scheduler have different configuration.")