chore(refactor): refactor scheduler for ZFS-LocalPV

Signed-off-by: Pawan <pawan@mayadata.io>

pkg/scheduler/scheduler.go

@@ -0,0 +1,99 @@
+/*
+Copyright © 2019 The OpenEBS Authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package scheduler
+
+import (
+	"math"
+
+	"github.com/container-storage-interface/spec/lib/go/csi"
+	k8sapi "github.com/openebs/zfs-localpv/pkg/client/k8s/v1alpha1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/klog"
+)
+
+// getNodeList gets the nodelist which satisfies the topology info
+func getNodeList(topo *csi.TopologyRequirement) ([]string, error) {
+
+	var nodelist []string
+
+	list, err := k8sapi.ListNodes(metav1.ListOptions{})
+	if err != nil {
+		return nil, err
+	}
+
+	for _, node := range list.Items {
+		for _, prf := range topo.Preferred {
+			nodeFiltered := false
+			for key, value := range prf.Segments {
+				if node.Labels[key] != value {
+					nodeFiltered = true
+					break
+				}
+			}
+			if nodeFiltered == false {
+				nodelist = append(nodelist, node.Name)
+				break
+			}
+		}
+	}
+
+	return nodelist, nil
+}
+
+// runScheduler goes through the node mapping
+// in the topology and picks the node which is less weighted
+func runScheduler(nodelist []string, nmap map[string]int64) string {
+	var selected string
+
+	var weight int64 = math.MaxInt64
+
+	// schedule it on the node which has less weight
+	for _, node := range nodelist {
+		if nmap[node] < weight {
+			selected = node
+			weight = nmap[node]
+		}
+	}
+	return selected
+}
+
+// Scheduler schedules the PV as per topology constraints for
+// the given node weight.
+func Scheduler(req *csi.CreateVolumeRequest, nmap map[string]int64) string {
+	topo := req.AccessibilityRequirements
+	if topo == nil ||
+		len(topo.Preferred) == 0 {
+		klog.Errorf("scheduler: topology information not provided")
+		return ""
+	}
+
+	nodelist, err := getNodeList(topo)
+	if err != nil {
+		klog.Errorf("scheduler: can not get the nodelist err : %v", err.Error())
+		return ""
+	} else if len(nodelist) == 0 {
+		klog.Errorf("scheduler: nodelist is empty")
+		return ""
+	}
+
+	// if there is a single node, schedule it on that
+	if len(nodelist) == 1 {
+		return nodelist[0]
+	}
+
+	return runScheduler(nodelist, nmap)
+}