adding scheduler as a configurable option

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

pkg/driver/controller.go

@@ -77,8 +77,9 @@ func (cs *controller) CreateVolume(
 	kl := req.GetParameters()["keylocation"]
 	pool := req.GetParameters()["poolname"]
 	tp := req.GetParameters()["thinprovision"]
+	schld := req.GetParameters()["scheduler"]
 
-	selected := scheduler(req.AccessibilityRequirements, pool)
+	selected := scheduler(req.AccessibilityRequirements, schld, pool)
 
 	if len(selected) == 0 {
 		return nil, status.Error(codes.Internal, "scheduler failed")

pkg/driver/scheduler.go

@@ -26,6 +26,13 @@ import (
 	zvol "github.com/openebs/zfs-localpv/pkg/zfs"
 )
 
+// scheduling algorithm constants
+const (
+	// pick the node where less volumes are provisioned for the given pool
+	// this will be the default scheduler when none provided
+	VolumeWeighted = "VolumeWeighted"
+)
+
 // volumeWeightedScheduler goes through all the pools on the nodes mentioned
 // in the topology and picks the node which has less volume on
 // the given zfs pool.
@@ -66,14 +73,19 @@ func volumeWeightedScheduler(topo *csi.TopologyRequirement, pool string) string
 
 // scheduler schedules the PV as per topology constraints for
 // the given zfs pool.
-func scheduler(topo *csi.TopologyRequirement, pool string) string {
+func scheduler(topo *csi.TopologyRequirement, schld string, pool string) string {
 
 	// if there is a single node, schedule it on that
 	if len(topo.Preferred) == 1 {
 		return topo.Preferred[0].Segments[zvol.ZFSTopologyKey]
 	}
 
-	selected := volumeWeightedScheduler(topo, pool)
+	switch schld {
+	case VolumeWeighted:
+		return volumeWeightedScheduler(topo, pool)
+	default:
+		return volumeWeightedScheduler(topo, pool)
+	}
 
-	return selected
+	return ""
 }