Add a new contiguous allocator strategy option

Also fix an error in port allocator

pkg/registry/service/allocator/bitmap.go

@@ -55,6 +55,7 @@ var _ Snapshottable = &AllocationBitmap{}
 // allocateStrategy is a search strategy in the allocation map for a valid item.
 type allocateStrategy func(allocated *big.Int, max, count int) (int, bool)
 
+// NewAllocationMap creates an allocation bitmap using the random scan strategy.
 func NewAllocationMap(max int, rangeSpec string) *AllocationBitmap {
 	a := AllocationBitmap{
 		strategy:  randomScanStrategy,
@@ -66,6 +67,30 @@ func NewAllocationMap(max int, rangeSpec string) *AllocationBitmap {
 	return &a
 }
 
+// NewContiguousAllocationMap creates an allocation bitmap using the contiguous scan strategy.
+func NewContiguousAllocationMap(max int, rangeSpec string) *AllocationBitmap {
+	a := AllocationBitmap{
+		strategy:  contiguousScanStrategy,
+		allocated: big.NewInt(0),
+		count:     0,
+		max:       max,
+		rangeSpec: rangeSpec,
+	}
+	return &a
+}
+
+// NewRandomAllocationInterface creates an allocation bitmap satisfying Interface using the
+// random scan strategy.
+func NewRandomAllocationInterface(max int, rangeSpec string) Interface {
+	return NewAllocationMap(max, rangeSpec)
+}
+
+// NewContiguousAllocationInterface creates an allocation bitmap satisfying Interface using the
+// contiguous scan strategy.
+func NewContiguousAllocationInterface(max int, rangeSpec string) Interface {
+	return NewContiguousAllocationMap(max, rangeSpec)
+}
+
 // Allocate attempts to reserve the provided item.
 // Returns true if it was allocated, false if it was already in use
 func (r *AllocationBitmap) Allocate(offset int) (bool, error) {
@@ -166,3 +191,16 @@ func randomScanStrategy(allocated *big.Int, max, count int) (int, bool) {
 	}
 	return 0, false
 }
+
+// contiguousScanStrategy tries to allocate starting at 0 and filling in any gaps
+func contiguousScanStrategy(allocated *big.Int, max, count int) (int, bool) {
+	if count >= max {
+		return 0, false
+	}
+	for i := 0; i < max; i++ {
+		if allocated.Bit(i) == 0 {
+			return i, true
+		}
+	}
+	return 0, false
+}

pkg/registry/service/portallocator/allocator.go

@@ -151,8 +151,7 @@ func (r *PortAllocator) Restore(pr util.PortRange, data []byte) error {
 	if !ok {
 		return fmt.Errorf("not a snapshottable allocator")
 	}
-	snapshottable.Restore(pr.String(), data)
-	return nil
+	return snapshottable.Restore(pr.String(), data)
 }
 
 // contains returns true and the offset if the port is in the range, and false