schema/resource isolator: Allow either 'limit' or 'request' to be empty.

NewResourceMemoryIsolator/NewResourceCPUIsolator
If 'limit' is empty, 'request' is set to 'limit', vice versa.
If both are empty, then functions return error.

Author: yifan-gu

schema/types/isolator_resources.go

@@ -144,6 +144,12 @@ func (r ResourceCPU) AsIsolator() Isolator {
 }
 
 func NewResourceCPUIsolator(request, limit string) (*ResourceCPU, error) {
+	if request == "" {
+		request = limit
+	} else if limit == "" {
+		limit = request
+	}
+
 	req, err := resource.ParseQuantity(request)
 	if err != nil {
 		return nil, fmt.Errorf("error parsing request: %v", err)
@@ -198,6 +204,12 @@ func (r ResourceMemory) AsIsolator() Isolator {
 }
 
 func NewResourceMemoryIsolator(request, limit string) (*ResourceMemory, error) {
+	if request == "" {
+		request = limit
+	} else if limit == "" {
+		limit = request
+	}
+
 	req, err := resource.ParseQuantity(request)
 	if err != nil {
 		return nil, fmt.Errorf("error parsing request: %v", err)

schema/types/isolator_resources_test.go

@@ -48,6 +48,44 @@ func TestResourceMemoryIsolator(t *testing.T) {
 			},
 			false,
 		},
+		// only empty request is valid.
+		{
+			"100M",
+			"",
+
+			&ResourceMemory{
+				ResourceBase{
+					resourceValue{
+						Request: mustQuantity("100M"),
+						Limit:   mustQuantity("100M"),
+					},
+				},
+			},
+			false,
+		},
+		// only empty limit is valid.
+		{
+			"",
+			"200M",
+
+			&ResourceMemory{
+				ResourceBase{
+					resourceValue{
+						Request: mustQuantity("200M"),
+						Limit:   mustQuantity("200M"),
+					},
+				},
+			},
+			false,
+		},
+		// both empty limit is invalid.
+		{
+			"",
+			"",
+
+			nil,
+			true,
+		},
 	}
 	for i, tt := range tests {
 		gres, err := NewResourceMemoryIsolator(tt.inreq, tt.inlim)
@@ -68,14 +106,44 @@ func TestResourceCPUIsolator(t *testing.T) {
 		wres *ResourceCPU
 		werr bool
 	}{
-		// empty is not valid
+		// both empty is not valid
 		{
 			"",
-			"2",
+			"",
 
 			nil,
 			true,
 		},
+		// only empty request is valid.
+		{
+			"1",
+			"",
+
+			&ResourceCPU{
+				ResourceBase{
+					resourceValue{
+						Request: mustQuantity("1"),
+						Limit:   mustQuantity("1"),
+					},
+				},
+			},
+			false,
+		},
+		// only empty limit is valid.
+		{
+			"",
+			"2",
+
+			&ResourceCPU{
+				ResourceBase{
+					resourceValue{
+						Request: mustQuantity("2"),
+						Limit:   mustQuantity("2"),
+					},
+				},
+			},
+			false,
+		},
 		// garbage value
 		{
 			"1",

spec/ace.md

@@ -162,6 +162,7 @@ If **request** is omitted, it defaults to the value of **limit**.
 
 - **limit** is the maximum amount of a resource available to the app/pod.
 If the app/pod consumes a resource in excess of its limit, it must be terminated or throttled to no more than the limit.
+If **limit** is ommitted, it defaults to the value of **request**.
 
 Limit and request quantities must always be represented internally (i.e. for encoding and any processing) as an integer value (i.e. NOT floating point) in a resource type's natural base units (e.g., bytes, not megabytes or gigabytes).
 For convenience, when specified by users quantities may either be unsuffixed, have metric suffices (E, P, T, G, M, K) or binary (power-of-two) suffices (Ei, Pi, Ti, Gi, Mi, Ki).