Implement resource constraints on nodes

pkg/apis/config/v1alpha3/types.go

@@ -17,6 +17,7 @@ limitations under the License.
 package v1alpha3
 
 import (
+	"k8s.io/apimachinery/pkg/api/resource"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 
 	"sigs.k8s.io/kind/pkg/container/cri"
@@ -75,6 +76,9 @@ type Node struct {
 	// ExtraPortMappings describes additional port mappings for the node container
 	// binded to a host Port
 	ExtraPortMappings []cri.PortMapping `json:"extraPortMappings,omitempty"`
+
+	// Constraints describes the node resources constraints
+	Constraints NodeResources `json:"constraints,omitempty"`
 }
 
 // NodeRole defines possible role for nodes in a Kubernetes cluster managed by `kind`
@@ -138,3 +142,11 @@ type PatchJSON6902 struct {
 	// Patch should contain the contents of the json patch as a string
 	Patch string `json:"patch"`
 }
+
+// NodeResources represents the node resources (CPU/Memory)
+type NodeResources struct {
+	// The maximum amount of memory the node can use.
+	Memory resource.Quantity `json:"memory,omitempty"`
+	// Specify how much of the available CPU resources a node can use
+	Cpus resource.Quantity `json:"cpus,omitempty"`
+}

pkg/internal/apis/config/types.go

@@ -17,6 +17,7 @@ limitations under the License.
 package config
 
 import (
+	"k8s.io/apimachinery/pkg/api/resource"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 
 	"sigs.k8s.io/kind/pkg/container/cri"
@@ -74,6 +75,9 @@ type Node struct {
 	// ExtraPortMappings describes additional port mappings for the node container
 	// binded to a host Port
 	ExtraPortMappings []cri.PortMapping
+
+	// Constraints describes the node resources constraints
+	Constraints NodeResources
 }
 
 // NodeRole defines possible role for nodes in a Kubernetes cluster managed by `kind`
@@ -137,3 +141,11 @@ type PatchJSON6902 struct {
 	// Patch should contain the contents of the json patch as a string
 	Patch string
 }
+
+// NodeResources represents the node resources (CPU/Memory)
+type NodeResources struct {
+	// The maximum amount of memory the node can use.
+	Memory resource.Quantity
+	// Specify how much of the available CPU resources a node can use.
+	Cpus resource.Quantity
+}

pkg/internal/apis/config/validate.go

@@ -19,6 +19,8 @@ package config
 import (
 	"net"
 
+	"k8s.io/apimachinery/pkg/api/resource"
+
 	"sigs.k8s.io/kind/pkg/errors"
 )
 
@@ -101,6 +103,17 @@ func (n *Node) Validate() error {
 		}
 	}
 
+	// validate node resource constraints
+	if n.Constraints.Cpus.Sign() < 0 {
+		errs = append(errs, errors.New("invalid number of Cpus"))
+	}
+
+	// minimum memory size is 4m
+	minMemory := resource.MustParse("4m")
+	if n.Constraints.Memory.Sign() != 0 && n.Constraints.Memory.Cmp(minMemory) < 0 {
+		errs = append(errs, errors.New("invalid Memory Size (minimum 4m)"))
+	}
+
 	if len(errs) > 0 {
 		return errors.NewAggregate(errs)
 	}

pkg/internal/apis/config/validate_test.go

@@ -19,6 +19,8 @@ package config
 import (
 	"testing"
 
+	"k8s.io/apimachinery/pkg/api/resource"
+
 	"sigs.k8s.io/kind/pkg/errors"
 )
 
@@ -70,6 +72,21 @@ func TestClusterValidate(t *testing.T) {
 			}(),
 			ExpectErrors: 1,
 		},
+		{
+			Name: "wrong resources constraints node",
+			Cluster: func() Cluster {
+				c := Cluster{}
+				SetDefaults_Cluster(&c)
+				n, n2 := Node{}, Node{}
+				SetDefaults_Node(&n)
+				SetDefaults_Node(&n2)
+				n.Constraints.Cpus = resource.MustParse("-12")
+				n.Constraints.Memory = resource.MustParse("1m")
+				c.Nodes = []Node{n, n2}
+				return c
+			}(),
+			ExpectErrors: 1,
+		},
 	}
 
 	for _, tc := range cases {
@@ -151,6 +168,24 @@ func TestNodeValidate(t *testing.T) {
 			}(),
 			ExpectErrors: 1,
 		},
+		{
+			TestName: "Negative CPU constraint",
+			Node: func() Node {
+				cfg := newDefaultedNode(ControlPlaneRole)
+				cfg.Constraints.Cpus = resource.MustParse("-12")
+				return cfg
+			}(),
+			ExpectErrors: 1,
+		},
+		{
+			TestName: "Minimum value for memory constraint",
+			Node: func() Node {
+				cfg := newDefaultedNode(ControlPlaneRole)
+				cfg.Constraints.Memory = resource.MustParse("2m")
+				return cfg
+			}(),
+			ExpectErrors: 1,
+		},
 	}
 
 	for _, tc := range cases {

pkg/internal/cluster/providers/docker/provision.go

@@ -173,9 +173,10 @@ func runArgsForNode(node *config.Node, name string, args []string) []string {
 		args...,
 	)
 
-	// convert mounts and port mappings to container run args
+	// convert mounts, port mappings and resource constraints to container run args
 	args = append(args, generateMountBindings(node.ExtraMounts...)...)
 	args = append(args, generatePortMappings(node.ExtraPortMappings...)...)
+	args = append(args, generateNodeConstraints(node.Constraints)...)
 
 	// finally, specify the image to run
 	return append(args, node.Image)
@@ -293,3 +294,21 @@ func generatePortMappings(portMappings ...cri.PortMapping) []string {
 	}
 	return args
 }
+
+// generateNodeConstraints converts the nodesConstraints to a list of args for docker
+// https://docs.docker.com/config/containers/resource_constraints/
+func generateNodeConstraints(resources config.NodeResources) []string {
+	var args []string
+	if resources.Cpus.Sign() > 0 {
+		args = append(args, fmt.Sprintf("--cpus=%s", resources.Cpus.String()))
+	}
+
+	if resources.Memory.Sign() > 0 {
+		args = append(args, fmt.Sprintf("--memory=%s", resources.Memory.String()))
+		// prevent a container from using swap because we want to effectevely emulate a real node
+		// https://docs.docker.com/config/containers/resource_constraints/#prevent-a-container-from-using-swap
+		args = append(args, fmt.Sprintf("--memory-swap=%s", resources.Memory.String()))
+	}
+
+	return args
+}

site/content/docs/user/quick-start.md

@@ -344,6 +344,26 @@ nodes:
 - role: worker
 ```
 
+#### Limit node resources
+You can set CPU and memory limits for your cluster nodes in the configuration file.
+
+```yaml
+kind: Cluster
+apiVersion: kind.sigs.k8s.io/v1alpha3
+nodes:
+# the control plane node
+- role: control-plane
+  constraints:
+    memory: "200m"
+    cpu: "2"
+- role: worker
+- role: worker
+  constraints:
+    memory: "100m"
+    cpu: "1"
+```
+
+
 ### Configure kind to use a proxy
 If you are running kind in an environment that requires a proxy, you may need to configure kind to use it.