Eviction manager needs to start as runtime dependent module

pkg/kubelet/eviction/eviction_manager.go

@@ -101,8 +101,9 @@ func (m *managerImpl) Admit(attrs *lifecycle.PodAdmitAttributes) lifecycle.PodAd
 }
 
 // Start starts the control loop to observe and response to low compute resources.
-func (m *managerImpl) Start(podFunc ActivePodsFunc, monitoringInterval time.Duration) {
+func (m *managerImpl) Start(diskInfoProvider DiskInfoProvider, podFunc ActivePodsFunc, monitoringInterval time.Duration) error {
 	go wait.Until(func() { m.synchronize(podFunc) }, monitoringInterval, wait.NeverStop)
+	return nil
 }
 
 // IsUnderMemoryPressure returns true if the node is under memory pressure.

pkg/kubelet/eviction/types.go

@@ -65,12 +65,18 @@ type Threshold struct {
 // Manager evaluates when an eviction threshold for node stability has been met on the node.
 type Manager interface {
 	// Start starts the control loop to monitor eviction thresholds at specified interval.
-	Start(podFunc ActivePodsFunc, monitoringInterval time.Duration)
+	Start(diskInfoProvider DiskInfoProvider, podFunc ActivePodsFunc, monitoringInterval time.Duration) error
 
 	// IsUnderMemoryPressure returns true if the node is under memory pressure.
 	IsUnderMemoryPressure() bool
 }
 
+// DiskInfoProvider is responsible for informing the manager how disk is configured.
+type DiskInfoProvider interface {
+	// HasDedicatedImageFs returns true if the imagefs is on a separate device from the rootfs.
+	HasDedicatedImageFs() (bool, error)
+}
+
 // KillPodFunc kills a pod.
 // The pod status is updated, and then it is killed with the specified grace period.
 // This function must block until either the pod is killed or an error is encountered.

pkg/kubelet/kubelet.go

@@ -926,7 +926,11 @@ func (kl *Kubelet) initializeModules() error {
 // initializeRuntimeDependentModules will initialize internal modules that require the container runtime to be up.
 func (kl *Kubelet) initializeRuntimeDependentModules() {
 	if err := kl.cadvisor.Start(); err != nil {
-		kl.runtimeState.setInternalError(fmt.Errorf("Failed to start cAdvisor %v", err))
+		kl.runtimeState.setInternalError(fmt.Errorf("failed to start cAdvisor %v", err))
+	}
+	// eviction manager must start after cadvisor because it needs to know if the container runtime has a dedicated imagefs
+	if err := kl.evictionManager.Start(kl, kl.getActivePods, evictionMonitoringPeriod); err != nil {
+		kl.runtimeState.setInternalError(fmt.Errorf("failed to start eviction manager %v", err))
 	}
 }
 
@@ -961,7 +965,6 @@ func (kl *Kubelet) Run(updates <-chan kubetypes.PodUpdate) {
 	// Start component sync loops.
 	kl.statusManager.Start()
 	kl.probeManager.Start()
-	kl.evictionManager.Start(kl.getActivePods, evictionMonitoringPeriod)
 
 	// Start the pod lifecycle event generator.
 	kl.pleg.Start()

pkg/kubelet/kubelet_cadvisor.go

@@ -45,6 +45,19 @@ func (kl *Kubelet) GetContainerInfo(podFullName string, podUID types.UID, contai
 	return &ci, nil
 }
 
+// HasDedicatedImageFs returns true if the imagefs has a dedicated device.
+func (kl *Kubelet) HasDedicatedImageFs() (bool, error) {
+	imageFsInfo, err := kl.ImagesFsInfo()
+	if err != nil {
+		return false, err
+	}
+	rootFsInfo, err := kl.RootFsInfo()
+	if err != nil {
+		return false, err
+	}
+	return imageFsInfo.Device != rootFsInfo.Device, nil
+}
+
 // GetContainerInfoV2 returns stats (from Cadvisor) for containers.
 func (kl *Kubelet) GetContainerInfoV2(name string, options cadvisorapiv2.RequestOptions) (map[string]cadvisorapiv2.ContainerInfo, error) {
 	return kl.cadvisor.ContainerInfoV2(name, options)

pkg/kubelet/kubelet_cadvisor_test.go

@@ -21,6 +21,7 @@ import (
 	"testing"
 
 	cadvisorapi "github.com/google/cadvisor/info/v1"
+	cadvisorapiv2 "github.com/google/cadvisor/info/v2"
 	kubecontainer "k8s.io/kubernetes/pkg/kubelet/container"
 	kubecontainertest "k8s.io/kubernetes/pkg/kubelet/container/testing"
 )
@@ -232,3 +233,37 @@ func TestGetContainerInfoWithNoMatchingContainers(t *testing.T) {
 	}
 	mockCadvisor.AssertExpectations(t)
 }
+
+func TestHasDedicatedImageFs(t *testing.T) {
+	testCases := map[string]struct {
+		imageFsInfo cadvisorapiv2.FsInfo
+		rootFsInfo  cadvisorapiv2.FsInfo
+		expected    bool
+	}{
+		"has-dedicated-image-fs": {
+			imageFsInfo: cadvisorapiv2.FsInfo{Device: "123"},
+			rootFsInfo:  cadvisorapiv2.FsInfo{Device: "456"},
+			expected:    true,
+		},
+		"has-unified-image-fs": {
+			imageFsInfo: cadvisorapiv2.FsInfo{Device: "123"},
+			rootFsInfo:  cadvisorapiv2.FsInfo{Device: "123"},
+			expected:    false,
+		},
+	}
+	for testName, testCase := range testCases {
+		testKubelet := newTestKubelet(t, false /* controllerAttachDetachEnabled */)
+		kubelet := testKubelet.kubelet
+		mockCadvisor := testKubelet.fakeCadvisor
+		mockCadvisor.On("Start").Return(nil)
+		mockCadvisor.On("ImagesFsInfo").Return(testCase.imageFsInfo, nil)
+		mockCadvisor.On("RootFsInfo").Return(testCase.rootFsInfo, nil)
+		actual, err := kubelet.HasDedicatedImageFs()
+		if err != nil {
+			t.Errorf("case: %s, unexpected error: %v", testName, err)
+		}
+		if actual != testCase.expected {
+			t.Errorf("case: %s, expected: %v, actual: %v", testName, testCase.expected, actual)
+		}
+	}
+}