Handle out of disk situation on kubelets.

Kubelet will stop accepting new pods if it detects low disk space on root fs or fs holding docker images.
Running pods are not affected. low-diskspace-threshold-mb is used to configure the low diskspace threshold.

pkg/kubelet/disk_manager.go

@@ -0,0 +1,149 @@
+/*
+Copyright 2015 The Kubernetes Authors All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package kubelet
+
+import (
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/kubelet/cadvisor"
+	"github.com/golang/glog"
+	cadvisorApi "github.com/google/cadvisor/info/v2"
+)
+
+// Manages policy for diskspace management for disks holding docker images and root fs.
+
+// Implementation is thread-safe.
+type diskSpaceManager interface {
+	// Checks the available disk space
+	IsRootDiskSpaceAvailable() (bool, error)
+	IsDockerDiskSpaceAvailable() (bool, error)
+	// Always returns sufficient space till Unfreeze() is called.
+	// This is a signal from caller that its internal initialization is done.
+	Unfreeze()
+}
+
+type DiskSpacePolicy struct {
+	// free disk space threshold for filesystem holding docker images.
+	DockerFreeDiskMB int
+	// free disk space threshold for root filesystem. Host volumes are created on root fs.
+	RootFreeDiskMB int
+}
+
+type fsInfo struct {
+	Usage     int64
+	Capacity  int64
+	Timestamp time.Time
+}
+
+type realDiskSpaceManager struct {
+	cadvisor   cadvisor.Interface
+	cachedInfo map[string]fsInfo // cache of filesystem info.
+	lock       sync.Mutex        // protecting cachedInfo and frozen.
+	policy     DiskSpacePolicy   // thresholds. Set at creation time.
+	frozen     bool              // space checks always return ok when frozen is set. True on creation.
+}
+
+func (dm *realDiskSpaceManager) getFsInfo(fsType string, f func() (cadvisorApi.FsInfo, error)) (fsInfo, error) {
+	dm.lock.Lock()
+	defer dm.lock.Unlock()
+	fsi := fsInfo{}
+	if info, ok := dm.cachedInfo[fsType]; ok {
+		timeLimit := time.Now().Add(-2 * time.Second)
+		if info.Timestamp.After(timeLimit) {
+			fsi = info
+		}
+	}
+	if fsi.Timestamp.IsZero() {
+		fs, err := f()
+		if err != nil {
+			return fsInfo{}, err
+		}
+		fsi.Timestamp = time.Now()
+		fsi.Usage = int64(fs.Usage)
+		fsi.Capacity = int64(fs.Capacity)
+		dm.cachedInfo[fsType] = fsi
+	}
+	return fsi, nil
+}
+
+func (dm *realDiskSpaceManager) IsDockerDiskSpaceAvailable() (bool, error) {
+	return dm.isSpaceAvailable("docker", dm.policy.DockerFreeDiskMB, dm.cadvisor.DockerImagesFsInfo)
+}
+
+func (dm *realDiskSpaceManager) IsRootDiskSpaceAvailable() (bool, error) {
+	return dm.isSpaceAvailable("root", dm.policy.RootFreeDiskMB, dm.cadvisor.RootFsInfo)
+}
+
+func (dm *realDiskSpaceManager) isSpaceAvailable(fsType string, threshold int, f func() (cadvisorApi.FsInfo, error)) (bool, error) {
+	if dm.frozen {
+		return true, nil
+	}
+	fsInfo, err := dm.getFsInfo(fsType, f)
+	if err != nil {
+		return true, fmt.Errorf("failed to get fs info for %q: %v", fsType, err)
+	}
+	if fsInfo.Capacity == 0 {
+		return true, fmt.Errorf("could not determine capacity for %q fs.", fsType)
+	}
+	free := fsInfo.Capacity - fsInfo.Usage
+	if free < 0 {
+		return true, fmt.Errorf("wrong fs usage for %q: capacity %d, usage %d", fsType, fsInfo.Capacity, fsInfo.Usage)
+	}
+
+	const mb = int64(1024 * 1024)
+
+	if free < int64(threshold)*mb {
+		glog.Infof("Running out of space on disk for %q: free %d MB, threshold %d MB", fsType, free/mb, threshold)
+		return false, nil
+	}
+	return true, nil
+}
+
+func (dm *realDiskSpaceManager) Unfreeze() {
+	dm.lock.Lock()
+	defer dm.lock.Unlock()
+	dm.frozen = false
+}
+
+func validatePolicy(policy DiskSpacePolicy) error {
+	if policy.DockerFreeDiskMB < 0 {
+		return fmt.Errorf("free disk space should be non-negative. Invalid value %d for docker disk space threshold.", policy.DockerFreeDiskMB)
+	}
+	if policy.RootFreeDiskMB < 0 {
+		return fmt.Errorf("free disk space should be non-negative. Invalid value %d for root disk space threshold.", policy.RootFreeDiskMB)
+	}
+	return nil
+}
+
+func newDiskSpaceManager(cadvisorInterface cadvisor.Interface, policy DiskSpacePolicy) (diskSpaceManager, error) {
+	// validate policy
+	err := validatePolicy(policy)
+	if err != nil {
+		return nil, err
+	}
+
+	dm := &realDiskSpaceManager{
+		cadvisor:   cadvisorInterface,
+		policy:     policy,
+		cachedInfo: map[string]fsInfo{},
+		frozen:     true,
+	}
+
+	return dm, nil
+}