Merge pull request #3443 from adrianreber/rootfs-changes-migration

Include changes to the container's root file-system in the checkpoint archive

3 files changed, 113 insertions, 14 deletions

diff --git a/libpod/container_api.go b/libpod/container_api.go
index ae181887e..6f530f75f 100644
--- a/libpod/container_api.go
+++ b/libpod/container_api.go
@@ -801,15 +801,16 @@ type ContainerCheckpointOptions struct {
 	// TCPEstablished tells the API to checkpoint a container
 	// even if it contains established TCP connections
 	TCPEstablished bool
-	// Export tells the API to write the checkpoint image to
-	// the filename set in TargetFile
-	// Import tells the API to read the checkpoint image from
-	// the filename set in TargetFile
+	// TargetFile tells the API to read (or write) the checkpoint image
+	// from (or to) the filename set in TargetFile
 	TargetFile string
 	// Name tells the API that during restore from an exported
 	// checkpoint archive a new name should be used for the
 	// restored container
 	Name string
+	// IgnoreRootfs tells the API to not export changes to
+	// the container's root file-system (or to not import)
+	IgnoreRootfs bool
 }
 
 // Checkpoint checkpoints a container
diff --git a/libpod/container_internal_linux.go b/libpod/container_internal_linux.go
index aa477611f..399220b9a 100644
--- a/libpod/container_internal_linux.go
+++ b/libpod/container_internal_linux.go
@@ -510,21 +510,44 @@ func (c *Container) addNamespaceContainer(g *generate.Generator, ns LinuxNS, ctr
 	return nil
 }
 
-func (c *Container) exportCheckpoint(dest string) (err error) {
+func (c *Container) exportCheckpoint(dest string, ignoreRootfs bool) (err error) {
 	if (len(c.config.NamedVolumes) > 0) || (len(c.Dependencies()) > 0) {
 		return errors.Errorf("Cannot export checkpoints of containers with named volumes or dependencies")
 	}
 	logrus.Debugf("Exporting checkpoint image of container %q to %q", c.ID(), dest)
+
+	includeFiles := []string{
+		"checkpoint",
+		"artifacts",
+		"ctr.log",
+		"config.dump",
+		"spec.dump",
+		"network.status"}
+
+	// Get root file-system changes included in the checkpoint archive
+	rootfsDiffPath := filepath.Join(c.bundlePath(), "rootfs-diff.tar")
+	if !ignoreRootfs {
+		rootfsDiffFile, err := os.Create(rootfsDiffPath)
+		if err != nil {
+			return errors.Wrapf(err, "error creating root file-system diff file %q", rootfsDiffPath)
+		}
+		tarStream, err := c.runtime.GetDiffTarStream("", c.ID())
+		if err != nil {
+			return errors.Wrapf(err, "error exporting root file-system diff to %q", rootfsDiffPath)
+		}
+		_, err = io.Copy(rootfsDiffFile, tarStream)
+		if err != nil {
+			return errors.Wrapf(err, "error exporting root file-system diff to %q", rootfsDiffPath)
+		}
+		tarStream.Close()
+		rootfsDiffFile.Close()
+		includeFiles = append(includeFiles, "rootfs-diff.tar")
+	}
+
 	input, err := archive.TarWithOptions(c.bundlePath(), &archive.TarOptions{
 		Compression:      archive.Gzip,
 		IncludeSourceDir: true,
-		IncludeFiles: []string{
-			"checkpoint",
-			"artifacts",
-			"ctr.log",
-			"config.dump",
-			"spec.dump",
-			"network.status"},
+		IncludeFiles:     includeFiles,
 	})
 
 	if err != nil {
@@ -546,6 +569,8 @@ func (c *Container) exportCheckpoint(dest string) (err error) {
 		return err
 	}
 
+	os.Remove(rootfsDiffPath)
+
 	return nil
 }
 
@@ -605,7 +630,7 @@ func (c *Container) checkpoint(ctx context.Context, options ContainerCheckpointO
 	}
 
 	if options.TargetFile != "" {
-		if err = c.exportCheckpoint(options.TargetFile); err != nil {
+		if err = c.exportCheckpoint(options.TargetFile, options.IgnoreRootfs); err != nil {
 			return err
 		}
 	}
@@ -792,6 +817,23 @@ func (c *Container) restore(ctx context.Context, options ContainerCheckpointOpti
 	if err := c.saveSpec(g.Spec()); err != nil {
 		return err
 	}
+
+	// Before actually restarting the container, apply the root file-system changes
+	if !options.IgnoreRootfs {
+		rootfsDiffPath := filepath.Join(c.bundlePath(), "rootfs-diff.tar")
+		if _, err := os.Stat(rootfsDiffPath); err == nil {
+			// Only do this if a rootfs-diff.tar actually exists
+			rootfsDiffFile, err := os.Open(rootfsDiffPath)
+			if err != nil {
+				return errors.Wrapf(err, "Failed to open root file-system diff file %s", rootfsDiffPath)
+			}
+			if err := c.runtime.ApplyDiffTarStream(c.ID(), rootfsDiffFile); err != nil {
+				return errors.Wrapf(err, "Failed to apply root file-system diff file %s", rootfsDiffPath)
+			}
+			rootfsDiffFile.Close()
+		}
+	}
+
 	if err := c.ociRuntime.createContainer(c, c.config.CgroupParent, &options); err != nil {
 		return err
 	}
@@ -809,7 +851,7 @@ func (c *Container) restore(ctx context.Context, options ContainerCheckpointOpti
 		if err != nil {
 			logrus.Debugf("Non-fatal: removal of checkpoint directory (%s) failed: %v", c.CheckpointPath(), err)
 		}
-		cleanup := [...]string{"restore.log", "dump.log", "stats-dump", "stats-restore", "network.status"}
+		cleanup := [...]string{"restore.log", "dump.log", "stats-dump", "stats-restore", "network.status", "rootfs-diff.tar"}
 		for _, del := range cleanup {
 			file := filepath.Join(c.bundlePath(), del)
 			err = os.Remove(file)
diff --git a/libpod/diff.go b/libpod/diff.go
index f348e6b81..925bda927 100644
--- a/libpod/diff.go
+++ b/libpod/diff.go
@@ -1,6 +1,9 @@
 package libpod
 
 import (
+	"archive/tar"
+	"io"
+
 	"github.com/containers/libpod/libpod/layers"
 	"github.com/containers/storage/pkg/archive"
 	"github.com/pkg/errors"
@@ -44,6 +47,59 @@ func (r *Runtime) GetDiff(from, to string) ([]archive.Change, error) {
 	return rchanges, err
 }
 
+// skipFileInTarAchive is an archive.TarModifierFunc function
+// which tells archive.ReplaceFileTarWrapper to skip files
+// from the tarstream
+func skipFileInTarAchive(path string, header *tar.Header, content io.Reader) (*tar.Header, []byte, error) {
+	return nil, nil, nil
+}
+
+// GetDiffTarStream returns the differences between the two images, layers, or containers.
+// It is the same functionality as GetDiff() except that it returns a tarstream
+func (r *Runtime) GetDiffTarStream(from, to string) (io.ReadCloser, error) {
+	toLayer, err := r.getLayerID(to)
+	if err != nil {
+		return nil, err
+	}
+	fromLayer := ""
+	if from != "" {
+		fromLayer, err = r.getLayerID(from)
+		if err != nil {
+			return nil, err
+		}
+	}
+	rc, err := r.store.Diff(fromLayer, toLayer, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	// Skip files in the tar archive which are listed
+	// in containerMounts map. Just as in the GetDiff()
+	// function from above
+	filterMap := make(map[string]archive.TarModifierFunc)
+	for key := range containerMounts {
+		filterMap[key[1:]] = skipFileInTarAchive
+		// In the tarstream directories always include a trailing '/'.
+		// For simplicity this duplicates every entry from
+		// containerMounts with a trailing '/', as containerMounts
+		// does not use trailing '/' for directories.
+		filterMap[key[1:]+"/"] = skipFileInTarAchive
+	}
+
+	filteredTarStream := archive.ReplaceFileTarWrapper(rc, filterMap)
+	return filteredTarStream, nil
+}
+
+// ApplyDiffTarStream applies the changes stored in 'diff' to the layer 'to'
+func (r *Runtime) ApplyDiffTarStream(to string, diff io.Reader) error {
+	toLayer, err := r.getLayerID(to)
+	if err != nil {
+		return err
+	}
+	_, err = r.store.ApplyDiff(toLayer, diff)
+	return err
+}
+
 // GetLayerID gets a full layer id given a full or partial id
 // If the id matches a container or image, the id of the top layer is returned
 // If the id matches a layer, the top layer id is returned