github.com/gunjan5/docker@v1.8.2/daemon/graphdriver/fsdiff.go (about)

     1  // +build daemon
     2  
     3  package graphdriver
     4  
     5  import (
     6  	"time"
     7  
     8  	"github.com/Sirupsen/logrus"
     9  	"github.com/docker/docker/pkg/archive"
    10  	"github.com/docker/docker/pkg/chrootarchive"
    11  	"github.com/docker/docker/pkg/ioutils"
    12  )
    13  
    14  // naiveDiffDriver takes a ProtoDriver and adds the
    15  // capability of the Diffing methods which it may or may not
    16  // support on its own. See the comment on the exported
    17  // NaiveDiffDriver function below.
    18  // Notably, the AUFS driver doesn't need to be wrapped like this.
    19  type naiveDiffDriver struct {
    20  	ProtoDriver
    21  }
    22  
    23  // NaiveDiffDriver returns a fully functional driver that wraps the
    24  // given ProtoDriver and adds the capability of the following methods which
    25  // it may or may not support on its own:
    26  //     Diff(id, parent string) (archive.Archive, error)
    27  //     Changes(id, parent string) ([]archive.Change, error)
    28  //     ApplyDiff(id, parent string, diff archive.ArchiveReader) (size int64, err error)
    29  //     DiffSize(id, parent string) (size int64, err error)
    30  func NaiveDiffDriver(driver ProtoDriver) Driver {
    31  	return &naiveDiffDriver{ProtoDriver: driver}
    32  }
    33  
    34  // Diff produces an archive of the changes between the specified
    35  // layer and its parent layer which may be "".
    36  func (gdw *naiveDiffDriver) Diff(id, parent string) (arch archive.Archive, err error) {
    37  	driver := gdw.ProtoDriver
    38  
    39  	layerFs, err := driver.Get(id, "")
    40  	if err != nil {
    41  		return nil, err
    42  	}
    43  
    44  	defer func() {
    45  		if err != nil {
    46  			driver.Put(id)
    47  		}
    48  	}()
    49  
    50  	if parent == "" {
    51  		archive, err := archive.Tar(layerFs, archive.Uncompressed)
    52  		if err != nil {
    53  			return nil, err
    54  		}
    55  		return ioutils.NewReadCloserWrapper(archive, func() error {
    56  			err := archive.Close()
    57  			driver.Put(id)
    58  			return err
    59  		}), nil
    60  	}
    61  
    62  	parentFs, err := driver.Get(parent, "")
    63  	if err != nil {
    64  		return nil, err
    65  	}
    66  	defer driver.Put(parent)
    67  
    68  	changes, err := archive.ChangesDirs(layerFs, parentFs)
    69  	if err != nil {
    70  		return nil, err
    71  	}
    72  
    73  	archive, err := archive.ExportChanges(layerFs, changes)
    74  	if err != nil {
    75  		return nil, err
    76  	}
    77  
    78  	return ioutils.NewReadCloserWrapper(archive, func() error {
    79  		err := archive.Close()
    80  		driver.Put(id)
    81  		return err
    82  	}), nil
    83  }
    84  
    85  // Changes produces a list of changes between the specified layer
    86  // and its parent layer. If parent is "", then all changes will be ADD changes.
    87  func (gdw *naiveDiffDriver) Changes(id, parent string) ([]archive.Change, error) {
    88  	driver := gdw.ProtoDriver
    89  
    90  	layerFs, err := driver.Get(id, "")
    91  	if err != nil {
    92  		return nil, err
    93  	}
    94  	defer driver.Put(id)
    95  
    96  	parentFs := ""
    97  
    98  	if parent != "" {
    99  		parentFs, err = driver.Get(parent, "")
   100  		if err != nil {
   101  			return nil, err
   102  		}
   103  		defer driver.Put(parent)
   104  	}
   105  
   106  	return archive.ChangesDirs(layerFs, parentFs)
   107  }
   108  
   109  // ApplyDiff extracts the changeset from the given diff into the
   110  // layer with the specified id and parent, returning the size of the
   111  // new layer in bytes.
   112  func (gdw *naiveDiffDriver) ApplyDiff(id, parent string, diff archive.ArchiveReader) (size int64, err error) {
   113  	driver := gdw.ProtoDriver
   114  
   115  	// Mount the root filesystem so we can apply the diff/layer.
   116  	layerFs, err := driver.Get(id, "")
   117  	if err != nil {
   118  		return
   119  	}
   120  	defer driver.Put(id)
   121  
   122  	start := time.Now().UTC()
   123  	logrus.Debugf("Start untar layer")
   124  	if size, err = chrootarchive.ApplyUncompressedLayer(layerFs, diff); err != nil {
   125  		return
   126  	}
   127  	logrus.Debugf("Untar time: %vs", time.Now().UTC().Sub(start).Seconds())
   128  
   129  	return
   130  }
   131  
   132  // DiffSize calculates the changes between the specified layer
   133  // and its parent and returns the size in bytes of the changes
   134  // relative to its base filesystem directory.
   135  func (gdw *naiveDiffDriver) DiffSize(id, parent string) (size int64, err error) {
   136  	driver := gdw.ProtoDriver
   137  
   138  	changes, err := gdw.Changes(id, parent)
   139  	if err != nil {
   140  		return
   141  	}
   142  
   143  	layerFs, err := driver.Get(id, "")
   144  	if err != nil {
   145  		return
   146  	}
   147  	defer driver.Put(id)
   148  
   149  	return archive.ChangesSize(layerFs, changes), nil
   150  }