github.com/makyo/juju@v0.0.0-20160425123129-2608902037e9/state/storage/storage.go (about)

     1  // Copyright 2014 Canonical Ltd.
     2  // Licensed under the AGPLv3, see LICENCE file for details.
     3  
     4  package storage
     5  
     6  import (
     7  	"io"
     8  
     9  	"gopkg.in/juju/blobstore.v2"
    10  	"gopkg.in/mgo.v2"
    11  )
    12  
    13  const (
    14  	// metadataDB is the name of the blobstore metadata database.
    15  	metadataDB = "juju"
    16  
    17  	// blobstoreDB is the name of the blobstore GridFS database.
    18  	blobstoreDB = "blobstore"
    19  )
    20  
    21  // Storage is an interface providing methods for storing and retrieving
    22  // data by path.
    23  type Storage interface {
    24  	// Get returns an io.ReadCloser for data at path, namespaced to the
    25  	// model.
    26  	//
    27  	// If the data is still being uploaded and is not fully written yet, a
    28  	// blobstore.ErrUploadPending error is returned. This means the path is
    29  	// valid but the caller should try again later to retrieve the data.
    30  	Get(path string) (r io.ReadCloser, length int64, err error)
    31  
    32  	// Put stores data from reader at path, namespaced to the model.
    33  	Put(path string, r io.Reader, length int64) error
    34  
    35  	// PutAndCheckHash stores data from reader at path, namespaced to
    36  	// the model. It also ensures the stored data has the correct
    37  	// hash.
    38  	PutAndCheckHash(path string, r io.Reader, length int64, hash string) error
    39  
    40  	// Remove removes data at path, namespaced to the model.
    41  	Remove(path string) error
    42  }
    43  
    44  // Storage returns a Storage for the model with the specified UUID.
    45  func NewStorage(modelUUID string, session *mgo.Session) Storage {
    46  	return stateStorage{modelUUID, session}
    47  }
    48  
    49  type stateStorage struct {
    50  	modelUUID string
    51  	session   *mgo.Session
    52  }
    53  
    54  func (s stateStorage) blobstore() (*mgo.Session, blobstore.ManagedStorage) {
    55  	session := s.session.Copy()
    56  	rs := blobstore.NewGridFS(blobstoreDB, blobstoreDB, session)
    57  	db := session.DB(metadataDB)
    58  	return session, blobstore.NewManagedStorage(db, rs)
    59  }
    60  
    61  func (s stateStorage) Get(path string) (r io.ReadCloser, length int64, err error) {
    62  	session, ms := s.blobstore()
    63  	r, length, err = ms.GetForBucket(s.modelUUID, path)
    64  	if err != nil {
    65  		session.Close()
    66  		return nil, -1, err
    67  	}
    68  	return &stateStorageReadCloser{r, session}, length, nil
    69  }
    70  
    71  func (s stateStorage) Put(path string, r io.Reader, length int64) error {
    72  	session, ms := s.blobstore()
    73  	defer session.Close()
    74  	return ms.PutForBucket(s.modelUUID, path, r, length)
    75  }
    76  
    77  func (s stateStorage) PutAndCheckHash(path string, r io.Reader, length int64, hash string) error {
    78  	session, ms := s.blobstore()
    79  	defer session.Close()
    80  	return ms.PutForBucketAndCheckHash(s.modelUUID, path, r, length, hash)
    81  }
    82  
    83  func (s stateStorage) Remove(path string) error {
    84  	session, ms := s.blobstore()
    85  	defer session.Close()
    86  	return ms.RemoveForBucket(s.modelUUID, path)
    87  }
    88  
    89  type stateStorageReadCloser struct {
    90  	io.ReadCloser
    91  	session *mgo.Session
    92  }
    93  
    94  func (r *stateStorageReadCloser) Close() error {
    95  	r.session.Close()
    96  	return r.ReadCloser.Close()
    97  }