/
mongodb.go
89 lines (78 loc) · 2.15 KB
/
mongodb.go
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// Copyright 2017 Canonical Ltd.
// Licensed under the AGPLv3, see LICENCE file for details.
package blobstore // import "gopkg.in/juju/charmstore.v5/internal/blobstore"
import (
"fmt"
"io"
"gopkg.in/errgo.v1"
"gopkg.in/mgo.v2"
)
type mongoBackend struct {
fs *mgo.GridFS
}
// NewMongoBackend returns a backend implementation which stores
// data in the given MongoDB database, using prefix as a prefix for
// the collections created.
func NewMongoBackend(db *mgo.Database, prefix string) Backend {
return &mongoBackend{
fs: db.GridFS(prefix),
}
}
func (m *mongoBackend) Get(name string) (ReadSeekCloser, int64, error) {
f, err := m.fs.Open(name)
if err != nil {
if err == mgo.ErrNotFound {
return nil, 0, errgo.WithCausef(err, ErrNotFound, "backend blob not found")
}
return nil, 0, errgo.Mask(err)
}
return mongoBackendReader{f}, f.Size(), nil
}
func (m *mongoBackend) Put(name string, r io.Reader, size int64, hash string) error {
f, err := m.fs.Create(name)
if err != nil {
return errgo.Mask(err)
}
if err := copyAndCheckHash(f, r, hash); err != nil {
f.Abort()
f.Close()
return errgo.Mask(err)
}
if err := f.Close(); err != nil {
return errgo.Mask(err)
}
return nil
}
func (m *mongoBackend) Remove(name string) error {
if err := m.fs.Remove(name); err != nil && err != mgo.ErrNotFound {
return errgo.Notef(err, "cannot delete %q", name)
}
return nil
}
func copyAndCheckHash(w io.Writer, r io.Reader, hash string) error {
hasher := NewHash()
if _, err := io.Copy(io.MultiWriter(w, hasher), r); err != nil {
return err
}
actualHash := fmt.Sprintf("%x", hasher.Sum(nil))
if actualHash != hash {
return errgo.New("hash mismatch")
}
return nil
}
// mongoBackendReader translates not-found errors as
// produced by mgo's GridFS into not-found errors as expected
// by the Backend.Get interface contract.
type mongoBackendReader struct {
ReadSeekCloser
}
func (r mongoBackendReader) Read(buf []byte) (int, error) {
n, err := r.ReadSeekCloser.Read(buf)
if err == nil || err == io.EOF {
return n, err
}
if errgo.Cause(err) == mgo.ErrNotFound {
return n, errgo.WithCausef(err, ErrNotFound, "")
}
return n, errgo.Mask(err)
}