gridfs

package
Version: v1.8.0 Latest Latest
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Published: Nov 23, 2021 License: Apache-2.0 Imports: 16 Imported by: 41

Documentation

Overview

Package gridfs provides a MongoDB GridFS API. See https://docs.mongodb.com/manual/core/gridfs/ for more information about GridFS and its use cases.

Buckets

The main type defined in this package is Bucket. A Bucket wraps a mongo.Database instance and operates on two collections in the database. The first is the files collection, which contains one metadata document per file stored in the bucket. This collection is named "<bucket name>.files". The second is the chunks collection, which contains chunks of files. This collection is named "<bucket name>.chunks".

Uploading a File

Files can be uploaded in two ways:

1. OpenUploadStream/OpenUploadStreamWithID - These methods return an UploadStream instance. UploadStream
implements the io.Writer interface and the Write() method can be used to upload a file to the database.

2. UploadFromStream/UploadFromStreamWithID - These methods take an io.Reader, which represents the file to
upload. They internally create a new UploadStream and close it once the operation is complete.

Downloading a File

Similar to uploads, files can be downloaded in two ways:

1. OpenDownloadStream/OpenDownloadStreamByName - These methods return a DownloadStream instance. DownloadStream
implements the io.Reader interface. A file can be read either using the Read() method or any standard library
methods that reads from an io.Reader such as io.Copy.

2. DownloadToStream/DownloadToStreamByName - These methods take an io.Writer, which represents the download
destination. They internally create a new DownloadStream and close it once the operation is complete.

Index

Examples

Constants

View Source
const DefaultChunkSize int32 = 255 * 1024 // 255 KiB

DefaultChunkSize is the default size of each file chunk.

View Source
const UploadBufferSize = 16 * 1024 * 1024 // 16 MiB

UploadBufferSize is the size in bytes of one stream batch. Chunks will be written to the db after the sum of chunk lengths is equal to the batch size.

Variables

View Source
var ErrFileNotFound = errors.New("file with given parameters not found")

ErrFileNotFound occurs if a user asks to download a file with a file ID that isn't found in the files collection.

View Source
var ErrMissingChunkSize = errors.New("files collection document does not contain a 'chunkSize' field")

ErrMissingChunkSize occurs when downloading a file if the files collection document is missing the "chunkSize" field.

View Source
var ErrStreamClosed = errors.New("stream is closed or aborted")

ErrStreamClosed is an error returned if an operation is attempted on a closed/aborted stream.

View Source
var ErrWrongIndex = errors.New("chunk index does not match expected index")

ErrWrongIndex is used when the chunk retrieved from the server does not have the expected index.

View Source
var ErrWrongSize = errors.New("chunk size does not match expected size")

ErrWrongSize is used when the chunk retrieved from the server does not have the expected size.

Functions

This section is empty.

Types

type Bucket

type Bucket struct {
	// contains filtered or unexported fields
}

Bucket represents a GridFS bucket.

func NewBucket

func NewBucket(db *mongo.Database, opts ...*options.BucketOptions) (*Bucket, error)

NewBucket creates a GridFS bucket.

func (*Bucket) Delete

func (b *Bucket) Delete(fileID interface{}) error

Delete deletes all chunks and metadata associated with the file with the given file ID.

If this operation requires a custom write deadline to be set on the bucket, it cannot be done concurrently with other write operations operations on this bucket that also require a custom deadline.

Example
package main

import (
	"log"

	"go.mongodb.org/mongo-driver/bson/primitive"
	"go.mongodb.org/mongo-driver/mongo/gridfs"
)

func main() {
	var bucket *gridfs.Bucket
	var fileID primitive.ObjectID

	if err := bucket.Delete(fileID); err != nil {
		log.Fatal(err)
	}
}
Output:

func (*Bucket) DownloadToStream

func (b *Bucket) DownloadToStream(fileID interface{}, stream io.Writer) (int64, error)

DownloadToStream downloads the file with the specified fileID and writes it to the provided io.Writer. Returns the number of bytes written to the steam and an error, or nil if there was no error.

If this download requires a custom read deadline to be set on the bucket, it cannot be done concurrently with other read operations operations on this bucket that also require a custom deadline.

Example
package main

import (
	"bytes"
	"log"

	"go.mongodb.org/mongo-driver/bson/primitive"
	"go.mongodb.org/mongo-driver/mongo/gridfs"
)

func main() {
	var bucket *gridfs.Bucket
	var fileID primitive.ObjectID

	fileBuffer := bytes.NewBuffer(nil)
	if _, err := bucket.DownloadToStream(fileID, fileBuffer); err != nil {
		log.Fatal(err)
	}
}
Output:

func (*Bucket) DownloadToStreamByName

func (b *Bucket) DownloadToStreamByName(filename string, stream io.Writer, opts ...*options.NameOptions) (int64, error)

DownloadToStreamByName downloads the file with the given name to the given io.Writer.

If this download requires a custom read deadline to be set on the bucket, it cannot be done concurrently with other read operations operations on this bucket that also require a custom deadline.

func (*Bucket) Drop

func (b *Bucket) Drop() error

Drop drops the files and chunks collections associated with this bucket.

If this operation requires a custom write deadline to be set on the bucket, it cannot be done concurrently with other write operations operations on this bucket that also require a custom deadline

Example
package main

import (
	"log"

	"go.mongodb.org/mongo-driver/mongo/gridfs"
)

func main() {
	var bucket *gridfs.Bucket

	if err := bucket.Drop(); err != nil {
		log.Fatal(err)
	}
}
Output:

func (*Bucket) Find

func (b *Bucket) Find(filter interface{}, opts ...*options.GridFSFindOptions) (*mongo.Cursor, error)

Find returns the files collection documents that match the given filter.

If this download requires a custom read deadline to be set on the bucket, it cannot be done concurrently with other read operations operations on this bucket that also require a custom deadline.

Example
package main

import (
	"context"
	"fmt"
	"log"

	"go.mongodb.org/mongo-driver/bson"
	"go.mongodb.org/mongo-driver/mongo/gridfs"
)

func main() {
	var bucket *gridfs.Bucket

	// Specify a filter to find all files with a length greater than 1000 bytes.
	filter := bson.D{
		{"length", bson.D{{"$gt", 1000}}},
	}
	cursor, err := bucket.Find(filter)
	if err != nil {
		log.Fatal(err)
	}
	defer func() {
		if err := cursor.Close(context.TODO()); err != nil {
			log.Fatal(err)
		}
	}()

	type gridfsFile struct {
		Name   string `bson:"filename"`
		Length int64  `bson:"length"`
	}
	var foundFiles []gridfsFile
	if err = cursor.All(context.TODO(), &foundFiles); err != nil {
		log.Fatal(err)
	}

	for _, file := range foundFiles {
		fmt.Printf("filename: %s, length: %d\n", file.Name, file.Length)
	}
}
Output:

func (*Bucket) GetChunksCollection added in v1.4.0

func (b *Bucket) GetChunksCollection() *mongo.Collection

GetChunksCollection returns a handle to the collection that stores the file chunks for this bucket.

func (*Bucket) GetFilesCollection added in v1.4.0

func (b *Bucket) GetFilesCollection() *mongo.Collection

GetFilesCollection returns a handle to the collection that stores the file documents for this bucket.

func (*Bucket) OpenDownloadStream

func (b *Bucket) OpenDownloadStream(fileID interface{}) (*DownloadStream, error)

OpenDownloadStream creates a stream from which the contents of the file can be read.

Example
package main

import (
	"bytes"
	"io"
	"log"
	"time"

	"go.mongodb.org/mongo-driver/bson/primitive"
	"go.mongodb.org/mongo-driver/mongo/gridfs"
)

func main() {
	var bucket *gridfs.Bucket
	var fileID primitive.ObjectID

	downloadStream, err := bucket.OpenDownloadStream(fileID)
	if err != nil {
		log.Fatal(err)
	}
	defer func() {
		if err := downloadStream.Close(); err != nil {
			log.Fatal(err)
		}
	}()

	// Use SetReadDeadline to force a timeout if the download does not succeed
	// in 2 seconds.
	err = downloadStream.SetReadDeadline(time.Now().Add(2 * time.Second))
	if err != nil {
		log.Fatal(err)
	}

	fileBuffer := bytes.NewBuffer(nil)
	if _, err := io.Copy(fileBuffer, downloadStream); err != nil {
		log.Fatal(err)
	}
}
Output:

func (*Bucket) OpenDownloadStreamByName

func (b *Bucket) OpenDownloadStreamByName(filename string, opts ...*options.NameOptions) (*DownloadStream, error)

OpenDownloadStreamByName opens a download stream for the file with the given filename.

func (*Bucket) OpenUploadStream

func (b *Bucket) OpenUploadStream(filename string, opts ...*options.UploadOptions) (*UploadStream, error)

OpenUploadStream creates a file ID new upload stream for a file given the filename.

Example
package main

import (
	"log"
	"time"

	"go.mongodb.org/mongo-driver/bson"
	"go.mongodb.org/mongo-driver/mongo/gridfs"
	"go.mongodb.org/mongo-driver/mongo/options"
)

func main() {
	var fileContent []byte
	var bucket *gridfs.Bucket

	// Specify the Metadata option to include a "metadata" field in the files
	// collection document.
	uploadOpts := options.GridFSUpload().
		SetMetadata(bson.D{{"metadata tag", "tag"}})
	uploadStream, err := bucket.OpenUploadStream("filename", uploadOpts)
	if err != nil {
		log.Fatal(err)
	}
	defer func() {
		if err = uploadStream.Close(); err != nil {
			log.Fatal(err)
		}
	}()

	// Use SetWriteDeadline to force a timeout if the upload does not succeed in
	// 2 seconds.
	err = uploadStream.SetWriteDeadline(time.Now().Add(2 * time.Second))
	if err != nil {
		log.Fatal(err)
	}

	if _, err = uploadStream.Write(fileContent); err != nil {
		log.Fatal(err)
	}
}
Output:

func (*Bucket) OpenUploadStreamWithID

func (b *Bucket) OpenUploadStreamWithID(fileID interface{}, filename string, opts ...*options.UploadOptions) (*UploadStream, error)

OpenUploadStreamWithID creates a new upload stream for a file given the file ID and filename.

func (*Bucket) Rename

func (b *Bucket) Rename(fileID interface{}, newFilename string) error

Rename renames the stored file with the specified file ID.

If this operation requires a custom write deadline to be set on the bucket, it cannot be done concurrently with other write operations operations on this bucket that also require a custom deadline

Example
package main

import (
	"log"

	"go.mongodb.org/mongo-driver/bson/primitive"
	"go.mongodb.org/mongo-driver/mongo/gridfs"
)

func main() {
	var bucket *gridfs.Bucket
	var fileID primitive.ObjectID

	if err := bucket.Rename(fileID, "new file name"); err != nil {
		log.Fatal(err)
	}
}
Output:

func (*Bucket) SetReadDeadline

func (b *Bucket) SetReadDeadline(t time.Time) error

SetReadDeadline sets the read deadline for this bucket

func (*Bucket) SetWriteDeadline

func (b *Bucket) SetWriteDeadline(t time.Time) error

SetWriteDeadline sets the write deadline for this bucket.

func (*Bucket) UploadFromStream

func (b *Bucket) UploadFromStream(filename string, source io.Reader, opts ...*options.UploadOptions) (primitive.ObjectID, error)

UploadFromStream creates a fileID and uploads a file given a source stream.

If this upload requires a custom write deadline to be set on the bucket, it cannot be done concurrently with other write operations operations on this bucket that also require a custom deadline.

Example
package main

import (
	"bytes"
	"fmt"
	"log"

	"go.mongodb.org/mongo-driver/bson"
	"go.mongodb.org/mongo-driver/mongo/gridfs"
	"go.mongodb.org/mongo-driver/mongo/options"
)

func main() {
	var fileContent []byte
	var bucket *gridfs.Bucket

	// Specify the Metadata option to include a "metadata" field in the files
	// collection document.
	uploadOpts := options.GridFSUpload().
		SetMetadata(bson.D{{"metadata tag", "tag"}})
	fileID, err := bucket.UploadFromStream(
		"filename",
		bytes.NewBuffer(fileContent),
		uploadOpts)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Printf("new file created with ID %s", fileID)
}
Output:

func (*Bucket) UploadFromStreamWithID

func (b *Bucket) UploadFromStreamWithID(fileID interface{}, filename string, source io.Reader, opts ...*options.UploadOptions) error

UploadFromStreamWithID uploads a file given a source stream.

If this upload requires a custom write deadline to be set on the bucket, it cannot be done concurrently with other write operations operations on this bucket that also require a custom deadline.

type DownloadStream

type DownloadStream struct {
	// contains filtered or unexported fields
}

DownloadStream is a io.Reader that can be used to download a file from a GridFS bucket.

func (*DownloadStream) Close

func (ds *DownloadStream) Close() error

Close closes this download stream.

func (*DownloadStream) GetFile added in v1.4.0

func (ds *DownloadStream) GetFile() *File

GetFile returns a File object representing the file being downloaded.

func (*DownloadStream) Read

func (ds *DownloadStream) Read(p []byte) (int, error)

Read reads the file from the server and writes it to a destination byte slice.

func (*DownloadStream) SetReadDeadline

func (ds *DownloadStream) SetReadDeadline(t time.Time) error

SetReadDeadline sets the read deadline for this download stream.

func (*DownloadStream) Skip

func (ds *DownloadStream) Skip(skip int64) (int64, error)

Skip skips a given number of bytes in the file.

type File added in v1.4.0

type File struct {
	// ID is the file's ID. This will match the file ID specified when uploading the file. If an upload helper that
	// does not require a file ID was used, this field will be a primitive.ObjectID.
	ID interface{}

	// Length is the length of this file in bytes.
	Length int64

	// ChunkSize is the maximum number of bytes for each chunk in this file.
	ChunkSize int32

	// UploadDate is the time this file was added to GridFS in UTC. This field is set by the driver and is not configurable.
	// The Metadata field can be used to store a custom date.
	UploadDate time.Time

	// Name is the name of this file.
	Name string

	// Metadata is additional data that was specified when creating this file. This field can be unmarshalled into a
	// custom type using the bson.Unmarshal family of functions.
	Metadata bson.Raw
}

File represents a file stored in GridFS. This type can be used to access file information when downloading using the DownloadStream.GetFile method.

func (*File) UnmarshalBSON added in v1.4.0

func (f *File) UnmarshalBSON(data []byte) error

UnmarshalBSON implements the bson.Unmarshaler interface.

type Upload

type Upload struct {
	// contains filtered or unexported fields
}

Upload contains options to upload a file to a bucket.

type UploadStream

type UploadStream struct {
	*Upload // chunk size and metadata
	FileID  interface{}
	// contains filtered or unexported fields
}

UploadStream is used to upload a file in chunks. This type implements the io.Writer interface and a file can be uploaded using the Write method. After an upload is complete, the Close method must be called to write file metadata.

func (*UploadStream) Abort

func (us *UploadStream) Abort() error

Abort closes the stream and deletes all file chunks that have already been written.

func (*UploadStream) Close

func (us *UploadStream) Close() error

Close writes file metadata to the files collection and cleans up any resources associated with the UploadStream.

func (*UploadStream) SetWriteDeadline

func (us *UploadStream) SetWriteDeadline(t time.Time) error

SetWriteDeadline sets the write deadline for this stream.

func (*UploadStream) Write

func (us *UploadStream) Write(p []byte) (int, error)

Write transfers the contents of a byte slice into this upload stream. If the stream's underlying buffer fills up, the buffer will be uploaded as chunks to the server. Implements the io.Writer interface.

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