syncthing/vendor/github.com/minio/minio-go/api-get-object-file.go
Jakob Borg 916ec63af6 cmd/stdiscosrv: New discovery server (fixes #4618)
This is a new revision of the discovery server. Relevant changes and
non-changes:

- Protocol towards clients is unchanged.

- Recommended large scale design is still to be deployed nehind nginx (I
  tested, and it's still a lot faster at terminating TLS).

- Database backend is leveldb again, only. It scales enough, is easy to
  setup, and we don't need any backend to take care of.

- Server supports replication. This is a simple TCP channel - protect it
  with a firewall when deploying over the internet. (We deploy this within
  the same datacenter, and with firewall.) Any incoming client announces
  are sent over the replication channel(s) to other peer discosrvs.
  Incoming replication changes are applied to the database as if they came
  from clients, but without the TLS/certificate overhead.

- Metrics are exposed using the prometheus library, when enabled.

- The database values and replication protocol is protobuf, because JSON
  was quite CPU intensive when I tried that and benchmarked it.

- The "Retry-After" value for failed lookups gets slowly increased from
  a default of 120 seconds, by 5 seconds for each failed lookup,
  independently by each discosrv. This lowers the query load over time for
  clients that are never seen. The Retry-After maxes out at 3600 after a
  couple of weeks of this increase. The number of failed lookups is
  stored in the database, now and then (avoiding making each lookup a
  database put).

All in all this means clients can be pointed towards a cluster using
just multiple A / AAAA records to gain both load sharing and redundancy
(if one is down, clients will talk to the remaining ones).

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4648
2018-01-14 08:52:31 +00:00

137 lines
4.0 KiB
Go

/*
* Minio Go Library for Amazon S3 Compatible Cloud Storage
* Copyright 2015-2017 Minio, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package minio
import (
"io"
"os"
"path/filepath"
"github.com/minio/minio-go/pkg/encrypt"
"context"
"github.com/minio/minio-go/pkg/s3utils"
)
// FGetObjectWithContext - download contents of an object to a local file.
// The options can be used to specify the GET request further.
func (c Client) FGetObjectWithContext(ctx context.Context, bucketName, objectName, filePath string, opts GetObjectOptions) error {
return c.fGetObjectWithContext(ctx, bucketName, objectName, filePath, opts)
}
// FGetObject - download contents of an object to a local file.
func (c Client) FGetObject(bucketName, objectName, filePath string, opts GetObjectOptions) error {
return c.fGetObjectWithContext(context.Background(), bucketName, objectName, filePath, opts)
}
// FGetEncryptedObject - Decrypt and store an object at filePath.
func (c Client) FGetEncryptedObject(bucketName, objectName, filePath string, materials encrypt.Materials) error {
if materials == nil {
return ErrInvalidArgument("Unable to recognize empty encryption properties")
}
return c.FGetObject(bucketName, objectName, filePath, GetObjectOptions{Materials: materials})
}
// fGetObjectWithContext - fgetObject wrapper function with context
func (c Client) fGetObjectWithContext(ctx context.Context, bucketName, objectName, filePath string, opts GetObjectOptions) error {
// Input validation.
if err := s3utils.CheckValidBucketName(bucketName); err != nil {
return err
}
if err := s3utils.CheckValidObjectName(objectName); err != nil {
return err
}
// Verify if destination already exists.
st, err := os.Stat(filePath)
if err == nil {
// If the destination exists and is a directory.
if st.IsDir() {
return ErrInvalidArgument("fileName is a directory.")
}
}
// Proceed if file does not exist. return for all other errors.
if err != nil {
if !os.IsNotExist(err) {
return err
}
}
// Extract top level directory.
objectDir, _ := filepath.Split(filePath)
if objectDir != "" {
// Create any missing top level directories.
if err := os.MkdirAll(objectDir, 0700); err != nil {
return err
}
}
// Gather md5sum.
objectStat, err := c.StatObject(bucketName, objectName, StatObjectOptions{opts})
if err != nil {
return err
}
// Write to a temporary file "fileName.part.minio" before saving.
filePartPath := filePath + objectStat.ETag + ".part.minio"
// If exists, open in append mode. If not create it as a part file.
filePart, err := os.OpenFile(filePartPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0600)
if err != nil {
return err
}
// Issue Stat to get the current offset.
st, err = filePart.Stat()
if err != nil {
return err
}
// Initialize get object request headers to set the
// appropriate range offsets to read from.
if st.Size() > 0 {
opts.SetRange(st.Size(), 0)
}
// Seek to current position for incoming reader.
objectReader, objectStat, err := c.getObject(ctx, bucketName, objectName, opts)
if err != nil {
return err
}
// Write to the part file.
if _, err = io.CopyN(filePart, objectReader, objectStat.Size); err != nil {
return err
}
// Close the file before rename, this is specifically needed for Windows users.
if err = filePart.Close(); err != nil {
return err
}
// Safely completed. Now commit by renaming to actual filename.
if err = os.Rename(filePartPath, filePath); err != nil {
return err
}
// Return.
return nil
}