From 2770ceb517738ea895a732ddb5ba94f608e4ccd8 Mon Sep 17 00:00:00 2001
From: Remco <remco@dutchcoders.io>
Date: Fri, 14 Nov 2014 23:32:44 +0100
Subject: [PATCH] resolve #11, multipart upload for large files

---
 transfersh-server/storage.go | 117 ++++++++++++++++++++++++++++++++++-
 1 file changed, 114 insertions(+), 3 deletions(-)

diff --git a/transfersh-server/storage.go b/transfersh-server/storage.go
index ac6aecf..a1c1ba5 100644
--- a/transfersh-server/storage.go
+++ b/transfersh-server/storage.go
@@ -1,13 +1,16 @@
 package main
 
 import (
+	"bytes"
 	"fmt"
 	"github.com/goamz/goamz/s3"
 	"io"
+	"log"
 	"mime"
 	"os"
 	"path/filepath"
 	"strconv"
+	"sync"
 )
 
 type Storage interface {
@@ -136,8 +139,116 @@ func (s *S3Storage) Get(token string, filename string) (reader io.ReadCloser, co
 	return
 }
 
-func (s *S3Storage) Put(token string, filename string, reader io.Reader, contentType string, contentLength uint64) error {
+func (s *S3Storage) Put(token string, filename string, reader io.Reader, contentType string, contentLength uint64) (err error) {
 	key := fmt.Sprintf("%s/%s", token, filename)
-	err := s.bucket.PutReader(key, reader, int64(contentLength), contentType, s3.Private, s3.Options{})
-	return err
+
+	var (
+		multi *s3.Multi
+		parts []s3.Part
+	)
+
+	if multi, err = s.bucket.InitMulti(key, contentType, s3.Private); err != nil {
+		log.Printf(err.Error())
+		return
+	}
+
+	// 20 mb parts
+	partsChan := make(chan interface{})
+	// partsChan := make(chan s3.Part)
+
+	go func() {
+		// maximize to 20 threads
+		sem := make(chan int, 20)
+		index := 1
+		var wg sync.WaitGroup
+
+		for {
+			// buffered in memory because goamz s3 multi needs seekable reader
+			var (
+				buffer []byte = make([]byte, (1<<20)*10)
+				count  int
+				err    error
+			)
+
+			// Amazon expects parts of at least 5MB, except for the last one
+			if count, err = io.ReadAtLeast(reader, buffer, (1<<20)*5); err != nil && err != io.ErrUnexpectedEOF && err != io.EOF {
+				log.Printf(err.Error())
+				return
+			}
+
+			// always send minimal 1 part
+			if err == io.EOF && index > 1 {
+				log.Printf("Waiting for all parts to finish uploading.")
+
+				// wait for all parts to be finished uploading
+				wg.Wait()
+
+				// and close the channel
+				close(partsChan)
+
+				return
+			}
+
+			wg.Add(1)
+
+			sem <- 1
+
+			// using goroutines because of retries when upload fails
+			go func(multi *s3.Multi, buffer []byte, index int) {
+				log.Printf("Uploading part %d %d", index, len(buffer))
+
+				defer func() {
+					log.Printf("Finished part %d %d", index, len(buffer))
+
+					wg.Done()
+
+					<-sem
+				}()
+
+				partReader := bytes.NewReader(buffer)
+
+				var part s3.Part
+
+				if part, err = multi.PutPart(index, partReader); err != nil {
+					log.Printf("Error while uploading part %d %d %s", index, len(buffer), err.Error())
+					partsChan <- err
+					return
+				}
+
+				log.Printf("Finished uploading part %d %d", index, len(buffer))
+
+				partsChan <- part
+
+			}(multi, buffer[:count], index)
+
+			index++
+		}
+	}()
+
+	// wait for all parts to be uploaded
+	for part := range partsChan {
+		switch part.(type) {
+		case s3.Part:
+			parts = append(parts, part.(s3.Part))
+		case error:
+			// abort multi upload
+			log.Printf("Error during upload, aborting %s.", part.(error).Error())
+			err = part.(error)
+
+			multi.Abort()
+			return
+		}
+
+	}
+
+	log.Printf("Completing upload %d parts", len(parts))
+
+	if err = multi.Complete(parts); err != nil {
+		log.Printf("Error during completing upload %d parts %s", len(parts), err.Error())
+		return
+	}
+
+	log.Printf("Completed uploading %d", len(parts))
+
+	return
 }