From 34c1d0ed5076994ef18338bb1ee0a8390357fd6f Mon Sep 17 00:00:00 2001
From: Sylvain Baubeau <sbaubeau@redhat.com>
Date: Thu, 29 Oct 2015 12:24:56 +0100
Subject: [PATCH] Ensure read after write for segments

Signed-off-by: Sylvain Baubeau <sbaubeau@redhat.com>
---
 docs/storage/driver/swift/swift.go | 64 +++++++++++++++++++++++++-----
 1 file changed, 53 insertions(+), 11 deletions(-)

diff --git a/docs/storage/driver/swift/swift.go b/docs/storage/driver/swift/swift.go
index c9d623d37..b0237281d 100644
--- a/docs/storage/driver/swift/swift.go
+++ b/docs/storage/driver/swift/swift.go
@@ -20,6 +20,7 @@ package swift
 
 import (
 	"bytes"
+	"crypto/md5"
 	"crypto/rand"
 	"crypto/sha1"
 	"crypto/tls"
@@ -52,6 +53,12 @@ const defaultChunkSize = 20 * 1024 * 1024
 // minChunkSize defines the minimum size of a segment
 const minChunkSize = 1 << 20
 
+// readAfterWriteTimeout defines the time we wait before an object appears after having been uploaded
+var readAfterWriteTimeout = 15 * time.Second
+
+// readAfterWriteWait defines the time to sleep between two retries
+var readAfterWriteWait = 200 * time.Millisecond
+
 // Parameters A struct that encapsulates all of the driver parameters after all values have been set
 type Parameters struct {
 	Username           string
@@ -252,6 +259,7 @@ func (d *driver) WriteStream(ctx context.Context, path string, offset int64, rea
 	partNumber := 1
 	chunkSize := int64(d.ChunkSize)
 	zeroBuf := make([]byte, d.ChunkSize)
+	hash := md5.New()
 
 	getSegment := func() string {
 		return fmt.Sprintf("%s/%016d", segmentPath, partNumber)
@@ -292,18 +300,13 @@ func (d *driver) WriteStream(ctx context.Context, path string, offset int64, rea
 		return 0, err
 	}
 
-	if createManifest {
-		if err := d.createManifest(path, d.Container+"/"+segmentPath); err != nil {
-			return 0, err
-		}
-	}
-
 	// First, we skip the existing segments that are not modified by this call
 	for i := range segments {
 		if offset < cursor+segments[i].Bytes {
 			break
 		}
 		cursor += segments[i].Bytes
+		hash.Write([]byte(segments[i].Hash))
 		partNumber++
 	}
 
@@ -312,7 +315,7 @@ func (d *driver) WriteStream(ctx context.Context, path string, offset int64, rea
 	if offset >= currentLength {
 		for offset-currentLength >= chunkSize {
 			// Insert a block a zero
-			_, err := d.Conn.ObjectPut(d.Container, getSegment(), bytes.NewReader(zeroBuf), false, "", d.getContentType(), nil)
+			headers, err := d.Conn.ObjectPut(d.Container, getSegment(), bytes.NewReader(zeroBuf), false, "", d.getContentType(), nil)
 			if err != nil {
 				if err == swift.ObjectNotFound {
 					return 0, storagedriver.PathNotFoundError{Path: getSegment()}
@@ -321,6 +324,7 @@ func (d *driver) WriteStream(ctx context.Context, path string, offset int64, rea
 			}
 			currentLength += chunkSize
 			partNumber++
+			hash.Write([]byte(headers["Etag"]))
 		}
 
 		cursor = currentLength
@@ -355,13 +359,23 @@ func (d *driver) WriteStream(ctx context.Context, path string, offset int64, rea
 			return false, bytesRead, err
 		}
 
-		n, err := io.Copy(currentSegment, multi)
+		segmentHash := md5.New()
+		writer := io.MultiWriter(currentSegment, segmentHash)
+
+		n, err := io.Copy(writer, multi)
 		if err != nil {
 			return false, bytesRead, err
 		}
 
 		if n > 0 {
-			defer currentSegment.Close()
+			defer func() {
+				closeError := currentSegment.Close()
+				if err != nil {
+					err = closeError
+				}
+				hexHash := hex.EncodeToString(segmentHash.Sum(nil))
+				hash.Write([]byte(hexHash))
+			}()
 			bytesRead += n - max(0, offset-cursor)
 		}
 
@@ -379,7 +393,7 @@ func (d *driver) WriteStream(ctx context.Context, path string, offset int64, rea
 					return false, bytesRead, err
 				}
 
-				_, copyErr := io.Copy(currentSegment, file)
+				_, copyErr := io.Copy(writer, file)
 
 				if err := file.Close(); err != nil {
 					if err == swift.ObjectNotFound {
@@ -414,7 +428,35 @@ func (d *driver) WriteStream(ctx context.Context, path string, offset int64, rea
 		}
 	}
 
-	return bytesRead, nil
+	for ; partNumber < len(segments); partNumber++ {
+		hash.Write([]byte(segments[partNumber].Hash))
+	}
+
+	if createManifest {
+		if err := d.createManifest(path, d.Container+"/"+segmentPath); err != nil {
+			return 0, err
+		}
+	}
+
+	expectedHash := hex.EncodeToString(hash.Sum(nil))
+	waitingTime := readAfterWriteWait
+	endTime := time.Now().Add(readAfterWriteTimeout)
+	for {
+		var infos swift.Object
+		if infos, _, err = d.Conn.Object(d.Container, d.swiftPath(path)); err == nil {
+			if strings.Trim(infos.Hash, "\"") == expectedHash {
+				return bytesRead, nil
+			}
+			err = fmt.Errorf("Timeout expired while waiting for segments of %s to show up", path)
+		}
+		if time.Now().Add(waitingTime).After(endTime) {
+			break
+		}
+		time.Sleep(waitingTime)
+		waitingTime *= 2
+	}
+
+	return bytesRead, err
 }
 
 // Stat retrieves the FileInfo for the given path, including the current size