From 8ff1765674c93a169fe29483503709a008f30618 Mon Sep 17 00:00:00 2001
From: "Guillaume J. Charmes" <guillaume.charmes@dotcloud.com>
Date: Wed, 8 May 2013 10:42:29 -0700
Subject: [PATCH] Make the checksum async within commit

---
 graph.go | 25 +++++++++++++++++++------
 image.go | 27 +++++++++++++++++++++------
 2 files changed, 40 insertions(+), 12 deletions(-)

diff --git a/graph.go b/graph.go
index 9a8fd1b3cb..4b504525e7 100644
--- a/graph.go
+++ b/graph.go
@@ -9,14 +9,18 @@ import (
 	"path"
 	"path/filepath"
 	"strings"
+	"sync"
 	"time"
 )
 
 // A Graph is a store for versioned filesystem images and the relationship between them.
 type Graph struct {
-	Root       string
-	idIndex    *TruncIndex
-	httpClient *http.Client
+	Root         string
+	idIndex      *TruncIndex
+	httpClient   *http.Client
+	checksumLock map[string]*sync.Mutex
+	lockSumFile  *sync.Mutex
+	lockSumMap   *sync.Mutex
 }
 
 // NewGraph instantiates a new graph at the given root path in the filesystem.
@@ -31,8 +35,11 @@ func NewGraph(root string) (*Graph, error) {
 		return nil, err
 	}
 	graph := &Graph{
-		Root:    abspath,
-		idIndex: NewTruncIndex(),
+		Root:         abspath,
+		idIndex:      NewTruncIndex(),
+		checksumLock: make(map[string]*sync.Mutex),
+		lockSumFile:  &sync.Mutex{},
+		lockSumMap:   &sync.Mutex{},
 	}
 	if err := graph.restore(); err != nil {
 		return nil, err
@@ -82,6 +89,11 @@ func (graph *Graph) Get(name string) (*Image, error) {
 		return nil, fmt.Errorf("Image stored at '%s' has wrong id '%s'", id, img.Id)
 	}
 	img.graph = graph
+	graph.lockSumMap.Lock()
+	defer graph.lockSumMap.Unlock()
+	if _, exists := graph.checksumLock[img.Id]; !exists {
+		graph.checksumLock[img.Id] = &sync.Mutex{}
+	}
 	return img, nil
 }
 
@@ -103,7 +115,7 @@ func (graph *Graph) Create(layerData Archive, container *Container, comment, aut
 	if err := graph.Register(layerData, img); err != nil {
 		return nil, err
 	}
-	img.Checksum()
+	go img.Checksum()
 	return img, nil
 }
 
@@ -131,6 +143,7 @@ func (graph *Graph) Register(layerData Archive, img *Image) error {
 	}
 	img.graph = graph
 	graph.idIndex.Add(img.Id)
+	graph.checksumLock[img.Id] = &sync.Mutex{}
 	return nil
 }
 
diff --git a/image.go b/image.go
index 5778931655..3e8ac55d3d 100644
--- a/image.go
+++ b/image.go
@@ -35,8 +35,9 @@ func LoadImage(root string) (*Image, error) {
 	if err != nil {
 		return nil, err
 	}
-	var img Image
-	if err := json.Unmarshal(jsonData, &img); err != nil {
+	img := &Image{}
+
+	if err := json.Unmarshal(jsonData, img); err != nil {
 		return nil, err
 	}
 	if err := ValidateId(img.Id); err != nil {
@@ -52,8 +53,7 @@ func LoadImage(root string) (*Image, error) {
 	} else if !stat.IsDir() {
 		return nil, fmt.Errorf("Couldn't load image %s: %s is not a directory", img.Id, layerPath(root))
 	}
-
-	return &img, nil
+	return img, nil
 }
 
 func StoreImage(img *Image, layerData Archive, root string) error {
@@ -261,6 +261,9 @@ func (img *Image) layer() (string, error) {
 }
 
 func (img *Image) Checksum() (string, error) {
+	img.graph.checksumLock[img.Id].Lock()
+	defer img.graph.checksumLock[img.Id].Unlock()
+
 	root, err := img.root()
 	if err != nil {
 		return "", err
@@ -270,7 +273,7 @@ func (img *Image) Checksum() (string, error) {
 	checksums := make(map[string]string)
 
 	if checksumDict, err := ioutil.ReadFile(checksumDictPth); err == nil {
-		if err := json.Unmarshal(checksumDict, checksums); err != nil {
+		if err := json.Unmarshal(checksumDict, &checksums); err != nil {
 			return "", err
 		}
 		if checksum, ok := checksums[img.Id]; ok {
@@ -299,18 +302,30 @@ func (img *Image) Checksum() (string, error) {
 	if _, err := h.Write([]byte("\n")); err != nil {
 		return "", err
 	}
+
+	fmt.Printf("precopy %s: %s\n", img.ShortId(), time.Now().String())
+
 	if _, err := io.Copy(h, layerData); err != nil {
 		return "", err
 	}
+	fmt.Printf("postcopy presum %s: %s\n", img.ShortId(), time.Now().String())
 
 	hash := "sha256:" + hex.EncodeToString(h.Sum(nil))
 	checksums[img.Id] = hash
+	fmt.Printf("postsum %s: %s\n", img.ShortId(), time.Now().String())
 
+	// Reload the json file to make sure not to overwrite faster sums
+	img.graph.lockSumFile.Lock()
+	defer img.graph.lockSumFile.Unlock()
+	if checksumDict, err := ioutil.ReadFile(checksumDictPth); err == nil {
+		if err := json.Unmarshal(checksumDict, &checksums); err != nil {
+			return "", err
+		}
+	}
 	checksumJson, err := json.Marshal(checksums)
 	if err != nil {
 		return hash, err
 	}
-
 	if err := ioutil.WriteFile(checksumDictPth, checksumJson, 0600); err != nil {
 		return hash, err
 	}