From 9a066460f1572644ef52843be10a554a1e67c8c5 Mon Sep 17 00:00:00 2001
From: Nick Craig-Wood <nick@craig-wood.com>
Date: Sun, 23 Dec 2012 09:32:33 +0000
Subject: [PATCH] Make downloads work in parallel

---
 swiftsync.go | 78 +++++++++++++++++++++++++++++++++-------------------
 1 file changed, 50 insertions(+), 28 deletions(-)

diff --git a/swiftsync.go b/swiftsync.go
index f93be1bfa..88a65f3c5 100644
--- a/swiftsync.go
+++ b/swiftsync.go
@@ -37,7 +37,7 @@ var (
 	userName  = flag.String("user", os.Getenv("ST_USER"), "User name. Defaults to environment var ST_USER.")
 	apiKey    = flag.String("key", os.Getenv("ST_KEY"), "API key (password). Defaults to environment var ST_KEY.")
 	checkers  = flag.Int("checkers", 8, "Number of checkers to run in parallel.")
-	uploaders = flag.Int("uploaders", 4, "Number of uploaders to run in parallel.")
+	transfers = flag.Int("transfers", 4, "Number of file transfers to run in parallel.")
 )
 
 // A filesystem like object which can either be a remote object or a
@@ -193,7 +193,7 @@ func (fs *FsObject) put(c *swift.Connection, container string) {
 	fs.Debugf("Uploaded")
 }
 
-// Stat a FsObject info info
+// Stat a FsObject into info
 func (fs *FsObject) lstat() error {
 	info, err := os.Lstat(fs.path)
 	fs.info = info
@@ -249,15 +249,24 @@ func walk(root string) FsObjectsChan {
 // Read FsObjects on in and write them to out if they need uploading
 //
 // FIXME potentially doing lots of MD5SUMS at once
-func checker(c *swift.Connection, container string, in, out FsObjectsChan, wg *sync.WaitGroup) {
+func checker(c *swift.Connection, container string, in, out FsObjectsChan, upload bool, wg *sync.WaitGroup) {
 	defer wg.Done()
 	for fs := range in {
+		if !upload {
+			_ = fs.lstat()
+			if fs.info == nil {
+				fs.Debugf("Couldn't find local file - download")
+				out <- fs
+				continue
+			}
+		}
+
 		// Check to see if can store this
 		if !fs.storable() {
 			continue
 		}
 		// Check to see if changed or not
-		if fs.Equal(c, container, true) {
+		if fs.Equal(c, container, upload) {
 			fs.Debugf("Unchanged skipping")
 			continue
 		}
@@ -278,17 +287,17 @@ func upload(c *swift.Connection, args []string) {
 	root, container := args[0], args[1]
 	mkdir(c, []string{container})
 	to_be_checked := walk(root)
-	to_be_uploaded := make(FsObjectsChan, *uploaders)
+	to_be_uploaded := make(FsObjectsChan, *transfers)
 
 	var checkerWg sync.WaitGroup
 	checkerWg.Add(*checkers)
 	for i := 0; i < *checkers; i++ {
-		go checker(c, container, to_be_checked, to_be_uploaded, &checkerWg)
+		go checker(c, container, to_be_checked, to_be_uploaded, true, &checkerWg)
 	}
 
 	var uploaderWg sync.WaitGroup
-	uploaderWg.Add(*uploaders)
-	for i := 0; i < *uploaders; i++ {
+	uploaderWg.Add(*transfers)
+	for i := 0; i < *transfers; i++ {
 		go uploader(c, container, to_be_uploaded, &uploaderWg)
 	}
 
@@ -344,12 +353,17 @@ func (fs *FsObject) get(c *swift.Connection, container string) {
 	}
 }
 
+
+// Read FsObjects on in and download them
+func downloader(c *swift.Connection, container string, in FsObjectsChan, wg *sync.WaitGroup) {
+	defer wg.Done()
+	for fs := range in {
+		fs.get(c, container)
+	}
+}
+
 // Syncs a container into a directory
 //
-// FIXME don't want to update the modification times on the
-// remote server if they are different - want to modify the local
-// file!
-//
 // FIXME need optional stat in FsObject and to be able to make FsObjects from ObjectsAll
 //
 // FIXME should download and stat many at once
@@ -366,26 +380,34 @@ func download(c *swift.Connection, args []string) {
 		log.Fatalf("Couldn't make directory %q: %s", root, err)
 	}
 
+	to_be_checked := make(FsObjectsChan, *checkers)
+	to_be_downloaded := make(FsObjectsChan, *transfers)
+
+	var checkerWg sync.WaitGroup
+	checkerWg.Add(*checkers)
+	for i := 0; i < *checkers; i++ {
+		go checker(c, container, to_be_checked, to_be_downloaded, false, &checkerWg)
+	}
+
+	var downloaderWg sync.WaitGroup
+	downloaderWg.Add(*transfers)
+	for i := 0; i < *transfers; i++ {
+		go downloader(c, container, to_be_downloaded, &downloaderWg)
+	}
+
 	for i := range objects {
 		object := &objects[i]
 		filepath := path.Join(root, object.Name)
-		fs := FsObject{remote: object.Name, path: filepath}
-		_ = fs.lstat()
-		if fs.info == nil {
-			fs.Debugf("Couldn't find local file - download")
-		} else {
-			fs.Debugf("Found local file - checking")
-			if !fs.storable() {
-				fs.Debugf("Not overwriting different type local file")
-				continue
-			}
-			if fs.Equal(c, container, false) {
-				fs.Debugf("Skip: not changed")
-				continue
-			}
-		}
-		fs.get(c, container)
+		to_be_checked <- &FsObject{remote: object.Name, path: filepath}
 	}
+	close(to_be_checked)
+
+	log.Printf("Waiting for checks to finish")
+	checkerWg.Wait()
+	close(to_be_downloaded)
+	log.Printf("Waiting for downloads to finish")
+	downloaderWg.Wait()
+
 }
 
 // Lists the containers