object layer initialization using distributed locking (#2397)

* vendorized latest minio/dsync

* wip - object layer initialization using distributed locking

cmd/routers.go

@@ -49,6 +49,11 @@ func newObjectLayerFactory(disks, ignoredDisks []string) func() ObjectLayer {
 		if objAPI != nil {
 			return objAPI
 		}
+
+		// Acquire a distributed lock to ensure only one of the nodes
+		// initializes the format.json.
+		nsMutex.Lock(minioMetaBucket, formatConfigFile)
+		defer nsMutex.Unlock(minioMetaBucket, formatConfigFile)
 		objAPI, err = newObjectLayer(disks, ignoredDisks)
 		if err != nil {
 			return nil

cmd/rpc-server.go

@@ -92,7 +92,7 @@ func (s *storageServer) ReadAllHandler(arg *ReadFileArgs, reply *[]byte) error {
 	if err != nil {
 		return err
 	}
-	reply = &buf
+	*reply = buf
 	return nil
 }
 
@@ -102,7 +102,7 @@ func (s *storageServer) ReadFileHandler(arg *ReadFileArgs, reply *int64) error {
 	if err != nil {
 		return err
 	}
-	reply = &n
+	*reply = n
 	return nil
 }
 
@@ -160,9 +160,9 @@ func newRPCServer(serverConfig serverCmdConfig) (servers []*storageServer, err e
 
 // registerStorageRPCRouter - register storage rpc router.
 func registerStorageRPCRouters(mux *router.Router, stServers []*storageServer) {
-	storageRPCServer := rpc.NewServer()
 	// Create a unique route for each disk exported from this node.
 	for _, stServer := range stServers {
+		storageRPCServer := rpc.NewServer()
 		storageRPCServer.RegisterName("Storage", stServer)
 		// Add minio storage routes.
 		storageRouter := mux.PathPrefix(reservedBucket).Subrouter()

cmd/server-main.go

@@ -21,11 +21,13 @@ import (
 	"net"
 	"net/http"
 	"os"
+	"path"
 	"strconv"
 	"strings"
 	"time"
 
 	"github.com/minio/cli"
+	"github.com/minio/dsync"
 )
 
 var srvConfig serverCmdConfig
@@ -220,6 +222,29 @@ func getPort(address string) int {
 	return portInt
 }
 
+// Initialize distributed locking only in case of distributed setup.
+func initDsyncNodes(disks []string, port int) error {
+	var isDist bool = false
+	var dsyncNodes []string
+	var rpcPaths []string
+	serverPort := strconv.Itoa(port)
+
+	for _, disk := range disks {
+		if idx := strings.LastIndex(disk, ":"); idx != -1 {
+			dsyncNodes = append(dsyncNodes, disk[:idx]+":"+serverPort)
+			rpcPaths = append(rpcPaths, path.Join(lockRPCPath, disk[idx+1:]))
+		}
+		if !isLocalStorage(disk) {
+			// One or more disks supplied as arguments are remote.
+			isDist = true
+		}
+	}
+	if isDist {
+		return dsync.SetNodesWithPath(dsyncNodes, rpcPaths)
+	}
+	return nil
+}
+
 // serverMain handler called for 'minio server' command.
 func serverMain(c *cli.Context) {
 	// Check 'server' cli arguments.
@@ -245,6 +270,14 @@ func serverMain(c *cli.Context) {
 	// Disks to be used in server init.
 	disks := c.Args()
 
+	// Set nodes for dsync
+	err = initDsyncNodes(disks, port)
+	fatalIf(err, "Unable to initialize distributed locking")
+
+	// Initialize name space lock.
+	// FIXME: add logic to switch between distributed and single-node namespace locking.
+	initNSLock()
+
 	// Configure server.
 	srvConfig = serverCmdConfig{
 		serverAddr:   serverAddress,

lock-rpc-server.go

@@ -26,7 +26,7 @@ import (
 	router "github.com/gorilla/mux"
 )
 
-const lockRPCPath = "/lock"
+const lockRPCPath = "/minio/lock"
 
 type lockServer struct {
 	rpcPath string
@@ -37,7 +37,7 @@ type lockServer struct {
 ///  Distributed lock handlers
 
 // LockHandler - rpc handler for lock operation.
-func (l *lockServer) LockHandler(name *string, reply *bool) error {
+func (l *lockServer) Lock(name *string, reply *bool) error {
 	l.mutex.Lock()
 	defer l.mutex.Unlock()
 	_, ok := l.lockMap[*name]
@@ -51,7 +51,7 @@ func (l *lockServer) LockHandler(name *string, reply *bool) error {
 }
 
 // UnlockHandler - rpc handler for unlock operation.
-func (l *lockServer) UnlockHandler(name *string, reply *bool) error {
+func (l *lockServer) Unlock(name *string, reply *bool) error {
 	l.mutex.Lock()
 	defer l.mutex.Unlock()
 	_, ok := l.lockMap[*name]
@@ -84,6 +84,7 @@ func newLockServers(serverConfig serverCmdConfig) (lockServers []*lockServer) {
 		if skipDisks[export] {
 			continue
 		}
+		if isLocalStorage(export) {
 			if idx := strings.LastIndex(export, ":"); idx != -1 {
 				export = export[idx+1:]
 			}
@@ -93,13 +94,14 @@ func newLockServers(serverConfig serverCmdConfig) (lockServers []*lockServer) {
 				lockMap: make(map[string]struct{}),
 			})
 		}
+	}
 	return lockServers
 }
 
-// registerStorageLockers - register locker rpc handlers for valyala/gorpc library clients
+// registerStorageLockers - register locker rpc handlers for net/rpc library clients
 func registerStorageLockers(mux *router.Router, lockServers []*lockServer) {
-	lockRPCServer := rpc.NewServer()
 	for _, lockServer := range lockServers {
+		lockRPCServer := rpc.NewServer()
 		lockRPCServer.RegisterName("Dsync", lockServer)
 		lockRouter := mux.PathPrefix(reservedBucket).Subrouter()
 		lockRouter.Path(path.Join("/lock", lockServer.rpcPath)).Handler(lockRPCServer)

vendor/github.com/minio/dsync/dmutex.go

@@ -21,7 +21,6 @@ import (
 	"math"
 	"math/rand"
 	"net/rpc"
-	"strings"
 	"sync"
 	"time"
 )
@@ -52,7 +51,7 @@ func connectLazy(dm *DMutex) {
 	for i := range dm.clnts {
 		if dm.clnts[i] == nil {
 			// pass in unique path (as required by server.HandleHTTP()
-			dm.clnts[i], _ = rpc.DialHTTPPath("tcp", nodes[i], rpcPath+"-"+strings.Split(nodes[i], ":")[1])
+			dm.clnts[i], _ = rpc.DialHTTPPath("tcp", nodes[i], rpcPaths[i])
 		}
 	}
 }

vendor/github.com/minio/dsync/dsync.go

@@ -28,7 +28,7 @@ const DefaultPath = "/rpc/dsync"
 
 var n int
 var nodes []string
-var rpcPath string
+var rpcPaths []string
 
 func closeClients(clients []*rpc.Client) {
 	for _, clnt := range clients {
@@ -36,8 +36,8 @@ func closeClients(clients []*rpc.Client) {
 	}
 }
 
-// Same as SetNodes, but takes a path argument different from the package-level default.
+// Same as SetNodes, but takes a slice of rpc paths as argument different from the package-level default.
-func SetNodesWithPath(nodeList []string, path string) (err error) {
+func SetNodesWithPath(nodeList []string, paths []string) (err error) {
 
 	// Validate if number of nodes is within allowable range.
 	if n != 0 {
@@ -50,7 +50,8 @@ func SetNodesWithPath(nodeList []string, path string) (err error) {
 
 	nodes = make([]string, len(nodeList))
 	copy(nodes, nodeList[:])
-	rpcPath = path
+	rpcPaths = make([]string, len(paths))
+	copy(rpcPaths, paths[:])
 	n = len(nodes)
 	return nil
 }

vendor/vendor.json

@@ -98,10 +98,10 @@
 			"revisionTime": "2015-11-18T20:00:48-08:00"
 		},
 		{
-			"checksumSHA1": "KCM0UiuvLA5fPiX5I83/HTklxlI=",
+			"checksumSHA1": "r1Vf/vQTkMsZrDVORBGAAIlOMP4=",
 			"path": "github.com/minio/dsync",
-			"revision": "c10eebd6b637bb834d502a6574c53e0ea6c64997",
+			"revision": "6bfa8c0c1c37959c1bda15bfdae228a986d3cca8",
-			"revisionTime": "2016-08-05T20:56:13Z"
+			"revisionTime": "2016-08-07T19:01:27Z"
 		},
 		{
 			"path": "github.com/minio/go-homedir",