Bring semantic versioning to provide for rolling upgrades (#5495)

This PR brings semver capabilities in our RPC layer to
ensure that we can upgrade the servers in rolling fashion
while keeping I/O in progress. This is only a framework change
the functionality remains the same as such and we do not
have any special API changes for now. But in future when
we bring in API changes we will be able to upgrade servers
without a downtime.

Additional change in this PR is to not abort when serverVersions
mismatch in a distributed cluster, instead wait for the quorum
treat the situation as if the server is down. This allows
for administrator to properly upgrade all the servers in the cluster.

Fixes #5393

cmd/admin-rpc-server_test.go

@@ -42,7 +42,7 @@ func testAdminCmd(cmd cmdType, t *testing.T) {
 	adminServer := adminCmd{}
 	args := LoginRPCArgs{
 		AuthToken:   token,
-		Version:     Version,
+		Version:     globalRPCAPIVersion,
 		RequestTime: UTCNow(),
 	}
 	err = adminServer.Login(&args, &LoginRPCReply{})
@@ -56,9 +56,10 @@ func testAdminCmd(cmd cmdType, t *testing.T) {
 	}()
 
 	sa := SignalServiceArgs{
-		AuthRPCArgs: AuthRPCArgs{AuthToken: token},
+		AuthRPCArgs: AuthRPCArgs{AuthToken: token, Version: globalRPCAPIVersion},
 		Sig:         cmd.toServiceSignal(),
 	}
+
 	genReply := AuthRPCReply{}
 	switch cmd {
 	case restartCmd, stopCmd:
@@ -123,7 +124,7 @@ func TestReInitDisks(t *testing.T) {
 
 	args := LoginRPCArgs{
 		AuthToken:   token,
-		Version:     Version,
+		Version:     globalRPCAPIVersion,
 		RequestTime: UTCNow(),
 	}
 	err = adminServer.Login(&args, &LoginRPCReply{})
@@ -133,6 +134,7 @@ func TestReInitDisks(t *testing.T) {
 
 	authArgs := AuthRPCArgs{
 		AuthToken: token,
+		Version:   globalRPCAPIVersion,
 	}
 	authReply := AuthRPCReply{}
 
@@ -150,7 +152,7 @@ func TestReInitDisks(t *testing.T) {
 	fsAdminServer := adminCmd{}
 	fsArgs := LoginRPCArgs{
 		AuthToken:   token,
-		Version:     Version,
+		Version:     globalRPCAPIVersion,
 		RequestTime: UTCNow(),
 	}
 	fsReply := LoginRPCReply{}
@@ -161,6 +163,7 @@ func TestReInitDisks(t *testing.T) {
 
 	authArgs = AuthRPCArgs{
 		AuthToken: token,
+		Version:   globalRPCAPIVersion,
 	}
 	authReply = AuthRPCReply{}
 	// Attempt ReInitDisks service on a FS backend.
@@ -192,7 +195,7 @@ func TestGetConfig(t *testing.T) {
 
 	args := LoginRPCArgs{
 		AuthToken:   token,
-		Version:     Version,
+		Version:     globalRPCAPIVersion,
 		RequestTime: UTCNow(),
 	}
 	reply := LoginRPCReply{}
@@ -203,6 +206,7 @@ func TestGetConfig(t *testing.T) {
 
 	authArgs := AuthRPCArgs{
 		AuthToken: token,
+		Version:   globalRPCAPIVersion,
 	}
 
 	configReply := ConfigReply{}
@@ -239,7 +243,7 @@ func TestWriteAndCommitConfig(t *testing.T) {
 	}
 	args := LoginRPCArgs{
 		AuthToken:   token,
-		Version:     Version,
+		Version:     globalRPCAPIVersion,
 		RequestTime: UTCNow(),
 	}
 	reply := LoginRPCReply{}
@@ -254,6 +258,7 @@ func TestWriteAndCommitConfig(t *testing.T) {
 	wArgs := WriteConfigArgs{
 		AuthRPCArgs: AuthRPCArgs{
 			AuthToken: token,
+			Version:   globalRPCAPIVersion,
 		},
 		TmpFileName: tmpFileName,
 		Buf:         buf,
@@ -271,6 +276,7 @@ func TestWriteAndCommitConfig(t *testing.T) {
 	cArgs := CommitConfigArgs{
 		AuthRPCArgs: AuthRPCArgs{
 			AuthToken: token,
+			Version:   globalRPCAPIVersion,
 		},
 		FileName: tmpFileName,
 	}

cmd/auth-rpc-client.go

@@ -26,6 +26,7 @@ import (
 	"net"
 	"net/http"
 	"net/rpc"
+	"strings"
 	"sync"
 	"time"
 )
@@ -61,9 +62,10 @@ type authConfig struct {
 // AuthRPCClient is a authenticated RPC client which does authentication before doing Call().
 type AuthRPCClient struct {
 	sync.RWMutex             // Mutex to lock this object.
-	rpcClient    *rpc.Client // RPC Client to make any RPC call.
+	rpcClient    *rpc.Client // RPC client to make any RPC call.
 	config       authConfig  // Authentication configuration information.
 	authToken    string      // Authentication token.
+	version      semVersion  // RPC version.
 }
 
 // newAuthRPCClient - returns a JWT based authenticated (go) rpc client, which does automatic reconnect.
@@ -81,7 +83,8 @@ func newAuthRPCClient(config authConfig) *AuthRPCClient {
 	}
 
 	return &AuthRPCClient{
-		config: config,
+		config:  config,
+		version: globalRPCAPIVersion,
 	}
 }
 
@@ -117,7 +120,7 @@ func (authClient *AuthRPCClient) Login() (err error) {
 			loginMethod = authClient.config.serviceName + loginMethodName
 			loginArgs   = LoginRPCArgs{
 				AuthToken:   authToken,
-				Version:     Version,
+				Version:     globalRPCAPIVersion,
 				RequestTime: UTCNow(),
 			}
 		)
@@ -130,6 +133,11 @@ func (authClient *AuthRPCClient) Login() (err error) {
 		}
 
 		if err = rpcClient.Call(loginMethod, &loginArgs, &LoginRPCReply{}); err != nil {
+			// gob doesn't provide any typed errors for us to reflect
+			// upon, this is the only way to return proper error.
+			if strings.Contains(err.Error(), "gob: wrong type") {
+				return errRPCAPIVersionUnsupported
+			}
 			return err
 		}
 
@@ -144,6 +152,7 @@ func (authClient *AuthRPCClient) Login() (err error) {
 // call makes a RPC call after logs into the server.
 func (authClient *AuthRPCClient) call(serviceMethod string, args interface {
 	SetAuthToken(authToken string)
+	SetRPCAPIVersion(version semVersion)
 }, reply interface{}) (err error) {
 	if err = authClient.Login(); err != nil {
 		return err
@@ -153,6 +162,7 @@ func (authClient *AuthRPCClient) call(serviceMethod string, args interface {
 	authClient.RLock()
 	defer authClient.RUnlock()
 	args.SetAuthToken(authClient.authToken)
+	args.SetRPCAPIVersion(authClient.version)
 
 	// Do an RPC call.
 	return authClient.rpcClient.Call(serviceMethod, args, reply)
@@ -161,6 +171,7 @@ func (authClient *AuthRPCClient) call(serviceMethod string, args interface {
 // Call executes RPC call till success or globalAuthRPCRetryThreshold on ErrShutdown.
 func (authClient *AuthRPCClient) Call(serviceMethod string, args interface {
 	SetAuthToken(authToken string)
+	SetRPCAPIVersion(version semVersion)
 }, reply interface{}) (err error) {
 
 	// Done channel is used to close any lingering retry routine, as soon
@@ -181,6 +192,11 @@ func (authClient *AuthRPCClient) Call(serviceMethod string, args interface {
 				}
 			}
 		}
+		// gob doesn't provide any typed errors for us to reflect
+		// upon, this is the only way to return proper error.
+		if err != nil && strings.Contains(err.Error(), "gob: wrong type") {
+			err = errRPCAPIVersionUnsupported
+		}
 		break
 	}
 	return err

cmd/auth-rpc-server_test.go

@@ -43,7 +43,7 @@ func TestLogin(t *testing.T) {
 		{
 			args: LoginRPCArgs{
 				AuthToken: token,
-				Version:   Version,
+				Version:   globalRPCAPIVersion,
 			},
 			skewTime:    0,
 			expectedErr: nil,
@@ -52,16 +52,16 @@ func TestLogin(t *testing.T) {
 		{
 			args: LoginRPCArgs{
 				AuthToken: token,
-				Version:   "INVALID-" + Version,
+				Version:   semVersion{2, 0, 0},
 			},
 			skewTime:    0,
-			expectedErr: errServerVersionMismatch,
+			expectedErr: errRPCAPIVersionUnsupported,
 		},
 		// Valid username, password and version, not request time
 		{
 			args: LoginRPCArgs{
 				AuthToken: token,
-				Version:   Version,
+				Version:   globalRPCAPIVersion,
 			},
 			skewTime:    20 * time.Minute,
 			expectedErr: errServerTimeMismatch,
@@ -70,7 +70,7 @@ func TestLogin(t *testing.T) {
 		{
 			args: LoginRPCArgs{
 				AuthToken: "",
-				Version:   Version,
+				Version:   globalRPCAPIVersion,
 			},
 			skewTime:    0,
 			expectedErr: errAuthentication,

cmd/globals.go

@@ -165,6 +165,9 @@ var (
 	// Set to store standard storage class
 	globalStandardStorageClass storageClass
 
+	// RPC version.
+	globalRPCAPIVersion = semVersion{1, 0, 0}
+
 	// Add new variable global values here.
 )
 

cmd/lock-rpc-server_test.go

@@ -64,7 +64,7 @@ func createLockTestServer(t *testing.T) (string, *lockServer, string) {
 	}
 	loginArgs := LoginRPCArgs{
 		AuthToken:   token,
-		Version:     Version,
+		Version:     globalRPCAPIVersion,
 		RequestTime: UTCNow(),
 	}
 	loginReply := LoginRPCReply{}
@@ -87,6 +87,7 @@ func TestLockRpcServerLock(t *testing.T) {
 		ServiceEndpoint: "rpc-path",
 	})
 	la.SetAuthToken(token)
+	la.SetRPCAPIVersion(globalRPCAPIVersion)
 
 	// Claim a lock
 	var result bool
@@ -120,6 +121,7 @@ func TestLockRpcServerLock(t *testing.T) {
 		ServiceEndpoint: "rpc-path",
 	})
 	la2.SetAuthToken(token)
+	la2.SetRPCAPIVersion(globalRPCAPIVersion)
 
 	err = locker.Lock(&la2, &result)
 	if err != nil {
@@ -143,6 +145,7 @@ func TestLockRpcServerUnlock(t *testing.T) {
 		ServiceEndpoint: "rpc-path",
 	})
 	la.SetAuthToken(token)
+	la.SetRPCAPIVersion(globalRPCAPIVersion)
 
 	// First test return of error when attempting to unlock a lock that does not exist
 	var result bool
@@ -188,6 +191,7 @@ func TestLockRpcServerRLock(t *testing.T) {
 		ServiceEndpoint: "rpc-path",
 	})
 	la.SetAuthToken(token)
+	la.SetRPCAPIVersion(globalRPCAPIVersion)
 
 	// Claim a lock
 	var result bool
@@ -221,6 +225,7 @@ func TestLockRpcServerRLock(t *testing.T) {
 		ServiceEndpoint: "rpc-path",
 	})
 	la2.SetAuthToken(token)
+	la2.SetRPCAPIVersion(globalRPCAPIVersion)
 
 	err = locker.RLock(&la2, &result)
 	if err != nil {
@@ -244,6 +249,7 @@ func TestLockRpcServerRUnlock(t *testing.T) {
 		ServiceEndpoint: "rpc-path",
 	})
 	la.SetAuthToken(token)
+	la.SetRPCAPIVersion(globalRPCAPIVersion)
 
 	// First test return of error when attempting to unlock a read-lock that does not exist
 	var result bool
@@ -268,6 +274,7 @@ func TestLockRpcServerRUnlock(t *testing.T) {
 		ServiceEndpoint: "rpc-path",
 	})
 	la2.SetAuthToken(token)
+	la2.SetRPCAPIVersion(globalRPCAPIVersion)
 
 	// ... and create a second lock on same resource
 	err = locker.RLock(&la2, &result)
@@ -330,6 +337,7 @@ func TestLockRpcServerForceUnlock(t *testing.T) {
 		ServiceEndpoint: "rpc-path",
 	})
 	laForce.SetAuthToken(token)
+	laForce.SetRPCAPIVersion(globalRPCAPIVersion)
 
 	// First test that UID should be empty
 	var result bool
@@ -352,6 +360,7 @@ func TestLockRpcServerForceUnlock(t *testing.T) {
 		ServiceEndpoint: "rpc-path",
 	})
 	la.SetAuthToken(token)
+	la.SetRPCAPIVersion(globalRPCAPIVersion)
 
 	// Create lock ... (so that we can force unlock)
 	err = locker.Lock(&la, &result)
@@ -394,6 +403,7 @@ func TestLockRpcServerExpired(t *testing.T) {
 		ServiceEndpoint: "rpc-path",
 	})
 	la.SetAuthToken(token)
+	la.SetRPCAPIVersion(globalRPCAPIVersion)
 
 	// Unknown lock at server will return expired = true
 	var expired bool

cmd/prepare-storage.go

@@ -101,13 +101,13 @@ const (
 var configErrs = []error{
 	errInvalidAccessKeyID,
 	errAuthentication,
-	errServerVersionMismatch,
+	errRPCAPIVersionUnsupported,
 	errServerTimeMismatch,
 }
 
-// Quick error to actions converts looking for specific errors
+// Config errs to actions converts looking for specific config errors
 // which need to be returned quickly and server should wait instead.
-func quickErrToActions(errMap map[error]int) InitActions {
+func configErrsToActions(errMap map[error]int) InitActions {
 	var action InitActions
 	for _, configErr := range configErrs {
 		if errMap[configErr] > 0 {
@@ -168,7 +168,7 @@ func prepForInitXL(firstDisk bool, sErrs []error, diskCount int) InitActions {
 	}
 
 	// Validates and converts specific config errors into WaitForConfig.
-	if quickErrToActions(errMap) == WaitForConfig {
+	if configErrsToActions(errMap) == WaitForConfig {
 		return WaitForConfig
 	}
 
@@ -311,13 +311,15 @@ func retryFormattingXLDisks(firstDisk bool, endpoints EndpointList, storageDisks
 				)
 			case WaitForConfig:
 				// Print configuration errors.
-				return reduceInitXLErrs(storageDisks, sErrs)
+				log.Printf(
+					"Initializing data volume. Waiting for configuration issues to be fixed (%s). (elapsed %s)\n",
+					reduceInitXLErrs(storageDisks, sErrs), getElapsedTime())
 			case WaitForAll:
 				log.Printf("Initializing data volume for first time. Waiting for other servers to come online (elapsed %s)\n", getElapsedTime())
 			case WaitForFormatting:
 				log.Printf("Initializing data volume for first time. Waiting for first server to come online (elapsed %s)\n", getElapsedTime())
 			}
-		case <-globalServiceDoneCh:
+		case <-globalOSSignalCh:
 			return fmt.Errorf("Initializing data volumes gracefully stopped")
 		}
 	}

cmd/prepare-storage_test.go

@@ -67,7 +67,7 @@ func TestReduceInitXLErrs(t *testing.T) {
 		{[]error{nil, nil, nil, nil}, ""},
 		{[]error{errUnformattedDisk, nil, nil, nil}, "\n[01/04] " + storageDisks[0].String() + " : unformatted disk found"},
 		{[]error{errUnformattedDisk, errUnformattedDisk, nil, nil}, "\n[01/04] " + storageDisks[0].String() + " : unformatted disk found" + "\n[02/04] " + storageDisks[1].String() + " : unformatted disk found"},
-		{[]error{errUnformattedDisk, errUnformattedDisk, errServerVersionMismatch, nil}, storageDisks[2].String() + ": Server versions do not match"},
+		{[]error{errUnformattedDisk, errUnformattedDisk, errRPCAPIVersionUnsupported, nil}, storageDisks[2].String() + ": Unsupported rpc API version"},
 	}
 	for i, test := range testCases {
 		actual := reduceInitXLErrs(storageDisks, test.sErrs)
@@ -123,24 +123,29 @@ func TestPrepForInitXL(t *testing.T) {
 	}
 	// Invalid access key id.
 	accessKeyIDErr := []error{
+		errInvalidAccessKeyID, errInvalidAccessKeyID, errInvalidAccessKeyID, errInvalidAccessKeyID,
 		errInvalidAccessKeyID, nil, nil, nil,
-		nil, nil, nil, nil,
 	}
 	// Authentication error.
 	authenticationErr := []error{
-		nil, nil, nil, nil,
-		errAuthentication, nil, nil, nil,
+		nil, nil, nil, errAuthentication,
+		errAuthentication, errAuthentication, errAuthentication, errAuthentication,
 	}
-	// Server version mismatch.
-	serverVersionMismatch := []error{
-		errServerVersionMismatch, nil, nil, nil,
-		errServerVersionMismatch, nil, nil, nil,
+	// Unsupported rpc API version.
+	rpcUnsupportedVersion := []error{
+		errRPCAPIVersionUnsupported, errRPCAPIVersionUnsupported, errRPCAPIVersionUnsupported, errRPCAPIVersionUnsupported,
+		errRPCAPIVersionUnsupported, nil, nil, nil,
 	}
 	// Server time mismatch.
 	serverTimeMismatch := []error{
-		nil, nil, nil, nil,
+		errServerTimeMismatch, errServerTimeMismatch, errServerTimeMismatch, errServerTimeMismatch,
 		errServerTimeMismatch, nil, nil, nil,
 	}
+	// Collection of config errs.
+	configErrs := []error{
+		errServerTimeMismatch, errServerTimeMismatch, errRPCAPIVersionUnsupported, errAuthentication,
+		errInvalidAccessKeyID, nil, nil, nil,
+	}
 	// Suggest to heal under formatted disks in quorum.
 	formattedDisksInQuorum := []error{
 		nil, nil, nil, nil,
@@ -187,8 +192,9 @@ func TestPrepForInitXL(t *testing.T) {
 		// Config mistakes.
 		{true, accessKeyIDErr, 8, WaitForConfig},
 		{true, authenticationErr, 8, WaitForConfig},
-		{true, serverVersionMismatch, 8, WaitForConfig},
+		{true, rpcUnsupportedVersion, 8, WaitForConfig},
 		{true, serverTimeMismatch, 8, WaitForConfig},
+		{true, configErrs, 8, WaitForConfig},
 	}
 	for i, test := range testCases {
 		actual := prepForInitXL(test.firstDisk, test.errs, test.diskCount)

cmd/rpc-common.go

@@ -1,5 +1,5 @@
 /*
- * Minio Cloud Storage, (C) 2016, 2017 Minio, Inc.
+ * Minio Cloud Storage, (C) 2016, 2017, 2018 Minio, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,6 +17,7 @@
 package cmd
 
 import (
+	"strconv"
 	"time"
 
 	"github.com/minio/dsync"
@@ -33,10 +34,51 @@ func isRequestTimeAllowed(requestTime time.Time) bool {
 		utcNow.Sub(requestTime) > rpcSkewTimeAllowed)
 }
 
+// semVersion - RPC semantic versioning.
+type semVersion struct {
+	Major uint64
+	Minor uint64
+	Patch uint64
+}
+
+// semver comparator implementation based on the semver 2.0.0 https://semver.org/.
+func (v semVersion) Compare(o semVersion) int {
+	if v.Major != o.Major {
+		if v.Major > o.Major {
+			return 1
+		}
+		return -1
+	}
+	if v.Minor != o.Minor {
+		if v.Minor > o.Minor {
+			return 1
+		}
+		return -1
+	}
+	if v.Patch != o.Patch {
+		if v.Patch > o.Patch {
+			return 1
+		}
+		return -1
+	}
+	return 0
+}
+
+func (v semVersion) String() string {
+	b := make([]byte, 0, 5)
+	b = strconv.AppendUint(b, v.Major, 10)
+	b = append(b, '.')
+	b = strconv.AppendUint(b, v.Minor, 10)
+	b = append(b, '.')
+	b = strconv.AppendUint(b, v.Patch, 10)
+	return string(b)
+}
+
 // AuthRPCArgs represents minimum required arguments to make any authenticated RPC call.
 type AuthRPCArgs struct {
 	// Authentication token to be verified by the server for every RPC call.
 	AuthToken string
+	Version   semVersion
 }
 
 // SetAuthToken - sets the token to the supplied value.
@@ -44,8 +86,21 @@ func (args *AuthRPCArgs) SetAuthToken(authToken string) {
 	args.AuthToken = authToken
 }
 
+// SetRPCAPIVersion - sets the rpc version to the supplied value.
+func (args *AuthRPCArgs) SetRPCAPIVersion(version semVersion) {
+	args.Version = version
+}
+
 // IsAuthenticated - validated whether this auth RPC args are already authenticated or not.
 func (args AuthRPCArgs) IsAuthenticated() error {
+	// checks if rpc Version is not equal to current server rpc version.
+	// this is fine for now, but in future when we add backward compatible
+	// APIs we need to make sure to allow lesser versioned clients to
+	// talk over RPC, until then we are fine with this check.
+	if args.Version.Compare(globalRPCAPIVersion) != 0 {
+		return errRPCAPIVersionUnsupported
+	}
+
 	// Check whether the token is valid
 	if !isAuthTokenValid(args.AuthToken) {
 		return errInvalidToken
@@ -61,15 +116,18 @@ type AuthRPCReply struct{}
 // LoginRPCArgs - login username and password for RPC.
 type LoginRPCArgs struct {
 	AuthToken   string
-	Version     string
+	Version     semVersion
 	RequestTime time.Time
 }
 
 // IsValid - validates whether this LoginRPCArgs are valid for authentication.
 func (args LoginRPCArgs) IsValid() error {
-	// Check if version matches.
-	if args.Version != Version {
-		return errServerVersionMismatch
+	// checks if rpc Version is not equal to current server rpc version.
+	// this is fine for now, but in future when we add backward compatible
+	// APIs we need to make sure to allow lesser versioned clients to
+	// talk over RPC, until then we are fine with this check.
+	if args.Version.Compare(globalRPCAPIVersion) != 0 {
+		return errRPCAPIVersionUnsupported
 	}
 
 	if !isRequestTimeAllowed(args.RequestTime) {

cmd/rpc-common_test.go

@@ -0,0 +1,56 @@
+/*
+ * Minio Cloud Storage, (C) 2018 Minio, Inc.
+ *
+ * Licensed under the Apache License, semVersion 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cmd
+
+import "testing"
+
+// Tests version comparator.
+func TestCompare(t *testing.T) {
+	type compareTest struct {
+		v1     semVersion
+		v2     semVersion
+		result int
+	}
+
+	var compareTests = []compareTest{
+		{semVersion{1, 0, 0}, semVersion{1, 0, 0}, 0},
+		{semVersion{2, 0, 0}, semVersion{1, 0, 0}, 1},
+		{semVersion{0, 1, 0}, semVersion{0, 1, 0}, 0},
+		{semVersion{0, 2, 0}, semVersion{0, 1, 0}, 1},
+		{semVersion{0, 0, 1}, semVersion{0, 0, 1}, 0},
+		{semVersion{0, 0, 2}, semVersion{0, 0, 1}, 1},
+		{semVersion{1, 2, 3}, semVersion{1, 2, 3}, 0},
+		{semVersion{2, 2, 4}, semVersion{1, 2, 4}, 1},
+		{semVersion{1, 3, 3}, semVersion{1, 2, 3}, 1},
+		{semVersion{1, 2, 4}, semVersion{1, 2, 3}, 1},
+
+		// Spec Examples #11
+		{semVersion{1, 0, 0}, semVersion{2, 0, 0}, -1},
+		{semVersion{2, 0, 0}, semVersion{2, 1, 0}, -1},
+		{semVersion{2, 1, 0}, semVersion{2, 1, 1}, -1},
+	}
+
+	for _, test := range compareTests {
+		if res := test.v1.Compare(test.v2); res != test.result {
+			t.Errorf("Comparing %q : %q, expected %d but got %d", test.v1, test.v2, test.result, res)
+		}
+		// Test if reverse is true as well.
+		if res := test.v2.Compare(test.v1); res != -test.result {
+			t.Errorf("Comparing %q : %q, expected %d but got %d", test.v2, test.v1, -test.result, res)
+		}
+	}
+}

cmd/storage-rpc-client.go

@@ -85,8 +85,8 @@ func toStorageErr(err error) error {
 		return errInvalidAccessKeyID
 	case errAuthentication.Error():
 		return errAuthentication
-	case errServerVersionMismatch.Error():
-		return errServerVersionMismatch
+	case errRPCAPIVersionUnsupported.Error():
+		return errRPCAPIVersionUnsupported
 	case errServerTimeMismatch.Error():
 		return errServerTimeMismatch
 	}

cmd/storage-rpc-client_test.go

@@ -190,8 +190,8 @@ func TestStorageErr(t *testing.T) {
 			err:         fmt.Errorf("%s", errAuthentication.Error()),
 		},
 		{
-			expectedErr: errServerVersionMismatch,
-			err:         fmt.Errorf("%s", errServerVersionMismatch.Error()),
+			expectedErr: errRPCAPIVersionUnsupported,
+			err:         fmt.Errorf("%s", errRPCAPIVersionUnsupported.Error()),
 		},
 		{
 			expectedErr: errServerTimeMismatch,

cmd/storage-rpc-server_test.go

@@ -55,9 +55,8 @@ func createTestStorageServer(t *testing.T) *testStorageRPCServer {
 		t.Fatalf("unable to initialize storage disks, %s", err)
 	}
 	stServer := &storageServer{
-		storage:   storageDisks[0],
-		path:      "/disk1",
-		timestamp: UTCNow(),
+		storage: storageDisks[0],
+		path:    "/disk1",
 	}
 	return &testStorageRPCServer{
 		token:     token,
@@ -85,7 +84,10 @@ func TestStorageRPCInvalidToken(t *testing.T) {
 	// Following test cases are meant to exercise the invalid
 	// token code path of the storage RPC methods.
 	var err error
-	badAuthRPCArgs := AuthRPCArgs{AuthToken: "invalidToken"}
+	badAuthRPCArgs := AuthRPCArgs{
+		Version:   globalRPCAPIVersion,
+		AuthToken: "invalidToken",
+	}
 	badGenericVolArgs := GenericVolArgs{
 		AuthRPCArgs: badAuthRPCArgs,
 		Vol:         "myvol",

cmd/typed-errors.go

@@ -42,8 +42,8 @@ var errDataTooSmall = errors.New("Object size smaller than expected")
 // errServerNotInitialized - server not initialized.
 var errServerNotInitialized = errors.New("Server not initialized, please try again")
 
-// errServerVersionMismatch - server versions do not match.
-var errServerVersionMismatch = errors.New("Server versions do not match")
+// errRPCAPIVersionUnsupported - unsupported rpc API version.
+var errRPCAPIVersionUnsupported = errors.New("Unsupported rpc API version")
 
 // errServerTimeMismatch - server times are too far apart.
 var errServerTimeMismatch = errors.New("Server times are too far apart")

cmd/web-handlers_test.go

@@ -192,7 +192,9 @@ func testStorageInfoWebHandler(obj ObjectLayer, instanceType string, t TestErrHa
 
 	rec := httptest.NewRecorder()
 
-	storageInfoRequest := AuthRPCArgs{}
+	storageInfoRequest := AuthRPCArgs{
+		Version: globalRPCAPIVersion,
+	}
 	storageInfoReply := &StorageInfoRep{}
 	req, err := newTestWebRPCRequest("Web.StorageInfo", authorization, storageInfoRequest)
 	if err != nil {
@@ -229,7 +231,9 @@ func testServerInfoWebHandler(obj ObjectLayer, instanceType string, t TestErrHan
 
 	rec := httptest.NewRecorder()
 
-	serverInfoRequest := AuthRPCArgs{}
+	serverInfoRequest := AuthRPCArgs{
+		Version: globalRPCAPIVersion,
+	}
 	serverInfoReply := &ServerInfoRep{}
 	req, err := newTestWebRPCRequest("Web.ServerInfo", authorization, serverInfoRequest)
 	if err != nil {
@@ -1493,7 +1497,9 @@ func TestWebCheckAuthorization(t *testing.T) {
 		"PresignedGet",
 	}
 	for _, rpcCall := range webRPCs {
-		args := &AuthRPCArgs{}
+		args := &AuthRPCArgs{
+			Version: globalRPCAPIVersion,
+		}
 		reply := &WebGenericRep{}
 		req, nerr := newTestWebRPCRequest("Web."+rpcCall, "Bearer fooauthorization", args)
 		if nerr != nil {
@@ -1577,7 +1583,9 @@ func TestWebObjectLayerNotReady(t *testing.T) {
 	webRPCs := []string{"StorageInfo", "MakeBucket", "ListBuckets", "ListObjects", "RemoveObject",
 		"GetBucketPolicy", "SetBucketPolicy", "ListAllBucketPolicies"}
 	for _, rpcCall := range webRPCs {
-		args := &AuthRPCArgs{}
+		args := &AuthRPCArgs{
+			Version: globalRPCAPIVersion,
+		}
 		reply := &WebGenericRep{}
 		req, nerr := newTestWebRPCRequest("Web."+rpcCall, authorization, args)
 		if nerr != nil {
@@ -1690,7 +1698,7 @@ func TestWebObjectLayerFaultyDisks(t *testing.T) {
 		RepArgs    interface{}
 	}{
 		{"MakeBucket", MakeBucketArgs{BucketName: bucketName}, WebGenericRep{}},
-		{"ListBuckets", AuthRPCArgs{}, ListBucketsRep{}},
+		{"ListBuckets", AuthRPCArgs{Version: globalRPCAPIVersion}, ListBucketsRep{}},
 		{"ListObjects", ListObjectsArgs{BucketName: bucketName, Prefix: ""}, ListObjectsRep{}},
 		{"GetBucketPolicy", GetBucketPolicyArgs{BucketName: bucketName, Prefix: ""}, GetBucketPolicyRep{}},
 		{"SetBucketPolicy", SetBucketPolicyArgs{BucketName: bucketName, Prefix: "", Policy: "none"}, WebGenericRep{}},
@@ -1714,7 +1722,9 @@ func TestWebObjectLayerFaultyDisks(t *testing.T) {
 	}
 
 	// Test Web.StorageInfo
-	storageInfoRequest := AuthRPCArgs{}
+	storageInfoRequest := AuthRPCArgs{
+		Version: globalRPCAPIVersion,
+	}
 	storageInfoReply := &StorageInfoRep{}
 	req, err := newTestWebRPCRequest("Web.StorageInfo", authorization, storageInfoRequest)
 	if err != nil {