fixup! Node: Add support for NEO cluster with > 1 master

- no need to keep Node.MasterAddr anymore - the address of current PM is
  managed by TalkMaster and is provided as part of operational context
  to user functions that TalkMaster runs.

- correct docstrings.

- cosmetics.

go/neo/client.go

-// Copyright (C) 2017-2021  Nexedi SA and Contributors.
+// Copyright (C) 2017-2023  Nexedi SA and Contributors.
 //                          Kirill Smelkov <kirr@nexedi.com>
 //
 // This program is free software: you can Use, Study, Modify and Redistribute
@@ -78,7 +78,7 @@ var _ zodb.IStorageDriver = (*Client)(nil)
 
 // NewClient creates new client node.
 //
-// It will connect to master @masterAddr and identify with specified cluster name.
+// It will connect to a master with address from masterAddrSlice and identify with specified cluster name.
 // Use Run to actually start running the node.
 func NewClient(clusterName string, masterAddrSlice []string, net xnet.Networker) *Client {
 	c := &Client{
@@ -542,8 +542,7 @@ func (c *Client) URL() string {
 	if strings.Contains(c.node.Net.Network(), "+tls") {
 		zurl += "s"
 	}
-	zurl += fmt.Sprintf(
-		"://%s/%s", strings.Join(c.node.MasterAddrSlice, ","), c.node.ClusterName,
+	zurl += fmt.Sprintf("://%s/%s", strings.Join(c.node.MasterAddrSlice, ","), c.node.ClusterName,
 	)
 	return zurl
 }

go/neo/master.go

@@ -219,8 +219,7 @@ func (m *Master) Run(ctx context.Context, l xnet.Listener) (err error) {
 	if err != nil {
 		return err
 	}
-        // NOTE: How can this master node know the address of the
-        //       other master nodes?
+	// XXX How can this master node know the address of the other master nodes?
 	m.node.MasterAddrSlice = []string{addr.String()}
 	m.node.MyInfo = proto.NodeInfo{
 		Type:	proto.MASTER,

go/neo/mastered.go

-// Copyright (C) 2017-2021  Nexedi SA and Contributors.
+// Copyright (C) 2017-2023  Nexedi SA and Contributors.
 //                          Kirill Smelkov <kirr@nexedi.com>
 //
 // This program is free software: you can Use, Study, Modify and Redistribute
@@ -84,7 +84,9 @@ const (
 	δPartTabPassThrough _MasteredNodeFlags = 1 << iota
 )
 
-// newMasteredNode creates new _MasteredNode that connects to masterAddr/cluster via net.
+// newMasteredNode creates new _MasteredNode that connects to masters/cluster via net.
+//
+// Addresses of known masters are specified by masterAddrSlice.
 func newMasteredNode(typ proto.NodeType, clusterName string, net xnet.Networker, masterAddrSlice []string) *_MasteredNode {
 	node := &_MasteredNode{
 		Node: xneo.NewNode(typ, clusterName, net, masterAddrSlice),
@@ -110,22 +112,17 @@ func (node *_MasteredNode) TalkMaster(ctx context.Context, f func(context.Contex
 	ctx0 := ctx
 
 	// When a node is created with "NewNode", we don't know yet, which of the
-	// the provided master nodes is the primary master. We'll figure this our here
+	// the provided master nodes is the primary master. We'll figure this out here
 	// and simply start with the first node.
-	// We don't assign 'MasterAddr' in 'NewNode', because master nodes are also
-	// created with the 'NewNode' method and master nodes don't know their Addr yet
-	// during initialization time: it's only assigned later when 'Run' is called.
-	if (node.MasterAddr == "") {
-		node.MasterAddr = node.MasterAddrSlice[0]
-	}
+	maddr := node.MasterAddrSlice[0]
 
-	defer task.Runningf(&ctx, "%s: talk master(%s)", node.MyInfo.NID, node.MasterAddr)(&err)
+	defer task.Runningf(&ctx, "%s: talk master(%s)", node.MyInfo.NID, maddr)(&err)
 
 	for {
 		node.updateOperational(func() {
 			node.mlink = nil
 		})
-		err := node.talkMaster1(ctx, ctx0, f, node.MasterAddr)
+		err := node.talkMaster1(ctx, ctx0, maddr, f)
 		log.Warning(ctx, err)	// XXX Warning -> Error?
 		if errors.Is(err, cmdShutdown) {
 			return err // M commands to shutdown
@@ -134,7 +131,7 @@ func (node *_MasteredNode) TalkMaster(ctx context.Context, f func(context.Contex
 		var notPrimaryMaster *proto.NotPrimaryMaster
 		if errors.As(err, &notPrimaryMaster) {
 			primary := notPrimaryMaster.KnownMasterList[notPrimaryMaster.Primary]
-			node.MasterAddr = fmt.Sprintf("[%s]:%v", primary.Host, primary.Port)
+			maddr = fmt.Sprintf("[%s]:%v", primary.Host, primary.Port)
 		}
 
 		// TODO if err == "reject identification / protocol error" -> shutdown client?
@@ -151,7 +148,7 @@ func (node *_MasteredNode) TalkMaster(ctx context.Context, f func(context.Contex
 	}
 }
 
-func (node *_MasteredNode) talkMaster1(ctx, ctxPreTalkM context.Context, f func(context.Context, *_MasterLink) error, masterAddr string) error {
+func (node *_MasteredNode) talkMaster1(ctx, ctxPreTalkM context.Context, maddr string, f func(context.Context, *_MasterLink) error) error {
 	reqID := &proto.RequestIdentification{
 		NodeType:	node.MyInfo.Type,
 		NID:		node.MyInfo.NID,
@@ -161,7 +158,7 @@ func (node *_MasteredNode) talkMaster1(ctx, ctxPreTalkM context.Context, f func(
 		DevPath:        nil,                // XXX stub
 		NewNID:         nil,	            // XXX stub
 	}
-	mlink, accept, err := xneo.Dial(ctx, proto.MASTER, node.Net, masterAddr, reqID)
+	mlink, accept, err := xneo.Dial(ctx, proto.MASTER, node.Net, maddr, reqID)
 	if err != nil {
 		return err
 	}

go/neo/xneo/xneo.go

@@ -79,8 +79,7 @@ type Node struct {
 	MyInfo          proto.NodeInfo // type, laddr, nid, state, idtime
 	ClusterName     string
 	Net             xnet.Networker // network AP we are sending/receiving on
-	MasterAddr      string         // address of current master  TODO -> masterRegistry
-	MasterAddrSlice []string       // address of all known masters
+	MasterAddrSlice []string       // address of all known masters  TODO -> masterRegistry
 
 	// XXX reconsider not using State and have just .NodeTab, .PartTab, .ClusterState
 //	StateMu	sync.RWMutex	// <- XXX unexport ?   XXX not used -> move to MasteredNode ?