add discovering mvp

box/info.go

@@ -48,6 +48,17 @@
 // Upstream information.
 type Upstream struct {
 	// Status is replication status of the connection with the instance.
+	/*
+	   connect: an instance is connecting to the master.
+	   auth: authentication is being performed.
+	   wait_snapshot: an instance is receiving metadata from the master. If join fails with a non-critical error at this stage (for example, ER_READONLY, ER_ACCESS_DENIED, or a network-related issue), an instance tries to find a new master to join.
+	   fetch_snapshot: an instance is receiving data from the master’s .snap files.
+	   final_join: an instance is receiving new data added during fetch_snapshot.
+	   sync: the master and replica are synchronizing to have the same data.
+	   follow: the current instance’s role is replica. This means that the instance is read-only or acts as a replica for this remote peer in master-master configuration. The instance is receiving or able to receive data from the instance n’s (upstream) master.
+	   stopped: replication is stopped due to a replication error (for example, duplicate key).
+	   disconnected: an instance is not connected to the replica set (for example, due to network issues, not replication errors).
+	*/
 	Status string `msgpack:"status"`
 	// Idle is the time (in seconds) since the last event was received.
 	Idle float64 `msgpack:"idle"`
@@ -61,6 +72,8 @@
 	Message string `msgpack:"message,omitempty"`
 	// SystemMessage contains an error message in case of a degraded state; otherwise, it is nil.
 	SystemMessage string `msgpack:"system_message,omitempty"`
+	// Name - instance name, required only for tarantool 3.
+	Name string `msgpack:"name,omitempty"`
 }
 
 // Downstream information.

pool/connection_pool.go

@@ -19,7 +19,6 @@ import (
 	"time"
 
 	"github.com/tarantool/go-iproto"
-
 	"github.com/tarantool/go-tarantool/v2"
 )
 
@@ -75,12 +74,17 @@ type Instance struct {
 
 // Opts provides additional options (configurable via ConnectWithOpts).
 type Opts struct {
+	DiscoveringDialer tarantool.NetDialer
 	// Timeout for timer to reopen connections that have been closed by some
 	// events and to relocate connection between subpools if ro/rw role has
 	// been updated.
 	CheckTimeout time.Duration
 	// ConnectionHandler provides an ability to handle connection updates.
 	ConnectionHandler ConnectionHandler
+	// WatchTopology start pool auto discovering by replication option
+	EnableDiscovery bool
+	// DiscoveryTimeout timout for discovering function
+	DiscoveryTimeout time.Duration
 }
 
 /*
@@ -103,6 +107,9 @@ Main features:
 - Automatic master discovery by mode parameter.
 */
 type ConnectionPool struct {
+	// root background connection pool ctx
+	ctx context.Context
+
 	ends      map[string]*endpoint
 	endsMutex sync.RWMutex
 
@@ -115,6 +122,8 @@ type ConnectionPool struct {
 	anyPool          *roundRobinStrategy
 	poolsMutex       sync.RWMutex
 	watcherContainer watcherContainer
+
+	discoveringCancel context.CancelFunc
 }
 
 var _ Pooler = (*ConnectionPool)(nil)
@@ -171,6 +180,7 @@ func ConnectWithOpts(ctx context.Context, instances []Instance,
 	anyPool := newRoundRobinStrategy(size)
 
 	connPool := &ConnectionPool{
+		ctx:     ctx,
 		ends:    make(map[string]*endpoint),
 		opts:    opts,
 		state:   connectedState,
@@ -192,6 +202,13 @@ func ConnectWithOpts(ctx context.Context, instances []Instance,
 		go connPool.controller(endpointCtx, endpoint)
 	}
 
+	if opts.EnableDiscovery {
+		err := connPool.StartDiscovery()
+		if err != nil { // it strange if there is error, but we need to check that one
+			return nil, err
+		}
+	}
+
 	return connPool, nil
 }
 

pool/discovering.go

@@ -0,0 +1,95 @@
+package pool
+
+import (
+	"context"
+	"errors"
+	"log"
+	"time"
+
+	"github.com/tarantool/go-tarantool/v2/box"
+)
+
+func (p *ConnectionPool) StartDiscovery() error {
+	if p.discoveringCancel != nil {
+		return errors.New("discovering already started")
+	}
+
+	ctx, cancel := context.WithCancel(p.ctx)
+
+	t := time.NewTicker(p.opts.DiscoveryTimeout)
+
+	go func() {
+		for {
+			select {
+			case <-t.C:
+				// we use any connection, because master can be unavailable
+				info, err := box.New(NewConnectorAdapter(p, ANY)).Info()
+				if err != nil {
+					log.Printf("tarantool: watch topology failed: %s\n", err)
+					continue
+				}
+
+				for _, replication := range info.Replication {
+					upstream := replication.Upstream
+
+					if upstream.Status != "follow" {
+						log.Printf("found replication instance (%s:%s) in non-follow state; skip discovering\n",
+							upstream.Name, upstream.Peer)
+						continue
+					}
+
+					addr := upstream.Peer
+
+					if addr == "" { // itself instance
+						continue
+					}
+
+					name := upstream.Name
+
+					if name == "" {
+						name = replication.UUID
+					}
+
+					p.endsMutex.Lock()
+					_, exists := p.ends[addr]
+					p.endsMutex.Unlock()
+
+					if !exists {
+						dialer := p.opts.DiscoveringDialer
+						dialer.Address = addr
+
+						i := Instance{
+							Name:   name,
+							Dialer: dialer,
+						}
+
+						err = p.Add(ctx, i)
+						if err != nil {
+							log.Printf("tarantool: add to pool failed: %s\n", err)
+							continue
+						}
+					}
+				}
+
+				continue
+			case <-ctx.Done():
+				return
+			}
+		}
+	}()
+
+	p.discoveringCancel = cancel
+
+	return nil
+}
+
+func (p *ConnectionPool) StopDiscovery() error {
+	if p.discoveringCancel != nil {
+		p.discoveringCancel()
+		p.discoveringCancel = nil
+
+		return nil
+	}
+
+	return errors.New("discovering not started yet")
+}