[#1609] config: Allow to prioritize N3 endpoints

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

pkg/morph/client/audit/result_test.go

@@ -26,7 +26,7 @@ func TestAuditResults(t *testing.T) {
 	auditHash, err := util.Uint160DecodeStringLE(sAuditHash)
 	require.NoError(t, err)
 
-	morphClient, err := client.New(key, endpoint)
+	morphClient, err := client.New(key, client.WithEndpoints(client.Endpoint{Address: endpoint}))
 	require.NoError(t, err)
 
 	auditClientWrapper, err := NewFromMorph(morphClient, auditHash, 0)

pkg/morph/client/constructor.go

@@ -2,6 +2,7 @@ package client
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"sync"
 	"time"
@@ -35,7 +36,7 @@ type cfg struct {
 
 	signer *transaction.Signer
 
-	extraEndpoints []string
+	endpoints []Endpoint
 
 	singleCli *client.WSClient // neo-go client for single client mode
 
@@ -76,7 +77,7 @@ func defaultConfig() *cfg {
 // If desired option satisfies the default value, it can be omitted.
 // If multiple options of the same config value are supplied,
 // the option with the highest index in the arguments will be used.
-func New(key *keys.PrivateKey, endpoint string, opts ...Option) (*Client, error) {
+func New(key *keys.PrivateKey, opts ...Option) (*Client, error) {
 	if key == nil {
 		panic("empty private key")
 	}
@@ -89,6 +90,10 @@ func New(key *keys.PrivateKey, endpoint string, opts ...Option) (*Client, error)
 		opt(cfg)
 	}
 
+	if len(cfg.endpoints) == 0 {
+		return nil, errors.New("no endpoints were provided")
+	}
+
 	cli := &Client{
 		cache:                  newClientCache(),
 		logger:                 cfg.logger,
@@ -111,9 +116,8 @@ func New(key *keys.PrivateKey, endpoint string, opts ...Option) (*Client, error)
 		// they will be used in switch process, otherwise
 		// inactive mode will be enabled
 		cli.client = cfg.singleCli
-		cli.endpoints.init(cfg.extraEndpoints)
 	} else {
-		ws, err := newWSClient(*cfg, endpoint)
+		ws, err := newWSClient(*cfg, cfg.endpoints[0].Address)
 		if err != nil {
 			return nil, fmt.Errorf("could not create morph client: %w", err)
 		}
@@ -124,8 +128,8 @@ func New(key *keys.PrivateKey, endpoint string, opts ...Option) (*Client, error)
 		}
 
 		cli.client = ws
-		cli.endpoints.init(append([]string{endpoint}, cfg.extraEndpoints...))
 	}
+	cli.endpoints.init(cfg.endpoints)
 
 	go cli.notificationLoop()
 
@@ -206,11 +210,11 @@ func WithSigner(signer *transaction.Signer) Option {
 	}
 }
 
-// WithExtraEndpoints returns a client constructor option
+// WithEndpoints returns a client constructor option
 // that specifies additional Neo rpc endpoints.
-func WithExtraEndpoints(endpoints []string) Option {
+func WithEndpoints(endpoints ...Endpoint) Option {
 	return func(c *cfg) {
-		c.extraEndpoints = append(c.extraEndpoints, endpoints...)
+		c.endpoints = append(c.endpoints, endpoints...)
 	}
 }
 

pkg/morph/client/multi.go

@@ -1,69 +1,46 @@
 package client
 
 import (
+	"sort"
+
 	"go.uber.org/zap"
 )
 
+// Endpoint represents morph endpoint together with its priority.
+type Endpoint struct {
+	Address  string
+	Priority int
+}
+
 type endpoints struct {
 	curr int
-	list []string
+	list []Endpoint
 }
 
-func (e *endpoints) init(ee []string) {
+func (e *endpoints) init(ee []Endpoint) {
+	sort.SliceStable(ee, func(i, j int) bool {
+		return ee[i].Priority > ee[j].Priority
+	})
+
 	e.curr = 0
 	e.list = ee
 }
 
-// next returns the next endpoint and its index
-// to try to connect to.
-// Returns -1 index if there is no known RPC endpoints.
-func (e *endpoints) next() (string, int) {
-	if len(e.list) == 0 {
-		return "", -1
-	}
-
-	next := e.curr + 1
-	if next == len(e.list) {
-		next = 0
-	}
-
-	e.curr = next
-
-	return e.list[next], next
-}
-
-// current returns an endpoint and its index the Client
-// is connected to.
-// Returns -1 index if there is no known RPC endpoints
-func (e *endpoints) current() (string, int) {
-	if len(e.list) == 0 {
-		return "", -1
-	}
-
-	return e.list[e.curr], e.curr
-}
-
 func (c *Client) switchRPC() bool {
 	c.switchLock.Lock()
 	defer c.switchLock.Unlock()
 
 	c.client.Close()
 
-	_, currEndpointIndex := c.endpoints.current()
-	if currEndpointIndex == -1 {
-		// there are no known RPC endpoints to try
-		// to connect to => do not switch
-		return false
-	}
-
-	for {
-		newEndpoint, index := c.endpoints.next()
-		if index == currEndpointIndex {
-			// all the endpoint have been tried
-			// for connection unsuccessfully
-			return false
+	// Iterate endpoints in the order of decreasing priority.
+	// Skip the current endpoint.
+	last := c.endpoints.curr
+	for c.endpoints.curr = range c.endpoints.list {
+		if c.endpoints.curr == last {
+			continue
 		}
 
+		newEndpoint := c.endpoints.list[c.endpoints.curr].Address
 		cli, err := newWSClient(c.cfg, newEndpoint)
 		if err != nil {
 			c.logger.Warn("could not establish connection to the switched RPC node",
@@ -103,6 +80,8 @@ func (c *Client) switchRPC() bool {
 
 		return true
 	}
+
+	return false
 }
 
 func (c *Client) notificationLoop() {