morph: support reloading morph endpoints with SIGHUP

Add a new function `Client.Reload` that passes the `WithEndpoints` option and
updates the `Client` endpoints.
Add docs.

Closes #1871.

Signed-off-by: Andrey Butusov <andrey@nspcc.io>

CHANGELOG.md

@@ -17,6 +17,7 @@ attribute, which is used for container domain name in NNS contracts (#2954)
 - `neofs-cli control object revive` command (#2968)
 - `--disable-auto-gen-tag` flag for gendoc command (#2983)
 - Docs files for cli commands to the `docs/cli-commands` folder (#2983)
+- Reloading morph endpoints with SIGHUP (#2998)
 
 ### Fixed
 - Do not search for tombstones when handling their expiration, use local indexes instead (#2929)

cmd/neofs-node/config.go

@@ -870,6 +870,10 @@ func (c *cfg) configWatcher(ctx context.Context) {
 				continue
 			}
 
+			// Morph
+
+			c.cli.Reload(client.WithEndpoints(c.morph.endpoints))
+
 			c.log.Info("configuration has been reloaded successfully")
 		case <-ctx.Done():
 			return

docs/sighup.md

@@ -32,3 +32,9 @@ comparing paths from `shard.blobstor` section. After this we have 3 sets:
 | Changed section | Actions                                                                                                              |
 |-----------------|----------------------------------------------------------------------------------------------------------------------|
 | `path`          | If `path` is different, metabase is closed and opened with a new path. All other configuration will also be updated. |
+
+### Morph
+
+| Changed section | Actions              |
+|-----------------|----------------------|
+| `endpoints`     | Update N3 endpoints. |

pkg/morph/client/constructor.go

@@ -40,7 +40,8 @@ type cfg struct {
 	autoSidechainScope bool
 	signer             *transaction.Signer
 
-	endpoints []string
+	endpoints     []string
+	endpointsLock *sync.RWMutex
 
 	singleCli *rpcclient.WSClient // neo-go client for single client mode
 
@@ -63,6 +64,7 @@ func defaultConfig() *cfg {
 		signer: &transaction.Signer{
 			Scopes: transaction.CalledByEntry,
 		},
+		endpointsLock:       &sync.RWMutex{},
 		reconnectionDelay:   5 * time.Second,
 		reconnectionRetries: 5,
 	}

pkg/morph/client/multi.go

@@ -33,6 +33,9 @@ func (c *Client) switchRPC() *connection {
 }
 
 func (c *Client) connEndpoints() *connection {
+	c.cfg.endpointsLock.RLock()
+	defer c.cfg.endpointsLock.RUnlock()
+
 	// Iterate endpoints.
 	for _, e := range c.cfg.endpoints {
 		conn, err := c.newConnection(e)

pkg/morph/client/reload.go

@@ -0,0 +1,15 @@
+package client
+
+// Reload allows runtime reconfiguration for WithEndpoints parameter.
+func (c *Client) Reload(opts ...Option) {
+	cfg := new(cfg)
+	for _, o := range opts {
+		o(cfg)
+	}
+
+	c.cfg.endpointsLock.Lock()
+
+	c.cfg.endpoints = cfg.endpoints
+
+	c.cfg.endpointsLock.Unlock()
+}