resolve issue #93

* Add a pause between bucketsDiscovery requests (default is 10 ms)

Author: nurzhan-saktaganov

discovery.go

@@ -261,6 +261,10 @@ func (r *Router) DiscoveryAllBuckets(ctx context.Context) error {
 				}
 
 				bucketsDiscoveryPaginationFrom = resp.NextFrom
+
+				// Don't spam many requests at once. Give storages time to handle them and other requests.
+				// https://github.com/tarantool/vshard/blob/b6fdbe950a2e4557f05b83bd8b846b126ec3724e/vshard/router/init.lua#L308
+				time.Sleep(r.cfg.DiscoveryWorkStep)
 			}
 		})
 	}

vshard.go

@@ -93,8 +93,9 @@ type Config struct {
 
 	// Discovery
 	// DiscoveryTimeout is timeout between cron discovery job; by default there is no timeout.
-	DiscoveryTimeout time.Duration
-	DiscoveryMode    DiscoveryMode
+	DiscoveryTimeout  time.Duration
+	DiscoveryWorkStep time.Duration
+	DiscoveryMode     DiscoveryMode
 
 	// BucketsSearchMode defines policy for BucketDiscovery method.
 	// Default value is BucketsSearchLegacy.
@@ -234,6 +235,7 @@ func (r *Router) RouteMapClean() {
 
 func prepareCfg(cfg Config) (Config, error) {
 	const discoveryTimeoutDefault = 1 * time.Minute
+	const discoveryWorkStepDefault = 10 * time.Millisecond
 
 	err := validateCfg(cfg)
 	if err != nil {
@@ -244,6 +246,10 @@ func prepareCfg(cfg Config) (Config, error) {
 		cfg.DiscoveryTimeout = discoveryTimeoutDefault
 	}
 
+	if cfg.DiscoveryWorkStep == 0 {
+		cfg.DiscoveryWorkStep = discoveryWorkStepDefault
+	}
+
 	if cfg.Loggerf == nil {
 		cfg.Loggerf = emptyLogfProvider
 	}