fix: Avoid concurrent map writes in go-routines (#5898)

Fixes #5897

cmd/notification.go

@@ -59,94 +59,126 @@ func (sys *NotificationSys) GetPeerRPCClient(addr xnet.Host) *PeerRPCClient {
 	return sys.peerRPCClientMap[addr]
 }
 
+// NotificationPeerErr returns error associated for a remote peer.
+type NotificationPeerErr struct {
+	Host xnet.Host // Remote host on which the rpc call was initiated
+	Err  error     // Error returned by the remote peer for an rpc call
+}
+
 // DeleteBucket - calls DeleteBucket RPC call on all peers.
-func (sys *NotificationSys) DeleteBucket(bucketName string) map[xnet.Host]error {
-	errors := make(map[xnet.Host]error)
+func (sys *NotificationSys) DeleteBucket(bucketName string) []NotificationPeerErr {
+	errs := make([]NotificationPeerErr, len(sys.peerRPCClientMap))
 	var wg sync.WaitGroup
+	idx := 0
 	for addr, client := range sys.peerRPCClientMap {
 		wg.Add(1)
-		go func(addr xnet.Host, client *PeerRPCClient) {
+		go func(idx int, addr xnet.Host, client *PeerRPCClient) {
 			defer wg.Done()
 			if err := client.DeleteBucket(bucketName); err != nil {
-				errors[addr] = err
+				errs[idx] = NotificationPeerErr{
+					Host: addr,
+					Err:  err,
+				}
 			}
-		}(addr, client)
+		}(idx, addr, client)
+		idx++
 	}
 	wg.Wait()
 
-	return errors
+	return errs
 }
 
 // SetBucketPolicy - calls SetBucketPolicy RPC call on all peers.
-func (sys *NotificationSys) SetBucketPolicy(bucketName string, bucketPolicy *policy.Policy) map[xnet.Host]error {
-	errors := make(map[xnet.Host]error)
+func (sys *NotificationSys) SetBucketPolicy(bucketName string, bucketPolicy *policy.Policy) []NotificationPeerErr {
+	errs := make([]NotificationPeerErr, len(sys.peerRPCClientMap))
 	var wg sync.WaitGroup
+	idx := 0
 	for addr, client := range sys.peerRPCClientMap {
 		wg.Add(1)
-		go func(addr xnet.Host, client *PeerRPCClient) {
+		go func(idx int, addr xnet.Host, client *PeerRPCClient) {
 			defer wg.Done()
 			if err := client.SetBucketPolicy(bucketName, bucketPolicy); err != nil {
-				errors[addr] = err
+				errs[idx] = NotificationPeerErr{
+					Host: addr,
+					Err:  err,
+				}
 			}
-		}(addr, client)
+		}(idx, addr, client)
+		idx++
 	}
 	wg.Wait()
 
-	return errors
+	return errs
 }
 
 // RemoveBucketPolicy - calls RemoveBucketPolicy RPC call on all peers.
-func (sys *NotificationSys) RemoveBucketPolicy(bucketName string) map[xnet.Host]error {
-	errors := make(map[xnet.Host]error)
+func (sys *NotificationSys) RemoveBucketPolicy(bucketName string) []NotificationPeerErr {
+	errs := make([]NotificationPeerErr, len(sys.peerRPCClientMap))
 	var wg sync.WaitGroup
+	idx := 0
 	for addr, client := range sys.peerRPCClientMap {
 		wg.Add(1)
-		go func(addr xnet.Host, client *PeerRPCClient) {
+		go func(idx int, addr xnet.Host, client *PeerRPCClient) {
 			defer wg.Done()
 			if err := client.RemoveBucketPolicy(bucketName); err != nil {
-				errors[addr] = err
+				errs[idx] = NotificationPeerErr{
+					Host: addr,
+					Err:  err,
+				}
 			}
-		}(addr, client)
+		}(idx, addr, client)
+		idx++
 	}
 	wg.Wait()
 
-	return errors
+	return errs
 }
 
 // PutBucketNotification - calls PutBucketNotification RPC call on all peers.
-func (sys *NotificationSys) PutBucketNotification(bucketName string, rulesMap event.RulesMap) map[xnet.Host]error {
-	errors := make(map[xnet.Host]error)
+func (sys *NotificationSys) PutBucketNotification(bucketName string, rulesMap event.RulesMap) []NotificationPeerErr {
+	errs := make([]NotificationPeerErr, len(sys.peerRPCClientMap))
 	var wg sync.WaitGroup
+	idx := 0
 	for addr, client := range sys.peerRPCClientMap {
 		wg.Add(1)
-		go func(addr xnet.Host, client *PeerRPCClient, rulesMap event.RulesMap) {
+		go func(idx int, addr xnet.Host, client *PeerRPCClient, rulesMap event.RulesMap) {
 			defer wg.Done()
 			if err := client.PutBucketNotification(bucketName, rulesMap); err != nil {
-				errors[addr] = err
+				errs[idx] = NotificationPeerErr{
+					Host: addr,
+					Err:  err,
+				}
 			}
-		}(addr, client, rulesMap.Clone())
+		}(idx, addr, client, rulesMap.Clone())
+		idx++
 	}
 	wg.Wait()
 
-	return errors
+	return errs
 }
 
 // ListenBucketNotification - calls ListenBucketNotification RPC call on all peers.
-func (sys *NotificationSys) ListenBucketNotification(bucketName string, eventNames []event.Name, pattern string, targetID event.TargetID, localPeer xnet.Host) map[xnet.Host]error {
-	errors := make(map[xnet.Host]error)
+func (sys *NotificationSys) ListenBucketNotification(bucketName string, eventNames []event.Name, pattern string,
+	targetID event.TargetID, localPeer xnet.Host) []NotificationPeerErr {
+	errs := make([]NotificationPeerErr, len(sys.peerRPCClientMap))
 	var wg sync.WaitGroup
+	idx := 0
 	for addr, client := range sys.peerRPCClientMap {
 		wg.Add(1)
-		go func(addr xnet.Host, client *PeerRPCClient) {
+		go func(idx int, addr xnet.Host, client *PeerRPCClient) {
 			defer wg.Done()
 			if err := client.ListenBucketNotification(bucketName, eventNames, pattern, targetID, localPeer); err != nil {
-				errors[addr] = err
+				errs[idx] = NotificationPeerErr{
+					Host: addr,
+					Err:  err,
+				}
 			}
-		}(addr, client)
+		}(idx, addr, client)
+		idx++
 	}
 	wg.Wait()
 
-	return errors
+	return errs
 }
 
 // AddRemoteTarget - adds event rules map, HTTP/PeerRPC client target to bucket name.