frostfs-node/pkg/morph/subscriber/subscriber.go
Pavel Karpy a69c6d1ec9 [] morph: Do not subscribe to events without listening
It led to a neo-go dead-lock in the `subscriber` component. Subscribing to
notifications is the same RPC as any others, so it could also be blocked
forever if no async listening (reading the notification channel) routine
exists. If a number of subscriptions is big enough (or a caller is lucky
enough) subscribing loop might have not finished subscribing before the
first notification is received and then: subscribing RPC is blocked by
received notification (non)handling and listening notifications routine is
blocked by not finished subscription loop.
That commit starts listening notification channel _before_ any subscription
actions.

Signed-off-by: Pavel Karpy <p.karpy@yadro.com>
2023-04-03 08:42:41 +00:00

241 lines
6.1 KiB
Go

package subscriber
import (
"context"
"errors"
"fmt"
"sync"
"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/morph/client"
"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
"github.com/nspcc-dev/neo-go/pkg/core/block"
"github.com/nspcc-dev/neo-go/pkg/core/state"
"github.com/nspcc-dev/neo-go/pkg/neorpc"
"github.com/nspcc-dev/neo-go/pkg/neorpc/result"
"github.com/nspcc-dev/neo-go/pkg/util"
"go.uber.org/zap"
)
type (
NotificationChannels struct {
BlockCh <-chan *block.Block
NotificationsCh <-chan *state.ContainedNotificationEvent
NotaryRequestsCh <-chan *result.NotaryRequestEvent
}
// Subscriber is an interface of the NotificationEvent listener.
Subscriber interface {
SubscribeForNotification(...util.Uint160) error
UnsubscribeForNotification()
BlockNotifications() error
SubscribeForNotaryRequests(mainTXSigner util.Uint160) error
NotificationChannels() NotificationChannels
Close()
}
subscriber struct {
*sync.RWMutex
log *logger.Logger
client *client.Client
notifyChan chan *state.ContainedNotificationEvent
blockChan chan *block.Block
notaryChan chan *result.NotaryRequestEvent
}
// Params is a group of Subscriber constructor parameters.
Params struct {
Log *logger.Logger
StartFromBlock uint32
Client *client.Client
}
)
func (s *subscriber) NotificationChannels() NotificationChannels {
return NotificationChannels{
BlockCh: s.blockChan,
NotificationsCh: s.notifyChan,
NotaryRequestsCh: s.notaryChan,
}
}
var (
errNilParams = errors.New("chain/subscriber: config was not provided to the constructor")
errNilLogger = errors.New("chain/subscriber: logger was not provided to the constructor")
errNilClient = errors.New("chain/subscriber: client was not provided to the constructor")
)
func (s *subscriber) SubscribeForNotification(contracts ...util.Uint160) error {
s.Lock()
defer s.Unlock()
notifyIDs := make(map[util.Uint160]struct{}, len(contracts))
for i := range contracts {
// subscribe to contract notifications
err := s.client.SubscribeForExecutionNotifications(contracts[i])
if err != nil {
// if there is some error, undo all subscriptions and return error
for hash := range notifyIDs {
_ = s.client.UnsubscribeContract(hash)
}
return err
}
// save notification id
notifyIDs[contracts[i]] = struct{}{}
}
return nil
}
func (s *subscriber) UnsubscribeForNotification() {
err := s.client.UnsubscribeAll()
if err != nil {
s.log.Error("unsubscribe for notification",
zap.Error(err))
}
}
func (s *subscriber) Close() {
s.client.Close()
}
func (s *subscriber) BlockNotifications() error {
if err := s.client.SubscribeForNewBlocks(); err != nil {
return fmt.Errorf("could not subscribe for new block events: %w", err)
}
return nil
}
func (s *subscriber) SubscribeForNotaryRequests(mainTXSigner util.Uint160) error {
if err := s.client.SubscribeForNotaryRequests(mainTXSigner); err != nil {
return fmt.Errorf("could not subscribe for notary request events: %w", err)
}
return nil
}
func (s *subscriber) routeNotifications(ctx context.Context) {
notificationChan := s.client.NotificationChannel()
for {
select {
case <-ctx.Done():
return
case notification, ok := <-notificationChan:
if !ok {
s.log.Warn("remote notification channel has been closed")
close(s.notifyChan)
close(s.blockChan)
close(s.notaryChan)
return
}
switch notification.Type {
case neorpc.NotificationEventID:
notifyEvent, ok := notification.Value.(*state.ContainedNotificationEvent)
if !ok {
s.log.Error("can't cast notify event value to the notify struct",
zap.String("received type", fmt.Sprintf("%T", notification.Value)),
)
continue
}
s.log.Debug("new notification event from sidechain",
zap.String("name", notifyEvent.Name),
)
s.notifyChan <- notifyEvent
case neorpc.BlockEventID:
b, ok := notification.Value.(*block.Block)
if !ok {
s.log.Error("can't cast block event value to block",
zap.String("received type", fmt.Sprintf("%T", notification.Value)),
)
continue
}
s.blockChan <- b
case neorpc.NotaryRequestEventID:
notaryRequest, ok := notification.Value.(*result.NotaryRequestEvent)
if !ok {
s.log.Error("can't cast notify event value to the notary request struct",
zap.String("received type", fmt.Sprintf("%T", notification.Value)),
)
continue
}
s.notaryChan <- notaryRequest
default:
s.log.Debug("unsupported notification from the chain",
zap.Uint8("type", uint8(notification.Type)),
)
}
}
}
}
// New is a constructs Neo:Morph event listener and returns Subscriber interface.
func New(ctx context.Context, p *Params) (Subscriber, error) {
switch {
case p == nil:
return nil, errNilParams
case p.Log == nil:
return nil, errNilLogger
case p.Client == nil:
return nil, errNilClient
}
err := awaitHeight(p.Client, p.StartFromBlock)
if err != nil {
return nil, err
}
sub := &subscriber{
RWMutex: new(sync.RWMutex),
log: p.Log,
client: p.Client,
notifyChan: make(chan *state.ContainedNotificationEvent),
blockChan: make(chan *block.Block),
notaryChan: make(chan *result.NotaryRequestEvent),
}
// Worker listens all events from neo-go websocket and puts them
// into corresponding channel. It may be notifications, transactions,
// new blocks. For now only notifications.
go sub.routeNotifications(ctx)
return sub, nil
}
// awaitHeight checks if remote client has least expected block height and
// returns error if it is not reached that height after timeout duration.
// This function is required to avoid connections to unsynced RPC nodes, because
// they can produce events from the past that should not be processed by
// FrostFS nodes.
func awaitHeight(cli *client.Client, startFrom uint32) error {
if startFrom == 0 {
return nil
}
height, err := cli.BlockCount()
if err != nil {
return fmt.Errorf("could not get block height: %w", err)
}
if height < startFrom {
return fmt.Errorf("RPC block counter %d didn't reach expected height %d", height, startFrom)
}
return nil
}