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subscriber.go
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subscriber.go
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package subscriber
import (
"context"
"errors"
"fmt"
"sync"
"time"
"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/rpc/client"
"github.com/nspcc-dev/neo-go/pkg/rpc/response"
"github.com/nspcc-dev/neo-go/pkg/util"
"go.uber.org/zap"
)
type (
// Subscriber is an interface of the NotificationEvent listener.
Subscriber interface {
SubscribeForNotification(...util.Uint160) (<-chan *state.NotificationEvent, error)
UnsubscribeForNotification()
BlockNotifications() (<-chan *block.Block, error)
SubscribeForNotaryRequests(mainTXSigner util.Uint160) (<-chan *response.NotaryRequestEvent, error)
Close()
}
subscriber struct {
*sync.RWMutex
log *zap.Logger
client *client.WSClient
notifyChan chan *state.NotificationEvent
notifyIDs map[util.Uint160]string
blockChan chan *block.Block
notaryChan chan *response.NotaryRequestEvent
}
// Params is a group of Subscriber constructor parameters.
Params struct {
Log *zap.Logger
Endpoint string
DialTimeout time.Duration
StartFromBlock uint32
}
)
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")
)
func (s *subscriber) SubscribeForNotification(contracts ...util.Uint160) (<-chan *state.NotificationEvent, error) {
s.Lock()
defer s.Unlock()
notifyIDs := make(map[util.Uint160]string, len(contracts))
for i := range contracts {
// do not subscribe to already subscribed contracts
if _, ok := s.notifyIDs[contracts[i]]; ok {
continue
}
// subscribe to contract notifications
id, err := s.client.SubscribeForExecutionNotifications(&contracts[i], nil)
if err != nil {
// if there is some error, undo all subscriptions and return error
for _, id := range notifyIDs {
_ = s.client.Unsubscribe(id)
}
return nil, err
}
// save notification id
notifyIDs[contracts[i]] = id
}
// update global map of subscribed contracts
for contract, id := range notifyIDs {
s.notifyIDs[contract] = id
}
return s.notifyChan, nil
}
func (s *subscriber) UnsubscribeForNotification() {
s.Lock()
defer s.Unlock()
for i := range s.notifyIDs {
err := s.client.Unsubscribe(s.notifyIDs[i])
if err != nil {
s.log.Error("unsubscribe for notification",
zap.String("event", s.notifyIDs[i]),
zap.Error(err))
}
delete(s.notifyIDs, i)
}
}
func (s *subscriber) Close() {
s.client.Close()
}
func (s *subscriber) BlockNotifications() (<-chan *block.Block, error) {
if _, err := s.client.SubscribeForNewBlocks(nil); err != nil {
return nil, fmt.Errorf("could not subscribe for new block events: %w", err)
}
return s.blockChan, nil
}
func (s *subscriber) SubscribeForNotaryRequests(mainTXSigner util.Uint160) (<-chan *response.NotaryRequestEvent, error) {
if _, err := s.client.SubscribeForNotaryRequests(nil, &mainTXSigner); err != nil {
return nil, fmt.Errorf("could not subscribe for notary request events: %w", err)
}
return s.notaryChan, nil
}
func (s *subscriber) routeNotifications(ctx context.Context) {
for {
select {
case <-ctx.Done():
return
case notification, ok := <-s.client.Notifications:
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 response.NotificationEventID:
notification, ok := notification.Value.(*state.NotificationEvent)
if !ok {
s.log.Error("can't cast notify event value to the notify struct")
continue
}
s.notifyChan <- notification
case response.BlockEventID:
b, ok := notification.Value.(*block.Block)
if !ok {
s.log.Error("can't cast block event value to block")
continue
}
s.blockChan <- b
case response.NotaryRequestEventID:
notaryRequest, ok := notification.Value.(*response.NotaryRequestEvent)
if !ok {
s.log.Error("can't cast notify event value to the notary request struct")
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
}
wsClient, err := client.NewWS(ctx, p.Endpoint, client.Options{
DialTimeout: p.DialTimeout,
})
if err != nil {
return nil, err
}
if err := wsClient.Init(); err != nil {
return nil, fmt.Errorf("could not init ws client: %w", err)
}
p.Log.Debug("event subscriber awaits RPC node",
zap.String("endpoint", p.Endpoint),
zap.Uint32("min_block_height", p.StartFromBlock))
err = awaitHeight(wsClient, p.StartFromBlock)
if err != nil {
return nil, err
}
sub := &subscriber{
RWMutex: new(sync.RWMutex),
log: p.Log,
client: wsClient,
notifyChan: make(chan *state.NotificationEvent),
notifyIDs: make(map[util.Uint160]string),
blockChan: make(chan *block.Block),
notaryChan: make(chan *response.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
// NeoFS nodes.
func awaitHeight(wsClient *client.WSClient, startFrom uint32) error {
if startFrom == 0 {
return nil
}
height, err := wsClient.GetBlockCount()
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
}