Retry subscription if no new events (#131)

* fix: resubscribe to ws if not responding

internal/clients/bbnclient/bbnclient.go

@@ -4,6 +4,8 @@ import (
 	"context"
 	"fmt"
 	"strings"
+	"sync"
+	"time"
 
 	"github.com/avast/retry-go/v4"
 	"github.com/babylonlabs-io/babylon-staking-indexer/internal/config"
@@ -16,6 +18,7 @@ import (
 )
 
 type BBNClient struct {
+	wg          sync.WaitGroup
 	queryClient *query.QueryClient
 	cfg         *config.BBNConfig
 }
@@ -30,7 +33,10 @@ func NewBBNClient(cfg *config.BBNConfig) BbnInterface {
 	if err != nil {
 		log.Fatal().Err(err).Msg("error while creating BBN query client")
 	}
-	return &BBNClient{queryClient, cfg}
+	return &BBNClient{
+		queryClient: queryClient,
+		cfg:         cfg,
+	}
 }
 
 func (c *BBNClient) GetLatestBlockNumber(ctx context.Context) (int64, error) {
@@ -140,8 +146,86 @@ func (c *BBNClient) GetBlock(ctx context.Context, blockHeight *int64) (*ctypes.R
 	return block, nil
 }
 
-func (c *BBNClient) Subscribe(subscriber, query string, outCapacity ...int) (out <-chan ctypes.ResultEvent, err error) {
-	return c.queryClient.RPCClient.Subscribe(context.Background(), subscriber, query, outCapacity...)
+func (c *BBNClient) Subscribe(
+	subscriber, query string,
+	healthCheckInterval time.Duration,
+	maxEventWaitInterval time.Duration,
+	outCapacity ...int,
+) (out <-chan ctypes.ResultEvent, err error) {
+	eventChan := make(chan ctypes.ResultEvent)
+
+	subscribe := func() (<-chan ctypes.ResultEvent, error) {
+		newChan, err := c.queryClient.RPCClient.Subscribe(
+			context.Background(),
+			subscriber,
+			query,
+			outCapacity...,
+		)
+		if err != nil {
+			return nil, fmt.Errorf(
+				"failed to subscribe babylon events for query %s: %w", query, err,
+			)
+		}
+		return newChan, nil
+	}
+
+	// Initial subscription
+	rawEventChan, err := subscribe()
+	if err != nil {
+		close(eventChan)
+		return nil, err
+	}
+	c.wg.Add(1)
+	go func() {
+		defer c.wg.Done()
+		defer close(eventChan)
+		timeoutTicker := time.NewTicker(healthCheckInterval)
+		defer timeoutTicker.Stop()
+		lastEventTime := time.Now()
+
+		for {
+			select {
+			case event, ok := <-rawEventChan:
+				if !ok {
+					log.Fatal().
+						Str("subscriber", subscriber).
+						Str("query", query).
+						Msg("Subscription channel closed, this shall not happen")
+				}
+				lastEventTime = time.Now()
+				eventChan <- event
+			case <-timeoutTicker.C:
+				if time.Since(lastEventTime) > maxEventWaitInterval {
+					log.Error().
+						Str("subscriber", subscriber).
+						Str("query", query).
+						Msg("No events received, attempting to resubscribe")
+
+					if err := c.queryClient.RPCClient.Unsubscribe(
+						context.Background(),
+						subscriber,
+						query,
+					); err != nil {
+						log.Error().Err(err).Msg("Failed to unsubscribe babylon events")
+					}
+
+					// Create new subscription
+					newEventChan, err := subscribe()
+					if err != nil {
+						log.Error().Err(err).Msg("Failed to resubscribe babylon events")
+						continue
+					}
+
+					// Replace the old channel with the new one
+					rawEventChan = newEventChan
+					// reset last event time
+					lastEventTime = time.Now()
+				}
+			}
+		}
+	}()
+
+	return eventChan, nil
 }
 
 func (c *BBNClient) UnsubscribeAll(subscriber string) error {

internal/clients/bbnclient/interface.go

@@ -2,6 +2,7 @@ package bbnclient
 
 import (
 	"context"
+	"time"
 
 	ctypes "github.com/cometbft/cometbft/rpc/core/types"
 )
@@ -13,7 +14,12 @@ type BbnInterface interface {
 	GetLatestBlockNumber(ctx context.Context) (int64, error)
 	GetBlock(ctx context.Context, blockHeight *int64) (*ctypes.ResultBlock, error)
 	GetBlockResults(ctx context.Context, blockHeight *int64) (*ctypes.ResultBlockResults, error)
-	Subscribe(subscriber, query string, outCapacity ...int) (out <-chan ctypes.ResultEvent, err error)
+	Subscribe(
+		subscriber, query string,
+		healthCheckInterval time.Duration,
+		maxEventWaitInterval time.Duration,
+		outCapacity ...int,
+	) (out <-chan ctypes.ResultEvent, err error)
 	UnsubscribeAll(subscriber string) error
 	IsRunning() bool
 	Start() error

internal/services/subscription.go

@@ -2,23 +2,38 @@ package services
 
 import (
 	"context"
+	"time"
 
 	"github.com/babylonlabs-io/babylon-staking-indexer/internal/types"
 	ctypes "github.com/cometbft/cometbft/types"
 	"github.com/rs/zerolog/log"
 )
 
 const (
-	subscriberName = "babylon-staking-indexer"
-	newBlockQuery  = "tm.event='NewBlock'"
+	subscriberName                  = "babylon-staking-indexer"
+	newBlockQuery                   = "tm.event='NewBlock'"
+	outCapacity                     = 100
+	subscriptionHealthCheckInterval = 1 * time.Minute
+	maxEventWaitInterval            = 1 * time.Minute
 )
 
 func (s *Service) SubscribeToBbnEvents(ctx context.Context) {
 	if !s.bbn.IsRunning() {
 		log.Fatal().Msg("BBN client is not running")
 	}
-
-	eventChan, err := s.bbn.Subscribe(subscriberName, newBlockQuery)
+	// Subscribe to new block events but only wait for 5 minutes for events
+	// if nothing come through within 5 minutes, the underlying subscription will
+	// be resubscribed.
+	// This is a workaround for the fact that cometbft ws_client does not have
+	// proper ping pong configuration setup to detect if the connection is dead.
+	// Refer to https://github.com/cometbft/cometbft/commit/2fd8496bc109d010c6c2e415604131b500550e37#r151452099
+	eventChan, err := s.bbn.Subscribe(
+		subscriberName,
+		newBlockQuery,
+		subscriptionHealthCheckInterval,
+		maxEventWaitInterval,
+		outCapacity,
+	)
 	if err != nil {
 		log.Fatal().Msgf("Failed to subscribe to events: %v", err)
 	}
@@ -36,11 +51,15 @@ func (s *Service) SubscribeToBbnEvents(ctx context.Context) {
 				if latestHeight == 0 {
 					log.Fatal().Msg("Event doesn't contain block height information")
 				}
+				log.Debug().
+					Int64("height", latestHeight).
+					Msg("received new block event from babylon subscription")
 
 				// Send the latest height to the BBN block processor
 				s.latestHeightChan <- latestHeight
 
 			case <-ctx.Done():
+				log.Info().Msg("context done, unsubscribing all babylon events")
 				err := s.bbn.UnsubscribeAll(subscriberName)
 				if err != nil {
 					log.Error().Msgf("Failed to unsubscribe from events: %v", err)