chore(swe): prevent stale reads (#96)

references
[issue](#86)

CHANGELOG.md

@@ -38,6 +38,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 ## Unreleased
 
 * [#94](https://github.com/babylonlabs-io/vigilante/pull/94) adds gosec and fixes gosec issues
+* [#96](https://github.com/babylonlabs-io/vigilante/pull/96) fixes potential stale data read
 
 ## v0.15.0
 

btcstaking-tracker/stakingeventwatcher/stakingeventwatcher.go

@@ -580,12 +580,7 @@ func (sew *StakingEventWatcher) handlerVerifiedDelegations() {
 // checkBtcForStakingTx gets a snapshot of current Delegations in cache
 // checks if staking tx is in BTC, generates a proof and invokes sending of MsgAddBTCDelegationInclusionProof
 func (sew *StakingEventWatcher) checkBtcForStakingTx() error {
-	delegations := sew.pendingTracker.GetDelegations()
-	if delegations == nil {
-		return nil
-	}
-
-	for _, del := range delegations {
+	for del := range sew.pendingTracker.DelegationsIter() {
 		if del.ActivationInProgress {
 			continue
 		}

btcstaking-tracker/stakingeventwatcher/tracked_delegations.go

@@ -2,6 +2,7 @@ package stakingeventwatcher
 
 import (
 	"fmt"
+	"iter"
 	"sync"
 
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
@@ -58,6 +59,20 @@ func (td *TrackedDelegations) GetDelegations() []*TrackedDelegation {
 	return delegations
 }
 
+func (td *TrackedDelegations) DelegationsIter() iter.Seq[*TrackedDelegation] {
+	return func(yield func(*TrackedDelegation) bool) {
+		td.mu.RLock()
+		defer td.mu.RUnlock()
+
+		// we lock for the entirety of the iteration
+		for _, v := range td.mapping {
+			if !yield(v) {
+				return
+			}
+		}
+	}
+}
+
 func (td *TrackedDelegations) AddDelegation(
 	StakingTx *wire.MsgTx,
 	StakingOutputIdx uint32,