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[release-24.0] vtorc: fix data race in forgetAliases cache initialization (#19843) #19847

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Merged
mattlord merged 1 commit into from
Apr 14, 2026
Merged

[release-24.0] vtorc: fix data race in forgetAliases cache initialization (#19843) #19847

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25 changes: 16 additions & 9 deletions go/vt/vtorc/inst/instance_dao.go
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Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,6 @@ import (
"strconv"
"strings"
"sync"
"sync/atomic"
"time"

"github.com/patrickmn/go-cache"
Expand Down Expand Up @@ -54,31 +53,37 @@ var (
instanceWriteSem = semaphore.NewWeighted(config.GetBackendWriteConcurrency())
)

var forgetAliases *cache.Cache
var (
forgetAliases *cache.Cache
forgetAliasesOnce sync.Once
)

var (
readTopologyInstanceCounter = stats.NewCounter("InstanceReadTopology", "Number of times an instance was read from the topology")
readInstanceCounter = stats.NewCounter("InstanceRead", "Number of times an instance was read")
currentErrantGTIDCount = stats.NewGaugesWithSingleLabel("CurrentErrantGTIDCount", "Number of errant GTIDs a vttablet currently has", "TabletAlias")
)

var (
emptyQuotesRegexp = regexp.MustCompile(`^""$`)
cacheInitializationCompleted atomic.Bool
)
var emptyQuotesRegexp = regexp.MustCompile(`^""$`)

func init() {
go initializeInstanceDao()
}

func initializeInstanceDao() {
config.WaitForConfigurationToBeLoaded()
InitializeForgetAliasesCache()
initForgetAliasesCache()
}

func initForgetAliasesCache() {
forgetAliasesOnce.Do(func() {
forgetAliases = cache.New(config.GetInstancePollTime()*3, time.Second)
})
}

// InitializeForgetAliasesCache ensures the forgetAliases cache is initialized.
func InitializeForgetAliasesCache() {
forgetAliases = cache.New(config.GetInstancePollTime()*3, time.Second)
cacheInitializationCompleted.Store(true)
initForgetAliasesCache()
}

// ExecDBWriteFunc chooses how to execute a write onto the database: whether synchronously or not
Expand Down Expand Up @@ -1105,6 +1110,7 @@ func UpdateInstanceLastAttemptedCheck(tabletAlias *topodatapb.TabletAlias) error

// InstanceIsForgotten returns true if an instance was forgotten.
func InstanceIsForgotten(tabletAlias *topodatapb.TabletAlias) bool {
initForgetAliasesCache()
tabletAliasString := topoproto.TabletAliasString(tabletAlias)
_, found := forgetAliases.Get(tabletAliasString)
return found
Expand All @@ -1118,6 +1124,7 @@ func ForgetInstance(tabletAlias *topodatapb.TabletAlias) error {
log.Error(errMsg)
return errors.New(errMsg)
}
initForgetAliasesCache()
tabletAliasString := topoproto.TabletAliasString(tabletAlias)
forgetAliases.Set(tabletAliasString, true, cache.DefaultExpiration)
log.Info(fmt.Sprintf("Forgetting: %v", tabletAliasString))
Expand Down
19 changes: 4 additions & 15 deletions go/vt/vtorc/inst/instance_dao_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -558,8 +558,8 @@ func TestReadOutdatedInstances(t *testing.T) {
},
}

// wait for the forgetAliases cache to be initialized to prevent data race.
waitForCacheInitialization()
// Ensure the forgetAliases cache is initialized before overriding it.
InitializeForgetAliasesCache()

// We are setting InstancePollSeconds to 59 minutes, just for the test.
oldVal := config.GetInstancePollTime()
Expand Down Expand Up @@ -747,8 +747,8 @@ func TestForgetInstanceAndInstanceIsForgotten(t *testing.T) {
},
}

// wait for the forgetAliases cache to be initialized to prevent data race.
waitForCacheInitialization()
// Ensure the forgetAliases cache is initialized before overriding it.
InitializeForgetAliasesCache()

oldCache := forgetAliases
// Clear the database after the test. The easiest way to do that is to run all the initialization commands again.
Expand Down Expand Up @@ -810,17 +810,6 @@ func TestSnapshotTopologies(t *testing.T) {
require.Equal(t, []string{"zone1-0000000100", "zone1-0000000101", "zone1-0000000112", "zone2-0000000200"}, tabletAliases)
}

// waitForCacheInitialization waits for the cache to be initialized to prevent data race in tests
// that alter the cache or depend on its behaviour.
func waitForCacheInitialization() {
for {
if cacheInitializationCompleted.Load() {
return
}
time.Sleep(100 * time.Millisecond)
}
}

func TestGetDatabaseState(t *testing.T) {
// Clear the database after the test. The easiest way to do that is to run all the initialization commands again.
defer func() {
Expand Down
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