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fix: atomic.Value should be a concrete type to avoid panics (#13740)

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Go's atomic.Value does not support `nil` type,
concrete type is necessary to avoid any panics with
the current implementation.

Also remove boolean to turn-off tracking of freezeCount.
This commit is contained in:
Harshavardhana 2021-11-23 16:09:28 -08:00 committed by GitHub
parent 91e0823ff0
commit 9ca25bd48f
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 19 additions and 38 deletions
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2
cmd/handler-api.go
View File

@ -228,7 +228,7 @@ func (t *apiConfig) getRequestsPool() (chan struct{}, time.Duration) {
func maxClients(f http.HandlerFunc) http.HandlerFunc { func maxClients(f http.HandlerFunc) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) { return func(w http.ResponseWriter, r *http.Request) {
if val := globalServiceFreeze.Load(); val != nil { if val := globalServiceFreeze.Load(); val != nil {
if unlock, ok := val.(chan struct{}); ok { if unlock, ok := val.(chan struct{}); ok && unlock != nil {
// Wait until unfrozen. // Wait until unfrozen.
<-unlock <-unlock
} }

55
cmd/service.go
View File

@ -68,56 +68,37 @@ func restartProcess() error {
return syscall.Exec(argv0, os.Args, os.Environ()) return syscall.Exec(argv0, os.Args, os.Environ())
} }
// Keep track of number of freeze/unfreeze calls.
const trackFreezeCount = true
// freezeServices will freeze all incoming S3 API calls. // freezeServices will freeze all incoming S3 API calls.
// For each call, unfreezeServices must be called once. // For each call, unfreezeServices must be called once.
func freezeServices() { func freezeServices() {
// Use atomics for globalServiceFreeze, so we can read without locking. // Use atomics for globalServiceFreeze, so we can read without locking.
if trackFreezeCount { // We need a lock since we are need the 2 atomic values to remain in sync.
// We need a lock since we are need the 2 atomic values to remain in sync. globalServiceFreezeMu.Lock()
globalServiceFreezeMu.Lock() // If multiple calls, first one creates channel.
// If multiple calls, first one creates channel. globalServiceFreezeCnt++
globalServiceFreezeCnt++ if globalServiceFreezeCnt == 1 {
if globalServiceFreezeCnt == 1 { globalServiceFreeze.Store(make(chan struct{}))
globalServiceFreeze.Store(make(chan struct{}))
}
globalServiceFreezeMu.Unlock()
} else {
// If multiple calls, first one creates channel.
globalServiceFreeze.CompareAndSwap(nil, make(chan struct{}))
} }
globalServiceFreezeMu.Unlock()
} }
// unfreezeServices will unfreeze all incoming S3 API calls. // unfreezeServices will unfreeze all incoming S3 API calls.
// For each call, unfreezeServices must be called once. // For each call, unfreezeServices must be called once.
func unfreezeServices() { func unfreezeServices() {
if trackFreezeCount { // We need a lock since we need the 2 atomic values to remain in sync.
// We need a lock since we need the 2 atomic values to remain in sync. globalServiceFreezeMu.Lock()
globalServiceFreezeMu.Lock() // Close when we reach 0
// Close when we reach 0 globalServiceFreezeCnt--
globalServiceFreezeCnt-- if globalServiceFreezeCnt <= 0 {
if globalServiceFreezeCnt <= 0 { // Ensure we only close once.
// Ensure we only close once.
if val := globalServiceFreeze.Load(); val != nil {
if ch, ok := val.(chan struct{}); ok {
globalServiceFreeze.Store(nil)
close(ch)
}
}
globalServiceFreezeCnt = 0 // Don't risk going negative.
}
globalServiceFreezeMu.Unlock()
} else {
// If multiple calls, first one closes channel.
if val := globalServiceFreeze.Load(); val != nil { if val := globalServiceFreeze.Load(); val != nil {
var _ch chan struct{}
if ch, ok := val.(chan struct{}); ok { if ch, ok := val.(chan struct{}); ok {
// Ensure we only close once. globalServiceFreeze.Store(_ch)
if globalServiceFreeze.CompareAndSwap(val, nil) { close(ch)
close(ch)
}
} }
} }
globalServiceFreezeCnt = 0 // Don't risk going negative.
} }
globalServiceFreezeMu.Unlock()
} }