fix(offlinegate): fix data race in offlinegate EE-2713 (#6626)

api/go.mod

@@ -37,6 +37,7 @@ require (
 	github.com/robfig/cron/v3 v3.0.1
 	github.com/sirupsen/logrus v1.8.1
 	github.com/stretchr/testify v1.7.0
+	github.com/viney-shih/go-lock v1.1.1
 	go.etcd.io/bbolt v1.3.6
 	golang.org/x/crypto v0.0.0-20220307211146-efcb8507fb70
 	golang.org/x/oauth2 v0.0.0-20200107190931-bf48bf16ab8d

api/go.sum

@@ -718,6 +718,8 @@ github.com/urfave/cli v0.0.0-20171014202726-7bc6a0acffa5/go.mod h1:70zkFmudgCuE/
 github.com/urfave/cli v1.20.0/go.mod h1:70zkFmudgCuE/ngEzBv17Jvp/497gISqfk5gWijbERA=
 github.com/urfave/cli v1.22.1/go.mod h1:Gos4lmkARVdJ6EkW0WaNv/tZAAMe9V7XWyB60NtXRu0=
 github.com/urfave/cli v1.22.2/go.mod h1:Gos4lmkARVdJ6EkW0WaNv/tZAAMe9V7XWyB60NtXRu0=
+github.com/viney-shih/go-lock v1.1.1 h1:SwzDPPAiHpcwGCr5k8xD15d2gQSo8d4roRYd7TDV2eI=
+github.com/viney-shih/go-lock v1.1.1/go.mod h1:Yijm78Ljteb3kRiJrbLAxVntkUukGu5uzSxq/xV7OO8=
 github.com/vishvananda/netlink v0.0.0-20181108222139-023a6dafdcdf/go.mod h1:+SR5DhBJrl6ZM7CoCKvpw5BKroDKQ+PJqOg65H/2ktk=
 github.com/vishvananda/netlink v1.1.0/go.mod h1:cTgwzPIzzgDAYoQrMm0EdrjRUBkTqKYppBueQtXaqoE=
 github.com/vishvananda/netlink v1.1.1-0.20201029203352-d40f9887b852/go.mod h1:twkDnbuQxJYemMlGd4JFIcuhgX83tXhKS2B/PRMpOho=
@@ -860,6 +862,7 @@ golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4/go.mod h1:RxMgew5VJxzue5/jJ
 golang.org/x/sync v0.0.0-20190227155943-e225da77a7e6/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20200317015054-43a5402ce75a/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20200625203802-6e8e738ad208/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20201207232520-09787c993a3a/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=

api/http/offlinegate/offlinegate.go

@@ -3,69 +3,48 @@ package offlinegate
 import (
 	"log"
 	"net/http"
-	"sync"
+	"strings"
 	"time"
 
 	httperror "github.com/portainer/libhttp/error"
+	lock "github.com/viney-shih/go-lock"
 )
 
-// OfflineGate is a entity that works similar to a mutex with a signaling
+// OfflineGate is an entity that works similar to a mutex with signaling
-// Only the caller that have Locked an gate can unlock it, otherw will be blocked with a call to Lock.
+// Only the caller that has Locked a gate can unlock it, otherwise it will be blocked with a call to Lock.
 // Gate provides a passthrough http middleware that will wait for a locked gate to be unlocked.
-// For a safety reasons, middleware will timeout
+// For safety reasons, the middleware will timeout
 type OfflineGate struct {
-	lock        *sync.Mutex
+	lock *lock.CASMutex
-	signalingCh chan interface{}
 }
 
 // NewOfflineGate creates a new gate
 func NewOfflineGate() *OfflineGate {
 	return &OfflineGate{
-		lock: &sync.Mutex{},
+		lock: lock.NewCASMutex(),
 	}
 }
 
 // Lock locks readonly gate and returns a function to unlock
 func (o *OfflineGate) Lock() func() {
 	o.lock.Lock()
-	o.signalingCh = make(chan interface{})
+	return o.lock.Unlock
-	return o.unlock
-}
-
-func (o *OfflineGate) unlock() {
-	if o.signalingCh == nil {
-		return
-	}
-
-	close(o.signalingCh)
-	o.signalingCh = nil
-	o.lock.Unlock()
-}
-
-// Watch returns a signaling channel.
-// Unless channel is nil, client needs to watch for a signal on a channel to know when gate is unlocked.
-// Signal channel is disposable: onced signaled, has to be disposed and acquired again.
-func (o *OfflineGate) Watch() chan interface{} {
-	return o.signalingCh
 }
 
 // WaitingMiddleware returns an http handler that waits for the gate to be unlocked before continuing
 func (o *OfflineGate) WaitingMiddleware(timeout time.Duration, next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		signalingCh := o.Watch()
+		if r.Method == "GET" || r.Method == "HEAD" || r.Method == "OPTIONS" || strings.HasPrefix(r.URL.Path, "/api/backup") || strings.HasPrefix(r.URL.Path, "/api/restore") {
+			next.ServeHTTP(w, r)
+			return
+		}
 
-		if signalingCh != nil {
+		if !o.lock.RTryLockWithTimeout(timeout) {
-			if r.Method != "GET" && r.Method != "HEAD" && r.Method != "OPTIONS" {
-				select {
-				case <-signalingCh:
-				case <-time.After(timeout):
 			log.Println("error: Timeout waiting for the offline gate to signal")
 			httperror.WriteError(w, http.StatusRequestTimeout, "Timeout waiting for the offline gate to signal", http.ErrHandlerTimeout)
+			return
 		}
-			}
-		}
-
 		next.ServeHTTP(w, r)
-
+		o.lock.RUnlock()
 	})
 }

api/http/offlinegate/offlinegate_test.go

@@ -58,77 +58,6 @@ func Test_hasToBeUnlockedToLockAgain(t *testing.T) {
 
 }
 
-func Test_waitChannelWillBeEmpty_ifGateIsUnlocked(t *testing.T) {
-	o := NewOfflineGate()
-
-	signalingCh := o.Watch()
-	if signalingCh != nil {
-		t.Error("Signaling channel should be empty")
-	}
-}
-
-func Test_startWaitingForSignal_beforeGateGetsUnlocked(t *testing.T) {
-	// scenario:
-	// 1. main routing locks the gate and waits for a consumer to start up
-	// 2. consumer starts up, notifies main and begins waiting for the gate to be unlocked
-	// 3. main unlocks the gate
-	// 4. consumer be able to continue
-
-	o := NewOfflineGate()
-	unlock := o.Lock()
-
-	signalingCh := o.Watch()
-
-	wg := sync.WaitGroup{}
-	wg.Add(1)
-	readerIsReady := sync.WaitGroup{}
-	readerIsReady.Add(1)
-
-	go func(t *testing.T) {
-		readerIsReady.Done()
-
-		// either wait for a signal or timeout
-		select {
-		case <-signalingCh:
-		case <-time.After(10 * time.Second):
-			t.Error("Failed to wait for a signal, exit by timeout")
-		}
-		wg.Done()
-	}(t)
-
-	readerIsReady.Wait()
-	unlock()
-
-	wg.Wait()
-}
-
-func Test_startWaitingForSignal_afterGateGetsUnlocked(t *testing.T) {
-	// scenario:
-	// 1. main routing locks, gets waiting channel and unlocks
-	// 2. consumer starts up and begins waiting for the gate to be unlocked
-	// 3. consumer gets signal immediately and continues
-
-	o := NewOfflineGate()
-	unlock := o.Lock()
-	signalingCh := o.Watch()
-	unlock()
-
-	wg := sync.WaitGroup{}
-	wg.Add(1)
-
-	go func(t *testing.T) {
-		// either wait for a signal or timeout
-		select {
-		case <-signalingCh:
-		case <-time.After(10 * time.Second):
-			t.Error("Failed to wait for a signal, exit by timeout")
-		}
-		wg.Done()
-	}(t)
-
-	wg.Wait()
-}
-
 func Test_waitingMiddleware_executesImmediately_whenNotLocked(t *testing.T) {
 	// scenario:
 	// 1. create an gate