feat: 为执行后端增加独立容量池

internal/assignmentqueue/jetstream.go

@@ -57,6 +57,11 @@ type Claims interface {
 	WaitClaimed(context.Context, string) error
 }
 
+type Admission interface {
+	Acquire(string) bool
+	Release(string)
+}
+
 // Message is the subset of jetstream.Msg needed by one reconciliation.
 type Message interface {
 	Data() []byte
@@ -70,13 +75,14 @@ type Processor struct {
 	TrustDomain  string
 	Accepter     Accepter
 	Claims       Claims
+	Admission    Admission
 	RetryDelay   time.Duration
 	ClaimTimeout time.Duration
 }
 
 func (p Processor) Process(ctx context.Context, message Message) error {
-	if p.Accepter == nil || p.Claims == nil {
-		return errors.New("assignment accepter and claim registry are required")
+	if p.Accepter == nil || p.Claims == nil || p.Admission == nil {
+		return errors.New("assignment accepter, claim registry, and backend admission pool are required")
 	}
 	assignment, err := taskassignment.Unmarshal(message.Data(), p.TrustDomain)
 	if err != nil {
@@ -85,8 +91,16 @@ func (p Processor) Process(ctx context.Context, message Message) error {
 	if _, err := p.Claims.Offer(assignment); err != nil {
 		return errors.Join(err, message.TermWithReason("conflicting assignment"))
 	}
+	if !p.Admission.Acquire(assignment.ID) {
+		delay := p.RetryDelay
+		if delay <= 0 {
+			delay = 2 * time.Second
+		}
+		return message.NakWithDelay(delay)
+	}
 	accepted, err := p.Accepter.Accept(ctx, assignment)
 	if err != nil {
+		p.Admission.Release(assignment.ID)
 		delay := p.RetryDelay
 		if delay <= 0 {
 			delay = 15 * time.Second