Ensure handling for specialization failure in pool manager (#2788)

* Add fixes for failure in specialization
* reduce specialization in progress and remove expired requests from queue when specialization is timed out
* rename markSpecializationFailure and remove logger from the queue
* refactor clean up code in api.go and add test case for queue

Details:

- Cleanup svc waiting for the counter in the pool manager if specialization fails
- Cleanup active requests counter in pool manager if client exists the demand for function service while we have allocated function service
- Consider specialization timeout if pod ready timeout > specialization timeout in waiting for ready pod. We also consider if the request to choosePod is cancelled.
- We ensure if we have requests waiting for service requests but if there is no pod in the specialization we clean up those.
---------

Signed-off-by: Sanket Sudake <sanketsudake@gmail.com>
Co-authored-by: Pranoy Kundu <pranoy1998k@gmail.com>

pkg/executor/fscache/queue.go

@@ -38,6 +38,31 @@ func (q *Queue) Pop() *svcWait {
 	return svcWait
 }
 
+func (q *Queue) Expired() int {
+	q.mutex.Lock()
+	defer q.mutex.Unlock()
+
+	expired := 0
+	svcExpired := []*list.Element{}
+	for item := q.items.Front(); item != nil; item = item.Next() {
+		svcWait, ok := item.Value.(*svcWait)
+		if !ok {
+			continue
+		}
+		if svcWait.ctx.Err() != nil {
+			close(svcWait.svcChannel)
+			svcExpired = append(svcExpired, item)
+			expired = expired + 1
+		}
+	}
+
+	for _, item := range svcExpired {
+		q.items.Remove(item)
+	}
+
+	return expired
+}
+
 func (q *Queue) Len() int {
 	q.mutex.Lock()
 	defer q.mutex.Unlock()