[FIXED] Fix request/reply performance when using allow_responses perms (

#6064)

Fixes performance issues noted in #6058. Attempts to prune reply map
every `replyPermLimit` messages or if it has been more than
`replyPruneTime` since the last prune.

Resolves #6058 

Signed-off-by: Jack Morris <jack@jackmorris.me>

server/client.go

@@ -262,6 +262,9 @@ type client struct {
 	last       time.Time
 	lastIn     time.Time
 
+	repliesSincePrune uint16
+	lastReplyPrune    time.Time
+
 	headers bool
 
 	rtt      time.Duration
@@ -422,6 +425,7 @@ const (
 	pruneSize            = 32
 	routeTargetInit      = 8
 	replyPermLimit       = 4096
+	replyPruneTime       = time.Second
 )
 
 // Represent read cache booleans with a bitmask
@@ -3634,9 +3638,11 @@ func (c *client) deliverMsg(prodIsMQTT bool, sub *subscription, acc *Account, su
 
 	// If we are tracking dynamic publish permissions that track reply subjects,
 	// do that accounting here. We only look at client.replies which will be non-nil.
-	if client.replies != nil && len(reply) > 0 {
+	// Only reply subject permissions if the client is not already allowed to publish to the reply subject.
+	if client.replies != nil && len(reply) > 0 && !client.pubAllowedFullCheck(string(reply), true, true) {
 		client.replies[string(reply)] = &resp{time.Now(), 0}
-		if len(client.replies) > replyPermLimit {
+		client.repliesSincePrune++
+		if client.repliesSincePrune > replyPermLimit || time.Since(client.lastReplyPrune) > replyPruneTime {
 			client.pruneReplyPerms()
 		}
 	}
@@ -3760,6 +3766,9 @@ func (c *client) pruneReplyPerms() {
 			delete(c.replies, k)
 		}
 	}
+
+	c.repliesSincePrune = 0
+	c.lastReplyPrune = now
 }
 
 // pruneDenyCache will prune the deny cache via randomly
@@ -3828,7 +3837,7 @@ func (c *client) pubAllowedFullCheck(subject string, fullCheck, hasLock bool) bo
 		allowed = np == 0
 	}
 
-	// If we are currently not allowed but we are tracking reply subjects
+	// If we are tracking reply subjects
 	// dynamically, check to see if we are allowed here but avoid pcache.
 	// We need to acquire the lock though.
 	if !allowed && fullCheck && c.perms.resp != nil {