make retry/recovery optional on first subscriptions (#48218)

Author: jkarneges

examples/config/pushpin.conf

@@ -157,6 +157,9 @@ message_wait=5000
 # time (seconds) to cache message ids
 id_cache_ttl=60
 
+# retry/recover sessions soon after the first subscription to a channel
+update_on_first_subscription=true
+
 # max subscriptions per connection
 connection_subscription_max=20
 

src/handler/handlerapp.cpp

@@ -314,6 +314,7 @@ class HandlerApp::Private
 		int messageBlockSize = settings.value("handler/message_block_size", -1).toInt();
 		int messageWait = settings.value("handler/message_wait", 5000).toInt();
 		int idCacheTtl = settings.value("handler/id_cache_ttl", 0).toInt();
+		bool updateOnFirstSubscription = settings.value("handler/update_on_first_subscription", true).toBool();
 		int clientMaxconn = settings.value("runner/client_maxconn", 50000).toInt();
 		int connectionSubscriptionMax = settings.value("handler/connection_subscription_max", 20).toInt();
 		int subscriptionLinger = settings.value("handler/subscription_linger", 60).toInt();
@@ -378,6 +379,7 @@ class HandlerApp::Private
 		config.messageBlockSize = messageBlockSize;
 		config.messageWait = messageWait;
 		config.idCacheTtl = idCacheTtl;
+		config.updateOnFirstSubscription = updateOnFirstSubscription;
 		config.connectionsMax = clientMaxconn;
 		config.connectionSubscriptionMax = connectionSubscriptionMax;
 		config.subscriptionLinger = subscriptionLinger;

src/handler/handlerengine.cpp

@@ -2316,7 +2316,8 @@ class HandlerEngine::Private
 
 	void sub_subscribed(Subscription *sub)
 	{
-		updateSessions(sub->channel());
+		if(config.updateOnFirstSubscription)
+			updateSessions(sub->channel());
 	}
 
 	void acceptWorker_sessionsReady(AcceptWorker *w)

src/handler/handlerengine.h

@@ -75,6 +75,7 @@ class HandlerEngine
 		int messageBlockSize;
 		int messageWait;
 		int idCacheTtl;
+		bool updateOnFirstSubscription;
 		int connectionsMax;
 		int connectionSubscriptionMax;
 		int subscriptionLinger;
@@ -98,6 +99,7 @@ class HandlerEngine
 			messageBlockSize(-1),
 			messageWait(-1),
 			idCacheTtl(-1),
+			updateOnFirstSubscription(false),
 			connectionsMax(-1),
 			connectionSubscriptionMax(-1),
 			subscriptionLinger(-1),