For the same zone, delay sync until icinga::Hello tells remote capabilities

They'll become important for teamwork in a zone.

Author: Al2Klimov

lib/remote/apilistener.cpp

@@ -852,11 +852,24 @@ void ApiListener::NewClientHandlerInternal(
 		JsonRpcConnection::Ptr aclient = new JsonRpcConnection(identity, verify_ok, client, role);
 
 		if (endpoint) {
-			endpoint->AddClient(aclient);
+			static const auto reuniteCluster ([](const JsonRpcConnection::Ptr& aclient) {
+				auto endpoint (aclient->GetEndpoint());
 
-			Utility::QueueAsyncCallback([this, aclient, endpoint]() {
-				SyncClient(aclient, endpoint, true);
+				endpoint->AddClient(aclient);
+
+				Utility::QueueAsyncCallback([this, aclient, endpoint] {
+					SyncClient(aclient, endpoint, true);
+				});
 			});
+
+			if (endpoint->GetZone() == Zone::GetLocalZone()) {
+				// Nodes in the same zone, which do teamwork, must know each other's capabilities in advance.
+				// Hence, we delay everything else until they're told us via an icinga::Hello message.
+				// Even v2.12 nodes send this message at the beginning, so we're safe.
+				aclient->OnNextHello.connect(reuniteCluster);
+			} else {
+				reuniteCluster(aclient);
+			}
 		} else if (!AddAnonymousClient(aclient)) {
 			Log(LogNotice, "ApiListener")
 				<< "Ignoring anonymous JSON-RPC connection " << conninfo