Changed behaviour of queryShutdown and querySetup; shutdown no longer

does anything if setup has not been called yet, and they are both only
called when relevant configuration changes are seen (there is always at
least one 'configuration change', the initial setup)

src/bin/resolver/resolver.cc

@@ -80,15 +80,19 @@ public:
     }
 
     void queryShutdown() {
-        dlog("Query shutdown");
-        delete rec_query_;
-        rec_query_ = NULL;
+        // only shut down if we have actually called querySetup before
+        // (this is not a safety check, just to prevent logging of
+        // actions that are not performed
+        if (rec_query_) {
+            dlog("Query shutdown");
+            delete rec_query_;
+            rec_query_ = NULL;
+        }
     }
 
     void setForwardAddresses(const vector<addr_t>& upstream,
         DNSService *dnss)
     {
-        queryShutdown();
         upstream_ = upstream;
         if (dnss) {
             if (upstream_.empty()) {
@@ -100,7 +104,6 @@ public:
                     dlog(" " + address.first + ":" +
                         boost::lexical_cast<string>(address.second));
                 }
-                querySetup(*dnss);
             }
         }
     }
@@ -327,8 +330,6 @@ Resolver::~Resolver() {
 
 void
 Resolver::setDNSService(asiolink::DNSService& dnss) {
-    impl_->queryShutdown();
-    impl_->querySetup(dnss);
     dnss_ = &dnss;
 }
 
@@ -514,14 +515,24 @@ Resolver::updateConfig(ConstElementPtr config) {
         }
         // Everything OK, so commit the changes
         // listenAddresses can fail to bind, so try them first
+        bool need_query_restart = false;
+        
         if (listenAddressesE) {
             setListenAddresses(listenAddresses);
+            need_query_restart = true;
         }
         if (forwardAddressesE) {
             setForwardAddresses(forwardAddresses);
+            need_query_restart = true;
         }
         if (set_timeouts) {
             setTimeouts(timeout, retries);
+            need_query_restart = true;
+        }
+
+        if (need_query_restart) {
+            impl_->queryShutdown();
+            impl_->querySetup(*dnss_);
         }
         return (isc::config::createAnswer());
     } catch (const isc::Exception& error) {
@@ -596,8 +607,6 @@ Resolver::setTimeouts(int timeout, unsigned retries) {
         " and retry count to " + boost::lexical_cast<string>(retries));
     impl_->timeout_ = timeout;
     impl_->retries_ = retries;
-    impl_->queryShutdown();
-    impl_->querySetup(*dnss_);
 }
 pair<int, unsigned>
 Resolver::getTimeouts() const {