move TS dns lookup into the worker thread

simgear/scene/tsync/terrasync.cxx

@@ -201,6 +201,7 @@ struct TerrasyncThreadState
     TerrasyncThreadState() :
         _busy(false),
         _stalled(false),
+        _hasServer(false),
         _fail_count(0),
         _updated_tile_count(0),
         _success_count(0),
@@ -214,6 +215,7 @@ struct TerrasyncThreadState
 
     bool _busy;
     bool _stalled;
+    bool _hasServer;
     int  _fail_count;
     int  _updated_tile_count;
     int  _success_count;
@@ -224,7 +226,6 @@ struct TerrasyncThreadState
     // kbytes, not bytes, because bytes might overflow 2^31
     int _total_kb_downloaded;
     unsigned int _totalKbPending;
-
 };
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -257,6 +258,20 @@ public:
         return _state._stalled;
     }
 
+    bool hasServer()
+    {
+        SGGuard<SGMutex> g(_stateLock);
+        return _state._hasServer;
+    }
+
+    bool hasServer( bool flag )
+    {
+        SGGuard<SGMutex> g(_stateLock);
+        return (_state._hasServer = flag);
+    }
+
+    bool findServer();
+
     void request(const SyncItem& dir) {waitingTiles.push_front(dir);}
 
     bool hasNewTiles()
@@ -269,6 +284,7 @@ public:
    void   setHTTPServer(const std::string& server)
    {
       _httpServer = stripPath(server);
+      _isAutomaticServer = (server == "automatic");
    }
 
    void setDNSDN( const std::string & dn )
@@ -348,6 +364,7 @@ private:
     string _local_dir;
     SGPath _persistentCachePath;
     string _httpServer;
+    bool _isAutomaticServer;
     SGPath _installRoot;
     string _sceneryVersion;
     string _protocol;
@@ -359,7 +376,8 @@ private:
 
 SGTerraSync::WorkerThread::WorkerThread() :
     _stop(false),
-    _running(false)
+    _running(false),
+    _isAutomaticServer(true)
 {
     _http.setUserAgent("terrascenery-" SG_STRINGIZE(SIMGEAR_VERSION));
 }
@@ -422,14 +440,10 @@ bool SGTerraSync::WorkerThread::start()
     _stop = false;
     _state = TerrasyncThreadState(); // clean state
 
-    string status = "Using built-in HTTP support.";
-
     // not really an alert - but we want to (always) see this message, so user is
     // aware we're downloading scenery (and using bandwidth).
     SG_LOG(SG_TERRASYNC,SG_ALERT,
-           "Starting automatic scenery download/synchronization. "
+           "Starting automatic scenery download/synchronization to '"<< _local_dir << "'.");
-           << status
-           << "Directory: '" << _local_dir << "'.");
 
     SGThread::start();
     return true;
@@ -441,16 +455,9 @@ static inline string MakeQService(string & protocol, string & version )
     return protocol + "+" + version;
 }
 
-void SGTerraSync::WorkerThread::run()
+bool SGTerraSync::WorkerThread::findServer()
 {
-    {
+    if ( false == _isAutomaticServer ) return true;
-         SGGuard<SGMutex> g(_stateLock);
-        _running = true;
-    }
-
-    initCompletedTilesPersistentCache();
-
-    if (_httpServer == "automatic" ) {
 
     DNS::NAPTRRequest * naptrRequest = new DNS::NAPTRRequest(_dnsdn);
     naptrRequest->qservice = MakeQService(_protocol, _sceneryVersion);
@@ -460,13 +467,15 @@ void SGTerraSync::WorkerThread::run()
 
     DNS::Client dnsClient;
     dnsClient.makeRequest(r);
+    SG_LOG(SG_TERRASYNC,SG_DEBUG,"DNS NAPTR query for '" << _dnsdn << "' '" << naptrRequest->qservice << "'" );
     while( !r->isComplete() && !r->isTimeout() )
       dnsClient.update(0);
 
     if( naptrRequest->entries.empty() ) {
-            SG_LOG(SG_TERRASYNC, SG_ALERT, "ERROR: automatic terrasync http-server requested, but no DNS entry found.");
+        SG_LOG(SG_TERRASYNC, SG_ALERT, "Warning: no DNS entry found for '" << _dnsdn << "' '" << naptrRequest->qservice << "'" );
         _httpServer = "";
-        } else {
+        return false;
+    }
     // walk through responses, they are ordered by 1. order and 2. preference
     // For now, only take entries with lowest order
     // TODO: try all available servers in the order given by preferenc and order
@@ -505,15 +514,17 @@ void SGTerraSync::WorkerThread::run()
     _httpServer = _httpServer.substr( 6, _httpServer.length()-7 ); // strip search pattern and separators
 
     SG_LOG(SG_TERRASYNC,SG_INFO, "picking entry # " << idx << ", server is " << _httpServer );
-        }
+    return true;
+}
+
+void SGTerraSync::WorkerThread::run()
+{
+    {
+         SGGuard<SGMutex> g(_stateLock);
+        _running = true;
     }
 
-    if (_httpServer.empty()) {
+    initCompletedTilesPersistentCache();
-        SG_LOG(SG_TERRASYNC, SG_ALERT, "ERROR: no http-server found, terrasync will be disabled");
-        SGGuard<SGMutex> g(_stateLock);
-        _running = false;
-        return;
-    }
 
     runInternal();
 
@@ -521,7 +532,6 @@ void SGTerraSync::WorkerThread::run()
         SGGuard<SGMutex> g(_stateLock);
         _running = false;
     }
-
 }
 
 void SGTerraSync::WorkerThread::updateSyncSlot(SyncSlot &slot)
@@ -607,7 +617,22 @@ void SGTerraSync::WorkerThread::updateSyncSlot(SyncSlot &slot)
 
 void SGTerraSync::WorkerThread::runInternal()
 {
+    unsigned dnsRetryCount = 0;
+
     while (!_stop) {
+        // try to find a terrasync server
+        if( !hasServer() ) {
+          if( ++dnsRetryCount > 5 ) {
+            SG_LOG(SG_TERRASYNC, SG_WARN, "Can't find a terrasync server. TS disabled.");
+            break;
+          }
+          if( hasServer( findServer() ) ) {
+            SG_LOG(SG_TERRASYNC, SG_INFO, "terrasync scenery provider of the day is '" << _httpServer << "'");
+          }
+          continue;
+        }
+        dnsRetryCount = 0;
+
         try {
             _http.update(10);
         } catch (sg_exception& e) {
@@ -861,7 +886,7 @@ void SGTerraSync::reinit()
 
     if (_terraRoot->getBoolValue("enabled",false))
     {
-        _workerThread->setHTTPServer( _terraRoot->getStringValue("http-server","") );
+        _workerThread->setHTTPServer( _terraRoot->getStringValue("http-server","automatic") );
         _workerThread->setSceneryVersion( _terraRoot->getStringValue("scenery-version","ws20") );
         _workerThread->setProtocol( _terraRoot->getStringValue("protocol","") );
 #if 1