fix engine selection and feature start/stop

arangod/RestServer/arangod.cpp

@@ -183,7 +183,7 @@ static int runServer(int argc, char** argv) {
 
   // storage engines
   server.addFeature(new MMFilesEngine(&server));
-  //server.addFeature(new RocksDBEngine(&server));
+  server.addFeature(new RocksDBEngine(&server));
 
   try {
     server.run(argc, argv);

arangod/StorageEngine/EngineSelectorFeature.cpp

@@ -56,7 +56,7 @@ void EngineSelectorFeature::prepare() {
 
     if (engine == _engine) {
       // this is the selected engine
-      LOG_TOPIC(TRACE, Logger::STARTUP) << "enabling storage engine " << engine;
+      LOG_TOPIC(TRACE, Logger::STARTUP) << "using storage engine " << engine;
       e->enable();
 
       // register storage engine
@@ -79,7 +79,6 @@ void EngineSelectorFeature::unprepare() {
 // return all available storage engines
 std::unordered_set<std::string> EngineSelectorFeature::availableEngines() { 
   return std::unordered_set<std::string>{
-    MMFilesEngine::EngineName
+    MMFilesEngine::EngineName, RocksDBEngine::EngineName 
-    // MMFilesEngine::EngineName, RocksDBEngine::EngineName 
   };
 }

arangod/StorageEngine/RocksDBEngine.cpp

@@ -52,7 +52,6 @@ std::string const RocksDBEngine::EngineName("RocksDB");
 // create the storage engine
 RocksDBEngine::RocksDBEngine(application_features::ApplicationServer* server)
     : StorageEngine(server, EngineName) {
-  TRI_ASSERT(false);
 }
 
 RocksDBEngine::~RocksDBEngine() {

arangod/VocBase/RevisionCacheChunkAllocator.cpp

@@ -73,6 +73,7 @@ void RevisionCacheChunkAllocator::startGcThread() {
 }
  
 void RevisionCacheChunkAllocator::stopGcThread() { 
+  _gcThread->beginShutdown();
   while (_gcThread->isRunning()) {
     usleep(10000);
   }

lib/ApplicationFeatures/ApplicationServer.cpp

@@ -522,6 +522,10 @@ void ApplicationServer::start() {
   bool abortStartup = false;
 
   for (auto feature : _orderedFeatures) {
+    if (!feature->isEnabled()) {
+      continue;
+    }
+
     LOG_TOPIC(TRACE, Logger::STARTUP) << feature->name() << "::start";
 
     try {
@@ -543,6 +547,9 @@ void ApplicationServer::start() {
       for (auto it = _orderedFeatures.rbegin(); it != _orderedFeatures.rend();
            ++it) {
         auto feature = *it;
+        if (!feature->isEnabled()) {
+          continue;
+        }
         if (feature->state() == FeatureState::STARTED) {
           LOG(TRACE) << "forcefully stopping feature '" << feature->name() << "'";
           try {
@@ -579,6 +586,9 @@ void ApplicationServer::stop() {
   for (auto it = _orderedFeatures.rbegin(); it != _orderedFeatures.rend();
        ++it) {
     auto feature = *it;
+    if (!feature->isEnabled()) {
+      continue;
+    }
 
     LOG_TOPIC(TRACE, Logger::STARTUP) << feature->name() << "::stop";
     feature->stop();