fix collector inactivity in shutdown

arangod/RestServer/DatabaseFeature.cpp

@@ -348,6 +348,12 @@ void DatabaseFeature::start() {
   updateContexts();
 }
 
+void DatabaseFeature::stop() {
+  auto logfileManager = arangodb::wal::LogfileManager::instance();
+  logfileManager->flush(true, true, false);
+  logfileManager->waitForCollector();
+}
+
 void DatabaseFeature::unprepare() {
   // close all databases
   closeDatabases();

arangod/RestServer/DatabaseFeature.h

@@ -73,6 +73,7 @@ class DatabaseFeature final : public application_features::ApplicationFeature {
   void validateOptions(std::shared_ptr<options::ProgramOptions>) override final;
   void prepare() override final;
   void start() override final;
+  void stop() override final;
   void unprepare() override final;
 
   int recoveryDone();

arangod/Wal/LogfileManager.cpp

@@ -442,6 +442,9 @@ bool LogfileManager::open() {
   return true;
 }
     
+void LogfileManager::stop() {
+}
+
 void LogfileManager::unprepare() {
   _shutdown = 1;
 
@@ -1612,6 +1615,17 @@ void LogfileManager::removeLogfile(Logfile* logfile) {
   }
 }
 
+void LogfileManager::waitForCollector() {
+  if (_collectorThread == nullptr) {
+    return;
+  }
+
+  while (_collectorThread->hasQueuedOperations()) {
+    LOG(TRACE) << "waiting for WAL collector";
+    usleep(50000);
+  }
+}
+
 // wait until a specific logfile has been collected
 int LogfileManager::waitForCollector(Logfile::IdType logfileId,
                                      double maxWaitTime) {
@@ -1885,7 +1899,10 @@ int LogfileManager::startCollectorThread() {
 
 // stop the collector thread
 void LogfileManager::stopCollectorThread() {
-  if (_collectorThread != nullptr) {
+  if (_collectorThread == nullptr) {
+    return;
+  }
+
   LOG(TRACE) << "stopping WAL collector thread";
 
   // wait for at most 5 seconds for the collector 
@@ -1922,7 +1939,6 @@ void LogfileManager::stopCollectorThread() {
 
   _collectorThread->beginShutdown();
 }
-}
 
 // start the remover thread
 int LogfileManager::startRemoverThread() {

arangod/Wal/LogfileManager.h

@@ -114,6 +114,7 @@ class LogfileManager final : public application_features::ApplicationFeature {
   void validateOptions(std::shared_ptr<options::ProgramOptions>) override final;
   void prepare() override final;
   void start() override final;
+  void stop() override final;
   void unprepare() override final;
 
  public:
@@ -372,6 +373,8 @@ class LogfileManager final : public application_features::ApplicationFeature {
   // get information about running transactions
   std::tuple<size_t, Logfile::IdType, Logfile::IdType> runningTransactions();
   
+  void waitForCollector();
+
  private:
   // memcpy the data into the WAL region and return the filled slot
   // to the WAL logfile manager