fix threading problems in arangoimp

arangosh/Import/ImportHelper.cpp

@@ -168,6 +168,19 @@ ImportHelper::ImportHelper(ClientFeature const* client,
     _senderThreads.emplace_back(new SenderThread(std::move(http), &_stats));
     _senderThreads.back()->start();
   }
+ 
+  // wait until all sender threads are ready 
+  while (true) {
+    uint32_t numReady = 0;
+    for (auto const& t : _senderThreads) {
+      if (t->isReady()) {
+        numReady++;
+      }
+    }
+    if (numReady == _senderThreads.size()) {
+      break;
+    }
+  }
 }
 
 ImportHelper::~ImportHelper() {
@@ -821,7 +834,7 @@ SenderThread* ImportHelper::findSender() {
         _hasError = true;
         _errorMessage = t->errorMessage();
         return nullptr;
-      } else if (t->idle()) {
+      } else if (t->isIdle()) {
         return t.get();
       }
     }
@@ -834,7 +847,7 @@ void ImportHelper::waitForSenders() {
   while (!_senderThreads.empty()) {
     uint32_t numIdle = 0;
     for (auto const& t : _senderThreads) {
-      if (t->idle() || t->hasError()) {
+      if (t->isDone()) {
         numIdle++;
       }
     }

arangosh/Import/SenderThread.cpp

@@ -46,6 +46,7 @@ SenderThread::SenderThread(
       _data(TRI_UNKNOWN_MEM_ZONE, false),
       _hasError(false),
       _idle(true),
+      _ready(false),
       _stats(stats) {}
 
 SenderThread::~SenderThread() {
@@ -73,31 +74,52 @@ void SenderThread::sendData(std::string const& url,
   guard.broadcast();
 }
 
+bool SenderThread::hasError() {
+  CONDITION_LOCKER(guard, _condition);
+  return _hasError;
+}
+
+bool SenderThread::isReady() {
+  CONDITION_LOCKER(guard, _condition);
+  return _ready;
+}
+
+bool SenderThread::isIdle() {
+  CONDITION_LOCKER(guard, _condition);
+  return _idle;
+}
+
+bool SenderThread::isDone() {
+  CONDITION_LOCKER(guard, _condition);
+  return _idle || _hasError;
+}
+
 void SenderThread::run() {
   while (!isStopping() && !_hasError) {
     {
       CONDITION_LOCKER(guard, _condition);
-      guard.wait();
+      _ready = true;
+      if (_idle) {
+        guard.wait();
+      }
     }
     if (isStopping()) {
-      CONDITION_LOCKER(guard, _condition);
-      _idle = true;
-      return;
+      break;
     }
     try {
       if (_data.length() > 0) {
         TRI_ASSERT(!_idle && !_url.empty());
 
-        std::unordered_map<std::string, std::string> headerFields;
         std::unique_ptr<httpclient::SimpleHttpResult> result(
             _client->request(rest::RequestType::POST, _url, _data.c_str(),
-                             _data.length(), headerFields));
+                             _data.length()));
 
         handleResult(result.get());
 
         _url.clear();
         _data.reset();
       }
+
       CONDITION_LOCKER(guard, _condition);
       _idle = true;
     } catch (...) {
@@ -106,6 +128,9 @@ void SenderThread::run() {
       _idle = true;
     }
   }
+    
+  CONDITION_LOCKER(guard, _condition);
+  TRI_ASSERT(_idle);
 }
 
 void SenderThread::handleResult(httpclient::SimpleHttpResult* result) {

arangosh/Import/SenderThread.h

@@ -57,9 +57,10 @@ class SenderThread : public arangodb::Thread {
 
   void sendData(std::string const& url, basics::StringBuffer* sender);
 
-  bool idle() const { return _idle; }
-
-  bool hasError() const { return _hasError; }
+  bool hasError();
+  bool isReady();
+  bool isIdle();
+  bool isDone();
 
   std::string const& errorMessage() const { return _errorMessage; }
 
@@ -73,8 +74,9 @@ class SenderThread : public arangodb::Thread {
   httpclient::SimpleHttpClient* _client;
   std::string _url;
   basics::StringBuffer _data;
-  bool _hasError = false;
-  bool _idle = true;
+  bool _hasError;
+  bool _idle;
+  bool _ready;
 
   ImportStatistics* _stats;
   std::string _errorMessage;