reynoldsm88
diff --git a/‎CHANGELOG
Lines changed: 2 additions & 0 deletions b/‎CHANGELOG
Lines changed: 2 additions & 0 deletions
diff --git a/‎arangod/Cluster/ClusterInfo.cpp
Lines changed: 40 additions & 6 deletions b/‎arangod/Cluster/ClusterInfo.cpp
Lines changed: 40 additions & 6 deletions
diff --git a/‎tests/IResearch/AgencyMock.cpp
Lines changed: 8 additions & 5 deletions b/‎tests/IResearch/AgencyMock.cpp
Lines changed: 8 additions & 5 deletions
@@ -1,6 +1,8 @@
 devel
 -----
 
+* fix timeout-response in case of simultaneous index create/drop in cluster
+
 * allow pregel to select the shard key via `shardKeyAttribute` in pregel start parameters
 
 * Added --server.jwt-secret-keyfile to arangosh.
 
@@ -2751,10 +2751,11 @@ Result ClusterInfo::ensureIndexCoordinatorInner(  // create index
   }
 
   // will contain the error number and message
-  auto dbServerResult = std::make_shared<std::atomic<int>>(-1);
+  std::atomic<int> dbServerResult(-1);
   std::shared_ptr<std::string> errMsg = std::make_shared<std::string>();
 
-  std::function<bool(VPackSlice const& result)> dbServerChanged = [=](VPackSlice const& result) {
+  std::function<bool(VPackSlice const& result)> dbServerChanged = [=, &dbServerResult](
+                                                                      VPackSlice const& result) {
     if (!result.isObject() || result.length() != numberOfShards) {
       return true;
     }
@@ -2786,7 +2787,7 @@ Result ClusterInfo::ensureIndexCoordinatorInner(  // create index
             // error otherwise
             int errNum = arangodb::basics::VelocyPackHelper::readNumericValue<int>(
                 v, StaticStrings::ErrorNum, TRI_ERROR_ARANGO_INDEX_CREATION_FAILED);
-            dbServerResult->store(errNum, std::memory_order_release);
+            dbServerResult.store(errNum, std::memory_order_release);
             return true;
           }
 
@@ -2797,7 +2798,7 @@ Result ClusterInfo::ensureIndexCoordinatorInner(  // create index
     }
 
     if (found == (size_t)numberOfShards) {
-      dbServerResult->store(setErrormsg(TRI_ERROR_NO_ERROR, *errMsg), std::memory_order_release);
+      dbServerResult.store(setErrormsg(TRI_ERROR_NO_ERROR, *errMsg), std::memory_order_release);
     }
 
     return true;
@@ -2828,12 +2829,12 @@ Result ClusterInfo::ensureIndexCoordinatorInner(  // create index
   // by a mutex. We use the mutex of the condition variable in the
   // AgencyCallback for this.
   std::string where = "Current/Collections/" + databaseName + "/" + collectionID;
-
   auto agencyCallback =
       std::make_shared<AgencyCallback>(ac, where, dbServerChanged, true, false);
   _agencyCallbackRegistry->registerCallback(agencyCallback);
   auto cbGuard = scopeGuard(
       [&] { _agencyCallbackRegistry->unregisterCallback(agencyCallback); });
+
   AgencyOperation newValue(planIndexesKey, AgencyValueOperationType::PUSH,
                            newIndexBuilder.slice());
   AgencyOperation incrementVersion("Plan/Version", AgencySimpleOperationType::INCREMENT_OP);
@@ -2878,7 +2879,40 @@ Result ClusterInfo::ensureIndexCoordinatorInner(  // create index
 
   {
     while (!application_features::ApplicationServer::isStopping()) {
-      int tmpRes = dbServerResult->load(std::memory_order_acquire);
+      int tmpRes = dbServerResult.load(std::memory_order_acquire);
+
+      if (tmpRes < 0) {
+        // index has not shown up in Current yet,  follow up check to
+        // ensure it is still in plan (not dropped between iterations)
+
+        AgencyCommResult result = _agency.sendTransactionWithFailover(
+            AgencyReadTransaction(AgencyCommManager::path(planIndexesKey)));
+
+        if (result.successful()) {
+          auto indexes = result.slice()[0].get(
+              std::vector<std::string>{AgencyCommManager::path(), "Plan",
+                                       "Collections", databaseName,
+                                       collectionID, "indexes"});
+
+          bool found = false;
+          if (indexes.isArray()) {
+            for (auto const& v : VPackArrayIterator(indexes)) {
+              VPackSlice const k = v.get(StaticStrings::IndexId);
+              if (k.isString() && k.isEqualString(idString)) {
+                // index is still here
+                found = true;
+                break;
+              }
+            }
+          }
+
+          if (!found) {
+            return Result(TRI_ERROR_ARANGO_INDEX_CREATION_FAILED,
+                          "index was dropped during creation");
+          }
+        }
+      }
+
       if (tmpRes == 0) {
         // Finally, in case all is good, remove the `isBuilding` flag
         // check that the index has appeared. Note that we have to have
 
@@ -35,6 +35,13 @@
 namespace arangodb {
 namespace consensus {
 
+// FIXME TODO this implementation causes deadlock when unregistering a callback,
+//            if there is still another callback registered; it's not obvious
+//            how to fix this, as it seems the problem is that both "agents"
+//            live on the same server and share an AgencyCallbackRegistry
+//            instance; we could solve this if we could have two
+//            ApplicationServers in the same instance, but too many things in
+//            the feature stack are static still to make the changes right now
 // FIXME TODO for some reason the implementation of this function is missing in the arangodb code
 void Store::notifyObservers() const {
   auto* clusterFeature =
@@ -79,11 +86,7 @@ void Store::notifyObservers() const {
 
   for (auto& id: callbackIds) {
     try {
-      auto& condition = callbackRegistry->getCallback(id)->_cv;
-      CONDITION_LOCKER(locker, condition);
-
-      callbackRegistry->getCallback(id)->refetchAndUpdate(false, true); // force a check
-      condition.signal();
     } catch(...) {
       // ignore
     }