From 381049acb3d0393c7b52f3e31ccbf7498927799f Mon Sep 17 00:00:00 2001
From: Andrew Meadows <andrew@highfidelity.io>
Date: Tue, 2 Feb 2016 14:28:59 -0800
Subject: [PATCH] clear simulation ownership when owners vanish

---
 .../entities/src/SimpleEntitySimulation.cpp   | 44 ++++++++++++-------
 .../entities/src/SimpleEntitySimulation.h     |  1 +
 2 files changed, 29 insertions(+), 16 deletions(-)

diff --git a/libraries/entities/src/SimpleEntitySimulation.cpp b/libraries/entities/src/SimpleEntitySimulation.cpp
index 120b536161..f0461abb97 100644
--- a/libraries/entities/src/SimpleEntitySimulation.cpp
+++ b/libraries/entities/src/SimpleEntitySimulation.cpp
@@ -15,34 +15,46 @@
 #include "SimpleEntitySimulation.h"
 #include "EntitiesLogging.h"
 
-const quint64 AUTO_REMOVE_SIMULATION_OWNER_USEC = 2 * USECS_PER_SECOND;
+const quint64 MIN_SIMULATION_OWNERSHIP_UPDATE_PERIOD = 2 * USECS_PER_SECOND;
 
 void SimpleEntitySimulation::updateEntitiesInternal(const quint64& now) {
-    // If an Entity has a simulation owner and we don't get an update for some amount of time,
-    // clear the owner.  This guards against an interface failing to release the Entity when it
-    // has finished simulating it.
-    auto nodeList = DependencyManager::get<LimitedNodeList>();
+    if (_entitiesWithSimulator.size() == 0) {
+        return;
+    }
+
+    if (now < _nextSimulationExpiry) {
+        // nothing has expired yet
+        return;
+    }
+
+    // If an Entity has a simulation owner but there has been no update for a while: clear the owner.
+    // If an Entity goes ownerless for too long: zero velocity and remove from _entitiesWithSimulator.
+    _nextSimulationExpiry = now + MIN_SIMULATION_OWNERSHIP_UPDATE_PERIOD;
 
     QMutexLocker lock(&_mutex);
     SetOfEntities::iterator itemItr = _entitiesWithSimulator.begin();
     while (itemItr != _entitiesWithSimulator.end()) {
         EntityItemPointer entity = *itemItr;
-        if (entity->getSimulatorID().isNull()) {
-            itemItr = _entitiesWithSimulator.erase(itemItr);
-        } else if (now - entity->getLastChangedOnServer() >= AUTO_REMOVE_SIMULATION_OWNER_USEC) {
-            SharedNodePointer ownerNode = nodeList->nodeWithUUID(entity->getSimulatorID());
-            if (ownerNode.isNull() || !ownerNode->isAlive()) {
-                qCDebug(entities) << "auto-removing simulation owner" << entity->getSimulatorID();
-                entity->clearSimulationOwnership();
-                itemItr = _entitiesWithSimulator.erase(itemItr);
+        quint64 expiry = entity->getLastChangedOnServer() + MIN_SIMULATION_OWNERSHIP_UPDATE_PERIOD;
+        if (expiry < now) {
+            if (entity->getSimulatorID().isNull()) {
+                // no simulators are volunteering
                 // zero the velocity on this entity so that it doesn't drift far away
                 entity->setVelocity(glm::vec3(0.0f));
+                // remove from list
+                itemItr = _entitiesWithSimulator.erase(itemItr);
+                continue;
             } else {
-                ++itemItr;
+                // the simulator has stopped updating this object
+                // clear ownership and restart timer, giving nearby simulators time to volunteer
+                qCDebug(entities) << "auto-removing simulation owner " << entity.getSimulatorID();
+                entity->clearSimulationOwnership();
+                entity->markAsChangedOnServer();
             }
-        } else {
-            ++itemItr;
+        } else if (expiry < _nextSimulationExpiry) {
+            _nextSimulationExpiry = expiry;
         }
+        ++itemItr;
     }
 }
 
diff --git a/libraries/entities/src/SimpleEntitySimulation.h b/libraries/entities/src/SimpleEntitySimulation.h
index 83c51525a8..53a7574bf2 100644
--- a/libraries/entities/src/SimpleEntitySimulation.h
+++ b/libraries/entities/src/SimpleEntitySimulation.h
@@ -29,6 +29,7 @@ protected:
     virtual void clearEntitiesInternal() override;
 
     SetOfEntities _entitiesWithSimulator;
+    quint64 _nextSimulationExpiry { 0 };
 };
 
 #endif // hifi_SimpleEntitySimulation_h