2 files changed, 21 insertions, 5 deletions
diff --git a/src/main/java/org/traccar/session/ConnectionManager.java b/src/main/java/org/traccar/session/ConnectionManager.java
index 05c4893fd..fe6521d18 100644
--- a/src/main/java/org/traccar/session/ConnectionManager.java
+++ b/src/main/java/org/traccar/session/ConnectionManager.java
@@ -144,7 +144,10 @@ public class ConnectionManager {
             endpointSessions.put(device.getUniqueId(), deviceSession);
             sessionsByEndpoint.put(endpoint, endpointSessions);
             sessionsByDeviceId.put(device.getId(), deviceSession);
-            cacheManager.addDevice(device.getId());
+
+            if (oldSession == null) {
+                cacheManager.addDevice(device.getId());
+            }
 
             return deviceSession;
         } else {
@@ -190,8 +193,8 @@ public class ConnectionManager {
     public void deviceUnknown(long deviceId) {
         updateDevice(deviceId, Device.STATUS_UNKNOWN, null);
         DeviceSession deviceSession = sessionsByDeviceId.remove(deviceId);
-        cacheManager.removeDevice(deviceId);
         if (deviceSession != null) {
+            cacheManager.removeDevice(deviceId);
             Endpoint endpoint = new Endpoint(deviceSession.getChannel(), deviceSession.getRemoteAddress());
             sessionsByEndpoint.computeIfPresent(endpoint, (e, sessions) -> {
                 sessions.remove(deviceSession.getUniqueId());
diff --git a/src/main/java/org/traccar/session/cache/CacheManager.java b/src/main/java/org/traccar/session/cache/CacheManager.java
index 87384f746..abc8ca4c9 100644
--- a/src/main/java/org/traccar/session/cache/CacheManager.java
+++ b/src/main/java/org/traccar/session/cache/CacheManager.java
@@ -60,6 +60,7 @@ public class CacheManager {
     private final ReadWriteLock lock = new ReentrantReadWriteLock();
 
     private final Map<CacheKey, CacheValue> deviceCache = new HashMap<>();
+    private final Map<Long, Integer> deviceReferences = new HashMap<>();
     private final Map<Long, Map<Class<? extends BaseModel>, List<Long>>> deviceLinks = new HashMap<>();
     private final Map<Long, Position> devicePositions = new HashMap<>();
 
@@ -136,9 +137,14 @@ public class CacheManager {
     public void addDevice(long deviceId) throws StorageException {
         try {
             lock.writeLock().lock();
-            if (!deviceLinks.containsKey(deviceId)) {
+            Integer references = deviceReferences.get(deviceId);
+            if (references != null) {
+                references += 1;
+            } else {
                 unsafeAddDevice(deviceId);
+                references = 1;
             }
+            deviceReferences.put(deviceId, references);
         } finally {
             lock.writeLock().unlock();
         }
@@ -147,8 +153,15 @@ public class CacheManager {
     public void removeDevice(long deviceId) {
         try {
             lock.writeLock().lock();
-            if (deviceLinks.containsKey(deviceId)) {
-                unsafeRemoveDevice(deviceId);
+            Integer references = deviceReferences.get(deviceId);
+            if (references != null) {
+                references -= 1;
+                if (references <= 0) {
+                    unsafeRemoveDevice(deviceId);
+                    deviceReferences.remove(deviceId);
+                } else {
+                    deviceReferences.put(deviceId, references);
+                }
             }
         } finally {
             lock.writeLock().unlock();