diff --git a/mqtt-common/src/main/java/io/streamnative/pulsar/handlers/mqtt/common/MQTTConnectionManager.java b/mqtt-common/src/main/java/io/streamnative/pulsar/handlers/mqtt/common/MQTTConnectionManager.java
index dfe71ea62..efd7b3c53 100644
--- a/mqtt-common/src/main/java/io/streamnative/pulsar/handlers/mqtt/common/MQTTConnectionManager.java
+++ b/mqtt-common/src/main/java/io/streamnative/pulsar/handlers/mqtt/common/MQTTConnectionManager.java
@@ -21,14 +21,16 @@
 import io.streamnative.pulsar.handlers.mqtt.common.systemtopic.ConnectEvent;
 import io.streamnative.pulsar.handlers.mqtt.common.systemtopic.EventListener;
 import io.streamnative.pulsar.handlers.mqtt.common.systemtopic.MqttEvent;
-import java.util.ArrayList;
 import java.util.Collection;
+import java.util.LinkedHashSet;
+import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.TimeUnit;
 import java.util.function.Consumer;
 import lombok.Getter;
 import lombok.extern.slf4j.Slf4j;
+import org.apache.pulsar.jetcd.shaded.io.vertx.core.impl.ConcurrentHashSet;
 
 /**
  * Proxy connection manager.
@@ -38,7 +40,7 @@ public class MQTTConnectionManager {
 
     private final ConcurrentMap<String, Connection> localConnections;
 
-    private final ConcurrentMap<String, Connection> eventConnections;
+    private final ConcurrentHashSet<String> eventClientIds;
 
     @Getter
     private static final HashedWheelTimer sessionExpireInterval =
@@ -56,7 +58,7 @@ public class MQTTConnectionManager {
     public MQTTConnectionManager(String advertisedAddress) {
         this.advertisedAddress = advertisedAddress;
         this.localConnections = new ConcurrentHashMap<>(2048);
-        this.eventConnections = new ConcurrentHashMap<>(2048);
+        this.eventClientIds = new ConcurrentHashSet<>(2048);
         this.connectListener = new ConnectEventListener();
         this.disconnectListener = new DisconnectEventListener();
     }
@@ -102,11 +104,11 @@ public Collection<Connection> getLocalConnections() {
         return this.localConnections.values();
     }
 
-    public Collection<Connection> getAllConnections() {
-        Collection<Connection> connections = new ArrayList<>(this.localConnections.values().size()
-                    + this.eventConnections.values().size());
-        connections.addAll(this.localConnections.values());
-        connections.addAll(eventConnections.values());
+    public Collection<String> getAllConnectionsId() {
+        Set<String> connections = new LinkedHashSet<>(this.localConnections.keySet().size()
+                    + this.eventClientIds.size());
+        connections.addAll(this.localConnections.keySet());
+        connections.addAll(eventClientIds);
         return connections;
     }
 
@@ -126,7 +128,7 @@ public void onChange(MqttEvent event) {
                         log.warn("[ConnectEvent] close existing connection : {}", connection);
                         connection.disconnect();
                     } else {
-                        eventConnections.put(connectEvent.getClientId(), connection);
+                        eventClientIds.add(connectEvent.getClientId());
                     }
                 }
             }
@@ -141,7 +143,7 @@ public void onChange(MqttEvent event) {
             if (event.getEventType() == DISCONNECT) {
                 ConnectEvent connectEvent = (ConnectEvent) event.getSourceEvent();
                 if (!connectEvent.getAddress().equals(advertisedAddress)) {
-                    eventConnections.remove(connectEvent.getClientId());
+                    eventClientIds.remove(connectEvent.getClientId());
                 }
             }
         }
diff --git a/mqtt-common/src/main/java/io/streamnative/pulsar/handlers/mqtt/common/systemtopic/SystemTopicBasedSystemEventService.java b/mqtt-common/src/main/java/io/streamnative/pulsar/handlers/mqtt/common/systemtopic/SystemTopicBasedSystemEventService.java
index 0a836aece..f68b203ae 100644
--- a/mqtt-common/src/main/java/io/streamnative/pulsar/handlers/mqtt/common/systemtopic/SystemTopicBasedSystemEventService.java
+++ b/mqtt-common/src/main/java/io/streamnative/pulsar/handlers/mqtt/common/systemtopic/SystemTopicBasedSystemEventService.java
@@ -237,7 +237,13 @@ private void refreshCache(Message<MqttEvent> msg) {
                 default:
                     break;
             }
-            listeners.forEach(listener -> listener.onChange(value));
+            listeners.forEach(listener -> {
+                try {
+                    listener.onChange(value);
+                } catch (Throwable e) {
+                    log.error("Failed to process event : {}", value.getKey(), e);
+                }
+            });
         } catch (Throwable ex) {
             log.error("refresh cache error", ex);
         }
diff --git a/mqtt-proxy/src/main/java/io/streamnative/pulsar/handlers/mqtt/proxy/web/admin/Devices.java b/mqtt-proxy/src/main/java/io/streamnative/pulsar/handlers/mqtt/proxy/web/admin/Devices.java
index a1fb9f5ca..b1ef0bf73 100644
--- a/mqtt-proxy/src/main/java/io/streamnative/pulsar/handlers/mqtt/proxy/web/admin/Devices.java
+++ b/mqtt-proxy/src/main/java/io/streamnative/pulsar/handlers/mqtt/proxy/web/admin/Devices.java
@@ -13,13 +13,11 @@
  */
 package io.streamnative.pulsar.handlers.mqtt.proxy.web.admin;
 
-import io.streamnative.pulsar.handlers.mqtt.common.Connection;
 import io.swagger.annotations.Api;
 import io.swagger.annotations.ApiOperation;
 import io.swagger.annotations.ApiResponse;
 import io.swagger.annotations.ApiResponses;
 import java.util.Collection;
-import java.util.stream.Collectors;
 import javax.ws.rs.GET;
 import javax.ws.rs.Path;
 import javax.ws.rs.Produces;
@@ -45,9 +43,8 @@ public class Devices extends WebResource {
             @ApiResponse(code = 500, message = "Internal server error")})
     public void getList(@Suspended final AsyncResponse asyncResponse) {
         try {
-            final Collection<Connection> allConnections = service().getConnectionManager().getAllConnections();
-            asyncResponse.resume(allConnections.stream().map(e ->
-                    e.getClientId()).collect(Collectors.toList()));
+            final Collection<String> allConnections = service().getConnectionManager().getAllConnectionsId();
+            asyncResponse.resume(allConnections);
         } catch (Exception e) {
             log.error("[{}] Failed to list devices {}", clientAppId(), e);
             asyncResponse.resume(new RestException(e));