diff --git a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/DistributedOpenstackNetworkStore.java b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/DistributedOpenstackNetworkStore.java
index 0cc63b9..63b4a49 100644
--- a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/DistributedOpenstackNetworkStore.java
+++ b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/DistributedOpenstackNetworkStore.java
@@ -29,7 +29,6 @@
 import org.onosproject.openstacknetworking.api.OpenstackNetworkEvent;
 import org.onosproject.openstacknetworking.api.OpenstackNetworkStore;
 import org.onosproject.openstacknetworking.api.OpenstackNetworkStoreDelegate;
-import org.onosproject.openstacknetworking.api.PreCommitPortService;
 import org.onosproject.store.AbstractStore;
 import org.onosproject.store.serializers.KryoNamespaces;
 import org.onosproject.store.service.ConsistentMap;
@@ -58,6 +57,7 @@
 
 import java.util.LinkedHashMap;
 import java.util.List;
+import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.ExecutorService;
 
@@ -93,8 +93,6 @@
     private static final String ERR_NOT_FOUND = " does not exist";
     private static final String ERR_DUPLICATE = " already exists";
 
-    private static final long TIMEOUT_MS = 2000; // wait for 2s
-
     private static final KryoNamespace SERIALIZER_NEUTRON_L2 = KryoNamespace.newBuilder()
             .register(KryoNamespaces.API)
             .register(Network.class)
@@ -122,9 +120,6 @@
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
     protected StorageService storageService;
 
-    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
-    protected PreCommitPortService preCommitPortService;
-
     private final ExecutorService eventExecutor = newSingleThreadExecutor(
             groupedThreads(this.getClass().getSimpleName(), "event-handler", log));
 
@@ -413,7 +408,7 @@
                     ImmutableList.of() : newPort.getSecurityGroups();
 
             oldSecurityGroups.stream()
-                    .filter(sgId -> !newPort.getSecurityGroups().contains(sgId))
+                    .filter(sgId -> !Objects.requireNonNull(newPort.getSecurityGroups()).contains(sgId))
                     .forEach(sgId -> notifyDelegate(new OpenstackNetworkEvent(
                             OPENSTACK_PORT_SECURITY_GROUP_REMOVED, newPort, sgId
                     )));
diff --git a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenStackSwitchingDirectPortProvider.java b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenStackSwitchingDirectPortProvider.java
index 76c0197..14e6aa1 100644
--- a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenStackSwitchingDirectPortProvider.java
+++ b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenStackSwitchingDirectPortProvider.java
@@ -311,9 +311,6 @@
             ports.forEach(port -> {
                 addIntfToDevice(node, port);
             });
-
-
-
         }
 
         private void addIntfToDevice(OpenstackNode node, Port port) {
diff --git a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackNetworkManager.java b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackNetworkManager.java
index 92257fd..1db1da1 100644
--- a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackNetworkManager.java
+++ b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackNetworkManager.java
@@ -339,7 +339,7 @@
                     osPort = osNetworkStore.ports()
                             .stream()
                             .filter(p -> p.getvNicType().equals(DIRECT) && p.getProfile().get(PCISLOT) != null)
-                            .filter(p -> getIntfNameFromPciAddress(p).equals(portName))
+                            .filter(p -> Objects.requireNonNull(getIntfNameFromPciAddress(p)).equals(portName))
                             .findFirst();
                     return osPort.orElse(null);
 
@@ -484,11 +484,11 @@
                 ByteBuffer.wrap(ethRequest.serialize())));
 
         externalPeerRouterMap.put(targetIp.toString(),
-                                    DefaultExternalPeerRouter.builder()
-                                                    .ipAddress(targetIp)
-                                                    .macAddress(MacAddress.NONE)
-                                                    .vlanId(vlanId)
-                                                    .build());
+                DefaultExternalPeerRouter.builder()
+                        .ipAddress(targetIp)
+                        .macAddress(MacAddress.NONE)
+                        .vlanId(vlanId)
+                        .build());
 
         log.info("Initializes external peer router map with peer router IP {}", targetIp.toString());
     }
@@ -641,7 +641,7 @@
 
         return subnets(network.getId()).stream()
                 .filter(s -> IpPrefix.valueOf(s.getCidr()).contains(ipAddress))
-                .map(s -> s.getGateway())
+                .map(Subnet::getGateway)
                 .findAny().orElse(null);
     }
 
@@ -704,4 +704,4 @@
 
         return externalSubnet.map(subnet -> IpAddress.valueOf(subnet.getGateway())).orElse(null);
     }
-}
+}
\ No newline at end of file
diff --git a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackRoutingIcmpHandler.java b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackRoutingIcmpHandler.java
index 764cefe..a7e008a 100644
--- a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackRoutingIcmpHandler.java
+++ b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackRoutingIcmpHandler.java
@@ -221,7 +221,6 @@
                 });
             } catch (IllegalArgumentException e) {
                 log.warn("IllegalArgumentException occurred because of {}", e.toString());
-                return;
             }
         }
     }
diff --git a/apps/openstacknetworkingui/src/main/java/org/onosproject/openstacknetworkingui/OpenstackNetworkingUiMessageHandler.java b/apps/openstacknetworkingui/src/main/java/org/onosproject/openstacknetworkingui/OpenstackNetworkingUiMessageHandler.java
index 3982d22..1dfefb8 100644
--- a/apps/openstacknetworkingui/src/main/java/org/onosproject/openstacknetworkingui/OpenstackNetworkingUiMessageHandler.java
+++ b/apps/openstacknetworkingui/src/main/java/org/onosproject/openstacknetworkingui/OpenstackNetworkingUiMessageHandler.java
@@ -168,7 +168,7 @@
             switch (mode) {
                 case MOUSE:
                     currentMode = Mode.MOUSE;
-                    eventExecutor.execute(() -> sendMouseData());
+                    eventExecutor.execute(OpenstackNetworkingUiMessageHandler.this::sendMouseData);
 
                     break;
 
@@ -195,7 +195,7 @@
                     dstIp,
                     srcDeviceId,
                     dstDeviceId);
-            eventExecutor.execute(() -> processFlowTraceRequest(srcIp, dstIp, srcDeviceId, dstDeviceId));
+            eventExecutor.execute(() -> processFlowTraceRequest(srcIp, dstIp, srcDeviceId));
         }
     }
 
@@ -211,7 +211,7 @@
             if (!Strings.isNullOrEmpty(id)) {
                 eventExecutor.execute(() -> updateForMode(id));
             } else {
-                eventExecutor.execute(() -> clearForMode());
+                eventExecutor.execute(OpenstackNetworkingUiMessageHandler.this::clearForMode);
             }
         }
     }
@@ -229,8 +229,6 @@
         }
     }
 
-    // === ------------
-
     private void clearState() {
         currentMode = Mode.IDLE;
         elementOfNote = null;
@@ -290,14 +288,13 @@
     private void sendMouseData() {
         Highlights highlights = new Highlights();
 
-        if (elementOfNote != null && elementOfNote instanceof Device) {
+        if (elementOfNote instanceof Device) {
             DeviceId deviceId = (DeviceId) elementOfNote.id();
 
             List<OpenstackLink> edgeLinks = edgeLinks(deviceId);
 
-            edgeLinks.forEach(edgeLink -> {
-                highlights.add(edgeLink.highlight(OpenstackLink.RequestType.DEVICE_SELECTED));
-            });
+            edgeLinks.forEach(edgeLink ->
+                    highlights.add(edgeLink.highlight(OpenstackLink.RequestType.DEVICE_SELECTED)));
 
             hostService.getConnectedHosts(deviceId).forEach(host -> {
                 HostHighlight hostHighlight = new HostHighlight(host.id().toString());
@@ -307,7 +304,7 @@
 
             sendHighlights(highlights);
 
-        } else if (elementOfNote != null && elementOfNote instanceof Host) {
+        } else if (elementOfNote instanceof Host) {
 
             HostId hostId = HostId.hostId(elementOfNote.id().toString());
             if (!hostMadeFromOpenstack(hostId)) {
@@ -316,9 +313,8 @@
 
             List<OpenstackLink> openstackLinks = linksInSameNetwork(hostId);
 
-            openstackLinks.forEach(openstackLink -> {
-                highlights.add(openstackLink.highlight(OpenstackLink.RequestType.HOST_SELECTED));
-            });
+            openstackLinks.forEach(openstackLink ->
+                    highlights.add(openstackLink.highlight(OpenstackLink.RequestType.HOST_SELECTED)));
 
             hostHighlightsInSameNetwork(hostId).forEach(highlights::add);
 
@@ -328,8 +324,7 @@
     }
 
     private boolean hostMadeFromOpenstack(HostId hostId) {
-        return hostService.getHost(hostId).annotations()
-                .value(ANNOTATION_NETWORK_ID) == null ? false : true;
+        return hostService.getHost(hostId).annotations().value(ANNOTATION_NETWORK_ID) != null;
     }
 
     private String networkId(HostId hostId) {
@@ -360,7 +355,7 @@
 
         List<OpenstackLink> edgeLinks = Lists.newArrayList();
 
-        openstackLinkMap.biLinks().forEach(edgeLinks::add);
+        edgeLinks.addAll(openstackLinkMap.biLinks());
 
         return edgeLinks;
     }
@@ -384,7 +379,7 @@
 
         List<OpenstackLink> openstackLinks = Lists.newArrayList();
 
-        linkMap.biLinks().forEach(openstackLinks::add);
+        openstackLinks.addAll(linkMap.biLinks());
 
         return openstackLinks;
     }
@@ -398,7 +393,7 @@
         return NodeBadge.number(Status.INFO, n, "Openstack Node");
     }
 
-    private void processFlowTraceRequest(String srcIp, String dstIp, String srcDeviceId, String dstDeviceId) {
+    private void processFlowTraceRequest(String srcIp, String dstIp, String srcDeviceId) {
         boolean traceSuccess = true;
 
         ObjectMapper mapper = new ObjectMapper();
diff --git a/apps/openstacknode/app/src/main/java/org/onosproject/openstacknode/impl/OpenstackNodeManager.java b/apps/openstacknode/app/src/main/java/org/onosproject/openstacknode/impl/OpenstackNodeManager.java
index b6a4437..ff10a2c 100644
--- a/apps/openstacknode/app/src/main/java/org/onosproject/openstacknode/impl/OpenstackNodeManager.java
+++ b/apps/openstacknode/app/src/main/java/org/onosproject/openstacknode/impl/OpenstackNodeManager.java
@@ -264,16 +264,7 @@
     public void addVfPort(OpenstackNode osNode, String portName) {
         log.trace("addVfPort called");
 
-        if (!isOvsdbConnected(osNode, ovsdbPort, ovsdbController, deviceService)) {
-            log.warn("There's no ovsdb connection with the device {}. Try to connect the device...",
-                    osNode.ovsdb().toString());
-            try {
-                ovsdbController.connect(osNode.managementIp(), tpPort(ovsdbPort));
-            } catch (Exception e) {
-                log.error("Failed to connect to the openstackNode via ovsdb protocol because of exception {}",
-                        e.toString());
-            }
-        }
+        connectSwitch(osNode);
 
         addOrRemoveSystemInterface(osNode, INTEGRATION_BRIDGE, portName, true);
     }
@@ -282,6 +273,12 @@
     public void removeVfPort(OpenstackNode osNode, String portName) {
         log.trace("removeVfPort called");
 
+        connectSwitch(osNode);
+
+        addOrRemoveSystemInterface(osNode, INTEGRATION_BRIDGE, portName, false);
+    }
+
+    private void connectSwitch(OpenstackNode osNode) {
         if (!isOvsdbConnected(osNode, ovsdbPort, ovsdbController, deviceService)) {
             log.warn("There's no ovsdb connection with the device {}. Try to connect the device...",
                     osNode.ovsdb().toString());
@@ -292,8 +289,6 @@
                         e.toString());
             }
         }
-
-        addOrRemoveSystemInterface(osNode, INTEGRATION_BRIDGE, portName, false);
     }
 
     private void addOrRemoveSystemInterface(OpenstackNode osNode, String bridgeName, String intfName,
diff --git a/apps/openstacktroubleshoot/app/src/main/java/org/onosproject/openstacktroubleshoot/impl/OpenstackTroubleshootManager.java b/apps/openstacktroubleshoot/app/src/main/java/org/onosproject/openstacktroubleshoot/impl/OpenstackTroubleshootManager.java
index 13e9579..1b1cdf8 100644
--- a/apps/openstacktroubleshoot/app/src/main/java/org/onosproject/openstacktroubleshoot/impl/OpenstackTroubleshootManager.java
+++ b/apps/openstacktroubleshoot/app/src/main/java/org/onosproject/openstacktroubleshoot/impl/OpenstackTroubleshootManager.java
@@ -44,6 +44,7 @@
 import org.onosproject.net.flow.FlowRuleService;
 import org.onosproject.net.flow.TrafficSelector;
 import org.onosproject.net.flow.TrafficTreatment;
+import org.onosproject.net.flow.criteria.Criterion;
 import org.onosproject.net.flow.criteria.IPCriterion;
 import org.onosproject.net.packet.DefaultOutboundPacket;
 import org.onosproject.net.packet.InboundPacket;
@@ -290,45 +291,21 @@
     /**
      * Checks whether east-west ICMP reply rule is added or not.
      *
-     * @param ip    IP address
+     * @param dstIp    IP address
      * @return true if ICMP reply rule is added, false otherwise
      */
-    private boolean checkEastWestIcmpReplyRule(String ip) {
-        for (FlowEntry entry : flowRuleService.getFlowEntriesById(appId)) {
-            TrafficSelector selector = entry.selector();
-
-            IPCriterion ipCriterion = (IPCriterion) selector.getCriterion(IPV4_DST);
-
-            if (ipCriterion != null &&
-                    ip.equals(ipCriterion.ip().address().toString()) &&
-                    entry.state() == ADDED) {
-                return true;
-            }
-        }
-
-        return false;
+    private boolean checkEastWestIcmpReplyRule(String dstIp) {
+        return checkFlowRule(dstIp, IPV4_DST);
     }
 
     /**
      * Checks whether north-south ICMP reply rule is added or not.
      *
-     * @param ip    IP address
+     * @param srcIp    IP address
      * @return true if ICMP reply rule is added, false otherwise
      */
-    private boolean checkNorthSouthIcmpReplyRule(String ip) {
-        for (FlowEntry entry : flowRuleService.getFlowEntriesById(appId)) {
-            TrafficSelector selector = entry.selector();
-
-            IPCriterion ipCriterion = (IPCriterion) selector.getCriterion(IPV4_SRC);
-
-            if (ipCriterion != null &&
-                    ip.equals(ipCriterion.ip().address().toString()) &&
-                    entry.state() == ADDED) {
-                return true;
-            }
-        }
-
-        return false;
+    private boolean checkNorthSouthIcmpReplyRule(String srcIp) {
+        return checkFlowRule(srcIp, IPV4_SRC);
     }
 
     /**
@@ -338,18 +315,28 @@
      * @return true if the rule is added, false otherwise
      */
     private boolean checkVidTagRule(String srcIp) {
+        return checkFlowRule(srcIp, IPV4_SRC);
+    }
+
+    /**
+     * Checks whether flow rules with the given IP and criterion are added or not.
+     *
+     * @param ip        IP address
+     * @param ipType    IP criterion type (IPV4_DST or IPV4_SRC)
+     * @return true if the flow rule is added, false otherwise
+     */
+    private boolean checkFlowRule(String ip, Criterion.Type ipType) {
         for (FlowEntry entry : flowRuleService.getFlowEntriesById(appId)) {
             TrafficSelector selector = entry.selector();
 
-            IPCriterion srcIpCriterion = (IPCriterion) selector.getCriterion(IPV4_SRC);
+            IPCriterion ipCriterion = (IPCriterion) selector.getCriterion(ipType);
 
-            if (srcIpCriterion != null &&
-                    srcIp.equals(srcIpCriterion.ip().address().toString()) &&
+            if (ipCriterion != null &&
+                    ip.equals(ipCriterion.ip().address().toString()) &&
                     entry.state() == ADDED) {
                 return true;
             }
         }
-
         return false;
     }