Implement host probing retry with major refactoring

- Implement probe retry
- Switch to typical core/provider design pattern for HostProbingService
  and as a result decoupling the dependency between SR and HostLocationProvider

Change-Id: I33a15af580677ea376b421ac3e26f9821dcca844
diff --git a/core/api/src/main/java/org/onosproject/net/host/HostLocationProbingService.java b/core/api/src/main/java/org/onosproject/net/host/HostLocationProbingService.java
index 56d056c..66f1266 100644
--- a/core/api/src/main/java/org/onosproject/net/host/HostLocationProbingService.java
+++ b/core/api/src/main/java/org/onosproject/net/host/HostLocationProbingService.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2017-present Open Networking Foundation
+ * Copyright 2018-present Open Networking Foundation
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,31 +18,21 @@
 import org.onosproject.net.ConnectPoint;
 import org.onosproject.net.Host;
 
+/**
+ * Service for interacting with the host probing entities.
+ *
+ * @deprecated in ONOS 1.12, replaced by {@link HostProbingService}
+ */
+@Deprecated
 public interface HostLocationProbingService {
     /**
-     * Mode of host location probing.
-     */
-    enum ProbeMode {
-        /**
-         * Append probed host location if reply is received before timeout. Otherwise, do nothing.
-         * Typically used to discover secondary locations.
-         */
-        DISCOVER,
-
-        /**
-         * Remove probed host location if reply is received after timeout. Otherwise, do nothing.
-         * Typically used to verify previous locations.
-         */
-        VERIFY
-    }
-
-    /**
      * Probes given host on given location.
      *
      * @param host the host to be probed
      * @param connectPoint the location of host to be probed
      * @param probeMode probe mode
+     * @deprecated in ONOS 1.12, replaced by {@link HostProbingService#probeHost(Host, ConnectPoint, ProbeMode)}
      */
-    void probeHostLocation(Host host, ConnectPoint connectPoint, ProbeMode probeMode);
-
+    @Deprecated
+    void probeHost(Host host, ConnectPoint connectPoint, ProbeMode probeMode);
 }
diff --git a/core/api/src/main/java/org/onosproject/net/host/HostProbe.java b/core/api/src/main/java/org/onosproject/net/host/HostProbe.java
new file mode 100644
index 0000000..7303a3d
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/host/HostProbe.java
@@ -0,0 +1,58 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.net.host;
+
+import org.onlab.packet.MacAddress;
+import org.onosproject.net.ConnectPoint;
+import org.onosproject.net.Host;
+
+/**
+ * Information related to the host being probed.
+ */
+public interface HostProbe extends Host {
+    /**
+     * Gets connect point of this entry.
+     *
+     * @return connect point
+     */
+    ConnectPoint connectPoint();
+
+    /**
+     * Gets retry counter of this entry.
+     *
+     * @return retry
+     */
+    int retry();
+
+    /**
+     * Decrease retry counter of this entry by one.
+     */
+    void decreaseRetry();
+
+    /**
+     * Gets mode of this entry.
+     *
+     * @return mode
+     */
+    ProbeMode mode();
+
+    /**
+     * Gets probe MAC of this entry.
+     *
+     * @return probe mac
+     */
+    MacAddress probeMac();
+}
diff --git a/core/api/src/main/java/org/onosproject/net/host/HostProbeStore.java b/core/api/src/main/java/org/onosproject/net/host/HostProbeStore.java
new file mode 100644
index 0000000..ba1217d
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/host/HostProbeStore.java
@@ -0,0 +1,49 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.net.host;
+
+import org.onlab.packet.MacAddress;
+import org.onosproject.net.ConnectPoint;
+import org.onosproject.net.Host;
+import org.onosproject.store.Store;
+
+/**
+ * Manages inventory of pending host probes.
+ */
+public interface HostProbeStore extends Store<HostProbingEvent, HostProbingStoreDelegate> {
+
+    /**
+     * Notifies HostProbeStore the beginning of pending host location verification and
+     * retrieves the unique MAC address for the probe.
+     *
+     * @param host host to be probed
+     * @param connectPoint the connect point that is under verification
+     * @param probeMode probe mode
+     * @param probeMac probeMac if this is a retry.
+     *                 Null if this is the very first probe and the probeMac is to-be-generated
+     * @param retry max retry times
+     * @return probeMac, the source MAC address ONOS uses to probe the host
+     */
+    MacAddress addProbingHost(Host host, ConnectPoint connectPoint, ProbeMode probeMode,
+                                      MacAddress probeMac, int retry);
+
+    /**
+     * Notifies HostProbeStore the end of pending host location verification.
+     *
+     * @param probeMac the source MAC address ONOS uses to probe the host
+     */
+    void removeProbingHost(MacAddress probeMac);
+}
diff --git a/core/api/src/main/java/org/onosproject/net/host/HostProbingEvent.java b/core/api/src/main/java/org/onosproject/net/host/HostProbingEvent.java
new file mode 100644
index 0000000..b77334a
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/host/HostProbingEvent.java
@@ -0,0 +1,123 @@
+/*
+ * Copyright 2014-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.net.host;
+
+import org.onlab.util.Tools;
+import org.onosproject.event.AbstractEvent;
+
+import static com.google.common.base.MoreObjects.toStringHelper;
+
+/**
+ * Describes host probing event.
+ */
+public class HostProbingEvent extends AbstractEvent<HostProbingEvent.Type, HostProbe> {
+
+    /**
+     * Type of host probing events.
+     */
+    public enum Type {
+        /**
+         * Probe has been requested.
+         */
+        PROBE_REQUESTED,
+
+        /**
+         * Probe timed out but still have not reach max retry.
+         */
+        PROBE_TIMEOUT,
+
+        /**
+         * Probe timed out and reach max retry.
+         */
+        PROBE_FAIL,
+
+        /**
+         * Probe has been complete normally.
+         */
+        PROBE_COMPLETED
+    }
+
+    private HostProbe prevSubject;
+
+    /**
+     * Creates an event of a given type and for the specified host probe and the
+     * current time.
+     *
+     * @param type probing host event type
+     * @param subject event subject
+     */
+    public HostProbingEvent(Type type, HostProbe subject) {
+        super(type, subject);
+    }
+
+    /**
+     * Creates an event of a given type and for the specified host probe and time.
+     *
+     * @param type probing host event type
+     * @param subject event subject
+     * @param time occurrence time
+     */
+    public HostProbingEvent(Type type, HostProbe subject, long time) {
+        super(type, subject, time);
+    }
+
+    /**
+     * Creates an event with previous subject.
+     * The previous subject is ignored if the type is not PROBE_TIMEOUT
+     *
+     * @param type host event type
+     * @param subject event subject
+     * @param prevSubject previous host subject
+     */
+    public HostProbingEvent(Type type, HostProbe subject, HostProbe prevSubject) {
+        super(type, subject);
+        this.prevSubject = prevSubject;
+    }
+
+    /**
+     * Creates an event with previous subject and specified time.
+     * The previous subject is ignored if the type is not PROBE_TIMEOUT
+     *
+     * @param type host event type
+     * @param subject event subject
+     * @param prevSubject previous host subject
+     * @param time occurrence time
+     */
+    public HostProbingEvent(Type type, HostProbe subject, HostProbe prevSubject, long time) {
+        super(type, subject, time);
+        this.prevSubject = prevSubject;
+    }
+
+    /**
+     * Gets the previous subject in this host probe event.
+     *
+     * @return the previous subject, or null if previous subject is not
+     *         specified.
+     */
+    public HostProbe prevSubject() {
+        return this.prevSubject;
+    }
+
+    @Override
+    public String toString() {
+        return toStringHelper(this)
+                .add("time", Tools.defaultOffsetDataTime(time()))
+                .add("type", type())
+                .add("subject", subject())
+                .add("prevSubject", prevSubject())
+                .toString();
+    }
+}
diff --git a/core/api/src/main/java/org/onosproject/net/host/HostProbingListener.java b/core/api/src/main/java/org/onosproject/net/host/HostProbingListener.java
new file mode 100644
index 0000000..25fd1ea
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/host/HostProbingListener.java
@@ -0,0 +1,24 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.net.host;
+
+import org.onosproject.event.EventListener;
+
+/**
+ * Entity capable of receiving host probing related events.
+ */
+public interface HostProbingListener extends EventListener<HostProbingEvent> {
+}
diff --git a/core/api/src/main/java/org/onosproject/net/host/HostProbingProvider.java b/core/api/src/main/java/org/onosproject/net/host/HostProbingProvider.java
new file mode 100644
index 0000000..f126013
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/host/HostProbingProvider.java
@@ -0,0 +1,42 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.net.host;
+
+import org.onosproject.net.ConnectPoint;
+import org.onosproject.net.Host;
+import org.onosproject.net.provider.Provider;
+
+/**
+ * Provider of host probing.
+ */
+public interface HostProbingProvider extends Provider {
+
+    /**
+     * Probe given host on the given connectPoint with given probeMode.
+     *
+     * @param host host to be probed
+     * @param connectPoint connect point on which the probe is sent
+     * @param probeMode probe mode
+     */
+    void probeHost(Host host, ConnectPoint connectPoint, ProbeMode probeMode);
+
+    /**
+     * Process host probing events.
+     *
+     * @param event host probing event
+     */
+    void processEvent(HostProbingEvent event);
+}
diff --git a/core/api/src/main/java/org/onosproject/net/host/HostProbingProviderRegistry.java b/core/api/src/main/java/org/onosproject/net/host/HostProbingProviderRegistry.java
new file mode 100644
index 0000000..915df6c
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/host/HostProbingProviderRegistry.java
@@ -0,0 +1,25 @@
+/*
+ * Copyright 2014-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.net.host;
+
+import org.onosproject.net.provider.ProviderRegistry;
+
+/**
+ * Abstraction of a host probing provider registry.
+ */
+public interface HostProbingProviderRegistry
+        extends ProviderRegistry<HostProbingProvider, HostProbingProviderService> {
+}
diff --git a/core/api/src/main/java/org/onosproject/net/host/HostProbingProviderService.java b/core/api/src/main/java/org/onosproject/net/host/HostProbingProviderService.java
new file mode 100644
index 0000000..d9c7c16
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/host/HostProbingProviderService.java
@@ -0,0 +1,49 @@
+/*
+ * Copyright 2014-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.net.host;
+
+import org.onlab.packet.MacAddress;
+import org.onosproject.net.ConnectPoint;
+import org.onosproject.net.Host;
+import org.onosproject.net.provider.ProviderService;
+
+/**
+ * Means of conveying host probing information to the core.
+ */
+public interface HostProbingProviderService extends ProviderService<HostProbingProvider> {
+
+    /**
+     * Notifies HostProbeStore the beginning of pending host location verification and
+     * retrieves the unique MAC address for the probe.
+     *
+     * @param host host to be probed
+     * @param connectPoint the connect point that is under verification
+     * @param probeMode probe mode
+     * @param probeMac probeMac if this is a retry.
+     *                 Null if this is the very first probe and the probeMac is to-be-generated
+     * @param retry max retry times
+     * @return probeMac, the source MAC address ONOS uses to probe the host
+     */
+     MacAddress addProbingHost(Host host, ConnectPoint connectPoint, ProbeMode probeMode,
+                                      MacAddress probeMac, int retry);
+
+    /**
+     * Notifies HostProbeStore the end of pending host location verification.
+     *
+     * @param probeMac the source MAC address ONOS uses to probe the host
+     */
+     void removeProbingHost(MacAddress probeMac);
+}
diff --git a/core/api/src/main/java/org/onosproject/net/host/HostProbingService.java b/core/api/src/main/java/org/onosproject/net/host/HostProbingService.java
new file mode 100644
index 0000000..6113dd4
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/host/HostProbingService.java
@@ -0,0 +1,33 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.net.host;
+
+import org.onosproject.net.ConnectPoint;
+import org.onosproject.net.Host;
+
+/**
+ * Service for interacting with the host probing entities.
+ */
+public interface HostProbingService {
+    /**
+     * Probes given host on given location.
+     *
+     * @param host the host to be probed
+     * @param connectPoint the location of host to be probed
+     * @param probeMode probe mode
+     */
+    void probeHost(Host host, ConnectPoint connectPoint, ProbeMode probeMode);
+}
diff --git a/core/api/src/main/java/org/onosproject/net/host/HostProbingStoreDelegate.java b/core/api/src/main/java/org/onosproject/net/host/HostProbingStoreDelegate.java
new file mode 100644
index 0000000..5221951
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/host/HostProbingStoreDelegate.java
@@ -0,0 +1,24 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.net.host;
+
+import org.onosproject.store.StoreDelegate;
+
+/**
+ * Host probing store delegate abstraction.
+ */
+public interface HostProbingStoreDelegate extends StoreDelegate<HostProbingEvent> {
+}
diff --git a/core/api/src/main/java/org/onosproject/net/host/HostProviderService.java b/core/api/src/main/java/org/onosproject/net/host/HostProviderService.java
index d9aeff5..f3dc7ab 100644
--- a/core/api/src/main/java/org/onosproject/net/host/HostProviderService.java
+++ b/core/api/src/main/java/org/onosproject/net/host/HostProviderService.java
@@ -15,12 +15,12 @@
  */
 package org.onosproject.net.host;
 
+import org.apache.commons.lang3.NotImplementedException;
 import org.onlab.packet.IpAddress;
 import org.onlab.packet.MacAddress;
 import org.onosproject.net.ConnectPoint;
 import org.onosproject.net.HostId;
 import org.onosproject.net.HostLocation;
-import org.onosproject.net.host.HostLocationProbingService.ProbeMode;
 import org.onosproject.net.provider.ProviderService;
 
 /**
@@ -54,6 +54,16 @@
     void removeIpFromHost(HostId hostId, IpAddress ipAddress);
 
     /**
+     * Notifies the core when a location is associated with a host.
+     *
+     * @param hostId id of the host
+     * @param location location of host that gets discovered
+     */
+    default void addLocationToHost(HostId hostId, HostLocation location) {
+        throw new NotImplementedException("addLocationToHost is not implemented");
+    }
+
+    /**
      * Notifies the core when a location is no longer associated with a host.
      *
      * @param hostId id of the host
@@ -69,7 +79,9 @@
      * @param connectPoint the connect point that is under verification
      * @param probeMode probe mode
      * @return probeMac, the source MAC address ONOS uses to probe the host
+     * @deprecated in ONOS 1.12, replaced by {@link HostProbingProviderService}
      */
+    @Deprecated
     default MacAddress addPendingHostLocation(HostId hostId, ConnectPoint connectPoint, ProbeMode probeMode) {
         return MacAddress.NONE;
     }
@@ -78,6 +90,8 @@
      * Notifies HostProviderService the end of pending host location verification.
      *
      * @param probeMac the source MAC address ONOS uses to probe the host
+     * @deprecated in ONOS 1.12, replaced by {@link HostProbingProviderService}
      */
+    @Deprecated
     default void removePendingHostLocation(MacAddress probeMac) {}
 }
diff --git a/core/api/src/main/java/org/onosproject/net/host/HostStore.java b/core/api/src/main/java/org/onosproject/net/host/HostStore.java
index 96d3c31..0b6238b 100644
--- a/core/api/src/main/java/org/onosproject/net/host/HostStore.java
+++ b/core/api/src/main/java/org/onosproject/net/host/HostStore.java
@@ -23,7 +23,6 @@
 import org.onosproject.net.Host;
 import org.onosproject.net.HostId;
 import org.onosproject.net.HostLocation;
-import org.onosproject.net.host.HostLocationProbingService.ProbeMode;
 import org.onosproject.net.provider.ProviderId;
 import org.onosproject.store.Store;
 
diff --git a/core/api/src/main/java/org/onosproject/net/host/ProbeMode.java b/core/api/src/main/java/org/onosproject/net/host/ProbeMode.java
new file mode 100644
index 0000000..bc3efbf
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/host/ProbeMode.java
@@ -0,0 +1,33 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.net.host;
+
+/**
+ * Mode of host location probing.
+ */
+public enum ProbeMode {
+    /**
+     * Append probed host location if reply is received before timeout. Otherwise, do nothing.
+     * Typically used to discover secondary locations.
+     */
+    DISCOVER,
+
+    /**
+     * Remove probed host location if reply is received after timeout. Otherwise, do nothing.
+     * Typically used to verify previous locations.
+     */
+    VERIFY
+}
diff --git a/core/net/src/main/java/org/onosproject/net/host/impl/HostManager.java b/core/net/src/main/java/org/onosproject/net/host/impl/HostManager.java
index 998f7df..31e8904 100644
--- a/core/net/src/main/java/org/onosproject/net/host/impl/HostManager.java
+++ b/core/net/src/main/java/org/onosproject/net/host/impl/HostManager.java
@@ -29,7 +29,6 @@
 import org.onlab.packet.VlanId;
 import org.onlab.util.Tools;
 import org.onosproject.cfg.ComponentConfigService;
-import org.onosproject.net.host.HostLocationProbingService.ProbeMode;
 import org.onosproject.net.intf.Interface;
 import org.onosproject.net.intf.InterfaceService;
 import org.onosproject.net.HostLocation;
@@ -442,6 +441,20 @@
         }
 
         @Override
+        public void addLocationToHost(HostId hostId, HostLocation location) {
+            checkNotNull(hostId, HOST_ID_NULL);
+            checkValidity();
+
+            if (!allowedToChange(hostId)) {
+                log.info("Request to remove {} from {} is ignored due to provider mismatch",
+                        location, hostId);
+                return;
+            }
+
+            store.appendLocation(hostId, location);
+        }
+
+        @Override
         public void removeLocationFromHost(HostId hostId, HostLocation location) {
             checkNotNull(hostId, HOST_ID_NULL);
             checkValidity();
@@ -455,16 +468,6 @@
             store.removeLocation(hostId, location);
         }
 
-        @Override
-        public MacAddress addPendingHostLocation(HostId hostId, ConnectPoint connectPoint, ProbeMode probeMode) {
-            return store.addPendingHostLocation(hostId, connectPoint, probeMode);
-        }
-
-        @Override
-        public void removePendingHostLocation(MacAddress probeMac) {
-            store.removePendingHostLocation(probeMac);
-        }
-
         /**
          * Providers should only be able to remove a host that is provided by itself,
          * or a host that is not configured.
diff --git a/core/net/src/main/java/org/onosproject/net/host/impl/HostProbingManager.java b/core/net/src/main/java/org/onosproject/net/host/impl/HostProbingManager.java
new file mode 100644
index 0000000..648e200
--- /dev/null
+++ b/core/net/src/main/java/org/onosproject/net/host/impl/HostProbingManager.java
@@ -0,0 +1,105 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.net.host.impl;
+
+import org.apache.felix.scr.annotations.Activate;
+import org.apache.felix.scr.annotations.Component;
+import org.apache.felix.scr.annotations.Deactivate;
+import org.apache.felix.scr.annotations.Reference;
+import org.apache.felix.scr.annotations.ReferenceCardinality;
+import org.apache.felix.scr.annotations.Service;
+import org.onlab.packet.MacAddress;
+import org.onosproject.net.ConnectPoint;
+import org.onosproject.net.Host;
+import org.onosproject.net.host.HostLocationProbingService;
+import org.onosproject.net.host.HostProbingEvent;
+import org.onosproject.net.host.ProbeMode;
+import org.onosproject.net.host.HostProbingListener;
+import org.onosproject.net.host.HostProbingProvider;
+import org.onosproject.net.host.HostProbingProviderService;
+import org.onosproject.net.host.HostProbingService;
+import org.onosproject.net.host.HostProbeStore;
+import org.onosproject.net.host.HostProbingProviderRegistry;
+import org.onosproject.net.host.HostProbingStoreDelegate;
+import org.onosproject.net.provider.AbstractListenerProviderRegistry;
+import org.onosproject.net.provider.AbstractProviderService;
+import org.slf4j.Logger;
+
+import static org.slf4j.LoggerFactory.getLogger;
+
+@Component(immediate = true)
+@Service
+public class HostProbingManager extends
+        AbstractListenerProviderRegistry<HostProbingEvent, HostProbingListener, HostProbingProvider,
+                HostProbingProviderService>
+        implements HostProbingService, HostProbingProviderRegistry, HostLocationProbingService {
+    private final Logger log = getLogger(getClass());
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    private HostProbeStore hostProbeStore;
+
+    private static final String SCHEME = "hostprobing";
+
+    private HostProbingStoreDelegate delegate = event -> {
+        getProvider(SCHEME).processEvent(event);
+    };
+
+    @Activate
+    public void activate() {
+        hostProbeStore.setDelegate(delegate);
+    }
+
+    @Deactivate
+    public void deactivate() {
+        hostProbeStore.unsetDelegate(delegate);
+    }
+
+    @Override
+    public void probeHost(Host host, ConnectPoint connectPoint, ProbeMode probeMode) {
+        HostProbingProvider provider = getProvider(SCHEME);
+        if (provider == null) {
+            log.warn("Unable to find host probing provider. Cannot {} {} at {}",
+                    probeMode, host, connectPoint);
+            return;
+        }
+        provider.probeHost(host, connectPoint, probeMode);
+    }
+
+    @Override
+    protected HostProbingProviderService createProviderService(HostProbingProvider provider) {
+        return new InternalHostProbingProviderService(provider);
+    }
+
+    private class InternalHostProbingProviderService
+            extends AbstractProviderService<HostProbingProvider>
+            implements HostProbingProviderService {
+        InternalHostProbingProviderService(HostProbingProvider provider) {
+            super(provider);
+        }
+
+        @Override
+        public MacAddress addProbingHost(Host host, ConnectPoint connectPoint, ProbeMode mode,
+                                         MacAddress probeMac, int retry) {
+            return hostProbeStore.addProbingHost(host, connectPoint, mode, probeMac, retry);
+        }
+
+        @Override
+        public void removeProbingHost(MacAddress probeMac) {
+            hostProbeStore.removeProbingHost(probeMac);
+        }
+    }
+}
diff --git a/core/store/dist/src/main/java/org/onosproject/store/host/impl/DefaultHostProbe.java b/core/store/dist/src/main/java/org/onosproject/store/host/impl/DefaultHostProbe.java
new file mode 100644
index 0000000..5ab72fc
--- /dev/null
+++ b/core/store/dist/src/main/java/org/onosproject/store/host/impl/DefaultHostProbe.java
@@ -0,0 +1,113 @@
+/*
+ * Copyright 2017-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.store.host.impl;
+
+import org.onlab.packet.MacAddress;
+import org.onosproject.net.ConnectPoint;
+import org.onosproject.net.DefaultHost;
+import org.onosproject.net.Host;
+import org.onosproject.net.host.ProbeMode;
+import org.onosproject.net.host.HostProbe;
+
+import java.util.Objects;
+
+import static com.google.common.base.MoreObjects.toStringHelper;
+
+/**
+ * Internal data structure to record the info of a host with location that is under verification.
+ */
+class DefaultHostProbe extends DefaultHost implements HostProbe {
+    private ConnectPoint connectPoint;
+    private int retry;
+    private ProbeMode mode;
+    private MacAddress probeMac;
+
+    /**
+     * Constructs DefaultHostProbe with given retry.
+     *
+     * @param host host to be probed
+     * @param connectPoint location to be verified
+     * @param probeMac source MAC address of the probe
+     * @param mode probe mode
+     * @param retry number of retry
+     */
+    DefaultHostProbe(Host host, ConnectPoint connectPoint, ProbeMode mode, MacAddress probeMac, int retry) {
+        super(host.providerId(), host.id(), host.mac(), host.vlan(), host.locations(), host.ipAddresses(),
+                host.configured());
+
+        this.connectPoint = connectPoint;
+        this.mode = mode;
+        this.probeMac = probeMac;
+        this.retry = retry;
+    }
+
+    @Override
+    public ConnectPoint connectPoint() {
+        return connectPoint;
+    }
+
+    @Override
+    public int retry() {
+        return retry;
+    }
+
+    @Override
+    public void decreaseRetry() {
+        this.retry -= 1;
+    }
+
+    @Override
+    public ProbeMode mode() {
+        return mode;
+    }
+
+    @Override
+    public MacAddress probeMac() {
+        return probeMac;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (!(o instanceof DefaultHostProbe)) {
+            return false;
+        }
+        DefaultHostProbe that = (DefaultHostProbe) o;
+        return (super.equals(o) &&
+                Objects.equals(this.connectPoint, that.connectPoint) &&
+                Objects.equals(this.retry, that.retry) &&
+                Objects.equals(this.mode, that.mode)) &&
+                Objects.equals(this.probeMac, that.probeMac);
+    }
+    @Override
+    public int hashCode() {
+        return Objects.hash(super.hashCode(), connectPoint, retry, mode, probeMac);
+    }
+
+    @Override
+    public String toString() {
+        return toStringHelper(getClass())
+                .add("host", super.toString())
+                .add("location", connectPoint)
+                .add("retry", retry)
+                .add("mode", mode)
+                .add("probeMac", probeMac)
+                .toString();
+    }
+}
diff --git a/core/store/dist/src/main/java/org/onosproject/store/host/impl/DefaultHostProbeStore.java b/core/store/dist/src/main/java/org/onosproject/store/host/impl/DefaultHostProbeStore.java
new file mode 100644
index 0000000..33cb7ad
--- /dev/null
+++ b/core/store/dist/src/main/java/org/onosproject/store/host/impl/DefaultHostProbeStore.java
@@ -0,0 +1,199 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.store.host.impl;
+
+import com.google.common.cache.Cache;
+import com.google.common.cache.CacheBuilder;
+import com.google.common.cache.RemovalNotification;
+import org.apache.felix.scr.annotations.Activate;
+import org.apache.felix.scr.annotations.Component;
+import org.apache.felix.scr.annotations.Deactivate;
+import org.apache.felix.scr.annotations.Reference;
+import org.apache.felix.scr.annotations.ReferenceCardinality;
+import org.apache.felix.scr.annotations.Service;
+import org.onlab.packet.MacAddress;
+import org.onlab.util.KryoNamespace;
+import org.onosproject.net.ConnectPoint;
+import org.onosproject.net.Host;
+import org.onosproject.net.host.HostProbe;
+import org.onosproject.net.host.HostProbeStore;
+import org.onosproject.net.host.HostProbingEvent;
+import org.onosproject.net.host.ProbeMode;
+import org.onosproject.net.host.HostProbingStoreDelegate;
+import org.onosproject.store.AbstractStore;
+import org.onosproject.store.serializers.KryoNamespaces;
+import org.onosproject.store.service.AtomicCounter;
+import org.onosproject.store.service.ConsistentMap;
+import org.onosproject.store.service.MapEvent;
+import org.onosproject.store.service.MapEventListener;
+import org.onosproject.store.service.Serializer;
+import org.onosproject.store.service.StorageService;
+import org.onosproject.store.service.Versioned;
+import org.slf4j.Logger;
+
+import java.util.Map;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+
+import static java.util.concurrent.Executors.newSingleThreadScheduledExecutor;
+import static org.onlab.util.Tools.groupedThreads;
+import static org.slf4j.LoggerFactory.getLogger;
+
+@Component(immediate = true)
+@Service
+public class DefaultHostProbeStore extends AbstractStore<HostProbingEvent, HostProbingStoreDelegate>
+        implements HostProbeStore {
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected StorageService storageService;
+
+    private final Logger log = getLogger(getClass());
+
+    // TODO make this configurable
+    private static final int PROBE_TIMEOUT_MS = 3000;
+
+    private AtomicCounter hostProbeIndex;
+    private Cache<MacAddress, HostProbe> probingHostsCache;
+    private ConsistentMap<MacAddress, HostProbe> probingHostsConsistentMap;
+    private Map<MacAddress, HostProbe> probingHosts;
+    private MapEventListener<MacAddress, HostProbe> probingHostListener = new ProbingHostListener();
+    private ScheduledExecutorService cacheCleaner;
+    private ScheduledExecutorService locationRemover;
+
+    @Activate
+    public void activate() {
+        KryoNamespace.Builder pendingHostSerializer = KryoNamespace.newBuilder()
+                .register(KryoNamespaces.API)
+                .register(DefaultHostProbe.class)
+                .register(ProbeMode.class);
+        probingHostsConsistentMap = storageService.<MacAddress, HostProbe>consistentMapBuilder()
+                .withName("onos-hosts-pending")
+                .withRelaxedReadConsistency()
+                .withSerializer(Serializer.using(pendingHostSerializer.build()))
+                .build();
+        probingHostsConsistentMap.addListener(probingHostListener);
+        probingHosts = probingHostsConsistentMap.asJavaMap();
+
+        hostProbeIndex = storageService.atomicCounterBuilder()
+                .withName("onos-hosts-probe-index")
+                .build()
+                .asAtomicCounter();
+
+        probingHostsCache = CacheBuilder.newBuilder()
+                .expireAfterWrite(PROBE_TIMEOUT_MS, TimeUnit.MILLISECONDS)
+                .removalListener((RemovalNotification<MacAddress, HostProbe> notification) -> {
+                    MacAddress probeMac = notification.getKey();
+                    switch (notification.getCause()) {
+                        case EXPIRED:
+                        case REPLACED:
+                            probingHosts.computeIfPresent(probeMac, (k, v) -> {
+                                v.decreaseRetry();
+                                return v;
+                            });
+                            break;
+                        case EXPLICIT:
+                            break;
+                        default:
+                            log.warn("Remove {} from pendingHostLocations for unexpected reason {}",
+                                    notification.getKey(), notification.getCause());
+                    }
+                }).build();
+
+        cacheCleaner = newSingleThreadScheduledExecutor(
+                groupedThreads("onos/host/hostprobestore", "cache-cleaner", log));
+        cacheCleaner.scheduleAtFixedRate(probingHostsCache::cleanUp, 0, PROBE_TIMEOUT_MS, TimeUnit.MILLISECONDS);
+        locationRemover = newSingleThreadScheduledExecutor(
+                groupedThreads("onos/host/hostprobestore", "loc-remover", log));
+
+        log.info("Started");
+    }
+
+    @Deactivate
+    public void deactivate() {
+        cacheCleaner.shutdown();
+        locationRemover.shutdown();
+        probingHostsCache.cleanUp();
+
+        log.info("Stopped");
+    }
+
+    @Override
+    public MacAddress addProbingHost(Host host, ConnectPoint connectPoint, ProbeMode probeMode,
+                                     MacAddress probeMac, int retry) {
+        if (probeMac == null) {
+            probeMac = generateProbeMac();
+        }
+        DefaultHostProbe probingHost = new DefaultHostProbe(host, connectPoint, probeMode, probeMac, retry);
+        probingHostsCache.put(probeMac, probingHost);
+        probingHosts.put(probeMac, probingHost);
+        return probeMac;
+    }
+
+    @Override
+    public void removeProbingHost(MacAddress probeMac) {
+        probingHostsCache.invalidate(probeMac);
+        probingHosts.remove(probeMac);
+    }
+
+    private MacAddress generateProbeMac() {
+        // Use ONLab OUI (3 bytes) + atomic counter (3 bytes) as the source MAC of the probe
+        long nextIndex = hostProbeIndex.incrementAndGet();
+        return MacAddress.valueOf(MacAddress.NONE.toLong() + nextIndex);
+    }
+
+    private class ProbingHostListener implements MapEventListener<MacAddress, HostProbe> {
+        @Override
+        public void event(MapEvent<MacAddress, HostProbe> event) {
+            HostProbe newValue = Versioned.valueOrNull(event.newValue());
+            HostProbe oldValue = Versioned.valueOrNull(event.oldValue());
+
+            HostProbingEvent hostProbingEvent;
+            switch (event.type()) {
+                case INSERT:
+                    hostProbingEvent = new HostProbingEvent(HostProbingEvent.Type.PROBE_REQUESTED, newValue);
+                    notifyDelegate(hostProbingEvent);
+                    break;
+                case UPDATE:
+                    // Fail VERIFY probe immediately. Only allow DISCOVER probe to retry.
+                    if (newValue.retry() > 0) {
+                        if (newValue.mode() == ProbeMode.DISCOVER) {
+                            hostProbingEvent = new HostProbingEvent(HostProbingEvent.Type.PROBE_TIMEOUT,
+                                    newValue, oldValue);
+                            notifyDelegate(hostProbingEvent);
+                        } else {
+                            hostProbingEvent = new HostProbingEvent(HostProbingEvent.Type.PROBE_FAIL,
+                                    newValue, oldValue);
+                            notifyDelegate(hostProbingEvent);
+                        }
+                    } else {
+                        // Remove from pendingHost and let the remove listener generates the event
+                        locationRemover.execute(() -> probingHosts.remove(event.key()));
+                    }
+                    break;
+                case REMOVE:
+                    if (oldValue.retry() > 0) {
+                        hostProbingEvent = new HostProbingEvent(HostProbingEvent.Type.PROBE_COMPLETED, oldValue);
+                        notifyDelegate(hostProbingEvent);
+                    } else {
+                        hostProbingEvent = new HostProbingEvent(HostProbingEvent.Type.PROBE_FAIL, oldValue);
+                        notifyDelegate(hostProbingEvent);
+                    }
+                    break;
+                default:
+                    log.warn("Unknown map event type: {}", event.type());
+            }
+        }
+    }
+}
diff --git a/core/store/dist/src/main/java/org/onosproject/store/host/impl/DistributedHostStore.java b/core/store/dist/src/main/java/org/onosproject/store/host/impl/DistributedHostStore.java
index aa811ba..d179288 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/host/impl/DistributedHostStore.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/host/impl/DistributedHostStore.java
@@ -15,9 +15,6 @@
  */
 package org.onosproject.store.host.impl;
 
-import com.google.common.cache.Cache;
-import com.google.common.cache.CacheBuilder;
-import com.google.common.cache.RemovalNotification;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Sets;
 
@@ -43,18 +40,15 @@
 import org.onosproject.net.host.HostEvent;
 import org.onosproject.net.host.HostStore;
 import org.onosproject.net.host.HostStoreDelegate;
-import org.onosproject.net.host.HostLocationProbingService.ProbeMode;
 import org.onosproject.net.provider.ProviderId;
 import org.onosproject.store.AbstractStore;
 import org.onosproject.store.serializers.KryoNamespaces;
-import org.onosproject.store.service.AtomicCounter;
 import org.onosproject.store.service.ConsistentMap;
 import org.onosproject.store.service.MapEvent;
 import org.onosproject.store.service.MapEventListener;
 import org.onosproject.store.service.Serializer;
 import org.onosproject.store.service.StorageService;
 import org.onosproject.store.service.DistributedPrimitive.Status;
-import org.onosproject.store.service.Versioned;
 import org.slf4j.Logger;
 
 import java.util.Collection;
@@ -62,11 +56,9 @@
 import java.util.Iterator;
 import java.util.Map;
 import java.util.Objects;
-import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ScheduledExecutorService;
-import java.util.concurrent.TimeUnit;
 import java.util.function.Consumer;
 import java.util.function.Predicate;
 import java.util.stream.Collectors;
@@ -93,47 +85,16 @@
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
     protected StorageService storageService;
 
-    private AtomicCounter hostProbeIndex;
     private ConsistentMap<HostId, DefaultHost> hostsConsistentMap;
     private Map<HostId, DefaultHost> hosts;
     private Map<IpAddress, Set<Host>> hostsByIp;
     private MapEventListener<HostId, DefaultHost> hostLocationTracker =
             new HostLocationTracker();
 
-    private ConsistentMap<MacAddress, PendingHostLocation> pendingHostsConsistentMap;
-    private Map<MacAddress, PendingHostLocation> pendingHosts;
-    private MapEventListener<MacAddress, PendingHostLocation> pendingHostListener =
-            new PendingHostListener();
-
     private ScheduledExecutorService executor;
-    private ScheduledExecutorService cacheCleaner;
-    private ScheduledExecutorService locationRemover;
 
     private Consumer<Status> statusChangeListener;
 
-    // TODO make this configurable
-    private static final int PROBE_TIMEOUT_MS = 3000;
-
-    private Cache<MacAddress, PendingHostLocation> pendingHostsCache = CacheBuilder.newBuilder()
-            .expireAfterWrite(PROBE_TIMEOUT_MS, TimeUnit.MILLISECONDS)
-            .removalListener((RemovalNotification<MacAddress, PendingHostLocation> notification) -> {
-                switch (notification.getCause()) {
-                    case EXPIRED:
-                        PendingHostLocation expired = notification.getValue();
-                        if (expired != null) {
-                            if (timeoutPendingHostLocation(notification.getKey())) {
-                                log.info("Evict {} from pendingHosts due to probe timeout", notification.getValue());
-                            }
-                        }
-                        break;
-                    case EXPLICIT:
-                        break;
-                    default:
-                        log.warn("Remove {} from pendingHostLocations for unexpected reason {}",
-                                notification.getKey(), notification.getCause());
-                }
-            }).build();
-
     @Activate
     public void activate() {
         KryoNamespace.Builder hostSerializer = KryoNamespace.newBuilder()
@@ -146,28 +107,6 @@
         hostsConsistentMap.addListener(hostLocationTracker);
         hosts = hostsConsistentMap.asJavaMap();
 
-        KryoNamespace.Builder pendingHostSerializer = KryoNamespace.newBuilder()
-                .register(KryoNamespaces.API)
-                .register(PendingHostLocation.class)
-                .register(ProbeMode.class);
-        pendingHostsConsistentMap = storageService.<MacAddress, PendingHostLocation>consistentMapBuilder()
-                .withName("onos-hosts-pending")
-                .withRelaxedReadConsistency()
-                .withSerializer(Serializer.using(pendingHostSerializer.build()))
-                .build();
-        pendingHostsConsistentMap.addListener(pendingHostListener);
-        pendingHosts = pendingHostsConsistentMap.asJavaMap();
-
-        hostProbeIndex = storageService.atomicCounterBuilder()
-            .withName("onos-hosts-probe-index")
-            .build()
-            .asAtomicCounter();
-
-        cacheCleaner = newSingleThreadScheduledExecutor(groupedThreads("onos/hosts", "cache-cleaner", log));
-        cacheCleaner.scheduleAtFixedRate(pendingHostsCache::cleanUp, 0, PROBE_TIMEOUT_MS, TimeUnit.MILLISECONDS);
-
-        locationRemover = newSingleThreadScheduledExecutor(groupedThreads("onos/hosts", "loc-remover", log));
-
         executor = newSingleThreadScheduledExecutor(groupedThreads("onos/hosts", "status-listener", log));
         statusChangeListener = status -> {
             if (status == Status.ACTIVE) {
@@ -182,9 +121,6 @@
     @Deactivate
     public void deactivate() {
         hostsConsistentMap.removeListener(hostLocationTracker);
-
-        cacheCleaner.shutdown();
-        locationRemover.shutdown();
         executor.shutdown();
 
         log.info("Stopped");
@@ -425,41 +361,6 @@
         return ImmutableSet.copyOf(filtered);
     }
 
-    @Override
-    public MacAddress addPendingHostLocation(HostId hostId, ConnectPoint connectPoint, ProbeMode probeMode) {
-        // Use ONLab OUI (3 bytes) + atomic counter (3 bytes) as the source MAC of the probe
-        long nextIndex = hostProbeIndex.getAndIncrement();
-        MacAddress probeMac = MacAddress.valueOf(MacAddress.NONE.toLong() + nextIndex);
-        PendingHostLocation phl = new PendingHostLocation(hostId, connectPoint, probeMode);
-
-        pendingHostsCache.put(probeMac, phl);
-        pendingHosts.put(probeMac, phl);
-
-        return probeMac;
-    }
-
-    @Override
-    public void removePendingHostLocation(MacAddress probeMac) {
-        // Add the host location if probe replied in-time in DISCOVER mode
-        Optional.ofNullable(pendingHosts.get(probeMac)).ifPresent(phl -> {
-            if (phl.probeMode() == ProbeMode.DISCOVER) {
-                HostLocation newLocation = new HostLocation(phl.connectPoint(), System.currentTimeMillis());
-                appendLocation(phl.hostId(), newLocation);
-            }
-        });
-
-        pendingHostsCache.invalidate(probeMac);
-        pendingHosts.remove(probeMac);
-    }
-
-    private boolean timeoutPendingHostLocation(MacAddress probeMac) {
-        PendingHostLocation phl = pendingHosts.computeIfPresent(probeMac, (k, v) -> {
-            v.setExpired(true);
-            return v;
-        });
-        return phl != null;
-    }
-
     private Set<Host> filter(Collection<DefaultHost> collection, Predicate<DefaultHost> predicate) {
         return collection.stream().filter(predicate).collect(Collectors.toSet());
     }
@@ -543,29 +444,4 @@
             }
         }
     }
-
-    private class PendingHostListener implements MapEventListener<MacAddress, PendingHostLocation> {
-        @Override
-        public void event(MapEvent<MacAddress, PendingHostLocation> event) {
-            Versioned<PendingHostLocation> newValue = event.newValue();
-            switch (event.type()) {
-                case INSERT:
-                    break;
-                case UPDATE:
-                    // Remove the host location if probe timeout in VERIFY mode
-                    if (newValue.value().expired() && newValue.value().probeMode() == ProbeMode.VERIFY) {
-                        locationRemover.execute(() -> {
-                            pendingHosts.remove(event.key());
-                            removeLocation(newValue.value().hostId(),
-                                    new HostLocation(newValue.value().connectPoint(), 0L));
-                        });
-                    }
-                    break;
-                case REMOVE:
-                    break;
-                default:
-                    log.warn("Unknown map event type: {}", event.type());
-            }
-        }
-    }
 }
diff --git a/core/store/dist/src/main/java/org/onosproject/store/host/impl/PendingHostLocation.java b/core/store/dist/src/main/java/org/onosproject/store/host/impl/PendingHostLocation.java
deleted file mode 100644
index dc10507..0000000
--- a/core/store/dist/src/main/java/org/onosproject/store/host/impl/PendingHostLocation.java
+++ /dev/null
@@ -1,123 +0,0 @@
-/*
- * Copyright 2017-present Open Networking Foundation
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.onosproject.store.host.impl;
-
-import org.onosproject.net.ConnectPoint;
-import org.onosproject.net.HostId;
-import org.onosproject.net.host.HostLocationProbingService.ProbeMode;
-
-import java.util.Objects;
-
-import static com.google.common.base.MoreObjects.toStringHelper;
-
-/**
- * Internal data structure to record the info of a host with location that is under verification.
- */
-class PendingHostLocation {
-    private HostId hostId;
-    private ConnectPoint connectPoint;
-    private boolean expired;
-    private ProbeMode probeMode;
-
-    /**
-     * Constructs PendingHostLocation.
-     *
-     * @param hostId Host ID
-     * @param connectPoint location to be verified
-     * @param probeMode probe mode
-     */
-    PendingHostLocation(HostId hostId, ConnectPoint connectPoint, ProbeMode probeMode) {
-        this.hostId = hostId;
-        this.connectPoint = connectPoint;
-        this.expired = false;
-        this.probeMode = probeMode;
-    }
-
-    /**
-     * Gets HostId of this entry.
-     *
-     * @return host id
-     */
-    HostId hostId() {
-        return hostId;
-    }
-
-    /**
-     * Gets connect point of this entry.
-     *
-     * @return connect point
-     */
-    ConnectPoint connectPoint() {
-        return connectPoint;
-    }
-
-    /**
-     * Determine whether this probe is expired or not.
-     *
-     * @return true if this entry is expired and waiting to be removed from the cache
-     */
-    boolean expired() {
-        return expired;
-    }
-
-    /**
-     * Sets whether this probe is expired or not.
-     *
-     * @param expired true if this entry is expired and waiting to be removed from the cache
-     */
-    void setExpired(boolean expired) {
-        this.expired = expired;
-    }
-
-    /**
-     * Gets probe mode of this entry.
-     *
-     * @return probe mode
-     */
-    ProbeMode probeMode() {
-        return probeMode;
-    }
-
-    @Override
-    public boolean equals(Object o) {
-        if (this == o) {
-            return true;
-        }
-        if (!(o instanceof PendingHostLocation)) {
-            return false;
-        }
-        PendingHostLocation that = (PendingHostLocation) o;
-        return (Objects.equals(this.hostId, that.hostId) &&
-                Objects.equals(this.connectPoint, that.connectPoint) &&
-                Objects.equals(this.expired, that.expired) &&
-                Objects.equals(this.probeMode, that.probeMode));
-    }
-    @Override
-    public int hashCode() {
-        return Objects.hash(hostId, connectPoint, expired, probeMode);
-    }
-
-    @Override
-    public String toString() {
-        return toStringHelper(getClass())
-                .add("hostId", hostId)
-                .add("location", connectPoint)
-                .add("expired", expired)
-                .add("probeMode", probeMode)
-                .toString();
-    }
-}