diff --git a/apps/foo/src/main/java/org/onlab/onos/foo/FooComponent.java b/apps/foo/src/main/java/org/onlab/onos/foo/FooComponent.java
index f7f6478..117a9a0 100644
--- a/apps/foo/src/main/java/org/onlab/onos/foo/FooComponent.java
+++ b/apps/foo/src/main/java/org/onlab/onos/foo/FooComponent.java
@@ -23,6 +23,10 @@
 import org.onlab.onos.cluster.ClusterEvent;
 import org.onlab.onos.cluster.ClusterEventListener;
 import org.onlab.onos.cluster.ClusterService;
+import org.onlab.onos.cluster.NodeId;
+import org.onlab.onos.mastership.MastershipEvent;
+import org.onlab.onos.mastership.MastershipListener;
+import org.onlab.onos.mastership.MastershipService;
 import org.onlab.onos.net.device.DeviceEvent;
 import org.onlab.onos.net.device.DeviceListener;
 import org.onlab.onos.net.device.DeviceService;
@@ -50,15 +54,20 @@
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
     protected IntentService intentService;
 
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected MastershipService mastershipService;
+
     private final ClusterEventListener clusterListener = new InnerClusterListener();
     private final DeviceListener deviceListener = new InnerDeviceListener();
     private final IntentListener intentListener = new InnerIntentListener();
+    private final MastershipListener mastershipListener = new InnerMastershipListener();
 
     @Activate
     public void activate() {
         clusterService.addListener(clusterListener);
         deviceService.addListener(deviceListener);
         intentService.addListener(intentListener);
+        mastershipService.addListener(mastershipListener);
         log.info("Started");
     }
 
@@ -67,6 +76,7 @@
         clusterService.removeListener(clusterListener);
         deviceService.removeListener(deviceListener);
         intentService.removeListener(intentListener);
+        mastershipService.removeListener(mastershipListener);
         log.info("Stopped");
     }
 
@@ -100,6 +110,18 @@
             log.info(message, event.subject());
         }
     }
+
+    private class InnerMastershipListener implements MastershipListener {
+        @Override
+        public void event(MastershipEvent event) {
+            final NodeId myId = clusterService.getLocalNode().id();
+            if (myId.equals(event.roleInfo().master())) {
+                log.info("I have control/I wish you luck {}", event);
+            } else {
+                log.info("you have control {}", event);
+            }
+        }
+    }
 }
 
 
diff --git a/cli/src/main/java/org/onlab/onos/cli/net/AddHostToHostIntentCommand.java b/cli/src/main/java/org/onlab/onos/cli/net/AddHostToHostIntentCommand.java
index 7d3bfc2..13f3000 100644
--- a/cli/src/main/java/org/onlab/onos/cli/net/AddHostToHostIntentCommand.java
+++ b/cli/src/main/java/org/onlab/onos/cli/net/AddHostToHostIntentCommand.java
@@ -15,14 +15,16 @@
  */
 package org.onlab.onos.cli.net;
 
+import java.util.List;
+
 import org.apache.karaf.shell.commands.Argument;
 import org.apache.karaf.shell.commands.Command;
-import org.onlab.onos.cli.AbstractShellCommand;
 import org.onlab.onos.net.HostId;
 import org.onlab.onos.net.flow.DefaultTrafficSelector;
 import org.onlab.onos.net.flow.DefaultTrafficTreatment;
 import org.onlab.onos.net.flow.TrafficSelector;
 import org.onlab.onos.net.flow.TrafficTreatment;
+import org.onlab.onos.net.intent.Constraint;
 import org.onlab.onos.net.intent.HostToHostIntent;
 import org.onlab.onos.net.intent.IntentService;
 
@@ -31,7 +33,7 @@
  */
 @Command(scope = "onos", name = "add-host-intent",
          description = "Installs host-to-host connectivity intent")
-public class AddHostToHostIntentCommand extends AbstractShellCommand {
+public class AddHostToHostIntentCommand extends ConnectivityIntentCommand {
 
     @Argument(index = 0, name = "one", description = "One host ID",
               required = true, multiValued = false)
@@ -50,9 +52,11 @@
 
         TrafficSelector selector = DefaultTrafficSelector.builder().build();
         TrafficTreatment treatment = DefaultTrafficTreatment.builder().build();
+        List<Constraint> constraints = buildConstraints();
 
         HostToHostIntent intent = new HostToHostIntent(appId(), oneId, twoId,
-                                                       selector, treatment);
+                                                       selector, treatment,
+                                                       constraints);
         service.submit(intent);
     }
 
diff --git a/cli/src/main/java/org/onlab/onos/cli/net/AddMultiPointToSinglePointIntentCommand.java b/cli/src/main/java/org/onlab/onos/cli/net/AddMultiPointToSinglePointIntentCommand.java
index 9e8e2fc..1cd695e 100644
--- a/cli/src/main/java/org/onlab/onos/cli/net/AddMultiPointToSinglePointIntentCommand.java
+++ b/cli/src/main/java/org/onlab/onos/cli/net/AddMultiPointToSinglePointIntentCommand.java
@@ -23,11 +23,13 @@
 import org.onlab.onos.net.flow.DefaultTrafficTreatment;
 import org.onlab.onos.net.flow.TrafficSelector;
 import org.onlab.onos.net.flow.TrafficTreatment;
+import org.onlab.onos.net.intent.Constraint;
 import org.onlab.onos.net.intent.Intent;
 import org.onlab.onos.net.intent.IntentService;
 import org.onlab.onos.net.intent.MultiPointToSinglePointIntent;
 
 import java.util.HashSet;
+import java.util.List;
 import java.util.Set;
 
 import static org.onlab.onos.net.DeviceId.deviceId;
@@ -69,9 +71,11 @@
 
         TrafficSelector selector = buildTrafficSelector();
         TrafficTreatment treatment = DefaultTrafficTreatment.builder().build();
+        List<Constraint> constraints = buildConstraints();
 
         Intent intent = new MultiPointToSinglePointIntent(appId(), selector, treatment,
-                                                          ingressPoints, egress);
+                                                          ingressPoints, egress,
+                                                          constraints);
         service.submit(intent);
     }
 
diff --git a/cli/src/main/java/org/onlab/onos/cli/net/AddPointToPointIntentCommand.java b/cli/src/main/java/org/onlab/onos/cli/net/AddPointToPointIntentCommand.java
index ed98c7e..26bb1c0 100644
--- a/cli/src/main/java/org/onlab/onos/cli/net/AddPointToPointIntentCommand.java
+++ b/cli/src/main/java/org/onlab/onos/cli/net/AddPointToPointIntentCommand.java
@@ -15,6 +15,8 @@
  */
 package org.onlab.onos.cli.net;
 
+import java.util.List;
+
 import org.apache.karaf.shell.commands.Argument;
 import org.apache.karaf.shell.commands.Command;
 import org.onlab.onos.net.ConnectPoint;
@@ -22,6 +24,7 @@
 import org.onlab.onos.net.PortNumber;
 import org.onlab.onos.net.flow.TrafficSelector;
 import org.onlab.onos.net.flow.TrafficTreatment;
+import org.onlab.onos.net.intent.Constraint;
 import org.onlab.onos.net.intent.Intent;
 import org.onlab.onos.net.intent.IntentService;
 import org.onlab.onos.net.intent.PointToPointIntent;
@@ -63,8 +66,10 @@
         TrafficSelector selector = buildTrafficSelector();
         TrafficTreatment treatment = builder().build();
 
+        List<Constraint> constraints = buildConstraints();
+
         Intent intent = new PointToPointIntent(appId(), selector, treatment,
-                                               ingress, egress);
+                                               ingress, egress, constraints);
         service.submit(intent);
     }
 
diff --git a/cli/src/main/java/org/onlab/onos/cli/net/ConnectivityIntentCommand.java b/cli/src/main/java/org/onlab/onos/cli/net/ConnectivityIntentCommand.java
index d8ec3c7..e4fc5aa 100644
--- a/cli/src/main/java/org/onlab/onos/cli/net/ConnectivityIntentCommand.java
+++ b/cli/src/main/java/org/onlab/onos/cli/net/ConnectivityIntentCommand.java
@@ -15,14 +15,21 @@
  */
 package org.onlab.onos.cli.net;
 
+import java.util.LinkedList;
+import java.util.List;
+
 import org.apache.karaf.shell.commands.Option;
 import org.onlab.onos.cli.AbstractShellCommand;
 import org.onlab.onos.net.flow.DefaultTrafficSelector;
 import org.onlab.onos.net.flow.TrafficSelector;
+import org.onlab.onos.net.intent.Constraint;
+import org.onlab.onos.net.intent.constraint.BandwidthConstraint;
+import org.onlab.onos.net.intent.constraint.LambdaConstraint;
+import org.onlab.onos.net.resource.Bandwidth;
 import org.onlab.packet.Ethernet;
 import org.onlab.packet.MacAddress;
 
-import com.google.common.base.Strings;
+import static com.google.common.base.Strings.isNullOrEmpty;
 
 /**
  * Base class for command line operations for connectivity based intents.
@@ -41,6 +48,14 @@
             required = false, multiValued = false)
     private String ethTypeString = "";
 
+    @Option(name = "-b", aliases = "--bandwidth", description = "Bandwidth",
+            required = false, multiValued = false)
+    private String bandwidthString = "";
+
+    @Option(name = "-l", aliases = "--lambda", description = "Lambda",
+            required = false, multiValued = false)
+    private boolean lambda = false;
+
     /**
      * Constructs a traffic selector based on the command line arguments
      * presented to the command.
@@ -50,21 +65,43 @@
         TrafficSelector.Builder selectorBuilder = DefaultTrafficSelector.builder();
         Short ethType = Ethernet.TYPE_IPV4;
 
-        if (!Strings.isNullOrEmpty(ethTypeString)) {
+        if (!isNullOrEmpty(ethTypeString)) {
             EthType ethTypeParameter = EthType.valueOf(ethTypeString);
             ethType = ethTypeParameter.value();
         }
         selectorBuilder.matchEthType(ethType);
 
-        if (!Strings.isNullOrEmpty(srcMacString)) {
+        if (!isNullOrEmpty(srcMacString)) {
             selectorBuilder.matchEthSrc(MacAddress.valueOf(srcMacString));
         }
 
-        if (!Strings.isNullOrEmpty(dstMacString)) {
+        if (!isNullOrEmpty(dstMacString)) {
             selectorBuilder.matchEthDst(MacAddress.valueOf(dstMacString));
         }
 
         return selectorBuilder.build();
     }
 
+    /**
+     * Builds the constraint list for this command based on the command line
+     * parameters.
+     *
+     * @return List of constraint objects describing the constraints requested
+     */
+    protected List<Constraint> buildConstraints() {
+        final List<Constraint> constraints = new LinkedList<>();
+
+        // Check for a bandwidth specification
+        if (!isNullOrEmpty(bandwidthString)) {
+            final double bandwidthValue = Double.parseDouble(bandwidthString);
+            constraints.add(new BandwidthConstraint(Bandwidth.valueOf(bandwidthValue)));
+        }
+
+        // Check for a lambda specification
+        if (lambda) {
+            constraints.add(new LambdaConstraint(null));
+        }
+
+        return constraints;
+    }
 }
diff --git a/core/api/src/main/java/org/onlab/onos/net/intent/HostToHostIntent.java b/core/api/src/main/java/org/onlab/onos/net/intent/HostToHostIntent.java
index 3fad93d..893270a 100644
--- a/core/api/src/main/java/org/onlab/onos/net/intent/HostToHostIntent.java
+++ b/core/api/src/main/java/org/onlab/onos/net/intent/HostToHostIntent.java
@@ -105,6 +105,7 @@
                 .add("appId", appId())
                 .add("selector", selector())
                 .add("treatment", treatment())
+                .add("constraints", constraints())
                 .add("one", one)
                 .add("two", two)
                 .toString();
diff --git a/core/api/src/main/java/org/onlab/onos/net/intent/MultiPointToSinglePointIntent.java b/core/api/src/main/java/org/onlab/onos/net/intent/MultiPointToSinglePointIntent.java
index 0c47aad..90907fb 100644
--- a/core/api/src/main/java/org/onlab/onos/net/intent/MultiPointToSinglePointIntent.java
+++ b/core/api/src/main/java/org/onlab/onos/net/intent/MultiPointToSinglePointIntent.java
@@ -22,6 +22,7 @@
 import org.onlab.onos.net.flow.TrafficSelector;
 import org.onlab.onos.net.flow.TrafficTreatment;
 
+import java.util.List;
 import java.util.Set;
 
 import static com.google.common.base.Preconditions.checkArgument;
@@ -65,6 +66,38 @@
     }
 
     /**
+     * Creates a new multi-to-single point connectivity intent for the specified
+     * traffic selector and treatment.
+     *
+     * @param appId         application identifier
+     * @param selector      traffic selector
+     * @param treatment     treatment
+     * @param ingressPoints set of ports from which ingress traffic originates
+     * @param egressPoint   port to which traffic will egress
+     * @param constraints   constraints to apply to the intent
+     * @throws NullPointerException     if {@code ingressPoints} or
+     *                                  {@code egressPoint} is null.
+     * @throws IllegalArgumentException if the size of {@code ingressPoints} is
+     *                                  not more than 1
+     */
+    public MultiPointToSinglePointIntent(ApplicationId appId,
+                                         TrafficSelector selector,
+                                         TrafficTreatment treatment,
+                                         Set<ConnectPoint> ingressPoints,
+                                         ConnectPoint egressPoint,
+                                         List<Constraint> constraints) {
+        super(id(MultiPointToSinglePointIntent.class, selector, treatment,
+                ingressPoints, egressPoint), appId, null, selector, treatment,
+                constraints);
+
+        checkNotNull(ingressPoints);
+        checkArgument(!ingressPoints.isEmpty(), "Ingress point set cannot be empty");
+
+        this.ingressPoints = Sets.newHashSet(ingressPoints);
+        this.egressPoint = checkNotNull(egressPoint);
+    }
+
+    /**
      * Constructor for serializer.
      */
     protected MultiPointToSinglePointIntent() {
@@ -101,6 +134,7 @@
                 .add("treatment", treatment())
                 .add("ingress", ingressPoints())
                 .add("egress", egressPoint())
+                .add("constraints", constraints())
                 .toString();
     }
 }
diff --git a/core/api/src/main/java/org/onlab/onos/net/intent/PathIntent.java b/core/api/src/main/java/org/onlab/onos/net/intent/PathIntent.java
index 9189bae..9f8816d 100644
--- a/core/api/src/main/java/org/onlab/onos/net/intent/PathIntent.java
+++ b/core/api/src/main/java/org/onlab/onos/net/intent/PathIntent.java
@@ -15,6 +15,8 @@
  */
 package org.onlab.onos.net.intent;
 
+import java.util.List;
+
 import com.google.common.base.MoreObjects;
 import org.onlab.onos.core.ApplicationId;
 import org.onlab.onos.net.Path;
@@ -46,6 +48,24 @@
     }
 
     /**
+     * Creates a new point-to-point intent with the supplied ingress/egress
+     * ports and using the specified explicit path.
+     *
+     * @param appId     application identifier
+     * @param selector  traffic selector
+     * @param treatment treatment
+     * @param path      traversed links
+     * @param constraints  optional list of constraints
+     * @throws NullPointerException {@code path} is null
+     */
+    public PathIntent(ApplicationId appId, TrafficSelector selector,
+                      TrafficTreatment treatment, Path path, List<Constraint> constraints) {
+        super(id(PathIntent.class, selector, treatment, path, constraints), appId,
+                resources(path.links()), selector, treatment, constraints);
+        this.path = path;
+    }
+
+    /**
      * Constructor for serializer.
      */
     protected PathIntent() {
@@ -75,6 +95,7 @@
                 .add("appId", appId())
                 .add("selector", selector())
                 .add("treatment", treatment())
+                .add("constraints", constraints())
                 .add("path", path)
                 .toString();
     }
diff --git a/core/net/src/main/java/org/onlab/onos/net/intent/impl/ConnectivityIntentCompiler.java b/core/net/src/main/java/org/onlab/onos/net/intent/impl/ConnectivityIntentCompiler.java
index 4cf1830..8a31900 100644
--- a/core/net/src/main/java/org/onlab/onos/net/intent/impl/ConnectivityIntentCompiler.java
+++ b/core/net/src/main/java/org/onlab/onos/net/intent/impl/ConnectivityIntentCompiler.java
@@ -118,13 +118,14 @@
 
         @Override
         public double weight(TopologyEdge edge) {
-            if (constraints == null) {
+            if (constraints == null || !constraints.iterator().hasNext()) {
                 return 1.0;
             }
 
             // iterate over all constraints in order and return the weight of
             // the first one with fast fail over the first failure
             Iterator<Constraint> it = constraints.iterator();
+
             double cost = it.next().cost(edge.link(), resourceService);
             while (it.hasNext() && cost > 0) {
                 if (it.next().cost(edge.link(), resourceService) < 0) {
@@ -132,6 +133,7 @@
                 }
             }
             return cost;
+
         }
     }
 
diff --git a/core/net/src/main/java/org/onlab/onos/net/intent/impl/HostToHostIntentCompiler.java b/core/net/src/main/java/org/onlab/onos/net/intent/impl/HostToHostIntentCompiler.java
index 605d3c7..4d989ac 100644
--- a/core/net/src/main/java/org/onlab/onos/net/intent/impl/HostToHostIntentCompiler.java
+++ b/core/net/src/main/java/org/onlab/onos/net/intent/impl/HostToHostIntentCompiler.java
@@ -70,7 +70,8 @@
                                     HostToHostIntent intent) {
         TrafficSelector selector = builder(intent.selector())
                 .matchEthSrc(src.mac()).matchEthDst(dst.mac()).build();
-        return new PathIntent(intent.appId(), selector, intent.treatment(), path);
+        return new PathIntent(intent.appId(), selector, intent.treatment(),
+                              path, intent.constraints());
     }
 
 }
diff --git a/core/net/src/main/java/org/onlab/onos/net/intent/impl/IntentManager.java b/core/net/src/main/java/org/onlab/onos/net/intent/impl/IntentManager.java
index 31df87a..af2af24 100644
--- a/core/net/src/main/java/org/onlab/onos/net/intent/impl/IntentManager.java
+++ b/core/net/src/main/java/org/onlab/onos/net/intent/impl/IntentManager.java
@@ -77,7 +77,7 @@
 @Service
 public class IntentManager
         implements IntentService, IntentExtensionService {
-    private final Logger log = getLogger(getClass());
+    private static final Logger log = getLogger(IntentManager.class);
 
     public static final String INTENT_NULL = "Intent cannot be null";
     public static final String INTENT_ID_NULL = "Intent ID cannot be null";
diff --git a/core/net/src/main/java/org/onlab/onos/net/intent/impl/PointToPointIntentCompiler.java b/core/net/src/main/java/org/onlab/onos/net/intent/impl/PointToPointIntentCompiler.java
index c32c8ee..5c8eb94 100644
--- a/core/net/src/main/java/org/onlab/onos/net/intent/impl/PointToPointIntentCompiler.java
+++ b/core/net/src/main/java/org/onlab/onos/net/intent/impl/PointToPointIntentCompiler.java
@@ -77,7 +77,8 @@
     private Intent createPathIntent(Path path,
                                     PointToPointIntent intent) {
         return new PathIntent(intent.appId(),
-                              intent.selector(), intent.treatment(), path);
+                              intent.selector(), intent.treatment(), path,
+                              intent.constraints());
     }
 
 }
diff --git a/core/net/src/test/java/org/onlab/onos/cluster/impl/MastershipManagerTest.java b/core/net/src/test/java/org/onlab/onos/cluster/impl/MastershipManagerTest.java
index ddd805f..33961e4 100644
--- a/core/net/src/test/java/org/onlab/onos/cluster/impl/MastershipManagerTest.java
+++ b/core/net/src/test/java/org/onlab/onos/cluster/impl/MastershipManagerTest.java
@@ -28,6 +28,7 @@
 import org.onlab.onos.cluster.NodeId;
 import org.onlab.onos.event.impl.TestEventDispatcher;
 import org.onlab.onos.mastership.MastershipService;
+import org.onlab.onos.mastership.MastershipStore;
 import org.onlab.onos.mastership.MastershipTermService;
 import org.onlab.onos.net.DeviceId;
 import org.onlab.onos.store.trivial.impl.SimpleMastershipStore;
@@ -57,9 +58,9 @@
     public void setUp() {
         mgr = new MastershipManager();
         service = mgr;
-        mgr.store = new SimpleMastershipStore();
         mgr.eventDispatcher = new TestEventDispatcher();
         mgr.clusterService = new TestClusterService();
+        mgr.store = new TestSimpleMastershipStore(mgr.clusterService);
         mgr.activate();
     }
 
@@ -74,7 +75,8 @@
     @Test
     public void setRole() {
         mgr.setRole(NID_OTHER, DEV_MASTER, MASTER);
-        assertEquals("wrong local role:", STANDBY, mgr.getLocalRole(DEV_MASTER));
+        assertEquals("wrong local role:", NONE, mgr.getLocalRole(DEV_MASTER));
+        assertEquals("wrong obtained role:", STANDBY, mgr.requestRoleFor(DEV_MASTER));
 
         //set to master
         mgr.setRole(NID_LOCAL, DEV_MASTER, MASTER);
@@ -182,4 +184,12 @@
         }
 
     }
+
+    private final class TestSimpleMastershipStore extends SimpleMastershipStore
+            implements MastershipStore {
+
+        public TestSimpleMastershipStore(ClusterService clusterService) {
+            super.clusterService = clusterService;
+        }
+    }
 }
diff --git a/core/store/dist/pom.xml b/core/store/dist/pom.xml
index 248e763..f0f37c7 100644
--- a/core/store/dist/pom.xml
+++ b/core/store/dist/pom.xml
@@ -64,6 +64,12 @@
 -->
 
         <dependency>
+            <groupId>org.mapdb</groupId>
+            <artifactId>mapdb</artifactId>
+            <version>1.0.6</version>
+        </dependency>
+
+        <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-databind</artifactId>
         </dependency>
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/mastership/impl/DistributedMastershipStore.java b/core/store/dist/src/main/java/org/onlab/onos/store/mastership/impl/DistributedMastershipStore.java
index 42e0799..6c2ad6a 100644
--- a/core/store/dist/src/main/java/org/onlab/onos/store/mastership/impl/DistributedMastershipStore.java
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/mastership/impl/DistributedMastershipStore.java
@@ -283,16 +283,15 @@
                 case MASTER:
                     NodeId newMaster = reelect(nodeId, deviceId, rv);
                     rv.reassign(nodeId, NONE, STANDBY);
+                    updateTerm(deviceId);
                     if (newMaster != null) {
-                        updateTerm(deviceId);
                         roleMap.put(deviceId, rv);
                         return new MastershipEvent(MASTER_CHANGED, deviceId, rv.roleInfo());
                     } else {
                         // no master candidate
                         roleMap.put(deviceId, rv);
-                        // FIXME: Should there be new event type?
-                        // or should we issue null Master event?
-                        return null;
+                        // TODO: Should there be new event type for no MASTER?
+                        return new MastershipEvent(MASTER_CHANGED, deviceId, rv.roleInfo());
                     }
                 case STANDBY:
                     return null;
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/service/ReadRequest.java b/core/store/dist/src/main/java/org/onlab/onos/store/service/ReadRequest.java
index a22464a..9f7af4a 100644
--- a/core/store/dist/src/main/java/org/onlab/onos/store/service/ReadRequest.java
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/service/ReadRequest.java
@@ -1,5 +1,9 @@
 package org.onlab.onos.store.service;
 
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import java.util.Objects;
+
 import com.google.common.base.MoreObjects;
 
 /**
@@ -10,9 +14,21 @@
     private final String tableName;
     private final String key;
 
+    /**
+     * Creates a read request,
+     * which will retrieve the specified key from the table.
+     *
+     * @param tableName name of the table
+     * @param key       key in the table
+     * @return ReadRequest
+     */
+    public static ReadRequest get(String tableName, String key) {
+        return new ReadRequest(tableName, key);
+    }
+
     public ReadRequest(String tableName, String key) {
-        this.tableName = tableName;
-        this.key = key;
+        this.tableName = checkNotNull(tableName);
+        this.key = checkNotNull(key);
     }
 
     /**
@@ -38,4 +54,26 @@
                 .add("key", key)
                 .toString();
     }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(key, tableName);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj == null) {
+            return false;
+        }
+        if (getClass() != obj.getClass()) {
+            return false;
+        }
+        ReadRequest other = (ReadRequest) obj;
+        return Objects.equals(this.key, other.key) &&
+                Objects.equals(this.tableName, other.tableName);
+    }
+
 }
\ No newline at end of file
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/service/VersionedValue.java b/core/store/dist/src/main/java/org/onlab/onos/store/service/VersionedValue.java
index 852fb07..ae6969c 100644
--- a/core/store/dist/src/main/java/org/onlab/onos/store/service/VersionedValue.java
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/service/VersionedValue.java
@@ -38,6 +38,28 @@
         return version;
     }
 
+    /**
+     * Creates a copy of given VersionedValue.
+     *
+     * @param original VersionedValue to create a copy
+     * @return same as original if original or it's value is null,
+     *         otherwise creates a copy.
+     */
+    public static VersionedValue copy(VersionedValue original) {
+        if (original == null) {
+            return null;
+        }
+        if (original.value == null) {
+            // immutable, no need to copy
+            return original;
+        } else {
+            return new VersionedValue(
+                                      Arrays.copyOf(original.value,
+                                                    original.value.length),
+                                      original.version);
+        }
+    }
+
     @Override
     public String toString() {
         return MoreObjects.toStringHelper(getClass())
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/ClusterMessagingProtocolClient.java b/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/ClusterMessagingProtocolClient.java
index 0c2aacd..582e00c 100644
--- a/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/ClusterMessagingProtocolClient.java
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/ClusterMessagingProtocolClient.java
@@ -132,8 +132,8 @@
             } catch (IOException | InterruptedException | ExecutionException | TimeoutException e) {
                 if (message.subject().equals(ClusterMessagingProtocol.COPYCAT_SYNC) ||
                         message.subject().equals(ClusterMessagingProtocol.COPYCAT_PING)) {
-                    log.warn("Request to {} failed. Will retry "
-                            + "in {} ms", remoteNode, RETRY_INTERVAL_MILLIS);
+                    log.warn("{} Request to {} failed. Will retry in {} ms",
+                             message.subject(), remoteNode, RETRY_INTERVAL_MILLIS);
                     THREAD_POOL.schedule(
                             this,
                             RETRY_INTERVAL_MILLIS,
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/ClusterMessagingProtocolServer.java b/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/ClusterMessagingProtocolServer.java
index 7d94847..b3eaeb4 100644
--- a/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/ClusterMessagingProtocolServer.java
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/ClusterMessagingProtocolServer.java
@@ -3,12 +3,17 @@
 import static org.slf4j.LoggerFactory.getLogger;
 
 import java.util.concurrent.CompletableFuture;
+import java.util.function.BiConsumer;
 
 import net.kuujo.copycat.protocol.PingRequest;
+import net.kuujo.copycat.protocol.PingResponse;
 import net.kuujo.copycat.protocol.PollRequest;
+import net.kuujo.copycat.protocol.PollResponse;
 import net.kuujo.copycat.protocol.RequestHandler;
 import net.kuujo.copycat.protocol.SubmitRequest;
+import net.kuujo.copycat.protocol.SubmitResponse;
 import net.kuujo.copycat.protocol.SyncRequest;
+import net.kuujo.copycat.protocol.SyncResponse;
 import net.kuujo.copycat.spi.protocol.ProtocolServer;
 
 import org.onlab.onos.store.cluster.messaging.ClusterCommunicationService;
@@ -57,37 +62,37 @@
         public void handle(ClusterMessage message) {
             T request = ClusterMessagingProtocol.SERIALIZER.decode(message.payload());
             if (request.getClass().equals(PingRequest.class)) {
-                handler.ping((PingRequest) request).whenComplete((response, error) -> {
-                    try {
-                        message.respond(ClusterMessagingProtocol.SERIALIZER.encode(response));
-                    } catch (Exception e) {
-                        log.error("Failed to respond to ping request", e);
-                    }
-                });
+                handler.ping((PingRequest) request).whenComplete(new PostExecutionTask<PingResponse>(message));
             } else if (request.getClass().equals(PollRequest.class)) {
-                handler.poll((PollRequest) request).whenComplete((response, error) -> {
-                    try {
-                        message.respond(ClusterMessagingProtocol.SERIALIZER.encode(response));
-                    } catch (Exception e) {
-                        log.error("Failed to respond to poll request", e);
-                    }
-                });
+                handler.poll((PollRequest) request).whenComplete(new PostExecutionTask<PollResponse>(message));
             } else if (request.getClass().equals(SyncRequest.class)) {
-                handler.sync((SyncRequest) request).whenComplete((response, error) -> {
-                    try {
-                        message.respond(ClusterMessagingProtocol.SERIALIZER.encode(response));
-                    } catch (Exception e) {
-                        log.error("Failed to respond to sync request", e);
-                    }
-                });
+                handler.sync((SyncRequest) request).whenComplete(new PostExecutionTask<SyncResponse>(message));
             } else if (request.getClass().equals(SubmitRequest.class)) {
-                handler.submit((SubmitRequest) request).whenComplete((response, error) -> {
+                handler.submit((SubmitRequest) request).whenComplete(new PostExecutionTask<SubmitResponse>(message));
+            } else {
+                throw new IllegalStateException("Unknown request type: " + request.getClass().getName());
+            }
+        }
+
+        private class PostExecutionTask<R> implements BiConsumer<R, Throwable> {
+
+            private final ClusterMessage message;
+
+            public PostExecutionTask(ClusterMessage message) {
+                this.message = message;
+            }
+
+            @Override
+            public void accept(R response, Throwable t) {
+                if (t != null) {
+                    log.error("Processing for " + message.subject() + " failed.", t);
+                } else {
                     try {
                         message.respond(ClusterMessagingProtocol.SERIALIZER.encode(response));
                     } catch (Exception e) {
-                        log.error("Failed to respond to submit request", e);
+                        log.error("Failed to respond to " + response.getClass().getName(), e);
                     }
-                });
+                }
             }
         }
     }
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/DatabaseStateMachine.java b/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/DatabaseStateMachine.java
index 2822f25..9662976 100644
--- a/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/DatabaseStateMachine.java
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/DatabaseStateMachine.java
@@ -5,8 +5,6 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
-import java.util.Set;
-
 import net.kuujo.copycat.Command;
 import net.kuujo.copycat.Query;
 import net.kuujo.copycat.StateMachine;
@@ -20,6 +18,7 @@
 import org.onlab.util.KryoNamespace;
 import org.slf4j.Logger;
 
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Maps;
 
 /**
@@ -64,8 +63,8 @@
     }
 
     @Query
-    public Set<String> listTables() {
-        return state.getTables().keySet();
+    public List<String> listTables() {
+        return ImmutableList.copyOf(state.getTables().keySet());
     }
 
     @Query
@@ -77,7 +76,7 @@
                 results.add(new InternalReadResult(InternalReadResult.Status.NO_SUCH_TABLE, null));
                 continue;
             }
-            VersionedValue value = table.get(request.key());
+            VersionedValue value = VersionedValue.copy(table.get(request.key()));
             results.add(new InternalReadResult(
                     InternalReadResult.Status.OK,
                     new ReadResult(
@@ -90,6 +89,8 @@
 
     @Command
     public List<InternalWriteResult> write(List<WriteRequest> requests) {
+
+        // applicability check
         boolean abort = false;
         List<InternalWriteResult.Status> validationResults = new ArrayList<>(requests.size());
         for (WriteRequest request : requests) {
@@ -133,8 +134,13 @@
             return results;
         }
 
+        // apply changes
         for (WriteRequest request : requests) {
             Map<String, VersionedValue> table = state.getTables().get(request.tableName());
+            // FIXME: If this method could be called by multiple thread,
+            // synchronization scope is wrong.
+            // Whole function including applicability check needs to be protected.
+            // Confirm copycat's thread safety requirement for StateMachine
             synchronized (table) {
                 VersionedValue previousValue =
                         table.put(request.key(), new VersionedValue(request.newValue(), state.nextVersion()));
@@ -166,8 +172,8 @@
         try {
             return SERIALIZER.encode(state);
         } catch (Exception e) {
-            log.error("Snapshot serialization error", e);
-            return null;
+            log.error("Failed to take snapshot", e);
+            throw new SnapshotException(e);
         }
     }
 
@@ -176,7 +182,8 @@
         try {
             this.state = SERIALIZER.decode(data);
         } catch (Exception e) {
-            log.error("Snapshot deserialization error", e);
+            log.error("Failed to install from snapshot", e);
+            throw new SnapshotException(e);
         }
     }
 }
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/MapDBLog.java b/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/MapDBLog.java
new file mode 100644
index 0000000..893c311
--- /dev/null
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/MapDBLog.java
@@ -0,0 +1,280 @@
+package org.onlab.onos.store.service.impl;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkState;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.concurrent.ConcurrentNavigableMap;
+
+import net.kuujo.copycat.log.Entry;
+import net.kuujo.copycat.log.Log;
+import net.kuujo.copycat.log.LogIndexOutOfBoundsException;
+
+import org.mapdb.Atomic;
+import org.mapdb.BTreeMap;
+import org.mapdb.DB;
+import org.mapdb.DBMaker;
+import org.mapdb.TxBlock;
+import org.mapdb.TxMaker;
+import org.onlab.onos.store.serializers.StoreSerializer;
+
+import com.google.common.collect.Lists;
+
+/**
+ * MapDB based log implementation.
+ */
+public class MapDBLog implements Log {
+
+    private final File dbFile;
+    private TxMaker txMaker;
+    private final StoreSerializer serializer;
+    private static final String LOG_NAME = "log";
+    private static final String SIZE_FIELD_NAME = "size";
+
+    public MapDBLog(File dbFile, StoreSerializer serializer) {
+        this.dbFile = dbFile;
+        this.serializer = serializer;
+    }
+
+    @Override
+    public void open() throws IOException {
+        txMaker = DBMaker
+                .newFileDB(dbFile)
+                .makeTxMaker();
+    }
+
+    @Override
+    public void close() throws IOException {
+        assertIsOpen();
+        txMaker.close();
+        txMaker = null;
+    }
+
+    @Override
+    public boolean isOpen() {
+        return txMaker != null;
+    }
+
+    protected void assertIsOpen() {
+        checkState(isOpen(), "The log is not currently open.");
+    }
+
+    @Override
+    public long appendEntry(Entry entry) {
+        checkArgument(entry != null, "expecting non-null entry");
+        return appendEntries(entry).get(0);
+    }
+
+    @Override
+    public List<Long> appendEntries(Entry... entries) {
+        checkArgument(entries != null, "expecting non-null entries");
+        return appendEntries(Arrays.asList(entries));
+    }
+
+    @Override
+    public List<Long> appendEntries(List<Entry> entries) {
+        assertIsOpen();
+        checkArgument(entries != null, "expecting non-null entries");
+        final List<Long> indices = Lists.newArrayList();
+
+        txMaker.execute(new TxBlock() {
+            @Override
+            public void tx(DB db) {
+                BTreeMap<Long, byte[]> log = db.getTreeMap(LOG_NAME);
+                Atomic.Long size = db.getAtomicLong(SIZE_FIELD_NAME);
+                long nextIndex = log.isEmpty() ? 1 : log.lastKey() + 1;
+                for (Entry entry : entries) {
+                    byte[] entryBytes = serializer.encode(entry);
+                    log.put(nextIndex, entryBytes);
+                    size.addAndGet(entryBytes.length);
+                    indices.add(nextIndex);
+                    nextIndex++;
+                }
+            }
+        });
+
+        return indices;
+    }
+
+    @Override
+    public boolean containsEntry(long index) {
+        assertIsOpen();
+        DB db = txMaker.makeTx();
+        try {
+            BTreeMap<Long, byte[]> log = db.getTreeMap(LOG_NAME);
+            return log.containsKey(index);
+        } finally {
+            db.close();
+        }
+    }
+
+    @Override
+    public void delete() throws IOException {
+        assertIsOpen();
+        txMaker.execute(new TxBlock() {
+            @Override
+            public void tx(DB db) {
+                BTreeMap<Long, byte[]> log = db.getTreeMap(LOG_NAME);
+                Atomic.Long size = db.getAtomicLong(SIZE_FIELD_NAME);
+                log.clear();
+                size.set(0);
+            }
+        });
+    }
+
+    @Override
+    public <T extends Entry> T firstEntry() {
+        assertIsOpen();
+        DB db = txMaker.makeTx();
+        try {
+            BTreeMap<Long, byte[]> log = db.getTreeMap(LOG_NAME);
+            return log.isEmpty() ? null : serializer.decode(log.firstEntry().getValue());
+        } finally {
+            db.close();
+        }
+    }
+
+    @Override
+    public long firstIndex() {
+        assertIsOpen();
+        DB db = txMaker.makeTx();
+        try {
+            BTreeMap<Long, byte[]> log = db.getTreeMap(LOG_NAME);
+            return log.isEmpty() ? 0 : log.firstKey();
+        } finally {
+            db.close();
+        }
+    }
+
+    @Override
+    public <T extends Entry> List<T> getEntries(long from, long to) {
+        assertIsOpen();
+        DB db = txMaker.makeTx();
+        try {
+            BTreeMap<Long, byte[]> log = db.getTreeMap(LOG_NAME);
+            if (log.isEmpty()) {
+                throw new LogIndexOutOfBoundsException("Log is empty");
+            } else if (from < log.firstKey()) {
+                throw new LogIndexOutOfBoundsException("From index out of bounds.");
+            } else if (to > log.lastKey()) {
+                throw new LogIndexOutOfBoundsException("To index out of bounds.");
+            }
+            List<T> entries = new ArrayList<>((int) (to - from + 1));
+            for (long i = from; i <= to; i++) {
+                T entry = serializer.decode(log.get(i));
+                entries.add(entry);
+            }
+            return entries;
+        } finally {
+            db.close();
+        }
+    }
+
+    @Override
+    public <T extends Entry> T getEntry(long index) {
+        assertIsOpen();
+        DB db = txMaker.makeTx();
+        try {
+            BTreeMap<Long, byte[]> log = db.getTreeMap(LOG_NAME);
+            byte[] entryBytes = log.get(index);
+            return entryBytes == null ? null : serializer.decode(entryBytes);
+        } finally {
+            db.close();
+        }
+    }
+
+    @Override
+    public boolean isEmpty() {
+        assertIsOpen();
+        DB db = txMaker.makeTx();
+        try {
+            BTreeMap<Long, byte[]> log = db.getTreeMap(LOG_NAME);
+            return log.isEmpty();
+        } finally {
+            db.close();
+        }
+    }
+
+    @Override
+    public <T extends Entry> T lastEntry() {
+        assertIsOpen();
+        DB db = txMaker.makeTx();
+        try {
+            BTreeMap<Long, byte[]> log = db.getTreeMap(LOG_NAME);
+            return log.isEmpty() ? null : serializer.decode(log.lastEntry().getValue());
+        } finally {
+            db.close();
+        }
+    }
+
+    @Override
+    public long lastIndex() {
+        assertIsOpen();
+        DB db = txMaker.makeTx();
+        try {
+            BTreeMap<Long, byte[]> log = db.getTreeMap(LOG_NAME);
+            return log.isEmpty() ? 0 : log.lastKey();
+        } finally {
+            db.close();
+        }
+    }
+
+    @Override
+    public void removeAfter(long index) {
+        assertIsOpen();
+        txMaker.execute(new TxBlock() {
+            @Override
+            public void tx(DB db) {
+                BTreeMap<Long, byte[]> log = db.getTreeMap(LOG_NAME);
+                Atomic.Long size = db.getAtomicLong(SIZE_FIELD_NAME);
+                long startIndex = index + 1;
+                long endIndex = log.lastKey();
+                for (long i = startIndex; i <= endIndex; ++i) {
+                    byte[] entryBytes = log.remove(i);
+                    size.addAndGet(-1L * entryBytes.length);
+                }
+            }
+        });
+    }
+
+    @Override
+    public long size() {
+        assertIsOpen();
+        DB db = txMaker.makeTx();
+        try {
+            Atomic.Long size = db.getAtomicLong(SIZE_FIELD_NAME);
+            return size.get();
+        } finally {
+            db.close();
+        }
+    }
+
+    @Override
+    public void sync() throws IOException {
+        assertIsOpen();
+    }
+
+    @Override
+    public void compact(long index, Entry entry) throws IOException {
+
+        assertIsOpen();
+        txMaker.execute(new TxBlock() {
+            @Override
+            public void tx(DB db) {
+                BTreeMap<Long, byte[]> log = db.getTreeMap(LOG_NAME);
+                Atomic.Long size = db.getAtomicLong(SIZE_FIELD_NAME);
+                ConcurrentNavigableMap<Long, byte[]> headMap = log.headMap(index);
+                long deletedBytes = headMap.keySet().stream().mapToLong(i -> log.remove(i).length).sum();
+                size.addAndGet(-1 * deletedBytes);
+                byte[] entryBytes = serializer.encode(entry);
+                byte[] existingEntry = log.put(index, entryBytes);
+                size.addAndGet(entryBytes.length - existingEntry.length);
+                db.compact();
+            }
+        });
+    }
+}
\ No newline at end of file
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/SnapshotException.java b/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/SnapshotException.java
new file mode 100644
index 0000000..4cfc13b
--- /dev/null
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/SnapshotException.java
@@ -0,0 +1,13 @@
+package org.onlab.onos.store.service.impl;
+
+import org.onlab.onos.store.service.DatabaseException;
+
+/**
+ * Exception that indicates a problem with the state machine snapshotting.
+ */
+@SuppressWarnings("serial")
+public class SnapshotException extends DatabaseException {
+    public SnapshotException(Throwable t) {
+        super(t);
+    }
+}
diff --git a/core/store/dist/src/test/java/org/onlab/onos/store/service/impl/MapDBLogTest.java b/core/store/dist/src/test/java/org/onlab/onos/store/service/impl/MapDBLogTest.java
new file mode 100644
index 0000000..75beefd
--- /dev/null
+++ b/core/store/dist/src/test/java/org/onlab/onos/store/service/impl/MapDBLogTest.java
@@ -0,0 +1,193 @@
+package org.onlab.onos.store.service.impl;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.util.List;
+
+import net.kuujo.copycat.internal.log.OperationEntry;
+import net.kuujo.copycat.log.Entry;
+import net.kuujo.copycat.log.Log;
+
+import org.junit.After;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+import org.onlab.onos.store.serializers.StoreSerializer;
+
+import com.google.common.testing.EqualsTester;
+
+/**
+ * Test the MapDBLog implementation.
+ */
+public class MapDBLogTest {
+
+    private static final String DB_FILE_NAME = "mapdbTest";
+    private static final StoreSerializer SERIALIZER = ClusterMessagingProtocol.SERIALIZER;
+    private static final Entry TEST_ENTRY1 = new OperationEntry(1, "test1");
+    private static final Entry TEST_ENTRY2 = new OperationEntry(2, "test12");
+    private static final Entry TEST_ENTRY3 = new OperationEntry(3, "test123");
+    private static final Entry TEST_ENTRY4 = new OperationEntry(4, "test1234");
+
+    private static final Entry TEST_SNAPSHOT_ENTRY = new OperationEntry(5, "snapshot");
+
+    private static final long TEST_ENTRY1_SIZE = SERIALIZER.encode(TEST_ENTRY1).length;
+    private static final long TEST_ENTRY2_SIZE = SERIALIZER.encode(TEST_ENTRY2).length;
+    private static final long TEST_ENTRY3_SIZE = SERIALIZER.encode(TEST_ENTRY3).length;
+    private static final long TEST_ENTRY4_SIZE = SERIALIZER.encode(TEST_ENTRY4).length;
+
+    private static final long TEST_SNAPSHOT_ENTRY_SIZE = SERIALIZER.encode(TEST_SNAPSHOT_ENTRY).length;
+
+    @Before
+    public void setUp() throws Exception {
+    }
+
+    @After
+    public void tearDown() throws Exception {
+        Files.deleteIfExists(new File(DB_FILE_NAME).toPath());
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void testAssertOpen() {
+        Log log = new MapDBLog(new File(DB_FILE_NAME), SERIALIZER);
+        log.size();
+    }
+
+    @Test
+    public void testAppendEntry() throws IOException {
+        Log log = new MapDBLog(new File(DB_FILE_NAME), SERIALIZER);
+        log.open();
+        log.appendEntry(TEST_ENTRY1);
+        OperationEntry first = log.firstEntry();
+        OperationEntry last = log.lastEntry();
+        new EqualsTester()
+            .addEqualityGroup(first, last, TEST_ENTRY1)
+            .testEquals();
+        Assert.assertEquals(TEST_ENTRY1_SIZE, log.size());
+        Assert.assertEquals(1, log.firstIndex());
+        Assert.assertEquals(1, log.lastIndex());
+    }
+
+    @Test
+    public void testAppendEntries() throws IOException {
+        Log log = new MapDBLog(new File(DB_FILE_NAME), SERIALIZER);
+        log.open();
+        log.appendEntries(TEST_ENTRY1, TEST_ENTRY2, TEST_ENTRY3);
+        OperationEntry first = log.firstEntry();
+        OperationEntry last = log.lastEntry();
+        new EqualsTester()
+            .addEqualityGroup(first, TEST_ENTRY1)
+            .addEqualityGroup(last, TEST_ENTRY3)
+            .testEquals();
+        Assert.assertEquals(TEST_ENTRY1_SIZE + TEST_ENTRY2_SIZE, TEST_ENTRY3_SIZE, log.size());
+        Assert.assertEquals(1, log.firstIndex());
+        Assert.assertEquals(3, log.lastIndex());
+        Assert.assertTrue(log.containsEntry(1));
+        Assert.assertTrue(log.containsEntry(2));
+    }
+
+    @Test
+    public void testDelete() throws IOException {
+        Log log = new MapDBLog(new File(DB_FILE_NAME), SERIALIZER);
+        log.open();
+        log.appendEntries(TEST_ENTRY1, TEST_ENTRY2);
+        log.delete();
+        Assert.assertEquals(0, log.size());
+        Assert.assertTrue(log.isEmpty());
+        Assert.assertEquals(0, log.firstIndex());
+        Assert.assertNull(log.firstEntry());
+        Assert.assertEquals(0, log.lastIndex());
+        Assert.assertNull(log.lastEntry());
+    }
+
+    @Test
+    public void testGetEntries() throws IOException {
+        Log log = new MapDBLog(new File(DB_FILE_NAME), SERIALIZER);
+        log.open();
+        log.appendEntries(TEST_ENTRY1, TEST_ENTRY2, TEST_ENTRY3, TEST_ENTRY4);
+        Assert.assertEquals(
+                TEST_ENTRY1_SIZE +
+                TEST_ENTRY2_SIZE +
+                TEST_ENTRY3_SIZE +
+                TEST_ENTRY4_SIZE, log.size());
+
+        List<Entry> entries = log.getEntries(2, 3);
+        new EqualsTester()
+            .addEqualityGroup(log.getEntry(4), TEST_ENTRY4)
+            .addEqualityGroup(entries.get(0), TEST_ENTRY2)
+            .addEqualityGroup(entries.get(1), TEST_ENTRY3)
+            .testEquals();
+    }
+
+    @Test
+    public void testRemoveAfter() throws IOException {
+        Log log = new MapDBLog(new File(DB_FILE_NAME), SERIALIZER);
+        log.open();
+        log.appendEntries(TEST_ENTRY1, TEST_ENTRY2, TEST_ENTRY3, TEST_ENTRY4);
+        log.removeAfter(1);
+        Assert.assertEquals(TEST_ENTRY1_SIZE, log.size());
+        new EqualsTester()
+            .addEqualityGroup(log.firstEntry(), log.lastEntry(), TEST_ENTRY1)
+            .testEquals();
+    }
+
+    @Test
+    public void testAddAfterRemove() throws IOException {
+        Log log = new MapDBLog(new File(DB_FILE_NAME), SERIALIZER);
+        log.open();
+        log.appendEntries(TEST_ENTRY1, TEST_ENTRY2, TEST_ENTRY3, TEST_ENTRY4);
+        log.removeAfter(1);
+        log.appendEntry(TEST_ENTRY4);
+        Assert.assertEquals(TEST_ENTRY1_SIZE + TEST_ENTRY4_SIZE, log.size());
+        new EqualsTester()
+            .addEqualityGroup(log.firstEntry(), TEST_ENTRY1)
+            .addEqualityGroup(log.lastEntry(), TEST_ENTRY4)
+            .addEqualityGroup(log.size(), TEST_ENTRY1_SIZE + TEST_ENTRY4_SIZE)
+            .testEquals();
+    }
+
+    @Test
+    public void testClose() throws IOException {
+        Log log = new MapDBLog(new File(DB_FILE_NAME), SERIALIZER);
+        Assert.assertFalse(log.isOpen());
+        log.open();
+        Assert.assertTrue(log.isOpen());
+        log.close();
+        Assert.assertFalse(log.isOpen());
+    }
+
+    @Test
+    public void testReopen() throws IOException {
+        Log log = new MapDBLog(new File(DB_FILE_NAME), SERIALIZER);
+        log.open();
+        log.appendEntries(TEST_ENTRY1, TEST_ENTRY2, TEST_ENTRY3, TEST_ENTRY4);
+        log.close();
+        log.open();
+
+        new EqualsTester()
+            .addEqualityGroup(log.firstEntry(), TEST_ENTRY1)
+            .addEqualityGroup(log.getEntry(2), TEST_ENTRY2)
+            .addEqualityGroup(log.lastEntry(), TEST_ENTRY4)
+            .addEqualityGroup(log.size(),
+                    TEST_ENTRY1_SIZE +
+                    TEST_ENTRY2_SIZE +
+                    TEST_ENTRY3_SIZE +
+                    TEST_ENTRY4_SIZE)
+            .testEquals();
+    }
+
+    @Test
+    public void testCompact() throws IOException {
+        Log log = new MapDBLog(new File(DB_FILE_NAME), SERIALIZER);
+        log.open();
+        log.appendEntries(TEST_ENTRY1, TEST_ENTRY2, TEST_ENTRY3, TEST_ENTRY4);
+        log.compact(3, TEST_SNAPSHOT_ENTRY);
+        new EqualsTester()
+        .addEqualityGroup(log.firstEntry(), TEST_SNAPSHOT_ENTRY)
+        .addEqualityGroup(log.lastEntry(), TEST_ENTRY4)
+        .addEqualityGroup(log.size(),
+                TEST_SNAPSHOT_ENTRY_SIZE +
+                TEST_ENTRY4_SIZE)
+        .testEquals();
+    }
+}
diff --git a/core/store/trivial/src/main/java/org/onlab/onos/store/trivial/impl/SimpleMastershipStore.java b/core/store/trivial/src/main/java/org/onlab/onos/store/trivial/impl/SimpleMastershipStore.java
index 0f36393..62c084e 100644
--- a/core/store/trivial/src/main/java/org/onlab/onos/store/trivial/impl/SimpleMastershipStore.java
+++ b/core/store/trivial/src/main/java/org/onlab/onos/store/trivial/impl/SimpleMastershipStore.java
@@ -29,8 +29,13 @@
 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.onos.cluster.ClusterEventListener;
+import org.onlab.onos.cluster.ClusterService;
 import org.onlab.onos.cluster.ControllerNode;
+import org.onlab.onos.cluster.ControllerNode.State;
 import org.onlab.onos.cluster.DefaultControllerNode;
 import org.onlab.onos.cluster.NodeId;
 import org.onlab.onos.cluster.RoleInfo;
@@ -44,7 +49,8 @@
 import org.onlab.packet.IpAddress;
 import org.slf4j.Logger;
 
-import com.google.common.collect.Lists;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSet;
 
 import static org.onlab.onos.mastership.MastershipEvent.Type.*;
 
@@ -60,23 +66,65 @@
 
     private final Logger log = getLogger(getClass());
 
-    public static final IpAddress LOCALHOST = IpAddress.valueOf("127.0.0.1");
-
     private static final int NOTHING = 0;
     private static final int INIT = 1;
 
-    private ControllerNode instance =
-            new DefaultControllerNode(new NodeId("local"), LOCALHOST);
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected ClusterService clusterService;
 
     //devices mapped to their masters, to emulate multiple nodes
     protected final Map<DeviceId, NodeId> masterMap = new HashMap<>();
     //emulate backups with pile of nodes
-    protected final Set<NodeId> backups = new HashSet<>();
+    protected final Map<DeviceId, List<NodeId>> backups = new HashMap<>();
     //terms
     protected final Map<DeviceId, AtomicInteger> termMap = new HashMap<>();
 
     @Activate
     public void activate() {
+        if (clusterService == null) {
+          // just for ease of unit test
+          final ControllerNode instance =
+                  new DefaultControllerNode(new NodeId("local"),
+                                            IpAddress.valueOf("127.0.0.1"));
+
+            clusterService = new ClusterService() {
+
+                @Override
+                public ControllerNode getLocalNode() {
+                    return instance;
+                }
+
+                @Override
+                public Set<ControllerNode> getNodes() {
+                    return ImmutableSet.of(instance);
+                }
+
+                @Override
+                public ControllerNode getNode(NodeId nodeId) {
+                    if (instance.id().equals(nodeId)) {
+                        return instance;
+                    }
+                    return null;
+                }
+
+                @Override
+                public State getState(NodeId nodeId) {
+                    if (instance.id().equals(nodeId)) {
+                        return State.ACTIVE;
+                    } else {
+                        return State.INACTIVE;
+                    }
+                }
+
+                @Override
+                public void addListener(ClusterEventListener listener) {
+                }
+
+                @Override
+                public void removeListener(ClusterEventListener listener) {
+                }
+            };
+        }
         log.info("Started");
     }
 
@@ -86,31 +134,27 @@
     }
 
     @Override
-    public MastershipEvent setMaster(NodeId nodeId, DeviceId deviceId) {
-        MastershipRole role = getRole(nodeId, deviceId);
+    public synchronized MastershipEvent setMaster(NodeId nodeId, DeviceId deviceId) {
 
-        synchronized (this) {
-            switch (role) {
-                case MASTER:
-                    return null;
-                case STANDBY:
-                    masterMap.put(deviceId, nodeId);
-                    termMap.get(deviceId).incrementAndGet();
-                    backups.add(nodeId);
-                    break;
-                case NONE:
-                    masterMap.put(deviceId, nodeId);
-                    termMap.put(deviceId, new AtomicInteger(INIT));
-                    backups.add(nodeId);
-                    break;
-                default:
-                    log.warn("unknown Mastership Role {}", role);
-                    return null;
-            }
+        MastershipRole role = getRole(nodeId, deviceId);
+        switch (role) {
+        case MASTER:
+            // no-op
+            return null;
+        case STANDBY:
+        case NONE:
+            NodeId prevMaster = masterMap.put(deviceId, nodeId);
+            incrementTerm(deviceId);
+            removeFromBackups(deviceId, nodeId);
+            addToBackup(deviceId, prevMaster);
+            break;
+        default:
+            log.warn("unknown Mastership Role {}", role);
+            return null;
         }
 
         return new MastershipEvent(MASTER_CHANGED, deviceId,
-                new RoleInfo(nodeId, Lists.newLinkedList(backups)));
+                                   getNodes(deviceId));
     }
 
     @Override
@@ -118,12 +162,11 @@
         return masterMap.get(deviceId);
     }
 
+    // synchronized for atomic read
     @Override
-    public RoleInfo getNodes(DeviceId deviceId) {
-        List<NodeId> nodes = new ArrayList<>();
-        nodes.addAll(backups);
-
-        return new RoleInfo(masterMap.get(deviceId), nodes);
+    public synchronized RoleInfo getNodes(DeviceId deviceId) {
+        return new RoleInfo(masterMap.get(deviceId),
+                            backups.getOrDefault(deviceId, ImmutableList.of()));
     }
 
     @Override
@@ -134,69 +177,97 @@
                 ids.add(d.getKey());
             }
         }
-        return Collections.unmodifiableSet(ids);
+        return ids;
     }
 
     @Override
-    public MastershipRole requestRole(DeviceId deviceId) {
+    public synchronized MastershipRole requestRole(DeviceId deviceId) {
         //query+possible reelection
-        NodeId node = instance.id();
+        NodeId node = clusterService.getLocalNode().id();
         MastershipRole role = getRole(node, deviceId);
 
         switch (role) {
             case MASTER:
-                break;
+                return MastershipRole.MASTER;
             case STANDBY:
-                synchronized (this) {
-                    //try to "re-elect", since we're really not distributed
-                    NodeId rel = reelect(node);
-                    if (rel == null) {
-                        masterMap.put(deviceId, node);
-                        termMap.put(deviceId, new AtomicInteger(INIT));
-                        role = MastershipRole.MASTER;
-                    }
-                    backups.add(node);
-                }
-                break;
-            case NONE:
-                //first to get to it, say we are master
-                synchronized (this) {
+                if (getMaster(deviceId) == null) {
+                    // no master => become master
                     masterMap.put(deviceId, node);
-                    termMap.put(deviceId, new AtomicInteger(INIT));
-                    backups.add(node);
-                    role = MastershipRole.MASTER;
+                    incrementTerm(deviceId);
+                    // remove from backup list
+                    removeFromBackups(deviceId, node);
+                    notifyDelegate(new MastershipEvent(MASTER_CHANGED, deviceId,
+                                                       getNodes(deviceId)));
+                    return MastershipRole.MASTER;
                 }
-                break;
+                return MastershipRole.STANDBY;
+            case NONE:
+                if (getMaster(deviceId) == null) {
+                    // no master => become master
+                    masterMap.put(deviceId, node);
+                    incrementTerm(deviceId);
+                    notifyDelegate(new MastershipEvent(MASTER_CHANGED, deviceId,
+                                                       getNodes(deviceId)));
+                    return MastershipRole.MASTER;
+                }
+                // add to backup list
+                if (addToBackup(deviceId, node)) {
+                    notifyDelegate(new MastershipEvent(BACKUPS_CHANGED, deviceId,
+                                                       getNodes(deviceId)));
+                }
+                return MastershipRole.STANDBY;
             default:
                 log.warn("unknown Mastership Role {}", role);
         }
         return role;
     }
 
+    // add to backup if not there already, silently ignores null node
+    private synchronized boolean addToBackup(DeviceId deviceId, NodeId nodeId) {
+        boolean modified = false;
+        List<NodeId> stbys = backups.getOrDefault(deviceId, new ArrayList<>());
+        if (nodeId != null && !stbys.contains(nodeId)) {
+            stbys.add(nodeId);
+            modified = true;
+        }
+        backups.put(deviceId, stbys);
+        return modified;
+    }
+
+    private synchronized boolean removeFromBackups(DeviceId deviceId, NodeId node) {
+        List<NodeId> stbys = backups.getOrDefault(deviceId, new ArrayList<>());
+        boolean modified = stbys.remove(node);
+        backups.put(deviceId, stbys);
+        return modified;
+    }
+
+    private synchronized void incrementTerm(DeviceId deviceId) {
+        AtomicInteger term = termMap.getOrDefault(deviceId, new AtomicInteger(NOTHING));
+        term.incrementAndGet();
+        termMap.put(deviceId, term);
+    }
+
     @Override
     public MastershipRole getRole(NodeId nodeId, DeviceId deviceId) {
         //just query
         NodeId current = masterMap.get(deviceId);
         MastershipRole role;
 
-        if (current == null) {
-            if (backups.contains(nodeId)) {
-                role = MastershipRole.STANDBY;
-            } else {
-                role = MastershipRole.NONE;
-            }
+        if (current != null && current.equals(nodeId)) {
+            return MastershipRole.MASTER;
+        }
+
+        if (backups.getOrDefault(deviceId, Collections.emptyList()).contains(nodeId)) {
+            role = MastershipRole.STANDBY;
         } else {
-            if (current.equals(nodeId)) {
-                role = MastershipRole.MASTER;
-            } else {
-                role = MastershipRole.STANDBY;
-            }
+            role = MastershipRole.NONE;
         }
         return role;
     }
 
+    // synchronized for atomic read
     @Override
-    public MastershipTerm getTermFor(DeviceId deviceId) {
+    public synchronized MastershipTerm getTermFor(DeviceId deviceId) {
         if ((termMap.get(deviceId) == null)) {
             return MastershipTerm.of(masterMap.get(deviceId), NOTHING);
         }
@@ -205,72 +276,71 @@
     }
 
     @Override
-    public MastershipEvent setStandby(NodeId nodeId, DeviceId deviceId) {
+    public synchronized MastershipEvent setStandby(NodeId nodeId, DeviceId deviceId) {
         MastershipRole role = getRole(nodeId, deviceId);
-        synchronized (this) {
-            switch (role) {
-                case MASTER:
-                    NodeId backup = reelect(nodeId);
-                    if (backup == null) {
-                        masterMap.remove(deviceId);
-                    } else {
-                        masterMap.put(deviceId, backup);
-                        termMap.get(deviceId).incrementAndGet();
-                        return new MastershipEvent(MASTER_CHANGED, deviceId,
-                                new RoleInfo(backup, Lists.newLinkedList(backups)));
-                    }
-                case STANDBY:
-                case NONE:
-                    if (!termMap.containsKey(deviceId)) {
-                        termMap.put(deviceId, new AtomicInteger(INIT));
-                    }
-                    backups.add(nodeId);
-                    break;
-                default:
-                    log.warn("unknown Mastership Role {}", role);
+        switch (role) {
+        case MASTER:
+            NodeId backup = reelect(deviceId, nodeId);
+            if (backup == null) {
+                // no master alternative
+                masterMap.remove(deviceId);
+                // TODO: Should there be new event type for no MASTER?
+                return new MastershipEvent(MASTER_CHANGED, deviceId,
+                                           getNodes(deviceId));
+            } else {
+                NodeId prevMaster = masterMap.put(deviceId, backup);
+                incrementTerm(deviceId);
+                addToBackup(deviceId, prevMaster);
+                return new MastershipEvent(MASTER_CHANGED, deviceId,
+                                           getNodes(deviceId));
             }
+        case STANDBY:
+        case NONE:
+            boolean modified = addToBackup(deviceId, nodeId);
+            if (modified) {
+                return new MastershipEvent(BACKUPS_CHANGED, deviceId,
+                                           getNodes(deviceId));
+            }
+        default:
+            log.warn("unknown Mastership Role {}", role);
         }
         return null;
     }
 
     //dumbly selects next-available node that's not the current one
     //emulate leader election
-    private NodeId reelect(NodeId nodeId) {
+    private synchronized NodeId reelect(DeviceId did, NodeId nodeId) {
+        List<NodeId> stbys = backups.getOrDefault(did, Collections.emptyList());
         NodeId backup = null;
-        for (NodeId n : backups) {
+        for (NodeId n : stbys) {
             if (!n.equals(nodeId)) {
                 backup = n;
                 break;
             }
         }
-        backups.remove(backup);
+        stbys.remove(backup);
         return backup;
     }
 
     @Override
-    public MastershipEvent relinquishRole(NodeId nodeId, DeviceId deviceId) {
+    public synchronized MastershipEvent relinquishRole(NodeId nodeId, DeviceId deviceId) {
         MastershipRole role = getRole(nodeId, deviceId);
-        synchronized (this) {
-            switch (role) {
-                case MASTER:
-                    NodeId backup = reelect(nodeId);
-                    backups.remove(nodeId);
-                    if (backup == null) {
-                        masterMap.remove(deviceId);
-                    } else {
-                        masterMap.put(deviceId, backup);
-                        termMap.get(deviceId).incrementAndGet();
-                        return new MastershipEvent(MASTER_CHANGED, deviceId,
-                                new RoleInfo(backup, Lists.newLinkedList(backups)));
-                    }
-                case STANDBY:
-                    backups.remove(nodeId);
-                case NONE:
-                default:
-                    log.warn("unknown Mastership Role {}", role);
+        switch (role) {
+        case MASTER:
+            NodeId backup = reelect(deviceId, nodeId);
+            masterMap.put(deviceId, backup);
+            incrementTerm(deviceId);
+            return new MastershipEvent(MASTER_CHANGED, deviceId,
+                                       getNodes(deviceId));
+        case STANDBY:
+            if (removeFromBackups(deviceId, nodeId)) {
+                return new MastershipEvent(BACKUPS_CHANGED, deviceId,
+                                           getNodes(deviceId));
             }
+        case NONE:
+        default:
+            log.warn("unknown Mastership Role {}", role);
         }
         return null;
     }
-
 }
diff --git a/core/store/trivial/src/test/java/org/onlab/onos/store/trivial/impl/SimpleMastershipStoreTest.java b/core/store/trivial/src/test/java/org/onlab/onos/store/trivial/impl/SimpleMastershipStoreTest.java
index 711e366..0998e0a 100644
--- a/core/store/trivial/src/test/java/org/onlab/onos/store/trivial/impl/SimpleMastershipStoreTest.java
+++ b/core/store/trivial/src/test/java/org/onlab/onos/store/trivial/impl/SimpleMastershipStoreTest.java
@@ -15,6 +15,8 @@
  */
 package org.onlab.onos.store.trivial.impl;
 
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicInteger;
 
@@ -22,6 +24,7 @@
 import org.junit.Before;
 import org.junit.Test;
 import org.onlab.onos.cluster.NodeId;
+import org.onlab.onos.mastership.MastershipEvent;
 import org.onlab.onos.mastership.MastershipTerm;
 import org.onlab.onos.net.DeviceId;
 
@@ -74,6 +77,7 @@
         assertEquals("wrong role", MASTER, sms.getRole(N2, DID3));
 
         //N2 is master but N1 is only in backups set
+        put(DID4, N1, false, true);
         put(DID4, N2, true, false);
         assertEquals("wrong role", STANDBY, sms.getRole(N1, DID4));
     }
@@ -127,12 +131,12 @@
         put(DID1, N1, false, false);
         assertEquals("wrong role", MASTER, sms.requestRole(DID1));
 
-        //STANDBY without backup - become MASTER
+        //was STANDBY - become MASTER
         put(DID2, N1, false, true);
         assertEquals("wrong role", MASTER, sms.requestRole(DID2));
 
-        //STANDBY with backup - stay STANDBY
-        put(DID3, N2, false, true);
+        //other MASTER - stay STANDBY
+        put(DID3, N2, true, false);
         assertEquals("wrong role", STANDBY, sms.requestRole(DID3));
 
         //local (N1) is MASTER - stay MASTER
@@ -145,30 +149,34 @@
         //NONE - record backup but take no other action
         put(DID1, N1, false, false);
         sms.setStandby(N1, DID1);
-        assertTrue("not backed up", sms.backups.contains(N1));
-        sms.termMap.clear();
+        assertTrue("not backed up", sms.backups.get(DID1).contains(N1));
+        int prev = sms.termMap.get(DID1).get();
         sms.setStandby(N1, DID1);
-        assertTrue("term not set", sms.termMap.containsKey(DID1));
+        assertEquals("term should not change", prev, sms.termMap.get(DID1).get());
 
         //no backup, MASTER
-        put(DID1, N1, true, true);
-        assertNull("wrong event", sms.setStandby(N1, DID1));
+        put(DID1, N1, true, false);
+        assertNull("expect no MASTER event", sms.setStandby(N1, DID1).roleInfo().master());
         assertNull("wrong node", sms.masterMap.get(DID1));
 
         //backup, switch
         sms.masterMap.clear();
         put(DID1, N1, true, true);
+        put(DID1, N2, false, true);
         put(DID2, N2, true, true);
-        assertEquals("wrong event", MASTER_CHANGED, sms.setStandby(N1, DID1).type());
+        MastershipEvent event = sms.setStandby(N1, DID1);
+        assertEquals("wrong event", MASTER_CHANGED, event.type());
+        assertEquals("wrong master", N2, event.roleInfo().master());
     }
 
     //helper to populate master/backup structures
-    private void put(DeviceId dev, NodeId node, boolean store, boolean backup) {
-        if (store) {
+    private void put(DeviceId dev, NodeId node, boolean master, boolean backup) {
+        if (master) {
             sms.masterMap.put(dev, node);
-        }
-        if (backup) {
-            sms.backups.add(node);
+        } else if (backup) {
+            List<NodeId> stbys = sms.backups.getOrDefault(dev, new ArrayList<>());
+            stbys.add(node);
+            sms.backups.put(dev, stbys);
         }
         sms.termMap.put(dev, new AtomicInteger());
     }
diff --git a/features/features.xml b/features/features.xml
index 0e7dfbf..b8ef86f 100644
--- a/features/features.xml
+++ b/features/features.xml
@@ -56,6 +56,9 @@
         <bundle>mvn:org.codehaus.jackson/jackson-mapper-asl/1.9.13</bundle>
 
         <bundle>mvn:org.onlab.onos/onlab-thirdparty/1.0.0-SNAPSHOT</bundle>
+
+        <bundle>mvn:org.mapdb/mapdb/1.0.6</bundle>
+
 <!-- FIXME: resolce Chronicle's dependency issue
         <bundle>mvn:net.openhft/lang/6.4.6</bundle>
         <bundle>mvn:net.openhft/affinity/2.1.1</bundle>