For controller initiated connection, there is race condition
[ovsdb.git] / southbound / southbound-impl / src / main / java / org / opendaylight / ovsdb / southbound / OvsdbConnectionManager.java
index 8180007c777e07fa5a1412bd726451093c7ec99c..ecfedfe48f1b787f71331f454c1dc944ad72898e 100644 (file)
  */
 package org.opendaylight.ovsdb.southbound;
 
+import static org.opendaylight.ovsdb.lib.operations.Operations.op;
+
 import java.net.InetAddress;
 import java.net.UnknownHostException;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ExecutionException;
+
+import javax.annotation.Nonnull;
 
 import org.opendaylight.controller.md.sal.binding.api.DataBroker;
 import org.opendaylight.controller.md.sal.binding.api.ReadOnlyTransaction;
-import org.opendaylight.controller.md.sal.binding.api.WriteTransaction;
+import org.opendaylight.controller.md.sal.binding.api.ReadWriteTransaction;
+import org.opendaylight.controller.md.sal.common.api.clustering.CandidateAlreadyRegisteredException;
+import org.opendaylight.controller.md.sal.common.api.clustering.Entity;
+import org.opendaylight.controller.md.sal.common.api.clustering.EntityOwnershipCandidateRegistration;
+import org.opendaylight.controller.md.sal.common.api.clustering.EntityOwnershipChange;
+import org.opendaylight.controller.md.sal.common.api.clustering.EntityOwnershipListener;
+import org.opendaylight.controller.md.sal.common.api.clustering.EntityOwnershipListenerRegistration;
+import org.opendaylight.controller.md.sal.common.api.clustering.EntityOwnershipService;
+import org.opendaylight.controller.md.sal.common.api.clustering.EntityOwnershipState;
 import org.opendaylight.controller.md.sal.common.api.data.LogicalDatastoreType;
 import org.opendaylight.controller.md.sal.common.api.data.ReadFailedException;
 import org.opendaylight.ovsdb.lib.OvsdbClient;
+import org.opendaylight.ovsdb.lib.OvsdbConnection;
 import org.opendaylight.ovsdb.lib.OvsdbConnectionListener;
-import org.opendaylight.ovsdb.lib.impl.OvsdbConnectionService;
-import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.overlay.rev150105.IpPortLocator;
+import org.opendaylight.ovsdb.lib.operations.Operation;
+import org.opendaylight.ovsdb.lib.operations.OperationResult;
+import org.opendaylight.ovsdb.lib.operations.Select;
+import org.opendaylight.ovsdb.lib.schema.DatabaseSchema;
+import org.opendaylight.ovsdb.lib.schema.GenericTableSchema;
+import org.opendaylight.ovsdb.lib.schema.typed.TyperUtils;
+import org.opendaylight.ovsdb.schema.openvswitch.OpenVSwitch;
+import org.opendaylight.ovsdb.southbound.transactions.md.OvsdbNodeRemoveCommand;
+import org.opendaylight.ovsdb.southbound.transactions.md.TransactionInvoker;
 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.ovsdb.rev150105.OvsdbBridgeAttributes;
-import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.ovsdb.rev150105.OvsdbManagedNodeAugmentation;
+import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.ovsdb.rev150105.OvsdbBridgeAugmentation;
 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.ovsdb.rev150105.OvsdbNodeAugmentation;
-import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.ovsdb.rev150105.OvsdbNodeRef;
+import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.ovsdb.rev150105.ovsdb.node.attributes.ConnectionInfo;
 import org.opendaylight.yang.gen.v1.urn.tbd.params.xml.ns.yang.network.topology.rev131021.network.topology.topology.Node;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import com.google.common.base.Optional;
 import com.google.common.base.Preconditions;
 import com.google.common.util.concurrent.CheckedFuture;
 
 public class OvsdbConnectionManager implements OvsdbConnectionListener, AutoCloseable {
-    Map<OvsdbClientKey,OvsdbConnectionInstance> clients = new ConcurrentHashMap<OvsdbClientKey,OvsdbConnectionInstance>();
+    private Map<ConnectionInfo, OvsdbConnectionInstance> clients =
+            new ConcurrentHashMap<>();
     private static final Logger LOG = LoggerFactory.getLogger(OvsdbConnectionManager.class);
+    private static final String ENTITY_TYPE = "ovsdb";
 
-    DataBroker db;
+    private DataBroker db;
+    private TransactionInvoker txInvoker;
+    private Map<ConnectionInfo,InstanceIdentifier<Node>> instanceIdentifiers =
+            new ConcurrentHashMap<>();
+    private Map<Entity, OvsdbConnectionInstance> entityConnectionMap =
+            new ConcurrentHashMap<>();
+    private EntityOwnershipService entityOwnershipService;
+    private OvsdbDeviceEntityOwnershipListener ovsdbDeviceEntityOwnershipListener;
+    private OvsdbConnection ovsdbConnection;
 
-    public OvsdbConnectionManager(DataBroker db) {
+    public OvsdbConnectionManager(DataBroker db,TransactionInvoker txInvoker,
+                                  EntityOwnershipService entityOwnershipService,
+                                  OvsdbConnection ovsdbConnection) {
         this.db = db;
+        this.txInvoker = txInvoker;
+        this.entityOwnershipService = entityOwnershipService;
+        this.ovsdbDeviceEntityOwnershipListener = new OvsdbDeviceEntityOwnershipListener(this, entityOwnershipService);
+        this.ovsdbConnection = ovsdbConnection;
     }
 
     @Override
-    public void connected(OvsdbClient externalClient) {
+    public void connected(@Nonnull final OvsdbClient externalClient) {
+
+        OvsdbConnectionInstance client = connectedButCallBacksNotRegistered(externalClient);
+
+        // Register Cluster Ownership for ConnectionInfo
+        registerEntityForOwnership(client);
+    }
+
+    public OvsdbConnectionInstance connectedButCallBacksNotRegistered(final OvsdbClient externalClient) {
         LOG.info("OVSDB Connection from {}:{}",externalClient.getConnectionInfo().getRemoteAddress(),
                 externalClient.getConnectionInfo().getRemotePort());
-        OvsdbClientKey key = new OvsdbClientKey(externalClient);
-        OvsdbConnectionInstance client = new OvsdbConnectionInstance(key,externalClient);
-        clients.put(key, client);
-        WriteTransaction transaction = db.newWriteOnlyTransaction();
-        transaction.put(LogicalDatastoreType.OPERATIONAL, key.toInstanceIndentifier(),
-                SouthboundMapper.createNode(client));
-        // TODO - Check the future and retry if needed
-        transaction.submit();
+        ConnectionInfo key = SouthboundMapper.createConnectionInfo(externalClient);
+        OvsdbConnectionInstance ovsdbConnectionInstance = getConnectionInstance(key);
+
+        // Check if existing ovsdbConnectionInstance for the OvsdbClient present.
+        // In such cases, we will see if the ovsdbConnectionInstance has same externalClient.
+        if (ovsdbConnectionInstance != null) {
+            if (ovsdbConnectionInstance.hasOvsdbClient(externalClient)) {
+                LOG.warn("OVSDB Connection Instance {} already exists for client {}", key, externalClient);
+                return ovsdbConnectionInstance;
+            }
+            LOG.warn("OVSDB Connection Instance {} being replaced with client {}", key, externalClient);
+
+            // Unregister Cluster Ownership for ConnectionInfo
+            // Because the ovsdbConnectionInstance is about to be completely replaced!
+            unregisterEntityForOwnership(ovsdbConnectionInstance);
+
+            ovsdbConnectionInstance.disconnect();
+
+            removeConnectionInstance(key);
+        }
+
+        ovsdbConnectionInstance = new OvsdbConnectionInstance(key, externalClient, txInvoker,
+                getInstanceIdentifier(key));
+        ovsdbConnectionInstance.createTransactInvokers();
+        return ovsdbConnectionInstance;
     }
 
     @Override
     public void disconnected(OvsdbClient client) {
-        LOG.info("OVSDB Disconnect from {}:{}",client.getConnectionInfo().getRemoteAddress(),
+        LOG.info("OVSDB Disconnected from {}:{}. Cleaning up the operational data store"
+                ,client.getConnectionInfo().getRemoteAddress(),
                 client.getConnectionInfo().getRemotePort());
-        OvsdbClientKey key = new OvsdbClientKey(client);
-        WriteTransaction transaction = db.newWriteOnlyTransaction();
-        transaction.delete(LogicalDatastoreType.OPERATIONAL, key.toInstanceIndentifier());
-        // TODO - Check the future and retry if needed
-        transaction.submit();
-        clients.remove(key);
+        ConnectionInfo key = SouthboundMapper.createConnectionInfo(client);
+        OvsdbConnectionInstance ovsdbConnectionInstance = getConnectionInstance(key);
+        if (ovsdbConnectionInstance != null) {
+            // Unregister Entity ownership as soon as possible ,so this instance should
+            // not be used as a candidate in Entity election (given that this instance is
+            // about to disconnect as well), if current owner get disconnected from
+            // OVSDB device.
+            unregisterEntityForOwnership(ovsdbConnectionInstance);
+
+            txInvoker.invoke(new OvsdbNodeRemoveCommand(ovsdbConnectionInstance, null, null));
+
+            removeConnectionInstance(key);
+        } else {
+            LOG.warn("disconnected : Connection instance not found for OVSDB Node {} ", key);
+        }
+        LOG.trace("OvsdbConnectionManager: disconnected exit");
     }
 
-    public OvsdbClient connect(OvsdbNodeAugmentation ovsdbNode) throws UnknownHostException {
+    public OvsdbClient connect(InstanceIdentifier<Node> iid,
+            OvsdbNodeAugmentation ovsdbNode) throws UnknownHostException {
         // TODO handle case where we already have a connection
-        // TODO use transaction chains to handle ordering issues between disconnected and connected when writing to the operational store
-        InetAddress ip = SouthboundMapper.createInetAddress(ovsdbNode.getIp());
-        OvsdbClient client = OvsdbConnectionService.getService().connect(ip, ovsdbNode.getPort().getValue().intValue());
-        OvsdbClientKey key = new OvsdbClientKey(client);
-        OvsdbConnectionInstance instance = new OvsdbConnectionInstance(key,client);
-        clients.put(key, instance);
-        connected(client); // For connections from the controller to the ovs instance, the library doesn't call this method for us
+        // TODO use transaction chains to handle ordering issues between disconnected
+        // TODO and connected when writing to the operational store
+        InetAddress ip = SouthboundMapper.createInetAddress(ovsdbNode.getConnectionInfo().getRemoteIp());
+        OvsdbClient client = ovsdbConnection.connect(ip,
+                ovsdbNode.getConnectionInfo().getRemotePort().getValue());
+        // For connections from the controller to the ovs instance, the library doesn't call
+        // this method for us
+        if (client != null) {
+            putInstanceIdentifier(ovsdbNode.getConnectionInfo(), iid.firstIdentifierOf(Node.class));
+            OvsdbConnectionInstance ovsdbConnectionInstance = connectedButCallBacksNotRegistered(client);
+            ovsdbConnectionInstance.setOvsdbNodeAugmentation(ovsdbNode);
+
+            // Register Cluster Ownership for ConnectionInfo
+            registerEntityForOwnership(ovsdbConnectionInstance);
+        } else {
+            LOG.warn("Failed to connect to OVSDB Node {}", ovsdbNode.getConnectionInfo());
+        }
         return client;
     }
 
     public void disconnect(OvsdbNodeAugmentation ovsdbNode) throws UnknownHostException {
-        OvsdbClientKey key = new OvsdbClientKey(ovsdbNode.getIp(), ovsdbNode.getPort());
-        OvsdbClient client = clients.get(key);
+        OvsdbConnectionInstance client = getConnectionInstance(ovsdbNode.getConnectionInfo());
         if (client != null) {
+            // Unregister Cluster Onwership for ConnectionInfo
+            unregisterEntityForOwnership(client);
+
             client.disconnect();
-            disconnected(client);
+
+            removeInstanceIdentifier(ovsdbNode.getConnectionInfo());
+        } else {
+            LOG.debug("disconnect : connection instance not found for {}",ovsdbNode.getConnectionInfo());
         }
     }
 
+/*    public void init(ConnectionInfo key) {
+        OvsdbConnectionInstance client = getConnectionInstance(key);
+
+        // TODO (FF): make sure that this cluster instance is the 'entity owner' fo the given OvsdbConnectionInstance ?
+
+        if (client != null) {
+
+             *  Note: registerCallbacks() is idemPotent... so if you call it repeatedly all is safe,
+             *  it only registersCallbacks on the *first* call.
+
+            client.registerCallbacks();
+        }
+    }
+*/
     @Override
     public void close() throws Exception {
-        for(OvsdbClient client: clients.values()) {
+        if (ovsdbDeviceEntityOwnershipListener != null) {
+            ovsdbDeviceEntityOwnershipListener.close();
+        }
+
+        for (OvsdbClient client: clients.values()) {
             client.disconnect();
         }
     }
 
-    public OvsdbClient getClient(OvsdbClientKey key) {
-        return clients.get(key);
+    private void putConnectionInstance(ConnectionInfo key,OvsdbConnectionInstance instance) {
+        ConnectionInfo connectionInfo = SouthboundMapper.suppressLocalIpPort(key);
+        clients.put(connectionInfo, instance);
     }
 
-    public OvsdbClient getClient(IpPortLocator loc) {
-        Preconditions.checkNotNull(loc);
-        return getClient(new OvsdbClientKey(loc));
+    private void removeConnectionInstance(ConnectionInfo key) {
+        ConnectionInfo connectionInfo = SouthboundMapper.suppressLocalIpPort(key);
+        clients.remove(connectionInfo);
     }
 
-    public OvsdbClient getClient(OvsdbBridgeAttributes mn) {
-        Preconditions.checkNotNull(mn);
-        try {
-            OvsdbNodeRef ref = mn.getManagedBy();
-            if(ref != null) {
-                ReadOnlyTransaction transaction = db.newReadOnlyTransaction();
-                CheckedFuture<?, ReadFailedException> nf = transaction.read(LogicalDatastoreType.OPERATIONAL, ref.getValue());
-                transaction.close();
-                Object obj = nf.get();
-                if(obj instanceof Node) {
-                    OvsdbNodeAugmentation ovsdbNode = ((Node)obj).getAugmentation(OvsdbNodeAugmentation.class);
-                    if(ovsdbNode !=null) {
-                        return getClient(ovsdbNode);
-                    } else {
-                        LOG.warn("OvsdbManagedNode {} claims to be managed by {} but that OvsdbNode does not exist",mn,ref.getValue());
-                        return null;
-                    }
-                } else {
-                    LOG.warn("Mysteriously got back a thing which is *not* a topology Node: {}",obj);
-                    return null;
-                }
-            } else {
-                LOG.warn("Cannot find client for OvsdbManagedNode without a specified ManagedBy {}",mn);
-                return null;
-            }
-         } catch (Exception e) {
-             LOG.warn("Failed to get OvsdbNode that manages OvsdbManagedNode {}",mn, e);
-             return null;
-         }
+    private void putInstanceIdentifier(ConnectionInfo key,InstanceIdentifier<Node> iid) {
+        ConnectionInfo connectionInfo = SouthboundMapper.suppressLocalIpPort(key);
+        instanceIdentifiers.put(connectionInfo, iid);
     }
 
-    public OvsdbClient getClient(Node node) {
+    private void removeInstanceIdentifier(ConnectionInfo key) {
+        ConnectionInfo connectionInfo = SouthboundMapper.suppressLocalIpPort(key);
+        instanceIdentifiers.remove(connectionInfo);
+    }
+
+    public OvsdbConnectionInstance getConnectionInstance(ConnectionInfo key) {
+        ConnectionInfo connectionInfo = SouthboundMapper.suppressLocalIpPort(key);
+        return clients.get(connectionInfo);
+    }
+
+    public InstanceIdentifier<Node> getInstanceIdentifier(ConnectionInfo key) {
+        ConnectionInfo connectionInfo = SouthboundMapper.suppressLocalIpPort(key);
+        return instanceIdentifiers.get(connectionInfo);
+    }
+
+    public OvsdbConnectionInstance getConnectionInstance(OvsdbBridgeAttributes mn) {
+        Optional<OvsdbNodeAugmentation> optional = SouthboundUtil.getManagingNode(db, mn);
+        if (optional.isPresent()) {
+            return getConnectionInstance(optional.get().getConnectionInfo());
+        } else {
+            return null;
+        }
+    }
+
+    public OvsdbConnectionInstance getConnectionInstance(Node node) {
         Preconditions.checkNotNull(node);
         OvsdbNodeAugmentation ovsdbNode = node.getAugmentation(OvsdbNodeAugmentation.class);
-        OvsdbManagedNodeAugmentation ovsdbManagedNode = node.getAugmentation(OvsdbManagedNodeAugmentation.class);
-        if(ovsdbNode != null) {
-            return getClient(ovsdbNode);
+        OvsdbBridgeAugmentation ovsdbManagedNode = node.getAugmentation(OvsdbBridgeAugmentation.class);
+        if (ovsdbNode != null) {
+            return getConnectionInstance(ovsdbNode.getConnectionInfo());
         } else if (ovsdbManagedNode != null) {
-            return getClient(ovsdbManagedNode);
+            return getConnectionInstance(ovsdbManagedNode);
         } else {
             LOG.warn("This is not a node that gives any hint how to find its OVSDB Manager: {}",node);
             return null;
         }
     }
+
+    public OvsdbConnectionInstance getConnectionInstance(InstanceIdentifier<Node> nodePath) {
+        try {
+            ReadOnlyTransaction transaction = db.newReadOnlyTransaction();
+            CheckedFuture<Optional<Node>, ReadFailedException> nodeFuture = transaction.read(
+                    LogicalDatastoreType.OPERATIONAL, nodePath);
+            transaction.close();
+            Optional<Node> optional = nodeFuture.get();
+            if (optional != null && optional.isPresent() && optional.get() instanceof Node) {
+                return this.getConnectionInstance(optional.get());
+            } else {
+                LOG.warn("Found non-topological node {} on path {}",optional);
+                return null;
+            }
+        } catch (Exception e) {
+            LOG.warn("Failed to get Ovsdb Node {}",nodePath, e);
+            return null;
+        }
+    }
+
+    public OvsdbClient getClient(ConnectionInfo connectionInfo) {
+        return getConnectionInstance(connectionInfo);
+    }
+
+    public OvsdbClient getClient(OvsdbBridgeAttributes mn) {
+        return getConnectionInstance(mn);
+    }
+
+    public OvsdbClient getClient(Node node) {
+        return getConnectionInstance(node);
+    }
+
+    public Boolean getHasDeviceOwnership(ConnectionInfo connectionInfo) {
+        OvsdbConnectionInstance ovsdbConnectionInstance = getConnectionInstance(connectionInfo);
+        if (ovsdbConnectionInstance == null) {
+            return Boolean.FALSE;
+        }
+        return ovsdbConnectionInstance.getHasDeviceOwnership();
+    }
+
+    public void setHasDeviceOwnership(ConnectionInfo connectionInfo, Boolean hasDeviceOwnership) {
+        OvsdbConnectionInstance ovsdbConnectionInstance = getConnectionInstance(connectionInfo);
+        if (ovsdbConnectionInstance != null) {
+            ovsdbConnectionInstance.setHasDeviceOwnership(hasDeviceOwnership);
+        }
+    }
+
+    private void handleOwnershipChanged(EntityOwnershipChange ownershipChange) {
+        OvsdbConnectionInstance ovsdbConnectionInstance = getConnectionInstanceFromEntity(ownershipChange.getEntity());
+        LOG.debug("handleOwnershipChanged: {} event received for device {}",
+                ownershipChange, ovsdbConnectionInstance != null ? ovsdbConnectionInstance.getConnectionInfo()
+                        : "that's currently NOT registered by *this* southbound plugin instance");
+
+        if (ovsdbConnectionInstance == null) {
+            if (ownershipChange.isOwner()) {
+                LOG.warn("handleOwnershipChanged: *this* instance is elected as an owner of the device {} but it "
+                        + "is NOT registered for ownership", ownershipChange.getEntity());
+            } else {
+                // EntityOwnershipService sends notification to all the nodes, irrespective of whether
+                // that instance registered for the device ownership or not. It is to make sure that
+                // If all the controller instance that was connected to the device are down, so the
+                // running instance can clear up the operational data store even though it was not
+                // connected to the device.
+                LOG.debug("handleOwnershipChanged: No connection instance found for {}", ownershipChange.getEntity());
+            }
+
+            // If entity has no owner, clean up the operational data store (it's possible because owner controller
+            // might went down abruptly and didn't get a chance to clean up the operational data store.
+            if (!ownershipChange.hasOwner()) {
+                LOG.info("{} has no owner, cleaning up the operational data store", ownershipChange.getEntity());
+                cleanEntityOperationalData(ownershipChange.getEntity());
+            }
+            return;
+        }
+        //Connection detail need to be cached, irrespective of ownership result.
+        putConnectionInstance(ovsdbConnectionInstance.getMDConnectionInfo(),ovsdbConnectionInstance);
+
+        if (ownershipChange.isOwner() == ovsdbConnectionInstance.getHasDeviceOwnership()) {
+            LOG.info("handleOwnershipChanged: no change in ownership for {}. Ownership status is : {}",
+                    ovsdbConnectionInstance.getConnectionInfo(), ovsdbConnectionInstance.getHasDeviceOwnership()
+                            ? SouthboundConstants.OWNERSHIPSTATES.OWNER.getState()
+                            : SouthboundConstants.OWNERSHIPSTATES.NONOWNER.getState());
+            return;
+        }
+
+        ovsdbConnectionInstance.setHasDeviceOwnership(ownershipChange.isOwner());
+        // You were not an owner, but now you are
+        if (ownershipChange.isOwner()) {
+            LOG.info("handleOwnershipChanged: *this* southbound plugin instance is an OWNER of the device {}",
+                    ovsdbConnectionInstance.getConnectionInfo());
+
+            //*this* instance of southbound plugin is owner of the device,
+            //so register for monitor callbacks
+            ovsdbConnectionInstance.registerCallbacks();
+
+        } else {
+            //You were owner of the device, but now you are not. With the current ownership
+            //grant mechanism, this scenario should not occur. Because this scenario will occur
+            //when this controller went down or switch flap the connection, but in both the case
+            //it will go through the re-registration process. We need to implement this condition
+            //when clustering service implement a ownership grant strategy which can revoke the
+            //device ownership for load balancing the devices across the instances.
+            //Once this condition occur, we should unregister the callback.
+            LOG.error("handleOwnershipChanged: *this* southbound plugin instance is no longer the owner of device {}."
+                    + "This should NOT happen.",
+                    ovsdbConnectionInstance.getNodeId().getValue());
+        }
+    }
+
+    private void cleanEntityOperationalData(Entity entity) {
+
+        InstanceIdentifier<Node> nodeIid = (InstanceIdentifier<Node>) SouthboundUtil
+                .getInstanceIdentifierCodec().bindingDeserializer(entity.getId());
+
+        final ReadWriteTransaction transaction = db.newReadWriteTransaction();
+        Optional<Node> node = SouthboundUtil.readNode(transaction, nodeIid);
+        if (node.isPresent()) {
+            SouthboundUtil.deleteNode(transaction, nodeIid);
+        }
+    }
+
+    private OpenVSwitch getOpenVswitchTableEntry(OvsdbConnectionInstance connectionInstance) {
+        DatabaseSchema dbSchema = null;
+        OpenVSwitch openVSwitchRow = null;
+        try {
+            dbSchema = connectionInstance.getSchema(OvsdbSchemaContants.databaseName).get();
+        } catch (InterruptedException | ExecutionException e) {
+            LOG.warn("Not able to fetch schema for database {} from device {}",
+                    OvsdbSchemaContants.databaseName,connectionInstance.getConnectionInfo(),e);
+        }
+        if (dbSchema != null) {
+            GenericTableSchema openVSwitchSchema = TyperUtils.getTableSchema(dbSchema, OpenVSwitch.class);
+
+            List<String> openVSwitchTableColumn = new ArrayList<>();
+            openVSwitchTableColumn.addAll(openVSwitchSchema.getColumns());
+            Select<GenericTableSchema> selectOperation = op.select(openVSwitchSchema);
+            selectOperation.setColumns(openVSwitchTableColumn);
+
+            List<Operation> operations = new ArrayList<>();
+            operations.add(selectOperation);
+            operations.add(op.comment("Fetching Open_VSwitch table rows"));
+            try {
+                List<OperationResult> results = connectionInstance.transact(dbSchema, operations).get();
+                if (results != null ) {
+                    OperationResult selectResult = results.get(0);
+                    openVSwitchRow = TyperUtils.getTypedRowWrapper(
+                            dbSchema,OpenVSwitch.class,selectResult.getRows().get(0));
+
+                }
+            } catch (InterruptedException | ExecutionException e) {
+                LOG.warn("Not able to fetch OpenVswitch table row from device {}",
+                        connectionInstance.getConnectionInfo(),e);
+            }
+        }
+        return openVSwitchRow;
+    }
+    private Entity getEntityFromConnectionInstance(@Nonnull OvsdbConnectionInstance ovsdbConnectionInstance) {
+        InstanceIdentifier<Node> iid = ovsdbConnectionInstance.getInstanceIdentifier();
+        if ( iid == null ) {
+            /* Switch initiated connection won't have iid, till it gets OpenVSwitch
+             * table update but update callback is always registered after ownership
+             * is granted. So we are explicitly fetch the row here to get the iid.
+             */
+            OpenVSwitch openvswitchRow = getOpenVswitchTableEntry(ovsdbConnectionInstance);
+            iid = SouthboundMapper.getInstanceIdentifier(openvswitchRow);
+            LOG.info("InstanceIdentifier {} generated for device "
+                    + "connection {}",iid,ovsdbConnectionInstance.getConnectionInfo());
+            ovsdbConnectionInstance.setInstanceIdentifier(iid);
+        }
+        YangInstanceIdentifier entityId = SouthboundUtil.getInstanceIdentifierCodec().getYangInstanceIdentifier(iid);
+        Entity deviceEntity = new Entity(ENTITY_TYPE, entityId);
+        LOG.debug("Entity {} created for device connection {}",
+                deviceEntity, ovsdbConnectionInstance.getConnectionInfo());
+        return deviceEntity;
+    }
+
+    private OvsdbConnectionInstance getConnectionInstanceFromEntity(Entity entity) {
+        return entityConnectionMap.get(entity);
+    }
+
+    private void registerEntityForOwnership(OvsdbConnectionInstance ovsdbConnectionInstance) {
+
+        Entity candidateEntity = getEntityFromConnectionInstance(ovsdbConnectionInstance);
+        entityConnectionMap.put(candidateEntity, ovsdbConnectionInstance);
+        ovsdbConnectionInstance.setConnectedEntity(candidateEntity);
+        try {
+            EntityOwnershipCandidateRegistration registration =
+                    entityOwnershipService.registerCandidate(candidateEntity);
+            ovsdbConnectionInstance.setDeviceOwnershipCandidateRegistration(registration);
+            LOG.info("OVSDB entity {} is registered for ownership.", candidateEntity);
+
+            //If entity already has owner, it won't get notification from EntityOwnershipService
+            //so cache the connection instances.
+            Optional<EntityOwnershipState> ownershipStateOpt =
+                    entityOwnershipService.getOwnershipState(candidateEntity);
+            if (ownershipStateOpt.isPresent()) {
+                EntityOwnershipState ownershipState = ownershipStateOpt.get();
+                if (ownershipState.hasOwner() && !ownershipState.isOwner()) {
+                    LOG.info("OVSDB entity {} is already owned by other southbound plugin "
+                                    + "instance, so *this* instance is NOT an OWNER of the device",
+                            ovsdbConnectionInstance.getConnectionInfo());
+                    putConnectionInstance(ovsdbConnectionInstance.getMDConnectionInfo(),ovsdbConnectionInstance);
+                }
+            }
+        } catch (CandidateAlreadyRegisteredException e) {
+            LOG.warn("OVSDB entity {} was already registered for ownership", candidateEntity, e);
+        }
+
+    }
+
+    private void unregisterEntityForOwnership(OvsdbConnectionInstance ovsdbConnectionInstance) {
+        ovsdbConnectionInstance.closeDeviceOwnershipCandidateRegistration();
+        entityConnectionMap.remove(ovsdbConnectionInstance.getConnectedEntity());
+    }
+
+    private class OvsdbDeviceEntityOwnershipListener implements EntityOwnershipListener {
+        private OvsdbConnectionManager cm;
+        private EntityOwnershipListenerRegistration listenerRegistration;
+
+        OvsdbDeviceEntityOwnershipListener(OvsdbConnectionManager cm, EntityOwnershipService entityOwnershipService) {
+            this.cm = cm;
+            listenerRegistration = entityOwnershipService.registerListener(ENTITY_TYPE, this);
+        }
+        public void close() {
+            listenerRegistration.close();
+        }
+        @Override
+        public void ownershipChanged(EntityOwnershipChange ownershipChange) {
+            cm.handleOwnershipChanged(ownershipChange);
+        }
+    }
 }