ONOS-6825: added OFAgent tracer

Change-Id: Ib04184b5fe108c636f8fb9c4b721a1004b72c0a7
diff --git a/apps/ofagent/src/main/java/org/onosproject/ofagent/api/OFAgent.java b/apps/ofagent/src/main/java/org/onosproject/ofagent/api/OFAgent.java
index ed1b2be..4602185 100644
--- a/apps/ofagent/src/main/java/org/onosproject/ofagent/api/OFAgent.java
+++ b/apps/ofagent/src/main/java/org/onosproject/ofagent/api/OFAgent.java
@@ -16,6 +16,7 @@
 package org.onosproject.ofagent.api;
 
 import org.onosproject.incubator.net.virtual.NetworkId;
+import org.onosproject.incubator.net.virtual.TenantId;
 
 import java.util.Set;
 
@@ -25,6 +26,8 @@
  */
 public interface OFAgent {
 
+    String TRACER_LOG_TENANT_ID_PREFIX = "OFAGENT_tenantId:";
+
     enum State {
 
         /**
@@ -46,6 +49,13 @@
     NetworkId networkId();
 
     /**
+     * Returns the identifier of the tenant which owns virtual network this agent cares for.
+     *
+     * @return id of the tenant
+     */
+    TenantId tenantId();
+
+    /**
      * Returns the external OpenFlow controllers of the virtual network.
      *
      * @return set of openflow controllers
@@ -89,6 +99,14 @@
         Builder networkId(NetworkId networkId);
 
         /**
+         * Returns OF agent builder with the supplied tenant ID.
+         *
+         * @param tenantId id of the virtual network
+         * @return of agent builder
+         */
+        Builder tenantId(TenantId tenantId);
+
+        /**
          * Returns OF agent builder with the supplied controllers.
          *
          * @param controllers set of openflow controllers