From 04eee1fda9fe592e9055ac23af71f07603c8ceff Mon Sep 17 00:00:00 2001
From: Adam Israel <adam.israel@canonical.com>
Date: Mon, 29 Apr 2019 14:59:45 -0400
Subject: [PATCH] Fix bug 680

This patch adds two new methods, Subscribe and Unsubscribe, allowing the
caller to subscribe to callback messages for an already deployed charm.

Change-Id: I1e34b488914feb488cf80b157fd664ca37037e76
Signed-off-by: Adam Israel <adam.israel@canonical.com>
---
 Makefile    |  1 +
 n2vc/vnf.py | 36 +++++++++++++++++++++++++++++++-----
 2 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/Makefile b/Makefile
index abc2c39..fab6991 100644
--- a/Makefile
+++ b/Makefile
@@ -3,6 +3,7 @@ clean:
 	find . -name *.pyc -delete
 	rm -rf .tox
 	rm -rf tests/charms/builds/*
+	lxc list test- --format=json|jq '.[]["name"]'| xargs lxc delete --force
 .tox:
 	tox -r --notest
 test: lint
diff --git a/n2vc/vnf.py b/n2vc/vnf.py
index 9f8360b..a68e657 100644
--- a/n2vc/vnf.py
+++ b/n2vc/vnf.py
@@ -443,11 +443,10 @@ class N2VC:
         # Register this application with the model-level event monitor #
         ################################################################
         if callback:
-            self.monitors[model_name].AddApplication(
+            self.log.debug("JujuApi: Registering callback for {}".format(
                 application_name,
-                callback,
-                *callback_args
-            )
+            ))
+            await self.Subscribe(model_name, application_name, callback, *callback_args)
 
         ########################################################
         # Check for specific machine placement (native charms) #
@@ -801,7 +800,7 @@ class N2VC:
             app = await self.get_application(model, application_name)
             if app:
                 # Remove this application from event monitoring
-                self.monitors[model_name].RemoveApplication(application_name)
+                await self.Unsubscribe(model_name, application_name)
 
                 # self.notify_callback(model_name, application_name, "removing", callback, *callback_args)
                 self.log.debug(
@@ -906,6 +905,33 @@ class N2VC:
             return True
         return False
 
+    async def Subscribe(self, ns_name, application_name, callback, *callback_args):
+        """Subscribe to callbacks for an application.
+
+        :param ns_name str: The name of the Network Service
+        :param application_name str: The name of the application
+        :param callback obj: The callback method
+        :param callback_args list: The list of arguments to append to calls to
+            the callback method
+        """
+        self.monitors[ns_name].AddApplication(
+            application_name,
+            callback,
+            *callback_args
+        )
+
+    async def Unsubscribe(self, ns_name, application_name):
+        """Unsubscribe to callbacks for an application.
+
+        Unsubscribes the caller from notifications from a deployed application.
+
+        :param ns_name str: The name of the Network Service
+        :param application_name str: The name of the application
+        """
+        self.monitors[ns_name].RemoveApplication(
+            application_name,
+        )
+
     # Non-public methods
     async def add_relation(self, model_name, relation1, relation2):
         """
-- 
2.17.1