Merge lp:~blake-rouse/maas/fix-1640300-2.1 into lp:maas/2.1

[Blake Rouse]

Be defensive in the postgresql listener when a system notification is received for a none existed handler or missing listener channel.

Backport: https://code.launchpad.net/~blake-rouse/maas/fix-1640300/+merge/310506

[Blake Rouse (blake-rouse)]

Self-approving backport.

review: Approve

[MAAS Lander (maas-lander)]

The attempt to merge lp:~blake-rouse/maas/fix-1640300-2.1 into lp:maas/2.1 failed. Below is the output from the failed tests.

Hit:1 http://prodstack-zone-1.clouds.archive.ubuntu.com/ubuntu xenial InRelease
Get:2 http://prodstack-zone-1.clouds.archive.ubuntu.com/ubuntu xenial-updates InRelease [95.7 kB]
Hit:3 http://security.ubuntu.com/ubuntu xenial-security InRelease
Hit:4 http://prodstack-zone-1.clouds.archive.ubuntu.com/ubuntu xenial-backports InRelease
Fetched 95.7 kB in 0s (245 kB/s)
Reading package lists...
sudo DEBIAN_FRONTEND=noninteractive apt-get -y \
    --no-install-recommends install apache2 archdetect-deb authbind avahi-utils bash bind9 bind9utils build-essential bzr bzr-builddeb chromium-browser chromium-chromedriver curl daemontools debhelper dh-apport dh-systemd distro-info dnsutils firefox freeipmi-tools git gjs ipython isc-dhcp-common isc-dhcp-server libjs-angularjs libjs-jquery libjs-jquery-hotkeys libjs-yui3-full libjs-yui3-min libpq-dev make nodejs-legacy npm postgresql pxelinux python3-all python3-apt python3-attr python3-bson python3-convoy python3-crochet python3-cssselect python3-curtin python3-dev python3-distro-info python3-django python3-django-nose python3-django-piston3 python3-dnspython python3-docutils python3-formencode python3-hivex python3-httplib2 python3-jinja2 python3-jsonschema python3-lxml python3-netaddr python3-netifaces python3-novaclient python3-oauth python3-oauthlib python3-openssl python3-paramiko python3-petname python3-pexpect python3-psycopg2 python3-pyinotify python3-pyparsing python3-pyvmomi python3-requests python3-seamicroclient python3-setuptools python3-simplestreams python3-sphinx python3-tempita python3-twisted python3-txtftp python3-tz python3-yaml python3-zope.interface python-bson python-crochet python-django python-django-piston python-djorm-ext-pgarray python-formencode python-lxml python-netaddr python-netifaces python-pocket-lint python-psycopg2 python-simplejson python-tempita python-twisted python-yaml socat syslinux-common tgt ubuntu-cloudimage-keyring wget xvfb
Reading package lists...
Building dependency tree...
Reading state information...
authbind is already the newest version (2.1.1+nmu1).
avahi-utils is already the newest version (0.6.32~rc+dfsg-1ubuntu2).
build-essential is already the newest version (12.1ubuntu2).
debhelper is already the newest version (9.20160115ubuntu3).
distro-info is already the newest version (0.14build1).
freeipmi-tools is already the newest version (1.4.11-1ubuntu1).
git is already the newest version (1:2.7.4-0ubuntu1).
libjs-angularjs is already the newest version (1.2.28-1ubuntu2).
libjs-jquery is already the newest version (1.11.3+dfsg-4).
libjs-yui3-full is already the newest version (3.5.1-1ubuntu3).
libjs-yui3-min is already the newest version (3.5.1-1ubuntu3).
make is already the newest version (4.1-6).
postgresql is already the newest version (9.5+173).
pxelinux is already the newest version (3:6.03+dfsg-11ubuntu1).
python-formencode is already the newest version (1.3.0-0ubuntu5).
python-lxml is already the newest version (3.5.0-1build1).
python-netaddr is already the newest version (0.7.18-1).
python-netifaces is already the newest v...

[MAAS Lander (maas-lander)]

The attempt to merge lp:~blake-rouse/maas/fix-1640300-2.1 into lp:maas/2.1 failed. Below is the output from the failed tests.

Hit:1 http://prodstack-zone-1.clouds.archive.ubuntu.com/ubuntu xenial InRelease
Get:2 http://security.ubuntu.com/ubuntu xenial-security InRelease [94.5 kB]
Get:3 http://prodstack-zone-1.clouds.archive.ubuntu.com/ubuntu xenial-updates InRelease [95.7 kB]
Hit:4 http://prodstack-zone-1.clouds.archive.ubuntu.com/ubuntu xenial-backports InRelease
Fetched 190 kB in 0s (405 kB/s)
Reading package lists...
sudo DEBIAN_FRONTEND=noninteractive apt-get -y \
    --no-install-recommends install apache2 archdetect-deb authbind avahi-utils bash bind9 bind9utils build-essential bzr bzr-builddeb chromium-browser chromium-chromedriver curl daemontools debhelper dh-apport dh-systemd distro-info dnsutils firefox freeipmi-tools git gjs ipython isc-dhcp-common isc-dhcp-server libjs-angularjs libjs-jquery libjs-jquery-hotkeys libjs-yui3-full libjs-yui3-min libpq-dev make nodejs-legacy npm postgresql pxelinux python3-all python3-apt python3-attr python3-bson python3-convoy python3-crochet python3-cssselect python3-curtin python3-dev python3-distro-info python3-django python3-django-nose python3-django-piston3 python3-dnspython python3-docutils python3-formencode python3-hivex python3-httplib2 python3-jinja2 python3-jsonschema python3-lxml python3-netaddr python3-netifaces python3-novaclient python3-oauth python3-oauthlib python3-openssl python3-paramiko python3-petname python3-pexpect python3-psycopg2 python3-pyinotify python3-pyparsing python3-pyvmomi python3-requests python3-seamicroclient python3-setuptools python3-simplestreams python3-sphinx python3-tempita python3-twisted python3-txtftp python3-tz python3-yaml python3-zope.interface python-bson python-crochet python-django python-django-piston python-djorm-ext-pgarray python-formencode python-lxml python-netaddr python-netifaces python-pocket-lint python-psycopg2 python-simplejson python-tempita python-twisted python-yaml socat syslinux-common tgt ubuntu-cloudimage-keyring wget xvfb
Reading package lists...
Building dependency tree...
Reading state information...
authbind is already the newest version (2.1.1+nmu1).
avahi-utils is already the newest version (0.6.32~rc+dfsg-1ubuntu2).
build-essential is already the newest version (12.1ubuntu2).
debhelper is already the newest version (9.20160115ubuntu3).
distro-info is already the newest version (0.14build1).
freeipmi-tools is already the newest version (1.4.11-1ubuntu1).
git is already the newest version (1:2.7.4-0ubuntu1).
libjs-angularjs is already the newest version (1.2.28-1ubuntu2).
libjs-jquery is already the newest version (1.11.3+dfsg-4).
libjs-yui3-full is already the newest version (3.5.1-1ubuntu3).
libjs-yui3-min is already the newest version (3.5.1-1ubuntu3).
make is already the newest version (4.1-6).
postgresql is already the newest version (9.5+173).
pxelinux is already the newest version (3:6.03+dfsg-11ubuntu1).
python-formencode is already the newest version (1.3.0-0ubuntu5).
python-lxml is already the newest version (3.5.0-1build1).
python-netaddr is already the newest version (0.7.18-1).
python-netifaces is already the...

=== modified file 'src/maasserver/listener.py'
--- src/maasserver/listener.py	2016-10-24 14:02:17 +0000
+++ src/maasserver/listener.py	2016-11-15 15:18:16 +0000
@@ -160,8 +160,20 @@
                     if self.isSystemChannel(notify.channel):
                         # System level message; pass it to the registered
                         # handler immediately.
-                        handler = self.listeners[notify.channel][0]
-                        handler(notify.channel, notify.payload)
+                        if notify.channel in self.listeners:
+                            # Be defensive in that if a handler does not exist
+                            # for this channel then the channel should be
+                            # unregisted and removed from listeners.
+                            if len(self.listeners[notify.channel]) > 0:
+                                handler = self.listeners[notify.channel][0]
+                                handler(notify.channel, notify.payload)
+                            else:
+                                self.unregisterChannel(notify.channel)
+                                del self.listeners[notify.channel]
+                        else:
+                            # Unregister the channel since no listener is
+                            # registered for this channel.
+                            self.unregisterChannel(notify.channel)
                     else:
                         # Place non-system messages into the queue to be
                         # processed.

=== modified file 'src/maasserver/tests/test_listener.py'
--- src/maasserver/tests/test_listener.py	2016-10-24 14:02:17 +0000
+++ src/maasserver/tests/test_listener.py	2016-11-15 15:18:16 +0000
@@ -110,6 +110,39 @@
 
     @wait_for_reactor
     @inlineCallbacks
+    def test__handles_missing_system_handler_on_notification(self):
+        listener = PostgresListenerService()
+        # Change notifications to a frozenset. This makes sure that
+        # the system message does not go into the queue. Instead if should
+        # call the handler directly in `doRead`.
+        listener.notifications = frozenset()
+        yield listener.startService()
+        yield deferToDatabase(listener.registerChannel, "sys_test")
+        listener.listeners["sys_test"] = []
+        try:
+            yield deferToDatabase(self.send_notification, "sys_test", 1)
+            self.assertFalse("sys_test" in listener.listeners)
+        finally:
+            yield listener.stopService()
+
+    @wait_for_reactor
+    @inlineCallbacks
+    def test__handles_missing_notify_system_listener_on_notification(self):
+        listener = PostgresListenerService()
+        # Change notifications to a frozenset. This makes sure that
+        # the system message does not go into the queue. Instead if should
+        # call the handler directly in `doRead`.
+        listener.notifications = frozenset()
+        yield listener.startService()
+        yield deferToDatabase(listener.registerChannel, "sys_test")
+        try:
+            yield deferToDatabase(self.send_notification, "sys_test", 1)
+            self.assertFalse("sys_test" in listener.listeners)
+        finally:
+            yield listener.stopService()
+
+    @wait_for_reactor
+    @inlineCallbacks
     def test__calls_handler_on_notification(self):
         listener = PostgresListenerService()
         dv = DeferredValue()