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+.. This work is licensed under a Creative Commons Attribution 4.0 International License.
+.. http://creativecommons.org/licenses/by/4.0
+
+Gap analysis in upstream projects
+=================================
+
+This section presents the findings of gaps on existing VIM platforms. The focus
+was to identify gaps based on the features and requirements specified in Section
+3.3. The analysis work determined gaps that are presented here.
+
+VIM Northbound Interface
+------------------------
+
+Immediate Notification
+^^^^^^^^^^^^^^^^^^^^^^
+
+* Type: 'deficiency in performance'
+* Description
+
+  + To-be
+
+    - VIM has to notify unavailability of virtual resource (fault) to VIM user
+      immediately.
+    - Notification should be passed in '1 second' after fault detected/notified
+      by VIM.
+    - Also, the following conditions/requirement have to be met:
+
+      - Only the owning user can receive notification of fault related to owned
+        virtual resource(s).
+
+  + As-is
+
+    - OpenStack Metering 'Ceilometer' can notify unavailability of virtual
+      resource (fault) to the owner of virtual resource based on alarm
+      configuration by the user.
+
+      - Ceilometer Alarm API:
+        http://docs.openstack.org/developer/ceilometer/webapi/v2.html#alarms
+
+    - Alarm notifications are triggered by alarm evaluator instead of
+      notification agents that might receive faults
+
+      - Ceilometer Architecture:
+        http://docs.openstack.org/developer/ceilometer/architecture.html#id1
+
+    - Evaluation interval should be equal to or larger than configured pipeline
+      interval for collection of underlying metrics.
+
+      - https://github.com/openstack/ceilometer/blob/stable/juno/ceilometer/alarm/service.py#L38-42
+
+    - The interval for collection has to be set large enough which depends on
+      the size of the deployment and the number of metrics to be collected.
+    - The interval may not be less than one second in even small deployments.
+      The default value is 60 seconds.
+    - Alternative: OpenStack has a message bus to publish system events.
+      The operator can allow the user to connect this, but there are no
+      functions to filter out other events that should not be passed to the user
+      or which were not requested by the user.
+
+  + Gap
+
+    - Fault notifications cannot be received immediately by Ceilometer.
+
+* Solved by
+
+  + Event Alarm Evaluator:
+    https://specs.openstack.org/openstack/ceilometer-specs/specs/liberty/event-alarm-evaluator.html
+  + New OpenStack alarms and notifications project AODH:
+    http://docs.openstack.org/developer/aodh/
+
+Maintenance Notification
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+* Type: 'missing'
+* Description
+
+  + To-be
+
+    - VIM has to notify unavailability of virtual resource triggered by NFVI
+      maintenance to VIM user.
+    - Also, the following conditions/requirements have to be met:
+
+      - VIM should accept maintenance message from administrator and mark target
+        physical resource "in maintenance".
+      - Only the owner of virtual resource hosted by target physical resource
+        can receive the notification that can trigger some process for
+        applications which are running on the virtual resource (e.g. cut off
+        VM).
+
+  + As-is
+
+    - OpenStack: None
+    - AWS (just for study)
+
+      - AWS provides API and CLI to view status of resource (VM) and to create
+        instance status and system status alarms to notify you when an instance
+        has a failed status check.
+        http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/monitoring-instances-status-check_sched.html
+      - AWS provides API and CLI to view scheduled events, such as a reboot or
+        retirement, for your instances. Also, those events will be notified
+        via e-mail.
+        http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/monitoring-system-instance-status-check.html
+
+  + Gap
+
+    - VIM user cannot receive maintenance notifications.
+
+* Solved by
+
+  + https://blueprints.launchpad.net/nova/+spec/service-status-notification
+
+VIM Southbound interface
+------------------------
+
+Normalization of data collection models
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+* Type: 'missing'
+* Description
+
+  + To-be
+
+    - A normalized data format needs to be created to cope with the many data
+      models from different monitoring solutions.
+
+  + As-is
+
+    - Data can be collected from many places (e.g. Zabbix, Nagios, Cacti,
+      Zenoss). Although each solution establishes its own data models, no common
+      data abstraction models exist in OpenStack.
+
+  + Gap
+
+    - Normalized data format does not exist.
+
+* Solved by
+
+  + Specification in Section :ref:`southbound`.
+
+OpenStack
+---------
+
+Ceilometer
+^^^^^^^^^^
+
+OpenStack offers a telemetry service, Ceilometer, for collecting measurements of
+the utilization of physical and virtual resources [CEIL]_. Ceilometer can
+collect a number of metrics across multiple OpenStack components and watch for
+variations and trigger alarms based upon the collected data.
+
+Scalability of fault aggregation
+________________________________
+
+* Type: 'scalability issue'
+* Description
+
+  + To-be
+
+    - Be able to scale to a large deployment, where thousands of monitoring
+      events per second need to be analyzed.
+
+  + As-is
+
+    - Performance issue when scaling to medium-sized deployments.
+
+  + Gap
+
+    - Ceilometer seems to be unsuitable for monitoring medium and large scale
+      NFVI deployments.
+
+* Solved by
+
+  + Usage of Zabbix for fault aggregation [ZABB]_. Zabbix can support a much
+    higher number of fault events (up to 15 thousand events per second, but
+    obviously also has some upper bound:
+    http://blog.zabbix.com/scalable-zabbix-lessons-on-hitting-9400-nvps/2615/
+
+  + Decentralized/hierarchical deployment with multiple instances, where one
+    instance is only responsible for a small NFVI.
+
+Monitoring of hardware and software
+___________________________________
+
+* Type: 'missing (lack of functionality)'
+* Description
+
+  + To-be
+
+    - OpenStack (as VIM) should monitor various hardware and software in NFVI to
+      handle faults on them by Ceilometer.
+    - OpenStack may have monitoring functionality in itself and can be
+      integrated with third party monitoring tools.
+    - OpenStack need to be able to detect the faults listed in the Annex.
+
+  + As-is
+
+    - For each deployment of OpenStack, an operator has responsibility to
+      configure monitoring tools with relevant scripts or plugins in order to
+      monitor hardware and software.
+    - OpenStack Ceilometer does not monitor hardware and software to capture
+      faults.
+
+  + Gap
+
+    - Ceilometer is not able to detect and handle all faults listed in the Annex.
+
+* Solved by
+
+  + Use of dedicated monitoring tools like Zabbix or Monasca.
+    See :ref:`nfvi_faults`.
+
+Nova
+^^^^
+
+OpenStack Nova [NOVA]_ is a mature and widely known and used component in
+OpenStack cloud deployments. It is the main part of an
+"infrastructure-as-a-service" system providing a cloud computing fabric
+controller, supporting a wide diversity of virtualization and container
+technologies.
+
+Nova has proven throughout these past years to be highly available and
+fault-tolerant. Featuring its own API, it also provides a compatibility API with
+Amazon EC2 APIs.
+
+Correct states when compute host is down
+________________________________________
+
+* Type: 'missing (lack of functionality)'
+* Description
+
+  + To-be
+
+    - The API shall support to change VM power state in case host has failed.
+    - The API shall support to change nova-compute state.
+    - There could be single API to change different VM states for all VMs
+      belonging to a specific host.
+    - Support external systems that are monitoring the infrastructure and resources
+      that are able to call the API fast and reliable.
+    - Resource states are reliable such that correlation actions can be fast and automated.
+    - User shall be able to read states from OpenStack and trust they are correct.
+
+  + As-is
+
+    - When a VM goes down due to a host HW, host OS or hypervisor failure,
+      nothing happens in OpenStack. The VMs of a crashed host/hypervisor are
+      reported to be live and OK through the OpenStack API.
+    - nova-compute state might change too slowly or the state is not reliable
+      if expecting also VMs to be down. This leads to ability to schedule VMs
+      to a failed host and slowness blocks evacuation.
+
+  + Gap
+
+    - OpenStack does not change its states fast and reliably enough.
+    - The API does not support to have an external system to change states and to
+      trust the states are reliable (external system has fenced failed host).
+    - User cannot read all the states from OpenStack nor trust they are right.
+
+* Solved by
+
+  + https://blueprints.launchpad.net/nova/+spec/mark-host-down
+  + https://blueprints.launchpad.net/python-novaclient/+spec/support-force-down-service
+
+Evacuate VMs in Maintenance mode
+________________________________
+
+* Type: 'missing'
+* Description
+
+  + To-be
+
+    - When maintenance mode for a compute host is set, trigger VM evacuation to
+      available compute nodes before bringing the host down for maintenance.
+
+  + As-is
+
+    - If setting a compute node to a maintenance mode, OpenStack only schedules
+      evacuation of all VMs to available compute nodes if in-maintenance compute
+      node runs the XenAPI and VMware ESX hypervisors. Other hypervisors (e.g.
+      KVM) are not supported and, hence, guest VMs will likely stop running due
+      to maintenance actions administrator may perform (e.g. hardware upgrades,
+      OS updates).
+
+  + Gap
+
+    - Nova libvirt hypervisor driver does not implement automatic guest VMs
+      evacuation when compute nodes are set to maintenance mode (``$ nova
+      host-update --maintenance enable <hostname>``).
+
+Monasca
+^^^^^^^
+
+Monasca is an open-source monitoring-as-a-service (MONaaS) solution that
+integrates with OpenStack. Even though it is still in its early days, it is the
+interest of the community that the platform be multi-tenant, highly scalable,
+performant and fault-tolerant. It provides a streaming alarm engine, a
+notification engine, and a northbound REST API users can use to interact with
+Monasca. Hundreds of thousands of metrics per second can be processed
+[MONA]_.
+
+Anomaly detection
+_________________
+
+
+* Type: 'missing (lack of functionality)'
+* Description
+
+  + To-be
+
+    - Detect the failure and perform a root cause analysis to filter out other
+      alarms that may be triggered due to their cascading relation.
+
+  + As-is
+
+    - A mechanism to detect root causes of failures is not available.
+
+  + Gap
+
+    - Certain failures can trigger many alarms due to their dependency on the
+      underlying root cause of failure. Knowing the root cause can help filter
+      out unnecessary and overwhelming alarms.
+
+* Status
+
+  + Monasca as of now lacks this feature, although the community is aware and
+    working toward supporting it.
+
+Sensor monitoring
+_________________
+
+* Type: 'missing (lack of functionality)'
+* Description
+
+  + To-be
+
+    - It should support monitoring sensor data retrieval, for instance, from
+      IPMI.
+
+  + As-is
+
+    - Monasca does not monitor sensor data
+
+  + Gap
+
+    - Sensor monitoring is very important. It provides operators status
+      on the state of the physical infrastructure (e.g. temperature, fans).
+
+* Addressed by
+
+  + Monasca can be configured to use third-party monitoring solutions (e.g.
+    Nagios, Cacti) for retrieving additional data.
+
+Hardware monitoring tools
+-------------------------
+
+Zabbix
+^^^^^^
+
+Zabbix is an open-source solution for monitoring availability and performance of
+infrastructure components (i.e. servers and network devices), as well as
+applications [ZABB]_. It can be customized for use with OpenStack. It is a
+mature tool and has been proven to be able to scale to large systems with
+100,000s of devices.
+
+Delay in execution of actions
+_____________________________
+
+
+* Type: 'deficiency in performance'
+* Description
+
+  + To-be
+
+    - After detecting a fault, the monitoring tool should immediately execute
+      the appropriate action, e.g. inform the manager through the NB I/F
+
+  + As-is
+
+    - A delay of around 10 seconds was measured in two independent testbed
+      deployments
+
+  + Gap
+
+    - Cause of the delay is a periodic evaluation and notification. Periodicity is configured
+      as 30s default value and can be reduced to 5s but not below.
+      https://github.com/zabbix/zabbix/blob/trunk/conf/zabbix_server.conf#L329
+
+
+..
+ vim: set tabstop=4 expandtab textwidth=80: