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+.. This work is licensed under a Creative Commons Attribution 4.0 International License.
+.. http://creativecommons.org/licenses/by/4.0
+.. (c) OPNFV, Intel Corporation and others.
+
+collectd plugins description
+============================
+The SFQM collectd plugins enable the ability to monitor DPDK interfaces by
+exposing stats and the relevant events to higher level telemetry and fault
+management applications. The following sections will discuss the SFQM features
+in detail.
+
+Measuring Telco Traffic and Performance KPIs
+--------------------------------------------
+This section will discuss the SFQM features that enable Measuring Telco Traffic
+and Performance KPIs.
+
+.. Figure:: stats_and_timestamps.png
+
+   Measuring Telco Traffic and Performance KPIs
+
+* The very first thing SFQM enabled was a call-back API in DPDK and an
+  associated application that used the API to demonstrate how to timestamp
+  packets and measure packet latency in DPDK (the sample app is called
+  rxtx_callbacks). This was upstreamed to DPDK 2.0 and is represented by
+  the interfaces 1 and 2 in Figure 1.2.
+
+* The second thing SFQM implemented in DPDK is the extended NIC statistics API,
+  which exposes NIC stats including error stats to the DPDK user by reading the
+  registers on the NIC. This is represented by interface 3 in Figure 1.2.
+
+  * For DPDK 2.1 this API was only implemented for the ixgbe (10Gb) NIC driver,
+    in association with a sample application that runs as a DPDK secondary
+    process and retrieves the extended NIC stats.
+
+  * For DPDK 2.2 the API was implemented for igb, i40e and all the Virtual
+    Functions (VFs) for all drivers.
+
+  * For DPDK 16.07 the API migrated from using string value pairs to using id
+    value pairs, improving the overall performance of the API.
+
+Monitoring DPDK interfaces
+--------------------------
+With the features SFQM enabled in DPDK to enable measuring Telco traffic and
+performance KPIs, we can now retrieve NIC statistics including error stats and
+relay them to a DPDK user. The next step is to enable monitoring of the DPDK
+interfaces based on the stats that we are retrieving from the NICs, by relaying
+the information to a higher level Fault Management entity. To enable this SFQM
+has been enabling a number of plugins for collectd.
+
+collectd
+~~~~~~~~
+collectd is a daemon which collects system performance statistics periodically
+and provides a variety of mechanisms to publish the collected metrics. It
+supports more than 90 different input and output plugins. Input plugins retrieve
+metrics and publish them to the collectd deamon, while output plugins publish
+the data they receive to an end point. collectd also has infrastructure to
+support thresholding and notification.
+
+collectd statistics and Notifications
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Within collectd notifications and performance data are dispatched in the same
+way. There are producer plugins (plugins that create notifications/metrics),
+and consumer plugins (plugins that receive notifications/metrics and do
+something with them).
+
+Statistics in collectd consist of a value list. A value list includes:
+
+* Values, can be one of:
+
+  * Derive: used for values where a change in the value since it's last been
+    read is of interest. Can be used to calculate and store a rate.
+
+  * Counter: similar to derive values, but take the possibility of a counter
+    wrap around into consideration.
+
+  * Gauge: used for values that are stored as is.
+
+  * Absolute: used for counters that are reset after reading.
+
+* Value length: the number of values in the data set.
+
+* Time: timestamp at which the value was collected.
+
+* Interval: interval at which to expect a new value.
+
+* Host: used to identify the host.
+
+* Plugin: used to identify the plugin.
+
+* Plugin instance (optional): used to group a set of values together. For e.g.
+  values belonging to a DPDK interface.
+
+* Type: unit used to measure a value. In other words used to refer to a data
+  set.
+
+* Type instance (optional): used to distinguish between values that have an
+  identical type.
+
+* meta data: an opaque data structure that enables the passing of additional
+  information about a value list. "Meta data in the global cache can be used to
+  store arbitrary information about an identifier" [7].
+
+Host, plugin, plugin instance, type and type instance uniquely identify a
+collectd value.
+
+Values lists are often accompanied by data sets that describe the values in more
+detail. Data sets consist of:
+
+* A type: a name which uniquely identifies a data set.
+
+* One or more data sources (entries in a data set) which include:
+
+  * The name of the data source. If there is only a single data source this is
+    set to "value".
+
+  * The type of the data source, one of: counter, gauge, absolute or derive.
+
+  * A min and a max value.
+
+Types in collectd are defined in types.db. Examples of types in types.db:
+
+.. code-block:: console
+
+    bitrate    value:GAUGE:0:4294967295
+    counter    value:COUNTER:U:U
+    if_octets  rx:COUNTER:0:4294967295, tx:COUNTER:0:4294967295
+
+In the example above if_octets has two data sources: tx and rx.
+
+Notifications in collectd are generic messages containing:
+
+* An associated severity, which can be one of OKAY, WARNING, and FAILURE.
+
+* A time.
+
+* A Message
+
+* A host.
+
+* A plugin.
+
+* A plugin instance (optional).
+
+* A type.
+
+* A types instance (optional).
+
+* Meta-data.
+
+collectd plugins
+----------------
+SFQM has enabled three collectd plugins to date:
+
+* `dpdkstat plugin`_: A read plugin that retrieve stats from the DPDK extended
+   NIC stats API.
+
+* `ceilometer plugin`_: A write plugin that pushes the retrieved stats to
+  Ceilometer. It's capable of pushing any stats read through collectd to
+  Ceilometer, not just the DPDK stats.
+
+* `hugepages plugin`_:  A read plugin that retrieves the number of available
+  and free hugepages on a platform as well as what is available in terms of
+  hugepages per socket.
+
+Other plugins in progress:
+
+* dpdkevents:  A read plugin that retrieves DPDK link status and DPDK
+  forwarding cores liveliness status (DPDK Keep Alive).
+
+* Open vSwitch stats Plugin: A read plugin that retrieve flow and interface
+  stats from OVS.
+
+* Open vSwitch events Plugin: A read plugin that retrieves events from OVS.
+
+
+Monitoring Interfaces and Openstack Support
+-------------------------------------------
+.. Figure:: monitoring_interfaces.png
+
+   Monitoring Interfaces and Openstack Support
+
+The figure above shows the DPDK L2 forwarding application running on a compute
+node, sending and receiving traffic. collectd is also running on this compute
+node retrieving the stats periodically from DPDK through the dpdkstat plugin
+and publishing the retrieved stats to Ceilometer through the ceilometer plugin.
+
+To see this demo in action please checkout: `SFQM OPNFV Summit demo`_
+
+References
+----------
+[1] https://collectd.org/wiki/index.php/Naming_schema
+[2] https://github.com/collectd/collectd/blob/master/src/daemon/plugin.h
+[3] https://collectd.org/wiki/index.php/Value_list_t
+[4] https://collectd.org/wiki/index.php/Data_set
+[5] https://collectd.org/documentation/manpages/types.db.5.shtml
+[6] https://collectd.org/wiki/index.php/Data_source
+[7] https://collectd.org/wiki/index.php/Meta_Data_Interface
+
+.. _SFQM OPNFV Summit demo: https://prezi.com/kjv6o8ixs6se/software-fastpath-service-quality-metrics-demo/
+.. _dpdkstat plugin: https://github.com/maryamtahhan/collectd-with-DPDK/tree/dpdkstat
+.. _ceilometer plugin: https://github.com/openstack/collectd-ceilometer-plugin/tree/stable/mitaka
+.. _hugepages plugin: https://github.com/maryamtahhan/collectd-with-DPDK/tree/hugepages