Laboratoire de l'Informatique et du Parallélisme » XLcloud

Although cloud computing has been transformational to the IT industry, it is built on large data centres that often consume massive amounts of electrical power. Efforts have been made to reduce the energy clouds consume, with certain data centres now approaching a \ac{PUE} factor of 1.08. While this is an incredible mark, it also means that the IT infrastructure accounts for a large part of the power consumed by a data centre. Hence, means to monitor and analyse how energy is spent have never been so crucial. Such monitoring is required not only for understanding how power is consumed, but also for assessing the impact of energy management policies. In this article, we draw lessons from experience on monitoring large-scale systems and introduce the energy monitoring software framework called \ac{KWAPI} able to deal with OpenStack clouds. The framework --- whose architecture is scalable, extensible, and completely integrated into OpenStack --- supports several wattmeter devices, multiple measurement formats, and minimises communication overhead.

This paper describes the design and architecture of a generic and flexible framework, termed as \ac{KWAPI}, that originally interfaces with OpenStack to provide it with power consumption information collected from multiple heterogeneous probes. OpenStack is a project that aims to provide ubiquitous open source cloud computing platform and is currently used by many corporations, researchers and global data centres\footnote{http://www.openstack.org/user-stories/}. We describe how \ac{KWAPI} has been integrated into Ceilometer; OpenStack's  component conceived to provide a framework to collect a large range of metrics for metering purposes\footnote{https://wiki.openstack.org/wiki/Ceilometer}. With the increasing use of Ceilometer as the \textit{de facto} metering tool for OpenStack, we believe that such an integration of a power monitoring framework into OpenStack can be of great value to the research community and practitioners.

\subsection{Related Work on Energy Monitoring and Efficiency in Clouds}

The communication between the layers is handled by a bus, as explained in detail later. Data consumers can subscribe to receive information collected by drivers from multiple sites. Both drivers and consumers are easily extensible to support, respectively, several types of wattmeters and provide additional data processing services. A REST API is designed as a data consumer to provide a programming interface for developers and system administrators. In this work it is used to interface with OpenStack by providing the information (\textit{i.e.} by polling monitored devices) required by a \textit{\ac{KWAPI} Pollster} to feed Ceilometer.

Table \ref{tab:wattmeters} shows the characteristics of equipments we deployed and used with Kwapi in our Cloud infrastructures.

This section provides results of a performance evaluation carried out in our testbed. The goal is not to compare publish/subscribe systems as such work has already been performed elsewhere \cite{EugsterSurvey:2003,FabretPS:2001}. The evaluation demonstrates that the framework serves well the needs of a large range of users of the Grid'5000 platform \cite{Grid5000} --- the infrastructure we use and where the Kwapi framework is currently deployed in production mode as the means for collecting and providing energy consumption information to users. 

In this paper, we described the first framework (KWAPI) for monitoring the power consumed by resources of an Openstack  cloud. Based on lessons learned on monitoring the power consumption of a large distributed infrastructure, we described the main user requirements and how they are met by the proposed architecture. The framework works in tandem with OpenStack's Ceilometer. Experimental results demonstrate that the overhead posed by the monitoring framework is small, allowing us to serve the users' monitoring needs of our large scale infrastructure.