Section: Research Program

Research axis 2: Cloud and Edge processing

The recent evolutions in the area of Big Data processing have pointed out some limitations of the initial Map-Reduce model. It is well suited for batch data processing, but less suited for real-time processing of dynamic data streams. New types of data-intensive applications emerge, e.g., for enterprises who need to perform analysis on their stream data in ways that can give fast results (i.e., in real time) at scale (e.g., click-stream analysis and network-monitoring log analysis). Similarly, scientists require fast and accurate data processing techniques in order to analyze their experimental data correctly at scale (e.g., collectively analysis of large data sets distributed in multiple geographically distributed locations).

Our plan is to revisit current data storage and processing techniques to cope with the volatile requirements of data-intensive applications on large-scale dynamic clouds in a cost-efficient way, with a particular focus on streaming. More recently, the strong emergence of edge/fog-based infrastructures leads to to additional challenges for new scenarios involving hybrid cloud/fog/edge systems.

Collaboration.

This axis is addressed in close collaboration with María Pérez (UPM), Kate Keahey. (ANL)

Relevant groups with similar interests include the following ones.

• The group of Geoffrey Fox, Indiana University, working on data analytics, cloud data processing, stream processing.

• The group at RISE Lab, UC Berkeley, working on real-time stream-based processing and analytics.

• The group of Ewa Deelman, USC Information Sciences Institute, working on resource management for workflows in clouds.

Stream-oriented, Big Data processing on clouds

The state-of-the-art Hadoop Map-Reduce framework cannot deal with stream data applications, as it requires the data to be initially stored in a distributed file system in order to process them. To better cope with the above-mentioned requirements, several systems have been introduced for stream data processing such as Flink  [27], Spark  [32], Storm  [33], and Google MillWheel  [34]. These systems keep computation in memory to decrease latency, and preserve scalability by using data-partitioning or dividing the streams into a set of deterministic batch computations.

However, they are designed to work in dedicated environments and they do not consider the performance variability (i.e., network, I/O, etc.) caused by resource contention in the cloud. This variability may in turn cause high and unpredictable latency when output streams are transmitted to further analysis. Moreover, they overlook the dynamic nature of data streams and the volatility in their computation requirements. Finally, they still address failures in a best-effort manner.

Our objective is to investigate new approaches for reliable, stream Big Data processing on clouds.

Efficient Edge, Cloud and hybrid Edge/Cloud data processing

Today, we are approaching an important technological milestone: applications are generating huge amounts of data and are demanding low-latency responses to their requests. Mobile computing and Internet of Things (IoT) applications are good illustrations of such scenarios. Using only Cloud computing for such scenarios is challenging. Firstly, Cloud resources are most of the time accessed through Internet, hence, data are sent across high-latency wide area networks, which may degrade the performance of applications. Secondly, it may be impossible to send data to the Cloud due to data regulations, national security laws or simply because an Internet connection is not available. Finally, data transmission costs (e.g., Cloud provider fees, carrier costs) could make a business solution impractical.

Edge computing is a new paradigm which aims to address some of these issues. The key idea is to leverage computing and storage resources at the "edge" of the network, i.e., on processing units located close to the data sources. This allows applications to outsource task execution from the main (Cloud) processing data centers to the edge. The development of Edge computing was accelerated by the recent emergence of stream processing, a new model for handling continuous flows of data in real-time, as opposed to batch processing, which typically processes bounded datasets offline.

However, Edge computing is not a silver bullet. Besides being a new concept not fully established in the community, issues like node volatility, limited processing power, high latency between nodes, fault tolerance and data degradation may impact applications depending on the characteristics of the infrastructure.

Some relevant research questions are: How much can one improve (or degrade) the performance of an application by performing data processing closer to the data sources rather than performing it in the cloud? How to progress towards a seamless scheduling and execution of a data analytics workflow and break the limitation the current dual approaches used in preliminary efforts in this area, that rely on manual and empirical deployment of the corresponding dataflow operator graphs, using separate analytics engines for centralized clouds and for edge systems respectively?

Our objective is to try to answer precisely such questions. We are interested in understanding the conditions that enable the usage of Edge or Cloud computing to reduce the time to results and the associated costs. While some state-of-the-art approaches advocate either "100% Cloud" or "100% Edge" solutions, the relative efficiency of a method over the other may vary. Intuitively, it depends on many parameters, including network technology, hardware characteristics, volume of data or computing power, processing framework configuration and application requirements, to cite a few. We plan to study their impact on the overall application performance.