A Distributed Analysis Framework for Heterogeneous Data Processing in HEP Environments

During the last extended maintenance period, CERNs Large Hadron Collider (LHC) and most of its equipment systems were upgraded to collide particles at an energy level almost twice higher compared to previous operational limits, significantly increasing the damage potential to accelerator components in case of equipment malfunctioning. System upgrades and the increased machine energy pose new challenges for the analysis of transient data recordings, which have to be both dependable and fast to maintain the required safety level of the deployed machine protection systems while at the same time maximizing the accelerator performance. With the LHC having operated for many years already, statistical and trend analysis across the collected data sets is an additional, growing requirement. The currently deployed accelerator transient data recording and analysis systems will equally require significant upgrades, as the developed architectures state-of-art at the time of their initial development are already working well beyond the initially provisioned capacities. Despite the fact that modern data storage and processing systems, are capable of solving multiple shortcomings of the present solution, the operation of the world’s biggest scientific experiment creates a set of unique challenges which require additional effort to be overcome. Among others, the dynamicity and heterogeneity of the data sources and executed workloads pose a significant challenge for the modern distributed data analysis solutions to achieve its optimal efficiency. In this thesis, a novel workload-aware approach for distributed file system storage and processing solutions a Mixed Partitioning Scheme Replication is proposed. Taking into consideration the experience of other researchers in the field and the most popular large dataset analysis architectures, the developed solution takes advantage of both, replication and partitioning in order to improve the efficiency of the underlying engine. The fundamental concept of the proposed approach is the multi-criteria partitioning, optimized for different workload categories observed on the target system. Unlike in traditional solutions, the repository replicates the data copies with a different structure instead of distributing the exact same representation of the data through the cluster nodes. This approach is expected to be more efficient and flexible in comparison to the generically optimized partitioning schemes. Additionally,the partitioning and replication criteria can by dynamically altered in case significant workload changes with respect to the initial assumptions are developing with time. The performance of the presented technique was initially assessed recurring to simulations. A specific model which recreated the behavior of the proposed approach and the original Hadoop system was developed. The main assumption, which allowed to describe the system’s behavior for different configurations, is based on the fact that the application execution time is linearly related with its input size, observed during initial assessment of the distributed data storage and processing solutions. The results of the simulations allowed to identify the profile of use cases for which the Mixed Partitioning Scheme Replication was more efficient in comparison to the traditional approaches and allowed quantifying the expected gains. Additionally, a prototype incorporating the core features of the proposed technique was developed and integrated into the Hadoop source code. The implementation was deployed on clusters with different characteristics and in-depth performance evaluation experiments were conducted. The workload was generated by a specifically developed and highly configurable application, which in addition monitors the application execution and collects a large set of executionand infrastructure-related metrics. The obtained results allowed to study the efficiency of the proposed solution on the actual physical cluster, using genuine accelerator device data and user requests. In comparison to the traditional approach, the Mixed Partitioning Scheme Replication was considerably decreasing the application execution time and the queue size, while being slightly more inefficient when concerning aspects of failure tolerance and system scalability. The analysis of the collected measurements has proven the superiority of the Mixed Partitioning Scheme Replication when compared to the performance of generically optimized partitioning schemes. Despite the fact that only a limited subset of configurations was assessed during the performance evaluation phase, the results, validated the simulation observations, allowing to use the model for further estimations and extrapolations towards the requirements of a full scale infrastructure.