Multi Criteria Rank Based Task Scheduling Algorithm for Scientific Workflows in IaaS Cloud Computing

Scientific workflows benefit from the cloud computing paradigm, which offers access to virtual resources provisioned on pay-as-you-go and on-demand basis. Minimizing resources costs to meet user’s budget is very important in a cloud environment. Several optimization approaches have been proposed to improve the performance and the cost of data-intensive scientific Workflow Scheduling (DiSWS) in cloud computing. However, in the literature, the majority of the DiSWS approaches focused on the use of heuristic and metaheuristic as an optimization method. Furthermore, the tasks hierarchy in data-intensive scientific workflows has not been extensively explored in the current literature. Specifically, in this paper, a data-intensive scientific workflow is represented as a hierarchy, which specifies hierarchical relations between workflow tasks, and an approach for data-intensive workflow scheduling applications is proposed. In this approach, first, the datasets and workflow tasks are modeled as a conditional probability matrix (CPM). Second, several data transformation and hierarchical clustering are applied to the CPM structure to determine the minimum number of virtual machines needed for the workflow execution. In this approach, the hierarchical clustering is done with respect to the budget imposed by the user. After data transformation and hierarchical clustering, the amount of data transmitted between clusters can be reduced, which can improve cost and makespan of the workflow by optimizing the use of virtual resources and network bandwidth. The performance and cost are analyzed using an extension of Cloudsim simulation tool and compared with existing multi-objective approaches. The results demonstrate that our approach reduces resources cost with respect to the user budgets.

Energy-efficient execution of the scientific workflow is a challenging task in cloud computing that demands high-performance computing to process growing datasets. Due to the interdependency of tasks in the scientific workflow applications, energy-efficient resource allocation is vital for large-scale applications running on heterogeneous physical machines. Thus, this paper proposes a hybrid heuristic algorithm based energy-efficient cloud computing service (HH-ECO) that offers a significant solution for resource allocation, task scheduling, and optimization of scientific workflows. To ensure the energy-efficient execution, the HH-ECO focuses on executing non-dominant workflow tasks through adaptive mutation and energy-aware migration strategy. HH-ECO adopts the chaotic based particle swarm optimization (C-PSO) principle to optimize the resource allocation, task scheduling, and resource migration by generating the global best plans without local convergence. C-PSO with adaptive mutation avoids the deterioration of global optima while finding the best host to place the virtual machine and ensures an appropriate resource allocation plan. By considering the workflow task precedence relationships during C-PSO based task scheduling, the novel hybrid heuristic method efficiently solves the multi-objective combinatorial optimization problem without dominance among the workflow tasks. The Cloudsim based simulation study delivers superior results compared to the existing methods such as the hybrid heuristic workflow scheduling algorithm (HHWS) and distributed dynamic VM management (DDVM). The proposed approach significantly improves the optimal makespan to 38.27% and energy conservation to 38.06% compared to the existing methods.

Scientific workflows are one of the well-established pillars of modern large-scale computational science. More recently, scientists have started to leverage machine learning (ML) capabilities in their workflows, leading to a new category of scientific workflows, denoted as scientific ML workflows. ML is not only about training and inference, modern ML workflows also involve complex data processing steps before the training can start, which are not often accounted for in most performance studies. In this work, we consider scientific ML workflows, from data pre-processing to training, inference, and model evaluation. We aim to explore (i) how scientific ML workflows differ from more traditional scientific workflows and; (ii) how we can characterize ML workflows both in terms of execution time and data movements when executing on a target cloud platform. We select three representative workflows, ranging from image classification to natural language processing and image segmentation, which have been executed using the academic cloud platform, Chameleon. We build four realistic deployment scenarios for each workflow, which stress data movements during workflow executions. Then, we compare the performance observed when utilizing these different configurations and study how different settings impact overall workflows performance and efficiency when running on cloud infrastructures. Finally, we summarize our findings and discuss performance impacts when augmenting scientific workflows with ML techniques and how traditional workflow management systems can improve their support for such workflows.

Due to economic benefits of cloud computing, consumers have rushed to adopt Cloud Computing. Apart from rushing into cloud, security concerns are also raised. These security concerns cause trust issue in adopting cloud computing. Enterprises adopting cloud, will have no more control over data, application and other computing resources that are outsourced from cloud computing provider. In this paper we propose a novel technique that will not leave consumer alone in cloud environment. Firstly we present theoretical analysis of selected state of the art technique and identified issues in IaaS cloud computing. Secondly we propose Distributed Trust Protocol for IaaS Cloud Computing in order to mitigate trust issue between cloud consumer and provider. Our protocol is distributed in nature that lets the consumer to check the integrity of cloud computing platform that is in the premises of provider's environment. We follow the rule of security duty separation between the premises of consumer and provider and let the consumer be the actual owner of the platform. In our protocol, user VM hosted at IaaS Cloud Computing uses Trusted Boot process by following specification of Trusted Computing Group (TCG) and by utilizing Trusted Platform Module (TPM) Chip of the consumer. The protocol is for the Infrastructure as a Service IaaS i.e. lowest service delivery model of cloud computing.

Scientific Workflows (SWFs) are widely used to model applications in e-Science. In this programming model, scientific applications are described as a set of tasks that have dependencies among them. During the last decades, the execution of scientific workflows has been successfully performed in the available computing infrastructures (supercomputers, clusters and grids) using software programs called Workflow Management Systems (WMSs), which orchestrate the workload on top of these computing infrastructures. However, because each computing infrastructure has its own architecture and each scientific applications exploits efficiently one of these infrastructures, it is necessary to organize the way in which they are executed. \nWMSs need to get the most out of all the available computing and storage resources. Traditionally, scientific workflow applications have been extensively deployed in high-performance computing infrastructures (such as supercomputers and clusters) and grids. But, in the last years, the advent of cloud computing infrastructures has opened the door of using on-demand infrastructures to complement or even replace local infrastructures. However, new issues have arisen, such as the integration of hybrid resources or the compromise between infrastructure reutilization and elasticity, everything on the basis of cost-efficiency.\nThe main contribution of this thesis is an ad-hoc solution for managing workflows exploiting the capabilities of cloud computing orchestrators to deploy resources on demand according to the workload and to combine heterogeneous cloud providers (such as on-premise clouds and public clouds) and traditional infrastructures (supercomputers and clusters) to minimize costs and response time. The thesis does not propose yet another WMS, but demonstrates the benefits of the integration of cloud orchestration when running complex workflows. The thesis shows several configuration experiments and multiple heterogeneous backends from a realistic comparative genomics workflow called Orthosearch, to migrate memory-intensive workload to public infrastructures while keeping other blocks of the experiment running locally. The running time and cost of the experiments is computed and best practices are suggested.

Scientific workflows are widely used to automate scientific data analysis and often involve computationally intensive processing of large datasets on compute clusters. As such, their execution tends to be long-running and resource-intensive, resulting in substantial energy consumption and, depending on the energy mix, carbon emissions. Meanwhile, a wealth of carbon-aware computing methods have been proposed, yet little work has focused specifically on scientific workflows, even though they present a substantial opportunity for carbon-aware computing because they are often significantly delay tolerant, efficiently interruptible, highly scalable and widely heterogeneous. In this study, we first exemplify the problem of carbon emissions associated with running scientific workflows, and then show the potential for carbon-aware workflow execution. For this, we estimate the carbon footprint of seven real-world Nextflow workflows executed on different cluster infrastructures using both average and marginal carbon intensity data. Furthermore, we systematically evaluate the impact of carbon-aware temporal shifting, and the pausing and resuming of the workflow. Moreover, we apply resource scaling to workflows and workflow tasks. Finally, we report the potential reduction in overall carbon emissions, with temporal shifting capable of decreasing emissions by over 80%, and resource scaling capable of decreasing emissions by 67%.

I/O intensive jobs such as stage-in, stage-out or data clean-up jobs account for significant time in execution of scientific workflows. Workflow managers typically add these data management operations as supporting jobs to computational tasks with scheduling emphasis on compute jobs only. We present the integration of the Pegasus Workflow Management System with a Policy Based Data Placement Service (PDPS) to reduce overall workflow execution time. Pegasus delegates all data staging jobs to PDPS, which schedules and executes stage-in jobs based on selected data placement policies and simply executes stage-out and clean-up jobs independent of the workflow execution state. We measure the impact of using PDPS with Pegasus first with the Montage workflow, and then with a synthetic workflow. We enforce two policies and demonstrate the advantage of using PDPS for asynchronous data placement for scientific workflows. Our results show that the influence of PDPS on the overall workflow runtimes is dependent on the data characteristics of the executable workflow and the data placement policy being enforced.

Workflow technology has been adopted in scientific domains to orchestrate and automate scientific processes in order to facilitate experimentation. Such scientific workflows often involve large data sets and intensive computation that necessitate the use of the Grid, which offers supercomputing power through shared distributed resources. To execute a scientific workflow in the Grid, tasks within the workflow that represent steps in the scientific process are assigned to Grid resources for execution. To ensure efficient execution of the workflow, Grid workflow scheduling is required to manage the allocation of Grid resources. Although many Grid workflow scheduling techniques exist, they are mainly designed for the execution of a single workflow. This is not the case with parameter sweep workflows which focus on parametric study and parameter optimisation. A parameter sweep workflow is executed numerous times with different input parameters in order to determine the effect of each parameter combination on the experiment. While executing multiple instances of a parameter sweep workflow in parallel can reduce the time required for the overall execution, this execution introduces new challenges to Grid workflow scheduling. Not only is a scheduling algorithm that is able to manage multiple workflow instances required, but this algorithm also needs the ability to schedule tasks across multiple workflow instances judiciously, as tasks may require the same set of Grid resources. Without appropriate resource allocation, resource competition problem could arise. In the thesis, we propose a new Grid workflow scheduling technique for parameter sweep workflow called the Besom scheduling algorithm. The scheduling decision of our algorithm is based on the resource dependencies of tasks in the workflow, as well as conventional Grid resource-performance metrics. In addition, the proposed technique is extended to handle loop structures in scientific workflows without using existing loop-unrolling techniques. We evaluate the Besom algorithm under a variety of conditions. A comparison between the simulation results of the Besom algorithm and of the three existing Grid workflow scheduling algorithms shows that the Besom algorithm is able to perform better than the existing algorithms for workflows that have complex structures and that involve overlapping resource dependencies of tasks. The Besom scheduling algorithm advances the ability to schedule parallel execution of parameter sweep workflows in the Grid. The outcomes of this thesis justify continuing research in this area to increase our understanding of scheduling multiple Grid workflow instances and to provide support to those involved in parametric study and scientific workflow management.

We consider the problem of optimizing the execution of data-intensive scientific workflows in the Cloud. We address the problem under the following scenario. The tasks of the workflows communicate through files; the output of a task is used by another task as an input file and if these tasks are assigned on different execution sites, a file transfer is necessary. The output files are to be stored at a site. Each execution site is to be assigned a certain percentage of the files and tasks. These percentages, called target weights, are pre-determined and reflect either user preferences or the storage capacity and computing power of the sites. The aim is to place the data files into and assign the tasks to the execution sites so as to reduce the cost associated with the file transfers, while complying with the target weights. To do this, we model the workflow as a hypergraph and with a hypergraph-partitioning-based formulation, we propose a heuristic which generates data placement and task assignment schemes simultaneously. We report simulation results on a number of real-life and synthetically generated scientific workflows. Our results show that the proposed heuristic is fast, and can find mappings and assignments which reduce file transfers, while respecting the target weights.

Most of the large-scale scientific experiments modeled as scientific workflows produce a large amount of data and require workflow parallelism to reduce workflow execution time. Some of the existing Scientific Workflow Management Systems (SWfMS) explore parallelism techniques - such as parameter sweep and data fragmentation. In those systems, several computing resources are used to accomplish many computational tasks in homogeneous environments, such as multiprocessor machines or cluster systems. Cloud computing has become a popular high performance computing model in which (virtualized) resources are provided as services over the Web. Some scientists are starting to adopt the cloud model in scientific domains and are moving their scientific workflows (programs and data) from local environments to the cloud. Nevertheless, it is still difficult for the scientist to express a parallel computing paradigm for the workflow on the cloud. Capturing distributed provenance data at the cloud is also an issue. Existing approaches for executing scientific workflows using parallel processing are mainly focused on homogeneous environments whereas, in the cloud, the scientist has to manage new aspects such as initialization of virtualized instances, scheduling over different cloud environments, impact of data transferring and management of instance images. In this paper we propose SciCumulus, a cloud middleware that explores parameter sweep and data fragmentation parallelism in scientific workflow activities (with provenance support). It works between the SWfMS and the cloud. SciCumulus is designed considering cloud specificities. We have evaluated our approach by executing simulated experiments to analyze the overhead imposed by clouds on the workflow execution time.

Usually, scientists need to execute experiments that demand high performance computing environments and parallel techniques. This is the scenario found in many bioinformatics experiments modeled as scientific workflows, such as phylogenetic and phylogenomic analyses. To execute these experiments, scientists have adopted virtual machines (VMs) instantiated in clouds. Estimating the number of VMs to instantiate is a crucial task to avoid negative impacts on the execution performance and on the financial costs with under or overestimations. Previously, the necessary number of VMs to execute bioinformatics workflows have been estimated by a GRASP heuristic and have been coupled to a Cloud-based Parallel Scientific Workflow Management System. Although this work was a step forward, this approach only provided a static dimensioning. If the characteristics of the environment change (processing capacity, network speed), this static dimensioning may not be suitable. In this way, it is of interest that the dimensioning is adjusted at runtime. To achieve this, we developed a novel framework for monitoring and dynamically dimensioning resources during the execution of parallel scientific workflows in clouds, called Dynamic Dimensioning of Cloud Computing Framework (DDC-F). We have evaluated DDC-F in real executions of bioinformatics workflows. Experiments showed that DDC-F is able to efficiently calculate the number of VMs necessary to execute bioinformatics workflows of Comparative Genomics (CG), also reducing the financial costs, when compared with other works of the related literature.

We present an end-to-end solution for automation of scientific workflow deployment and execution on distributed computing infrastructures. The solution integrates de-facto standard and widely adopted tools, including Terraform and Kubernetes, with our HyperFlow workflow management system. In such a solution, infrastructure providers have abstracted away thanks to generic Kubernetes layer. However, we also support other computing infrastructures, both containerized such as Kubernetes or Amazon ECS, and non-containerized, e.g. Amazon Lambda, in a single unified approach. The resulting solution enables execution of hybrid workflows that utilize multiple computing infrastructures and significantly lowers the complexity related to management of repeatable infrastructures for the execution of scientific workflows and conducting scientific workflow research.

Towards a model-driven transformation framework for scientific workflows

Scientific workflow technology has become a de facto standard in e-Science. It provides a powerful unifying platform that allows scientists to build arbitrarily complicated applications by combining predefined components. With a wide range of components, with the functions ranging from acquiring data inputs from sensors, querying databases, performing data-mining, performing execution, through to visualising the results, this paradigm allows scientists to automate, manage and execute various steps in scientific research. Although powerful, scientific workflow systems still require some programming knowledge, which might not be optimal for many scientists. Recently, scientific workflows have been integrated into the Web, creating workflow-based science gateways. These gateways allow scientists to launch large-scale computational experiments without concern for the underlying complexity of the infrastructure. This approach delivers scientific workflows to more scientists and is becoming increasingly popular. To date, much workflow-based science gateway development effort has been invested in creating user-friendly and secure interfaces to setup parameters, execute workflows and collect results. However, interaction between users and executing workflows has not received a lot of attention. Scientific workflows have typically been executed in batch mode. This model does not work with human-in-the-loop workflows, which require continuous interaction between users and executing workflows. A fundamental contribution of this thesis is to show that gateways can support complex human- workflow interactions, facilitating monitoring and steering of the workflow execution as it progresses. This is important because scientific workflows increasingly require user decisions and interactions at various steps; human decision-making is an important component of real-world computational science. In order to achieve this goal, the thesis presents the design, implementation and demonstration of WorkWays, an interactive workflow-based science gateway for supporting development and execution of human-in-the-loop scientific workflows. WorkWays consists of two distinct frameworks with well defined APIs and bindings: a framework that enables human- workflow interaction and a framework for workflow development and execution.

Cloud computing emerges with high performance computing, massive data storage and easy access of the Internet. By deploying cloud computing, scientific workflows can be more cost-effective. During workflow execution, large volume data transmission may occur among multiple datacenters, hence incur large cost. Traditional approaches aim at finding data placement strategies for individual workflows only to reduce data transmission cost. However, workflows may share some datasets. Therefore, optimal data placement considering individual workflows in isolation is not necessarily optimal for the situation of multiple workflows as a whole. In this paper, by facilitation of Particle Swarm Optimization (PSO), we build a novel data transmission cost model for developing a new multi-datacenter cost-effective data placement strategy. The experimental results show that our strategy is much better than its traditional counterparts.