Το αντικείμενο της παρούσας Διπλωματικής Εργασίας είναι η ανάπτυξη και υλοποίηση μιας εφαρμογής cloud για διαδικτυακές υπηρεσίες. Συγκεκριμένα, η εφαρμογή ονομάζεται My Calendar και αφορά ένα προσωπικό ημερολόγιο. Η εφαρμογή βρίσκεται στην υποδομή «νέφους» της Google και οι τελικοί χρήστες μπορούν να έχουν πρόσβαση στην υπηρεσία μέσω ενός web browser. Αρχικά, γίνεται η εισαγωγή στις έννοιες του cloud computing καθώς και σε αυτές της πλατφόρμας της Google. Στη συνέχεια παρουσιάζεται ο τρόπος υλοποίησης της εφαρμογής και αναλύονται οι λειτουργίες της. Ο εκάστοτε χρήστης, αφού πρώτα δημιουργήσει τον προσωπικό του λογαριασμό, μπορεί να έχει πρόσβαση στην παρεχόμενη υπηρεσία. Η προσπάθεια επικεντρώθηκε κυρίως στην παρουσίαση μιας απλής και εύχρηστης εφαρμογής και δόθηκε ιδιαίτερη έμφαση στο λειτουργικό κομμάτι, ώστε και ο πλέον άπειρος χρήστης να κατανοεί τη διαδικασία και να μπορεί να χρησιμοποιεί την εφαρμογή εύκολα και γρήγορα για τις καθημερινές του εργασίες οργανώνοντας το πρόγραμμά του. / This diploma thesis deals with the development of a cloud application for web services. The application is called “My Calendar” and it is hosted on Google’s infrastructure. Everyone can access it from a simple web browser. First of all, we make an introduction in order to understand the meaning of cloud computing and be able to handle with the Google Cloud Platform. We describe the deployment of the application and we present its operations. Users must register in order to login and, after that, they could enter the interface which enables them to organize their schedule. We tried to focus on creating a user-friendly application and we emphasized on the functionality, so even the most inexperienced user could easily cope with it. As a result, we developed “My Calendar” with a view to everyone who wants to manage his/her scheduled tasks.

Infrastructure as a service (IaaS) Cloud platforms are increasingly used in the IT industry. IaaS platforms are providers of virtual resources from a catalogue of predefined types. Improvements in virtualization technology make it possible to create and destroy virtual machines on the fly, with a low overhead. As a result, the great benefit of IaaS platforms is the ability to scale a virtual platform on the fly, while only paying for the used resources. From a research point of view, IaaS platforms raise new questions in terms of making efficient virtual platform scaling decisions and then efficiently scheduling applications on dynamic platforms. The current thesis is a step forward towards exploring and answering these questions. The first contribution of the current work is focused on resource management. We have worked on the topic of automatically scaling cloud client applications to meet changing platform usage. There have been various studies showing self-similarities in web platform traffic which implies the existence of usage patterns that may or may not be periodical. We have developed an automatic platform scaling strategy that predicted platform usage by identifying non-periodic usage patterns and extrapolating future platform usage based on them. Next we have focused on extending an existing grid platform with on-demand resources from an IaaS platform. We have developed an extension to the DIET (Distributed Interactive Engineering Toolkit) middleware, that uses a virtual market based approach to perform resource allocation. Each user is given a sum of virtual currency that he will use for running his tasks. This mechanism help in ensuring fair platform sharing between users. The third and final contribution targets application management for IaaS platforms. We have studied and developed an allocation strategy for budget-constrained workflow applications that target IaaS Cloud platforms. The workflow abstraction is very common amongst scientific applications. It is easy to find examples in any field from bioinformatics to geology. In this work we have considered a general model of workflow applications that comprise parallel tasks and permit non-deterministic transitions. We have elaborated two budget-constrained allocation strategies for this type of workflow. The problem is a bi-criteria optimization problem as we are optimizing both budget and workflow makespan. This work has been practically validated by implementing it on top of the Nimbus open source cloud platform and the DIET MADAG workflow engine. This is being tested with a cosmological simulation workflow application called RAMSES. This is a parallel MPI application that, as part of this work, has been ported for execution on dynamic virtual platforms. Both theoretical simulations and practical experiments have shown encouraging results and improvements.

Magistro baigiamajame darbe yra analizuojama įmonės perėjimo į debesų kompiuteriją nauda, aprašomi migracijos procesai ir su jais susijusios rizikos. Siekiant patvirtinti arba paneigti debesų kompiuterijos naudą, aprašomas bei pritaikomas debesų kompiuterijos atsiperkamumo modelis. Problemos analizės skyriuje pateikiami moksliniai metodai, kuriais remiantis atliekamas tyrimas, pateikiamas debesų kompiuterijos aprašymas ir supažindinama su debesų kompiuterijos rūšimis bei diegimo moduliais. Taip pat įvertinama debesų kompiuterijos rizika, analizuojamas kainų skirtumas, perėjus iš paprastos sistemos bei supažindinama su reikalavimais techninei įrangai. Be to aprašomas debesų kompiuterijos atsiperkamumo įvertinimo modelis. Teorinių bei eksperimentinių tyrimų skyriuje atskirties analizės pagalba pateikiami įmonėje vykstantys procesai prieš ir po įmonės perėjimo į debesų kompiuteriją. Apskaičiuojami kaštai būtini norint įsirengti nuosavą IT infrastruktūrą ir lyginama su debesų kompiuterijos infrastruktūros kaštais. Pritaikomas investicijų į debesų kompiuteriją atsiperkamumo įvertinimo modelis, kurio pagalba apskaičiuojami įmonės finansiniai rodikliai, tiek įprastoje IT infrastruktūroje, tiek debesų kompiuterijos infrastruktūroje. Darbo pabaigoje pateikiamos išvados, kurios rodo, jog debesų kompiuterijos rizikos yra nereikšmingos, todėl naudingumo sprendimas yra akivaizdus. / Master's thesis analyzes the company's transition to cloud computing benefits, a description of the migration processes and the associated risks. In order to confirm or refute the benefits of cloud computing, there is described and applied cloud computing valuation model for return on investment. In first section of master‘s thesis are described scientific methods by which the study is conducted, presented description of cloud computing and an introduction to cloud computing and the types of deployment modules. There is evaluated cloud computing risks, analyzed difference in prices after transition from usual IT infrastructure and introduces the requirements of the hardware. Also describes the cloud computing valuation model for return on investment. In theoretical and experimental section, with GAP analysis help are provided processes before and after the company's transition to cloud computing. Calculated the costs necessary to install its own IT infrastructure, and compared with the cloud infrastructure costs. After that, there is applied investment in cloud computing payback evaluation model that express the company's financial performance in the normal IT infrastructure and in cloud computing infrastructure. In the end are provided conclusions, which shows that the cloud risk is negligible, so the solution is obvious.

A large number of personal cloud storage systems have emerged in recent years, such as Dropbox, iCloud, Google Drive etc. A common limitation of these system is that the users have to trust the cloud provider not to be malicious. Now we have a Unity block store, which can solve the problem and provide a secure and durable cloud-based block store. However, the base Unity system does not have the concept of file on top of its block device, thus the concurrent operations to different files can cause false sharing problem. In this thesis, we propose UnityFS, a file system built on top of the base Unity system. We design and implement the file system that maintains a mapping between files and a group of data blocks, such that the whole Unity system can support concurrent file operations to different files from multiple user devices in the personal cloud.

A large number of personal cloud storage systems have emerged in recent years, such as Dropbox, iCloud, Google Drive etc. A common limitation of these system is that the users have to trust the cloud provider not to be malicious. Now we have a Unity block store, which can solve the problem and provide a secure and durable cloud-based block store. However, the base Unity system does not have the concept of file on top of its block device, thus the concurrent operations to different files can cause false sharing problem. In this thesis, we propose UnityFS, a file system built on top of the base Unity system. We design and implement the file system that maintains a mapping between files and a group of data blocks, such that the whole Unity system can support concurrent file operations to different files from multiple user devices in the personal cloud.

The growing popularity of mobile platforms is changing the Internet user’s computing experience. Current studies suggest that the traditional ubiquitous computing landscape is shifting towards more enhanced and broader mobile computing platform consists of large number of heterogeneous devices. Smartphones and tablets begin to replace the desktop as the primary means of interacting with IT resources. While mobile devices facilitate in consuming web resources in the form of web services, the growing demand for consuming services on mobile device is introducing a complex ecosystem in the mobile environment. This research addresses the communication challenges involved in mobile distributed networks and proposes an event-driven communication approach for information dissemination. This research investigates different communication techniques such as synchronous and asynchronous polling and long-polling, server-side push as mechanisms between client-server interactions and the latest web technologies namely HTML5 standard WebSocket as communication protocol within a publish/subscribe paradigm. Finally, this research introduces and evaluates a framework that is hybrid of REST and event-based publish/subscribe for operating in the mobile environment.

Message passing interface (MPI) has been widely used for implementing parallel and distributed applications. The emergence of cloud computing offers a scalable, fault-tolerant, on-demand al-ternative to traditional on-premise clusters. In this thesis, we investigate the possibility of adopt-ing the cloud platform as an alternative to conventional MPI-based solutions. We show that cloud platform can exhibit competitive performance and benefit the users of this platform with its fault-tolerant architecture and on-demand access for a robust solution. Extensive research is done to identify the difficulties of designing and implementing an MPI-like framework for Azure cloud platform. We present the details of the key components required for implementing such a framework along with our experimental results for benchmarking multiple basic operations of MPI standard implemented in the cloud and its practical application in solving well-known large-scale algorithmic problems.

Handheld devices are becoming increasingly common, and they have varied range of resources. Mobile Cloud Computing (MCC) allows resource constrained devices to offload computation and use storage capacities of more resourceful surrogate machines. This enables creation of new and interesting applications for all devices. We propose a scheme that constructs a high-performance de-centralized system by a group of volunteer mobile devices which come together to form a resourceful unit (cloudlet). The idea is to design a model to operate as a public-resource between mobile devices in close geographical proximity. This cloudlet can provide larger storage capability and can be used as a computational resource by other devices in the network. The system needs to watch the movement of the participating nodes and restructure the topology if some nodes that are providing support to the cloudlet fail or move out of the network. In this work, we discuss the need of the system, our goals and design issues in building a scalable and reconfigurable system. We achieve this by leveraging the concept of virtual dominating set to create an overlay in the broads of the network and distribute the responsibilities in hosting a cloudlet server. We propose an architecture for such a system and develop algorithms that are requited for its operation. We map the resources available in the network by first scoring each device individually, and then gathering these scores to determine suitable candidate cloudlet nodes. We have simulated cloudlet functionalities for several scenarios and show that our approach is viable alternative for many applications such as sharing GPS, crowd sourcing, natural language processing, etc.

In this dissertation, we focus on the problem of self-management in distributed systems. In this context, we propose a new methodology for reactive self-management based on multiple criteria decision analysis (MCDA). The general structure of the proposed methodology is extracted from the commonalities of the former well-established approaches that are applied in other problem domains. The main novelty of this work, however, lies in the usage of MCDA during the reaction processes in the context of the two problems that the proposed methodology is applied to. In order to provide a detailed analysis and assessment of this new approach, we have used the proposed methodology to design distributed autonomous agents that can provide self-management in two outstanding problems. These two problems also represent the two distinct ways in which the methodology can be applied to self-management problems. These two cases are: 1) independent self management, and 2) coordinated self-management. In the simulation case study regarding independent self-management, the methodology is used to design and implement a distributed resource consolidation manager for clouds, called IMPROMPTU. In IMPROMPTU, each autonomous agent is attached to a unique physical machine in the cloud, where it manages resource consolidation independently from the rest of the autonomous agents. On the other hand, the simulation case study regarding coordinated self-management focuses on the problem of adaptive routing in mobile ad hoc networks (MANET). The resulting system carries out adaptation through autonomous agents that are attached to each MANET node in a coordinated manner. In this context, each autonomous node agent expresses its opinion in the form of a decision regarding which routing algorithm should be used given the perceived conditions. The opinions are aggregated through coordination in order to produce a final decision that is to be shared by every node in the MANET. Although MCDA has been previously considered within the context of artificial intelligence---particularly with respect to algorithms and frameworks that represent different requirements for MCDA problems, to the best of our knowledge, this dissertation outlines a work where MCDA is applied for the first time in the domain of these two problems that are represented as simulation case studies. / Graduate

Modern offices are crowded with personal computers. While studies have shown these to be idle most of the time, they remain powered, consuming up to 60% of their peak power. Hardware based solutions engendered by PC vendors (e.g., low power states, Wake-on-LAN) have proven unsuccessful because, in spite of user inactivity, these machines often need to remain network active in support of background applications that maintain network presence. Recent solutions have been proposed that perform consolidation of idle desktop virtual machines. However, desktop VMs are often large requiring gigabytes of memory. Consolidating such VMs, creates large network transfers lasting in the order of minutes, and utilizes server memory inefficiently. When multiple VMs migrate simultaneously, each VM’s experienced migration latency grows, and this limits the use of VM consolidation to environments in which only a few daily migrations are expected per VM. This thesis introduces partial VM migration, an approach that transparently migrates only the working set of an idle VM, by migrating memory pages on-demand. It creates a partial replica of the desktop VM on the consolidation server by copying only VM metadata, and transferring pages to the server, as the VM accesses them. This approach places desktop PCs in low power state when inactive and resumes them to running state when pages are needed by the VM running on the consolidation server. Jettison, our software prototype of partial VM migration for off-the-shelf PCs, can deliver 78% to 91% energy savings during idle periods lasting more than an hour, while providing low migration latencies of about 4 seconds, and migrating minimal state that is under an order of magnitude of the VM’s memory footprint. In shorter idle periods of up to thirty minutes, Jettison delivers savings of 7% to 31%. We present two approaches that increase energy savings attained with partial VM migration, especially in short idle periods. The first, Context-Aware Selective Resume, expedites PC resume and suspend cycle times by supplying a context identifier at desktop resume, and initializing only devices and code that are relevant to the context. CAESAR, the Context-Aware Selective Resume framework, enables applications to register context vectors that are invoked when the desktop is resumed with matching context. CAESAR increases energy savings in short periods of five minutes to an hour by up to 66%. The second approach, the low power page cache, embeds network accessible low power hardware in the PC, to enable serving of pages to the consolidation server, while the PC is in low power state. We show that Oasis, our prototype page cache, addresses the shortcomings of energy-oriented on-demand page migration by increasing energy savings, especially during short idle periods. In periods of up to an hour, Oasis increases savings by up to twenty times.