Passive redundancy (warm restart/dual redundancy/triple redundancy). Three widely used tactics for recognizing faults are ping/echo, heartbeat, and exceptions. One method for recognizing faults is to encounter an exception, which is raised when one of the fault classes we discussed in Chapter 4 is recognized. When a fault occurs, the downtime of systems using this tactic is usually milliseconds since the backup is current and the only time to recover is the switching time. The architect can then decide whether to For all i tasks in the architecture design. In the air traffic control system, the secondary decides when to take over from the primary, but in other systems this decision can be done in other components. Patterns are closely related to tactics, as we saw last week. A failure occurs when the system no longer delivers a service that is consistent with its specification; this failure is observable by the system's users. Sometimes a system fails in an unusual manner, with a detectably inconsistent state. In this case, a single bridge or path failure will not make all of the system's components unavailable. Detection Recovery- reintroduction Recovery- preparation and repair Prevention . Other books focus on software and system architecture and product-line development. The tactics we discuss in this section will … It is usually used for control systems in which the outputs to the voter are straightforward and easy to classify as equivalent or deviant, the computations are cyclic, and all redundant components receive equivalent inputs from sensors. It must be rebooted to the appropriate software configuration and have its state initialized when a failure occurs. Recovery reintroduction tactics ! I compare the inferred quality attributes such as reliability, availability, performance, etc. A fault (or combination of faults) has the potential to cause a failure. Hence, availability tactics have been modeled in the RBML-PI add-in component by Kim [19]. A reliable transmission protocol requires all recipients to acknowledge receipt together with some integrity indication such as a checksum. Technical Report. Deriving architectural tactics: A step toward methodical architectural design. Such tactics are shadow operation, state resynchronization, and rollback. 2. 2010. swe320 Software Architecture‎ > ... - Availability Tactics - Performance Tactics ... Increase Availability Resources. Synchronization is the responsibility of the primary component, which may use atomic broadcasts to the secondaries to guarantee synchronization. The design and subsequent implementation of a high availability architecture can be difficult given the vast range of software, hardware and deployment options. RISE/EFTS Joint Int. A transaction is the bundling of several sequential steps such that the entire bundle can be undone at once. This tactic removes a component of the system from operation to undergo some activities to prevent anticipated failures. Architectural tactics are important building blocks of software architecture. An architectural tactic is a design decision that affects how well a software architecture addresses a particular quality attribute. Removal from service. All approaches to maintaining availability involve some type of redundancy, some type of health monitoring to detect a failure, and some type of recovery when a failure is detected. The new data item is stored in a shadow page and the old page becomes a backup for recovery. These and all books in the series address critical problems in software engineering for which practical solutions are available. Google Scholar; Len Bass, Paul Clements, and Rick Kazman. Diversity has no downtime when a failure occurs since the voter continues to operate. Consequently, they are all in the same state. Benefits. Availability Tactics. when tactics are applied to the software architecture [17]. Recall the vocabulary for availability from Chapter 4. What is Software Architecture? Software Architecture Topics Introduction to Architecture Quality Attributes •Availability •Interoperability •Modifiability •Performance •Security •Testability •Usability Other Quality Attributes Patterns and Tactics Architecture in Agile Projects Designing an Architecture Documenting Software Architectures Architecture and Business 5.2 Availability Tactics. good architecture. The voting algorithm can be "majority rules" or "preferred component" or some other algorithm. For example, it may be desirable to use a LAN with a number of parallel paths and place each redundant component in a separate path. Architecture patterns describe the high-level structure and behavior of software systems as the solution to multiple system requirements, whereas tactics are design decisions that improve individual quality attribute concerns. รวมทุกเนื้อหาสาระ ที่เกี่ยวกับ software engineer Availability Tactics - software engineering software engineering Wiley, Chichester (2005) Google Scholar. This statement is clearly correct because tactics are essentially recipes to be followed by the architect. TEDx Talks 4,725,545 views The Software Engineering Institute is a federally ... quirements to the domain of architecture has historically been an art more than a science. 1. One extreme of diversity is that the software for each redundant component is developed by different teams and executes on dissimilar platforms. Then, we'll learn how to combine tactics and patterns. Diversity is expensive to develop and maintain and is used only in exceptional circumstances, such as the control of surfaces on aircraft. If the sender cannot verify that all recipients have received the message, it will resend the message to those components not acknowledging receipt. Recall also that recovery or repair is an important aspect of availability. swe320 Software Architecture. J. Scott Hawker/R. Quality Attributes. Many of the tactics we discuss are available within standard execution environments such as operating systems, application servers, and database management systems. One component issues a ping and expects to receive back an echo, within a predefined time, from the component under scrutiny. 5. 2010. Ping/Echo Heartbeat Exception Voting Active . Achieving Qualities . "Ping/echo" fault detectors can be organized in a hierarchy, in which a lowest-level detector pings the software processes with which it shares a processor, and the higher-level fault detectors ping lower-level ones. What is Software Architecture? Hence these tactics can be easily lead into design decisions. Tactics are fundamental elements of software architecture that an architect employs to meet a system's quality requirements. This tactic depends on the standby components taking over reliably. Still others, from the SEI’s CERT Program, describe technologies and practices needed to manage software and network security risk. Quality Attributes in Software Architecture. Some database systems force a switch with storage of every new data item. Figure 5.13 shows a summary of the runtime tactics to achieve usability. This uses less communications bandwidth than a remote fault detector that pings all processes. Achieving Qualities. This can be used within a group of components mutually responsible for one task. The response from only one component is used (usually the first to respond), and the rest are discarded. § Patterns package tactics. In a highly available distributed system, the redundancy may be in the communication paths. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Heartbeat (dead man timer). 4/14/2012 Garlan Still others, from the SEI’s CERT Program, describe technologies and practices needed to manage software and network security risk. Voting. The heartbeat can also carry data. Software architecture designers inevitably work with both architecture patterns and tactics. If communication has a possibility of being lost (because of noisy or overloaded communication lines), a reliable transmission protocol can be used to recover. It provides an abstraction to manage the system complexity and establish a communication and coordination mechanism among components. Shadow State resynchronization Rollback Removal . Software architecture is the structure or structures of the system, which comprise software elements, the externally visible properties of these elements, and the relationships among them. More specifically, RBML describes tactics as components and connectors with a specific functionality. PATTERNS AND TACTICS 2.3 Software Architecture The notion of software architecture evolved in the early 90s [11], but the origins date back to the late 60s and early 70s, when the software crisis led to the discipline of software engineering. Interoperability is an attribute of the system or part of the system that is responsible for its operation and the transmission of data and its exchange with other external systems. Figure 5.3 summarizes the tactics just discussed. Nevertheless, most architectural strategies have not been developed to … Ping/echo. Tactics are a building block of architecture patterns –more primitive/granular, proven design technique Tactics to Control Stimulus Response. UNIT IV: CREATING AN ARCHITECTURE-II Documenting Software Architectures: Use of Architectural Documentation, Views, Choosing the Relevant Views, Documenting a view, Documentation across … In the fourth week, we will explain how architectural tactics can help you create a software architecture that achieves the predefined requirements. Incremental state upgrades, with periods of service between increments, lead to complicated software. Architectural Structures and view. 9 September 2008 15-313: Foundations of Software Eng ineering Software Architecture 8 Availability Tactics: Fault Recovery • voting • multiple components produce answer • give client the answer with the most votes • most useful for hardware failures •buggy software will fail in the same way • occurs even if built by different teams! The software architecture of a system is the set of structures needed to reason about the system, which comprise software elements, relations among … Tactics for availability: Use replication of the server to cope with downtime. Security is a complex quality property due to its … When a redundant component fails, it may be reintroduced after it has been corrected. If the heartbeat fails, the originating component is assumed to have failed and a fault correction component is notified. If you design, develop, or manage the building of large software systems (or plan to do so), or if you are interested in acquiring such systems for your corporation or government agency, use Software Architecture in Practice, Second Edition, to get up to speed on the current state of software architecture. Tactics impart portability to one design, high performance to another, and integrability to a third. redundancy . In this case, the downtime can usually be limited to seconds. Priyal Walpita. Other books focus on software and system architecture and product-line development. 12 software architecture quality attributes Performance – shows the response of the system to performing certain actions for a certain period of time. Software Architecture in Practice, 3rd Edition ... We call these techniques architectural tactics. The software architecture patterns developed to implement this tactic and to support the modification of the user interface are: - Model-View-Controller - Presentation-Abstraction-Control - Seeheim - Arch/Slinky. If the voter detects deviant behavior from a single processor, it fails it. Tactics that are implemented in existing architectures can have significant impact on the architecture patterns in the system. A checkpoint is a recording of a consistent state created either periodically or in response to specific events. RBML is a UML-based modeling language to describe these manipulations [18]. Start studying Software Architecture In Practice. Security is responsible for the ability of the system to reduce the likelihood of malicious or accidental actions as well as the possibility of theft or loss of information. Results: The satisfaction levels of the quality requirements by a set of architectural patterns and tactics of a software architecture… In this case, the system should be restored using a previous checkpoint of a consistent state and a log of the transactions that occurred since the snapshot was taken. Availability tactics in software architecture ! Availability tactics (2) 6 8.11.2011 . A tactic is a design decision that influences the achievement of a quality attribute response—tactics directly affect the system’s response to some stimulus. He said: Having worked on large-scale systems for more than a decade, if I could… 9–18. § Tactics can refine other tactics. Software architecture designers inevitably work with both architecture patterns and tactics. The exception handler typically executes in the same process that introduced the exception. A failure occurs when the system no longer delivers a service that is consistent with its specification; this failure is observable by the system's users. Availability experts insist that for any system to be highly available, its parts should be well designed and rigorously tested. This message not only acts as a heartbeat but also carries data to be processed. It defines a structured solutionto meet all the technical and operational requirements, while optimizing the common quality attributes like performance and security. Synchronization is performed by ensuring that all messages to any redundant component are sent to all redundant components. Some material in these slides is adapted from Software Architecture in Practice, 3rd edition by Bass, Clements and Kazman. Fault recovery consists of preparing for recovery and making the system repair. Realizing and Refining Architectural Tactics: Availability. An ... CARNEGIE-MELLON UNIV PITTSBURGH PA SOFTWARE ENGINEERING INST, *FAULTS, *SOFTWARE ENGINEERING, FAULT DETECTION, AVAILABILITY, ARCHITECTURE, Collection ... categorization has re-mained stable. The downtime for this tactic is usually minutes. Patterns and Tactics Architecture in Agile Projects Designing an Architecture Documenting Software Architectures Architecture and Business Architecture and Software Product Lines The Brave New World 2 . Transactions. The passive and active redundancy tactics require the component being restored to have its state upgraded before its return to service. In this case one component emits a heartbeat message periodically and another component listens for it. The current availability architectural tactics catalog [4] provides . Further, it involves a set of significant decisions about the organization relat… Most notably David Parnas pointed out the importance of system structure (c.f. Other books focus on software and system architecture and product-line development. Process . 4. Summary of Usability Tactics 30. We then consider fault recovery and finally, briefly, fault prevention. rework the architecture Tactics: optimize repeated processing reduce contention via replication prioritize processing consolidate related workload distribute processing over time minimize the use of shared resources reuse resources and results partition and parallelize scale up or scale out degrade gracefully use asynchronous processing Processes running on redundant processors each take equivalent input and compute a simple output value that is sent to a voter. Availability Tactics, Modifiability Tactics, Performance Tactics, Security Tactics, Testability Tactics, Usability Tactics. Exceptions. The tactics we discuss in this section will keep faults from becoming failures or at least bound the effects of the fault and make repair possible. One component (the primary) responds to events and informs the other components (the standbys) of state updates they must make. A catalog of architectural tactics has now been in use for several years in academia and industry. If it is manual, the system must be designed to support it. This article compares high availability architectures and gives best practices: software vs hardware clustering, shared nothing vs shared disk cluster, application vs virtual machine high availability, synchronous vs asynchronous replication, file vs disk replication, quorum, network load balancing. Recovery reintroduction tactics ! Hence, availability tactics have been modeled in the RBML-PI add-in component by Kim [19]. Availability Tactics (1) Avoid fault become failures Fault Detection between processes • ping/echo check others • heartbeat message/dead man timer be checked by other within a process • exceptions when a fault is recognized 4 (13) - SOFTWARE ARCHITECTURE Quality Attributes (2) - Sven Arne Andreasson - Computer Science and Engineering Not My Problem. More specifically, RBML describes tactics as components and connectors with a specific functionality. shadow tactic state re synchronization and checkpoint rollbackhttps://youtu.be/0nesVXjEWRA★★★★★★★★★★★★★★★★★★★★★★★Thank you For Watching..Hit the Like ButtonAnd Don't Forget to Subscribe our Channel★★★★★★★★★★★★★★★★★★★★★★★Like my fb page : https://www.facebook.com/FaizaWaseemFW/My Playlists:Artificial intellignece tutorial https://www.youtube.com/watch?v=TiRDF7HCSr4\u0026list=PLfX2IHFUV0cEo45AXclPvtcoEIu37VfhDData mining https://www.youtube.com/watch?v=KOsJTrZGVOk\u0026list=PLfX2IHFUV0cEe0-h5JtXOiNsxis_Nw5lHXML tutorial https://www.youtube.com/watch?v=rtb6PWUVyFw\u0026list=PLfX2IHFUV0cEEIMZYXX6N6z4u691LvsiISoftware quality assurance https://www.youtube.com/watch?v=wQ7t1h2qTtM\u0026list=PLfX2IHFUV0cGQqIx0F_RGT5hC5n1KW3wTDatawarehouse tutorial https://www.youtube.com/watch?v=A6yfnPheOo8\u0026list=PLfX2IHFUV0cEnhlvcafMFJ5pbfUaHrRnnFreelancing tutorials https://www.youtube.com/watch?v=z-kpPrqYhEI\u0026list=PLfX2IHFUV0cFrdcma8QO4KF4RsLcbwL7LSPSC past papers https://www.youtube.com/watch?v=pAD20zWRvuA\u0026list=PLfX2IHFUV0cGrNAWo0hosu4gwbIkStXO8 Availability Tactics • Recovery or repair is an important aspect of availability. A previously failed component may be run in "shadow mode" for a short time to make sure that it mimics the behavior of the working components before restoring it to service. One example is rebooting a component to prevent memory leaks from causing a failure. 1 Introducing Tactics § Tactics are intended to control responses to stimuli. Workshop on Software Engineering for Resilient Systems, 2008, pp. Boston, MA: Addison-Wesley, 2003. Spare . Documenting Software Architectures. Tactics are a building block of architecture patterns –more primitive/granular, proven design technique Tactics to ... Software Engineering Availability Scenario Example Availability of the crossing gate controller: Architectural patterns: Use a kind of a model-view controller pattern where the view and the controller is represented in the user interface part and the model is the database. What Is a Software Architecture? In spite of their applicability, they are not effective in self-adaptive software architectures due to their off-line properties; e.g., scenario-based methods. If all of the processors utilize the same algorithms, the redundancy detects only a processor fault and not an algorithm fault. Software architecture has become a widely accepted conceptual basis for the development of nontrivial software in all application areas and by organizations of all sizes. This is often used as the standby client workstation, where the user can move when a failure occurs. Availability tactics 1. —Woody Allen Availability refers to a property of software that it is there and ready to carry … - Selection from Software Architecture in Practice, Third Edition [Book] Achieving Quality Attributes through Tactics. Finally the system availability can be calculated The RF will then propose the tactics most likely to from the results of all the task unavailability values: provide the biggest gain in availability for the software Overall Availability = 1 – (sum of all TUFi + TUJi) architecture. What Is Software Architecture? Less extreme is to develop a single software component on dissimilar platforms. Bass, L.; Clements, P.; & Kazman, R. Software Architecture in Practice, Second Edition. Thus, if the consequence of a failure is extreme, such as potential loss of life, the redundant components can be diverse. Architecture in the life cycle. As you may know, a quote that shaped the way I think about architecture is from Werner Vogels, CTO at Amazon.com. Pattern and reference model. The updating approach will depend on the downtime that can be sustained, the size of the update, and the number of messages required for the update. Spare. Software Architecture in Practice (3rd Edition). Transactions are used to prevent any data from being affected if one step in a process fails and also to prevent collisions among several simultaneous threads accessing the same data. Availability tactics are designed to enable a system to endure system faults so that a service being delivered by the system remains compliant with its specification. Still others, from the SEI’s CERT Program, describe technologies and practices needed to manage software and network security risk. Transactions . This method is used to correct faulty operation of algorithms or failure of a processor and is often used in control systems. 2013. It can also used be used by clients to ensure that a server object and the communication path to the server are operating within the expected performance bounds. Active redundancy is often used in a client/server configuration, such as database management systems, where quick responses are necessary even when a fault occurs. 3. First, we'll look at different types of patterns. Checkpoint/rollback. The Super Mario Effect - Tricking Your Brain into Learning More | Mark Rober | TEDxPenn - Duration: 15:09. Software Engineering Institute, Carnegie-Mellon University. Achieving Qualities: Introducing Tactics, Availability Tactics, Modifiability Tactics, Performance Tactics, Security Tactics, Testability Tactics, Usability Tactics. Architecture patterns describe the high-level structure and behavior of software systems as the solution to multiple system requirements, whereas tactics are design decisions that improve individual quality attribute concerns. 2 Availability Tactics § Goal of availability tactics § Tactics 3 Modifiability Tactics § Goal of modifiability tactics § Tactics 4 Performance Tactics Summary of runtime usability tactics Architectural tactics are fundamental design decisions. Availability With James Scott Ninety percent of life is just showing up. "An architecture should implement all available tactics for all quality attributes that have been identified as ASRs for a system." Chapter 6, describing an air traffic control example, shows a system using it. Peer-review under responsibility of Universal Society for Applied Research doi: 10.1016/j.procs.2015.09.111 ScienceDirect Available online at www.sciencedirect.com International Conference on Communication, Management and Information Technology (ICC 2015) Decision Model for Software Architectural Tactics Selection based on Quality Attributes Requirements Ahmed E. Sabry* … A standby spare computing platform is configured to replace many different failed components. Harrison and P. Avgeriou, Incorporating fault tolerance tactics in software architecture patterns, in Proc. This report describes an updated set of tactics that enable the architect to build availability into a system. State resynchronization. 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