软件体系结构之质量属性

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,Ch.5 Designing the Architecture,Instructor:Tan,Liwei,软件设计与体系结构,reference,Software architecture in practice ch1,ch5,ch7,contents,Designing Architecture:,Achieving Qualities,Architecture Business Cycle(ABC),Creating the architecture,How does the architect create an architecture?(Multiple choice):,By re-using approaches from other architectures,通过重用来自于其他体系结构的方法,By inventing new approaches out of thin air,无中生有地发明新方法,By magic,耍魔术，变一个,Creating the architecture,Architects primarily work by using previously-tried solutions,Large scale:Patterns and styles,Small scale:Tactics,Styles,patterns,and tactics represent conceptual tools in the architects“tool bag.”,Professional architects always keep their tool bag up to date.,风格，模式和策略是体系架构师的工具箱中的概念工具。,专业的体系架构师会不断更新自己的工具箱。,Patterns and styles,The modern term is“patterns”but early papers on software architecture wrote about“software architecture styles.”,Styles in architecture were analogous to styles in houses:,Victorian(multi-story,lots of frilly(,镶褶边的,)wood decorations,tall windows,basically square footprint),Colonial(brick front,pillars or columns,usually symmetrical front),Ranch(single-story,sprawling,not very decorated),大农场,Patterns and styles,Independent component patterns,Communication-processes,Event systems,Implicit invocation,Explicit invocation,Data flow patterns,Batch sequential,Pipe-and-filter,Layers,Data-centered patterns,Blackboard,repository,Virtual machine patterns,Interpreters,Rule-based systems,Call-return patterns,Main program and subroutine,Object oriented,Styles-Patterns,Then,the design patterns community arrived.Architectural styles were clearly just patterns,whose scope of design was the whole system that is,whose scope was the architecture.,Now,architectural patterns is the term in use.,There are books of architectural patterns,e.g.,Buschmann,F.,R.,Meunier,H.Rohnert,P.,Sommerlad,and M.,Stal,.1996.,Pattern-Oriented Software Architecture,Volume 1:A System of Patterns.Wiley.,现在到了设计模式时代，体系结构风格显然就是模式，其设计范围是整个系统。,现在使用的术语是,体系结构模式,。,关于体系结构模式的经典图书,Architectural patterns,These are broadly-scoped solutions to previously encountered problems.,An architectural pattern,is found repeatedly in practice,is a package of design decisions,has known properties that permit reuse,describes a class of architectures,模式会在实际应用中被不断地重复；,它是一个设计决策包；,具有众所周知的可重用的属性；,模式描述了一类体系结构。,Architectural patterns,A pattern is determined and described by,a set of element types,for example,data repositories,processes,and objects,a set of interaction mechanisms or connectors,for example,subroutine calls,events,and pipes,a topological layout of the components,a set of semantic constraints covering topology,element behavior,and interaction mechanisms,In addition,a pattern is described by when and why to use it,模式的描述：组成元素的类型、交互机制或连接器、组件的拓扑规划、语义约束以及何时为什么使用该模式。,Architectural patterns,These are widely known and include many familiar design approaches:,Layered,Pipe-and filter,Client-server,Thin client,Thick client,Asynchronous,Synchronous,N-tier client-server,Etc.,Peer-to peer,Agent-based systems,Service-oriented architectures,Etc.,Observe:,No“universal”list,Patterns can be combined:,e.g.,layered client-server,Patterns can be specialized,Choice of patterns to use is not random!,注意：不可能列出所有的模式；多个模式可以组合；模式可能是专门化的；模式的选择不是随机的。,Tactics,An architectural,tactic is a fine-grained design approach,used to achieve a quality attribute response.,Tactics are the“building blocks”of design from which architectural patterns are created.,体系结构策略是一种可获得质量属性响应的细腻的设计方法。,策略可看作用来搭建体系结构模式的积木块。,Tactics,What is it that imparts portability to one design,high performance to another,and,integrability,to a third?,The achievement of these qualities relies on fundamental design decisions.,A,tactic,is a design decision that influences the control of a quality attribute response.We call a collection of tactics an,architectural strategy.,是什么向外界传达一个设计的灵便性、高性能和可集成性？,依赖于基本的设计决策。,策略是指影响质量属性响应控制的设计决策。策略的集合叫做体系结构战略。,Availability Tactics,可用性策略,keep faults from becoming failures or at least bound the effects of the fault and make repair possible.,使缺陷不要成为失败，或者至少限制缺陷的影响并使修复成为可能。,Availability Tactics,fault detection.,故障检测,Ping/echo,Heartbeat,Exceptions,fault recovery,故障恢复,Fault recovery consists of preparing for recovery and making the system repair.,Voting,Active redundancy,Passive redundancy,Spare,Shadow operation,State resynchronization,Checkpoint/rollback,fault prevention,故障预防,Removal from service,Transactions,Process monitor,Fault detection,Ping/echo,One component issues a ping and expects to receive back an echo,within a predefined time,from the component under scrutiny.,used within a group of components mutually responsible for one task.,used by clients to ensure that a server object and the communication path to the server are operating within the expected performance bounds.,Ping/echo fault detectors can be organized in a hierarchy,in which a lowest-level detector pings the software processes with whi