Architecture Workshop

Transcription

1 TIE / TIE Tietotekniikan projektityö / Project Work on Pervasive Systems Architecture Workshop Hadaytullah Marko Leppänen

2 Workshop Plan Start Technologies Table (Collaboration) Workshop Workshop Groups Questions For Each Workshop Group Warm-up Thoughts (Presentation) Open Discussion End

3 What is software architecture and why it is important? Scenarios or Use cases Logical View An abstract view of the system Development View Process View Architectural Specification Physical View Communication Work Distribution Pre-Dev. Testing Analysis

4 Architecting in Real Logical View Development View Process View Physical View

5 Goals Decisions Architecture D Functional Goals D Non- Functional Goals D D D D D

6 Cross-cutting concerns Architecture

7 Freedom of choice? Dictators Frameworks (Web Frameworks) Eco System (ios MVC, Delegate, Protocol, Singleton) Technologies (AngularJ MVC) Organization of Team

8 update Evaluation: ATAM 1 Stake holders 2 Goals 3 Scenarios 4 Simulate Analyze 5 Satisfied? Architecture

9 Designing and Documenting using UML Scenarios Use Cases Behavior Sequence Diagram Structure Class Diagram Behavior State Diagram Development Package Diagram Behavior Activity Diagram Physical Deployment Diagram

10 Integration & Testing Big Bang Putting all together at once and testing Why? Feeling lazy? No continuous integration tools? Don t do it. Why? Time consuming Whose component is failing? Origin of bugs is hard to trace Trust me, there will be many bugs! Continuous Develop, test and deploy as you go Why? It makes more sense Tools available, automated unit testing scripts Do it. Why? Automatable If build FAILS, the last commit is the potential culprit Automated deployment, if build PASSES Less last moments stress

11 This is how you would do it! Initial Architecture Coding Black hole

12 Workshop

13 Technologies G2 Node-RED Node.js HTML5 AngularJS REST JSON MongoDB Linux Docker G8 BeagleBone Black Raspberry Pi Node.js AngularJS PostgreSQL Bookshelf.js Bootstrap G3 G6 Flask flask-babel flask-sqlalchemy Bootstrap d3.js AngularJS PostgreSQL Git Back-end techology: Node.js Database: Sequelize Front-end technology: Angular.js Deployment: Heroku G5 PHP JavaScript jquery Bootstrap CodeIgniter IIS Express server SQL server Git

14 Three Tier Architecture Client-Server Client Server Database Modifiability Design Pattern Different Technologies for each tier can be used Each tier can change independent of others Efficiency may suffer Poor network speed or bandwidth Reliability R= Client Reliability * Server Reliability * DB Reliability Security Encrypt the messages Usually encryption is by default supported

15 Why Model-View-Controller? User Interface Synch Data View View Perform action on view Data Changed Notification User action Get New Data 1 Model Update Data 2 3 Controller 4 5 MVC = Separation between Views and Application or Business Logic Business logic and Views can change independently Each view can show the data in a different way (e.g., charts, table etc.) There can be different Views for different devices (Mobile, Tablet, PC, TV etc.)

16 Questions (G3) How to distribute the work among the project team when the application's architecture is not yet modular and requires work on basic parts? (G2) What are good practices of documenting the architecture and why the customer might need it? (G5) What are the main pros and cons of using MVC architecture for designing a web service system? Which other arcitectural styles work well for web systems? (G5) How to decide which parts of the web application should run on the server, and which ones on the browser? (G6) Should it be the backend or the client that fetches data from third party REST interface? (In what kind of situations?)

17 Questions (G7)What kind of software architecture evaluation methods would be feasible on this project course? (G7) In a web application, where the backend is a REST API to a relational SQL database: What kind of software architecture would allow synchronising the data between clients efficiently? (Like in google docs for example: one user edits the document and others see the changes almost instantaneously.) (G8) Is a formal architecture evaluation really necessary, when developing a relatively small web application? (G8) What are some usual problems/considerations with tried and true web-architectures? For example nodejs backend with a REST-api and angularjs frontend.

18 Questions Why MVC models are getting more and more popular in web front ends? How single page application web pages affect information security when combined with MVC front end? E.g. Admin page implementation. How to manage the amount of javascript files on big web pages and their depedencies? Is there any options? When using Entity-Component design pattern for high-level architechture (for example when using Unity), what approach should be taken for project-spanning architechture? When the project begins with proof of concept and heavy prototyping, what is the optimal point for rebooting with production quality architechture or should it emerge gradually?

19 NOTE Group Hardware Client Messaging Server ORM Database Version Control Deployment G1 G2 G3 G4 G5 G6 G7 G8 - The assistants have filled in some missing technologies and marked them with "?" mark. Remove the "?" mark if you are using the technology or - If your product does not fit into Client-Server paradigm, please add free form text stating your technologies to the table. - Deployment: Does your tool support continuous integration? if Yes, please add "(Continuous)". Rasberry Pi (Embedded) BealgleBoneBlack, HTML5, Backbone.js on web server + Python on RPi JSON Node.js Sequelize.js MySQL Git Raspberry Pi HTML5, AngularJS, (Embedded) Bootstrap?, jquery? JSON Node.js, REST? MongoDB Git? Google glass (Embedded) Java JSON? REST, Node.js??? Bitbucket? PC/Mac/ Mobile/ AngularJS, HTML5?, Embedded? Bootstrap?, jquery? JSON? Node.js, REST? Sequelize.js? Git? PC/Mobile(tablet) PC/Mac/ Mobile/ Embedded? PC/Mac/ Mobile/ Embedded? PC/Mac/ Mobile Docker + SD card image Docker (Continuous?) Heroku (Continuous?) HTML, Javascript, jquery, Bootstrap JSON PHP(CodeIgniter ),IIS Express Server CodeIgniter's "Active record" SQL Server Git? Flask, d3.js, AngularJS, Bootstrap, Html5? JSON??? PostgreSql Git? HTML5, AngularJS, REST w/ C#, Bootstrap, jquery JSON? Apache Custom PostgreSql Git? HTML5, AngularJS, Bootstrap JSON Node.js, REST Bookshelf.js PostgreSql Git? G9 PC/Mac C#, Unity Java, HTML5, CSS, G10 Mobile / Desktop Javascript, AngularJS JSON Bitbucket/ SourceTree? Python(Django), REST, MongoDB Git?

20 Theoretical 1. (G3) How to distribute the work among the project team when the application's architecture is not yet modular and requires work on basic parts? - Define the architecture and interfaces and distribute them. - Coming up with initial architecture should not be that challenging. - Design for the team or team for the design, choose what is possible for you. In this course work, perhaps, teams are already fixed, therefore your design should follow the team structure (keeping in mind team member skills). 2. (G2) What are good practices of documenting the architecture and why the customer might need it? - Document minimum as needed according to customer demands. Use figures to show big picture of the architecture. - Agile manifesto view: Working software over comprehensive documentation. See: A. Rüping: Agile Documentation - It should be possible to trace the architectural choices back to the goals or requirements. Therefore, not only document the architecture but also the decisions or rationale that explains why the architecture is the way it is. It is good for transfer of knowledge when the architect leaves the teams in companies. Tech savvy customer may want to see the architecture to confirm that it delivers what he or she has demanded from you. Customer may internally conduct (or demand from you) formal evaluation/review of the architecture for further satisfaction. 3. When the project begins with proof of concept and heavy prototyping, what is the optimal point for rebooting with production quality architecture or should it emerge gradually? - If something is expected to change in future, make is modifiable. - Build your MVP first and then see if it can be extended without so many problems, otherwise go for next prototype. Throwing away might be sensible if fixing cost more - An old saying states that PoC s and prototypes should always be thrown away. When starting the actual product, PoCs and prototypes work as ideas how to design the actual architecture. So, play with prototypes, make quick n dirty solutions, but when you have learned enough, start with a scratch. 4. (G7)What kind of software architecture evaluation methods would be feasible on this project course? (G8) Is a formal architecture evaluation really necessary, when developing a relatively small web application? - Full-scale evaluation might take too much time to deliver any real value for anyone. However, could some things from evaluation methods be applied to your context too?

21 For example, documenting arch. decisions and their rationale for future use? Could scenarios help to facilitate discussion with stakeholders? 5. (G10) Should the architecture be designed so that it's easily tested even if it could severly cripple other aspects of the architecture? And how much weight should be given for the testability when planning the architecture? - If your tools dictate wrong methods that will cripple the architecture, try finding other tools that may work for your architecture. - Architecture is enabler of multiple cross-cutting concerns (functionality vs testability vs efficiency vs reliability). Find a balance among them or overweight one over another according to your application s needs or stakeholders interests. Patterns 6. MVC: (G5) What are the main pros and cons of using MVC architecture for designing a web service system? Which other architectural styles work well for web systems? How single page application web pages affect information security when combined with MVC front end? E.g. Admin page implementation. - See workshop slides on MVC for introduction to the pattern. - MVC alternative- Presentation Abstraction Control (PAC) Design Pattern (Agents hierarchy + separate MVC per view or agent at every level, no connection between Model:Abstraction and Views:Presentation, Centralized at Controller) - Security; Each view is restricted to show (and receive) some part of the information available in the model. This inherently enables some level of secure data visualization. 7. CLIENT-SERVER: (G5) How to decide which parts of the web application should run on the server, and which ones on the browser? - Computation intensive parts and databases usually go to the server side. - See workshop slides on Three Tier Architecture. 8. (G6) Should it be the backend or the client that fetches data from third party REST interface? (In what kind of situations?) - Technically it should be possible to access a third part REST API from your client unless the owner of the API restricts such access. Another option is to build a proxy server for the third party API, if allowed.

22 Technical 9. (G7) In a web application, where the backend is a REST API to a relational SQL database: What kind of software architecture would allow synchronising the data between clients efficiently? (Like in google docs for example: one user edits the document and others see the changes almost instantaneously.) - use sockets - This approach works for cloud based apps. All major ecosystems have their own solutions. e.g., Google cloud messaging and their Backup API for Android OS. icloud support data synchronization as a built-in feature. Microsoft Sync Framework for SQL server. 10. (G8) What are some usual problems/considerations with tried and true webarchitectures? For example node.js backend with a REST-api and angular.js frontend. - NodeJS and its technologies are still immature, so keep expectations a bit lower. For example, is NodeJS and technologies built upon it are powerful enough to support the incoming traffic or a large database? How many parallel connections can it support without crashing? Are the NodeJS ORMs really good as traditional tools like HIBERNATE etc. 11. How to manage the amount of javascript files on big web pages and their dependencies? Is there any options? - TaskRunner, Grunt (watch out for circular dependencies) - RequireJS 12. (G10) An external system contains large amounts of location based data which is accessed through an API which doesn't fit our needs. Could there be any other viable options than to replicate the entire external database which will make the size of our own database huge? - If the owner s API provide restrictive access then even your own API has to obey such restrictions. Otherwise, it might be time consuming, however, could be possible to adapt the external API for you needs by creating a Proxy server? (OR) Partially or fully replicate the database on your own server and write a fresh API satisfying your application s needs, if possible. Other

23 13. When using Entity-Component design pattern for high-level architecture (for example when using Unity), what approach should be taken for project-spanning architecture? - Unity dictates it own solutions and constraints