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  • How to solve cyclic dependencies in a visitor pattern

    - by Benjamin Rogge
    When programming at work we now and then face a problem with visitors and module/project dependencies. Say you have a class A in a module X. And there are subclasses B and C in module Y. That means that module Y is dependent on module X. If we want to implement a visitor pattern to the class hierarchy, thus introducing an interface with the handle Operations and an abstract accept method in A, we get a dependency from module Y to module X, which we cannot allow for architectural reasons. What we do is, use a direct comparison of the types (i.e. instanceof, since we program in Java), which is not satisfying. My question(s) would be: Do you encounter this kind of problem in your daily work (or do we make poor architectural choices) and if so, how is your approach to solve this?

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  • Capitalizing on JavaScript's prototypal inheritance

    - by keithjgrant
    JavaScript has a class-free object system in which objects inherit properties directly from other objects. This is really powerful, but it is unfamiliar to classically trained programmers. If you attempt to apply classical design patterns directly to JavaScript, you will be frustrated. But if you learn to work with JavaScript's prototypal nature, your efforts will be rewarded. ... It is Lisp in C's clothing. -Douglas Crockford What does this mean for a game developer working with canvas and HTML5? I've been looking over this question on useful design patterns in gaming, but prototypal inheritance is very different than classical inheritance, and there are surely differences in the best way to apply some of these common patterns. For example, classical inheritance allows us to create a moveableEntity class, and extend that with any classes that move in our game world (player, monster, bullet, etc.). Sure, you can strongarm JavaScript to work that way, but in doing so, you are kind of fighting against its nature. Is there a better approach to this sort of problem when we have prototypal inheritance at our fingertips?

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  • Should I think about switching to another platform as a .Net developer? [closed]

    - by A. Karimi
    I’ve been a developer for about 10 years and I’ve almost worked on Microsoft stack. At the last several years I’ve been introduced to some good practices such as IoC and other primary design patterns. Now I feel so much comfortable using these patterns and concepts and I’m very angry why we didn’t do that earlier! They exist and used by many developers since more than 5 years ago but why I and many of my colleagues began using them a little later. As you may know Java developers are more ahead in these fields (concepts, patterns and …) than .Net developers. Am I right? Now the question is, “Why we (as .NET developers) weren’t ahead so much? Isn’t it because we are using Microsoft stack?”. I know ALT.NET but why we are trying make a closed ecosystem open and finding alternatives for Microsoft Echo Chamber, while there are natively open ecosystems like Java!? I've always liked most of the Microsoft works very much but I’m worried about this issue. I am even ask myself should I move to another platform?

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  • Designing a social network with CQRS, graph databases and relational databases in mind

    - by Siraj Mansour
    I have done quite an amount of research on the topic so far, but i couldn't come up with a conclusion to make up my mind. I am designing a social network and during my research i stumbled upon graph databases, i found neo4j pretty interesting for user relations and traversing through nodes. I also thought of using a relational database such as MS-SQL or MySQL to store entity data only and depending on neo4j for connections between entities. Of course this means more work in my application to store and pull data in and out of 2 different sources. My first question : Is using this approach (graph + relational) a good approach for designing my social network keeping in mind that users on social networks don't have to in synch with real data by split second ? What are the positives and negatives of this approach ? My Second question : I've been doing some reading on CQRS and as i understood it is mostly useful for collaborative environments, and environments where users see a lot of "stale" data. social networks has shared comments, events, etc .. and many users query or update the same data. Could CQRS be a helpful approach ? Would it give any performance/scalability benefits or non-useful complexity ? Is it fairly applicable with my possible choice of (graph + relational) databases approach mentioned in the question above ? My purpose is to know if the approaches i have mentioned above seem good enough for the business context.

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  • How to handle "circular dependency" in dependency injection

    - by Roel
    The title says "Circular Dependency", but it is not the correct wording, because to me the design seems solid. However, consider the following scenario, where the blue parts are given from external partner, and orange is my own implementation. Also assume there is more then one ConcreteMain, but I want to use a specific one. (In reality, each class has some more dependencies, but I tried to simplify it here) I would like to instanciate all of this with Depency Injection (Unity), but I obviously get a StackOverflowException on the following code, because Runner tries to instantiate ConcreteMain, and ConcreteMain needs a Runner. IUnityContainer ioc = new UnityContainer(); ioc.RegisterType<IMain, ConcreteMain>() .RegisterType<IMainCallback, Runner>(); var runner = ioc.Resolve<Runner>(); How can I avouid this? Is there any way to structure this so that I can use it with DI? The scenario I'm doing now is setting everything up manually, but that puts a hard dependency on ConcreteMain in the class which instantiates it. This is what i'm trying to avoid (with Unity registrations in configuration). All source code below (very simplified example!); public class Program { public static void Main(string[] args) { IUnityContainer ioc = new UnityContainer(); ioc.RegisterType<IMain, ConcreteMain>() .RegisterType<IMainCallback, Runner>(); var runner = ioc.Resolve<Runner>(); Console.WriteLine("invoking runner..."); runner.DoSomethingAwesome(); Console.ReadLine(); } } public class Runner : IMainCallback { private readonly IMain mainServer; public Runner(IMain mainServer) { this.mainServer = mainServer; } public void DoSomethingAwesome() { Console.WriteLine("trying to do something awesome"); mainServer.DoSomething(); } public void SomethingIsDone(object something) { Console.WriteLine("hey look, something is finally done."); } } public interface IMain { void DoSomething(); } public interface IMainCallback { void SomethingIsDone(object something); } public abstract class AbstractMain : IMain { protected readonly IMainCallback callback; protected AbstractMain(IMainCallback callback) { this.callback = callback; } public abstract void DoSomething(); } public class ConcreteMain : AbstractMain { public ConcreteMain(IMainCallback callback) : base(callback){} public override void DoSomething() { Console.WriteLine("starting to do something..."); var task = Task.Factory.StartNew(() =>{ Thread.Sleep(5000);/*very long running task*/ }); task.ContinueWith(t => callback.SomethingIsDone(true)); } }

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  • Implementing a modern web application with Web API on top of old services

    - by Gaui
    My company has many WCF services which may or may not be replaced in the near future. The old web application is written in WebForms and communicates straight with these services via SOAP and returns DataTables. Now I am designing a new modern web application in a modern style, an AngularJS client which communicates with an ASP.NET Web API via JSON. The Web API then communicates with the WCF services via SOAP. In the future I want to let the Web API handle all requests and go straight to the database, but because the business logic implemented in the WCF services is complicated it's going to take some time to rewrite and replace it. Now to the problem: I'm trying to make it easy in the near future to replace the WCF services with some other data storage, e.g. another endpoint, database or whatever. I also want to make it easy to unit test the business logic. That's why I have structured the Web API with a repository layer and a service layer. The repository layer has a straight communication with the data storage (WCF service, database, or whatever) and the service layer then uses the repository (Dependency Injection) to get the data. It doesn't care where it gets the data from. Later on I can be in control and structure the data returned from the data storage (DataTable to POCO) and be able to test the logic in the service layer with some mock repository (using Dependency Injection). Below is some code to explain where I'm going with this. But my question is, does this all make sense? Am I making this overly complicated and could this be simplified in any way possible? Does this simplicity make this too complicated to maintain? My main goal is to make it as easy as possible to switch to another data storage later on, e.g. an ORM and be able to test the logic in the service layer. And because the majority of the business logic is implemented in these WCF services (and they return DataTables), I want to be in control of the data and the structure returned to the client. Any advice is greatly appreciated. Update 20/08/14 I created a repository factory, so services would all share repositories. Now it's easy to mock a repository, add it to the factory and create a provider using that factory. Any advice is much appreciated. I want to know if I'm making things more complicated than they should be. So it looks like this: 1. Repository Factory public class RepositoryFactory { private Dictionary<Type, IServiceRepository> repositories; public RepositoryFactory() { this.repositories = new Dictionary<Type, IServiceRepository>(); } public void AddRepository<T>(IServiceRepository repo) where T : class { if (this.repositories.ContainsKey(typeof(T))) { this.repositories.Remove(typeof(T)); } this.repositories.Add(typeof(T), repo); } public dynamic GetRepository<T>() { if (this.repositories.ContainsKey(typeof(T))) { return this.repositories[typeof(T)]; } throw new RepositoryNotFoundException("No repository found for " + typeof(T).Name); } } I'm not very fond of dynamic but I don't know how to retrieve that repository otherwise. 2. Repository and service // Service repository interface // All repository interfaces extend this public interface IServiceRepository { } // Invoice repository interface // Makes it easy to mock the repository later on public interface IInvoiceServiceRepository : IServiceRepository { List<Invoice> GetInvoices(); } // Invoice repository // Connects to some data storage to retrieve invoices public class InvoiceServiceRepository : IInvoiceServiceRepository { public List<Invoice> GetInvoices() { // Get the invoices from somewhere // This could be a WCF, a database, or whatever using(InvoiceServiceClient proxy = new InvoiceServiceClient()) { return proxy.GetInvoices(); } } } // Invoice service // Service that handles talking to a real or a mock repository public class InvoiceService { // Repository factory RepositoryFactory repoFactory; // Default constructor // Default connects to the real repository public InvoiceService(RepositoryFactory repo) { repoFactory = repo; } // Service function that gets all invoices from some repository (mock or real) public List<Invoice> GetInvoices() { // Query the repository return repoFactory.GetRepository<IInvoiceServiceRepository>().GetInvoices(); } }

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  • Architecture of interaction modes ("paint tools") for a 3D paint program

    - by Bernhard Kausler
    We are developing a Qt-based application to navigate through and paint on a volume treated as a 3D pixel graphic. The layout of the app consists of three orthogonal slice views on which the user may paint stuff like dots, circles etc. and also erase already painted pixels. Think of a 3D Gimp or MS Paint. How would you design the the architecture for the different interaction modes (i.e. paint tools)? My idea is: use the MVC pattern have a separate controler for every interaction mode install an event filter on all three slice views to collect all incoming user interaction events (mouse, keyboard) redirect the events to the currently active interaction controler I would appreciate critical comments on that idea.

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  • Scalable Architecture for modern Web Development [on hold]

    - by Jhilke Dai
    I am doing research about Scalable architecture for Web Development, the research is solely to support Modern Web Development with flexible architecture which can scale up/down according to the needs without losing any core functionality. By Modern Web I mean to support all the Devices used to access websites, but the loading mechanism for all devices would be different. My quest of architecture is: For PC: Accessing web in PC is faster but it also depends on the Geo-location, so, the application would check by default the capacity of Internet/Browser and load the page according to it. For Mobile: Most of the mobile design these days either hide information or use different version of same application. eg: facebook uses m.facebook.com which is completely different than PC version. Hiding the things from Mobile using JavaScript or CSS is not a solution as it'll consume the bandwidth and make the application slow. So, my architecture research is about Serving one Application, which has different stack. When the application receives the request it'd send the Packaged Stack to the received request. This way the load time for end users would be faster and maintenance of application for developers would be easier. I am researching about for 4-tier(layered) architecture like: Presentation Layer Application Logic Layer -- The main Logic layer which stores the Presentation Stack Business Logic Layer Data Layer Main Question: Have you come across of similar architecture? If so, then can you list the links here, I'm very much interested to learn about those implementations specially in real world scenario. Have you thought about similar architectures and tried your own ideas, or if you have any ideas regarding this, then I urge to share. I am open to any discussions regarding this, so, please feel free to comment/answer.

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  • using sed to replace two patterns within a larger pattern

    - by Hair of the Dog
    Using sed how could I replace two patterns within a larger pattern on a single line? Given a single line of text I want to find a pattern (Let's call this the outer pattern) and then within that outer pattern replace two inner patterns. Here's a one line example of the input text: Z:\source\private\main\developer\foo\setenv.sh(25): export 'FONTCONFIG_PATH'="$WINE_SHARED_SUPPORT/X11/etc/fonts" In the example above the outer pattern is "/^.*([[:digit:]]+):/" which should equal "Z:\source\private\main\developer\foo\setenv.sh(25):" The two inner patterns are "/^[A-Za-z]:/" and "/\/". Another way to phrase my question is: Using sed I know how to perform replacements of a pattern using the "s" command, but how do I limit the range of "s" command so it only works on the portion of the input string up to the "(25):"? The ultimate result I am trying to get is the line of text is transformed into this: /enlistments/source/private/main/developer/foo/setenv.sh(25): export 'FONTCONFIG_PATH'="$WINE_SHARED_SUPPORT/X11/etc/fonts"

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  • Software Architecture: Quality Attributes

    Quality is what all software engineers should strive for when building a new system or adding new functionality. Dictonary.com ambiguously defines quality as a grade of excellence. Unfortunately, quality must be defined within the context of a situation in that each engineer must extract quality attributes from a project’s requirements. Because quality is defined by project requirements the meaning of quality is constantly changing base on the project. Software architecture factors that indicate the relevance and effectiveness The relevance and effectiveness of architecture can vary based on the context in which it was conceived and the quality attributes that are required to meet. Typically when evaluating architecture for a specific system regarding relevance and effectiveness the following questions should be asked.   Architectural relevance and effectiveness questions: Does the architectural concept meet the needs of the system for which it was designed? Out of the competing architectures for a system, which one is the most suitable? If we look at the first question regarding meeting the needs of a system for which it was designed. A system that answers yes to this question must meet all of its quality goals. This means that it consistently meets or exceeds performance goals for the system. In addition, the system meets all the other required system attributers based on the systems requirements. The suitability of a system is based on several factors. In order for a project to be suitable the necessary resources must be available to complete the task. Standard Project Resources: Money Trained Staff Time Life cycle factors that affect the system and design The development life cycle used on a project can drastically affect how a system’s architecture is created as well as influence its design. In the case of using the software development life cycle (SDLC) each phase must be completed before the next can begin.  This waterfall approach does not allow for changes in a system’s architecture after that phase is completed. This can lead to major system issues when the architecture for the system is not as optimal because of missed quality attributes. This can occur when a project has poor requirements and makes misguided architectural decisions to name a few examples. Once the architectural phase is complete the concepts established in this phase must move on to the design phase that is bound to use the concepts and guidelines defined in the previous phase regardless of any missing quality attributes needed for the project. If any issues arise during this phase regarding the selected architectural concepts they cannot be corrected during the current project. This directly has an effect on the design of a system because the proper qualities required for the project where not used when the architectural concepts were approved. When this is identified nothing can be done to fix the architectural issues and system design must use the existing architectural concepts regardless of its missing quality properties because the architectural concepts for the project cannot be altered. The decisions made in the design phase then preceded to fall down to the implementation phase where the actual system is coded based on the approved architectural concepts established in the architecture phase regardless of its architectural quality. Conversely projects using more of an iterative or agile methodology to implement a system has more flexibility to correct architectural decisions based on missing quality attributes. This is due to each phase of the SDLC is executed more than once so any issues identified in architecture of a system can be corrected in the next architectural phase. Subsequently the corresponding changes will then be adjusted in the following design phase so that when the project is completed the optimal architectural and design decision are applied to the solution. Architecture factors that indicate functional suitability Systems that have function shortcomings do not have the proper functionality based on the project’s driving quality attributes. What this means in English is that the system does not live up to what is required of it by the stakeholders as identified by the missing quality attributes and requirements. One way to prevent functional shortcomings is to test the project’s architecture, design, and implementation against the project’s driving quality attributes to ensure that none of the attributes were missed in any of the phases. Another way to ensure a system has functional suitability is to certify that all its requirements are fully articulated so that there is no chance for misconceptions or misinterpretations by all stakeholders. This will help prevent any issues regarding interpreting the system requirements during the initial architectural concept phase, design phase and implementation phase. Consider the applicability of other architectural models When considering an architectural model for a project is also important to consider other alternative architectural models to ensure that the model that is selected will meet the systems required functionality and high quality attributes. Recently I can remember talking about a project that I was working on and a coworker suggested a different architectural approach that I had never considered. This new model will allow for the same functionally that is offered by the existing model but will allow for a higher quality project because it fulfills more quality attributes. It is always important to seek alternatives prior to committing to an architectural model. Factors used to identify high-risk components A high risk component can be defined as a component that fulfills 2 or more quality attributes for a system. An example of this can be seen in a web application that utilizes a remote database. One high-risk component in this system is the TCIP component because it allows for HTTP connections to handle by a web server and as well as allows for the server to also connect to a remote database server so that it can import data into the system. This component allows for the assurance of data quality attribute and the accessibility quality attribute because the system is available on the network. If for some reason the TCIP component was to fail the web application would fail on two quality attributes accessibility and data assurance in that the web site is not accessible and data cannot be update as needed. Summary As stated previously, quality is what all software engineers should strive for when building a new system or adding new functionality. The quality of a system can be directly determined by how closely it is implemented when compared to its desired quality attributes. One way to insure a higher quality system is to enforce that all project requirements are fully articulated so that no assumptions or misunderstandings can be made by any of the stakeholders. By doing this a system has a better chance of becoming a high quality system based on its quality attributes

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  • What Patterns Should I Consider For a Html Widget Generator?

    - by DaveDev
    I'm looking to see if I can design a HtmlHelper extension method that will generate the Html for different types of widgets I want to produce. Each different type of widget implements functionality to get and prepare any data it needs to render. Can anyone suggest any patterns I could refer to for approaches to take? I know there are probably frameworks available that will do this for me, but I thought I'd give it a try anyway. Any points of advice? Thanks

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  • DMV {dm_os_ring_buffers} - Queries to help pinpoint current Issues / usual usage patterns

    - by NeilHambly
    I'm been running some queries (below) to help me identify when I have had time-sensitive performance issues around Memory/CPU, I didn't want to load up additional overhead to the system (unless absolutely neccessary) using traces or profiler  - naturally we have various methods to do this Perfmon counters, DBCC, DMVs etc.. One quick way I like is to run a few DMV queries (normally back in seconds) to help me find those RECENT specific time periods when the system has been substantially changed in some way using, this is using the DMV dm_os_ring_buffers This one helps me identify when I'm expericing Timeout Errors (1222).. modiy code to look for other error as highlight belowDECLARE @ts_now BIGINT,@dt_max BIGINT, @dt_min BIGINT  SELECT @ts_now = cpu_ticks / CONVERT(FLOAT, cpu_ticks_in_ms) FROM sys.dm_os_sys_info SELECT @dt_max = MAX(timestamp), @dt_min = MIN(timestamp)    FROM sys.dm_os_ring_buffers WHERE ring_buffer_type = N'RING_BUFFER_EXCEPTION'  SELECT       record_id      ,DATEADD(ms, -1 * (@ts_now - [timestamp]), GETDATE()) AS EventTime      ,y.Error      ,UserDefined      ,b.description as NormalizedText FROM       (       SELECT       record.value('(./Record/@id)[1]', 'int')                    AS record_id,       record.value('(./Record/Exception/Error)[1]', 'int')        AS Error,       record.value('(./Record/Exception/UserDefined)[1]', 'int')  AS UserDefined,      TIMESTAMP       FROM             (             SELECT TIMESTAMP, CONVERT(XML, record) AS record             FROM sys.dm_os_ring_buffers             WHERE ring_buffer_type = N'RING_BUFFER_EXCEPTION'             AND record LIKE '% %'            ) AS x      ) AS y INNER JOIN sys.sysmessages b on y.Error = b.error WHERE b.msglangid = 1033 and  y.Error = 1222 ORDER BY record_id DESC Sample Output record_id EventTime Error UserDefined NormalizedText 15199195 18/03/2010 14:00 1222 0 Lock request time out period exceeded. 15199194 18/03/2010 14:00 1222 0 Lock request time out period exceeded. 15199193 18/03/2010 14:00 1222 0 Lock request time out period exceeded. 15199192 18/03/2010 14:00 1222 0 Lock request time out period exceeded. 15199191 18/03/2010 14:00 1222 0 Lock request time out period exceeded.  This one helps me identify when I have Unusally High Processing (> 50%) or # Page-FaultsSELECT record.value('(./Record/@id)[1]', 'int') AS record_id,record.value('(./Record/SchedulerMonitorEvent/SystemHealth/SystemIdle)[1]', 'int')              AS SystemIdle,record.value('(./Record/SchedulerMonitorEvent/SystemHealth/ProcessUtilization)[1]', 'int')      AS SQLProcessUtilization,record.value('(./Record/SchedulerMonitorEvent/SystemHealth/UserModeTime)[1]', 'bigint')         AS UserModeTime,record.value('(./Record/SchedulerMonitorEvent/SystemHealth/KernelModeTime)[1]', 'bigint')       AS KernelModeTime,record.value('(./Record/SchedulerMonitorEvent/SystemHealth/PageFaults)[1]', 'bigint')           AS PageFaults,record.value('(./Record/SchedulerMonitorEvent/SystemHealth/WorkingSetDelta)[1]', 'bigint')      AS WorkingSetDelta,record.value('(./Record/SchedulerMonitorEvent/SystemHealth/MemoryUtilization)[1]', 'int')       AS MemoryUtilization,TIMESTAMPFROM (        SELECT TIMESTAMP, CONVERT(XML, record) AS record         FROM sys.dm_os_ring_buffers         WHERE ring_buffer_type = N'RING_BUFFER_SCHEDULER_MONITOR'        AND record LIKE '% %'         ) AS x Example: Showing entries > 50% SQL CPU record_id SystemIdle SQLProcessUtilization UserModeTime KernelModeTime PageFaults WorkingSetDelta MemoryUtilization TIMESTAMP 111916 66 29 36718750 1374843750 21333 -40960 100 7991061289 111917 54 41 50156250 1954062500 26914 -28672 100 7991121290 111918 57 39 42968750 1838437500 30096 20480 100 7991181290 111919 41 53 43906250 2530156250 22088 -4096 100 7991241307 111920 48 45 40937500 2124062500 26395 8192 100 7991301310 111921 52 43 35625000 2052812500 21996 155648 100 7991361311 111922 40 55 36875000 2637343750 33355 -262144 100 7991421311 111923 36 58 44843750 2786562500 47019 28672 100 7991481311 111924 31 64 53437500 3046562500 31027 61440 100 7991541314 111925 36 57 43906250 2711250000 37074 -8192 100 7991601317 111926 52 43 43437500 2060156250 29176 20480 100 7991661318 111927 71 24 33750000 1141250000 14478 16384 100 7991721320 111928 71 23 34531250 1116250000 12711 -20480 100 7991781320 111929 53 36 46562500 1714062500 26684 200704 100 7991841323 Finally one to provide some understanding of the level of memory state changes that are ocuringSELECT record.value('(./Record/@id)[1]', 'int')                                                       AS 'record_id',record.value('(./Record/ResourceMonitor/Notification)[1]', 'VARCHAR(100)')                     AS 'ReservedMemory',record.value('(./Record/ResourceMonitor/Indicators)[1]', 'int')                                AS 'Indicators',record.value('(./Record/ResourceMonitor/Effect/@state)[1]', 'VARCHAR(100)')         + ' - ' + record.value('(./Record/ResourceMonitor/Effect/@reversed)[1]', 'VARCHAR(100)')      + ' - ' + record.value('(./Record/ResourceMonitor/Effect)[1]', 'VARCHAR(100)')                           AS 'APPLY-HIGHPM',record.value('(./Record/ResourceMonitor/Effect/@state)[2]', 'VARCHAR(100)')         + ' - ' + record.value('(./Record/ResourceMonitor/Effect/@reversed)[2]', 'VARCHAR(100)')      + ' - ' + record.value('(./Record/ResourceMonitor/Effect)[2]', 'VARCHAR(100)')                           AS 'APPLY-HIGHPM',record.value('(./Record/ResourceMonitor/Effect/@state)[3]', 'VARCHAR(100)')         + ' - ' + record.value('(./Record/ResourceMonitor/Effect/@reversed)[3]', 'VARCHAR(100)')      + ' - ' + record.value('(./Record/ResourceMonitor/Effect)[3]', 'VARCHAR(100)')                           AS 'REVERT_HIGHPM',record.value('(./Record/MemoryNode/ReservedMemory)[1]', 'int')                                 AS 'ReservedMemory',record.value('(./Record/MemoryNode/CommittedMemory)[1]', 'int')                                AS 'CommittedMemory',record.value('(./Record/MemoryNode/SharedMemory)[1]', 'int')                                   AS 'SharedMemory',record.value('(./Record/MemoryNode/AWEMemory)[1]', 'int')                                      AS 'AWEMemory',record.value('(./Record/MemoryNode/SinglePagesMemory)[1]', 'int')                              AS 'SinglePagesMemory',record.value('(./Record/MemoryNode/CachedMemory)[1]', 'int')                                   AS 'CachedMemory',record.value('(./Record/MemoryRecord/MemoryUtilization)[1]', 'int')                            AS 'MemoryUtilization',record.value('(./Record/MemoryRecord/TotalPhysicalMemory)[1]', 'int')                          AS 'TotalPhysicalMemory',record.value('(./Record/MemoryRecord/AvailablePhysicalMemory)[1]', 'int')                      AS 'AvailablePhysicalMemory',record.value('(./Record/MemoryRecord/TotalPageFile)[1]', 'int')                                AS 'TotalPageFile',record.value('(./Record/MemoryRecord/AvailablePageFile)[1]', 'int')                            AS 'AvailablePageFile',record.value('(./Record/MemoryRecord/TotalVirtualAddressSpace)[1]', 'bigint')                  AS 'TotalVirtualAddressSpace',record.value('(./Record/MemoryRecord/AvailableVirtualAddressSpace)[1]', 'bigint')              AS 'AvailableVirtualAddressSpace',record.value('(./Record/MemoryRecord/AvailableExtendedVirtualAddressSpace)[1]', 'bigint')      AS 'AvailableExtendedVirtualAddressSpace', TIMESTAMPFROM (        SELECT TIMESTAMP, CONVERT(XML, record) AS record         FROM sys.dm_os_ring_buffers         WHERE ring_buffer_type = N'RING_BUFFER_RESOURCE_MONITOR'        AND record LIKE '% %'        ) AS x  

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  • Windows Azure guidance from the Patterns and Practices team

    - by Eric Nelson
    The P&P team have started to share guidance on the Windows Azure Platform.  They plan to group their efforts around: 1. Moving to the Cloud 2. Integrating with the Cloud 3. Leveraging the Cloud First up is a document which explains the capabilities and limitations of Enterprise Library 5.0 Beta 2 in terms of use within .NET applications designed to run with the Windows Azure platform. You can download it here. Related Links: UK Azure Online Community – join today. UK Windows Azure Site Start working with Windows Azure

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  • When should complexity be removed?

    - by ElGringoGrande
    Prematurely introducing complexity by implementing design patterns before they are needed is not good practice. But if you follow all (or even most of) the SOLID principles and use common design patterns you will introduce some complexity as features and requirements are added or changed to keep your design as maintainable and flexible as needed. However once that complexity is introduced and working like a champ when do you removed it? Example. I have an application written for a client. When originally created there where several ways to give raises to employees. I used the strategy pattern and factory to keep the whole process nice and clean. Over time certain raise methods where added or removed by the application owner. Time passes and new owner takes over. This new owner is hard nosed, keeps everything simple and only has one single way to give a raise. The complexity needed by the strategy pattern is no longer needed. If I where to code this from the requirements as they are now I would not introduce this extra complexity (but make sure I could introduce it with little or no work should the need arise). So do I remove the strategy implementation now? I don't think this new owner will ever change how raises are given. But the application itself has demonstrated that this could happen. Of course this is just one example in an application where a new owner takes over and has simplified many processes. I could remove dozens of classes, interfaces and factories and make the whole application much more simple. Note that the current implementation does works just fine and the owner is happy with it (and surprised and even happier that I was able to implement her changes so quickly because of the discussed complexity). I admit that a small part of this doubt is because it is highly likely the new owner isn't going to use me any longer. I don't really care that somebody else will take this over since it has not been a big income generator. But I do care about 2 (related) things I care a bit that the new maintainer will have to think a bit harder when trying to understand the code. Complexity is complexity and I don't want to anger the psycho maniac coming after me. But even more I worry about a competitor seeing this complexity and thinking I just implement design patterns to pad my hours on jobs. Then spreading this rumor to hurt my other business. (I have heard this mentioned.) So... In general should previously needed complexity be removed even though it works and there has been a historically demonstrated need for the complexity but you have no indication that it will be needed in the future? Even if the question above is generally answered "no" is it wise to remove this "un-needed" complexity if handing off the project to a competitor (or stranger)?

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  • Seperating entities from their actions or behaviours

    - by Jamie Dixon
    Hi everyone, I'm having a go at creating a very simple text based game and am wondering what the standard design patterns are when it comes to entities (characters, sentient scenery) and the actions those entities can perform. As an example, I have entity that is a 'person' with various properties such as age, gender, height, etc. This 'person' can also perform some actions such as speaking, walking, jumping, flying, etc etc. How would you seperate out the entity from the actions it can perform and what are some common design patterns that solve this kind of problem?

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  • Integration Patterns with Azure Service Bus Relay, Part 1: Exposing the on-premise service

    - by Elton Stoneman
    We're in the process of delivering an enabling project to expose on-premise WCF services securely to Internet consumers. The Azure Service Bus Relay is doing the clever stuff, we register our on-premise service with Azure, consumers call into our .servicebus.windows.net namespace, and their requests are relayed and serviced on-premise. In theory it's all wonderfully simple; by using the relay we get lots of protocol options, free HTTPS and load balancing, and by integrating to ACS we get plenty of security options. Part of our delivery is a suite of sample consumers for the service - .NET, jQuery, PHP - and this set of posts will cover setting up the service and the consumers. Part 1: Exposing the on-premise service In theory, this is ultra-straightforward. In practice, and on a dev laptop it is - but in a corporate network with firewalls and proxies, it isn't, so we'll walkthrough some of the pitfalls. Note that I'm using the "old" Azure portal which will soon be out of date, but the new shiny portal should have the same steps available and be easier to use. We start with a simple WCF service which takes a string as input, reverses the string and returns it. The Part 1 version of the code is on GitHub here: on GitHub here: IPASBR Part 1. Configuring Azure Service Bus Start by logging into the Azure portal and registering a Service Bus namespace which will be our endpoint in the cloud. Give it a globally unique name, set it up somewhere near you (if you’re in Europe, remember Europe (North) is Ireland, and Europe (West) is the Netherlands), and  enable ACS integration by ticking "Access Control" as a service: Authenticating and authorizing to ACS When we try to register our on-premise service as a listener for the Service Bus endpoint, we need to supply credentials, which means only trusted service providers can act as listeners. We can use the default "owner" credentials, but that has admin permissions so a dedicated service account is better (Neil Mackenzie has a good post On Not Using owner with the Azure AppFabric Service Bus with lots of permission details). Click on "Access Control Service" for the namespace, navigate to Service Identities and add a new one. Give the new account a sensible name and description: Let ACS generate a symmetric key for you (this will be the shared secret we use in the on-premise service to authenticate as a listener), but be sure to set the expiration date to something usable. The portal defaults to expiring new identities after 1 year - but when your year is up *your identity will expire without warning* and everything will stop working. In production, you'll need governance to manage identity expiration and a process to make sure you renew identities and roll new keys regularly. The new service identity needs to be authorized to listen on the service bus endpoint. This is done through claim mapping in ACS - we'll set up a rule that says if the nameidentifier in the input claims has the value serviceProvider, in the output we'll have an action claim with the value Listen. In the ACS portal you'll see that there is already a Relying Party Application set up for ServiceBus, which has a Default rule group. Edit the rule group and click Add to add this new rule: The values to use are: Issuer: Access Control Service Input claim type: http://schemas.xmlsoap.org/ws/2005/05/identity/claims/nameidentifier Input claim value: serviceProvider Output claim type: net.windows.servicebus.action Output claim value: Listen When your service namespace and identity are set up, open the Part 1 solution and put your own namespace, service identity name and secret key into the file AzureConnectionDetails.xml in Solution Items, e.g: <azure namespace="sixeyed-ipasbr">    <!-- ACS credentials for the listening service (Part1):-->   <service identityName="serviceProvider"            symmetricKey="nuR2tHhlrTCqf4YwjT2RA2BZ/+xa23euaRJNLh1a/V4="/>  </azure> Build the solution, and the T4 template will generate the Web.config for the service project with your Azure details in the transportClientEndpointBehavior:           <behavior name="SharedSecret">             <transportClientEndpointBehavior credentialType="SharedSecret">               <clientCredentials>                 <sharedSecret issuerName="serviceProvider"                               issuerSecret="nuR2tHhlrTCqf4YwjT2RA2BZ/+xa23euaRJNLh1a/V4="/>               </clientCredentials>             </transportClientEndpointBehavior>           </behavior> , and your service namespace in the Azure endpoint:         <!-- Azure Service Bus endpoints -->          <endpoint address="sb://sixeyed-ipasbr.servicebus.windows.net/net"                   binding="netTcpRelayBinding"                   contract="Sixeyed.Ipasbr.Services.IFormatService"                   behaviorConfiguration="SharedSecret">         </endpoint> The sample project is hosted in IIS, but it won't register with Azure until the service is activated. Typically you'd install AppFabric 1.1 for Widnows Server and set the service to auto-start in IIS, but for dev just navigate to the local REST URL, which will activate the service and register it with Azure. Testing the service locally As well as an Azure endpoint, the service has a WebHttpBinding for local REST access:         <!-- local REST endpoint for internal use -->         <endpoint address="rest"                   binding="webHttpBinding"                   behaviorConfiguration="RESTBehavior"                   contract="Sixeyed.Ipasbr.Services.IFormatService" /> Build the service, then navigate to: http://localhost/Sixeyed.Ipasbr.Services/FormatService.svc/rest/reverse?string=abc123 - and you should see the reversed string response: If your network allows it, you'll get the expected response as before, but in the background your service will also be listening in the cloud. Good stuff! Who needs network security? Onto the next post for consuming the service with the netTcpRelayBinding.  Setting up network access to Azure But, if you get an error, it's because your network is secured and it's doing something to stop the relay working. The Service Bus relay bindings try to use direct TCP connections to Azure, so if ports 9350-9354 are available *outbound*, then the relay will run through them. If not, the binding steps down to standard HTTP, and issues a CONNECT across port 443 or 80 to set up a tunnel for the relay. If your network security guys are doing their job, the first option will be blocked by the firewall, and the second option will be blocked by the proxy, so you'll get this error: System.ServiceModel.CommunicationException: Unable to reach sixeyed-ipasbr.servicebus.windows.net via TCP (9351, 9352) or HTTP (80, 443) - and that will probably be the start of lots of discussions. Network guys don't really like giving servers special permissions for the web proxy, and they really don't like opening ports, so they'll need to be convinced about this. The resolution in our case was to put up a dedicated box in a DMZ, tinker with the firewall and the proxy until we got a relay connection working, then run some traffic which the the network guys monitored to do a security assessment afterwards. Along the way we hit a few more issues, diagnosed mainly with Fiddler and Wireshark: System.Net.ProtocolViolationException: Chunked encoding upload is not supported on the HTTP/1.0 protocol - this means the TCP ports are not available, so Azure tries to relay messaging traffic across HTTP. The service can access the endpoint, but the proxy is downgrading traffic to HTTP 1.0, which does not support tunneling, so Azure can’t make its connection. We were using the Squid proxy, version 2.6. The Squid project is incrementally adding HTTP 1.1 support, but there's no definitive list of what's supported in what version (here are some hints). System.ServiceModel.Security.SecurityNegotiationException: The X.509 certificate CN=servicebus.windows.net chain building failed. The certificate that was used has a trust chain that cannot be verified. Replace the certificate or change the certificateValidationMode. The evocation function was unable to check revocation because the revocation server was offline. - by this point we'd given up on the HTTP proxy and opened the TCP ports. We got this error when the relay binding does it's authentication hop to ACS. The messaging traffic is TCP, but the control traffic still goes over HTTP, and as part of the ACS authentication the process checks with a revocation server to see if Microsoft’s ACS cert is still valid, so the proxy still needs some clearance. The service account (the IIS app pool identity) needs access to: www.public-trust.com mscrl.microsoft.com We still got this error periodically with different accounts running the app pool. We fixed that by ensuring the machine-wide proxy settings are set up, so every account uses the correct proxy: netsh winhttp set proxy proxy-server="http://proxy.x.y.z" - and you might need to run this to clear out your credential cache: certutil -urlcache * delete If your network guys end up grudgingly opening ports, they can restrict connections to the IP address range for your chosen Azure datacentre, which might make them happier - see Windows Azure Datacenter IP Ranges. After all that you've hopefully got an on-premise service listening in the cloud, which you can consume from pretty much any technology.

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  • Handy SQL Server Functions Series (HSSFS) Part 2.0 - Prelude to Parsing Patterns Properly

    - by Most Valuable Yak (Rob Volk)
    In Part 1 of the series I wrote about 2 lesser-known and somewhat undocumented functions. In this part, I'm going to cover some familiar string functions like Substring(), Parsename(), Patindex(), and Charindex() and delve into their strengths and weaknesses. I'm also splitting this part up into sub-parts to help focus on a particular technique and/or problem with the technique, hence the Part 2.0. Consider this a composite post, or com-post, if you will. (It may just turn out to be a pile of sh_t after all) I'll be using a contrived example, perhaps the most frustratingly useful, or usefully frustrating, function in SQL Server: @@VERSION. Contrived, because there are better ways to get the information (which I'll cover later); frustrating, because of the way Microsoft formatted the value; and useful because it does have 1 or 2 bits of information not found elsewhere. First let's take a look at the output of @@VERSION: Microsoft SQL Server 2008 R2 (RTM) - 10.50.1600.1 (Intel X86) Apr 2 2010 15:53:02 Copyright (c) Microsoft Corporation Developer Edition on Windows NT 5.1 <X86> (Build 2600: Service Pack 3) There are 4 lines, with lines 2-4 indented with a tab character.  In case your browser (or this blog software) doesn't show it correctly, I gave each line a different color.  While this PRINTs nicely, if you SELECT @@VERSION in grid mode it all runs together because it ignores carriage return/line feed (CR/LF) characters.  Not fatal, but annoying. Note that @@VERSION's output will vary depending on edition and version of SQL Server, and also the OS it's installed on.  Despite the differences, the output is laid out the same way and the relevant pieces are in the same order. I'll be using the following view for Parts 2.1 onward, so we have a nice collection of @@VERSION information: create view version(SQLVersion,VersionString) AS ( select 2000, 'Microsoft SQL Server 2000 - 8.00.2055 (Intel X86) Dec 16 2008 19:46:53 Copyright (c) 1988-2003 Microsoft Corporation Developer Edition on Windows NT 5.1 (Build 2600: Service Pack 3)' union all select 2005, 'Microsoft SQL Server 2005 - 9.00.4053.00 (Intel X86) May 26 2009 14:24:20 Copyright (c) 1988-2005 Microsoft Corporation Developer Edition on Windows NT 5.1 (Build 2600: Service Pack 3)' union all select 2008, 'Microsoft SQL Server 2008 R2 (RTM) - 10.50.1600.1 (Intel X86) Apr 2 2010 15:53:02 Copyright (c) Microsoft Corporation Developer Edition on Windows NT 5.1 <X86> (Build 2600: Service Pack 3)' union all select 2005, 'Microsoft SQL Server 2005 - 9.00.3080.00 (Intel X86) Sep 6 2009 01:43:32 Copyright (c) 1988-2005 Microsoft Corporation Standard Edition on Windows NT 5.2 (Build 3790: Service Pack 2)' union all select 2008, 'Microsoft SQL Server 2008 R2 (RTM) - 10.50.1600.1 (X64) Apr 2 2010 15:48:46 Copyright (c) Microsoft Corporation Developer Edition (64-bit) on Windows NT 6.1 <X64> (Build 7600: ) (Hypervisor)' union all select 2008, 'Microsoft SQL Server 2008 R2 (RTM) - 10.50.1600.1 (X64) Apr 2 2010 15:48:46 Copyright (c) Microsoft Corporation Express Edition with Advanced Services (64-bit) on Windows NT 6.1 <X64> (Build 7600: ) (Hypervisor)' ) Feel free to add your own @@VERSION info if it's not already there. In Part 2.1 I'll focus on extracting the SQL Server version number (10.50.1600.1 in first example) and the Edition (Developer), but will have a solution that works with all versions.  Stay tuned!

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