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  • Client-Server connection response timeout issues

    - by Srikar
    User creates a folder in client and in the client-side code I hit an API to the server to make this persistent for that user. But in some cases, my server is so busy that the request timesout. The server has executed my request but timedout before sending a response back to client. The timeout set is 10 seconds in client. At this point the client thinks that server has not executed its request (of creating a folder) and ends up sending it again. Now I have 2 folders on the server but the user has created only 1 folder in the client. How to prevent this? One of the ways to solve this is to use a unique ID with each new request. So the ID acts as a distinguisher between old and new requests from client. But this leads to storing these IDs on my server and do a lookup for each API call which I want to avoid. Other way is to increase the timeout duration. But I dont want to change this from 10 seconds. Something tells me that there are better solutions. I have posted this question in stackoverflow but I think its better suited here. UPDATE: I will make my problem even more explicit. The client is a webbrowser and the server is running nginx+django+mysql (standard stack). The user creates a folder in webbrowser. As a result I need to hit a server API. The API call responds back, thereby client knows API call was success. This is normal scenario. Sometimes though, server successfully completes the API request but the client-side (webbrowser) connection timesout before server can respond back. The client has no clue at this point. The user thinks the request was a fail & clicks again. This time it was a success but when the UI refreshes he sees 2 folders. I want to remedy this situation.

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  • Distinguishing between UI command & domain commands

    - by SonOfPirate
    I am building a WPF client application using the MVVM pattern that provides an interface on top of an existing set of business logic residing in a library which is shared with other applications. The business library followed a domain-driven architecture using CQRS to separate the read and write models (no event sourcing). The combination of technologies and patterns has brought up an interesting conundrum: The MVVM pattern uses the command pattern for handling user-interaction with the view models. .NET provides an ICommand interface which is implemented by most MVVM frameworks, like MVVM Light's RelayCommand and Prism's DelegateCommand. For example, the view model would expose a number of command objects as properties that are bound to the UI and respond when the user performs actions like clicking buttons. Many implementations of the CQRS use the command pattern to isolate and encapsulate individual behaviors. In my business library, we have implemented the write model as command / command-handler pairs. As such, when we want to do some work, such as create a new order, we 'issue' a command (CreateOrderCommand) which is routed to the command-handler responsible for executing the command. This is great, clearly explained in many sources and I am good with it. However, take this scenario: I have a ToolbarViewModel which exposes a CreateNewOrderCommand property. This ICommand object is bound to a button in the UI. When clicked, the UI command creates and issues a new CreateOrderCommand object to the domain which is handled by the CreateOrderCommandHandler. This is difficult to explain to other developers and I am finding myself getting tongue-tied because everything is a command. I'm sure I'm not the first developer to have patterns overlap like this where the naming/terminology also overlap. How have you approached distinguishing your commands used in the UI from those used in the domain? (Edit: I should mention that the business library is UI-agnostic, i.e. no UI technology-specific code exists, or will exists, in this library.)

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  • AngularJS: structuring a web application with multiple ng-apps

    - by mg1075
    The blogosphere has a number of articles on the topic of AngularJS app structuring guidelines such as these (and others): http://www.johnpapa.net/angular-app-structuring-guidelines/ http://codingsmackdown.tv/blog/2013/04/19/angularjs-modules-for-great-justice/ http://danorlando.com/angularjs-architecture-understanding-modules/ http://henriquat.re/modularizing-angularjs/modularizing-angular-applications/modularizing-angular-applications.html However, one scenario I have yet to come across for guidelines and best practices is the case where you have a large web application containing multiple "mini-spa" apps, and the mini-spa apps all share a certain amount of code. I am not referring to the case of trying to have multiple ng-app declarations on the same page; rather, I mean different sections of a large site that have their own, unique ng-app declaration. As Scott Allen writes in his OdeToCode blog: One scenario I haven't found addressed very well is the scenario where multiple apps exist in the same greater web application and require some shared code on the client. Are there any recommended approaches to take, pitfalls to avoid, or good sample structures of this scenario that you can point to?

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  • can you have too many dto/bo - mapping method

    - by Fredou
    I have a windows service, 2 web services and a web interface that need to follow the same path (data wise). So I came up with two ways of creating my solution. My concern is the fact that the UI/WS/etc will have their own kind of DTO (let's say the model in ASP.Net MVC) that should be mapped to a DTO so the SL can then map it to a BO then mapping it to the proper EF6 DTO so that I can save it in a database. So I'm thinking of doing it this way to remove one level of mapping. Which one should I take? Or is there a 3rd solution?

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  • designing classes with similar goal but widely different decisional core

    - by Stefano Borini
    I am puzzled on how to model this situation. Suppose you have an algorithm operating in a loop. At every loop, a procedure P must take place, whose role is to modify an input data I into an output data O, such that O = P(I). In reality, there are different flavors of P, say P1, P2, P3 and so on. The choice of which P to run is user dependent, but all P have the same finality, produce O from I. This called well for a base class PBase with a method PBase::apply, with specific reimplementations of P1::apply(I), P2::apply(I), and P3::apply(I). The actual P class gets instantiated in a factory method, and the loop stays simple. Now, I have a case of P4 which follows the same principle, but this time needs additional data from the loop (such as the current iteration, and the average value of O during the previous iterations). How would you redesign for this case?

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  • Is having functionality in DB a road block to scalability?

    - by Estefany Velez
    I may not be able to give the right title to the question. But here it is, We are developing financial portal for wealth management. We are expecting over 10000 clients to use the application. The portal calculates various performance analytics based on the the technical analysis of the stock market. We developed lot of the functionality through Stored procedures, user defined functions, triggers etc. through Database. We thought we can gain huge performance boost doing stuff directly in database than through C# code. And we actually did get a huge performance boost. When I tried to brag about the achievement to our CTO, he counter questioned my decision of having functionality implemented in database rather than code. According to him such applications suffer scalability problems. In his words "These days things are kept in memory/cache. Clustered data is hard to manage over time. Facebook, Google have nothing in database. It is the era of thin servers and thick clients. DB is used only to store plain data and functionality should be completely decoupled from the database." Can you guys please give me some suggestions as to whether what he says is right. How to go about architect such an application?

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  • constructor should not call methods

    - by Stefano Borini
    I described to a colleague why a constructor calling a method is an antipattern. example (in my rusty C++) class C { public : C(int foo); void setFoo(int foo); private: int foo; } C::C(int foo) { setFoo(foo); } void C::setFoo(int foo) { this->foo = foo } I would like to motivate better this fact through your additional contribute. If you have examples, book references, blog pages, or names of principles, they would be very welcome. Edit: I'm talking in general, but we are coding in python.

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  • Go/Obj-C style interfaces with ability to extend compiled objects after initial release

    - by Skrylar
    I have a conceptual model for an object system which involves combining Go/Obj-C interfaces/protocols with being able to add virtual methods from any unit, not just the one which defines a class. The idea of this is to allow Ruby-ish open classes so you can take a minimalist approach to library development, and attach on small pieces of functionality as is actually needed by the whole program. Implementation of this involves a table of methods marked virtual in an RTTI table, which system functions are allowed to add to during module initialization. Upon typecasting an object to an interface, a Go-style lookup is done to create a vtable for that particular mapping and pass it off so you can have comparable performance to C/C++. In this case, methods may be added /afterwards/ which were not previously known and these new methods allow newer interfaces to be satisfied; while I like this idea because it seems like it would be very flexible (disregarding the potential for spaghetti code, which can happen with just about any model you use regardless). By wrapping the system calls for binding methods up in a set of clean C-compatible calls, one would also be able to integrate code with shared libraries and retain a decent amount of performance (Go does not do shared linking, and Objective-C does a dynamic lookup on each call.) Is there a valid use-case for this model that would make it worth the extra background plumbing? As much as this Dylan-style extensibility would be nice to have access to, I can't quite bring myself to a use case that would justify the overhead other than "it could make some kinds of code more extensible in future scenarios."

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  • My Last "Catch-Up" Post for 2010 Content

    - by KKline
    I did a lot of writing in 2010. Unfortunately, I didn't do a good job of keeping all of that writing equally distributed throughout all of the channels where I'm active. So here are a few more posts from my blog, put on-line during the months of November and December 2010, that I didn't get posted here on SQLBlog.com: 1. It's Time to Upgrade! So many of my customers and many of you, dear readers, are still on SQL Server 2005. Join Kevin Kline , SQL Server MVP and SQL Server Technology Strategist...(read more)

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  • Import SSIS Project in Denali CTP1

    For years Analysis Services has had the ability to take an existing database from a server and reverse engineer it into a BIDS project.  This is extremely useful when all you have is the running instance of the database and the project that created it has long since disappeared.  Reverse engineering has never been a feature of SSIS until now. Let me walk you through the simple steps. The first step is that you obviously have to have a project deployed to an SSIS Catalog.  I will do a video on this soon but in case you can’t wait then my good buddy Jamie Thomson has written it up here As you can see I have a project called imaginatively “Denali1” with one package “Package.dtsx” The next thing we need to do is fire up BIDS and choose the right project type (Integration Services Import Project) Now we just follow the wizard.  We make sure we specify on which server to find the Catalog and in which folder to look for the project. Next the setting are validated and we are greeted with the familiar review screen before the creation of our new project from the deployed project happens Hit Import and away we go The result is just what we wanted.

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  • What is the best website width? [on hold]

    - by Salvis Dišlers
    What is the best website width? I can't decide between 1200px max-width and 1236px....with 300px sidebar as enough or 320px? I personally like wide website, my current website is 1236px; but I hear it's considered very wide for eyesight and all those gadgets keeping in mind... The website is for reading - I mean, mostly articles with around 3000 words on average per page, so no matter - whether they look wide, whether they love to scroll down :) Also - what to decide about Banner size / sidebar? Probably the 300px I can put a 300px banner, but on 320px sidebar I could put 336px banner, if necessary...

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  • Making Modular, Reusable and Loosely Coupled MVC Components

    - by Dusan
    I am building MVC3 application and need some general guidelines on how to manage complex client side interaction between my components. Here is my definition of one component in general way: Component which has it's own controller, model and view. All of the component's logic is placed inside these three parts and component is sort of "standalone", it contains it's own form, data needed for interaction, updates itself with Ajax and so on. Beside this internal logic and behavior of the component, it needs to be able to "Talk" to the outside world. By this I mean it should provide data and events (sort of) so when this component gets embedded in pages can notify other components which then can update based on the current state and data. I have an idea to use client ViewModel (in java-script) which would hookup all relevant components on page and control interaction between them. This would make components reusable, modular - independent of the context in which they are used. How would you do this, I am a bit stuck as I do not know if this is a good approach and there is a technical possibility to achieve this using java-script/jquery. The confusing part is about update via Ajax, how to ensure that component is properly linked to ViewModel when component is Ajax updated (or even worse removed or dynamically added). Also, how should this ViewModel be constructed and which technicalities to use here and in components to work as synergy??? On the web, I have found the various examples of the similar approach, but they are oversimplified (even for dummies) or over specific and do not provide valuable resource or general solution for this kind of implementation. If you have some serious examples it would be, also, very helpful. Note: My aim is to make interactions between many components on the same page simpler and more robust and elegant.

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  • Who should control navigation in an MVVM application?

    - by SonOfPirate
    Example #1: I have a view displayed in my MVVM application (let's use Silverlight for the purposes of the discussion) and I click on a button that should take me to a new page. Example #2: That same view has another button that, when clicked, should open up a details view in a child window (dialog). We know that there will be Command objects exposed by our ViewModel bound to the buttons with methods that respond to the user's click. But, what then? How do we complete the action? Even if we use a so-called NavigationService, what are we telling it? To be more specific, in a traditional View-first model (like URL-based navigation schemes such as on the web or the SL built-in navigation framework) the Command objects would have to know what View to display next. That seems to cross the line when it comes to the separation of concerns promoted by the pattern. On the other hand, if the button wasn't wired to a Command object and behaved like a hyperlink, the navigation rules could be defined in the markup. But do we want the Views to control application flow and isn't navigation just another type of business logic? (I can say yes in some cases and no in others.) To me, the utopian implementation of the MVVM pattern (and I've heard others profess this) would be to have the ViewModel wired in such a way that the application can run headless (i.e. no Views). This provides the most surface area for code-based testing and makes the Views a true skin on the application. And my ViewModel shouldn't care if it displayed in the main window, a floating panel or a child window, should it? According to this apprach, it is up to some other mechanism at runtime to 'bind' what View should be displayed for each ViewModel. But what if we want to share a View with multiple ViewModels or vice versa? So given the need to manage the View-ViewModel relationship so we know what to display when along with the need to navigate between views, including displaying child windows / dialogs, how do we truly accomplish this in the MVVM pattern?

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  • Is it evil to model JSON responses to classes when they are mostly smilar?

    - by Aybe
    Here's the problem : While implementing a C# wrapper for an online API (Discogs) I've been faced to a dilemma : quite often the responses returned have mostly similar members and while modeling these responses to classes, some questions surfaces on which way to go would be the best. Example : Querying for a 'release' or a 'master' will return an object that contains an array of 'artist', however these 'artists' do not exactly have the same members. Currently I decided to represent these 'artists' as a single 'Artist' class, against having respective 'ReleaseArtist' and 'MasterArtist' classes which soon becomes very confusing even though another problem arises : when a category (master or release) does not return these members, they will be null. Though it might sound confusing as well I find it less confusing than the former situation as I've tackled the problem by simply not showing null members when visualizing these objects. Is this the right approach to follow ? An example of these differences : public class Artist { public List<Alias> Aliases { get; set; } public string DataQuality { get; set; } public List<Image> Images { get; set; } public string Name { get; set; } public List<string> NameVariations { get; set; } public string Profile { get; set; } public string Realname { get; set; } public string ReleasesUrl { get; set; } public string ResourceUrl { get; set; } public string Uri { get; set; } public List<string> Urls { get; set; } } public class ReleaseArtist { public string Join { get; set; } public string Name { get; set; } public string Anv { get; set; } public string Tracks { get; set; } public string Role { get; set; } public string ResourceUrl { get; set; } public int Id { get; set; } }

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  • Designing an API on top with Java RMI and Rest APIs

    - by user1303881
    I'm working on the backend of a java web application. We have a document repository (Fedora Commons specifically) where we house xml files. I want to abstract the API of the repository internally so that we aren't tightly coupled to one product. I'd also like to give the flexibility of connecting to to a repository via Java RMI or REST APIs. I was hoping to get advice or resources on how to implement something like this. My thought it that I'd have some abstract repository class that had methods like getRecord, updateRecord, and deleteRecord. In the constructor I would pass the URI for the repository and the API method and port. This would allow some flexibility in the future so that if the REST api became more practical, but allow the flexibility or using RMI which could (should?) have better performance. Am I over thinking this or am I on the right path?

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  • DDD and validation of aggregate root

    - by Mik378
    Suppose an aggregate root : MailConfiguration (wrapping an AddressPart object). The AddressPart object is a simple immutable value object with some fields like senderAdress, recipentAddress (to make example simple). As being an invariant object, AddressPart should logically wrap its own Validator (by the way of external a kind of AddressValidator for respecting Single Responsibility Principle) I read some articles that claimed an aggregateRoot must validate its 'children'. However, if we follow this principle, one could create an AddressPart with an uncohesive/invalid state. What are your opinion? Should I move the collaborator AddressValidator(used in constructor so in order to validate immediately the cohesion of an AddressPart) from AddressPart and assign it to aggregateRoot (MailConfiguration) ?

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  • Disqus integration in website.. what is wrong??

    - by Thieme Hennis
    hi, I try to embed a disqus forum in a website I created. I used the exact code and instructions they give on the installation instructions. I just don't get it. Not much on Google either. Is something wrong in the code? Should I change anything? <!DOCTYPE HTML> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <link rel="shortcut icon" href="../favicon.ico"> <title>Little Louie | Hennis &amp; Blaisse Lovers Productions</title> <META NAME="keywords" CONTENT="some,tags"> <link href="../style2.css" rel="stylesheet" type="text/css"> </head> <body> <p><b>Some text</p> <p> <div id="disqus_thread"></div> <script type="text/javascript"> (function() { var dsq = document.createElement('script'); dsq.type = 'text/javascript'; dsq.async = true; dsq.src = 'http://littelouie.disqus.com/embed.js'; (document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0]).appendChild(dsq); })(); </script> <noscript>Please enable JavaScript to view the <a href="http://disqus.com/?ref_noscript=littelouie">comments powered by Disqus.</a></noscript> <a href="http://disqus.com" class="dsq-brlink">blog comments powered by <span class="logo-disqus">Disqus</span></a> </p> <p> <script type="text/javascript"> var disqus_shortname = 'littelouie'; (function () { var s = document.createElement('script'); s.async = true; s.src = 'http://disqus.com/forums/littelouie/count.js'; (document.getElementsByTagName('HEAD')[0] || document.getElementsByTagName('BODY')[0]).appendChild(s); }()); </script> </p> </body> </html>

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  • Mounting of UDF Bluray in Linux Mint 17

    - by user134885
    I am running Linux mint 17 Cinnamon 64 Bit 2.2.13 - 3.13.0-27 Kernal My machine is a Clevo - fitted with a bluray burner I have tried the following line sudo mount -t udf /dev/scd0 /media/bluray /dev/sr0 But to no avail. Can anyone help me with how to initiate / mount a Bluray on my machine? Thank you to anyone who can give me feedback may sanity and get it going - all works well in windows, but nothing in Linux?

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  • What is wrong with Unix/linux

    - by John Smith
    This is a genuine question motivated by Ideal Operating System When I moved from DOS to Linux in the late 90s it was an eye opener for me. Long file names, arbitrarily many extensions etc... Now I look at Linux and Unix and see all sorts of issues. Here are things I see which could be fixed. Too much depends on root, and rootly powers cannot be voluntarily delegated over several users. (I would love to give up my power to manager printers and delegate the job to another account) File permissions are very limited, and there is not much metadata to go with files. The "everything is a file" metaphor is not true, Plan 9 gets it right(er).

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  • Efficient existing rating system for multiplayer?

    - by Nikolay Kuznetsov
    I would like to add a rating for online version of a board game. In this game there are many game rooms each normally having 3-4 people. So I expect that player's rating adjustments (RA) should depends on Rating of opponents in the game room Number of players in game room and final place of a player Person gets rating increase if he plays more games and more frequently If a person leaves a game room (disconnect) before the game ends he should get punished with a high rating decrease I have found two related questions in here Developing an ELO like point system for a multiplayer gaming site Simplest most effective way to rank and measure player skill in a multi-player environment? Please, let me know what would be the most appropriate existing rating model to refer.

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  • Changelog Management

    - by Gnial0id
    I'm currently developing a WinForm application. In order to inform the client about the improvements and corrections made during the last version, I would like to manage and display a changelog. I mostly found existing changelog on website (the term changelog is pretty used) or explanation on how to manage the release numbers, which I don't care. So, these are my questions: How do I manage a changelog (using XML, pure text in the app, etc.) in a desktop application? How do I present it to the user (external website, inside the winform application)?

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  • Are there any concerns with using a static read-only unit of work so that it behaves like a cache?

    - by Rowan Freeman
    Related question: How do I cache data that rarely changes? I'm making an ASP.NET MVC4 application. On every request the security details about the user will need to be checked with the area/controller/action that they are accessing to see if they are allowed to view it. The security information is stored in the database. For example: User Permission UserPermission Action ActionPermission A "Permission" is a token that is applied to an MVC action to indicate that the token is required in order to access the action. Once a user is given the permission (via the UserPermission table) then they have the token and can therefore access the action. I've been looking in to how to cache this data (since it rarely changes) so that I'm only querying in-memory data and not hitting a database (which is a considerable performance hit at the moment). I've tried storing things in lists, using a caching provider but I either run in to problems or performance doesn't improve. One problem that I constantly run in to is that I'm using lazy loading and dynamic proxies with EntityFramework. This means that even if I ToList() everything and store them somewhere static, the relationships are never populated. For example, User.Permissions is an ICollection but it's always null. I don't want to Include() everything because I'm trying to keep things simple and generic (and easy to modify). One thing I know is that an EntityFramework DbContext is a unit of work that acts with 1st-level caching. That is, for the duration of the unit of work, everything that is accessed is cached in memory. I want to create a read-only DbContext that will exist indefinitely and will only be used to read about permission data. Upon testing this it worked perfectly; my page load times went from 200ms+ to 20ms. I can easily force the data to refresh at certain intervals or simply leave it to refresh when the application pool is recycled. Basically it will behave like a cache. Note that the rest of the application will interact with other contexts that exist per request as normal. Is there any disadvantage to this approach? Could I be doing something different?

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  • Where to start learning OpenGL with C++?

    - by NERDcustard
    I'm 16 years old and my name is Norbert. I have learnt C++ and made some cool text based games and such but I would love to start graphic's programming. I'm a decent artiest (I will have some of my work bellow) I know the base of C++ but I really would like to get into OpenGL. I need someone to show me some good tutorials for OpenGl with C++ so I can really get into game dev. My goal is to be able to program a simple 2d game by the end of the year and I have lots of time to do so. I'm en-rolled in a game dev next year and really need some help with starting off. http://imgur.com/QZjKX http://imgur.com/3CZy7

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  • Keep user and user profile in different tables?

    - by Andrey
    I have seen in a couple of projects that developers prefer to keep essential user info in one table (email/login, password hash, screen name) and rest of the non essential user profile in another (creation date, country, etc). By non-essential I mean that this data is needed only occasionally. Obvious benefit is that if you are using ORM querying less fields is obviously good. But then you can have two entities mapped to same table and this will save you from querying stuff you don't need (while being more convenient). Does anybody know any other advantage of keeping these things in two tables?

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  • Speaking this week at Richmond SQL Server User Group

    - by drsql
    Thursday night, at 6:00 (or so) I will be speaking in Richmond ( http://richmondsql.org/cs2007/ ), talking about How to Implement a Hierarchy using SQL Server. The abstract is: One of the most common structures you will come across in the real world is a hierarchy (either a single parent "tree" or a multi-parent "graph"). Many systems will implement the obvious examples, such as a corporate managerial structure or a bill of materials. It turns out that almost any many-to-many relationship can be...(read more)

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