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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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  • In MVC , DAO should be called from Controller or Model

    - by tito
    I have seen various arguments against the DAO being called from the Controller class directly and also the DAO from the Model class.Infact I personally feel that if we are following the MVC pattern , the controller should not coupled with the DAO , but the Model class should invoke the DAO from within and controller should invoke the model class.Why because , we can decouple the model class apart from a webapplication and expose the functionalities for various ways like for a REST service to use our model class. If we write the DAO invocation in the controller , it would not be possible for a REST service to reuse the functionality right ? I have summarized both the approaches below. Approach #1 public class CustomerController extends HttpServlet { proctected void doPost(....) { Customer customer = new Customer("xxxxx","23",1); new CustomerDAO().save(customer); } } Approach #2 public class CustomerController extends HttpServlet { proctected void doPost(....) { Customer customer = new Customer("xxxxx","23",1); customer.save(customer); } } public class Customer { ........... private void save(Customer customer){ new CustomerDAO().save(customer); } } Note- Here is what a definition of Model is : Model: The model manages the behavior and data of the application domain, responds to requests for information about its state (usually from the view), and responds to instructions to change state (usually from the controller). In event-driven systems, the model notifies observers (usually views) when the information changes so that they can react. I would need an expert opinion on this because I find many using #1 or #2 , So which one is it ?

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  • Of which bad practice is require calling functions in order a sign?

    - by stijn
    Sometimes I find myself writing comments on class methods like this: class A : public Base { public: /** * Sets variable; * should be called before ImplementsInterfaceMtehod(), * else has no effect. */ void SetSomeVariable( var_type value ); virtual void ImplementsInterfaceMethod(); } The callers of Base::ImplementsInterfaceMethod obviously do not know about the variable, and should not. But the users of A should set the variable if they want it to take effect. It is not required to set the variable (else it could be a parameter for the constructor), so I cannot throw exceptions in ImplementsInterfaceMethod if it is not set. Is this a sign of some typical bad practice? Is there a better way than writing a comment as shown to deal with this?

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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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  • When would you want two references to the same object?

    - by HCBPshenanigans
    In Java specifically, but likely in other languages as well; When would it be useful to have two references to the same object? Example: Dog a = new Dog(); Dob b = a; Is there a situation where this would be useful? Why would this be a preferred solution to using a whenever you want to interact with the object represented by a? Edit: Can I just say that all of your dog related examples are Delightful!

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  • Object oriented EDI handling in PHP

    - by Robert van der Linde
    I'm currently starting a new sub project where I will: Retrieve the order information from our mainframe Save the order information to our web-apps' database Send the order as EDI (either D01b or D93a) Receive the order response, despatch advice and invoice messages Do all kinds of fun things with the resulting datasets. However I am struggling with my initial class designs. The order information will be retrieved from the mainframe which will result in a "AOrder" class, this isn't a problem, I am not sure about how to mold this local object into an EDI string. Should I create EDIOrder/EDIOrderResponse/etc classes with matching decorators (EDIOrderD01BDecorator, EDIOrderD93ADecorator)? Do I need builder objects or can I do: // $myOrder is instance of AOrder $myOrder->toEDIOrder(); $decorator = new EDIOrderD01BDecorator($myOrder); $edi = $decorator->getEDIString(); And it'll have to work the other way around as well. Is the following code a good way of handling this problem or should I go about this differently? $ediString = $myEDIMessageBroker->fetch(); $ediOrderResponse = EDIOrderResponse::fromString($ediString); I'm just not so sure about how I should go about designing the classes and interactions between them. Thanks for reading and helping.

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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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  • Random/Procedural vs. Previously Made Level Generation

    - by PythonInProgress
    I am making a game (called "Glory") that is a top-down explorer game, and am wondering what the advantages/disadvantages of using random/procedural generation vs. pre-made levels are. There seems to be few that i can think of, other than the fact that items may be a problem to distribute in randomly generated terrain, and that the generated terrain may look weird. The downside to previously made levels is that I would need to make a level editor, though. I cannot decide what is better to use.

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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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  • Should I limit my type name suffix vocabulary when using OOP?

    - by Den
    My co-workers tend to think that it is better to limit non-domain type suffixes to a small fixed set of OOP-pattern inspired words, e.g.: *Service *Repository *Factory *Manager *Provider I believe there is no reason to not extend that set with more names, e.g. (some "translation" to the previous vocabulary is given in brackets): *Distributor (= *DistributionManager or *SendingService) *Generator *Browser (= *ReadonlyRepositoryService) *Processor *Manipulator (= *StateMachineManager) *Enricher (= *EnrichmentService) (*) denotes some domain word, e.g. "Order", "Student", "Item" etc. The domain is probably not complex enough to use specialized approaches such as DDD which could drive the naming.

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  • Which is a better practice - helper methods as instance or static?

    - by Ilian Pinzon
    This question is subjective but I was just curious how most programmers approach this. The sample below is in pseudo-C# but this should apply to Java, C++, and other OOP languages as well. Anyway, when writing helper methods in my classes, I tend to declare them as static and just pass the fields if the helper method needs them. For example, given the code below, I prefer to use Method Call #2. class Foo { Bar _bar; public void DoSomethingWithBar() { // Method Call #1. DoSomethingWithBarImpl(); // Method Call #2. DoSomethingWithBarImpl(_bar); } private void DoSomethingWithBarImpl() { _bar.DoSomething(); } private static void DoSomethingWithBarImpl(Bar bar) { bar.DoSomething(); } } My reason for doing this is that it makes it clear (to my eyes at least) that the helper method has a possible side-effect on other objects - even without reading its implementation. I find that I can quickly grok methods that use this practice and thus help me in debugging things. Which do you prefer to do in your own code and what are your reasons for doing so?

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  • Code Smell: Inheritance Abuse

    - by dsimcha
    It's been generally accepted in the OO community that one should "favor composition over inheritance". On the other hand, inheritance does provide both polymorphism and a straightforward, terse way of delegating everything to a base class unless explicitly overridden and is therefore extremely convenient and useful. Delegation can often (though not always) be verbose and brittle. The most obvious and IMHO surest sign of inheritance abuse is violation of the Liskov Substitution Principle. What are some other signs that inheritance is The Wrong Tool for the Job even if it seems convenient?

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  • How can you predict the time it will take for two processes in two different machines in a cluster to communicate?

    - by Dokkat
    I am trying to develop a computing application which needs a lot of memory (500gb). Buying a single machine for that is overly expensive. I can, though, buy ~100 small instances on Digital Ocean or similar, divide the memory in blocks and use TCP to emulate shared memory between the instances. Now, my question is: how can I measure/predict the time it will take for two processes in two different machines like that to share information, in comparison to IPC and shared memory? Are there rules of thumb? I don't want exact values, but knowing more or less how much faster one is would be very helpful in visualising the feasibility of this approach.

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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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  • Is this an acceptable approach to undo/redo in Python?

    - by Codemonkey
    I'm making an application (wxPython) to process some data from Excel documents. I want the user to be able to undo and redo actions, even gigantic actions like processing the contents of 10 000 cells simultaneously. I Googled the topic, and all the solutions I could find involves a lot of black magic or is overly complicated. Here is how I imagine my simple undo/redo scheme. I write two classes - one called ActionStack and an abstract one called Action. Every "undoable" operation must be a subclass of Action and define the methods do and undo. The Action subclass is passed the instance of the "document", or data model, and is responsible for committing the operation and remembering how to undo the change. Now, every document is associated with an instance of the ActionStack. The ActionStack maintains a stack of actions (surprise!). Every time actions are undone and new actions are performed, all undone actions are removed for ever. The ActionStack will also automatically remove the oldest Action when the stack reaches the configurable maximum amount. I imagine the workflow would produce code looking something like this: class TableDocument(object): def __init__(self, table): self.table = table self.action_stack = ActionStack(history_limit=50) # ... def delete_cells(self, cells): self.action_stack.push( DeleteAction(self, cells) ) def add_column(self, index, name=''): self.action_stack.push( AddColumnAction(self, index, name) ) # ... def undo(self, count=1): self.action_stack.undo(count) def redo(self, count=1): self.action_stack.redo(count) Given that none of the methods I've found are this simple, I thought I'd get the experts' opinion before I go ahead with this plan. More specifically, what I'm wondering about is - are there any glaring holes in this plan that I'm not seeing?

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  • Presenting Loading Data Warehouse Partitions with SSIS 2012 at SQL Saturday DC!

    - by andyleonard
    Join Darryll Petrancuri and me as we present Loading Data Warehouse Partitions with SSIS 2012 Saturday 8 Dec 2012 at SQL Saturday 173 in DC ! SQL Server 2012 table partitions offer powerful Big Data solutions to the Data Warehouse ETL Developer. In this presentation, Darryll Petrancuri and Andy Leonard demonstrate one approach to loading partitioned tables and managing the partitions using SSIS 2012, and reporting partition metrics using SSRS 2012. Objectives A practical solution for loading Big...(read more)

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  • Service Layer - how broad should it be, and should it be used also on the local application?

    - by BornToCode
    Background: I need to build a main application with some operations (CRUD and more) (-in winforms), I need to make another application which will re-use some of the functions of the main application (-in webforms). I understood that using service layer is the best approach here. If I understood correctly the service should be calling the function on the BL layer (correct me if I'm wrong) The dilemma: In my main winform UI - should I call the functions from the BL, or from the service? (please explain why) Should I create a service for every single function on the BL even if I need some of the functions only in one UI? for example - should I create services for all the CRUD operations, even though I need to re-use only update operation in the webform? YOUR HELP IS MUCH APPRECIATED

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  • Write own messaging system vs. utilize existing ones

    - by A.Rashad
    We are trying to have our own startup, with a middleware application to glue small applications with enterprise legacy systems. for such middle-ware to function properly, we will need some sort of messaging system to make different components talk to each other in a reliable way. the alternatives are: use an existing messaging system, such as 0MQ, jBOSS, WebSphere MQ, etc. build our own messaging system the way we see the problem I am more biased towards the later option for the following reasons: to have more control over our final product to avoid any licensing problems later on to learn about messaging while writing the code to invent something new, that might cost us lots of $$$ if reused an existing system What would you do if in my shoes?

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  • What browser do you build in? [closed]

    - by Ryan
    Lately I have been using Chrome, but I am starting to think I should use FF. What are the advantages and disadvantages of the various mainstream browsers (with an emphasis on Chrome and FF) when doing web development? Is it easier to start with clean code for a relatively conforming browser, and later add hacks/workarounds for acceptable display with less conforming browsers, or is it easier to work with a variety of browsers from the beginning, so we never have a page that's completely unacceptable with, for example, IE 6?

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  • How is intermediate data organized in MapReduce?

    - by Pedro Cattori
    From what I understand, each mapper outputs an intermediate file. The intermediate data (data contained in each intermediate file) is then sorted by key. Then, a reducer is assigned a key by the master. The reducer reads from the intermediate file containing the key and then calls reduce using the data it has read. But in detail, how is the intermediate data organized? Can a data corresponding to a key be held in multiple intermediate files? What happens when there is too much data corresponding to one key to be held by a single file? In short, how do intermediate partitions differ from intermediate files and how are these differences dealt with in the implementation?

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  • Single or multiple return statements in a function [on hold]

    - by Juan Carlos Coto
    When writing a function that can have several different return values, particularly when different branches of code return different values, what is the cleanest or sanest way of returning? Please note the following are really contrived examples meant only to illustrate different styles. Example 1: Single return def my_function(): if some_condition: return_value = 1 elif another_condition: return_value = 2 else: return_value = 3 return return_value Example 2: Multiple returns def my_function(): if some_condition: return 1 elif another_condition: return 2 else: return 3 The second example seems simpler and is perhaps more readable. The first one, however, might describe the overall logic a bit better (the conditions affect the assignment of the value, not whether it's returned or not). Is the second way preferable to the first? Why?

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  • Should I incorporate exit cost into choosing a solution

    - by Mr Happy
    I'm currently choosing between two viable software designs/solutions. Solution 1 is easy to implement, but will lock some data in a propriaty format, and will be hard to change later. Solution 2 is hard to implement, but will be a lot easier to change later on. Should I go YAGNI on this or should I incorporate the exit cost in the decision making? Or asked differently, is the exit cost part of the TCO? I'm thinking of going back to the customer with this to ask wether or not he thinks the exit costs are relevant, but I'd like to know what the community thinks first. P.S. Is exit cost the correct term?

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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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  • which style of member-access is preferable

    - by itwasntpete
    the purpose of oop using classes is to encapsulate members from the outer space. i always read that accessing members should be done by methods. for example: template<typename T> class foo_1 { T state_; public: // following below }; the most common doing that by my professor was to have a get and set method. // variant 1 T const& getState() { return state_; } void setState(T const& v) { state_ = v; } or like this: // variant 2 // in my opinion it is easier to read T const& state() { return state_; } void state(T const& v) { state_ = v; } assume the state_ is a variable, which is checked periodically and there is no need to ensure the value (state) is consistent. Is there any disadvantage of accessing the state by reference? for example: // variant 3 // do it by reference T& state() { return state_; } or even directly, if I declare the variable as public. template<typename T> class foo { public: // variant 4 T state; }; In variant 4 I could even ensure consistence by using c++11 atomic. So my question is, which one should I prefer?, Is there any coding standard which would decline one of these pattern? for some code see here

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  • Pattern for performing game actions

    - by Arkiliknam
    Is there a generally accepted pattern for performing various actions within a game? A way a player can perform actions and also that an AI might perform actions, such as move, attack, self-destruct, etc. I currently have an abstract BaseAction which uses .NET generics to specify the different objects that get returned by the various actions. This is all implemented in a pattern similar to the Command, where each action is responsible for itself and does all that it needs. My reasoning for being abstract is so that I may have a single ActionHandler, and AI can just queue up different action implementing the baseAction. And the reason it is generic is so that the different actions can return result information relevant to the action (as different actions can have totally different outcomes in the game), along with some common beforeAction and afterAction implementations. So... is there a more accepted way of doing this, or does this sound alright?

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