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• Strategy for clients to retrieve real-time log from HTTP server

  - by Jerry Dodge

  I have an HTTP Server Service application which has its own logging mechanism. It's written in Delphi. I would like to provide a way for multiple clients to connect to this service and get a real-time update of the log. The log in the service moves rather fast, there's a lot of things to log. There may be up to 50 messages within 1 second at times. The existing log which is already implemented is not saved, it's only kept in the memory of the server service - where I will need to distribute it to any client which needs it. Once all clients have a log message, it should be deleted. I intend to use HTTP to "ask" the server for the log, and respond with an XML packet. The connections are not keep-alive. The only problem is, the server should only send the client those log records which it needs, not everything. I have no way of the server pushing the log to the clients in real-time, so each client needs to repeatedly ask the server for the latest log records. This HTTP Server is very lightweight, and there is no session management. There isn't even any type of authentication. The only way I see is for a client to register its self on the server, and whenever a log is issued on the server, it creates a copy of the log for each client, where each client has a log queue (string list). However, suppose there are 100 clients connected and expecting to receive this log. That means the server must create 100 copies of each log, add this log to the end of each client log queue, and wait for the client to request it. At that point, when the server replies with the XML log, it should flush (delete) whatever's in the queue. I'm worried however that this could cause memory issues. Each client log queue might get 100 log messages before the client requests the latest logs. How should I go about doing this in the fastest way possible without hindering the performance of the server? I'm trying to avoid having to create a copy of each log for each client.

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• Why does it take so long to finalize the HTML 5 spec?

  - by EpsilonVector

  I was reading this and one sentence caught my eye (emphasis mine): So Ian Hickson, XHTML’s biggest critic, fathered HTML 5, an action-oriented toddler specification that won’t reach adulthood until 2022, although some of it can be used today. Is that true? Is that really the HTML 5 development cycle? Why is it taking so long? What makes it so difficult to get right that it won't be final until 11 years from now?

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• To implement registration page with Vaadin or not?

  - by JVerstry

  This is a tactical implementation question about usage of Vaadin or in some part of my application. Vaadin is a great framework to login users and implement sophisticated web applications with many pages. However, I think it is not very well suited to desgin pages to register new users for my application. Am I right? Am I am wrong? It seems to me that a simple HTML/CSS/Javascript login + email registration + confirmation email with confirmation link cannot be implemented easily with Vaadin. It seems like Vaadin would be overkill. Do you agree? Or am I missing something? I am looking for feedback from experienced Vaadin users.

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• What happens at control invoke function?

  - by user65909

  A question about form controls invoke function. Control1 is created on thread1. If you want to update something in Control1 from thread2 you must do something like: delegate void SetTextCallback(string txt); void setText(string txt) { if (this.textBox1.InvokeRequired) { SetTextCallback d = new SetTextCallback(setText); this.Invoke(d, new object[] { txt }); } else { // this will run on thread1 even when called from thread2 this.textBox1.AppendText(msg); } }` What happens behind the scenes here? This invoke behaves different from a normal object invoke. When you want to call a function in an object on a specific thread, then that thread must be waiting on some queue of delegates, and execute the incoming delegates. Is it correct that the windows forms control invoke function is completely different from the standard object invoke function?

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• How do I handle priority and propagation in an event system?

  - by Peeter

  Lets say I have a simple event system with the following syntax: object = new Object(); object.bind("my_trigger", function() { print "hello"; }); object.bind("my_trigger", function() { print "hello2"; }); object.trigger("my_trigger"); How could I make sure hello2 is printed out first (I do not want my code to depend on which order the events are binded). Ontop of that, how would I prevent my events from propagating (e.g. I want to stop every other event from being executed)

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• Do you think code is self documenting?

  - by Desolate Planet

  This is a question that was put to me many years ago as a gradute in a job interview and it's kind of picked at my brain now and again and I've never really found a good answer that satisfies me. The interviewer in question was looking for a black and white answer, there was no middle ground. I never got the chance to ask about the rationale behind the question, but I'm curious why that question would be put to a developer and what you would learn from a yes or no answer? From my own point of view, I can read Java, Python, Delphi etc, but if my manager comes up to me and asks me how far along in a project I am and I say "The code is 80% complete" (and before you start shooting me down, I've heard this uttered in a couple of offices by developers), how exactly is that self documenting? Apologies if this question seems strange, but I'd rather ask and get some opinions on it to gain a better understanding of why it would be put to someone in an interview.

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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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• Why not have a High Level Language based OS? Are Low Level Languages more efficient?

  - by rtindru

  Without being presumptuous, I would like you to consider the possibility of this. Most OS today are based on pretty low level languages (mainly C/C++) Even the new ones such as Android uses JNI & underlying implementation is in C In fact, (this is a personal observation) many programs written in C run a lot faster than their high level counterparts (eg: Transmission (a bittorrent client on Ubuntu) is a whole lot faster than Vuze(Java) or Deluge(Python)). Even python compilers are written in C, although PyPy is an exception. So is there a particular reason for this? Why is it that all our so called "High Level Languages" with the great "OOP" concepts can't be used in making a solid OS? So I have 2 questions basically. Why are applications written in low level languages more efficient than their HLL counterparts? Do low level languages perform better for the simple reason that they are low level and are translated to machine code easier? Why do we not have a full fledged OS based entirely on a High Level Language?

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• How can test users access an unpublished iOS app?

  - by David

  I am considering outsourcing the development of an iOS app to various independent developers. I will have have various testers of the app. We all work for separate companies. Some of these testers will be customers, who I would like feedback from. As there are multiple developers involved I expect there to be a new release on a daily basis. How can this be done? Would each of the testers need to buy some sort of license to avoid having to go through the app approval process? Is there any smooth way to do this so that it will not be a hassle for our friendly customers, who are willing to test our app?

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• Logging errors caused by exceptions deep in the application

  - by Kaleb Pederson

  What are best-practices for logging deep within an application's source? Is it bad practice to have multiple event log entries for a single error? For example, let's say that I have an ETL system whose transform step involves: a transformer, pipeline, processing algorithm, and processing engine. In brief, the transformer takes in an input file, parses out records, and sends the records through the pipeline. The pipeline aggregates the results of the processing algorithm (which could do serial or parallel processing). The processing algorithm sends each record through one or more processing engines. So, I have at least four levels: Transformer - Pipeline - Algorithm - Engine. My code might then look something like the following: class Transformer { void Process(InputSource input) { try { var inRecords = _parser.Parse(input.Stream); var outRecords = _pipeline.Transform(inRecords); } catch (Exception ex) { var inner = new ProcessException(input, ex); _logger.Error("Unable to parse source " + input.Name, inner); throw inner; } } } class Pipeline { IEnumerable<Result> Transform(IEnumerable<Record> records) { // NOTE: no try/catch as I have no useful information to provide // at this point in the process var results = _algorithm.Process(records); // examine and do useful things with results return results; } } class Algorithm { IEnumerable<Result> Process(IEnumerable<Record> records) { var results = new List<Result>(); foreach (var engine in Engines) { foreach (var record in records) { try { engine.Process(record); } catch (Exception ex) { var inner = new EngineProcessingException(engine, record, ex); _logger.Error("Engine {0} unable to parse record {1}", engine, record); throw inner; } } } } } class Engine { Result Process(Record record) { for (int i=0; i<record.SubRecords.Count; ++i) { try { Validate(record.subRecords[i]); } catch (Exception ex) { var inner = new RecordValidationException(record, i, ex); _logger.Error( "Validation of subrecord {0} failed for record {1}", i, record ); } } } } There's a few important things to notice: A single error at the deepest level causes three log entries (ugly? DOS?) Thrown exceptions contain all important and useful information Logging only happens when failure to do so would cause loss of useful information at a lower level. Thoughts and concerns: I don't like having so many log entries for each error I don't want to lose important, useful data; the exceptions contain all the important but the stacktrace is typically the only thing displayed besides the message. I can log at different levels (e.g., warning, informational) The higher level classes should be completely unaware of the structure of the lower-level exceptions (which may change as the different implementations are replaced). The information available at higher levels should not be passed to the lower levels. So, to restate the main questions: What are best-practices for logging deep within an application's source? Is it bad practice to have multiple event log entries for a single error?

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• About insertion sort and especially why it's said that copy is much faster than swap?

  - by Software Engeneering Learner

  From Lafore's "Data Structures and Algorithms in Java": (about insertion sort (which uses copy + shift instead of swap (used in bubble and selection sort))) However, a copy isn’t as time-consuming as a swap, so for random data this algo- rithm runs twice as fast as the bubble sort and faster than the selectionsort. Also author doesn't mention how time consuming shift is. From my POV copy is the simplest pointer assignment operation. While swap is 3x pointer assignment operations. Which doesn't take much time. Also shift of N elemtns is Nx pointer assignment operations. Please correct me if I'm wrong. Please explain, why what author says is true? I don't understand.

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• OpenGL programming vs Blender Software, which is better for custom video creation?

  - by iammilind

  I am learning OpenGL API bit by bit and also develop my own C++ framework library for effectively using them. Recently came across Blender software which is used for graphics creation and is in turn written in OpenGL itself. For my part time hobby of graphics learning, I want to just create small-small movie or video segments; e.g. related to construction engineering, epic stories and so on. There may be very minimal to nil mouse-keyboard interaction for those videos, unlike video games which are highly interactive. I was wondering if learning OpenGL from scratch is worth for it or should I invest my time in learning Blender software? There are quite a few good movie examples are created using Blender and are shown in its website. Other such opensource cross platform alternatives are also welcome, which can serve my aforementioned purpose.

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• How to present a stable data model in a public API that allows internal data structures to be changed without breaking the public view of the data?

  - by Max Palmer

  I am in the process of developing an application that allows users to write C# scripts. These scripts allow users to call selected methods and to access and manipulate data in a document. This works well, however, in the development version, scripts access the document's (internal) data structures directly. This means that if we were to change the internal data model/structure, there is a good chance that someone's script will no longer compile. We obviously want to prevent this breaking change from happening, but still want to allow the user to write sensible C# code (whilst not restricting how we develop our internal data model as a result). We therefore need to decouple our scripting API and its data structures from our internal methods and data structures. We've a few ideas as to how we might allow the user to access a what is effectively a stable public version of the document's internal data*, but I wanted to throw the question out there to someone who might have some real experience of this problem. NB our internal document's data structure is quite complex and it could be quite difficult to wrap. We know we want to expose as little as possible in our public API, especially as once it's out there, it's out there for good. Can anyone help? How do scripting languages / APIs decouple their public API and data structures from their internal data structures? Is there no real alternative to having to write a complex interaction layer? If we need to do this, what's a good approach or pattern for wrapping complex data structures that include nested objects, including collections? I've looked at the API facade pattern, which looks like it's trying to address these kinds of issues, but are there alternatives? *One idea is to build a data facade that is kept stable across versions of our application. The facade exposes a set of facade data objects that are used in the script code. These maintain backwards compatibility and wrap access to our internal document's data model.

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• blurry lines between web application context layer, service layer and data access layer in spring

  - by thenaglecode

  I Originally asked this question in SO but on advice I have moved the question here... I'll admit I'm a spring newbie, but you can correct me if I'm wrong, this one liner looks kinda fishy in a best practices sort of way: @RepositoryRestResource(collectionResourceRel="people"...) public interface PersonRepository extends PagingAndSortingRepository<Person, Long> For those who are unaware, the following does many things: It is an interface definition that can be registered in an application context as a jpa repository, automagically hooking up all the default CRUD operations within a persistence context (that is externally configured). and also configures default controller/request-mapping/handler functionality at the namespace "/people" relative to your configured dispatcher servlet-mapping. Here's my point. I just crossed 3 conceptual layers with one line of code! this feels against my seperation-of-concern instincts but i wanted to hear your opinion. And for the sake of being on a question and answer site, I would like to know whether there is a better way of seperating these different layers - Service, Data, Controllers - whilst maintaining as minimal configuration as possible

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• REST - Tradeoffs between content negotiation via Accept header versus extensions

  - by Brandon Linton

  I'm working through designing a RESTful API. We know we want to return JSON and XML for any given resource. I had been thinking we would do something like this: GET /api/something?param1=value1 Accept: application/xml (or application/json) However, someone tossed out using extensions for this, like so: GET /api/something.xml?parm1=value1 (or /api/something.json?param1=value1) What are the tradeoffs with these approaches? Is it best to rely on the accept header when an extension isn't specified, but honor extensions when specified? Is there a drawback to that approach?

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• Why isn't Stripes popular, even though it's an awesome web framework?

  - by Mr.Chowdary

  I'm new to Stripes. I worked on MVC frameworks like Struts 1.x and 2.x. When I started learning, its features are awesome and very lightweight; it has in-depth validations and offers easy integration with other frameworks too. There are no configurations and everything is simplified with annotations. I don't understand why Stripes is not popular compared with other Java web frameworks like Struts or JSF? I didn't find any drawbacks in Stripes. Any ideas why?

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• How not to suffer from ideologists when you're a pragmatic person?

  - by Lukas Eder

  My story: I'm a pragmatic person. Sometimes, the most simple solution to a problem to get the job done is the one that fits best for me, if its not an utter blasphemy and reproach to any design principles. Check out my answer to this question on stackoverflow. Simple. Works. Was accepted. Could be improved. Is clearly not perfect. And along comes this guy. He downvotes me, comments on the question how his answer is better, more accurate etc and calls me "plain wrong". Reminds me of this comic strip. :-) While on stackoverflow I can laugh at these things because those people are far away, in the real world I'm suffering from ideologies every now and then. Heck, I'm not creating a miracle piece of software, I need to keep that huge legacy thing running, and it's an adventure to me every day. I don't have the time or passion to beautify my code (or other people's code) to that extent. My question(s): How do you deal with ideologies / ideologists, when you're a pragmatic person? How do you deal with pragmatism / pragmatists, when you're an ideologic person? I'm interested in both point of views. Tell me your experience. But please, be fair, somewhat objective, and understand that you may NOT be entirely correct and your opinion is NOT the only true one... :-)

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• mocha testing for the lazies, single key-press for all possible tests

  - by laggingreflex

  I have a batch file that lists all the test files I have and asks me which test I want to perform, like Test. [U]nit, [I]ntegration : i (user input) Integration. [A]ll, [2][U]serInteraction, [3][R]esultGeneration : u 2 User Interaction. Running "mocha integration\2userint.js" ... So essentially I have configured a batch "option" for each test file I have, which I can choose to run individually or all together. But adding and removing tests is a pain. Is there something that does this or anything like this automatically? Like reads all the files and asks me which file(s) I want to test. A GUI with checkboxes would be ultimate! but I'll take anything. I'm working in node.js

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• What is a good support knowledge base tool?

  - by Guillaume

  I have been searching for a tool to help my team organize its knowledge for resolving recurring support cases. I know this question will probably be closed, but I'll try my change anyway because I know that I can have some good answers about that. Context: our team is developing and supporting an huge applications (lots of different screens and workflow processes. We already have a good tool for managing our documentation, but we are struggling with support cases. Support action involve often quite a lot of manual steps to fix stuff and the knowledge for these actions is more 'oral transmission' than modern tools. We need an efficient way to store them in a knowledge base to be able to retrieve similar cases based on patterns (a stacktrace, an error message, a component name, a workflow step, ...) and ranked by similarity. Our wiki search is not very powerful when it come to this kind of search and the team members don't want to 'waste' time writing a report that will never be found... Do you know efficient knowledge base tool for this kind of use case ?

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• what is the Web development process efficiency judgment criteria

  - by Ahmed safan

  I'm working as a web developer and I want to be able to determine if I'm efficient. Does this include the how long it take to accomplish tasks such as: Server side code for the site logic with one language or multiple php,asp,asp.net. Client side code like javascript with jquery for ajax, menus and other interactivity Page layout, html, css (color, fonts (but I have no artistic sense!)) The needs of the site and how it will work (planning) How can i judge how long it will take to complete a website? The site has CMS for adding and editing news, products, articles on the experience of the company. Also, they can edit team work, add Recreational Activities and a logo gallery with compressed psd download, and send messages to cpanel and to email. You are starting from scratch except JQuery and PHPmailer. How can I estimate how long the job will take, and how can I calculate the required time to finish any new projects? I'm so sorry for many scattered questions, but I'm in my first experiment and I want to take benefits from the great experience of those who have it.

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• Building general programming skills?

  - by toleero

  Hello :) I currently am quite new to programming, I've had exposure to a few languages (C#, PHP, JavaScript, VB, and some others) and I'm quite new to OOP. I was just wondering what is the best way to build up general programming/problem solving skills without being language specific? I was thinking maybe of something like Project Euler but more geared towards newbies? Thanks! Edit: I am looking at getting into Game Scripting/Programming, I'm already in Games but in a different discipline :)

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• C# or .Net features to cut off assuming no backward compatibility needed?

  - by Gulshan

  Any product or framework evolves. Mainly it's done to catch up the needs of it's users, leverage new computing powers and simply make it better. Sometimes the primary design goal also changes with the product. C# or .net framework is no exception. As we see, the present day 4th version is very much different comparing with the first one. But thing comes as a barricade to this evolution- backward compatibility. In most of frameworks/products there are features would have been cut off if there was no need to support backward compatibility. According to you, what are these features in C#/.net? Please mention one feature per answer.

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• PHP ORM style of querying

  - by Petah

  Ok so I have made an ORM library for PHP. It uses syntax like so: *(assume that $business_locations is an array)* Business::type(Business:TYPE_AUTOMOTIVE)-> size(Business::SIZE_SMALL)-> left_join(BusinessOwner::table(), BusinessOwner::business_id(), SQL::OP_EQUALS, Business::id())-> left_join(Owner::table(), SQL::OP_EQUALS, Owner::id(), BusinessOwner::owner_id())-> where(Business::location_id(), SQL::in($business_locations))-> group_by(Business::id())-> select(SQL::count(BusinessOwner::id()); Which can also be represented as: $query = new Business(); $query->set_type(Business:TYPE_AUTOMOTIVE); $query->set_size(Business::SIZE_SMALL); $query->left_join(BusinessOwner::table(), BusinessOwner::business_id(), SQL::OP_EQUALS, $query->id()); $query->left_join(Owner::table(), SQL::OP_EQUALS, Owner::id(), BusinessOwner::owner_id()); $query->where(Business::location_id(), SQL::in($business_locations)); $query->group_by(Business::id()); $query->select(SQL::count(BusinessOwner::id()); This would produce a query like: SELECT COUNT(`business_owners`.`id`) FROM `businesses` LEFT JOIN `business_owners` ON `business_owners`.`business_id` = `businesses`.`id` LEFT JOIN `owners` ON `owners`.`id` = `business_owners`.`owner_id` WHERE `businesses`.`type` = 'automotive' AND `businesses`.`size` = 'small' AND `businesses`.`location_id` IN ( 1, 2, 3, 4 ) GROUP BY `businesses`.`id` Please keep in mind that the syntax might not be prefectly correct (I only wrote this off the top of my head) Any way, what do you think of this style of querying? Is the first method or second better/clearer/cleaner/etc? What would you do to improve it?

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• Is there a programming language with not a tree but tags idea behind OOP?

  - by kolupaev

  I'm thinking about tree structures, and I feel that I don't like them. It's like when you have a shop, then you try to put all products to tree-like catalog, and then you need to place one product to multiple categories, now you have multiple routing, bla-bla. I don't feel like everything in the world could be put to a tree. Instead, I like idea of tags. I would like to store everything with tags. With tags I could do much more. I can even simulate trees if I want. I want to have tag-based filesystem! But hey - modern OOP paradigm with inheritance is based on tree. I want to see how it is when you don't have such basement. Closest thing I found is mixins in some languages. Do you know what else is also about this ideas?

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• What are some recommended video lectures for a non-CS student to prepare for the GRE CS subject test?

  - by aristos

  Well the title kinda explains all there is to explain. I'm a non-cs student and was preparing to apply PhD programs in applied mathematics. But for my senior thesis I've been reading lots of machine learning and pattern recognition literature and enjoying it a lot. I've taken lots of courses with statistics and stochastics content, which I think, would help me if I get accepted to a program with ML focus, but there are only two CS courses -introduction to programming- in my transcript and therefore I decided to take the CS subject test to increase my chances. Which courses do you think would be most essential to have a good result from CS subject test? I'm thinking of watching video lectures of them, so do you have any recommendations?

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