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• hosting a high traffic facebook app (game)

  - by z3cko

  we are currently developing a high traffic facebook application. all the traffic will be within one month, where there are 500.000 to 1.000.000 expected users. after that month, the game is over and we have a winner - so the app will be archived. we are currently planning to develop the application with ruby on rails and searching for hosting options that can deal with the traffic. the problem is not so much the users, but the peak values: we will have around 500.000 requests coming daily within a short timeframe (lets say within 3 minutes in the worst case) we are expecting 500.000 to 1.000.000 users of the application, with peaks at 1:00pm (timezone GMT+1), where most (up to 80% of the users) will send most of the requests. the requests are from 11th of june to 11.july - after that, the app/game is closed/over. we are currently developing an aggressive caching mechanism - currently we are thinking about 2 or 3 small apps/webservices, that will handle the load. the load is distributed as follows: a) main application, cached data (11 screens, 200k each) b) voting: every day until 1:00pm (timezone GMT+1) - every user votes with about 10k data sent, high concurrent peak values! questions: is there any specific application setup that is recommendable? are there any hosting partners that can be recommended? thanks!

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• UnauthorizedAccessException when running desktop application from shared folder

  - by Atara

  I created a desktop application using VS 2008. When I run it locally, all works well. I shared my output folder (WITHOUT allowing network users to change my files) and ran my exe from another Vista computer on our intranet. When running the shared exe, I receive "System.UnauthorizedAccessException" when trying to read a file. How can I give permission to allow reading the file? Should I change the code? Should I grant permission to the application\folder on the Vista computer? how? Notes: I do not use ClickOnce. the application should be distributed using xcopy. My application target framework is ".Net Framework 2.0" On the Vista computer, "controlPanel | UninstallOrChangePrograms" it says it has "Microsoft .Net Framework 3.5 SP1" I also tried to map the folder drive, but got the same errors, only now the fileName is "T:\my.ocx" ' ---------------------------------------------------------------------- ' my code: Dim src As String = mcGlobals.cmcFiles.mcGetFileNameOcx() Dim ioStream As New System.IO.FileStream(src, IO.FileMode.Open) ' ---------------------------------------------------------------------- Public Shared Function mcGetFileNameOcx() As String ' ---------------------------------------------------------------------- Dim dirName As String = Application.StartupPath & "\" Dim sFiles() As String = System.IO.Directory.GetFiles(dirName, "*.ocx") Dim i As Integer For i = 0 To UBound(sFiles) Debug.WriteLine(System.IO.Path.GetFullPath(sFiles(i))) ' if found any - return the first: Return System.IO.Path.GetFullPath(sFiles(i)) Next Return "" End Function ' ---------------------------------------------------------------------- ' The Exception I receive: System.UnauthorizedAccessException: Access to the path '\\computerName\sharedFolderName\my.ocx' is denied. at System.IO._Error(Int32 errorCode, String maybeFullPath) at System.IO.FileStream.Init(...) at System.IO.FileStream..ctor(...) at System.IO.FileStream..ctor(String path, FileMode mode) ' ----------------------------------------------------------------------

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• How to implement Administrator rights in Java Application?

  - by Yatendra Goel

  I am developing a Data Modeling Software that is implemented in Java. This application converts the textual data (stored in a database) to graphical form so that users can interpret the data in a more efficient form. Now, this application will be accessed by 3 kinds of persons: 1. Managers (who can fill the database with data and they can also view the visual form of the data after entering the data into the database) 2. Viewers (who can only view the visual form of data that has been filled by managers) 3. Administrators (who can create and manage other administrators, managers and viewers) Now, how to implement 3 diff. views of the same application. Note: Managers, Viewers and Administrators can be located in any part of the world and should access the application through internet. One idea that came in my mind is as follows: Step1: Code all the business logic in EJBs so that it can be used in distributed environment (means which can be accessed by several users through internet) Step2: Code 3 Swing GUI Clients: One for administrators, one for managers and one for viewers. These 3 GUI clients can access business logic written in EJBs. Step3: Distribute the clients corresponding to their users. For instance, manager client to managers. =================================QUESTIONS======================================= Q1. Is the above approach is correct? Q2. This is very common functionality that various softwares have. So, Do they implement this kind of functionality through this way or any other way? Q3. If any other approach would be more better, then what is that approach?

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• Java: fastest way to do random reads on huge disk file(s)

  - by cocotwo

  I've got a moderately big set of data, about 800 MB or so, that is basically some big precomputed table that I need to speed some computation by several orders of magnitude (creating that file took several mutlicores computers days to produce using an optimized and multi-threaded algo... I do really need that file). Now that it has been computed once, that 800MB of data is read only. I cannot hold it in memory. As of now it is one big huge 800MB file but splitting in into smaller files ain't a problem if it can help. I need to read about 32 bits of data here and there in that file a lot of time. I don't know before hand where I'll need to read these data: the reads are uniformly distributed. What would be the fastest way in Java to do my random reads in such a file or files? Ideally I should be doing these reads from several unrelated threads (but I could queue the reads in a single thread if needed). Is Java NIO the way to go? I'm not familiar with 'memory mapped file': I think I don't want to map the 800 MB in memory. All I want is the fastest random reads I can get to access these 800MB of disk-based data. btw in case people wonder this is not at all the same as the question I asked not long ago: http://stackoverflow.com/questions/2346722/java-fast-disk-based-hash-set

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• Mutually beneficial IP/copyright clauses for contract-based freelance work

  - by Nathan de Vries

  I have a copyright section in the contract I give to my clients stating that I retain copyright on any works produced during my work for them as an independent contractor. This is most definitely not intended to place arbitrary restrictions on my clients, but rather to maintain my ability to decide on how the software I create is licensed and distributed. Almost every project I work on results in at least one part of it being released as open source. Every project I work on makes use of third-party software released in the same fashion, so returning the favour is something I would like to continue doing. Unfortunately, the contract is not so clear when it comes to defining the rights of the client in the use of said software. I mention that the code will be licensed to them, but do not mention specifics about exclusivity, ability to produce derivatives etc. As such, a client has raised concerns about the copyright section of my contract, and has suggested that I reword it such that all copyrights are transferred entirely to the client on final payment for the project. This will almost certainly reduce my ability to distribute the software I have created; I would much prefer to find a more mutually beneficial agreement where both our concerns are appeased. Are there any tried and true approaches to licensing software in this kind of situation? To summarise: I want to maintain the ability to license (parts of) the software under my own terms, independently of my relationship with the client; with some guarantee to the client that no trade-secrets or critical business logic will be shared; giving them the ability to re-use my code in their future projects; but not necessarily letting them sell it (I'm not sure about this, though...what happens if they sell their business and the software along with it?) I realise that everyone's feedback is going to be prefixed with "IANAL", however I appreciate any thoughts you might have on the matter.

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• The way cores, processes, and threads work exactly?

  - by unknownthreat

  I need a bit of an advice for understanding how this whole procedure work exactly. If I am incorrect in any part described below, please correct me. In a single core CPU, it runs each process in the OS, jumping around from one process to another to utilize the best of itself. A process can also have many threads, in which the CPU core runs through these threads when it is running on the respective process. Now, on a multiple core CPU, Do the cores run in every process together, or can the cores run separately in different processes at one particular point of time? For instance, you have program A running two threads, can a duo core CPU run both threads of this program? I think the answer should be yes if we are using something like OpenMP. But while the cores are running in this OpenMP-embedded process, can one of the core simply switch to other process? For programs that are created for single core, when running at 100%, why the CPU utilization of each core are distributed? (ex. A duo core CPU of 80% and 20%. The utilization percentage of all cores always add up to 100% for this case.) Do the cores try help each other run each thread of each process in some ways? Frankly, I'm not sure how this works exactly. Any advice is appreciated.

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• A generic C++ library that provides QtConcurrent functionality?

  - by Lucas

  QtConcurrent is awesome. I'll let the Qt docs speak for themselves: QtConcurrent includes functional programming style APIs for parallel list processing, including a MapReduce and FilterReduce implementation for shared-memory (non-distributed) systems, and classes for managing asynchronous computations in GUI applications. For instance, you give QtConcurrent::map() an iterable sequence and a function that accepts items of the type stored in the sequence, and that function is applied to all the items in the collection. This is done in a multi-threaded manner, with a thread pool equal to the number of logical CPU's on the system. There are plenty of other function in QtConcurrent, like filter(), filteredReduced() etc. The standard CompSci map/reduce functions and the like. I'm totally in love with this, but I'm starting work on an OSS project that will not be using the Qt framework. It's a library, and I don't want to force others to depend on such a large framework like Qt. I'm trying to keep external dependencies to a minimum (it's the decent thing to do). I'm looking for a generic C++ framework that provides me with the same/similar high-level primitives that QtConcurrent does. AFAIK boost has nothing like this (I may be wrong though). boost::thread is very low-level compared to what I'm looking for. I know C# has something very similar with their Parallel Extensions so I know this isn't a Qt-only idea. What do you suggest I use?

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• What about parallelism across network using multiple PCs?

  - by MainMa

  Parallel computing is used more and more, and new framework features and shortcuts make it easier to use (for example Parallel extensions which are directly available in .NET 4). Now what about the parallelism across network? I mean, an abstraction of everything related to communications, creation of processes on remote machines, etc. Something like, in C#: NetworkParallel.ForEach(myEnumerable, () => { // Computing and/or access to web ressource or local network database here }); I understand that it is very different from the multi-core parallelism. The two most obvious differences would probably be: The fact that such parallel task will be limited to computing, without being able for example to use files stored locally (but why not a database?), or even to use local variables, because it would be rather two distinct applications than two threads of the same application, The very specific implementation, requiring not just a separate thread (which is quite easy), but spanning a process on different machines, then communicating with them over local network. Despite those differences, such parallelism is quite possible, even without speaking about distributed architecture. Do you think it will be implemented in a few years? Do you agree that it enables developers to easily develop extremely powerfull stuff with much less pain? Example: Think about a business application which extracts data from the database, transforms it, and displays statistics. Let's say this application takes ten seconds to load data, twenty seconds to transform data and ten seconds to build charts on a single machine in a company, using all the CPU, whereas ten other machines are used at 5% of CPU most of the time. In a such case, every action may be done in parallel, resulting in probably six to ten seconds for overall process instead of forty.

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• asp.net, wcf authentication and caching

  - by andrew

  I need to place my app business logic into a WCF service. The service shouldn't be dependent on ASP.NET and there is a lot of data regarding the authenticated user which is frequently used in the business logic hence it's supposed to be cached (probably using a distributed cache). As for authentication - I'm going to use two level authentication: Front-End - forms authentication back-end (WCF Service) - message username authentication. For both authentications the same custom membership provider is supposed to be used. To cache the authenticated user data, I'm going to implement two service methods: 1) Authenticate - will retrieve the needed data and place it into the cache(where username will be used as a key) 2) SignOut - will remove the data from the cache Question 1. Is correct to perform authentication that way (in two places) ? Question 2. Is this caching strategy worth using or should I look at using aspnet compatible service and asp.net session ? Maybe, these questions are too general. But, anyway I'd like to get any suggestions or recommendations. Any Idea

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• Why is there so much XML in Java these days?

  - by BD at Rivenhill

  This is really more of a philosophy/design issue. I did some work in Java back in the middle 90's and again in the early 2000's and now I'm coming back to it after spending a lot of time in C/C++ and it seems like there was an explosion of XML dependency while I was gone. Major build system tools like ant and maven depend on XML for their configuration, but I'm actually more concerned with all the frameworks, such as Spring, Hibernate, etc. My experience is that powerful supporting libraries like these are where a developer can really get leverage for building programs with lots of features without writing a lot of code, but it really seems like I'm getting one language for the price of two here. I write a bunch of Java classes, but then I also write a bunch of XML files to glue them together. The things that get done in the XML are things that I can see reasonable ways of doing in straight code without the middleman, and they don't really seem to be treated exactly like configuration files: they change rarely and they end up getting committed to source code control like the Java code itself, but they are distributed with the resulting application and need to be unpacked and installed in the classpath in order to get the application to work. I'm working with server applications that are not web-based, so maybe the domain is a bit different from what most people are doing, but I just can't help feeling that I must be doing something wrong here. Can someone point me to a good source of information for why these design choices were made and what problems they are meant to solve so that I can analyze my own experiences in this context?

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• How do software projects go over budget and under-deliver?

  - by Carlos

  I've come across this story quite a few times here in the UK: NHS Computer System Summary: We're spunking £12 Billion on some health software with barely anything working. I was sitting the office discussing this with my colleagues, and we had a little think about. From what I can see, all the NHS needs is a database + middle tier of drugs/hospitals/patients/prescriptions objects, and various GUIs for doctors and nurses to look at. You'd also need to think about security and scalability. And you'd need to sit around a hospital/pharmacy/GPs office for a bit to figure out what they need. But, all told, I'd say I could knock together something with that kind of structure in a couple of days, and maybe throw in a month or two to make it work in scale. If I had a few million quid, I could probably hire some really excellent designers to make a maintainable codebase, and also buy appropriate hardware to run the system on. I hate to trivialize something that seems to have caused to much trouble, but to me it looks like just a big distributed CRUD + UI system. So how on earth did this project bloat to £12B without producing much useful software? As I don't think the software sounds so complicated, I can only imagine that something about how it was organised caused this mess. Is it outsourcing that's the problem? Is it not getting the software designers to understand the medical business that caused it? What are your experiences with projects gone over budget, under delivered? What are best practices for large projects? Have you ever worked on such a project?

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• Are there any changes in the licensing of Visual Studio 2013 Express editions?

  - by Ramón García-Pérez

  As was going through reading the license.htm file provided as part of the VS2013_RTM_WebExp_ENU.iso offline installation media for the Visual Studio 2013 Express for Web, section 6 reads as follows: 6. PACKAGE MANAGER AND THIRD PARTY SOFTWARE INSTALLATION FEATURES. The software includes the following features (each a “Feature”), each of which enables you to obtain software applications or packages through the Internet from other sources: Extension Manager, New Project Dialog, Web Platform Installer, and Microsoft NuGet-Based Package Manager. Those software applications and packages are offered and distributed in some cases by third parties and in some cases by Microsoft, but each such application or package is under its own license terms. Microsoft is not developing, distributing or licensing any of the third-party applications or packages to you, but instead, as a convenience, enables you to use the Features to access or obtain those applications or packages directly from the third-party application or package providers. By using the Features, you acknowledge and agree that: you are obtaining the applications or packages from such third parties and under separate license terms applicable to each application or package (including, with respect to the package-manager Features, any terms applicable to software dependencies that may be included in the package); MICROSOFT MAKES NO REPRESENTATIONS, WARRANTIES OR GUARANTEES AS TO THE FEED OR GALLERY URL, ANY FEEDS OR GALLERIES FROM SUCH URL, THE INFORMATION CONTAINED THEREIN, OR ANY SOFTWARE APPLICATIONS OR PACKAGES REFERENCED IN OR ACCESSED BY YOU THROUGH SUCH FEEDS OR GALLERIES. MICROSOFT GRANTS YOU NO LICENSE RIGHTS FOR THIRD-PARTY SOFTWARE APPLICATIONS OR PACKAGES THAT ARE OBTAINED USING THE FEATURES. Are there any changes in the licensing of Visual Studio 2013 Express editions? If so, does this means that Visual Studio extensions installation in Express Editions is now allowed? PS: Previous versions of the Express editions did not allow the installation of extensions as per "EULA/TOS" discussed here: Limitations of Visual Studio 2012 Express Desktop

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• Web services or shared database for (game) server communication?

  - by jaaronfarr

  We have 2 server clusters: the first is made up of typical web applications backed by SQL databases. The second are highly optimized multiplayer game servers which keep all data in memory. Both clusters communicate with clients via HTTP (Ajax with JSON). There are a few cases in which we need to share data between the two server types, for example, reporting back and storing the results of a game (should ultimately end up in the database). We're considering several approaches for inter-server communication: Just share the MySQL databases between clusters (introduce SQL to the game servers) Sharing data in a distributed key-value store like Memcache, Redis, etc. Use an RPC technology like Google ProtoBufs or Apache Thrift Using RESTful web services (the game server would POST back to the web servers, for example) At the moment, we're leaning towards web services or just sharing the database. Sharing the database seems easy, but we're concerned this adds extra memory and a new dependency into the game servers. Web services provide good separation of concerns and fit with the existing Ajax we use, but add complexity, overhead and many more ways for communication to fail. Are there any other good reasons not to use one or the other approach? Which would be easier to scale?

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• In maven2, how do I assemble bits and pieces of different modules to create final distributions?

  - by Carcassi

  I have four maven project: client api jar web service war ui jar web interface war The service war will need to be packaged to include the client api jar, together with javadocs (so that each version is distributed with a matching client and documentation). The web interface war will need the ui jar and all the dependencies (webstart/applet deployment). So I need a 5th project that does all the packaging. How to do this with ant or a script is perfectly clear to me, but not in maven. I tried the following: having the javadocs included as part of the war packaging: this requires the execution of the javadocs goal in project 1 before execution of package in project 2. Haven't found a way to bind plugins/goals across different projects. Using the assembly plugin in project2 had the same problem. create a fifth project and use the assembly plugin. Still the same problems as before, with the problem that since I need different pieces from each sub-project I do not understand how this can be done using the assembly. Is this too hard to do in maven, and should I just give up? Or I am looking at it wrong, in which case, how should I be looking at it? Thanks! Upon further reflection, here is a partial answer: Each project should build all its artifacts. This is done by having the plugins configured to run as per the prepare-resources and package phases. So, in my case, I prepare all that needs to be generated (jar, javadocs, xsd documentation, ...) as different artifacts so that a single "package" goal execution creates all. So, it's not "how project 2 forces project 1 to run different goals", but it's "make project 1 create all of its artifact as part as the normal lifecycle). This seems to simplify things.

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• Fastest reliable way for Clojure (Java) and Ruby apps to communicate

  - by jkndrkn

  Hi There, We have cloud-hosted (RackSpace cloud) Ruby and Java apps that will interact as follows: Ruby app sends a request to Java app. Request consists of map structure containing strings, integers, other maps, and lists (analogous to JSON). Java app analyzes data and sends reply to Ruby App. We are interested in evaluating both messaging formats (JSON, Buffer Protocols, Thrift, etc.) as well as message transmission channels/techniques (sockets, message queues, RPC, REST, SOAP, etc.) Our criteria: Short round-trip time. Low round-trip-time standard deviation. (We understand that garbage collection pauses and network usage spikes can affect this value). High availability. Scalability (we may want to have multiple instances of Ruby and Java app exchanging point-to-point messages in the future). Ease of debugging and profiling. Good documentation and community support. Bonus points for Clojure support. What combination of message format and transmission method would you recommend? Why? I've gathered here some materials we have already collected for review: Comparison of various java serialization options Comparison of Thrift and Protocol Buffers (old) Comparison of various data interchange formats Comparison of Thrift and Protocol Buffers Fallacies of Protocol Buffers RPC features Discussion of RPC in the context of AMQP (Message-Queueing) Comparison of RPC and message-passing in distributed systems (pdf) Criticism of RPC from perspective of message-passing fan Overview of Avro from Ruby programmer perspective

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• Behavior of Struts2 and convention-plugin when there is Index(extends ActionSupport)

  - by hanishi

  We have an Action class named 'Index' immediately under com.example.common.action and is annotated @ParentPackage('default') which is declared in package directive in struts.xml and has "/" for its namespace and extends "struts-default". It also declares @Result so that it responses with jsp files corresponding the string values returned by its execute() method. In our struts.xml, the following struts setting is configured along with other necessary configurations that are needed for convention-plugin. <constant name="struts.action.extension" value=","/> When accessing /my_context/none_existing_path, the request apparently hits this Index class and the contents of the jsp declared in the Index's @Result section gets returned. However, if we provide /my_context/, we receive the following error: HTTP Status 404-There is no Action mapped for namespace[/] and action name [] associated with context path [/my_context]. We want to know the reason why accessing /my_context/none_existing_path, where none_existing_path has no matching action, can fallback to Index class, but error is returned when when the URL requested is just /my_context/. Currently, our convention-plugin settings are declared as follows: <constant name="struts.convention.package.locators.basePackage" value="com.example"/> <constant name="struts.convention.package.locators" value="action"/> Strangely, if we changed the value of the struts.convention.package.locators.basePackage to om.example.common, in which the aforementioned Index file can be immediately found by narrowing the search scope, requesting /my_context/ displays the content of the jsps declared in @Result section of the Index class. However, as our action classes are distributed throughout the com.example.[a-z].action packages, where [a-z] represents the large volume of directories we have in our package structure, we cannot use this trick as a workaround. We have also tried placing index.jsp at the top level of the class path, and have the index.jsp redirect to /my_context/index, which worked but not what we want. Could this be a bug? We appreciate your responses. Thank you in advance. EDIT: JIRA registered, problem solved (from Struts 2.3.12 up)

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• Hadoop File Read

  - by user3684584

  Hadoop Distributed Cache Wordcount example in hadoop 2.2.0. Copied file into hdfs filesystem to be used inside setup of mapper class. protected void setup(Context context) throws IOException,InterruptedException { Path[] uris = DistributedCache.getLocalCacheFiles(context.getConfiguration()); cacheData=new HashMap(); for(Path urifile: uris) { try { BufferedReader readBuffer1 = new BufferedReader(new FileReader(urifile.toString())); String line; while ((line=readBuffer1.readLine())!=null) { System.out.println("**************"+line); cacheData.put(line,line); } readBuffer1.close(); } catch (Exception e) { System.out.println(e.toString()); } } } Inside Driver Main class Configuration conf = new Configuration(); String[] otherArgs = new GenericOptionsParser(conf,args).getRemainingArgs(); if (otherArgs.length != 3) { System.err.println("Usage: wordcount <in> <out>"); System.exit(2); } Job job = new Job(conf, "word_count"); job.setJarByClass(WordCount.class); job.setMapperClass(Map.class); job.setReducerClass(Reduce.class); job.setOutputKeyClass(Text.class); job.setOutputValueClass(IntWritable.class); FileInputFormat.addInputPath(job, new Path(otherArgs[0])); Path outputpath=new Path(otherArgs[1]); outputpath.getFileSystem(conf).delete(outputpath,true); FileOutputFormat.setOutputPath(job,outputpath); System.out.println("CachePath****************"+otherArgs[2]); DistributedCache.addCacheFile(new URI(otherArgs[2]),job.getConfiguration()); System.exit(job.waitForCompletion(true) ? 0 : 1); But getting exception java.io.FileNotFoundException: file:/home/user12/tmp/mapred/local/1408960542382/cache (No such file or directory) So Cache functionality not working properly. Any Idea ?

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• when to use Hibernate vs. Simple ResultSets for small application

  - by luke

  I just started working on upgrading a small component in a distributed java application. The main application is a rather complicated applet/servlet combo running on JBoss and it extensively uses Hibernate for its DataAccess. The component i am working on however is very a very straightforward data importing service. Basically the workflow is Listen for a network event Parse the data packet, extract a set of identifiers Map the identifier set to a primary key in our database Parse the rest of the packet and insert items in a related table using the foreign key found in step 3 Repeat in the previous version of this component it used a hibernate based DAL, that is no longer usable for a variety of reasons (in particular it is EOL), so I am in charge of replacing the Data Access layer for this component. So on the one hand I think i should use Hibernate because that's what the rest of the application does, but on the other i think i should just use regular java.sql.* classes because my requirements are really straightforward and aren't expected to change any time soon. So my question is (and i understand it is subjective) at what point do you think that the added complexity of using an ORM tool (in terms of configuration, dependencies...) is worth it? UPDATE due to the way the DataAccesLayer for the main application was written (weird dependencies) i cannot easily use it, i would have to implement it myself.

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• Creating multiple instances of a generic database

  - by sagekilla

  Hi all, currently I'm trying to have a setup where a generic database is distributed to students. They would develop an application using this database (Say a shopping cart application), submit their project onto our server, and then it would be graded automatically. These databases are being run in Microsoft SQL Server 2005. We're using user instances to instantiate each database, and multiple requests could be serviced at once. But, the problem is when more than one student submitted a project to be graded, the first database to be instantiated would be the only one and would overwrite all other copies that were currently open. So if stu1 modified his database and stu2 and stu3 had their projects being graded concurrently, at the end of the grading stu1, stu2, and stu3 would have identical DB's at the end. Is there any way I can have multiple independent copies of a generic database, each of which I can load concurrently and modify without having any changes made to any one affecting the others? I did a little reading, and thought it might be possible to do something along the lines of: Student submits project Attach the database with unique db name (specified by student) Do all necessary operations Detach the database I'm unsure if this would fix our problem or be possible, so any help would be much appreciated!

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• Mysql - wondering about scaling a twitter-like application ?

  - by user246114

  Hi, I'm developing an app that is vaguely similar to twitter, in that it allows users to follow one another. I wanted to do this using google app engine, for its scalability promises, but it's proving kind of difficult to get running for a few different reasons. I'd basically like to have a _users table, and a _followers table. Users go into the users table, follower relationships go into _followers. The problem is that each row in the users table will probably have like 100 corresponding records in the _followers table as users start following one another. So the number of rows is going to explode quickly. Using app engine, the volume [shouldn't] be a problem. If I go with mysql, and I do actually start to get some traction, how do I scale this up? Am I going to just end up moving to a distributed database in the end anyway? Should I fight it out with google app engine? I read that Twitter was using mysql, and they've run into this problem, and are now switching to cassandra. Thanks

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• In sync query calls, one query causing other query to run slower. Why?

  - by Irchi

  Sorry for the long question, but I think this is an interesting situation and I couldn't find any explanations for it: I was involved in optimization of an application that performed a large number of sequential SELECT and INSERT statements on a single dedicated SQL Server database. The process needs to INSERT a large number of records into a table, but for each of them there should be some value mappings, which performed using SELECT statements on another table in the same database. For a specific execution, it took 90 minutes to run. I used a profiler (JProfiler - the application is Java-based) to determine how much time does each part of the application take. It yields that 60% of the time was spent on INSERT method calls, and almost 20% on SELECT calls (the rest distributed in other parts). After some trials, I came to this situation: I commented out the INSERT query that took 60% of the time. I was expecting for the total run time to be around 35 minutes, as I have removed 60% of the 90 minutes. But the whole process took the same 90 minutes (doing only SELECTs and nothing else), but each SELECT took longer this time! Everything was running sync, there were no async calls. And there was only one single thread of execution. SELECT and INSERT queries are very simple, and don't have anything special, and they are on different tables, but on the same DB. I tested with both the DB on the application machine, and on a remote network machine. I can't think of any explanation for this, as the Profiler (Application profiler, not SQL Profiler) reported the changes in the method call times, and by removing INSERT statements SELECT statements took longer to run. Can anyone give me some kind of explanation of what could have happened? (there can't be cache / query optimization stuff, because the queries were run in sync, and in a single thread, and it was far from affecting the cache this much) I should note that the bottleneck of the speed was in SQL server, using most of the CPU time.

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• MATLAB: What is an appropriate Data Structure for a Matrix with Random Variable Entries?

  - by user568249

  I'm currently working in an area that is related to simulation and trying to design a data structure that can include random variables within matrices. To motivate this let me say I have the following matrix: [a b; c d] I want to find a data structure that will allow for a, b, c, d to either be real numbers or random variables. As an example, let's say that a = 1, b = -1, c = 2 but let d be a normally distributed random variable with mean 0 and SD 1. The data structure that I have in mind will give no value to d. However, I also want to be able to design a function that can take in the structure, simulate an uniform(0,1), obtain a value for d using an inverse CDF and then spit out an actual matrix. I have several ideas to do this (all related to the MATLAB icdf function) but would like to know how more experienced programmers would do this. In this application, it's important that the structure is as "lean" as possible since I will be working with very very large matrices and memory will be an issue.

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• Kendo Grid: Foreign Key Dropdown does not update grid cell after update

  - by JookyDFW

  I have a Kendo MVC grid that contains a nullable property (short) that is bound as a foreign key and uses a dropdown list as an editor template. I am also using inline editing. When the property value is null, the dropdown list selected value does not get set into the grid cell after the update button is clicked. This works fine if incell editing is used. I am looking for a workaround that will solve my problem. I am including a stripped down version of my code below Everything works if the nullable value is set to a non-null value. GRID @(Html.Kendo().Grid<AssetViewModel>() .Name("DealAssets") .Columns(c => { c.Bound(x => x.Name); c.ForeignKey(x => x.AssetTypeID, (IEnumerable<SelectListItem>)ViewBag.AssetTypeList, "Value", "Text"); c.ForeignKey(x => x.SeniorityTypeID, seniorityTypeList, "Value", "Text").EditorTemplateName("GridNullableForeignKey"); c.ForeignKey(x => x.RateBaseID, rateBaseList, "Value", "Text").EditorTemplateName("GridNullableForeignKey"); ; c.Command(m => { m.Edit(); m.Destroy(); }); }) .ToolBar(toolbar => toolbar.Create().Text("Add New Asset")) .Editable(x => x.Mode(GridEditMode.InLine)) .DataSource(ds => ds .Ajax() .Model(model => model.Id(request => request.ID)) .Read(read => read.Action("ReadAssets", "Deal", new { id = Model.ID })) .Create(create => create.Action("CreateAsset", "Deal", new { currentDealID = Model.ID })) .Update(update => update.Action("UpdateAsset", "Deal")) .Destroy(destroy => destroy.Action("DeleteAsset", "Deal")) ) ) EDITOR TEMPLATE @model short? @{ var controlName = ViewData.TemplateInfo.GetFullHtmlFieldName(""); } @( Html.Kendo().DropDownListFor(m => m) .Name(controlName) .OptionLabel("- Please select -") .BindTo((SelectList)ViewData[ViewData.TemplateInfo.GetFullHtmlFieldName("") + "_Data"]) ) UPDATE ACTION public ActionResult UpdateAsset([DataSourceRequest] DataSourceRequest request, int ID) { var dealAsset = DataContext.DealAssets.SingleOrDefault(o => o.ID == ID); if (dealAsset != null) { if (TryUpdateModel(dealAsset.Asset, new[] {"Name","AssetTypeID","SeniorityTypeID","RateBaseID" })) { DataContext.SaveChanges(); } } return Json(new[] { new AssetViewModel(dealAsset) }.ToDataSourceResult(request, ModelState), JsonRequestBehavior.AllowGet); }

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• WMI Rights required to read root\MicrosoftIISv2 in IIS7 with IIS6 compatibility mode

  - by JoeBilly

  I need to manage my IIS7 (Windows Server 2008) remotely with a WMI IIS6 API. So I added the IIS6 WMI Compatibility and IIS6 Metabase Compatibility roles to access the root\MicrosoftIIsv2 namespace. I have a domain account which is not administrator on the remote machine ; with this right, everything is ok. I configured these rights for my domain account to access the root\MicrosoftIIsv2 WMI namespace remotely ; note that these rights work perfectly on a IIS6 and Windows Server 2003 : DCOM : Account in Distributed COM Users Remote & local access to DCOM WMI : Root\CIMV2 (I need access here too) Execute methods, Enable Account, Remote Enable Root\Default (I need access here too) Execute methods, Enable Account, Remote Enable Root\MicrosoftIISv2 Execute methods, Enable Account, Provider Write, Remote Enable IIS Metabase (Metabase Explorer) : LM Full Control (W3SVC inherits these permissions) I tried to give some access on C:\Windows\System32\inetsrv too ; don't know if needed. My issue is : I can't list the IIS WebSites (\root\MicrosoftIISv2:IIsWebServerSetting.Name="W3SVC/*"). I don't get an 'access denied' but nothing is returned. My API and powershell tests can connect and execute queries in the root\MicrosoftIISv2 namespace I can read the IIsComputer class ex: Get-WmiObject IIsComputer -namespace "ROOT\MicrosoftIISv2" -authentication PacketPrivacy | SELECT * I can't read the IIsWebServerSetting, IIsWebServer ... to list the WebSites : the query returns an empty collection ex: Get-WmiObject IIsWebServerSetting -namespace "ROOT\MicrosoftIISv2" -authentication PacketPrivacy | SELECT ServerComment All queries work perfectly if the account is administrator as already said I am using PacketPrivacy authentication FI: I got a Warning Event 5605 with the Administrator right or not, that does not seem to have an impact : The root\MicrosoftIISv2 namespace is marked with the RequiresEncryption flag. Access to this namespace might be denied if the script or application does not have the appropriate authentication level. Change the authentication level to Pkt_Privacy and run the script or application again Ok, I have some more informations, when I use IIS 6 Metabase Explorer with my administrator account I can see the rights are correctly inherited for my non-administrator account. But when I try to connect using my non-administrator account, I can list the LM node, but get an "access denied, failed to get a key's data" when I try to browse the child nodes. I'll check further. I tried to Trace the WMI Activity, and everything seems OK ; this tends to confirm that the problem lies in IIS Rights.

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• Windows Server 2012 Branchcache vs. DFS-R

  - by TheCleaner

  Warning, subjective question ahead! But hopefully a good one that won't get closed. SCENARIO: I have a branch office that currently has no on-premise server. They access everything including a DC across a 12Mbps WAN link (MPLS). The link isn't saturated, averaging around 20% utilization. The circuit is very stable and has a high SLA and excellent uptime. However, large file transfers (mainly reads, not writes) from the file server across the WAN can be slow. We don't currently utilize DFS. RESEARCH DONE: I'm aware of WAN acceleration, using either dedicated hardware (Riverbed) or a dedicated software VM (Silver Peak) for example. But the pricing is outside of our current budget and the need isn't quite there yet from our perspective (since the issue is mainly in a "pull" scenario not necessarily push/pull). I'm mainly looking at deploying a Windows server at this branch office and either utilizing DFS-R or BranchCache. Looking at a table comparison and assuming we are looking at a "hosted branchcache server" and not simply distributed: It would appear there are benefits to both, even if both are "hosted" on a server. QUESTIONS I ACTUALLY HAVE: In what scenarios do each of these techs shine and where do you choose one over the other? Looking at a hosted Branchcache server, can you set "pre-fetching" of certain folders/files on the central file server so that they are immediately accessible locally at the branch? Do you have to do this on a schedule (if it is possible)? Looking at DFS-R my concern (and apparently solved with 3rd party apps) is file locking and making sure the file gets updated properly during a write operation (ie, making sure if both copies are accessed and both are written to, which file takes precedence and what happens to the changes?). Ideal it would seem would be to lock any alternate replicas of the data, but is it really that big of an issue? Does Branchcache lock the central file for editing? Does branchcache only transmit the deltas back to the central file of what has changed? Would either technology be ill advised if the branch office server was going to be utilized as a domain controller as well?

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