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• Need help with WCF design

  - by Jason

  I have been tasked with creating a set of web services. We are a Microsoft shop, so I will be using WCF for this project. There is an interesting design consideration that I haven't been able to figure out a solution for yet. I'll try to explain it with an example: My WCF service exposes a method named Foo(). 10 different users call Foo() at roughly the same time. I have 5 special resources called R1, R2, R3, R4, and R5. We don't really need to know what the resource is, other than the fact that a particular resource can only be in use by one caller at a time. Foo() is responsible to performing an action using one of these special resources. So, in a round-robin fashion, Foo() needs to find a resource that is not in use. If no resources are available, it must wait for one to be freed up. At first, this seems like an easy task. I could maybe create a singleton that keeps track of which resources are currently in use. The big problem is the fact that I need this solution to be viable in a web farm scenario. I'm sure there is a good solution to this problem, but I've just never run across this scenario before. I need some sort of resource tracker / provider that can be shared between multiple WCF hosts. Any ideas from the architects out there would be greatly appreciated!

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• Systems design question: DB connection management in load-balanced n-tier

  - by aoven

  I'm wondering about the best approach to designing a DB connection manager for a load-balanced n-tier system. Classic n-tier looks like this: Client -> BusinessServer -> DBServer A load-balancing solution as I see it would then look like this: +--> ... +--+ +--> BusinessServer +--+--> SessionServer --+ Client -> Gateway --+--> BusinessServer +--| +--> DBServer +--> BusinessServer +--+--------------------+ +--> ... +--+ As pictured, the business server component is being load-balanced via multiple instances, and a hardware gateway is distributing the load among them. Session server probably needs to be situated outside the load-balancing array, because it manages state, which mustn't be duplicated. Barring any major errors in design so far, what is the best way to implement DB connection management? I've come up with a couple of options, but there may be others I'm not aware of: Introduce a new Broker component between the DBServer and the other components and let it handle the DB connections. The upside is that all the connections can be managed from a single point, which is very convenient. The downside is that now there is an additional "single point of failure" in the system. Other components must go through it for every request that involves DB in some way, which also makes this a bottleneck. Move the DB connection management into BusinessServer and SessionServer components and let each handle its own DB connections. The upside is that there is no additional "single point of failure" or bottleneck components. The downside is that there is also no control over possible conflicts and deadlocks apart from what DBServer itself can provide. What else can be done? FWIW: Technology is .NET, but none of the vendor-specific stacks are used (e.g. no WCF, MSMQ or the like).

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• Nested namespaces, correct static library design issues

  - by PeterK

  Hello all, I'm currently in the process of developing a fairly large static library which will be used by some tools when it's finished. Now since this project is somewhat larger than anything i've been involved in so far, I realized its time to think of a good structure for the project. Using namespaces is one of those logical steps. My current approach is to divide the library into parts (which are not standalone, but their purpose calls for such a separation). I have a 'core' part which now just holds some very common typedefs and constants (used by many different parts of the library). Other parts are for example some 'utils' (hash etc.), file i/o and so on. Each of these parts has its own namespace. I have nearly finished the 'utils' part and realized that my approach probably is not the best. The problem (if we want to call it so) is that in the 'utils' namespace i need something from the 'core' namespace which results in including the core header files and many using directives. So i began to think that this probably is not a good thing and should be changed somehow. My first idea is to use nested namespaces as to have something like core::utils. Since this will require some heavy refactoring i want to ask here first. What do you think? How would you handle this? Or more generally: How to correctly design a static library in terms of namespaces and code organization? If there are some guidelines or articles about it, please mentoin them too. Thanks. Note: i'm quite sure that there are more good approaches than just one. Feel free to post your ideas, suggestions etc. Since i'm designing this library i want it to be really good. The goal is to make it as clean and FAST as possible. The only problem is that i will have to integrate a LOT of existing code and refactor it, which will really be a painful process (sigh) - thats why good structure is so important)

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• Django Database design -- Is this a good stragety for overriding defaults

  - by rh0dium

  Hi SO's I have a question on good database design practices and I would like to leverage you guys for pointers. The project started out simple. Hey we have a bunch of questions we want answered for every project (no problem) Which turned into... Hey we have so many questions can we group them into sections (yup we can do that) Which lead into.. Can we weight these questions and I don't really want some of these questions for my project (Yes but we are getting difficult) And then I'm thinking they will want to have each section have it's own weight.. Requirements So there's the requirements - For n number of project Allow a admin member the ability select the questions for a project Allow the admin member to re-weigh or use the default weights for the questions Allow the admin member to re-weight the sections Allow team members to answer the questions. So here is what I came up with. Please feel free to comment and provide better examples models.py from django.db import models from django.contrib.sites.models import Site from django.conf import settings class Section(models.Model): """ This describes the various sections for a checklist: """ name = models.CharField(max_length=64) description = models.TextField() class Question(models.Model): """ This simply provides a simple way to list out the questions. """ question = models.CharField(max_length=255) answer_type = models.CharField(max_length=16) description = models.TextField() section = models.ForeignKey(Section) class ProjectQuestion(models.Model): """ These are the questions relevant to the project """ question = models.ForeignKey(Question) answer = models.CharField(max_length=255) required = models.BooleanField(default=True) weight = models.FloatField(default = XXX) class Project(models.Model): """ Here is where we want to gather our questions """ questions = models.ManyToManyField(ProjectQuestion) Immediate questions: - When I start a project - any ideas on how to "pre-populate" the questions (and ultimately the weights) for the project? - Is there a generally accepted method for doing this process that I am missing? Basically the idea that you refer to the questions overide your own default weight, and store the answer? - It appears that a good chuck of the work will be done in the views and that a lot of checking will need to occur there? Is that OK? Again - feel free to give me better strategies!! Thanks

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• Ruby Design Problem for SQL Bulk Inserter

  - by crunchyt

  This is a Ruby design problem. How can I make a reusable flat file parser that can perform different data scrubbing operations per call, return the emitted results from each scrubbing operation to the caller and perform bulk SQL insertions? Now, before anyone gets narky/concerned, I have written this code already in a very unDRY fashion. Which is why I am asking any Ruby rockstars our there for some assitance. Basically, everytime I want to perform this logic, I create two nested loops, with custom processing in between, buffer each processed line to an array, and output to the DB as a bulk insert when the buffer size limit is reached. Although I have written lots of helpers, the main pattern is being copy pasted everytime. Not very DRY! Here is a Ruby/Pseudo code example of what I am repeating. lines_from_file.each do |line| line.match(/some regex/).each do |sub_str| # Process substring into useful format # EG1: Simple gsub() call # EG2: Custom function call to do complex scrubbing # and matching, emitting results to array # EG3: Loop to match opening/closing/nested brackets # or other delimiters and emit results to array end # Add processed lines to a buffer as SQL insert statement @buffer << PREPARED INSERT STATEMENT # Flush buffer when "buffer size limit reached" or "end of file" if sql_buffer_full || last_line_reached @dbc.insert(SQL INSERTS FROM BUFFER) @buffer = nil end end I am familiar with Proc/Lambda functions. However, because I want to pass two separate procs to the one function, I am not sure how to proceed. I have some idea about how to solve this, but I would really like to see what the real Rubyists suggest? Over to you. Thanks in advance :D

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• Observer Design Pattern - multiple event types

  - by David

  I'm currently implementing the Observer design pattern and using it to handle adding items to the session, create error logs and write messages out to the user giving feedback on their actions (e.g. You've just logged out!). I began with a single method on the subject called addEvent() but as I added more Observers I found that the parameters required to detail all the information I needed for each listener began to grow. I now have 3 methods called addMessage(), addStorage() and addLog(). These add data into an events array that has a key related to the event type (e.g. log, message, storage) but I'm starting to feel that now the subject needs to know too much about the listeners that are attached. My alternative thought is to go back to addEvent() and pass an event type (e.g. USER_LOGOUT) along with the data associated and each Observer maintains it's own list of event handles it is looking for (possibly in a switch statement), but this feels cumbersome. Also, I'd need to check that sufficient data had also been passed along with the event type. What is the correct way of doing this? Please let me know if I can explain any parts of this further. I hope you can help and see the problem I'm battling with.

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• CSS Experts required - problems with Z-Index stack in my page design

  - by Jack W-H

  Howdy y'all! Basically I'm having some problems with Z-Index. Although I'm not amazing at CSS I would reckon I was reasonably good, but really can't work this out. You'll see at the URL... http://howcode.com/code/ ... that my problem is that links in the returned 'Popular' results aren't clickable or anything. I've concluded this is due to their Z-Index being messed up. I had to fiddle and tweak with Z-Index to get the tabs - Popular, Top Rated, Featured etc. - to show above the codebg div. When I adjusted the Z-Index so that the results were definitely on top, they acted as normal - text could be selected, the ratings images hovered, etc. etc. However the downside to this was that my Popular, Top Rated, Featured tabs were all placed BENEATH the background image for the returned results. If anyone can post a workaround or alteration to my CSS that would be much appreciated. Please don't forget this is a test site and design and any other URLs are likely not to work, I haven't uploaded any database configs yet or whatever! Attached are a couple of screenshots to clarify what I mean: This is what I WANT to happen (not that in actual fact in this screenshots link aren't clickable, just to demo my point though): This is what DOES happen when I adjust the Z-Index properties (I don't want this!): Thanks y'all!

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• MySQL Database Design with Internationalization

  - by Some name

  Hello, I'm going to start work on a medium sized application, and i'm planning it's db design. One thing that I'm not sure about is this. I will have many tables which will need internationalization, such as: "membership_options, gender_options, language_options etc" Each of these tables will share common i18n fields, like: "title, alternative_title, short_description, description" In your opinion which is the best way to do it? Have an i18n table with the same fields for each of the tables that will need them? or do something like: Membership table Gender table ---------------- -------------- id | created_at id | created_at 1 - 22.03.2001 1 - 14.08.2002 2 - 22.03.2001 2 - 14.08.2002 General translation table ------------------------- record_id | table_name | string_name | alternative_title| .... |id_language 1 - membership regular null 1 (english) 1 - membership normale null 2 (italian) 1 - gender man null 1(english) 1 -gender uomo null 2(italian) This would avoid me repeating something like: membership_translation table ----------------------------- membership_id | name | alternative_title | id_lang 1 regular null 1 1 normale null 2 gender_translation table ----------------------------- gender_id | name | alternative_title | id_lang 1 man null 1 1 uomo null 2 and so on, so i would probably reduce the number of db tables, but i'm not sure about performance.I'm not much of a DB designer, so please let me know.

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• Nested Data XML design

  - by esryl

  Looking to nest (to unlimited levels) elements in XML. Like so: <items> <item> <name>Item One</name> <item> <name>Item Two</name> </item> <item> <name>Item Three</name> <item> <name>Item Four</name> </item> <!-- etc... --> </item> </item> </items> However. While browsing for a solution I noticed in the comments of: http://stackoverflow.com/questions/988139/weird-nesting-in-xml while the above is well formed it would not validate against any sinsible DTD. Two things, what is a better way of nesting similar elements, and secondly what would be the design of the DTD. UPDATE: Would prefer to validate against an XML Schema rather than DTD.

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• Threadpool design question

  - by ZeroVector

  I have a design question. I want some feedback to know if a ThreadPool is appropriate for the client program I am writing. I am having a client running as a service processing database records. Each of these records contains connection information to external FTP sites [basically it is a queue of files to transfer]. A lot of them are to the same host, just moving different files. Therefore, I am grouping them together by host. I want to be able to create a new thread per host. I really don't care when the transfers finish, they just need to do all the work (or try to do) they were assigned, and then terminate once they are finished, cleaning up all resources they used in the process. I anticipate no more than 10-25 connections to be established. Once the transfer queue is empty, the program will simply wait until there are records in the queue again. Is the ThreadPool a good candidate for this or should I use a different approach? Edit: For the most part, this is the only significant custom application running on the server.

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• Proper API Design for Version Independence?

  - by Justavian

  I've inherited an enormous .NET solution of about 200 projects. There are now some developers who wish to start adding their own components into our application, which will require that we begin exposing functionality via an API. The major problem with that, of course, is that the solution we've got on our hands contains such a spider web of dependencies that we have to be careful to avoid sabotaging the API every time there's a minor change somewhere in the app. We'd also like to be able to incrementally expose new functionality without destroying any previous third party apps. I have a way to solve this problem, but i'm not sure it's the ideal way - i was looking for other ideas. My plan would be to essentially have three dlls. APIServer_1_0.dll - this would be the dll with all of the dependencies. APIClient_1_0.dll - this would be the dll our developers would actual refer to. No references to any of the mess in our solution. APISupport_1_0.dll - this would contain the interfaces which would allow the client piece to dynamically load the "server" component and perform whatever functions are required. Both of the above dlls would depend upon this. It would be the only dll that the "client" piece refers to. I initially arrived at this design, because the way in which we do inter process communication between windows services is sort of similar (except that the client talks to the server via named pipes, rather than dynamically loading dlls). While i'm fairly certain i can make this work, i'm curious to know if there are better ways to accomplish the same task.

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• Factorial function - design and test.

  - by lukas

  I'm trying to nail down some interview questions, so I stared with a simple one. Design the factorial function. This function is a leaf (no dependencies - easly testable), so I made it static inside the helper class. public static class MathHelper { public static int Factorial(int n) { Debug.Assert(n >= 0); if (n < 0) { throw new ArgumentException("n cannot be lower that 0"); } Debug.Assert(n <= 12); if (n > 12) { throw new OverflowException("Overflow occurs above 12 factorial"); } //by definition if (n == 0) { return 1; } int factorialOfN = 1; for (int i = 1; i <= n; ++i) { //checked //{ factorialOfN *= i; //} } return factorialOfN; } } Testing: [TestMethod] [ExpectedException(typeof(OverflowException))] public void Overflow() { int temp = FactorialHelper.MathHelper.Factorial(40); } [TestMethod] public void ZeroTest() { int factorialOfZero = FactorialHelper.MathHelper.Factorial(0); Assert.AreEqual(1, factorialOfZero); } [TestMethod] public void FactorialOf5() { int factOf5 = FactorialHelper.MathHelper.Factorial(5); Assert.AreEqual(120,factOf5); } [TestMethod] [ExpectedException(typeof(ArgumentException))] public void NegativeTest() { int factOfMinus5 = FactorialHelper.MathHelper.Factorial(-5); } I have a few questions: Is it correct? (I hope so ;) ) Does it throw right exceptions? Should I use checked context or this trick ( n 12 ) is ok? Is it better to use uint istead of checking for negative values? Future improving: Overload for long, decimal, BigInteger or maybe generic method? Thank you

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• C++ AI Design Question

  - by disney

  Hi, I am currently writing a bot for a MMORPG. Though, currently I am stuck at trying to figure out how to nicely implement this. The design problem is related to casting the character spells in the correct order. Here is a simple example to what I need to archieve. It's not related to casting them, but doing it in the correct order. I would know how simply cast them randomly, by checking which skill has not yet been casted, but in right order as being shown in the GUI, not really. note: the skill amount may differ, it's not always 3, maximum 10 though. Charactername < foobar has 3 skills. Skill 1: Name ( random1 ) cooldown ( 1000 ms ) cast duration ( 500 ms ) Skill 2: Name ( random2 ) cooldown ( 1500 ms ) cast duration ( 700 ms ) Skill 3: Name ( random3 ) cooldown ( 2000 ms ) cast duration ( 900 ms ) I don't really know how I could implement this, if anyone has some thoughts, feel free to share. I do know that most of the people don't like the idea of cheating in games, I don't like it either, nor I am actually playing the game, but its an interesting field for me. Thank you.

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• Enterprise Platform in Python, Design Advice

  - by Jason Miesionczek

  I am starting the design of a somewhat large enterprise platform in Python, and was wondering if you guys can give me some advice as to how to organize the various components and which packages would help achieve the goals of scalability, maintainability, and reliability. The system is basically a service that collects data from various outside sources, with each outside source having its own separate application. These applications would poll a central database and get any requests that have been submitted to perform on the external source. There will be a main website and REST/SOAP API that should also have access to the central data service. My initial thought was to use Django for the web site, web service and data access layer (using its built-in ORM), and then the outside source applications can use the web service(s) to get the information they need to process the request and save the results. Using this method would allow me to have multiple instances of the service applications running on the same or different machines to balance out the load. Are there more elegant means of accomplishing this? i've heard of messaging systems such as MQ, would something like that be beneficial in this scenario? My other thought was to use a completely separate data service not based on Django, and use some kind of remoting or remote objects (in they exist in Python) to interact with the data model. The downside here would be with the website which would become much slower if it had to push all of its data requests through a second layer. I would love to hear what other developers have come up with to achieve these goals in the most flexible way possible.

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• Complicated .NET factory design

  - by Tom W

  Hello SO; I'm planning to ask a fairly elaborate question that is also something of a musing here, so bear with me... I'm trying to design a factory implementation for a simulation application. The simulation will consist of different sorts of entities i.e. it is not a homogenous simulation in any respect. As a result, there will be numerous very different concrete implementations and only the very general properties will be abstracted at the top level. What I'd like to be able to do is create new simulation entities by calling a method on the model with a series of named arguments representing the parameters of the entity, and have the model infer what type of object is being described by the inbound parameters (from the names of the parameters and potentially the sequence they occur in) and call a factory method on the appropriate derived class. For example, if I pass the model a pair of parameters (Param1=5000, Param2="Bacon") I would like it to infer that the names Param1 and Param2 'belong' to the class "Blob1" and call a shared function "getBlob1" with named parameters Param1:=5000, Param2:="Bacon" whereas if I pass the model (Param1=5000, Param3=50) it would call a similar factory method for Blob2; because Param1 and Param3 in that order 'belong' to Blob2. I foresee several issues to resolve: Whether or not I can reflect on the available types with string parameter names and how to do this if it's possible Whether or not there's a neat way of doing the appropriate constructor inference from the combinatoric properties of the argument list or whether I'm going to have to bodge something to do it 'by hand'. If possible I'd like the model class to be able to accept parameters as parameters rather than as some collection of keys and values, which would require the model to expose a large number of parametrised methods at runtime without me having to code them explicitly - presumably one for every factory method available in the relevant namespace. What I'm really asking is how you'd go about implementing such a system, rather than whether or not it's fundamentally possible. I don't have the foresight or experience with .NET reflection to be able to figure out a way by myself. Hopefully this will prove an informative discussion.

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• OO Design: use Properties or Overloaded methods?

  - by Robert Frank

  Question about OO design. Suppose I have a base object vehicle. And two descendants: truck and automobile. Further, suppose the base object has a base method: FixFlatTire(); abstract; When the truck and automobile override the base object's, they require different information from the caller. Am I better off overloading FixFlatTire like this in the two descendant objects: Procedure Truck.FixFlatTire( OfficePhoneNumber: String; NumberOfAxles: Integer): Override; Overload; Procedure Automobile.FixFlatTire( WifesPhoneNumber: String; AAAMembershipID: String): Override; Overload; Or introducing new properties in each of the descendants and then setting them before calling FixFlatTire, like this: Truck.OfficePhoneNumber := '555-555-1212'; Truck.NumberOfAxles := 18; Truck.FixFlatTire(); Automobile.WifesPhoneNumber := '555-555-2323'; Automobile.AAAMembershipID := 'ABC'; Automobile.FixFlatTire();

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• Winforms App Not Displaying Graphical Elements in Design Mode

  - by Sev

  I wrote a bunch of code in the .cs file in c# for a winforms application. The application runs fine, and everything is in it's place. Something like this: using.. namespace Temp { public class Temp : Form { Button b1; TextBox t1; Temp() { b1.Text = "Some Text"; b1.Size = new Size(50,20); ... } void function1() { // stuff } static void Main() { Application.Run(new Temp()); } } } How can I modify my code (or fix it somehow) so that the design view displays the elements in their correct positions and view so that I can visually edit them instead of having to trial/error everything. Edit for Clarification My application runs fine. The problem is, that I didn't use designer to create the application and so in the designer view, the app is empty. But not empty when I run it, since everything is positioned programmatically in the .cs file. My question is, how can I fix this, so that the designer shows the objects correctly. There is no quick fix other than to redesign everything?

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• Visual C# Winforms App Not Displaying Graphical Elements in Design Mode

  - by Sev

  I wrote a bunch of code in the .cs file in c# for a winforms application. The application runs fine, and everything is in it's place. Something like this: using.. namespace Temp { public class Temp : Form { Button b1; TextBox t1; Temp() { b1.Text = "Some Text"; b1.Size = new Size(50,20); ... } void function1() { // stuff } static void Main() { Application.Run(new Temp()); } } } How can I modify my code (or fix it somehow) so that the design view displays the elements in their correct positions and view so that I can visually edit them instead of having to trial/error everything. Edit for Clarification My application runs fine. The problem is, that I didn't use designer to create the application and so in the designer view, the app is empty. But not empty when I run it, since everything is positioned programmatically in the .cs file. My question is, how can I fix this, so that the designer shows the objects correctly. There is no quick fix other than to redesign everything?

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• Design patterns for Caching Images in a MVC?

  - by Onema

  Hi, I'm designing an image cache system that will be used in an MVC CMS. The main purpose of the image cacher is to modify images: scale, crop, etc and cache them in the client site. I have created an image cache Model and Mapper that interact with the Database, to keep track of the images and know what kind of actions have been applied to them (scale, crop, etc). In addition to the Model and Mapper I have created a ImageCacher Class that is used by the API to manage the Model and image creation based on arguments passed by the client site, this class creates the images and generates the links to the images for the View. A coworker argued that I need to include the functionality of this last Class inside the Model, as the bulk of the logic should go in the model. I respectfully disagree with him since I feel the model's responsibility is to deal with the information about the images cached at the database level, and the responsibility of the ImageCacher Class is to create the url/image that we will be caching (keeping the single responsibility principle). In addition to this I believe that a model should not have Presentation-related features, like creating or showing images. Does anyone have any insight on this? is there a particular design pattern that would make this division of tasks clear and and the image cacher reusable? Should I add all the logic in the Model? Thank you.

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• Grid related UI design question

  - by younevertell

  Grid related UI design question I want some 16-grid (4 rows and 4 columns) user interface, and fill the grid with some round shapes. I also want to use the MouseOver, mouse left button down, and Mouse Left Button Up events to set the state of grids as selected or not selected. My questions: 1. How fill the grid with some round shapes? by SetColumn and SetRow? 2. How to make the grids respond to the mouse please? Thanks <Grid.ColumnDefinitions> <ColumnDefinition /> <ColumnDefinition /> <ColumnDefinition /> <ColumnDefinition /> </Grid.ColumnDefinitions> <Grid.RowDefinitions> <RowDefinition /> <RowDefinition /> <RowDefinition /> <RowDefinition /> </Grid.RowDefinitions>

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• MS Access Premiere Products Exercise

  - by rynwtts

  I am working with Microsoft Access, Premiere Products Exercises for a college course. I can't seem to get past a specific question. We are working with DBDL and E-R Diagrams. The question is here. Indicate the changes you need to make to the design of the Premiere Products database to support the following situation. A customer is not necessarily represented by a single sales rep but can be represented by several sales reps. when a customer places an order, the sales rep who gets the commission on the order must be one of the collection of sales reps who represents the customer. In the database already each customer is represented by a sales rep. Which yields a one to one relationship. I need to enable a customer to have several sales reps, and make it so that only those sales rep will be eligible for commission upon each order.

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• Why my computer working without harddisc with livecd, but with hardisk not working - computer not response to any signals?

  - by Yosef

  Hi, History of problem: I formated computer (HP Pavalion Desktop). When I restart computer - computer come to first screen before boot and not response to any signals (f2, f10, ESC, etc..) I take out motherboad battery return after time back and power computer - result : as before I disconnect wires of hard-disk and insert livecd UBUNTU to cd and power coputer: result: works without hard-disk. What is the root of problem: hard-disk broken? hard-disk wires not working well? BIOS? other reason How can I fix the problem?(Buy new hard disk etc...) Thanks, Yosef

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• CPU and Motherboard clock speeds

  - by NZHammer

  I have been doing some reading about CPU clock speeds and how CPU clock speeds are calculated. After reading several articles, I have come to the understanding that your CPU clock speed is determined by: CPU clock speed = cpu multiplier x mobo clock speed A few questions came about after reading this which I cannot seem to find the answer to anywhere: If the CPU clock speed is dependent upon the mobo clock speed, then how is the clock speed of the CPU predetermined upon buying the CPU (i.e. written on the box without knowing what mobo is being used)? After installation, does the CPU adjust it's multiplier based upon the mobo clock speed to achieve advertised speeds? For example, if the CPU clocks speed is advertised at 2.4GHz and the mobo clock speed is 100MHz, will the multiplier be automatically set to 24x? Why does mobo clock speed seem to not be very important / talked about? For example, when I search on Newegg, mobo clock speed never seems to be listed. When I search enthusiast forums and overclocking forums, mobo clock speed is rarely mentioned. To me, it seems like the mobo clock speed would be pretty important. If I am understanding things correctly, a lower mobo clock speed means that you CPU must work harder to achieve advertised clock speeds. I guess that I should stop there with the questions for now, as I may be asking my questions based on incorrect assumptions. Thanks!

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• Bash can't start a programme that's there and has all the right permissions

  - by Rory

  This is a gentoo server. There's a programme prog that can't execute. (Yes the execute permission is set) About the file $ ls prog $ ./prog bash: ./prog: No such file or directory $ file prog prog: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), for GNU/Linux 2.2.5, dynamically linked (uses shared libs), not stripped $ pwd /usr/local/bin $ /usr/local/bin/prog bash: /usr/local/bin/prog: No such file or directory $ less prog | head ELF Header: Magic: 7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00 Class: ELF32 Data: 2's complement, little endian Version: 1 (current) OS/ABI: UNIX - System V ABI Version: 0 Type: EXEC (Executable file) Machine: Intel 80386 Version: 0x1 I have a fancy less, to show that it's an actual executable, here's some more data: $ xxd prog |head 0000000: 7f45 4c46 0101 0100 0000 0000 0000 0000 .ELF............ 0000010: 0200 0300 0100 0000 c092 0408 3400 0000 ............4... 0000020: 0401 0a00 0000 0000 3400 2000 0700 2800 ........4. ...(. 0000030: 2600 2300 0600 0000 3400 0000 3480 0408 &.#.....4...4... 0000040: 3480 0408 e000 0000 e000 0000 0500 0000 4............... 0000050: 0400 0000 0300 0000 1401 0000 1481 0408 ................ 0000060: 1481 0408 1300 0000 1300 0000 0400 0000 ................ 0000070: 0100 0000 0100 0000 0000 0000 0080 0408 ................ 0000080: 0080 0408 21f1 0500 21f1 0500 0500 0000 ....!...!....... 0000090: 0010 0000 0100 0000 40f1 0500 4081 0a08 ........@...@... and $ ls -l prog -rwxrwxr-x 1 1000 devs 725706 Aug 6 2007 prog $ ldd prog not a dynamic executable $ strace ./prog 1249403877.639076 execve("./prog", ["./prog"], [/* 27 vars */]) = -1 ENOENT (No such file or directory) 1249403877.640645 dup(2) = 3 1249403877.640875 fcntl(3, F_GETFL) = 0x8002 (flags O_RDWR|O_LARGEFILE) 1249403877.641143 fstat(3, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 0), ...}) = 0 1249403877.641484 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2b3b8954a000 1249403877.641747 lseek(3, 0, SEEK_CUR) = -1 ESPIPE (Illegal seek) 1249403877.642045 write(3, "strace: exec: No such file or dir"..., 40strace: exec: No such file or directory ) = 40 1249403877.642324 close(3) = 0 1249403877.642531 munmap(0x2b3b8954a000, 4096) = 0 1249403877.642735 exit_group(1) = ? About the server FTR the server is a xen domU, and the programme is a closed source linux application. This VM is a copy of another VM that has the same root filesystem (including this programme), that works fine. I've tried all the above as root and same problem. Did I mention the root filesystem is mounted over NFS. However it's mounted 'defaults,nosuid', which should include execute. Also I am able to run many other programmes from that mounted drive /proc/cpuinfo: processor : 0 vendor_id : GenuineIntel cpu family : 15 model : 4 model name : Intel(R) Xeon(TM) CPU 3.00GHz stepping : 1 cpu MHz : 2992.692 cache size : 1024 KB fpu : yes fpu_exception : yes cpuid level : 5 wp : yes flags : fpu tsc msr pae mce cx8 apic mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm constant_tsc pni monitor ds_cpl cid cx16 xtpr bogmips : 5989.55 clflush size : 64 cache_alignment : 128 address sizes : 36 bits physical, 48 bits virtual power management: Example of a file that I can run I can run other programmes on that mounted filesystem on that server. For example: $ ls -l ls -rwxr-xr-x 1 root root 105576 Jul 25 17:14 ls $ file ls ls: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), for GNU/Linux 2.6.9, dynamically linked (uses shared libs), stripped $ ./ls attr cat cut echo getfacl ln more ... (you get the idea) ... rmdir sort tty $ less ls | head ELF Header: Magic: 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00 Class: ELF64 Data: 2's complement, little endian Version: 1 (current) OS/ABI: UNIX - System V ABI Version: 0 Type: EXEC (Executable file) Machine: Advanced Micro Devices X86-64 Version: 0x1

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• 32bit vs 64bit guest VM and RAM usage

  - by sims

  Why does a 32bit domU (Xen guest VM) use less RAM than a 64bit? Notes: The same software complied for a different arch(AMD64 vs. 686). Obviously this is Linux or BSD or something easily ported. Maybe this is also a good one for SO. I've read this is so. I can guess why, but I'd like to hear everyone's comments.

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