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• Large, high performance object or key/value store for HTTP serving on Linux

  - by Tommy

  I have a service that serves images to end users at a very high rate using plain HTTP. The images vary between 4 and 64kbytes, and there are 1.300.000.000 of them in total. The dataset is about 30TiB in size and changes (new objects, updates, deletes) make out less than 1% of the requests. The number of requests pr. second vary from 240 to 9000 and is dispersed pretty much all over, with few objects being especially "hot". As of now, these images are files on a ext3 filesystem distributed read only across a large amount of mid range servers. This poses several problems: Using a fileysystem is very inefficient since the metadata size is large, the inode/dentry cache is volatile on linux and some daemons tend to stat()/readdir() it's way through the directory structure, which in my case becomes very expensive. Updating the dataset is very time consuming and requires remounting between set A and B. The only reasonable handling is operating on the block device for backup, copying, etc. What I would like is a deamon that: speaks HTTP (get, put, delete and perhaps update) stores data it in an efficient structure. The index should remain in memory, and considering the amount of objects, the overhead must be small. The software should be able to handle massive connections with slow (if any) time needed to ramp up. Index should be read in memory at startup. Statistics would be nice, but not mandatory. I have experimented a bit with riak, redis, mongodb, kyoto and varnish with persistent storage, but I haven't had the chance to dig in really deep yet.

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• GMail Phone dialer - shortcut key for pushing the hash or pound key?

  - by Brian

  I use the GMall 'Call phone' feature a lot, and the numeric keyboard pad works great for entering conference codes, but most conference call services want you "Enter your conference code followed by the 'hash' or 'pound' sign. So I end up typing the 10 digit conference code using the keyboard but then I have to use my mouse to push the # or hash sign. Is their a way to push the # with the keyboard?

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• Standard F* keys need holding Fn key on Compaq CQ62

  - by Chandru

  I got a Compaq CQ62 laptop recently. I find that I have to hold down the Fn keys to use the standard F* keys while accessing the special functionalities like media keys does not. This is frustrating as the standard keys are used more often the special functions. Is there anyway to fix it so that it behaves like other sane laptops out there? I use Ubuntu Lucid, but this behavior is present on laptops running Windows 7 too.

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• Emacs eshell over SSH not obeying key commands or elisp

  - by Brad Wright

  When SSHing to a remote server Eshell doesn't behave very well, e.g: M-x eshell ssh server <tab> *inserts literal tab instead of trying to complete* Hitting <tab>, for instance, inserts a literal tab. Is there no way to get tab completion, lisp interaction (like find-file blah) etc. over SSH? All the documentation I've read says Eshell is "TRAMP-aware", which I assume meant it could deal with this. Am I just wrong in my assumption that it would work over SSH, or is something broken? This is on Emacs 24.0.94 pretest.

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• ctrl-v key on AIX

  - by antenore

  Hi all, I'm new to AIX and I miss some tricks that work well on other *nix flavors. I need a CTRL sequence in a ksh scripts, like ^[ (CTRL-[) and to do that I'm habit to use the ctrl-v[ , but here it doesn't work. At the moment I'm obliged to use a windows box with putty so I cannot even edit the scripts on my Linux box and transfer the scripts on the AIX server. Do you know why and how I can fix the issue? Thanks in advance Kind regards Antenore.

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• vim: sending tab-completion key against a mapped keystroke

  - by CDR

  To switch between buffers without installing any plugins, a good way is to type :b <tab> Which shows all the current buffers names in status bar and you can pick one using cursor keys and enter. But :b <tab> is 5 keystrokes and I would like to map it to a <leader>. But setting the following is not working. :nnoremap <Leader>. :b <Tab> It shows ":b ^I" in status bar and doesn't actually open the buffer names on status bar. Anyone knows why?

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• How to record screencast on Linux with mouse clicks and key hits shown

  - by zalun

  Basically I'm looking for an application to record a series of tutorials for a program I wrote. It's important to show the actions like mouse click, mouse right click, and all what's coming out from the keyboard. In the similar way to this video http://www.flickr.com/photos/jannis/3246408003/ which is made using OSX and ScreenFlick www.araelium.com/screenflick/ Is there such an option? Thanks

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• Key to mute my Skype mic?

  - by lo_fye

  I'm using a Mac. Is there a keyboard shortcut for muting the mic during a call? I can't find one, and I often need to toggle mute/unmute. Clicking the button on the Skype interface is very inconvenient :(

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• Tool to run same key strokes on multiple unix machines

  - by virtualvoid

  I want to run the same commands on multiple machines, I know I can do this using ssh scripting or things like clusterssh, however I don't want to install anything on the server. (Don't have the rights) What I want is to just clone the keystrokes across multiple machines e.g. run cat /etc/oratab on one window and same is run on multiple windows e.g. in putty, is there a tool to do that from a windows client.

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• Prevent Virtualbox intercepting certain key combinations?

  - by Blazemore

  Is it possible to prevent my Windows 7 guest OS intercepting Ctrl+Up/Down, and allow my Ubuntu how to intercept them instead? I have a dual-monitor setup with two vertical virtual desktops on Ubuntu. I have a Windows 7 fullscreen guest on one monitor, set to always display on the current workspace. This means I have effectively two vertical workspaces on one monitor, and just Windows 7 on the other. The problem occurs with Windows 7 is focussed and I hit Ctrl+Up/Down to switch workspaces. I have to click out of the VM first, which breaks my workflow. Can this be fixed?

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• Remotely enter encryption key?

  - by Jason Swett

  This might be a really dumb question but here goes, anyway. I just bought a couple servers. I already installed Ubuntu with encrypted LVM on one and I'm planning on doing the same with the other. This means that every time I boot up each of these machines, I have to enter the passphrase. And I'll have to do this every morning because I'll power each machine off each night for security reasons. Here's the problem: I don't have monitors or keyboards for these servers. It seems to me I have two options: Somehow enter the passphrase remotely Buy a KVM switch I doubt #1 is an option but I want to make sure it's not before I buy a KVM. Is it possible to enter the passphrase remotely? AND is it a good idea?

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• Control Key for Home & End on Command Line in Terminal on Mac OS X

  - by ydfeed

  What are the control keys to move the cursor to the beginning and end of the command line? The Home and End keys don't work in Terminal on Mac OS X.

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• Discover intended Foreign Keys from JOINS in scripts

  - by Jason

  I'm inheriting a database that has 400 tables and only 150 foreign key constraints registered. Knowing what I do about the application and looking at the table columns, it's easy to say that there ought to be a lot more. I'm afraid that the current application software will break if I started adding the missing FKs because the developers have probably come to rely on this "freedom", but step one in fixing the problem is to come up with the list of missing FKs so we can evaluate them as a team. To make matters worse, the referencing columns don't share a naming convention. The relationships ARE coded informally into the hundreds of ad-hoc queries and stored procedures, so my hope is to parse these files programmatically looking for JOINS between actual tables (but not table variables, etc). Challenges I foresee in this approach are: newlines, optional aliases and table hints, alias resolution. Any better ideas? (Besides quitting) Are there any pre-built tools that can solve this? I don't think regex can handle this. Do you disagree? SQL Parsers? I tried using Microsoft.SqlServer.Management.SqlParser.Parser but all that is exposed is the lexer - can't get an AST out of it - all that stuff is internal.

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• Server Design Enquiry [closed]

  - by Brandon Gelfand

  I am really new to this and am having trouble with how I can store information from a website. I am going to be making a site similar to dropbox for my company and there is gonna be around 40 TB of space that we need to be able to access on the go, for instance pull the file up on the phone or off our laptop using the internet. Obviously using an Amazon S3 server is not the most cost effective way of doing this so how can I make my own server to hold all of the info and communicate to it from a website? Please I need as much help as possible, like a blueprint or something. Thanks and sorry for the noobish question but I can't really find an exact answer to my question.

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• Ajax, Lizard Brain Web Design, JSF, Struts, JavaScript, Mobile Web, Flash, jQuery, GWT, Harmony at I

  - by Kim Won

  Great Indian Developer Summit 2010 – India's Biggest Polyglot Conference and Workshops for IT Software Professionals Bangalore, April 9, 2010: The GIDS.Web Conference and Workshops has announced the complete program of over 30 sessions on how browser and rich web technologies such as AJAX, DHTML, Mashups, Web 2.0, Enterprise 2.0 technologies, and Rich UI technologies are making money and gaining market-share for some of the leading businesses in the world. The GIDS.Web track at Great Indian Developer Summit takes place 21 and 23 April 2010, at the Indian Institute of Science in Bangalore. As one of the longest running independent developer conferences in India, GIDS.Web at the Great Indian Developer Summit 2010 is uniquely positioned to provide a blend of practical, pragmatic and immediately applicable knowledge and a glimpse of the future of technology. During 21 and 23 April 2010, GIDS.Web offers a multi-track conference, workshops, expo show floor, and networking opportunities. The first keynote at GIDS.Web is led by the leading Java EE and Ajax developer, speaker, and author Marty Hall. The best of India's Java and RIA programmers have learnt the subject from Marty's seminal books Core Servlets and JavaServer Pages (first and second editions), More Servlets and JavaServer Pages, and Core Web Programming (first and second editions) from Prentice Hall and Sun Microsystems Press. Marty's keynote address is a comparison of approaches to building rich Internet applications with Ajax. Marty says Ajax development is difficult, and there are several fundamentally different strategies to building Ajaxified Web applications. The keynote address will survey the three most important of these approaches: using an Ajax-enabled JavaScript library such as jQuery, Prototype, Scriptaculous, Dojo, or Ext/JS; using a Web framework such as JSF 2.0 or Struts 2 that has integrated Ajax support; using the Google Web Toolkit (GWT) to build "pure Java" Ajax applications. The talk will compare and contrast these three approaches, discussing the types of applications that fit best for each option. Over the course of the summit Marty will conduct several more sessions on "Choosing an Ajax/JavaScript Toolkit: A Comparison of the Most Popular JavaScript Libraries", "Pure Java Ajax: An Overview of GWT 2.0", "Integrated Ajax Support in JSF 2.0" and "Ajax Support in the Prototype JavaScript Library". The second keynote by the head of Adobe's Flash initiative in India, Ramesh Srinivasaraghavan, explores the state of art in web application development and identify trends that could transform the way we create and use web applications. The talk explains how the Adobe Flash Platform has fuelled this revolution with an integrated set of technologies for delivering the most compelling applications, content and video to the widest possible audience. The Director of Forum Nokia will explain how cloud computing coupled with mobile applications enable consumers to have access to powerful services and improved user experiences never before thought possible. IEEE's 2010 President-Elect Sorel Reisman's afternoon address steps to improve the IT profession in India. Featured talks at GID.Web also include: Web 2.0 Checklist - Deconstructing Modern Websites, Scott Davis Choosing an Ajax/JavaScript Toolkit: Comparison of Popular JavaScript Libraries, Marty Hall Lizard Brain Web Design, Scott Davis Effective Design Processes and Resources for Mobile Web Development, Arabella David NoSQL: The Shift to a Non-relational World, Nosh Petigara Open Source Web Debugging Tools, Matthew McCullough Building Line of Business Applications with Silverlight 4.0, Stephen Forte Hadoop - Divide and Conquer, Matthew McCullough Adobe Flash Catalyst for Agile Interaction Design, Harish Sivaramakrishnan Using jQuery and AJAX to Build Front-ends for ASP.NET and ASP.NET MVC, Pandurang Nayak First Steps to IT Heaven Through the Cloud. Part II: .WEB, Simone Brunozzi Building Rich Internet Applications with SL RIA Web Services, Pandurang Nayak Enriching Cloud Applications with Adobe Flash Platform, Ramesh Srinivasaraghavan Payments for the Web.future, Khurram Khan and Praveen Alavilli Longevity of Scalable Systems, Nishad Kamat Transform yourself into a Mobile App Developer Using Web Run Time, Balagopal K S Developing Multi Screen Applications on Adobe Flash Platform, Hemanth Sharma Why Harmony and For Whom?, Himanshu Goyal IIS Hosting Solution for ASP.net and PHP Web Sites, Nahas Mohammed Building Pluggable Web applications using Django, Lakshman Prasad Workshop: The 180-min AJAX and JSON Spike Class, Scott Davis Workshop: Essence of Functional Programming, Venkat Subramaniam Workshop: Agile Development, Tools, and Teams and Scrum Certification, Stephen Forte Workshop: PHP + Adobe Flex = Killer RIA, Shyamprasad P Workshop: Cloud Computing Boot Camp on the Google App Engine, Matthew McCullough Workshop: Building Data Centric Applications using Adobe Flex and Java, Prashant Singh Workshop: Building Your First Amazon App, Simone Brunozzi Workshop: Windows Azure Deep Dive, Ramaprasanna Chellamuthu Workshop: Monetizing your Apps with PayPal X Payments Platform, Khurram Khan, Praveen Alavilli Workshop: User Expereince Evaluation Model Walkthrough, Sanna Häiväläinen Sponsors of Great Indian Developer Summit 2010 include: Platinum sponsors Microsoft, Oracle Forum Nokia and Adobe; Gold sponsors Intel and SAP; Silver sponsors Quest Software, PayPal, Telerik and AMT. About Great Indian Developer Summit Great Indian Developer Summit is the gold standard for India's software developer ecosystem for gaining exposure to and evaluating new projects, tools, services, platforms, languages, software and standards. Packed with premium knowledge, action plans and advise from been-there-done-it veterans, creators, and visionaries, the 2010 edition of Great Indian Developer Summit features focused sessions, case studies, workshops and power panels that will transform you into a force to reckon with. Featuring 3 co-located conferences: GIDS.NET, GIDS.Web, GIDS.Java and an exclusive day of in-depth tutorials - GIDS.Workshops, from 20 April to 24 April at the IISc campus in Bangalore. At GIDS you'll participate in hundreds of sessions encompassing the full range of Microsoft computing, Java, Agile, RIA, Rich Web, open source/standards, languages, frameworks and platforms, practical tutorials that deep dive into technical skill and best practices, inspirational keynote presentations, an Expo Hall featuring dozens of the latest projects and products activities, engaging networking events, and the interact with the best and brightest of speakers from around the world. For further information on GIDS 2010, please visit the summit on the web http://www.developersummit.com/ A Saltmarch Media Press Release E: [email protected] Ph: +91 80 4005 1000

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• Who architected / designed C++'s IOStreams, and would it still be considered well-designed by today'

  - by stakx

  First off, it may seem that I'm asking for subjective opinions, but that's not what I'm after. I'd love to hear some well-grounded arguments on this topic. In the hope of getting some insight into how a modern streams / serialization framework ought to be designed, I recently got myself a copy of the book Standard C++ IOStreams and Locales by Angelika Langer and Klaus Kreft. I figured that if IOStreams wasn't well-designed, it wouldn't have made it into the C++ standard library in the first place. After having read various parts of this book, I am starting to have doubts if IOStreams can compare to e.g. the STL from an overall architectural point-of-view. Read e.g. this interview with Alexander Stepanov (the STL's "inventor") to learn about some design decisions that went into the STL. What surprises me in particular: It seems to be unknown who was responsible for IOStreams' overall design (I'd love to read some background information about this — does anyone know good resources?); Once you delve beneath the immediate surface of IOStreams, e.g. if you want to extend IOStreams with your own classes, you get to an interface with fairly cryptic and confusing member function names, e.g. getloc/imbue, uflow/underflow, snextc/sbumpc/sgetc/sgetn, pbase/pptr/epptr (and there's probably even worse examples). This makes it so much harder to understand the overall design and how the single parts co-operate. Even the book I mentioned above doesn't help that much (IMHO). Thus my question: If you had to judge by today's software engineering standards (if there actually is any general agreement on these), would C++'s IOStreams still be considered well-designed? (I wouldn't want to improve my software design skills from something that's generally considered outdated.)

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• How much detail should be in a project plan or spec?

  - by DeanMc

  I have an issue that I feel many programmers can relate to... I have worked on many small scale projects. After my initial paper brain storm I tend to start coding. What I come up with is usually a rough working model of the actual application. I design in a disconnected fashion so I am talking about underlying code libraries, user interfaces are the last thing as the library usually dictates what is needed in the UI. As my projects get bigger I worry that so should my "spec" or design document. The above paragraph, from my investigations, is echoed all across the internet in one fashion or another. When a UI is concerned there is a bit more information but it is UI specific and does not relate to code libraries. What I am beginning to realise is that maybe code is code is code. It seems from my extensive research that there is no 1:1 mapping between a design document and the code. When I need to research a topic I dump information into OneNote and from there I prioritise features into versions and then into related chunks so that development runs in a fairly linear fashion, my tasks tend to look like so: Implement Binary File Reader Implement Binary File Writer Create Object to encapsulate Data for expression to the caller Now any programmer worth his salt is aware that between those three to do items could be a potential wall of code that could expand out to multiple files. I have tried to map the complete code process for each task but I simply don't think it can be done effectively. By the time one mangles pseudo code it is essentially code anyway so the time investment is negated. So my question is this: Am I right in assuming that the best documentation is the code itself. We are all in agreement that a high level overview is needed. How high should this be? Do you design to statement, class or concept level? What works for you?

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• How to redirect page

  - by sharun

  Hi i created one java application in which i tried to open my company's standard login page and i planned to redirect the link to open my own design page. Standard login page is displayed, instead of going to my own design page as usual its going to mail page. After sign out the mail page i'm gettting my own design page. But my need is, when i sign in the standard login page it should diplay my own design page. Is it possible? Please Help me. And this is code that i followed import java.io.IOException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import com.google.appengine.api.users.UserService; import com.google.appengine.api.users.UserServiceFactory; import com.google.appengine.api.users.User; public class New extends HttpServlet { /** * */ private static final long serialVersionUID = 1L; public void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException { resp.setHeader("Cache-Control", "no-store, no-cache, must-revalidate"); resp.setContentType("text/html"); UserService userService = UserServiceFactory.getUserService(); User user = userService.getCurrentUser(); if (user != null) { if(user.getEmail().equals("[email protected]")) { resp.getWriter().println("done"); resp.sendRedirect("/login.jsp"); } else { resp.getWriter().println("Hello, " + user.getNickname()+"<br>"); resp.getWriter().println("Thanks for your interest. But this application is still not available to everybody."); resp.getWriter().println("<a href="+UserServiceFactory.getUserService().createLogoutURL(userService.createLoginURL(req.getRequestURI()))+">Log out</a>"); } } else { resp.sendRedirect(userService.createLoginURL("http://mail.yyy.edu.in")); } } } Thanks in advance Regards Sharun.

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• On the search for my next great .Net Read

  - by user127954

  Just got done with "The art of unit testing". It was a great read and i think everyone should go buy a copy. With that said i think the next book I'm like to read would be a architecture / Design type book that would focus heavily on building your objects / software in such a way that it would be: Low Coupling High Cohesion Easily Maintainable / Extended Easy to test Easy to Navigate / Debug The above characteristcs are the most important ones but also maybe it would also include (but not necessary) designing for: Performance - Don't want to design a system at at the end find out its dog slow :) Scalability - Again don't want to design something at the end find out it won't scale. I'd also prefer (but not necessary again): Something newer - Architectural principles seem to gradually evolve / improve over time and id like something with current thinking. .Net as illustrating language - like i said above its not mandatory but since its what i use every day id prefer it to be in .net. Doesn't really matter if its in vb.net or c# Some of the topics that would be talked about its how to minimize dependencies and using interfaces throughout your solution rather than concrete classes. Maybe it would constract /compare some of the newest design principles like DDD, Repository Pattern, Ect... I already have "Clean Code" (don't know if its this type of book or not) and "Working effectively with legacy code" on my radar but id like to read a book based upon the topic i talked about above first. Is there such a book?

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• Pre Project Documentation

  - by DeanMc

  I have an issue that I feel many programmers can relate to... I have worked on many small scale projects. After my initial paper brain storm I tend to start coding. What I come up with is usually a rough working model of the actual application. I design in a disconnected fashion so I am talking about underlying code libraries, user interfaces are the last thing as the library usually dictates what is needed in the UI. As my projects get bigger I worry that so should my "spec" or design document. The above paragraph, from my investigations, is echoed all across the internet in one fashion or another. When a UI is concerned there is a bit more information but it is UI specific and does not relate to code libraries. What I am beginning to realise is that maybe code is code is code. It seems from my extensive research that there is no 1:1 mapping between a design document and the code. When I need to research a topic I dump information into OneNote and from there I prioritise features into versions and then into related chunks so that development runs in a fairly linear fashion, my tasks tend to look like so: Implement Binary File Reader Implement Binary File Writer Create Object to encapsulate Data for expression to the caller Now any programmer worth his salt is aware that between those three to do items could be a potential wall of code that could expand out to multiple files. I have tried to map the complete code process for each task but I simply don't think it can be done effectively. By the time one mangles pseudo code it is essentially code anyway so the time investment is negated. So my question is this: Am I right in assuming that the best documentation is the code itself. We are all in agreement that a high level overview is needed. How high should this be? Do you design to statement, class or concept level? What works for you?

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• Tender vs. Requirements vs. Solution Design

  - by Tom Tom

  Conventionally, which of the above documents is deemed to hold the most weight when it comes to system acceptance? I recently had a conversation along these lines: It was argued that the initial requirements / tender documentation should be used to determine system acceptance. It was said that the solution design only serves to describe the way in which the system will solve the problem, not the problem it will solve. Furthermore, it was argued that if requirements are missed during solution design, the requirements should be referenced during system acceptance and that if any requirements were missed then the original tender should be referenced. Conversely, I suggested that - while requirements may be based on the original tender - they supersede it once agreed with the stakeholders. Furthermore, during solution design, analysis is performed to address and refine these initial requirements, translating them into a system capable of meeting the actual requirements. Once signed off by the relevant users, this solution design should absolutely represent the requirements (by virtue of the fact that it's designed upon them) but actually supersedes them as the basis for system acceptance. Is one of the above arguments more valid than the other?

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• Setting up Cluster Configuration using an existing web server as a Primary Node?

  - by RapidWebs

  Thanks in advance for any help which is issued! I am having a slight issue, and need help with the decision making process when it comes to setting up my Cluster Configuration, consisting on a line of Ubuntu Servers (12.04). We currently have a Primary node, which resides in the US within a Datacenter, but we are going to be using this for all serious bandwidth and resource intensive websites, and through a configuration of Virtualmin + Webmin, will be setup as a sort of pseudo-cluster, using Virtualmins Cluster Modules. Anyways, on to the issue: We also have a business line setup locally, with three servers. here are their specs: Intel P4 2.4 ghz, 1GB Ram, 110 gb sata, Ubuntu 12.04* AMD 1.3 ghz, 512MB Ram, 20 GB IDE P3 Xeon 800mhz (dual physical processors), 1GB Ram, 3 * 25 GB Raid Configuration (one in use for host operating system). The first machine is currently IN USE and is serving virtual hosts off a sub-domain. My question is this: How can I integrate the Secondary node (which will be the Primary node per say, in this smaller configuration...) which is currently in use, into the cluster configuration w/ the other two servers for: Sharing Resources Redundancy (HA?) NFS /w the two Raid Disks without having the FORMAT the secondary node, and start fresh moving all my services in to a DRBD network drive or something similar, and than restoring all active virtualmin's Virtual hosts. the idea is that I want minimal downtime to people currently being served from server2.mywebsite.com, and from what I understand, all services need to be on a NFS so that they can be mounted on demand and accessed from the other machine taking over (i.e. Heartbeat + DRBD Config.) but my issue is that i already have all these services installed to their default directory structure: how can i most easily setup this NFS and HA system, move all my desires services to this new drive, and do it with minimal down time, and without breaking Virtualmin and everything else on my server? even just some pointers, a thread i could read, or a step by step check list or run down of commands i could issue to get started would be great! thanks!

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• Silverlight 4 + WCF RIA - Data Service Design Best Practices

  - by Chadd Nervig

  Hey all. I realize this is a rather long question, but I'd really appreciate any help from anyone experienced with RIA services. Thanks! I'm working on a Silverlight 4 app that views data from the server. I'm relatively inexperienced with RIA Services, so have been working through the tasks of getting the data I need down to the client, but every new piece I add to the puzzle seems to be more and more problematic. I feel like I'm missing some basic concepts here, and it seems like I'm just 'hacking' pieces on, in time-consuming ways, each one breaking the previous ones as I try to add them. I'd love to get the feedback of developers experienced with RIA services, to figure out the intended way to do what I'm trying to do. Let me lay out what I'm trying to do: First, the data. The source of this data is a variety of sources, primarily created by a shared library which reads data from our database, and exposes it as POCOs (Plain Old CLR Objects). I'm creating my own POCOs to represent the different types of data I need to pass between server and client. DataA - This app is for viewing a certain type of data, lets call DataA, in near-realtime. Every 3 minutes, the client should pull data down from the server, of all the new DataA since the last time it requested data. DataB - Users can view the DataA objects in the app, and may select one of them from the list, which displays additional details about that DataA. I'm bringing these extra details down from the server as DataB. DataC - One of the things that DataB contains is a history of a couple important values over time. I'm calling each data point of this history a DataC object, and each DataB object contains many DataCs. The Data Model - On the server side, I have a single DomainService: [EnableClientAccess] public class MyDomainService : DomainService { public IEnumerable<DataA> GetDataA(DateTime? startDate) { /*Pieces together the DataAs that have been created since startDate, and returns them*/ } public DataB GetDataB(int dataAID) { /*Looks up the extended info for that dataAID, constructs a new DataB with that DataA's data, plus the extended info (with multiple DataCs in a List<DataC> property on the DataB), and returns it*/ } //Not exactly sure why these are here, but I think it //wouldn't compile without them for some reason? The data //is entirely read-only, so I don't need to update. public void UpdateDataA(DataA dataA) { throw new NotSupportedException(); } public void UpdateDataB(DataB dataB) { throw new NotSupportedException(); } } The classes for DataA/B/C look like this: [KnownType(typeof(DataB))] public partial class DataA { [Key] [DataMember] public int DataAID { get; set; } [DataMember] public decimal MyDecimalA { get; set; } [DataMember] public string MyStringA { get; set; } [DataMember] public DataTime MyDateTimeA { get; set; } } public partial class DataB : DataA { [Key] [DataMember] public int DataAID { get; set; } [DataMember] public decimal MyDecimalB { get; set; } [DataMember] public string MyStringB { get; set; } [Include] //I don't know which of these, if any, I need? [Composition] [Association("DataAToC","DataAID","DataAID")] public List<DataC> DataCs { get; set; } } public partial class DataC { [Key] [DataMember] public int DataAID { get; set; } [Key] [DataMember] public DateTime Timestamp { get; set; } [DataMember] public decimal MyHistoricDecimal { get; set; } } I guess a big question I have here is... Should I be using Entities instead of POCOs? Are my classes constructed correctly to be able to pass the data down correctly? Should I be using Invoke methods instead of Query (Get) methods on the DomainService? On the client side, I'm having a number of issues. Surprisingly, one of my biggest ones has been threading. I didn't expect there to be so many threading issues with MyDomainContext. What I've learned is that you only seem to be able to create MyDomainContextObjects on the UI thread, all of the queries you can make are done asynchronously only, and that if you try to fake doing it synchronously by blocking the calling thread until the LoadOperation finishes, you have to do so on a background thread, since it uses the UI thread to make the query. So here's what I've got so far. The app should display a stream of the DataA objects, spreading each 3min chunk of them over the next 3min (so they end up displayed 3min after the occurred, looking like a continuous stream, but only have to be downloaded in 3min bursts). To do this, the main form initializes, creates a private MyDomainContext, and starts up a background worker, which continuously loops in a while(true). On each loop, it checks if it has any DataAs left over to display. If so, it displays that Data, and Thread.Sleep()s until the next DataA is scheduled to be displayed. If it's out of data, it queries for more, using the following methods: public DataA[] GetDataAs(DateTime? startDate) { _loadOperationGetDataACompletion = new AutoResetEvent(false); LoadOperation<DataA> loadOperationGetDataA = null; loadOperationGetDataA = _context.Load(_context.GetDataAQuery(startDate), System.ServiceModel.DomainServices.Client.LoadBehavior.RefreshCurrent, false); loadOperationGetDataA.Completed += new EventHandler(loadOperationGetDataA_Completed); _loadOperationGetDataACompletion.WaitOne(); List<DataA> dataAs = new List<DataA>(); foreach (var dataA in loadOperationGetDataA.Entities) dataAs.Add(dataA); return dataAs.ToArray(); } private static AutoResetEvent _loadOperationGetDataACompletion; private static void loadOperationGetDataA_Completed(object sender, EventArgs e) { _loadOperationGetDataACompletion.Set(); } Seems kind of clunky trying to force it into being synchronous, but since this already is on a background thread, I think this is OK? So far, everything actually works, as much of a hack as it seems like it may be. It's important to note that if I try to run that code on the UI thread, it locks, because it waits on the WaitOne() forever, locking the thread, so it can't make the Load request to the server. So once the data is displayed, users can click on one as it goes by to fill a details pane with the full DataB data about that object. To do that, I have the the details pane user control subscribing to a selection event I have setup, which gets fired when the selection changes (on the UI thread). I use a similar technique there, to get the DataB object: void SelectionService_SelectedDataAChanged(object sender, EventArgs e) { DataA dataA = /*Get the selected DataA*/; MyDomainContext context = new MyDomainContext(); var loadOperationGetDataB = context.Load(context.GetDataBQuery(dataA.DataAID), System.ServiceModel.DomainServices.Client.LoadBehavior.RefreshCurrent, false); loadOperationGetDataB.Completed += new EventHandler(loadOperationGetDataB_Completed); } private void loadOperationGetDataB_Completed(object sender, EventArgs e) { this.DataContext = ((LoadOperation<DataB>)sender).Entities.SingleOrDefault(); } Again, it seems kinda hacky, but it works... except on the DataB that it loads, the DataCs list is empty. I've tried all kinds of things there, and I don't see what I'm doing wrong to allow the DataCs to come down with the DataB. I'm about ready to make a 3rd query for the DataCs, but that's screaming even more hackiness to me. It really feels like I'm fighting against the grain here, like I'm doing this in an entirely unintended way. If anyone could offer any assistance, and point out what I'm doing wrong here, I'd very much appreciate it! Thanks!

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• slow mysql count because of subselect

  - by frgt10

  how to make this select statement more faster? the first left join with the subselect is making it slower... mysql> SELECT COUNT(DISTINCT w1.id) AS AMOUNT FROM tblWerbemittel w1 JOIN tblVorgang v1 ON w1.object_group = v1.werbemittel_id INNER JOIN ( SELECT wmax.object_group, MAX( wmax.object_revision ) wmaxobjrev FROM tblWerbemittel wmax GROUP BY wmax.object_group ) AS wmaxselect ON w1.object_group = wmaxselect.object_group AND w1.object_revision = wmaxselect.wmaxobjrev LEFT JOIN ( SELECT vmax.object_group, MAX( vmax.object_revision ) vmaxobjrev FROM tblVorgang vmax GROUP BY vmax.object_group ) AS vmaxselect ON v1.object_group = vmaxselect.object_group AND v1.object_revision = vmaxselect.vmaxobjrev LEFT JOIN tblWerbemittel_has_tblAngebot wha ON wha.werbemittel_id = w1.object_group LEFT JOIN tblAngebot ta ON ta.id = wha.angebot_id LEFT JOIN tblLieferanten tl ON tl.id = ta.lieferant_id AND wha.zuschlag = (SELECT MAX(zuschlag) FROM tblWerbemittel_has_tblAngebot WHERE werbemittel_id = w1.object_group) WHERE w1.flags =0 AND v1.flags=0; +--------+ | AMOUNT | +--------+ | 1982 | +--------+ 1 row in set (1.30 sec) Some indexes has been already set and as EXPLAIN shows they were used. +----+--------------------+-------------------------------+--------+----------------------------------------+----------------------+---------+-----------------------------------------------+------+----------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+--------------------+-------------------------------+--------+----------------------------------------+----------------------+---------+-----------------------------------------------+------+----------------------------------------------+ | 1 | PRIMARY | <derived2> | ALL | NULL | NULL | NULL | NULL | 2072 | | | 1 | PRIMARY | v1 | ref | werbemittel_group,werbemittel_id_index | werbemittel_group | 4 | wmaxselect.object_group | 2 | Using where | | 1 | PRIMARY | <derived3> | ALL | NULL | NULL | NULL | NULL | 3376 | | | 1 | PRIMARY | w1 | eq_ref | object_revision,or_og_index | object_revision | 8 | wmaxselect.wmaxobjrev,wmaxselect.object_group | 1 | Using where | | 1 | PRIMARY | wha | ref | PRIMARY,werbemittel_id_index | werbemittel_id_index | 4 | dpd.w1.object_group | 1 | | | 1 | PRIMARY | ta | eq_ref | PRIMARY | PRIMARY | 4 | dpd.wha.angebot_id | 1 | | | 1 | PRIMARY | tl | eq_ref | PRIMARY | PRIMARY | 4 | dpd.ta.lieferant_id | 1 | Using index | | 4 | DEPENDENT SUBQUERY | tblWerbemittel_has_tblAngebot | ref | PRIMARY,werbemittel_id_index | werbemittel_id_index | 4 | dpd.w1.object_group | 1 | | | 3 | DERIVED | vmax | index | NULL | object_revision_uq | 8 | NULL | 4668 | Using index; Using temporary; Using filesort | | 2 | DERIVED | wmax | range | NULL | or_og_index | 4 | NULL | 2168 | Using index for group-by | +----+--------------------+-------------------------------+--------+----------------------------------------+----------------------+---------+-----------------------------------------------+------+----------------------------------------------+ 10 rows in set (0.01 sec) The main problem while the statement above takes about 2 seconds seems to be the subselect where no index can be used. How to write the statement even more faster? Thanks for help. MT

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• Why is Mac supposedly better than Windows for graphics?

  - by Svish

  Ok, people just keep telling me that if you're going to be working with graphics and design and stuff, you should get a Mac. And I just don't get the logic. Because most of these people would be working with Adobe software, which are for both Windows and Mac. To me it seems like their whole argument is based on that "everyone else does". Like, Mac had some graphics software that Windows didn't earlier in history, so most people were using Mac. And since most people were using Mac, new people also started using Mac. And since most people were using Mac, schools and universities used Mac. Which taught new people to use Mac. So they were using Mac. And told everyone they met that everyone they knew were using Mac. And so on. Anyways... What is the deal really? Is there actually any advantage in using Mac for graphics and design and such things? My take is that you pretty much have the same software and both Mac and Windows are powerful enough, support enough RAM, are stable (as long as you don't install lot's of junk or faulty drivers), et cetera. So, can anyone give me a good explanation on this? Is there a real difference or are people just brainwashed?

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