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• What Counts for A DBA: Observant

  - by drsql

  When walking up to the building where I work, I can see CCTV cameras placed here and there for monitoring access to the building. We are required to wear authorization badges which could be checked at any time. Do we have enemies?  Of course! No one is 100% safe; even if your life is a fairy tale, there is always a witch with an apple waiting to snack you into a thousand years of slumber (or at least so I recollect from elementary school.) Even Little Bo Peep had to keep a wary lookout.    We nerdy types (or maybe it was just me?) generally learned on the school playground to keep an eye open for unprovoked attack from simpler, but more muscular souls, and take steps to avoid messy confrontations well in advance. After we’d apprehensively negotiated adulthood with varying degrees of success, these skills of watching for danger, and avoiding it,  translated quite well to the technical careers so many of us were destined for. And nowhere else is this talent for watching out for irrational malevolence so appropriate as in a career as a production DBA.   It isn’t always active malevolence that the DBA needs to watch out for, but the even scarier quirks of common humanity.  A large number of the issues that occur in the enterprise happen just randomly or even just one time ever in a spurious manner, like in the case where a person decided to download the entire MSDN library of software, cross join every non-indexed billion row table together, and simultaneously stream the HD feed of 5 different sporting events, making the network access slow while the corporate online sales just started. The decent DBA team, like the going, gets tough under such circumstances. They spring into action, checking all of the sources of active information, observes the issue is no longer happening now, figures that either it wasn’t the database’s fault and that the reboot of the whatever device on the network fixed the problem.  This sort of reactive support is good, and will be the initial reaction of even excellent DBAs, but it is not the end of the story if you really want to know what happened and avoid getting called again when it isn’t even your fault.   When fires start raging within the corporate software forest, the DBA’s instinct is to actively find a way to douse the flames and get back to having no one in the company have any idea who they are.  Even better for them is to find a way of killing a potential problem while the fires are small, long before they can be classified as raging. The observant DBA will have already been monitoring the server environment for months in advance.  Most troubles, such as disk space and security intrusions, can be predicted and dealt with by alerting systems, whereas other trouble can come out of the blue and requires a skill of observing ongoing conditions and noticing inexplicable changes that could signal an emerging problem.  You can’t automate the DBA, because the bankable skill of a DBA is in detecting the early signs of unexpected problems, and working out how to deal with them before anyone else notices them.    To achieve this, the DBA will check the situation as it is currently happening,  and in many cases is likely to have been the person who submitted the problem to the level 1 support person in the first place, just to let the support team know of impending issues (always well received, I tell you what!). Database and host computer settings, configurations, and even critical data might be profiled and captured for later comparisons. He’ll use Monitoring tools, built-in, commercial (Not to be too crassly commercial or anything, but there is one such tool is SQL Monitor) and lots of homebrew monitoring tools to monitor for problems and changes in the server environment.   You will know that you have it right when a support call comes in and you can look at your monitoring tools and quickly respond that “response time is well within the normal range, the query that supports the failing interface works perfectly and has actually only been called 67% as often as normal, so I am more than willing to help diagnose the problem, but it isn’t the database server’s fault and is probably a client or networking slowdown causing the interface to be used less frequently than normal.” And that is the best thing for any DBA to observe…

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• Configuring MySQL Cluster Data Nodes

  - by Mat Keep

  0 0 1 692 3948 Homework 32 9 4631 14.0 Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:Cambria; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin; mso-ansi-language:EN-US;} In my previous blog post, I discussed the enhanced performance and scalability delivered by extensions to the multi-threaded data nodes in MySQL Cluster 7.2. In this post, I’ll share best practices on the configuration of data nodes to achieve optimum performance on the latest generations of multi-core, multi-thread CPU designs. Configuring the Data Nodes The configuration of data node threads can be managed in two ways via the config.ini file: - Simply set MaxNoOfExecutionThreads to the appropriate number of threads to be run in the data node, based on the number of threads presented by the processors used in the host or VM. - Use the new ThreadConfig variable that enables users to configure both the number of each thread type to use and also which CPUs to bind them too. The flexible configuration afforded by the multi-threaded data node enhancements means that it is possible to optimise data nodes to use anything from a single CPU/thread up to a 48 CPU/thread server. Co-locating the MySQL Server with a single data node can fully utilize servers with 64 – 80 CPU/threads. It is also possible to co-locate multiple data nodes per server, but this is now only required for very large servers with 4+ CPU sockets dense multi-core processors. 24 Threads and Beyond! An example of how to make best use of a 24 CPU/thread server box is to configure the following: - 8 ldm threads - 4 tc threads - 3 recv threads - 3 send threads - 1 rep thread for asynchronous replication. Each of those threads should be bound to a CPU. It is possible to bind the main thread (schema management domain) and the IO threads to the same CPU in most installations. In the configuration above, we have bound threads to 20 different CPUs. We should also protect these 20 CPUs from interrupts by using the IRQBALANCE_BANNED_CPUS configuration variable in /etc/sysconfig/irqbalance and setting it to 0x0FFFFF. The reason for doing this is that MySQL Cluster generates a lot of interrupt and OS kernel processing, and so it is recommended to separate activity across CPUs to ensure conflicts with the MySQL Cluster threads are eliminated. When booting a Linux kernel it is also possible to provide an option isolcpus=0-19 in grub.conf. The result is that the Linux scheduler won't use these CPUs for any task. Only by using CPU affinity syscalls can a process be made to run on those CPUs. By using this approach, together with binding MySQL Cluster threads to specific CPUs and banning CPUs IRQ processing on these tasks, a very stable performance environment is created for a MySQL Cluster data node. On a 32 CPU/Thread server: - Increase the number of ldm threads to 12 - Increase tc threads to 6 - Provide 2 more CPUs for the OS and interrupts. - The number of send and receive threads should, in most cases, still be sufficient. On a 40 CPU/Thread server, increase ldm threads to 16, tc threads to 8 and increment send and receive threads to 4. On a 48 CPU/Thread server it is possible to optimize further by using: - 12 tc threads - 2 more CPUs for the OS and interrupts - Avoid using IO threads and main thread on same CPU - Add 1 more receive thread. Summary As both this and the previous post seek to demonstrate, the multi-threaded data node extensions not only serve to increase performance of MySQL Cluster, they also enable users to achieve significantly improved levels of utilization from current and future generations of massively multi-core, multi-thread processor designs. A big thanks to Mikael Ronstrom, Senior MySQL Architect at Oracle, for his work in developing these enhancements and best practices. You can download MySQL Cluster 7.2 today and try out all of these enhancements. The Getting Started guides are an invaluable aid to quickly building a Proof of Concept Don’t forget to check out the MySQL Cluster 7.2 New Features whitepaper to discover everything that is new in the latest GA release

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• Windows 8 for productivity?

  - by Charles Young

  At long last I’ve started using Windows 8.  I boot from a VHD on which I have installed Office, Visio, Visual Studio, SQL Server, etc.  For a week, now, I’ve been happily writing code and documents and using Visio and PowerPoint.  I am, very much, a ‘productivity’ user rather than a content consumer.   I spend my days flitting between countless windows and browser tabs displayed across dual monitors.  I need to access a lot of different functionality and information in as fluid a fashion as possible. With that in mind, and like so many others, I was worried about Windows 8.  The Metro interface is primarily about content consumption on touch-enabled screens, and not really geared for people like me sitting in front of an 8-core non-touch laptop and an additional Samsung monitor.  I still use a mouse, not my finger.  And I create more than I consume. Clearly, Windows 8 won’t be viable for people like me unless Metro keeps out of my hair when using productivity and development tools.  With this in mind, I had long expected Microsoft to provide some mechanism for switching Metro off.  There was a registry hack in last year’s Developer Preview, but this capability has been removed.   That’s brave.  So, how have things worked out so far? Well, I am really quite surprised.  When I played with the Developer Preview last year, it was clear that Metro was unfinished and didn’t play well enough with the desktop.  Obviously I expected things to improve, but the context switching from desktop to full-screen seemed a heavy burden to place on users.  That sense of abrupt change hasn’t entirely gone away (how could it), but after a few days, I can’t say that I find it burdensome or irritating.   I’ve got used very quickly to ‘gesturing’ with my mouse at the bottom or top right corners of the screen to move between applications, using the Windows key to toggle the Start screen and generally finding my way around.   I am surprised at how effective the Start screen is, given the rather basic grouping features it provides.  Of course, I had to take control of it and sort things the way I want.  If anything, though, the Start screen provides a better navigation and application launcher tool than the old Start menu. What I didn’t expect was the way that Metro enhances the productivity story.  As I write this, I’ve got my desktop open with a maximised Word window.  However, the desktop extends only across about 85% of the width of my screen.  On the left hand side, I have a column that displays the new Metro email client.  This is currently showing me a list of emails for my main work account.  I can flip easily between different accounts and read my email within that same column.  As I work on documents, I want to be able to monitor my inbox with a quick glance. The desktop, of course, has its own snap feature.  I could run the desktop full screen and bring up Outlook and Word side by side.  However, this doesn’t begin to approach the convenience of snapping the Metro email client.  Consider that when I snap a window on the desktop, it initially takes up 50% of the screen.  Outlook doesn’t really know anything about snap, and doesn’t adjust to make effective use of the limited screen estate.  Even at 50% screen width, it is difficult to use, so forget about trying to use it in a Metro fashion. In any case, I am left with the prospect of having to manually adjust everything to view my email effectively alongside Word.  Worse, there is nothing stopping another window from overlapping and obscuring my email.  It becomes a struggle to keep sight of email as it arrives.  Of course, there is always ‘toast’ to notify me when things arrive, but if Outlook is obscured, this just feels intrusive. The beauty of the Metro snap feature is that my email reader now exists outside of my desktop.   The Metro app has been crafted to work well in the fixed width column as well as in full-screen.  It cannot be obscured by overlapping windows.  I still get notifications if I wish.  More importantly, it is clear that careful attention has been given to how things work when moving between applications when ‘snapped’.  If I decide, say to flick over to the Metro newsreader to catch up with current affairs, my desktop, rather than my email client, obligingly makes way for the reader.  With a simple gesture and click, or alternatively by pressing Windows-Tab, my desktop reappears. Another pleasant surprise is the way Windows 8 handles dual monitors.  It’s not just the fact that both screens now display the desktop task bar.  It’s that I can so easily move between Metro and the desktop on either screen.  I can only have Metro on one screen at a time which makes entire sense given the ‘full-screen’ nature of Metro apps.  Using dual monitors feels smoother and easier than previous versions of Windows. Overall then, I’m enjoying the Windows 8 improvements.  Strangely, for all the hype (“Windows reimagined”, etc.), my perception as a ‘productivity’ user is more one of evolution than revolution.  It all feels very familiar, but just better.

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• If I were in a Silverlight focus group, here is ten things I would say.

  - by mbcrump

  Silverlight is a great product right off the shelf. I use it, love it and spend a lot of time helping the community understand it. This however, doesn’t mean that I don’t think that it can get better. If I were invited to a Microsoft Focus Group about Silverlight here is 10 things I would say:  We need more navigation templates. I’ve found (4) templates that Microsoft has released (Cosmo, Windows 7, Accent and JetPack). This number needs to be around 16. In order to get more people developing for Silverlight, we need to give them a variety of templates to get them off the ground quickly. Silverlight needs to ship with the next version of Windows. At least version 4 needs to be pre-installed on Windows going forward. It’s small, in its own sandbox and I cannot find a reason for it not to be included. Silverlight needs to run on more platforms.  iOS and Android are the key here. I think Microsoft should shoot for Android first since I believe Android will take the lead in the mobile market (at least for the short-term). It would also be great to see Microsoft use Silverlight as the focus on their new tablets / “AppleTV”. I would even invest in getting it working with Kinect. When creating a new project in Silverlight, we should have the option to create a Unit Test. Most Silverlight developers are not unit testing. If this is surprising to you then you need to get out and talk to more developers. I partially blame this on Microsoft. When you create a new ASP.NET MVC application, you simply put a check to create a Unit Test project. We need the same thing for Silverlight. We should steer the developer into the right direction. Design patterns such as MVVM need to be easier to implement in Silverlight solutions.  I’d go so far as to say that MVVM Light should ship with Visual Studio. With the project / item templates and code snippets, Laurent puts you into the right direction. This is the way that it should have been. Easy for the 9-5 developer to grasp. I believe the majority of developers use code behind because that’s what is in all the demos provided by Microsoft. They are not trying to write sucky code it is that they simply don’t know a better way.  The XAP Files should be obfuscated/unused references deleted by default when in “Release” mode. A better Silverlight experience starts with a smaller XAP file. The less that a user has to download is the better, even with the majority of people on broadband. I would also recommend built-in obfuscation by Microsoft. People are paranoid that they can rename the .zip and run it through reflector. Get rid of the boring install experiences. Here is a great write up on what I’m talking about. The default “Install Silverlight” and “Loading screens” suck. They suck bad. We need a choice of templates that a professional designer has created.  Silverlight needs to supports more image formats. For example: it would be great to use .gif’s without converting them to .png.    Switching between Blend 4 and VS2010 to develop a Silverlight application is a pain. Probably one of the biggest issues that I can’t think of a good solution for. It would be nice if VS2012 had the best of both worlds and you never have to leave VS. We need reporting controls with SSRS included with the Silverlight Toolkit. I can’t think of another control that we need built into the toolkit. It would also be helpful to have export to .xls, .pdf and .doc included with the control. I hope that this post will at least get a few people talking. Who knows, Microsoft could be working on these things right now. Thanks for reading!  Subscribe to my feed CodeProject

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• Stumbling Through: Visual Studio 2010 (Part II)

  I would now like to expand a little on what I stumbled through in part I of my Visual Studio 2010 post and touch on a few other features of VS 2010.  Specifically, I want to generate some code based off of an Entity Framework model and tie it up to an actual data source.  Im not going to take the easy way and tie to a SQL Server data source, though, I will tie it to an XML data file instead.  Why?  Well, why not?  This is purely for learning, there are probably much better ways to get strongly-typed classes around XML but it will force us to go down a path less travelled and maybe learn a few things along the way.  Once we get this XML data and the means to interact with it, I will revisit data binding to this data in a WPF form and see if I cant get reading, adding, deleting, and updating working smoothly with minimal code.  To begin, I will use what was learned in the first part of this blog topic and draw out a data model for the MFL (My Football League) - I dont want the NFL to come down and sue me for using their name in this totally football-related article.  The data model looks as follows, with Teams having Players, and Players having a position and statistics for each season they played: Note that when making the associations between these entities, I was given the option to create the foreign key but I only chose to select this option for the association between Player and Position.  The reason for this is that I am picturing the XML that will contain this data to look somewhat like this: <MFL> <Position/> <Position/> <Position/> <Team>     <Player>         <Statistic/>     </Player> </Team> </MFL> Statistic will be under its associated Player node, and Player will be under its associated Team node no need to have an Id to reference it if we know it will always fall under its parent.  Position, however, is more of a lookup value that will not have any hierarchical relationship to the player.  In fact, the Position data itself may be in a completely different xml file (something Id like to play around with), so in any case, a player will need to reference the position by its Id. So now that we have a simple data model laid out, I would like to generate two things based on it:  A class for each entity with properties corresponding to each entity property An IO class with methods to get data for each entity, either all instances, by Id or by parent. Now my experience with code generation in the past has consisted of writing up little apps that use the code dom directly to regenerate code on demand (or using tools like CodeSmith).  Surely, there has got to be a more fun way to do this given that we are using the Entity Framework which already has built-in code generation for SQL Server support.  Lets start with that built-in stuff to give us a base to work off of.  Right click anywhere in the canvas of our model and select Add Code Generation Item: So just adding that code item seemed to do quite a bit towards what I was intending: It apparently generated a class for each entity, but also a whole ton more.  I mean a TON more.  Way too much complicated code was generated now that code is likely to be a black box anyway so it shouldnt matter, but we need to understand how to make this work the way we want it to work, so lets get ready to do some stumbling through that text template (tt) file. When I open the .tt file that was generated, right off the bat I realize there is going to be trouble there is no color coding, no intellisense no nothing!  That is going to make stumbling through more like groping blindly in the dark while handcuffed and hopping on one foot, which was one of the alternate titles I was considering for this blog.  Thankfully, the community comes to my rescue and I wont have to cast my mind back to the glory days of coding in VI (look it up, kids).  Using the Extension Manager (Available under the Tools menu), I did a quick search for tt editor in the Online Gallery and quickly found the Tangible T4 Editor: Downloading and installing this was a breeze, and after doing so I got some color coding and intellisense while editing the tt files.  If you will be doing any customizing of tt files, I highly recommend installing this extension.  Next, well see if that is enough help for us to tweak that tt file to do the kind of code generation that we wantDid you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Control HelpButton, HelpRequested, HelpButtonClicked - Instant help for windows Dialog Form components

  Instant help for windows dialog components is a great feature and very much known since windows 98. but I saw many many people are not aware it and query on Google to get help, but “help button” for dialogs helps you or your customers to get the help instantly. Every dialog window has help icon if that dialog was coded to enable it. it really helps to know the functionality of the components quickly. For example I was trying to pint a document from acrobat reader and opened printer properties to print the content front and back of the paper. If you observe there is a help button before close button. To get help on options of “Print on Both Sides” you would need to click on help button first and then click on the area on which you want to see the help. above picture shows help text for the options of “Print on Both Sides”. If you would like to get the help using keyboard you can use F1 key. Help button can be displayed only if minimize button and maximize button both are not shown unless you want go with custom buttons. below is the way if you want to get Help button for windows forms.   In this sample demo I want to have a checkbox and need to show help when I click on F1 on check box. So I created a form which country check box and help label as show in adjacent picture. Below is the code for your code bind file. using System; using System.Windows.Forms; namespace WindowsFormsApplication1 {     public partial classForm1: Form    {         publicForm1()         {             InitializeComponent();         }         private void Form1_Load(objectsender, EventArgs e)         {             this.Text = "Help Button Demo Form";             lblHelp.Text = "Press F1 on any component to get Instant Help";             this.HelpButton = true;             this.MaximizeBox = false;             this.MinimizeBox = false;             chkCountry.Tag = "Check or Uncheck Coutry Check Box";             chkCountry.HelpRequested += newHelpEventHandler(chkCountry_HelpRequested);             chkCountry.MouseLeave += newEventHandler(chkCountry_MouseLeave);         }         void chkCountry_HelpRequested(objectsender, HelpEventArgs hlpevent)         {             ControlrequestingControl = (Control)sender;             lblHelp.Text = (string)requestingControl.Tag;             hlpevent.Handled = true;         }         void chkCountry_MouseLeave(objectsender, EventArgs e)         {             lblHelp.Text = "Press F1 on any component to get Instant Help";         }     } } In above code  “HelpRequested” is an event will be fired when you click on F1 on Country checkbox. I stored the help information in the checkbox property called “Tag”. You might also maintain a property file to keep help text for each component differently. If you click on F1 when focus is on main form instead on individual component then generally separate help window opens. This can be done using the event “Form.HelpRequested” to open help windows as in below code. this.HelpRequested += newHelpEventHandler(Form1_HelpRequested); voidForm1_HelpRequested(objectsender, HelpEventArgs hlpevent) {     frmHelp.Show(); } span.fullpost {display:none;}

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• YouTube SEO: Video Optimization

  - by Mike Stiles

  SEO optimization is still regarded as one of the primary tools in the digital marketing kit. However and wherever a potential customer is conducting a search, brands want their content to surface in the top results. Makes sense. But without a regular flow of good, relevant content, your SEO opportunities run shallow. We know from several studies video is one of the most engaging forms of content, so why not make sure that in addition to being cool, your videos are helping you win the SEO game? Keywords:-Decide what search phrases make the most sense for your video. Don’t dare use phrases that have nothing to do with the content. You’ll make people mad.-Research those keywords to see how competitive they are. Adjust them so there are still lots of people searching for it, but there are not as many links showing up for it.-Search your potential keywords and phrases to see what comes up. It’s amazing how many people forget to do that. Video Title: -Try to start and/or end with your keyword.-When you search on YouTube, visual action words tend to come up as suggested searches. So try to use action words. Video Description: -Lead with a link to your site (include http://). -Don’t stuff this with your keyword. It leads to bad writing and it won’t work anyway. This is where you convince people to watch, so write for humans. Use some showmanship. -At the end, do a call to action (subscribe, see the whole playlist, visit our social channels, etc.) Video Tags:-Don’t over-tag. 5-10 tags per video is plenty. -If you’re compelled to have more than 10, that means you should probably make more videos specifically targeting all those keywords. Find Linking Pals:-45% of videos are discovered on video sites. But 44% are found through links on blogs and sites.-Write a blog about your video’s content, then link to the video in it. -A good site for finding places to guest blog is myblogguest.com-Once you find good linking partners, they’ll link to your future videos (as long as they’re good and you’re returning the favor). Tap the Power of Similar Videos:-Use Video Reply to associate your video with other topic-related videos. That’s when you make a video responding to or referencing a video made by someone else. Content:-Again, build up a portfolio of videos, not just one that goes after 30 keywords.-Create shorter, sequential videos that pull them deeper into the content and closer to a desired final action.-Organize your video topics separately using Playlists. Playlists show up as a whole in search results like individual videos, so optimize playlists the same as you would for a video. Meta Data:-Too much importance is placed on it. It accounts for only 15% of search success.-YouTube reads Captions or Transcripts to determine what a video is about. If you’re not using them, you’re missing out.-You get the SEO benefit of captions and transcripts whether the viewers has them toggled on or not. Promotion:-This accounts for 25% of search success.-Promote the daylights out of your videos using your social channels and digital assets. Don’t assume it’s going to magically get discovered. -You can pay to promote your video. This could surface it on the YouTube home page, YouTube search results, YouTube related videos, and across the Google content network. Community:-Accounts for 10% of search success.-Make sure your YouTube home page is a fun place to spend time. Carefully pick your featured video, and make sure your Playlists are featured. -Participate in discussions so users will see you’re present. The volume of ratings/comments is as important as the number of views when it comes to where you surface on search. Video Sitemaps:-As with a web site, a video sitemap helps Google quickly index your video.-Google wants to know title, description, play page URL, the URL of the thumbnail image you want, and raw video file location.-Sitemaps are xml files you host or dynamically generate on your site. Once you’ve made your sitemap, sign in and submit it using Google webmaster tools. Just as with the broadcast and cable TV channels, putting a video out there is only step one. You also have to make sure everybody knows it’s there so the largest audience possible can see it. Here’s hoping you get great ratings. @mikestiles

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• The architecture and technologies to use for a secure, fast, reliable and easily scalable web application

  - by DSoul

  ^ For actual questions, skip to the lists down below I understand, that his is a vague topic, but please, before you turn the other way and disregard me, hear me out. I am currently doing research for a web application(I don't know if application is the correct word for it, but I will proceed w/ that for now), that one day might need to be everything mentioned in the title. I am bound by nothing. That means that every language, OS and framework is acceptable, but only if it proves it's usefulness. And if you are going to say, that scalability and speed depend on the code I write for this application, then I agree, but I am just trying to find something, that wouldn't stand in my way later on. I have done quite a bit reading on this subject, but I still don't have a clear picture, to what suits my needs, so I come to you, StackOverflow, to give me directions. I know you all must be wondering what I'm building, but I assure you, that it doesn't matter. I have heard of 12 factor app though, if you have any similar guidelines or what is, to suggest the please, go ahead. For the sake of keeping your answers as open as possible, I'm not gonna provide you my experience regarding anything written in this question. ^ Skippers, start here First off - the weights of the requirements are probably something like that (on a scale of 10): Security - 10 Speed - 5 Reliability (concurrency) - 7.5 Scalability - 10 Speed and concurrency are not a top priority, in the sense, that the program can be CPU intensive, and therefore slow, and only accept a not-that-high number of concurrent users, but both of these factors must be improvable by scaling the system Anyway, here are my questions: How many layers should the application have, so it would be future-proof and could best fulfill the aforementioned requirements? For now, what I have in mind is the most common version: Completely separated front end, that might be a web page or an MMI application or even both. Some middle-ware handling communication between the front and the back end. This is probably a server that communicates w/ the front end via HTTP. How the communication w/ the back end should be handled is probably dependent on the back end. The back end. Something that handles data through resources like DB and etc. and does various computations w/ the data. This, as the highest priority part of the software, must be easily spread to multiple computers later on and have no known security holes. I think ideally the middle-ware should send a request to a queue from where one of the back end processes takes this request, chops it up to smaller parts and buts these parts of the request back onto the same queue as the initial request, after what these parts will be then handled by other back end processes. Something *map-reduce*y, so to say. What frameworks, languages and etc. should these layers use? The technologies used here are not that important at this moment, you can ignore this part for now I've been pointed to node.js for this part. Do you guys know any better alternatives, or have any reasons why I should (not) use node.js for this particular job. I actually have no good idea, what to use for this job, there are too many options out there, so please direct me. This part (and the 2. one also, I think) depend a lot on the OS, so suggest any OSs alongside w/ the technologies/frameworks. Initially, all computers (or 1 for starters) hosting the back end are going to be virtual machines. Please do give suggestions to any part of the question, that you feel you have comprehensive knowledge and/or experience of. And also, point out if you feel that any part of the current set-up means an instant (or even distant) failure or if I missed a very important aspect to consider. I'm not looking for a definitive answer for how to achieve my goals, because there certainly isn't one, for I haven't provided you w/ all the required information. I'm just looking for recommendations and directions on what to look into. Also, bare in mind, that this isn't something that I have to get done quickly, to sell and let it be re-written by the new owner (which, I've been told for multiple times, is what I should aim for). I have all the time in the world and I really just want to learn doing something really high-end. Also, excuse me if my language isn't the best, I'm not a native. Anyway. Thanks in advance to anyone, who takes the time to help me out here. PS. When I do seem to come up w/ a good architecture/design for this project, I will certainly make it an open project and keep you guys up to date w/ it's development. As in what you could have told me earlier and etc. For obvious reasons the very same question got closed on SO, but could you guys still help me?.

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• Nagios Creating lots of zombie process

  - by pradeepchhetri

  In my monitoring box, I have lots of zombie process created by nagios and they gets remove quickly also. I am using active checks to perform monitoring of my servers. I accumulated the defunct processes created using the following command: $ top -d 0.25 -b -n 20 > topout.txt This collected the output of top with 0.25s delay 20 times. I did grep on the topout.txt for the defunct process. $ cat topout.txt | grep defunct I get the following output. 8957 nagios 20 0 0 0 0 Z 6.0 0.0 0:00.02 nagios <defunct> 8951 nagios 20 0 0 0 0 Z 3.0 0.0 0:00.01 nagios <defunct> 8954 nagios 20 0 0 0 0 Z 3.0 0.0 0:00.01 nagios <defunct> 8945 nagios 20 0 0 0 0 Z 0.0 0.0 0:00.01 nagios <defunct> 8946 nagios 20 0 0 0 0 Z 0.0 0.0 0:00.01 nagios <defunct> 8980 nagios 20 0 0 0 0 Z 0.0 0.0 0:00.01 nagios <defunct> 9000 nagios 20 0 0 0 0 Z 0.0 0.0 0:00.00 nagios <defunct> 9024 nagios 20 0 0 0 0 Z 7.0 0.0 0:00.02 nagios <defunct> 9025 nagios 20 0 0 0 0 Z 3.5 0.0 0:00.01 nagios <defunct> 9040 nagios 20 0 0 0 0 Z 3.1 0.0 0:00.01 nagios <defunct> 9086 nagios 20 0 0 0 0 Z 0.0 0.0 0:00.01 nagios <defunct> 9087 nagios 20 0 0 0 0 Z 0.0 0.0 0:00.01 nagios <defunct> 9123 nagios 20 0 0 0 0 Z 6.1 0.0 0:00.02 nagios <defunct> 9126 nagios 20 0 0 0 0 Z 3.0 0.0 0:00.01 nagios <defunct> 9131 nagios 20 0 0 0 0 Z 3.0 0.0 0:00.01 nagios <defunct> 9091 nagios 20 0 0 0 0 Z 0.0 0.0 0:00.05 nagios <defunct> 9111 nagios 20 0 0 0 0 Z 0.0 0.0 0:00.01 nagios <defunct> 9119 nagios 20 0 0 0 0 Z 0.0 0.0 0:00.01 nagios <defunct> 9118 nagios 20 0 0 0 0 Z 0.0 0.0 0:00.01 nagios <defunct> 9151 nagios 20 0 0 0 0 Z 2.9 0.0 0:00.02 nagios <defunct> 9153 nagios 20 0 0 0 0 Z 2.9 0.0 0:00.02 nagios <defunct> 9150 nagios 20 0 0 0 0 Z 0.0 0.0 0:00.01 nagios <defunct> 9164 nagios 20 0 0 0 0 Z 3.5 0.0 0:00.02 nagios <defunct> 9171 nagios 20 0 0 0 0 Z 3.5 0.0 0:00.02 nagios <defunct> 9154 nagios 20 0 0 0 0 Z 0.0 0.0 0:00.01 nagios <defunct> 9156 nagios 20 0 0 0 0 Z 0.0 0.0 0:00.01 nagios <defunct> 9163 nagios 20 0 0 0 0 Z 0.0 0.0 0:00.01 nagios <defunct> 9167 nagios 20 0 0 0 0 Z 0.0 0.0 0:00.01 nagios <defunct> 9178 nagios 20 0 0 0 0 Z 3.8 0.0 0:00.02 nagios <defunct> 9174 nagios 20 0 0 0 0 Z 0.0 0.0 0:00.01 nagios <defunct> 9179 nagios 20 0 0 0 0 Z 0.0 0.0 0:00.01 nagios <defunct> 9182 nagios 20 0 0 0 0 Z 0.0 0.0 0:00.01 nagios <defunct> Can somebody help me in finding out the reason of these zombie processes and how i can prevent these zombie processes ?

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• How can I automatically update Flash Player whenever a new version is released? [closed]

  - by user219950

  Summary: Flash Player Update Service doesn't run on a reliable schedule, and doesn't automatically download and apply updates when it does run. Given the importance of having an up-to-date version of Flash Player installed (for those of us who don't use Chrome with its built-in player), I would like to find a way to ensure that new updates are promptly detected and installed. What follows are the details of my efforts to solve this problem on my own... Appendix A: Flash Player Update Service OK, way back in Flash Player 11.2 (or so?) Adobe added the Flash Player Update Service (FlashPlayerUpdateService.exe), it was supposed to keep the Flash Player updated... Upon installation, FPUS is configured to run as a Windows Service, with Start Type set to Manual. A Scheduled Task (Adobe Flash Player Updater.job) is added to start this service every hour. So far, so good - this set-up avoids having a constantly-running service, but makes sure that the checks are run often enough to catch any updates quickly. Google's software updater is configured in a similar fashion, and that works just fine... ...And yet, when I checked the version of my installed Flash Player, I found it was 11.6.602.180, which, based on looking at the timestamps of the files in C:\Windows\System32\Macromed\Flash was last updated (or installed) on Tue, Mar 12, 2013 --- 3/12/13, 5:00:08pm. I made this observation on Thu, Apr 25, 2013 --- 4/25/13, 7:00:00pm, and upon checking Adobe's website found that the current version of Flash Player was 11.7.700.169. That's over a month since the last update, with a new one clearly available on the website but with no indication that the hourly check running on my machine has noticed it or has any intention of downloading it. Appendix B: running the Flash Player updater manually Once upon a time, running FlashUtil32_<version_Plugin.exe -update plugin would give you a window with an Install button; pressing it would download the installer for the current version (automatically, without opening a browser) and run it, then you'd click thru that installer & be done. It was manual, but it worked! Finding my current installation out of date (see Appendix A), I first tried this manual update process. However... Running FlashUtil32_<version_ActiveX.exe -update activex (in my case, that's FlashUtil32_11_6_602_180_ActiveX.exe -update activex) ...only presents a window with a Download button, clicking that Download button opens my browser to the URL https://get3.adobe.com/flashplayer/update/activex. Running FlashUtil32_<version_Plugin.exe -update plugin (in my case, that's FlashUtil32_11_6_602_180_Plugin.exe -update plugin) ...only presents a window with a Download button, clicking that Download button opens my browser to the URL https://get3.adobe.com/flashplayer/update/plugin. I could continue with the Download page it sent me to, uncheck the foistware box ("Free! McAfee Security Scan Plus"), download that installer (ActiveX, no foistware: install_flashplayer11x32axau_mssd_aih.exe, Plugin, no foistware: install_flashplayer11x32au_mssd_aih.exe) & probably have an updated Flash...but then, what is the point of the Flash Player Update Service if I have to manually download & run another exe? Epilogue I've since come to suspect that the update service is intentionally hobbled to drive early adopters to the manual download page. If this is true, there's probably no solution to this short of writing my own updater; hopefully I am wrong.

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• Wireless AAA for a small, bandwidth-limited hotel.

  - by Anthony Hiscox

  We (the tech I work with and myself) live in a remote northern town where Internet access is somewhat of a luxury, and bandwidth is quite limited. Here, overage charges ranging from few hundreds, to few thousands of dollars a month, is not uncommon. I myself incur regular monthly charges just through my regular Internet usage at home (I am allowed 10G for $60CAD!) As part of my work, I have found myself involved with several hotels that are feeling this. I know that I can come up with something to solve this problem, but I am relatively new to system administration and I don't want my dreams to overcome reality. So, I pass these ideas on to you, those with much more experience than I, in hopes you will share some of your thoughts and concerns. This system must be cost effective, yes the charges are high here, but the trust in technology is the lowest I've ever seen. Must be capable of helping client reduce their usage (squid) Allow a limited (throughput and total usage) amount of free Internet, as this is often franchise policy. Allow a user to track their bandwidth usage Allow (optional) higher speed and/or usage for an additional charge. This fee can be obtained at the front desk on checkout and should not require the use of PayPal or Credit Card. Unfortunately some franchises have ridiculous policies that require the use of a third party remote service to authenticate guests to your network. This means WPA is out, and it also means that I do not auth before Internet usage, that will be their job. However, I do require the ABILITY to perform authentication for Internet access if a hotel does not have this policy. I will still have to track bandwidth (under a guest account by default) and provide the same limiting, however the guest often will require a complete 'unlimited' access, in terms of existence, not throughput. Provide firewalling capabilities for hotels that have nothing, Office, and Guest network segregation (some of these guys are running their office on the guest network, with no encryption, and a simple TOS to get on!) Prevent guests from connecting to other guests, however provide a means to allow this to happen. IE. Each guest connects to a page and allows the other guest, this writes a iptables rule (with python-netfilter) and allows two rooms to play a game, for instance. My thoughts on how to implement this. One decent box (we'll call it a router now) with a lot of ram, and 3 NIC's: Internet Office Guests (AP's + In Room Ethernet) Router Firewall Rules Guest can talk to router only, through which they are routed to where they need to go, including Internet services. Office can be used to bridge Office to Internet if an existing solution is not in place, otherwise, it simply works for a network accessible web (webmin+python-webmin?) interface. Router Software: OpenVZ provides virtualization for a few services I don't really trust. Squid, FreeRADIUS and Apache. The only service directly accessible to guests is Apache. Apache has mod_wsgi and django, because I can write quickly using django and my needs are low. It also potentially has the FreeRADIUS mod, but there seems to be some caveats with this. Firewall rules are handled on the router with iptables. Webmin (or a custom django app maybe) provides abstracted control over any features that the staff may need to access. Python, if you haven't guessed it's the language I feel most comfortable in, and I use it for almost everything. And finally, has this been done, is it a overly massive project not worth taking on for one guy, and/or is there some tools I'm missing that could be making my life easier? For the record, I am fairly good with Python, but not very familiar with many other languages (I can struggle through PHP, it's a cosmetic issue there). I am also an avid linux user, and comfortable with config files and command line. Thank you for your time, I look forward to reading your responses. Edit: My apologies if this is not a Q&A in the sense that some were expecting, I'm just looking for ideas and to make sure I'm not trying to do something that's been done. I'm looking at pfSense now as a possible start for what I need.

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• Oracle performance problem

  - by jreid42

  We are using an Oracle 11G machine that is very powerful; has redundant storage etc. It's a beast from what I have been told. We just got this DB for a tool that when I first came on as a coop had like 20 people using, now its upwards of 150 people. I am the only one working on it :( We currently have a system in place that distributes PERL scripts across our entire data center essentially giving us a sort of "grid" computing power. The Perl scripts run a sort of simulation and report back the results to the database. They do selects / inserts. The load is not very high for each script but it could be happening across 20-50 systems at the same time. We then have multiple data centers and users all hitting the same database with this same approach. Our main problem with this is that our database is getting overloaded with connections and having to drop some. We sometimes have upwards of 500 connections. These are old perl scripts and they do not handle this well. Essentially they fail and the results are lost. I would rather avoid having to rewrite a lot of these as they are poorly written, and are a headache to even look at. The database itself is not overloaded, just the connection overhead is too high. We open a connection, make a quick query and then drop the connection. Very short connections but many of them. The database team has basically said we need to lower the number of connections or they are going to ignore us. Because this is distributed across our farm we cant implement persistent connections. I do this with our webserver; but its on a fixed system. The other ones are perl scripts that get opened and closed by the distribution tool and thus arent always running. What would be my best approach to resolving this issue? The scripts themselves can wait for a connection to be open. They do not need to act immediately. Some sort of queing system? I've been suggested to set up a few instances of a tool called "SQL Relay". Maybe one in each data center. How reliable is this tool? How good is this approach? Would it work for what we need? We could have one for each data center and relay requests through it to our main database, keeping a pipeline of open persistent connections? Does this make sense? Is there any other suggestions you can make? Any ideas? Any help would be greatly appreciated. Sadly I am just a coop student working for a very big company and somehow all of this has landed all on my shoulders (there is literally nobody to ask for help; its a hardware company, everybody is hardware engineers, and the database team is useless and in India) and I am quite lost as what the best approach would be? I am extremely overworked and this problem is interfering with on going progress and basically needs to be resolved as quickly as possible; preferably without rewriting the whole system, purchasing hardware (not gonna happen), or shooting myself in the foot. HELP LOL!

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• creating a heirarchy of terminals or workspaces

  - by intuited

  <rant This question occurred to me ('occurred' meaning 'whispered seductively in my ear for the 100th time') while using GNU-screen, so I'll make that my example. However this is a much more general question about user interfaces and what I perceive as a flawmissing feature in every implementation I've yet seen. I'm wondering if there is some way to create a heirarchy/tree of terminals in a screen session. EG I'd like to have something like 1 bash 1.1 bash 1.2 bash 2 bash 3 bash 3.1 bash 3.1.1 bash 3.1.2 bash It would be good if the terminals could be labelled instead of having to be navigated to via some arrangement that I suspect doesn't exist. So then you could jump to one using eg ^A:goto happydays or ^A:goto dykstra.angry. So to generalize that: Firefox, Chrome, Internet Explorer, gnome-terminal, roxterm, konsole, yakuake, OpenOffice, Microsoft Office, Mr. Snuffaluppagus's Funtime Carousel™, and Your Mom's Jam Browser™ all offer the ability to create a flat set of tabs containing documents of an identical nature: web pages, terminals, documents, fun rideable animals, and jams. GNU-screen implements the same functionality without using tabs. Linux and OS/X window managers provide the ability to organize windows into an array of workspaces, which amounts to again, the same deal. Over the past few years, this has become a more or less ubiquitous concept which has been righteously welcomed into the far reaches of the computer interface funfest. Heavy users of these systems quickly encounter a problem with it: the set of entities is flat. In the case of workspaces, an option may be available to create a 2d array. However none of these applications furnish their users with the ability to create heirarchies, similar to filesystem directory structures, containing instances of their particular contained type. I for one am consistently bothered by this, and am wondering if the community can offer some wisdom as to why this has not happened in any of the foremost collections of computational functionality our culture has yet produced. Or if perhaps it has and I'm just an ignorant savage. I'd like to be able to not only group things into a tree structure, but also to create references (aka symbolic links, aka pointers) from one part of the structure to another, as well as apply properties (eg default directory, colorscheme, ...) recursively downward from a given node. I see no reason why we shouldn't be able to save these structures as known sessions, and apply tags to particular instances. So then you can sort through them by tag, find them by name, or just use the arrow keys (with an appropriate modifier) to move left or right and in or out of a given level. Another key combo would serve to create a branch in the place of the current terminal/webpage/lifelike statue/spreadsheet/spreadsheet sheet/presentation/jam and move that entity into the new branch, then create a fresh one as a sibling to it: a second leaf node within the same branch node. They would get along well. I find it a bit astonishing that this hasn't happened yet, and the only reason I can venture as a guess is that the creators of these fine systems do not consider such functionality to be useful to a significant portion of their userbase. I posit that the probability that that such an assumption would be correct is pretty low. On the other hand, given the relative ease with which such structures can be implemented using modern libraries/languages, it doesn't seem likely that difficulty of implementation would be a major roadblock. If it could be done in 1972 or whenever within the constraints of a filesystem driver, it should be relatively painless to implement in 2010 in a fullblown application. Given that all of these systems are capable of maintaining a set of equivalent entities, it seems unlikely that a major infrastructure overhaul would be necessary in order to enable a navigable heirarchy of them. </rant Mostly I'm just looking to start up a discussion and/or brainstorming on this topic. Any ideas, examples, criticism, or analysis are quite welcome. * Mr. Snuffaluppagus's Funtime Carousel is a registered trademark of Children's Television Workshop Inc. * Your Mom's Jam Browser is a registered trademark of Your Mom Inc.

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• DHCP and DNS services configuration for VOIP system, windows domain, etc

  - by Stemen

  My company has numerous physical offices (for purposes of this discussion, 15 buildings). Some of them are well-connected to our primary data center via fiber. Others will be connected to the data center by P2P T1. We are in the beginning stages of implementing an Avaya VOIP telephone system, and we will be replacing a significant portion of our network infrastructure in the process. In tandem with the phone system implementation, we are going to be re-addressing some of our networks, and consolidating most of our Windows domains into one (not all domains, just most). We currently have quite a few Windows domains, and they of course each have their own DNS zones. A few of those networks currently use DHCP, but the majority use static IP assignments for every device. I'm tired of managing static assignments -- I want to use DHCP configuration on everything except servers. Printers and etc will have DHCP reservations. The new IP phones will need to get IP addresses from DHCP, though they need to be in a separate VLAN from the computers/printers/etc. The computers and printers need to be registered in DNS. That's currently handled by the Windows DHCP servers on each of the respective domains. We need to place a priority on DHCP and DNS being available on a per-site basis (in case something were to interrupt the WAN connection) for computers and (primarily) phones. Smaller locations (which will have IP phones but not be a member of any Windows domain) will not have any Windows DNS/DHCP server(s) available. We also are looking for the easiest way to replace a part if it were to fail. That is to say, if a server/appliance/router hosting DHCP were to crash hard, and we couldn't extremely quickly recover the DHCP reservations and leases (and subsequently restore them onto a cold spare), we anticipate that bad things could happen. What is the best idea for how to re-implement DNS and DHCP keeping all of the above in mind? Some thoughts that have been raised (by myself or my coworkers): Use Windows DNS and DHCP servers, where they exist, and use IP helpers to route DHCP requests to some other Windows server if necessary. May not be acceptable if the WAN goes down and clients don't get a DHCP response. Use Windows DNS (everywhere, over WAN in some cases) and a mix of Windows DHCP and DHCP provided by Cisco routers. Every site would be covered for DHCP, but from what I've read, Cisco routers can't handle dynamic registration of DHCP clients to Windows DNS servers, which might create a problem where Cisco routers are used for DHCP. Use Windows DNS (everywhere, over WAN in some cases) and a mix of Windows DHCP and DHCP provided by some service running on an extremely low-price linux server. Is there any such software that would allow DHCP leases granted by these linux boxes to be dynamically registered on the Windows DNS servers? Come up with a Linux solution for both DNS and DHCP, and deploy low-price linux servers to every site. Requirements would be that the DNS zone be multi-master (like Windows DNS integrated with Active Directory), that DHCP be able to make dynamic DNS registrations in that zone, for every lease (where a hostname is provided and is thus possible), and that multiple servers be either authoritative for the same DHCP scope or at least receiving a real-time copy / replication / sync of the leases table so that if one server dies, we still know which MAC has what address. Purchase dedicated DNS/DHCP appliances, deploying to all sites. From what I read/see, this solves all of our technical problems. Then come the financial problems... I don't have a ton of money to spend on this. Or, some other solution that we've thus far overlooked and will consider upon recommendation. Can Cisco routers or Windows servers sync DHCP lease tables so that multiple servers can be authoritative (or active/passive for all I care) for the same scope, in case one of the partners were to fail? I've read online (repeatedly) that ISC's DHCP is able to maintain the same lease table across multiple servers, in order to solve this problem. Does anyone have any experience or advice to regarding that?

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• Issues with Verizon's "Network Extender" device talking on my home network.

  - by Logan

  I recently switched my phone service to Verizon from ATT, and I get somewhat spotty service in my house. I called them and they sent me a "network extender" device for free. Its a femtocell that connects to my home network. The directions that come with it are very dumbed down, basically just say to connect it to your router and put it near a window (so it can get a GPS signal, it has to make sure its within the correct area before operating). The problem I'm having is the network light on it stays red. The troubleshooting information that came with it tells me this means there is a bad network connection. Its connected through an ASUS router running DD-WRT. No other devices on my network have a problem with it, including a Western Digital WDLIVE device, mine and my wife's cell phones (via wifi), a Wii, and an Xbox. If I connect the device directly to my cable modem, the light goes blue (which means good) and it starts working. So this tells me that its definately a configuration issue with my router. Verizon basically washed their hands of me when I connected it to my cable modem, and told me that its a router issue and to try a different router. Because normal people just have extra routers laying around their houses... When I connect it to the router, I can watch the DHCP Clients list on the status page, and the MAC of the network extender quickly fills up the clients list, grabbing every available DHCP address. Its like it grabs an address, can't connect to the internet, releases it, grabs another, then another, then another. So in the DHCP server settings I assigned a static IP to its MAC. This made it quit doing what it was doing before, but its still not working. I found the ports I needed to open on verizon's website, and opened them in the port forwarding config on my router. This still didn't help. So, I tried setting the network extender device's IP as the DMZ IP on the router. This still did no good. I called Verizon back and got the tech to write up a report which he passed on to a "senior network tech" who I got a call back from a few hours ago. This guy told me that while an ASUS router isn't listed as a supported device, he's not really sure why its not working. He suggested restoring the firmware to stock ASUS firmware and trying again. I have a very hard time believing its DD-WRT doing this, since every other device is working just fine with it. But its also not the Network Extender, since it works just fine when connected directly to the modem. At this point I'm out of ideas, and the next step is to restore the stock firmware on my router, and then going to walmart and getting a linksys WRT-54G to try. Is there anything else I could try before going that drastic? Cliffs- -Network extender won't work behind router, works when connected directly to cable modem. -Extender goes nuts when allowed to pick its own DHCP address, I had to assign it a static IP. -Won't work when correct ports are forwarded to it -Won't work with a DMZ address.

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• How to stop Apache from crashing my entire server?

  - by CyberShadow

  I maintain a Gentoo server with a few services, including Apache. It's fairly low-end (2GB of RAM and a low-end CPU with 2 cores). My problem is that, despite my best efforts, an over-loaded Apache crashes the entire server. In fact, at this point I'm close to being convinced that Linux is a horrible operating system that isn't worth anyone's time looking for stability under load. Things I tried: Adjusting oom_adj for the root Apache process (and thus all its children). That had close to no effect. When Apache was overloaded it would bring the system to a grind, as the system paged out everything else before it got to kill anything. Turning off swap. Didn't help, it would unload memory paged to binaries of processes and other files on /, thus causing the same effect. Putting it in a memory-limited cgroup (limited to 512 MB of RAM, 1/4th of the total). This "worked", at least in my own stress tests - except the server keeps crashing under load (basically stalling all other processes, inaccessible via SSH, etc.) Running it with idle I/O priority. This wasn't a very good idea in the end, because it just caused the system load to climb indefinitely (into the thousands) with almost no visible effect - until you tried to access an unbuffered part of the disk. This caused the task to freeze. (So much for good I/O scheduling, eh?) Limiting the number of concurrent connections to Apache. Setting the number too low caused web sites to become unresponsive due to most slots being occupied with long requests (file downloads). I tried various Apache MPMs without much success (prefork, event, itk). Switching from prefork/event+php-cgi+suphp to itk+mod_php. This improved performance, but didn't solve the actual problem. Switching I/O schedulers (cfq to deadline). Just to stress this out: I don't care if Apache itself goes down under load, I just want the rest of my system to remain stable. Of course, having Apache recover quickly after a brief period of intensive load would be great to have, but one step at a time. Right now I am mostly dumbfounded by how can humanity, in this day and age, design an operating system where such a seemingly simple task (don't allow one system component to crash the entire system) seems practically impossible - or at least, very hard to do. Please don't suggest things like VMs or "BUY MORE RAM". Some more information gathered with a friend's help: The processes hang when the cgroup oom killer is invoked. Here's the call trace: [<ffffffff8104b94b>] ? prepare_to_wait+0x70/0x7b [<ffffffff810a9c73>] mem_cgroup_handle_oom+0xdf/0x180 [<ffffffff810a9559>] ? memcg_oom_wake_function+0x0/0x6d [<ffffffff810aa041>] __mem_cgroup_try_charge+0x32d/0x478 [<ffffffff810aac67>] mem_cgroup_charge_common+0x48/0x73 [<ffffffff81081c98>] ? __lru_cache_add+0x60/0x62 [<ffffffff810aadc3>] mem_cgroup_newpage_charge+0x3b/0x4a [<ffffffff8108ec38>] handle_mm_fault+0x305/0x8cf [<ffffffff813c6276>] ? schedule+0x6ae/0x6fb [<ffffffff8101f568>] do_page_fault+0x214/0x22b [<ffffffff813c7e1f>] page_fault+0x1f/0x30 At this point, the apache memory cgroup is practically deadlocked, and burning CPU in syscalls (all with the above call trace). This seems like a problem in the cgroup implementation...

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• Server Cabinet/Room Cooling

  - by user37226

  Hello all. I currently have two desktops and three servers in my office sitting on the floor (I know this is bad). With that many servers the ambient temperature in the room goes up quickly. I am located in Dallas, TX so during the winter, if the heat is kept low, it is not a problem, but during the summer it easily jumps the room +10 degrees. I have decided and found a free 42U server cabinet that a hosting company was throwing away to house all of these systems in. One server is in a rack mount case while the other four servers are housed in mid-tower cases. I have purchased shelves for each computer and plan to lay the towers side ways on these shelves (as replacing the cases costs a heck of a lot of money). I like the idea of housing all of these systems in the cabinet because it will save a lot of room and clean up all of the cabling currently laying all over the office floor. When putting this setup together over the next couple of weeks, I want to address issues with dust and cooling. The server cabinet has a fan on top, front plexiglass door and a rear metal door with vent wholes on the bottom. First the cooling issues. I know I am going to want to have cool air enter the bottom of the cabinet and exit the top. I do not want the room heating up though as this will make my work area hot and then make the servers warmer as the air eventually reenters the cabinet. I had an idea to fix this problem, but am unsure if it will work. I was thinking of taking flexible piping and adapting it to the back fans of the computer having the other end of the pipe at the top close to the cabinet's top mounted fan. I was then thinking of creating a duct around the top fan into the attic. Now I am very concerned that the attic will cause issues with this type of setup because during July/August time frame, the attic is easily 120 degrees F. I could also use the flexible pipe to take it to an attic exhaust vent if it would be better to vent it into the 100 degree air outside (at least there may be wind. The other option would be to buy a small portable air conditioner. This may be a possibility, but do I want to spend the extra money on power? I bet this increases the noise. Plus they are around $250 on Amazon. What would you all recommend? Depending on the solution I end up running with above, I would also like to limit the dust that gets into the cabinet. If I were to cut a whole and mount a second cabinet fan on the bottom of the rear door, could I possibly mount a standard home air filter on the other side of that whole? Thanks in advance for your recommendations. I look forward to reading your interesting ideas.

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• Server Cabinet/Room Cooling

  - by user37226

  Hello all. I currently have two desktops and three servers in my office sitting on the floor (I know this is bad). With that many servers the ambient temperature in the room goes up quickly. I am located in Dallas, TX so during the winter, if the heat is kept low, it is not a problem, but during the summer it easily jumps the room +10 degrees. I have decided and found a free 42U server cabinet that a hosting company was throwing away to house all of these systems in. One server is in a rack mount case while the other four servers are housed in mid-tower cases. I have purchased shelves for each computer and plan to lay the towers side ways on these shelves (as replacing the cases costs a heck of a lot of money). I like the idea of housing all of these systems in the cabinet because it will save a lot of room and clean up all of the cabling currently laying all over the office floor. When putting this setup together over the next couple of weeks, I want to address issues with dust and cooling. The server cabinet has a fan on top, front plexiglass door and a rear metal door with vent wholes on the bottom. First the cooling issues. I know I am going to want to have cool air enter the bottom of the cabinet and exit the top. I do not want the room heating up though as this will make my work area hot and then make the servers warmer as the air eventually reenters the cabinet. I had an idea to fix this problem, but am unsure if it will work. I was thinking of taking flexible piping and adapting it to the back fans of the computer having the other end of the pipe at the top close to the cabinet's top mounted fan. I was then thinking of creating a duct around the top fan into the attic. Now I am very concerned that the attic will cause issues with this type of setup because during July/August time frame, the attic is easily 120 degrees F. I could also use the flexible pipe to take it to an attic exhaust vent if it would be better to vent it into the 100 degree air outside (at least there may be wind. The other option would be to buy a small portable air conditioner. This may be a possibility, but do I want to spend the extra money on power? I bet this increases the noise. Plus they are around $250 on Amazon. What would you all recommend? Depending on the solution I end up running with above, I would also like to limit the dust that gets into the cabinet. If I were to cut a whole and mount a second cabinet fan on the bottom of the rear door, could I possibly mount a standard home air filter on the other side of that whole? Thanks in advance for your recommendations. I look forward to reading your interesting ideas.

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• The best dvd ripper software in 2014 review

  - by user328170

  The top 3 DVD Ripping Tools in 2014 Nowadays everyone may have several smart mobile devices, such as iphone, ipad air, ipad mini ,Samsung Galaxy and Sony Xperia. If you want to take your movies with your mobile devices, or sometimes just want to backup those classic physical discs on your notebook or workstation with high quality resolutions, you need a fast and stable software to rip them and convert them to the format you like. Fortunately, there are plenty of great software products designed to make the process easy and transform DVD to the files that are playable on any mobile device you choose. We have done a full review on dozens of products. Here are five of the best, based on our review. We test the software from its ripping speed, friendly use guide , reliability and ripping capability. The top one is still Winx DVD Ripper platinum. We've test its 6.1 version 2 years ago for its ability to quickly and easily rip DVDs and Blu-ray discs to high quality MKV files with a single click. It gave us deep impression in the test. This time we test it’s lastest 7.3.5 version. Besides easy use and speed, we test its capability to decrypt all kinds of discs with different protect method, for example, Disney X-project DRM , Sony ArccOS, RCE and region code. The result shows that winx dvd ripper platinum still maintain its advantages in all the area. Winx dvd ripper platinum is a more focused on DVD ripping software with the basic duty to rip and convert DVD. The color of UI is a modern technical sense. All the main functions are shown obviously while others specials are hidden for advanced users, making it more clear and convenient to make option. There are two company weisoft limited and Digiarty who can provide the software. Weisoft limited focus on USA, UK and Australia market. Digiarty focus on others. ripping speed ????? friendly use guide ????? reliability ????? ripping capability ????? The second one DVDFab DVDFab is also very robust during ripping dics. It can also decrypt most of the dics in the market. The shortage it still friendly use and speed. We'd note that the app is frequently updated to cut through the copy protection on even the latest DVDs and Blu-ray discs . The app is shareware, meaning most features are free, including decrypting and ripping to your hard drive. Many of you note that you use another app for compression and authoring, but many of you say they hey, storage is cheap, and the rips from DVDFab are easy, one-click, and work. ripping speed ??? friendly use guide ???? reliability ????? ripping capability ????? The Third one is Handbrake Handbrake is our favorite video encoder for a reason: it's simple, easy to use, easy to install, and offers a lots of options to get the high quality file as a result. If you're scared by them, you don't even have to use them—the app will compensate for you and pick some settings it thinks you'll like based on your destination device. So many of you like Handbrake that many of you use it in conjunction with another app (like VLC, which makes ripping easy)—you'll let another app do the rip and crack the DRM on your discs, and then process the file through Handbrake for encoding. The app is fast, can make the most of multi-core processors to speed up the process, and is completely open source. ripping speed ??? friendly use guide ???? reliability ???? ripping capability ????

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• Problem with waitable timers in Windows (timeSetEvent and CreateTimerQueueTimer)

  - by MusiGenesis

  I need high-resolution (more accurate than 1 millisecond) timing in my application. The waitable timers in Windows are (or can be made) accurate to the millisecond, but if I need a precise periodicity of, say, 35.7142857141 milliseconds, even a waitable timer with a 36 ms period will drift out of sync quickly. My "solution" to this problem (in ironic quotes because it's not working quite right) is to use a series of one-shot timers where I use the expiration of each timer to call the next timer. Normally a process like this would be subject to cumulative error over time, but in each timer callback I check the current time (with System.Diagnostics.Stopwatch) and use this to calculate what the period of the next timer needs to be (so if a timer happens to expire a little late, the next timer will automagically have a shorter period to compensate). This works as expected, except that after maybe 10-15 seconds the timer system seems to get bogged down, and a few timer callbacks here and there arrive anywhere from 25 to 100 milliseconds late. After a couple of seconds the problem goes away and everything runs smoothly again for 10-15 seconds, and then the stuttering again. Since I'm using Stopwatch to set each timer period, I'm also using it to monitor the arrival times of each timer callback. During the smooth-running periods, most (maybe 95%) of the intervals are either 35 or 36 milliseconds, and no intervals are ever more than 5 milliseconds away from the expected 35.7142857143. During the "glitchy" stretches, the distribution of intervals is very nearly identical, except that a very small number are unusually large (a couple more than 60 ms and one or two longer than 100 ms during maybe a 3-second stretch). This stuttering is very noticeable, and it's what I'm trying to fix, if possible. For the high-resolution timer, I was using the extremely antique timeSetEvent() multimedia timer from winmm.dll. In pursuit of this problem, I switched to using CreateTimerQueueTimer (along with timeBeginPeriod to set the high-resolution), but I'm seeing the same problem with both timer mechanisms. I've tried experimenting with the various flags for CreateTimerQueueTimer which determine which thread the timer runs on, but the stuttering appears no matter what. Is this just a fundamental problem with using timers in this way (i.e. using each one-shot timer to call the next)? If so, do I have any alternatives? One thing I was considering was to determine how many consecutive 1-millisecond-accuracy ticks would keep my within some arbitrary precision limit before I need to reset the timer. So, for example, if I wanted a 35.71428 period, I could let a 36 ms timer elapse 15 times before it was off by 5 milliseconds, then kill it and start a new one.

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• MVVM pattern and nested view models - communication and lookup lists

  - by LostInWPF

  I am using Prism for a new application that I am creating. There are several lookup lists that will be used in several places in the application. Therefore it makes sense to define it once and use that everywhere I need that functionality. My current solution is to use typed data templates to render the controls inside a content control. <DataTemplate DataType={x:Type ListOfCountriesViewModel}> <ComboBox ItemsSource={Binding Countries} SelectedItem="{Binding SelectedCountry"/> </DataTemplate> <DataTemplate DataType={x:Type ListOfRegionsViewModel}> <ComboBox ItemsSource={Binding Countries} SelectedItem={Binding SelectedRegion} /> </DataTemplate> public class ParentViewModel { SelectedCountry get; set; SelectedRegion get; set; ListOfCountriesViewModel CountriesVM; ListOfRegionsViewModel RgnsVM; } Then in my window I have 2 content controls and the rest of the controls <ContentControl Content="{Binding CountriesVM}"></ContentControl> <ContentControl Content="{Binding RgnsVM}"></ContentControl> <Rest of controls on view> At the moment I have this working and the SelectedItems for the combo boxes are publising events via EventAggregator from the child view models which are then subscribed to in the parent view model. I am not sure that this is the best way to go as I can imagine I would end up with a lot of events very quickly and it will become unwieldy. Also if I was to use the same view model on another window it will publish the event and this parent viewmodel is subscribed to it which could have unintended consequences. My questions are :- Is this the best way to put lookup lists in a view which can be re-used across screens? How do I make it so that the combobox which is bound to the child viewmodel sets the relevant property on the parent viewmodel without using events / mediator. e.g in this case SelectedCountry for example? Any alternative implementation proposals for what I am trying to do? I have a feeling I am missing something obvious and there is so much info it is hard to know what is right so any help would be most gratefully received.

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• Android GPS timeout

  - by Scott Saunders

  I'm writing an Android application that, among other things, needs to send the current GPS coordinates to a server when the user tells it to. From a context menu, I run the service below. The service is a LocationListener and requests updates from the LocationManager. When it gets a location (onLocationChanged()), it removes itself as a listener and sends the coordinates off to the server. All of this is working. However, if GPS coordinates are not quickly available, my service just keeps running until it gets some. It holds up the UI with a progress dialog, which is annoying. Worse, if the user has moved since starting the service, the first GPS coordinates might be wrong and the app will send bad data to the server. I need a timeout on the service. Is there a good way to do that? I'm not very experienced with threads. I think I can run a Runnable in the onStartCommand() method that will somehow count down 30 seconds and then, if there is no GPS result yet, call my service's stop() method. Does that sound like the best way to do this? Alternatively, is it possible to tell if the GPS cannot get a fix? How would I go about doing that? Edit: To further clarify, I'm looking for the best way to "give up" on getting a Location after some amount of time. public class AddCurrentLocation extends Service implements LocationListener { Application app; LocationManager mLocManager; ProgressDialog mDialog; @Override public int onStartCommand(Intent intent, int arg0, int arg1) { app = getApplication(); // show progress dialog if (app.getScreen() != null) { mDialog = ProgressDialog.show(app.getScreen(), "", "Adding Location. Please wait...", true); } // find GPS service and start listening Criteria criteria = new Criteria(); criteria.setAccuracy(Criteria.ACCURACY_FINE); mLocManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE); String bestProvider = mLocManager.getBestProvider(criteria, true); mLocManager.requestLocationUpdates(bestProvider, 2000, 0, this); return START_NOT_STICKY; } private void stop() { mLocManager.removeUpdates(this); if (mDialog != null) { mDialog.dismiss(); } stopSelf(); } @Override public void onLocationChanged(Location location) { // done with GPS stop listening mLocManager.removeUpdates(this); sendLocation(location); // method to send info to server stop(); } // other required methods and sendLocation() ... }

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• Progress gauge in status bar, using Cody Precord's ProgressStatusBar

  - by MCXXIII

  Hi. I am attempting to create a progress gauge in the status bar for my application, and I'm using the example in Cody Precord's wxPython 2.8 Application Development Cookbook. I've reproduced it below. For now I simply wish to show the gauge and have it pulse when the application is busy, so I assume I need to use the Start/StopBusy() methods. Problem is, none of it seems to work, and the book doesn't provide an example of how to use the class. In the __init__ of my frame I create my status bar like so: self.statbar = status.ProgressStatusBar( self ) self.SetStatusBar( self.statbar ) Then, in the function which does all the work, I have tried things like: self.GetStatusBar().SetRange( 100 ) self.GetStatusBar().SetProgress( 0 ) self.GetStatusBar().StartBusy() self.GetStatusBar().Run() # work done here self.GetStatusBar().StopBusy() And several combinations and permutations of those commands, but nothing happens, no gauge is ever shown. The work takes several seconds, so it's not because the gauge simply disappears again too quickly for me to notice. I can get the gauge to show up by removing the self.prog.Hide() line from Precord's __init__ but it still doesn't pulse and simply disappears never to return once work has finished the first time. Here's Precord's class: class ProgressStatusBar( wx.StatusBar ): '''Custom StatusBar with a built-in progress bar''' def __init__( self, parent, id_=wx.ID_ANY, style=wx.SB_FLAT, name='ProgressStatusBar' ): super( ProgressStatusBar, self ).__init__( parent, id_, style, name ) self._changed = False self.busy = False self.timer = wx.Timer( self ) self.prog = wx.Gauge( self, style=wx.GA_HORIZONTAL ) self.prog.Hide() self.SetFieldsCount( 2 ) self.SetStatusWidths( [-1, 155] ) self.Bind( wx.EVT_IDLE, lambda evt: self.__Reposition() ) self.Bind( wx.EVT_TIMER, self.OnTimer ) self.Bind( wx.EVT_SIZE, self.OnSize ) def __del__( self ): if self.timer.IsRunning(): self.timer.Stop() def __Reposition( self ): '''Repositions the gauge as necessary''' if self._changed: lfield = self.GetFieldsCount() - 1 rect = self.GetFieldRect( lfield ) prog_pos = (rect.x + 2, rect.y + 2) self.prog.SetPosition( prog_pos ) prog_size = (rect.width - 8, rect.height - 4) self.prog.SetSize( prog_size ) self._changed = False def OnSize( self, evt ): self._changed = True self.__Reposition() evt.Skip() def OnTimer( self, evt ): if not self.prog.IsShown(): self.timer.Stop() if self.busy: self.prog.Pulse() def Run( self, rate=100 ): if not self.timer.IsRunning(): self.timer.Start( rate ) def GetProgress( self ): return self.prog.GetValue() def SetProgress( self, val ): if not self.prog.IsShown(): self.ShowProgress( True ) if val == self.prog.GetRange(): self.prog.SetValue( 0 ) self.ShowProgress( False ) else: self.prog.SetValue( val ) def SetRange( self, val ): if val != self.prog.GetRange(): self.prog.SetRange( val ) def ShowProgress( self, show=True ): self.__Reposition() self.prog.Show( show ) def StartBusy( self, rate=100 ): self.busy = True self.__Reposition() self.ShowProgress( True ) if not self.timer.IsRunning(): self.timer.Start( rate ) def StopBusy( self ): self.timer.Stop() self.ShowProgress( False ) self.prog.SetValue( 0 ) self.busy = False def IsBusy( self ): return self.busy

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• Android "Trying to use recycled bitmap" error?

  - by Mike

  Hi all, I am running into a problem with bitmaps on an Android application I am working on. What is suppose to happen is that the application downloads images from a website, saves them to the device, loads them into memory as bitmaps into an arraylist, and displays them to the user. This all works fine when the application is first started. However, I have added a refresh option for the user where the images are deleted, and the process outlined above starts all over. My problem: By using the refresh option the old images were still in memory and I would quickly get OutOfMemoryErrors. Thus, if the images are being refreshed, I had it run through the arraylist and recycle the old images. However, when the application goes to load the new images into the arraylist, it crashes with a "Trying to use recycled bitmap" error. As far as I understand it, recycling a bitmap destroys the bitmap and frees up its memory for other objects. If I want to use the bitmap again, it has to be reinitialized. I believe that I am doing this when the new files are loaded into the arraylist, but something is still wrong. Any help is greatly appreciated as this is very frustrating. The problem code is below. Thank you! public void fillUI(final int refresh) { // Recycle the images to avoid memory leaks if(refresh==1) { for(int x=0; x<images.size(); x++) images.get(x).recycle(); images.clear(); selImage=-1; // Reset the selected image variable } final ProgressDialog progressDialog = ProgressDialog.show(this, null, this.getString(R.string.loadingImages)); // Create the array with the image bitmaps in it new Thread(new Runnable() { public void run() { Looper.prepare(); File[] fileList = new File("/data/data/[package name]/files/").listFiles(); if(fileList!=null) { for(int x=0; x<fileList.length; x++) { try { images.add(BitmapFactory.decodeFile("/data/data/[package name]/files/" + fileList[x].getName())); } catch (OutOfMemoryError ome) { Log.i(LOG_FILE, "out of memory again :("); } } Collections.reverse(images); } fillUiHandler.sendEmptyMessage(0); } }).start(); fillUiHandler = new Handler() { public void handleMessage(Message msg) { progressDialog.dismiss(); } }; }

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• Existing web-site CSS replacement (re-skinning) best-practices without changing the HTML

  - by Enigmativity

  I can see a number of other good answers to questions relating to CSS best-practices on stack overflow: How to Manage CSS Explosion CSS Conventions / Code Layout Models Are there any CSS standards that I should follow while writing my first stylesheet? What is the best method for tidying CSS? Best Practices - CSS Stylesheet Formatting But I think I have a different problem. I'm trying to "re-skin" an existing site that has been nicely built using div's and ul's, etc, and it has a good existing CSS file, but when I start making changes to the CSS I quickly find that I break the layout. My feeling is that it is very hard to get a feel for how all the CSS will work together and indeed what CSS is affecting parent and sibling elements in the HTML. So, my question is "what are the best-practices around re-skinning an existing web-site by replacing the CSS only and not modifying the existing HTML?" I can't change the classes, ids, node hierarchy, etc. An example of the particular site that I am trying to re-skin is http://demo.nopcommerce.com/. The existing CSS can be as complicated/detailed as this extract from the main CSS file: .header-selectors-wrapper { text-align: right; float: right; width: 500px; } .header-currencyselector { float: right; } .header-languageselector { float: left; } .header-taxDisplayTypeSelector { float: right; } .header-links-wrapper { float: right; text-align: right; width: 570px; } .header-links { border: solid 1px #9a9a9a; padding: 5px 5px 5px 5px; margin-bottom: 5px; display: inline-table; } .order-summary-content .cart .cart-item-row td, .wishlist-content .cart .cart-item-row td { border-bottom: 1px solid #c5c5c5; vertical-align: middle; line-height: 30px; } .order-summary-content .cart .cart-item-row td.product, .wishlist-content .cart .cart-item-row td.product { text-align: left; padding: 0px 10px 0px 10px; } .order-summary-content .cart .cart-item-row td.product a, .wishlist-content .cart .cart-item-row td.product a { font-weight: bold; } Any help would be appreciated.

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