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  • KVM Virtual guest Paused on Reboot

    - by David Hamilton
    I'm running REHL 6 and just installed a Ubuntu Server Guest via KVM set to start at boot. This works correctly and the guest loads, but it loads "paused" and requires that I manually un-pause it. Can someone give me a hint as to how I can I get the Guest OS to actually become active on boot? Here is the libvert dump as requested...Also tried libvert auto-start --- no effect. <domain type='kvm' id='1'> <name>MailServer</name> <uuid>a61dae75-1f5c-d536-718f-3c615d9b4868</uuid> <memory>4194304</memory> <currentMemory>4194304</currentMemory> <vcpu>4</vcpu> <os> <type arch='x86_64' machine='rhel6.0.0'>hvm</type> <boot dev='hd'/> </os> <features> <acpi/> <apic/> <pae/> </features> <clock offset='utc'/> <on_poweroff>destroy</on_poweroff> <on_reboot>restart</on_reboot> <on_crash>restart</on_crash> <devices> <emulator>/usr/libexec/qemu-kvm</emulator> <disk type='file' device='disk'> <driver name='qemu' type='raw' cache='none'/> <source file='/home/MailServer/MailServer-1.img'/> <target dev='hda' bus='ide'/> <alias name='ide0-0-0'/> <address type='drive' controller='0' bus='0' unit='0'/> </disk> <disk type='block' device='cdrom'> <driver name='qemu' type='raw'/> <target dev='hdc' bus='ide'/> <readonly/> <alias name='ide0-1-0'/> <address type='drive' controller='0' bus='1' unit='0'/> </disk> <controller type='ide' index='0'> <alias name='ide0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/> </controller> <interface type='bridge'> <mac address='52:54:00:cd:f9:9f'/> <source bridge='br0'/> <target dev='vnet0'/> <model type='virtio'/> <alias name='net0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/> </interface> <serial type='pty'> <source path='/dev/pts/1'/> <target port='0'/> <alias name='serial0'/> </serial> <console type='pty' tty='/dev/pts/1'> <source path='/dev/pts/1'/> <target port='0'/> <alias name='serial0'/> </console> <input type='mouse' bus='ps2'/> <graphics type='vnc' port='5900' autoport='yes'/> <sound model='ac97'> <alias name='sound0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/> </sound> <video> <model type='cirrus' vram='9216' heads='1'/> <alias name='video0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/> </video> <memballoon model='virtio'> <alias name='balloon0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/> </memballoon> </devices> <seclabel type='dynamic' model='selinux'> <label>system_u:system_r:svirt_t:s0:c211,c271</label> <imagelabel>system_u:object_r:svirt_image_t:s0:c211,c271</imagelabel> </seclabel></domain>

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  • SharePoint 2010 Single Page Apps without a Master Page

    - by David Jacobus
    Originally posted on: http://geekswithblogs.net/djacobus/archive/2014/06/06/156827.aspxWell, maybe a stretch, but I am inclined to believe it is so.  I have been using  the JavaScript Client Object Model (JCSOM) for about 6 months now and I believe it can do about 80% of my job quickly without much fanfare.  When building sites in SharePoint no one wants the OOTB list views, etc. They want a custom look and feel!  I used to think in previous engagements that this would mean some custom server code or at least a data-form web part.   Since coming on-board in my current engagement, I have been forced because we don’t own the hosting site to come up with innovative ways to customize the UI of SharePoint.  We can push content via sandbox solutions and use JCSOM from within SharePoint Designer to do almost all customizations.  I have been using the following methodology to accomplish this: 1. Create an HTML file, which links CSS and JavaScript Files 2. Create and ASPX Web Part Page, Include a Content Editor Web Part and link to the HTML page created above.   So basically once it was done, I could copy , paste,  and rename those 4 items: CC, JS, HTML. ASPX and using MVVM just change the Model, View, and View-Model in the JavaScript file.  in about 5 minutes, I could create a completely new web part with SharePoint data.  Styling would take a little longer.  Some issues that would crop up: 1.  Multiple(s) of these web parts would not work well together on the same page (context). 2.  To separate the Web parts and context I would create a separate page for each web part and link them to a tabs layout via a Page Viewer web part or I frame.  Easy to do and not a problem but a big load problem as these web part pages even with minimal master had huge footprints.  (master page and page web part zones)   I kept thinking of my experience with SharePoint 2013 and apps!  The JavaScript was loaded from within the app, why can’t we do that in 2010 and skip the master page and web part zones. I thought at first, just link to sp.js but that didn’t work so I searched the web and found a link which did not work at all in my environment but helped me create a solution that would kudos to (Will). <!DOCTYPE html> <%@ Page %> <%@ Register Tagprefix="SharePoint" Namespace="Microsoft.SharePoint.WebControls" Assembly="Microsoft.SharePoint, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %> <%@ Import Namespace="Microsoft.SharePoint" %> <html> <head> <link rel="Stylesheet" type="text/css" href="../CSS/smoothness/jquery-ui-1.10.4.custom.min.css"> </head> <body > <form runat="server"> <!-- the following 5 js files are required to use CSOM --> <script src="/_layouts/1033/init.js" type="text/javascript" ></script> <script src="/_layouts/MicrosoftAjax.js" type="text/javascript" ></script> <script src="/_layouts/sp.core.js" type="text/javascript" ></script> <script src="/_layouts/sp.runtime.js" type="text/javascript" ></script> <script src="/_layouts/sp.js" type="text/javascript" ></script> <!-- include your app code --> <script src="../scripts/jquery-1.9.1.js" type="text/javascript" ></script> <script src="../Scripts/jquery-ui-1.10.3.custom.min.js" type="text/javascript"></script> <script src="../scripts/App.js" type="text/javascript" ></script> <div ID="Wrapper"> </div> <SharePoint:FormDigest ID="FormDigest1" runat="server"></SharePoint:FormDigest> </form> </body> </html> Notice that I have the scripts loaded within the body! I discovered this by accident in trying to get Will’s solution to work, it made this work just like normal JCSOM from the master page.  I am sure there are other ways to do this, but I am a full time developer, so I’ll let someone else investigate the alternatives.  I have an example page showing an Announcements list as a Booklet which is a JQuery Plug-In.  Here is the page source notice the footprint is light.   <!DOCTYPE html> <html> <head> <link rel="Stylesheet" type="text/css" href="../CSS/smoothness/jquery-ui-1.10.4.custom.min.css"> <link href="../CSS/jquery.booklet.latest.css" type="text/css" rel="stylesheet" media="screen, projection, tv" /> <link href="../CSS/bookletannouncement.css" type="text/css" rel="stylesheet" media="screen, projection, tv" /> </head> <body > <form name="ctl00" method="post" action="BookletAnnouncements2.aspx" onsubmit="javascript:return WebForm_OnSubmit();" id="ctl00"> <div> <input type="hidden" name="__REQUESTDIGEST" id="__REQUESTDIGEST" value="0x3384922A8349572E3D76DC68A3F7A0984CEC14CB9669817CCA584681B54417F7FDD579F940335DCEC95CFFAC78ADDD60420F7AA82F60A8BC1BB4B9B9A57F9309,06 Jun 2014 14:13:27 -0000" /> <input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="/wEPDwUBMGRk20t+bh/NWY1sZwphwb24pIxjUbo=" /> </div> <script type="text/javascript"> //<![CDATA[ var g_presenceEnabled = true;var _fV4UI=true;var _spPageContextInfo = {webServerRelativeUrl: "\u002fsites\u002fDemo50\u002fTeamSite", webLanguage: 1033, currentLanguage: 1033, webUIVersion:4,pageListId:"{ee707b5f-e246-4246-9e55-8db11d09a8cb}",pageItemId:167,userId:1, alertsEnabled:false, siteServerRelativeUrl: "\u002fsites\u002fdemo50", allowSilverlightPrompt:'True'};//]]> </script> <script type="text/javascript" src="/_layouts/1033/init.js?rev=lEi61hsCxcBAfvfQNZA%2FsQ%3D%3D"></script> <script type="text/javascript"> //<![CDATA[ function WebForm_OnSubmit() { UpdateFormDigest('\u002fsites\u002fDemo50\u002fTeamSite', 1440000); return true; } //]]> </script> <!-- the following 5 js files are required to use CSOM --> <script src="/_layouts/1033/init.js"></script> <script src="/_layouts/MicrosoftAjax.js"></script> <script src="/_layouts/sp.core.js"></script> <script src="/_layouts/sp.runtime.js"></script> <script src="/_layouts/sp.js"></script> <!-- include your app code --> <script src="../scripts/jquery-1.9.1.js"></script> <script src="../Scripts/jquery-ui-1.10.3.custom.min.js" type="text/javascript"></script> <script src="../Scripts/jquery.easing.1.3.js"></script> <script src="../Scripts/jquery.booklet.latest.min.js"></script> <script src="../scripts/Announcementsbooklet.js"></script> <div ID="Accord"> </div> <script type="text/javascript"> //<![CDATA[ var _spFormDigestRefreshInterval = 1440000;//]]> </script> </form> </body> </html> Here is the source to make the booklet work: ExecuteOrDelayUntilScriptLoaded(retrieveListItems, "sp.js"); var context; var collListItem; var web; var listRootFolder; var oList; //retieve the list items from the host web function retrieveListItems() { context = SP.ClientContext.get_current(); web = context.get_web(); oList = context.get_web().get_lists().getByTitle('Announcements'); var camlQuery = new SP.CamlQuery(); camlQuery.set_viewXml('<View><RowLimit>10</RowLimit></View>'); collListItem = oList.getItems(camlQuery); listRootFolder = oList.get_rootFolder(); context.load(listRootFolder); context.load(web); context.load(collListItem); context.executeQueryAsync(onQuerySucceeded, onQueryFailed); } //Model object var Dev = function (id, title, body, expires, url) { var self = this; self.ID = id; self.Title = title; self.Body = body; self.Expires = expires; self.Url = url; } //View model var DevVM = new ListViewModel() function ListViewModel() { var self = this; self.items = new Array(); } function onQuerySucceeded(sender, args) { var listItemEnumerator = collListItem.getEnumerator(); while (listItemEnumerator.moveNext()) { var oListItem = listItemEnumerator.get_current(); var javaDate = oListItem.get_item('Expires'); var fmtExpires = javaDate.format('dd MMM yyyy'); var url = ""; var goodUrl = oListItem.get_item('Url'); if (goodUrl == null) { url = web.get_serverRelativeUrl() + "/Lists/Announcements/EditForm.aspx?ID=" + oListItem.get_item('ID'); } else { url = web.get_serverRelativeUrl() + oListItem.get_item('Url') } DevVM.items.push(new Dev(oListItem.get_item('ID'), oListItem.get_item('Title'), oListItem.get_item('Body'), fmtExpires, url)); } $.each(DevVM.items, function (index) { $("#Accord").append(createAccordNode(DevVM.items[index].Title, DevVM.items[index].Body, " Expires: " + DevVM.items[index].Expires, DevVM.items[index].Url)); }); $("#Accord").booklet(); } function createAccordNode(title, body, expires, url) { return ( $("<div><h3>" + title + "</h3><p><span class='titlespan'><a href='" + url + "'>" + title + "</a></span><span class='dicussionspan'>" + body + "</span><span class='expiresspan'>" + expires + "</span></p></div>") ); } function onQueryFailed(sender, args) { alert('Request failed. ' + args.get_message() + '\n' + args.get_stackTrace()); } The idea behind this post is that this could be used to: 1.   Create landing pages that are very un-SharePoint like! 2.   Make lightweight pages that could be used in page viewer web part or I Frame. 3.  Utilize Deep Zoom Composer and Sea-Dragon/or Silver light I will be using this for much of my development work!

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  • Do you know what is a DevOps Project?

    - by Gopinath
    Yesterday I wrote about OpenStack project, an open source cloud computing stack that lets you build Cloud Computing environments. While reading more on this topic I stumbled about a new type of projects called DevOps projects.  OpenStack is all set to become the first DevOps project, reports Forbes …the way OpenStack is applying the open source model to creating cloud infrastructure, the open source model is on the verge of being extended so that the collaboration and design process will include software, hardware, and networking in the data center as well as operational processes. In modern development, the idea of designing software, data center, and operations using one integrated team is called DevOps.

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  • Weblogic Virtual Developer Day Reminder - Feb 1 @ 9:30am PT

    - by Cassandra Clark
    Don't forget to register and attend the next Oracle Technology Network Virtual Developer Day- Weblogic Server tomorrow starting at 9:30 am PST. Learn how Oracle WebLogic Server enables a whole new level of productivity for enterprise developers. Also hear the latest on Java EE 6 and the programming tenets that have made it a true platform breakthrough, with new programming paradigms, persistence strategies, and more: * Convention over configuration - minimal XML * Leaner and meaner API - and one that is an open standard * POJO model - managed beans for testable components * Annotation-based programming model - decorate and inject * Reduce or eliminate need for deployment descriptors * Traditional API for advanced users We will have three live events - N. America - Tuesday, Feb 1, 2011 09:30 a.m. - 1:30 p.m. US Pacific TIme Register Europe / Russia - February 10, 2011 9:30 a.m. UK Time / 10:30 a.m. CET Register India - February 17, 2011 9:30 a.m. India time Register

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  • Should custom data elements be stored as XML or database entries?

    - by meteorainer
    There are a ton of questions like this, but they are mostly very generalized, so I'd like to get some views on my specific usage. General: I'm building a new project on my own in Django. It's focus will be on small businesses. I'd like to make it somewhat customizble for my clients so they can add to their customer/invoice/employee/whatever items. My models would reflect boilerplate items that all ModelX might have. For example: first name last name email address ... Then my user's would be able to add fields for whatever data they might like. I'm still in design phase and am building this myself, so I've got some options. Working on... Right now the 'extra items' models have a FK to the generic model (Customer and CustomerDataPoints for example). All values in the extra data points are stored as char and will be coerced/parced into their actual format at view building. In this build the user could theoretically add whatever values they want, group them in sets and generally access them at will from the views relavent to that model. Pros: Low storage overhead, very extensible, searchable Cons: More sql joins My other option is to use some type of markup, or key-value pairing stored directly onto the boilerplate models. This coul essentially just be any low-overhead method weather XML or literal strings. The view and form generated from the stored data would be taking control of validation and reoganizing on updates. Then it would just dump the data back in as a char/blob/whatever. Something like: <datapoint type='char' value='something' required='true' /> <datapoint type='date' value='01/01/2001' required='false' /> ... Pros: No joins needed, Updates for validation and views are decoupled from data Cons: Much higher storage overhead, limited capacity to search on extra content So my question is: If you didn't live in the contraints impose by your company what method would you use? Why? What benefits or pitfalls do you see down the road for me as a small business trying to help other small businesses? Just to clarify, I am not asking about custom UI elements, those I can handle with forms and template snippets. I'm asking primarily about data storage and retreival of non standardized data relative to a boilerplate model.

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  • Game engine design: Multiplayer and listen servers

    - by jarx
    My game engine right now consists of a working singleplayer part. I'm now starting to think about how to do the multiplayer part. I have found out that many games actually don't have a real singleplayer mode, but when playing alone you are actually hosting a local server as well, and almost everything runs as if you were in multiplayer (except that the data packets can be passed over an alternate route for better performance) My engine would need major refactoring to adapt to this model. There would be three possible modes: Dedicated client, Dedicated server and Client-Server (listen mode) * How often is the listen-server model used in the gaming industry? * What are the (dis)advantages of it? * What other options do I have?

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  • Copyright of pictures upload to a website?

    - by All
    I want to run a website like stock photos. How can I be sure that the uploader is real copyright holder of the picture? Is it possible to leave the responsibility of this copyright claim to the uploader or at last the webmaster is responsible for the website content? It generally confuses me, as for example, stock photo websites needs form signed by the model for photos showing human face. How they can be sure that the signature actually belongs to the model? How they keep them safe from possible lawsuit in this case (e.g. if selling photos of a models with a fake signature?)

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  • ASP.Net MVC Interview Questions and Answers

    - by Samir R. Bhogayta
    About ASP.Net MVC The ASP.Net MVC is the framework provided by Microsoft that lets you develop the applications that follows the principles of Model-View-Controller (MVC) design pattern. The .Net programmers new to MVC thinks that it is similar to WebForms Model (Normal ASP.Net), but it is far different from the WebForms programming.  This article will tell you how to quick learn the basics of MVC along with some frequently asked interview questions and answers on ASP.Net MVC 1. What is ASP.Net MVC The ASP.Net MVC is the framework provided by Microsoft to achieve     separation of concerns that leads to easy maintainability of the     application. Model is supposed to handle data related activity View deals with user interface related work Controller is meant for managing the application flow by communicating between Model and View. Normal 0 false false false EN-US X-NONE X-NONE 2. Why to use ASP.Net MVC The strength of MVC (i.e. ASP.Net MVC) listed below will answer this question MVC reduces the dependency between the components; this makes your code more testable. MVC does not recommend use of server controls, hence the processing time required to generate HTML response is drastically reduced. The integration of java script libraries like jQuery, Microsoft MVC becomes easy as compared to Webforms approach. 3. What do you mean by Razor The Razor is the new View engine introduced in MVC 3.0. The View engine is responsible for processing the view files [e.g. .aspx, .cshtml] in order to generate HTML response. The previous versions of MVC were dependent on ASPX view engine.  4. Can we use ASPX view engine in latest versions of MVC Yes. The Recommended way is to prefer Razor View 5. What are the benefits of Razor View?      The syntax for server side code is simplified      The length of code is drastically reduced      Razor syntax is easy to learn and reduces the complexity Normal 0 false false false EN-US X-NONE 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-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;} 6. What is the extension of Razor View file? .cshtml (for c#) and .vbhtml (for vb) 7. How to create a Controller in MVC Normal 0 false false false EN-US X-NONE 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-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;} Create a simple class and extend it from Controller class. The bare minimum requirement for a class to become a controller is to inherit it from ControllerBase is the class that is required to inherit to create the controller but Controller class inherits from ControllerBase. 8. How to create an Action method in MVC Add a simple method inside a controller class with ActionResult return type. 9. How to access a view on the server    The browser generates the request in which the information like Controller name, Action Name and Parameters are provided, when server receives this URL it resolves the Name of Controller and Action, after that it calls the specified action with provided parameters. Action normally does some processing and returns the ViewResult by specifying the view name (blank name searches according to naming conventions).   10. What is the default Form method (i.e. GET, POST) for an action method GET. To change this you can add an action level attribute e.g [HttpPost] Normal 0 false false false EN-US X-NONE 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-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;} 11. What is a Filter in MVC? When user (browser) sends a request to server an action method of a controller gets invoked; sometimes you may require executing a custom code before or after action method gets invoked, this custom code is called as Filter. 12. What are the different types of Filters in MVC? a. Authorization filter b. Action filter c. Result filter d. Exception filter [Do not forget the order mentioned above as filters gets executed as per above mentioned sequence] 13. Explain the use of Filter with an example? Suppose you are working on a MVC application where URL is sent in an encrypted format instead of a plain text, once encrypted URL is received by server it will ignore action parameters because of URL encryption. To solve this issue you can create global action filter by overriding OnActionExecuting method of controller class, in this you can extract the action parameters from the encrypted URL and these parameters can be set on filterContext to send plain text parameters to the actions.     14. What is a HTML helper? A HTML helper is a method that returns string; return string usually is the HTML tag. The standard HTML helpers (e.g. Html.BeginForm(),Html.TextBox()) available in MVC are lightweight as it does not rely on event model or view state as that of in ASP.Net server controls.

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  • When attempting to install ubuntu 12.04 from CD, I am stuck on black streen with "loading bootlogo..."

    - by Jessica K
    I downloaded Ubuntu 12.04 to my desktop and burned to a CD using Infra Recorder and instructions on ubuntu website. Restarted PC to boot from CD receive black screen with "Loading bootlogo..." then nothing happens and I have to restart with windows. The CD seems to be correct. Folders include .disk, boot, casper, dists, install, isolinux, pics, pool, preseed, autorun file, md5sum text file, readme.diskdefines file, wubi app. System Information Operating System: Windows Vista™ Home Premium (6.0, Build 6002) Service Pack 2 (6002.vistasp2_gdr.120824-0336) System Manufacturer: TOSHIBA System Model: Satellite L305 BIOS: Default System BIOS Processor: Intel(R) Pentium(R) Dual CPU T2390 @ 1.86GHz (2 CPUs), ~1.9GHz Memory: 3062MB RAM Page File: 1553MB used, 4772MB available Windows Dir: C:\Windows DirectX Version: DirectX 11 DX Setup Parameters: Not found DxDiag Version: 7.00.6002.18107 32bit Unicode Drive: D: Model: PIONEER DVD-RW DVRKD08L ATA Device Driver: c:\windows\system32\drivers\cdrom.sys, 6.00.6002.18005 (English), 4/11/2009 00:39:17, 67072 bytes

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  • Of transactions and Mongo

    - by Nuri Halperin
    Originally posted on: http://geekswithblogs.net/nuri/archive/2014/05/20/of-transactions-and-mongo-again.aspxWhat's the first thing you hear about NoSQL databases? That they lose your data? That there's no transactions? No joins? No hope for "real" applications? Well, you *should* be wondering whether a certain of database is the right one for your job. But if you do so, you should be wondering that about "traditional" databases as well! In the spirit of exploration let's take a look at a common challenge: You are a bank. You have customers with accounts. Customer A wants to pay B. You want to allow that only if A can cover the amount being transferred. Let's looks at the problem without any context of any database engine in mind. What would you do? How would you ensure that the amount transfer is done "properly"? Would you prevent a "transaction" from taking place unless A can cover the amount? There are several options: Prevent any change to A's account while the transfer is taking place. That boils down to locking. Apply the change, and allow A's balance to go below zero. Charge person A some interest on the negative balance. Not friendly, but certainly a choice. Don't do either. Options 1 and 2 are difficult to attain in the NoSQL world. Mongo won't save you headaches here either. Option 3 looks a bit harsh. But here's where this can go: ledger. See, and account doesn't need to be represented by a single row in a table of all accounts with only the current balance on it. More often than not, accounting systems use ledgers. And entries in ledgers - as it turns out – don't actually get updated. Once a ledger entry is written, it is not removed or altered. A transaction is represented by an entry in the ledger stating and amount withdrawn from A's account and an entry in the ledger stating an addition of said amount to B's account. For sake of space-saving, that entry in the ledger can happen using one entry. Think {Timestamp, FromAccountId, ToAccountId, Amount}. The implication of the original question – "how do you enforce non-negative balance rule" then boils down to: Insert entry in ledger Run validation of recent entries Insert reverse entry to roll back transaction if validation failed. What is validation? Sum up the transactions that A's account has (all deposits and debits), and ensure the balance is positive. For sake of efficiency, one can roll up transactions and "close the book" on transactions with a pseudo entry stating balance as of midnight or something. This lets you avoid doing math on the fly on too many transactions. You simply run from the latest "approved balance" marker to date. But that's an optimization, and premature optimizations are the root of (some? most?) evil.. Back to some nagging questions though: "But mongo is only eventually consistent!" Well, yes, kind of. It's not actually true that Mongo has not transactions. It would be more descriptive to say that Mongo's transaction scope is a single document in a single collection. A write to a Mongo document happens completely or not at all. So although it is true that you can't update more than one documents "at the same time" under a "transaction" umbrella as an atomic update, it is NOT true that there' is no isolation. So a competition between two concurrent updates is completely coherent and the writes will be serialized. They will not scribble on the same document at the same time. In our case - in choosing a ledger approach - we're not even trying to "update" a document, we're simply adding a document to a collection. So there goes the "no transaction" issue. Now let's turn our attention to consistency. What you should know about mongo is that at any given moment, only on member of a replica set is writable. This means that the writable instance in a set of replicated instances always has "the truth". There could be a replication lag such that a reader going to one of the replicas still sees "old" state of a collection or document. But in our ledger case, things fall nicely into place: Run your validation against the writable instance. It is guaranteed to have a ledger either with (after) or without (before) the ledger entry got written. No funky states. Again, the ledger writing *adds* a document, so there's no inconsistent document state to be had either way. Next, we might worry about data loss. Here, mongo offers several write-concerns. Write-concern in Mongo is a mode that marshals how uptight you want the db engine to be about actually persisting a document write to disk before it reports to the application that it is "done". The most volatile, is to say you don't care. In that case, mongo would just accept your write command and say back "thanks" with no guarantee of persistence. If the server loses power at the wrong moment, it may have said "ok" but actually no written the data to disk. That's kind of bad. Don't do that with data you care about. It may be good for votes on a pole regarding how cute a furry animal is, but not so good for business. There are several other write-concerns varying from flushing the write to the disk of the writable instance, flushing to disk on several members of the replica set, a majority of the replica set or all of the members of a replica set. The former choice is the quickest, as no network coordination is required besides the main writable instance. The others impose extra network and time cost. Depending on your tolerance for latency and read-lag, you will face a choice of what works for you. It's really important to understand that no data loss occurs once a document is flushed to an instance. The record is on disk at that point. From that point on, backup strategies and disaster recovery are your worry, not loss of power to the writable machine. This scenario is not different from a relational database at that point. Where does this leave us? Oh, yes. Eventual consistency. By now, we ensured that the "source of truth" instance has the correct data, persisted and coherent. But because of lag, the app may have gone to the writable instance, performed the update and then gone to a replica and looked at the ledger there before the transaction replicated. Here are 2 options to deal with this. Similar to write concerns, mongo support read preferences. An app may choose to read only from the writable instance. This is not an awesome choice to make for every ready, because it just burdens the one instance, and doesn't make use of the other read-only servers. But this choice can be made on a query by query basis. So for the app that our person A is using, we can have person A issue the transfer command to B, and then if that same app is going to immediately as "are we there yet?" we'll query that same writable instance. But B and anyone else in the world can just chill and read from the read-only instance. They have no basis to expect that the ledger has just been written to. So as far as they know, the transaction hasn't happened until they see it appear later. We can further relax the demand by creating application UI that reacts to a write command with "thank you, we will post it shortly" instead of "thank you, we just did everything and here's the new balance". This is a very powerful thing. UI design for highly scalable systems can't insist that the all databases be locked just to paint an "all done" on screen. People understand. They were trained by many online businesses already that your placing of an order does not mean that your product is already outside your door waiting (yes, I know, large retailers are working on it... but were' not there yet). The second thing we can do, is add some artificial delay to a transaction's visibility on the ledger. The way that works is simply adding some logic such that the query against the ledger never nets a transaction for customers newer than say 15 minutes and who's validation flag is not set. This buys us time 2 ways: Replication can catch up to all instances by then, and validation rules can run and determine if this transaction should be "negated" with a compensating transaction. In case we do need to "roll back" the transaction, the backend system can place the timestamp of the compensating transaction at the exact same time or 1ms after the original one. Effectively, once A or B visits their ledger, both transactions would be visible and the overall balance "as of now" would reflect no change.  The 2 transactions (attempted/ reverted) would be visible , since we do actually account for the attempt. Hold on a second. There's a hole in the story: what if several transfers from A to some accounts are registered, and 2 independent validators attempt to compute the balance concurrently? Is there a chance that both would conclude non-sufficient-funds even though rolling back transaction 100 would free up enough for transaction 117 (some random later transaction)? Yes. there is that chance. But the integrity of the business rule is not compromised, since the prime rule is don't dispense money you don't have. To minimize or eliminate this scenario, we can also assign a single validation process per origin account. This may seem non-scalable, but it can easily be done as a "sharded" distribution. Say we have 11 validation threads (or processing nodes etc.). We divide the account number space such that each validator is exclusively responsible for a certain range of account numbers. Sounds cunningly similar to Mongo's sharding strategy, doesn't it? Each validator then works in isolation. More capacity needed? Chop the account space into more chunks. So where  are we now with the nagging questions? "No joins": Huh? What are those for? "No transactions": You mean no cross-collection and no cross-document transactions? Granted - but don't always need them either. "No hope for real applications": well... There are more issues and edge cases to slog through, I'm sure. But hopefully this gives you some ideas of how to solve common problems without distributed locking and relational databases. But then again, you can choose relational databases if they suit your problem.

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  • Sending JSON to an ASP.NET MVC Action Method Argument

    Javier G Money Lozano, one of the good folks involved with C4MVC, recently wrote a blog post on posting JSON (JavaScript Object Notation) encoded data to an MVC controller action. In his post, he describes an interesting approach of using a custom model binder to bind sent JSON data to an argument of an action method. Unfortunately, his sample left out the custom model binder and only demonstrates how to retrieve JSON data sent from a controller action, not how to send the JSON to the action method....Did 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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  • How to create a reasonably sized urban area manually but efficiently

    - by Overv
    I have a game concept that only really works in an urban area that is of reasonable scale and diversity. In terms of what it should look like, think GTA, in terms of the size think more like a small neighbourhood with residents and a few local shops, perhaps a supermarket. I'm mostly experienced in programming and not at all with modelling, texturing or drawing, but I've found that SketchUp allows me to design interesting looking buildings that I model after real world buildings in my own neighbourhood. Designing these buildings and other objects can take from a few tens of minutes to a few hours. My question is: what is the best approach for a one man army like me who does manage to model buildings to create an interesting city environment in a reasonable amount of time? My game will not be based on procedural generation, the environment will actually be modelled like GTA cities.

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  • Where should i organize my matrices in a 3D Game engine?

    - by Need4Sleep
    I'm working with a group of people from around the world to create a game engine(and hopefully a game with it) within the next upcoming years. My first task was writing a camera class for the engine to use in order to add cameras to the scene, position and follow points in the scene. The problem i have is with using matrices for transformations in the class, should i keep matrices separate to each class? such as have the model matrix in the model class, camera matrix in the camera class, or have all matrices placed in one class/chuck? I could see pros and cons for each method, but i wanted to hear some input form a more professional standpoint.

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  • Advanced Analytics Oracle Data Mining - NEW 2-Day Training Course

    - by Mike.Hallett(at)Oracle-BI&EPM
    A NEW 2-Day Oracle University (OU) Instructor Led Course on Oracle Data Mining has been developed for partners and customers to learn more about data mining, predictive analytics and knowledge discovery inside the Oracle Database. Oracle Data Mining, provides data mining algorithms that run native for high performance in-database model building and model deployment. This OU course is a great way to learn the advantages and benefits of "big data analytics"; mining data, building and deploying "predictive analytics" all inside the Oracle Database and to work with OBI. To register for a class, click here, then click on View Schedule to see the latest scheduled classes and/or submit your information expressing interest in attending a class.

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  • Any way for ubuntu to use more than one core of i7 cpu on my Asus laptop?

    - by G. He
    Newly installed ubuntu 11.10 on a new Asus U46E laptop. /proc/cpuinfo correctly identified the cpu but shows only one core: processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 42 model name : Intel(R) Core(TM) i7-2640M CPU @ 2.80GHz stepping : 7 cpu MHz : 800.000 cache size : 4096 KB physical id : 0 siblings : 1 core id : 0 cpu cores : 1 apicid : 0 initial apicid : 0 fpu : yes fpu_exception : yes cpuid level : 13 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc up arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 sse4_2 x2apic popcnt aes xsave avx lahf_lm ida arat epb xsaveopt pln pts dts tpr_shadow vnmi flexpriority ept vpid bogomips : 5587.63 clflush size : 64 cache_alignment : 64 address sizes : 36 bits physical, 48 bits virtual power management: I search here and found the answer to one post suggesting remove boot parameter 'nolapic'. However, on my particular laptop, ubuntu won't boot without this nolapic parameter. Is there anyway for ubuntu correly utility the full cpu power?

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  • Un-used Indexes on MDP_MATRIX Consuming Resources

    - by user702295
    Disable un-used Indexes: As much as it is recommended to create relevant indexes, it is advised not to have too many indexes on the mdp_matrix table.  Too many indexes will cause long waits on the table as indexes needs to get updated every time the table is updated.  There are many seeded indexes on mdp_matrix, every out of the box data model level has an index on the matrix table.  If a level is unused in the specific data model of the implementation, it is advisable to disable that index.  If the customer is not sure if and how indexes are utilized, the DBA can monitor all indexes.  After a few cycles of operation, the DBA should go over that list and see which indexes have not been used.  Consider disabling them. There are scripts on the net to monitor indexes or use the monitoring usage clause in the alter index statement.

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  • Making Class Diagram for MVC Pattern Project

    - by iMohammad
    I have a question about making a class diagram for an MVC based college senior project. If we have 2 actors of users in my system, lets say Undergrad and Graduate students are the children of abstract class called User. (Generalisation) Each actor has his own features. My question, in such case, do we need to have these two actors in separate classes which inherits from the abstract class User? even though, I'm going to implement them as roles using one Model called User Model ? I think you can see my confusion here. I code using MVC pattern, but I've never made a class diagram for this pattern. Thank you in advance!

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  • how can i get rotation vector from matrix4x4 in xna?

    - by mr.Smyle
    i want to get rotation vector from matrix to realize some parent-children system for models. Matrix bonePos = link.Bone.Transform * World; Matrix m = Matrix.CreateTranslation(link.Offset) * Matrix.CreateScale(link.gameObj.Scale.X, link.gameObj.Scale.Y, link.gameObj.Scale.Z) * Matrix.CreateFromYawPitchRoll(MathHelper.ToRadians(link.gameObj.Rotation.Y), MathHelper.ToRadians(link.gameObj.Rotation.X), MathHelper.ToRadians(link.gameObj.Rotation.Z)) //need rotation vector from bone matrix here (now it's global model rotation vector) * Matrix.CreateFromYawPitchRoll(MathHelper.ToRadians(Rotation.Y), MathHelper.ToRadians(Rotation.X), MathHelper.ToRadians(Rotation.Z)) * Matrix.CreateTranslation(bonePos.Translation); link.gameObj.World = m; where : link - struct with children model settings, like position, rotation etc. And link.Bone - Parent Bone

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