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  • best SEO method for date in url structure? [closed]

    - by Haroldo
    I'm working on an events website so dates are very important search terms, ie: 'whats on on fri 14th september' I've seen it done in various methods for example: domain/whats-on/city-hall/14-09-2010/event-name.html domain/whats-on/city-hall/2010/09/14/event-name.html the first is 'shallower'. the second could be clearer for google to synonym-ize as a date, has anyone else got any experience or input?

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  • AJAX/JSONP Question. Access id denied using IE while requesting corss domain.

    - by Sisir
    Ok, Here we go. I have already searched the Stack for the answer i have found some useful info but i want to clear up some more things. I also search the net for the answer but no real help. I have worked with some api (yelp, ouside.in). In yelp i use to inject the script to head with the url request to the api with a callback funcion. I worked fine in all browsers. But while using outside.in api when i call the url the callback in not working. In yelp they have a url field can be used like that callback=callbackfuncion so the callback will automatically called. But in outside.in there is not such field available. Is there are any standard command for callback function which will work regardless of any server/api? I also tried a standard ajax request using jQuery $.ajax() function. It worked for my local pc for both IE and other browser but did not working in IE showing the error: access denied, other borwser seems ok. Firebug in my FF also don't notice any errors. Outside.in has an javascript example but it is too hard to me to understand github.com/outsidein/api-examples/tree/master/javascript/browser/ site i am working: http://citystir.com yelp: yelp.com outside.in: outside.in Techniqual info: i am using: wampserver in local, wordpress for hosting, Godaddy, apache for remote with linux. Codes: Using Jquery $.ajax url is like: "http://hyperlocal-api.outside.in/v1.1/states/Illinois/cities/chicago/stories?dev_key="+key+"&sig="+signeture+"&limit=3 function makeOutsideRequest(url){ $.ajax({ url: url, dataType: 'json', type: 'GET', success: function (data, status, xhr) { if (data == null) { alert("An error occurred connecting to " + url + ". Please ensure that the server is running and configured to allow cross-origin requests."); }else{ printHomeNews(data); } }, error: function (xhr, status, error) { alert("An error occurred - check the server log for a stack trace."); } }); } Thanks!

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  • How to get current controller for a URL in Rails?

    - by valk
    I'm using this code to highlight currently active menu tab with Twitter Bootstrap: def nav_link_to(link_text, link_path, options = nil) class_name = current_page?(link_path) ? 'active' : '' content_tag(:li, :class => class_name) do link_to link_text, link_path, options end end This of course makes the link active, only if the given link IS the current page. How can I change this function, such that it would return 'active' for any links below current controller? In other words, for all actions for Posts controller, the links would be active? Thanks.

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  • Javascript function working strangely during the first call in CHROME ?

    - by Sohil
    HI all, Below mentioned javascript code works fine in all browsers including chrome(from second call onwards). function call(val){ url = window.location.href; indexnum = url.lastIndexOf("/"); str = url.slice(indexnum+1); window.location.href = url.replace(str, "sample.php?src_q=") + val; } I am calling this function on onclick of a link as below <?php echo "<a href='#' onclick='javascript:call(\"$fieldvalue\");'>$fieldvalue</a>" ?> Normal Behaviour : In all browser after clicking on the link new formed url is url://localhost/mysite/sample.php?src_q=val Strange Behaviour : When I click on the link for the first time in chrome value of variable val gets replaced by url and its value as follows http://localhost/mysite/sample.php?src_q=http://localhost/mysite/val This strange behaviour happens during the first click in chrome. From the second call onwards in the same tab, the value of variable val works fine and I get desired url. I tried to google on it, but couldn't found any explanation. Thanks in advance.

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  • Php, passing data between pages without using the url?

    - by terabytest
    I have a php page that has a form that asks for an e-mail. When you press the send button, it gets to another php page, which gets the form data and does its stuff. I need to then be able to go back to the old page (the one that contained the form) and give it some data so that it will be able to change itself and say "You've sent your e-mail successfully, and will not display the form. How do I do it?

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  • [Facebook Graph API - Android] I want to know the HTTPSConnection redirected to which URL?

    - by Mohammad Abdelaziz
    I am building an application that uses the Facebook Graph API. To get the access token I should send the following request https://graph.facebook.com/oauth/authorize? client_id=...& redirect_uri=http://www.example.com/callback It redirects to the redirect_uri with the code to be used as access token. How can I capture that the HttpsURLConnection is redirected and how to get the code? Is it possible or I need to have server that gets the access token?

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  • How to call back (like onActivityResult) after launching activity from browser by clicking url?

    - by kimilhee
    I succeded to call activity from browser link with tag like this. <a href="myapp://launch.myapp.com/activity2?var1=linkClicked">my app</a> of cource I added actvity setting in AndroidManifest.xml like this. <activity android:name=".Activity2" > <intent-filter> <action android:name="android.intent.action.VIEW"></action> <category android:name="android.intent.category.DEFAULT"></category> <category android:name="android.intent.category.BROWSABLE"></category> <data android:host="launch.myapp.com" android:scheme="myapp" android:pathPrefix="/activity2"></data> </intent-filter> </activity> I want to call back from the activity2 with a value. Is there any way to receive some value from the activity that was launched by the browser like above? In other words I want do something like onActivityResult in the browser and get a value from the activity and set the value on the web page which has launched the activity.

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  • What do these characters do in a URL/WebAddress?

    - by acidzombie24
    I notice these characters are all illegal #%<>?\/*+|:" I notice these are encoded (%NN where NN is the hex value) but can be replace without problem $,;=& @ (note the space which is typically encoded as + (but may be %20)) #%?/+ i understand. But whats do the following characters do? <>\*|": Note: I understand what : does in the domain part (its the port) as @ is a login but after the first / why is : illegal? (@ isnt)

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  • Drupal 6, how to identify active menu item by url parameters (full link), ?q=page1&filter=10

    - by OlgaV
    I have a submenu that has all items linked to the same node, but with different additional parameters, for ex: ... <li...><a href = "/?q=page1&filter=10" class = "... active">Item1</a></li> <li...><a href = "/?q=page1&filter=11" class = "... active">Item2</a></li> ... in this case all items have class 'active' and none of them has class 'active-trail'. Is there any way to identify the true active link (for styling purposes)? any suggestions will be much appreciated!

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  • What does the $1$2$4 mean in this preg_replace?

    - by Taylor
    Got this function for ammending the query string and was wondering what the replacement part of the pre_replace meant (ie- $1$2$4). function add_querystring_var($url, $key, $value) { $url = preg_replace('/(.*)(\?|&)' . $key . '=[^&]+?(&)(.*)/i', '$1$2$4', $url . '&'); $url = substr($url, 0, -1); if (strpos($url, '?') === false) { return ($url . '?' . $key . '=' . $value); } else { return ($url . '&' . $key . '=' . $value); } } Not too familiar with regular expression stuff. I get the various parts to preg_replace but not 100% about the use of '$1$2$4' in the replacement part.

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  • html open a url on new target and focus.

    - by richard
    I am trying to fix a web site. It opens a help page in a new window/tab via <a href="..." target="help"> (no other frame has this name) This works well the first time opening a new window/tab, for the help. But on subsequent clicks the window/tab is loaded but remains hidden. I tryed this: <script> function OpenAndFocusHelp() { win=window.open('help/1000CH00017.htm','help'); win.focus(); } </script> <a href="help.html" target="help" onclick="OpenAndFocusHelp()">Help</a> It did not work!

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  • How to rewrite a URL with %23 in it?

    - by Jan P.
    I have a (wordpress) blog where after commenting the users are redirected back to the page with an anchor to their comment. Should look like this: http://example.org/foo-bar/#comment-570630 But somehow I get a lot of 404 ins my logfiles for such URLs: http://example.org/foo-bar/%23comment-570630 Is there a way to write a .htaccess rewrite rule to fix this? Bonus question: Any idea why this happens and what I can do about it?

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  • Silverlight 4 Training Kit

    - by ScottGu
    We recently released a new free Silverlight 4 Training Kit that walks you through building business applications with Silverlight 4.  You can browse the training kit online or alternatively download an entire offline version of the training kit.  The training material is structured on teaching how to use the new Silverlight 4 features to build an end to end business application. The training kit includes 8 modules, 25 videos, and several hands on labs. Below is a breakdown and links to all of the content. [In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu] Module 1: Introduction Click here to watch this module. In this video John Papa and Ian Griffiths discuss the key areas that the Building Business Applications with Silverlight 4 course focuses on. This module is the overview of the course and covers many key scenarios that are faced when building business applications, and how Silverlight can help address them. Module 2: WCF RIA Services Click here to explore this module. In this lab, you will create a web site for managing conferences that will be the basis for the other labs in this course. Don’t worry if you don’t complete a particular lab in the series – all lab manual instructions are accompanied by completed solutions, so you can either build your own solution from start to finish, or dive straight in at any point using the solutions provided as a starting point. In this lab you will learn how to set up WCF RIA Services, create bindings to the domain context, filter using the domain data source, and create domain service queries. Online Link Download Source Download Lab Document Videos Module 2.1 - WCF RIA Services Ian Griffiths sets up the Entity Framework and WCF RIA Services for the sample Event Manager application for the course. He covers how to set up the services, how the Domain Services work and the role that the DomainContext plays in the sample application. He also reviews the metadata classes and integrating the navigation framework. Module 2.2 – Using WCF RIA Services to Edit Entities Ian Griffiths discusses how he adds the ability to edit and create individual entities with the features built into WCF RIA Services into the sample Event Manager application. He covers data binding fundamentals, IQueryable, LINQ, the DomainDataSource, navigation to a single entity using the navigation framework, and how to use the Visual Studio designer to do much of the work . Module 2.3 – Showing Master/Details Records Using WCF RIA Services Ian Griffiths reviews how to display master/detail records for the sample Event Manager application using WCF RIA Services. He covers how to use the Include attribute to indicate which elements to serialize back to the client. Ian also demonstrates how to use the Data Sources window in the designer to add and bind controls to specific data elements. He wraps up by showing how to create custom services to the Domain Services. Module 3 – Authentication, Validation, MVVM, Commands, Implicit Styles and RichTextBox Click here to visit this module. This lab demonstrates how to build a login screen, integrate ASP.NET authentication, and perform validation on data elements. Model-View-ViewModel (MVVM) is introduced and used in this lab as a pattern to help separate the UI and business logic. You will also learn how to use implicit styling and the new RichTextBox control. Online Link Download Source Download Lab Document Videos Module 3.1 – Authentication Ian Griffiths covers how to integrate a login screen and authentication into the sample Event Manager application. Ian shows how to use the ASP.NET authentication and integrate it into WCF RIA Services and the Silverlight presentation layer. Module 3.2 – MVVM Ian Griffiths covers how to Model-View-ViewModel (MVVM) patterns into the sample Event Manager application. He discusses why MVVM exists, what separated presentation means, and why it is important. He shows how to connect the View to the ViewModel, why data binding is important in this symbiosis, and how everything fits together in the overall application. Module 3.3 –Validation Ian Griffiths discusses how validation of user input can be integrated into the sample Event Manager application. He demonstrates how to use the DataAnnotations, the INotifyDataErrorInfo interface, binding markup extensions, and WCF RIA Services in concert to achieve great validation in the sample application. He discusses how this technique allows for property level validation, entity level validation, and asynchronous server side validation. Module 3.4 – Implicit Styles Ian Griffiths discusses how why implicit styles are important and how they can be integrated into the sample Event Manager application. He shows how implicit styles defined in a resource dictionary can be applied to all elements of a particular kind throughout the application. Module 3.5 – RichTextBox Ian Griffiths discusses how the new RichTextBox control and it can be integrated into the sample Event Manager application. He demonstrates how the RichTextBox can provide editing for the event information and how it can display the rich text for selection and copying. Module 4 – User Profiles, Drop Targets, Webcam and Clipboard Click here to visit this module. This lab builds new features into the sample application to take the user's photo. It teaches you how to use the webcam to capture an image, use Silverlight as a drop target, and take advantage of programmatic access to the clipboard. Link Download Source Download Lab Document Videos Module 4.1 – Webcam Ian Griffiths demonstrates how the webcam adds value to the sample Event Manager application by capturing an image of the attendee. He discusses the VideoCaptureDevice, the CaptureDviceConfiguration, and the CaptureSource classes and how they allow audio and video to be captured so you can grab an image from the capture device and save it. Module 4.2 - Drag and Drop in Silverlight Ian Griffiths demonstrates how to capture and handle the Drop in the sample Event Manager application so the user can drag a photo from a file and drop it into the application. Ian reviews the AllowDrop property, the Drop event, how to access the file that can be dropped, and the other drag related events. He also reviews how to make this work across browsers and the challenges for this. Module 5 – Schedule Planner and Right Mouse Click Click here to visit this module. This lab builds on the application to allow grouping in the DataGrid and implement right mouse click features to add context menu support. Link Download Source Download Lab Document Videos Module 5.1 – Grouping and Binding Ian Griffiths demonstrates how to use the grouping features for data binding in the DataGrid and how it applies to the sample Event Manager application. He reviews the role of the CollectionViewSource in grouping, customizing the templates for headers, and how to work with grouping with ItemsControls. Module 5.2 – Layout Visual States Ian Griffiths demonstrates how to use the Fluid UI animation support for visual states in the ListBox control DataGrid and how it applies to the sample Event Manager application. He reviews the 3 visual states of BeforeLoaded, AfterLoaded, and BeforeUnloaded. Module 5.3 – Right Mouse Click Ian Griffiths demonstrates how to add support for handling the right mouse button click event to display a context menu for the Event Manager application. He demonstrates how to handle the event, show a custom context menu control, and integrate it into the scheduling portion of the application. Module 6 – Printing the Schedule Click here to visit this module. This lab teaches how to use the new printing features in Silverlight 4. The lab walks through the PrintDocument class and the ViewBox control, while showing how to print multiple pages of content using them. Link Download Source Download Lab Document Videos Module 6.1 – Printing and the Viewbox Ian Griffiths demonstrates how to add the ability to print the schedule to the sample Event Manager application. He walks through the importance of the PrintDocument class and its members. He also shows how to handle printing the visual tree and how the ViewBox control can help. Module 6.2 – Multi Page Printing Ian Griffiths expands on his printing discussion by showing how to handle printing multiple pages of content for the sample Event Manager application. He shows how to paginate the content and points out various tips to keep in mind when determining the printable area. Module 7 – Running the Event Dashboard Out of Browser Click here to visit this module. This lab builds a dashboard for the sample application while explaining the fundamentals of the out of browser features, how to handle authentication, displaying notifications (toasts), and how to use native integration to use COM Interop with Silverlight. Link Download Source Download Lab Document Videos Module 7.1 – Out of Browser Ian Griffiths discusses the role of an Out of Browser application for administrators to manage the events and users in the sample Event Manager application. He discusses several reasons why out of browser applications may better suit your needs including custom chrome, toasts, window placement, cross domain access, and file access. He demonstrates the basic technique to take your application and make it work out of browser using the tools. Module 7.2 – NotificationWindow (Toasts) for Elevated Trust Out of Browser Applications Ian Griffiths discusses the how toasts can be used in the sample Event Manager application to show information that may require the user's attention. Ian covers how to create a toast using the NotificationWindow, security implications, and how to make the toast appear as needed. Module 7.3 – Out of Browser Window Placement Ian Griffiths discusses the how to manage the window positioning when building an out of browser application, handling the windows state, and controlling and handling activation of the window. Module 7.4 – Out of Browser Elevated Trust Application Overview Ian Griffiths discusses the implications of creating trusted out of browser application for the Event Manager sample application. He reviews why you might want to use elevated trust, what features is opens to you, and how to take advantage of them. Topics Ian covers include the dynamic keyword in C# 4, the AutomationFactory class, the API to check if you are in a trusted application, and communicating with Excel. Module 8 – Advanced Out of Browser and MEF Click here to visit this module. This hands-on lab walks through the creation of a trusted out of browser application and the new functionality that comes with that. You will learn to use COM Automation, handle the window closing event, set custom window chrome, digitally sign your Silverlight out of browser trusted application, create a silent install option, and take advantage of MEF. Link Download Source Download Lab Document Videos Module 8.1 – Custom Window Chrome for Elevated Trust Out of Browser Applications Ian Griffiths discusses how to replace the standard operating system window chrome with customized chrome for an elevated trusted out of browser application. He covers how it is important to handle close, resize, minimize, and maximize events. Ian mentions that the tooling was not ready when he shot this video, but the good news is that the tooling now supports setting the custom chrome directly from the property page for the Silverlight application. Module 8.2 – Window Closing Event for Out of Browser Applications Ian Griffiths discusses the WindowClosing event and how to handle and optionally cancel the event. Module 8.3 – Silent Install of Out of Browser Applications Ian Griffiths discusses how to use the SLLauncher executable to install an out of browser application. He discusses the optional command line switches that can be set including how the emulate switch can help you emulate the install process. Ian also shows how to setup a shortcut for the application and tell the application where it should look for future updates online. Module 8.4 – Digitally Signing Out of Browser Application Ian Griffiths discusses how and why to digitally sign an out of browser application using the signtool program. He covers what trusted certificates are, the implications of signing (or not signing), and the effect on the user experience. Module 8.5 – The Value of MEF with Silverlight Ian Griffiths discusses what MEF is, how your application can benefit from it, and the fundamental features it puts at your disposal. He covers the 3 step import, export and compose process as well as how to dynamically import XAP files using MEF. Summary As you can probably tell from the long list above – this series contains a ton of great content, and hopefully provides a nice end-to-end walkthrough that helps explain how to take advantage of Silverlight 4 (and all its new features).  Hope this helps, Scott

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  • PDC and Tech-Ed Europe Slides and Code

    - by Stephen Walther
    I spent close to three weeks on the road giving talks at Tech-Ed Europe (Berlin), PDC (Los Angeles), and the Los Angeles Code Camp (Los Angeles). I got to talk about two topics that I am very passionate about: ASP.NET MVC and Ajax. Thanks everyone for coming to all my talks! At PDC, I announced all of the new features of our ASP.NET Ajax Library. In particular, I made five big announcements: ASP.NET Ajax Library Beta Released – You can download the beta from Ajax.CodePlex.com ASP.NET Ajax Library includes the AJAX Control Toolkit – You can use the Ajax Control Toolkit with ASP.NET MVC. ASP.NET Ajax Library being contributed to the CodePlex Foundation – ASP.NET Ajax is the founding project for the CodePlex Foundation (see CodePlex.org) ASP.NET Ajax Library is receiving full product support – Complain to Microsoft Customer Service at midnight on Christmas ASP.NET Ajax Library supports jQuery integration – Use (almost) all of the Ajax Control Toolkit controls in jQuery For more details on the Ajax announcements, see James Senior’s blog entry on the Ajax announcements at: http://jamessenior.com/post/News-on-the-ASPNET-Ajax-Library.aspx In my MVC talks, I discussed the new features being introduced with ASP.NET MVC 2. Here are three of my favorite new features: Client Validation – Client validation done the right way. Do your validation in your model and let the validation bubble up to JavaScript code automatically. Areas – Divide your ASP.NET MVC application into sub-applications. Great for managing both medium and large projects. RenderAction() – Finally, a way to add content to master pages and multiple pages without doing anything strange or twisted. There are demos of all of these features in the MVC downloads below. Here are the power point and code from all of the talks: PDC – Introducing the New ASP.NET Ajax Library PDC – ASP.NET MVC: The New Stuff Tech-Ed Europe - What's New in Microsoft ASP.NET Model-View-Controller Tech-Ed Europe - Microsoft ASP.NET AJAX: Taking AJAX to the Next Level

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  • ASP.NET 4 Hosting :: ValidateRequest=”false” not working in .Net 4.0 (VS.Net 2010)

    - by mbridge
    When we migrated our project from .NET 3.5 to .NET 4.0, we can get this error: Error: System.Web.HttpRequestValidationException A potentially dangerous Request.Form value was detected from the client (ctl00$CC$txtAnswer=\”… World\r\n\r\nI am doing Testin…\”).”} System.Web.HttpRequestValidationException at System.Web.HttpRequest.ValidateString(String value, String collectionKey, RequestValidationSource requestCollection)    at System.Web.HttpRequest.ValidateNameValueCollection(NameValueCollection nvc, RequestValidationSource requestCollection)    at System.Web.HttpRequest.get_Form()    at System.Web.HttpRequest.get_HasForm()    at System.Web.UI.Page.GetCollectionBasedOnMethod(Boolean dontReturnNull)    at System.Web.UI.Page.DeterminePostBackMode()    at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)    at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)    at System.Web.UI.Page.ProcessRequest()    at System.Web.UI.Page.ProcessRequestWithNoAssert(HttpContext context)    at System.Web.UI.Page.ProcessRequest(HttpContext context)    at ASP.displaypost_aspx.ProcessRequest(HttpContext context) in c:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\root\a37c2f81\cfc4c927\App_Web_i2rujncl.9.cs:line 0    at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()    at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) What is the Cause? In ASP.NET 4, by default, request validation is enabled for all requests, because it is enabled before the BeginRequest phase of an HTTP request. As a result, request validation applies to requests for all ASP.NET resources, not just .aspx page requests. This includes requests such as Web service calls and custom HTTP handlers. Request validation is also active when custom HTTP modules are reading the contents of an HTTP request. Solution: To revert to the behavior of the ASP.NET 2.0 request validation feature, add the following setting in the Web.config file: <system.web>  <httpRuntime requestValidationMode=”2.0? /> </system.web>

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  • ArchBeat Link-o-Rama for 11/22/2011

    - by Bob Rhubart
    A Brief Introduction on Migrating to an Oracle-based Cloud Environment | Tom Laszewski "Before you can start migrating to the cloud, you must define what the cloud means to you," says Tom Laszeski. "The cloud is not a specific software or hardware product; contrary to what many technology vendors would have you believe." Custom Exception Registration for ADF BC EO Attribute | Andrejus Baranovskis "Sometimes customers prefer to implement business logic validation completely in Java, without using ADF BC declarative/Groovy validation rules," says Oracle ACE Director Andrejus Baranovskis. "Thats fine, we can code business logic validation in ADF and implement different custom validation methods on VO/EO level." Oracle Exadata Virtual Conference - Jan 20 2012 The Exadata SIG, along with IOUG, is organizing the First Exadata Virtual Conference, to be held on January 20, 2012. Proposals for presentations are now being accepted. Smooth Sailing or Rough Waters: Navigating Policy Administration Modernization | Helen Pitts "It’s no surprise that fueling growth, both now and in the future, continues to be a key driver for modernization" says Helen Pitts. "Why? Inflexible, hard-coded, legacy systems require customization by IT every time a change is required." Architects putting on the Ritz; Info integration book learning; Platform for SAS Grid Computing This week on the Architect Home Page on OTN. Webcast: Introducing Oracle WebLogic Server 12c: Developer Deep Dive - Dec 1 - 11am PT / 2pm ET Learn how Oracle WebLogic Server 12c enables rapid development of modern, lightweight Java EE 6 applications. Discover how you can leverage the latest development technologies, tools and standards when deploying to Oracle WebLogic Server across both conventional and Cloud environments. Architecture all day. Oracle Technology Network Architect Day - Phoenix, AZ - Dec14. Free registration. When: December 14, 2011 Where: The Ritz-Carlton, Phoenix, 2401 East Camelback Road, Phoenix, AZ 85016 Registration is free, but seating is limited.

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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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