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  • Consumer Oriented Search In Oracle Endeca Information Discovery – Part 1

    - by Bob Zurek
    Information Discovery, a core capability of Oracle Endeca Information Discovery, enables business users to rapidly search, discover and navigate through a wide variety of big data including structured, unstructured and semi-structured data. One of the key capabilities, among many, that differentiate our solution from others in the Information Discovery market is our deep support for search across this growing amount of varied big data. Our method and approach is very different than classic simple keyword search that is found in may information discovery solutions. In this first part of a series on the topic of search, I will walk you through many of the key capabilities that go beyond the simple search box that you might experience in products where search was clearly an afterthought or attempt to catch up to our core capabilities in this area. Lets explore. The core data management solution of Oracle Endeca Information Discovery is the Endeca Server, a hybrid search-analytical database that his highly scalable and column-oriented in nature. We will talk in more technical detail about the capabilities of the Endeca Server in future blog posts as this post is intended to give you a feel for the deep search capabilities that are an integral part of the Endeca Server. The Endeca Server provides best-of-breed search features aw well as a new class of features that are the first to be designed around the requirement to bridge structured, semi-structured and unstructured big data. Some of the key features of search include type a heads, automatic alphanumeric spell corrections, positional search, Booleans, wildcarding, natural language, and category search and query classification dialogs. This is just a subset of the advanced search capabilities found in Oracle Endeca Information Discovery. Search is an important feature that makes it possible for business users to explore on the diverse data sets the Endeca Server can hold at any one time. The search capabilities in the Endeca server differ from other Information Discovery products with simple “search boxes” in the following ways: The Endeca Server Supports Exploratory Search.  Enterprise data frequently requires the user to explore content through an ad hoc dialog, with guidance that helps them succeed. This has implications for how to design search features. Traditional search doesn’t assume a dialog, and so it uses relevance ranking to get its best guess to the top of the results list. It calculates many relevance factors for each query, like word frequency, distance, and meaning, and then reduces those many factors to a single score based on a proprietary “black box” formula. But how can a business users, searching, act on the information that the document is say only 38.1% relevant? In contrast, exploratory search gives users the opportunity to clarify what is relevant to them through refinements and summaries. This approach has received consumer endorsement through popular ecommerce sites where guided navigation across a broad range of products has helped consumers better discover choices that meet their, sometimes undetermined requirements. This same model exists in Oracle Endeca Information Discovery. In fact, the Endeca Server powers many of the most popular e-commerce sites in the world. The Endeca Server Supports Cascading Relevance. Traditional approaches of search reduce many relevance weights to a single score. This means that if a result with a good title match gets a similar score to one with an exact phrase match, they’ll appear next to each other in a list. But a user can’t deduce from their score why each got it’s ranking, even though that information could be valuable. Oracle Endeca Information Discovery takes a different approach. The Endeca Server stratifies results by a primary relevance strategy, and then breaks ties within a strata by ordering them with a secondary strategy, and so on. Application managers get the explicit means to compose these strategies based on their knowledge of their own domain. This approach gives both business users and managers a deterministic way to set and understand relevance. Now that you have an understanding of two of the core search capabilities in Oracle Endeca Information Discovery, our next blog post on this topic will discuss more advanced features including set search, second-order relevance as well as an understanding of faceted search mechanisms that include queries and filters.  

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  • Decoding an affinity mask

    - by GavinPayneUK
    Recently, in preparation for my SQLBits NUMA internals session I began looking at some of the SQLOS DMVs and trying to understand how their contents directly related to the physical server architecture that SQL Server was running on. While their contents used regular terms such as node and affinity mask the results were often in an “internals” format that can be distracting to the human reader.  An example of this is the DMV sys.dm_os_nodes (link to Technet here ), or more specifically the column...(read more)

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  • Is MongoDB a good choice or not for my application?

    - by shubham
    I have a Reporting application which stores the reports in xml format as recieved from source (XML schema is not defined, it can be any format) and those reports contain some keys and values. Like jobid, setid be keys for 1 type of report and userid, groupId for another type of report etc. The type of keys that can be referred from the document is determined by the namespaces used in the xml doc. These keys are stored on the basis of namespace used in the xml document. For e.g. If a tag in xml fragment uses namespace= "myspace1", then I have keys A and B for myspace1 stored in another table. It will fetch those keys from that table for this namespace, look for their values in xml doc and store it in another table along with the pointer to this xml document (Id of a record storing complete xml document in a cell). Use cases: When the user comes and queries for that key and value, I return the document or a set of documents that are having those key/value pairs. When the user comes and queries for a certain key and provide a name for xslt (pre stored), I fetch the set of documents fulfilling that criteria and convert that xml to html with the specified xslt. When the user comes and asks for a particular fragment of a doc then it can fetch a subset from a particular document also. When the user comes and queries for top x values of a certain key, I return the set of documents that are having top 10 values of that key. I am using DB2 database for its support of xml along with relational capabilities. That makes easier for me to run xpath expressions and fetch values of keys and also aggregate a set of documents fullfilling a criteria, all on the database side. Problems: DB2 stores XML doc of upto 2GB in size. Retrieval is very slow. If some thing involves many documents, then it takes significant time for things to show up in browser, and the user has to wait. Can MongoDb help in this case, as it is document oriented? can I do xml related xpath queries and document transformations on db side? Or is it ok to use both in such a case?

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  • best command line tool to join videos

    - by user1079002
    I have used ffmpeg, but with it you have to first make mpg videos then do cat video1.mpg video2.mpg > joined.mpg and then convert to joined.mpg to joined.mp4 with ffmpeg to be able to upload on youtube. I heard there's mencoder which can join avi files without converting to mpg and using cat command. I'm making videos to upload on youtube so it needs to be avi mp4 or flv format. Which tool is the best to join videos from command line?

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  • SSMS Built in Reports for Server and Database Monitoring

    - by GrumpyOldDBA
    This is a long post which I hope will format correctly – I’ve placed a pdf version for download here  http://www.grumpyolddba.co.uk/sql2008/ssmsreports_grumpyolddba.pdf I sometimes discover that the built in reports for SQL Server within SSMS are an unknown, sometimes this is because not all the right components were installed during the server build, other times is because generally there’s never been great reporting for the DBA from the SQL Team so no-one expects to find anything useful for...(read more)

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  • REST to Objects in C#

    RESTful interfaces for web services are all the rage for many Web 2.0 sites.  If you want to consume these in a very simple fashion, LINQ to XML can do the job pretty easily in C#.  If you go searching for help on this, youll find a lot of incomplete solutions and fairly large toolkits and frameworks (guess how I know this) this quick article is meant to be a no fluff just stuff approach to making this work. POCO Objects Lets assume you have a Model that you want to suck data into from a RESTful web service.  Ideally this is a Plain Old CLR Object, meaning it isnt infected with any persistence or serialization goop.  It might look something like this: public class Entry { public int Id; public int UserId; public DateTime Date; public float Hours; public string Notes; public bool Billable;   public override string ToString() { return String.Format("[{0}] User: {1} Date: {2} Hours: {3} Notes: {4} Billable {5}", Id, UserId, Date, Hours, Notes, Billable); } } Not that this isnt a completely trivial object.  Lets look at the API for the service.  RESTful HTTP Service In this case, its TickSpots API, with the following sample output: <?xml version="1.0" encoding="UTF-8"?> <entries type="array"> <entry> <id type="integer">24</id> <task_id type="integer">14</task_id> <user_id type="integer">3</user_id> <date type="date">2008-03-08</date> <hours type="float">1.00</hours> <notes>Had trouble with tribbles.</notes> <billable>true</billable> # Billable is an attribute inherited from the task <billed>true</billed> # Billed is an attribute to track whether the entry has been invoiced <created_at type="datetime">Tue, 07 Oct 2008 14:46:16 -0400</created_at> <updated_at type="datetime">Tue, 07 Oct 2008 14:46:16 -0400</updated_at> # The following attributes are derived and provided for informational purposes: <user_email>[email protected]</user_email> <task_name>Remove converter assembly</task_name> <sum_hours type="float">2.00</sum_hours> <budget type="float">10.00</budget> <project_name>Realign dilithium crystals</project_name> <client_name>Starfleet Command</client_name> </entry> </entries> Im assuming in this case that I dont necessarily care about all of the data fields the service is returning I just need some of them for my applications purposes.  Thus, you can see there are more elements in the <entry> XML than I have in my Entry class. Get The XML with C# The next step is to get the XML.  The following snippet does the heavy lifting once you pass it the appropriate URL: protected XElement GetResponse(string uri) { var request = WebRequest.Create(uri) as HttpWebRequest; request.UserAgent = ".NET Sample"; request.KeepAlive = false;   request.Timeout = 15 * 1000;   var response = request.GetResponse() as HttpWebResponse;   if (request.HaveResponse == true && response != null) { var reader = new StreamReader(response.GetResponseStream()); return XElement.Parse(reader.ReadToEnd()); } throw new Exception("Error fetching data."); } This is adapted from the Yahoo Developer article on Web Service REST calls.  Once you have the XML, the last step is to get the data back as your POCO. Use LINQ-To-XML to Deserialize POCOs from XML This is done via the following code: public IEnumerable<Entry> List(DateTime startDate, DateTime endDate) { string additionalParameters = String.Format("start_date={0}&end_date={1}", startDate.ToShortDateString(), endDate.ToShortDateString()); string uri = BuildUrl("entries", additionalParameters);   XElement elements = GetResponse(uri);   var entries = from e in elements.Elements() where e.Name.LocalName == "entry" select new Entry { Id = int.Parse(e.Element("id").Value), UserId = int.Parse(e.Element("user_id").Value), Date = DateTime.Parse(e.Element("date").Value), Hours = float.Parse(e.Element("hours").Value), Notes = e.Element("notes").Value, Billable = bool.Parse(e.Element("billable").Value) }; return entries; }   For completeness, heres the BuildUrl method for my TickSpot API wrapper: // Change these to your settings protected const string projectDomain = "DOMAIN.tickspot.com"; private const string authParams = "[email protected]&password=MyTickSpotPassword";   protected string BuildUrl(string apiMethod, string additionalParams) { if (projectDomain.Contains("DOMAIN")) { throw new ApplicationException("You must update your domain in ProjectRepository.cs."); } if (authParams.Contains("MyTickSpotPassword")) { throw new ApplicationException("You must update your email and password in ProjectRepository.cs."); } return string.Format("https://{0}/api/{1}?{2}&{3}", projectDomain, apiMethod, authParams, additionalParams); } Thats it!  Now go forth and consume XML and map it to classes you actually want to work with.  Have fun! 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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  • To Fix HTTP 400-499 error codes with 301 redirects in .htaccess file

    - by user2131844
    Google previously indexed my websites pages (sitemap.xml) with below format: www.domain.com/2013/04/18/hot?test-gadgets-of-2013-to-include-in-?your-list www.domain.com/2013/02/09/rin?gdroid I have resubmitted the sitemap but there are still 404 errors in Google/Bing engine. Could you please help me to write 301 redirects rule in .htaccess file so when some clicks the URL for: www.domain.com/2013/02/09/rin?gdroid They should be redirected to: www.domain.com/rin?gdroid How we can write rule in .htaccess file to remove date part 2013/02/09/?

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  • udev complaining about deprecated rules

    - by Kerrek SB
    I have Ubuntu 10.10, upgraded several times from older versions over many years, and during startup, I get a long list of warning messages from udevd that certain syntax rules are deprecated. (I don't actually have a copy of the messages, since they don't appear to be logged in the ring buffer or any log files.) Does anyone know how I can summarily prune or upgrade the troublesome rule files to the current format?

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  • Running Built-In Test Simulator with SOA Suite Healthcare 11g in PS4 and PS5

    - by Shub Lahiri, A-Team
    Background SOA Suite for Healthcare Integration pack comes with a pre-installed simulator that can be used as an external endpoint to generate inbound and outbound HL7 traffic on specified MLLP ports. This is a command-line utility that can be very handy when trying to build a complete end-to-end demo within a standalone, closed environment. The ant-based utility accepts the name of a configuration file as the command-line input argument. The format of this configuration file has changed between PS4 and PS5. In PS4, the configuration file was XML based and in PS5, it is name-value property based. The rest of this note highlights these differences and provides samples that can be used to run the first scenario from the product samples set. PS4 - Configuration File The sample configuration file for PS4 is shown below. The configuration file contains information about the following items: Directory for incoming and outgoing files for the host running SOA Suite Healthcare Polling Interval for the directory External Endpoint Logical Names External Endpoint Server Host Name and Ports Message throughput to be simulated for generating outbound messages Documents to be handled by different endpoints A copy of this file can be downloaded from here. PS5 - Configuration File The corresponding sample configuration file for PS5 is shown below. The configuration file contains similar information about the sample scenario but is not in XML format. It has name-value pairs specified in the form of a properties file. This sample file can be downloaded from here. Simulator Configuration Before running the simulator, the environment has to be set by defining the proper ANT_HOME and JAVA_HOME. The following extract is taken from a working sample shell script to set the environment: Also, as a part of setting the environment, template jndi.properties and logging.properties can be generated by using the following ant command: ant -f ant-b2bsimulator-util.xml b2bsimulator-prop Sample jndi.properties and logging.properties are shown below and can be modified, as needed. The jndi.properties contains information about connectivity to the local Weblogic Managed Server instance and the logging.properties file controls the amount of logging that can be generated from the running simulator process. Simulator Usage - Start and Stop The command syntax to launch the simulator via ant is the same in PS4 and PS5. Only the appropriate configuration file has to be supplied as the command-line argument, for example: ant -f ant-b2bsimulator-util.xml b2bsimulatorstart -Dargs="simulator1.hl7-config.xml" This will start the simulator and will keep running to provide an active external endpoint for SOA Healthcare Integration engine. To stop the simulator, a similar ant command can be used, for example: ant -f ant-b2bsimulator-util.xml b2bsimulatorstop

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  • What packages do I install for ffmpeg and libmp3lame?

    - by matt wilkie
    On my desktop Ubuntu 10.4 I use ffmpeg to convert videos to a format my dvd-player understands. On my laptop running 10.10 I can't get the same command to work, what package(s) are missing? ffmpeg -i infile.flv \ -threads 2 -vcodec mpeg4 -vtag divx -acodec libmp3lame -sameq \ outfile.avi #...snip Unknown encoder 'libmp3lame' Using apt-cache search libmp3lame I'm told there exist libmp3lame0 and libmp3lame-dev, both of which I've installed. Using acodec libmp3lame0 doesn't work either.

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  • Algorithm to map an area [on hold]

    - by user37843
    I want to create a crawler that starts in a room and from that room to move North,East,West and South until there aren't any new rooms to visit. I don't want to have duplicates and the output format per line to be something like this: current room, neighbour 1, neighbour 2 ... and in the end to apply BFS algorithm to find the shortest path between 2 rooms. Can anyone offer me some suggestion what to use? Thanks

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  • Problem running the python code for backup on Ubuntu?

    - by Akash
    I was trying to run following python code through terminal but something is wrong as it is producing some errors source = ['/home/akash/', '/home/akash/code'] target_dir = '/media' target = target_dir + os.sep + time.strftime('%Y%m%d%H%M%S') + '.zip' zip_command = "zip -qr {0} {1}".format(target, ' '.join(source)) if os.system(zip_command) == 0: print('Successful backup to', target) else: print('Backup FAILED') but when i try to run it following error appears zip I/O error: Permission denied zip error: Could not create output file (/media/20131019083404.zip) Backup FAILED

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  • TSQL formatting - a sure fire way to start a conversation.

    - by fatherjack
    There are probably as many opinions on ways to format code as there are people writing code and I am not here to say that any one is better than any other. Well, that isn't true. I am here to say that one way is better than another but this isn't a matter of preference or personal taste, this is an example of where sloppy formatting can cause TSQL to weird and whacky things but following some simple methods can make your code more reliable and more robust when . Take these two pieces of code, ready...(read more)

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  • OpenGL quake 3 shader file for objects (for trees)

    - by mlodziaszka
    I decided to add to my game few trees, I already quake 3 model loader (md3) its for characters and method for texture drawing is store in *.ini file. I found a package of trees in MD3 and I have no problem with loading model alone, but there is a *.shader file and i have no idea how to load it to draw texture properly. Tree pack: http://www.custommapmakers.org/wiki/index.php/Models:GR_Trees_set I do not have to use exactly this format, I can write another loader, but trees in *.obj or .3ds look even harder

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  • How do I use IIS7 rewrite to redirect requests for (HTTP or HTTPS):// (www or no-www) .domainaliases.ext to HTTPS://maindomain.ext

    - by costax
    I have multiple domain names assigned to the same site and I want all possible access combinations redirected to one domain. In other words whether the visitor uses http://domainalias.ext or http://www.domainalias.ext or https://www.domainalias3.ext or https://domainalias4.ext or any other combination, including http://maindomain.ext, http://www.maindomain.ext, and https://www.maindomain.ext they are all redirected to https://maindomain.ext I currently use the following code to partially achieve my objectives: <?xml version="1.0" encoding="UTF-8"?> <configuration> <system.webServer> <rewrite> <rules> <rule name="CanonicalHostNameRule" stopProcessing="true"> <match url="(.*)" /> <conditions> <add input="{HTTP_HOST}" pattern="^MAINDOMAIN\.EXT$" negate="true" /> </conditions> <action type="Redirect" redirectType="Permanent" url="https://MAINDOMAIN.EXT/{R:1}" /> </rule> <rule name="HTTP2HTTPS" stopProcessing="true"> <match url="(.*)" /> <conditions> <add input="{HTTPS}" pattern="off" ignoreCase="true" /> </conditions> <action type="Redirect" redirectType="Permanent" url="https://MAINDOMAIN.EXT/{R:1}" /> </rule> </rules> </rewrite> </system.webServer> </configuration> ...but it fails to work in all instances. It does not redirect to https://maindomain.ext when user inputs https://(www.)domainalias.ext So my question is, are there any programmers here familiar with IIS7 ReWrite that can help me modify my existing code to cover all possibilities and reroute all my domain aliases, loaded by themselves or using www in front, in HTTP or HTTPS mode, to my main domain in HTTPS format??? The logic would be: if entire URL does NOT start with https://maindomain.ext then REDIRECT to https://maindomain.ext/(plus_whatever_else_that_followed). Thank you very much for your attention and any help would be appreciated. NOTE TO MODS: If my question is not in the correct format, please edit or advise. Thanks in advance.

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  • Animate multiple entities

    - by Robert
    I'm trying to animate multiple(3) entities using one model(IQM format). It's working but performance is really bad because I'm calling animate function for each entity in my game loop (I think problem is there). What's the best way to animate multiple entities (with different animation ofc) in OpenGL? I think I can try build one VBO / entity for better performances but I don't think it's the best way to do it.

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  • Import 3ds into JMonkeyEngine 3

    - by Yanick Rochon
    I have asked this question on SO, but I think it will be more suitable here. Basically, we are trying to import an animated character body (with skeleton) from 3D Studio Max to JMonkeyEngine 3, but while we succeeded at importing some animations, we cannot seem to export the skeleton to .skeleton.xml using OgreXML format. Since OgreXML seems to be the favored way to import models into JME, we dropped .obj files and such. Any help appreciated.

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  • DBA Reporting Presentation - Cambridge UG

    - by NeilHambly
    I'm now able to Report (sorry for the pun!) that my presentation on DBA Reporting I gave @ the User group on 25th November @ Red-Gate Offices in Cambridge So I have attached the Presentation in PDF format for you all to replay and view if you weren't able to attend. Here a few links you may also want to check out on some of those products we discussed Various ones like SQL NEXUS / DAIG / PAL / Internals Viewer http://www.codeplex.com/ SQL Server 2005 Performance Dashboard Reports http://www...(read more)

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  • Will installing Ubuntu using Wubi erase Windows?

    - by James Lang
    I have an HP laptop with 2 partitions: C: and D:, with windows 7 installed in the C: drive and D: is the Recovery partition. When I try to install Ubuntu 12.04 LTS using Wubi, it only shows the C: drive for installing and not the D: drive where I wanted to format and install ubuntu. So, if I go ahead and install in the C: drive where windows 7 is already installed, would Wubi erase windows 7? Or it will just install Ubuntu as a program in windows?

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  • How to create a screencast?

    - by Riccardo Murri
    How can I create a screencast on Ubuntu? What applications are available? The app I'm looking for has ideally all of these features: Can record in a format that can be played back easily on any platform and/or accepted by youtube or another popular video site Can record just a window (instead of the whole screen), possibly selecting it with a mouse click Can start recording after a configurable delay (e.g., I launch the app and have time to do arrangements to my desktop/window before actual recording starts)

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  • Obtaining the correct Client IP address when a Physical Load Balancer and a Web Server Configured With Proxy Plug-in Are Between The Client And Weblogic

    - by adejuanc
    Some Load Balancers like Big-IP have build in interoperability with Weblogic Cluster, this means they know how Weblogic understand a header named 'WL-Proxy-Client-IP' to identify the original client ip.The problem comes when you have a Web Server configured with weblogic plug-in between the Load Balancer and the back-end weblogic servers - WL-Proxy-Client-IP this is not designed to go to Web server proxy plug-in. The plug-in will not use a WL-Proxy-Client-IP header that came in from the previous hop (which is this case is the Physical Load Balancer but could be anything), in order to prevent IP spoofing, therefore the plug-in won't pass on what Load Balancer has set for it.So unfortunately under this Architecture the header will be useless. To get the client IP from Weblogic you need to configure extended log format and create a custom field that gets the appropriate header containing the IP of the client.On WLS versions prior to 10.3.3 use these instructions:You can also create user-defined fields for inclusion in an HTTP access log file that uses the extended log format. To create a custom field you identify the field in the ELF log file using the Fields directive and then you create a matching Java class that generates the desired output. You can create a separate Java class for each field, or the Java class can output multiple fields. For a sample of the Java source for such a class, seeJava Class for Creating a Custom ELF Field to import weblogic.servlet.logging.CustomELFLogger;import weblogic.servlet.logging.FormatStringBuffer;import weblogic.servlet.logging.HttpAccountingInfo;/* This example outputs the X-Forwarded-For field into a custom field called MyOriginalClientIPField */public class MyOriginalClientIPField implements CustomELFLogger{ public void logField(HttpAccountingInfo metrics,  FormatStringBuffer buff) {   buff.appendValueOrDash(metrics.getHeader("X-Forwarded-For");  }}In this case we are using 'X-Forwarded-For' but it could be changed for the header that contains the data you need to use.Compile the class, jar it, and prepend it to the classpath.In order to compile and package the class: 1. Navigate to <WLS_HOME>/user_projects/domains/<SOME_DOMAIN>/bin2. Set up an environment by executing: $ . ./setDomainEnv.sh This will include weblogic.jar into classpath, in order to use any of the libraries included under package weblogic.*3. Compile the class by copying the content of the code above and naming the file as:MyOriginalClientIPField.java4. Run javac to compile the class.$javac MyOriginalClientIPField.java5. Package the compiled class into a jar file by executing:$jar cvf0 MyOriginalClientIPField.jar MyOriginalClientIPField.classExpected output is:added manifestadding: MyOriginalClientIPField.class(in = 711) (out= 711)(stored 0%)6. This will produce a file called:MyOriginalClientIPField.jar This way you will be able to get the real client IP when the request is passing through a Load Balancer and a Web server before reaching WLS. Since 10.3.3 it is possible to configure a specific header that WLS will check when getRemoteAddr is called. That can be set on the WebServer Mbean. In this case, set that to be X-Forwarded-For header coming from Load Balancer as well.

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  • What packages do I install for ffmpeg and libmp3lame?

    - by matt wilkie
    On my desktop Ubuntu 10.4 I use ffmpeg to convert videos to a format my dvd-player understands. On my laptop running 10.10 I can't get the same command to work, what package(s) are missing? ffmpeg -i infile.flv \ -threads 2 -vcodec mpeg4 -vtag divx -acodec libmp3lame -sameq \ outfile.avi #...snip Unknown encoder 'libmp3lame' Using apt-cache search libmp3lame I'm told there exist libmp3lame0 and libmp3lame-dev, both of which I've installed. Using acodec libmp3lame0 doesn't work either.

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  • how to keep display tick rate steady when using continuous collision detection?

    - by nas Ns
    (I've just found about this forum). I hope it is ok to repost my question again here. I posted this question at stackoverflow, but it looks like I might get better help here. Here is the question: I've implemented basic particles motion simulation with continuous collision detection. But there is small issue in display. Assume simple case of circles moving inside square. All elastic collisions. no firction. All motion is constant speed. No forces are involved, no gravity. So when a particle is moving, it is always moving at constant speed (in between collisions) What I do now is this: Let the simulation time step be 1 second (for example). This is the time step simulation is advanced before displaying the new state (unless there is a collision sooner than this). At start of each time step, time for the next collision between any particles or a particle with a wall is determined. Call this the TOC time; let’s say TOC was .5 seconds in this case. Since TOC is smaller than the standard time step, then the system is moved by TOC and the new system is displayed so that the new display shows any collisions as just taking place (say 2 circles just touched each other’s, or a circle just touched a wall) Next, the collision(s) are resolved (i.e. speeds updated, changed directions etc..). A new step is started. The same thing happens. Now assume there is no collision detected within the next 1 second (those 2 circles above will not be in collision any more, even though they are still touching, due to their speeds showing they are moving apart now), Hence, simulation time is advanced now by the full one second, the standard time step, and particles are moved on the screen using 1 second simulation time and new display is shown. You see what has just happened: One frame ran for .5 seconds, but the next frame runs for 1 second, may be the 3rd frame is displayed after 2 seconds, may be the 4th frame is displayed after 2.8 seconds (because TOC was .8 seconds then) and so on. What happens is that the motion of a particle on the screen appears to speed up or slow down, even though it is moving at constant speed and was not even involved in a collision. i.e. Looking at one particle on its own, I see it suddenly speeding up or slowing down, becuase another particle had hit a wall. This is because the display tick is not uniform. i.e. the frame rate update is changing, giving the false illusion that a particle is moving at non-constant speed while in fact it is moving at constant speed. The motion on the screen is not smooth, since the screen is not updating at constant rate. I am not able to figure how to fix this. If I want to show 2 particles at the moment of the collision, I must draw the screen at different times. Drawing the screen always at the same tick interval, results in seeing 2 particles before the collision, and then after the collision, and not just when they colliding, which looked bad when I tried it. So, how do real games handle this issue? How to display things in order to show collisions when it happen, yet keep the display tick constant? These 2 requirements seem to contradict each other’s.

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