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• What's a good FOSS java servlet session replication solution

  - by Bossy Joe

  I work on a very high volume public website running on Tomcat 5.5. Currently we require stickiness to a particular server in order to maintain session. I'd like to start replicating session, but have had trouble finding a good FOSS solution. I've written my own Manager (using memcached as the store) but am having trouble dealing with race conditions if more than one server is handling the requests for the same user. Is there a solution out there I should be looking at? I'm looking for not just something that works as a fallback if stickiness fails, but that would work if user requests are regularly spread to multiple servers.

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• conceptually different entities with a few similar properties should be stored in one table or more?

  - by Haghpanah

  Assume A and B are conceptually different entities that have a few similar properties and of course their own specific properties. In database design, should I put those two entities in one big aggregated table or two respectively designed tables. For instance, I have two types of payment; Online-payment and Manual-payment with following definition, TABLE [OnlinePayments] ( [ID] [uniqueidentifier], [UserID] [uniqueidentifier], [TrackingCode] [nvarchar](32), [ReferingCode] [nvarchar](32), [BankingAccID] [uniqueidentifier], [Status] [int], [Amount] [money], [Comments] [nvarchar](768), [CreatedAt] [datetime], [ShopingCartID] [uniqueidentifier], ) And TABLE [ManualPayments] ( [ID] [uniqueidentifier], [UserID] [uniqueidentifier], [BankingAccID] [uniqueidentifier], [BankingOrgID] [uniqueidentifier], [BranchName] [nvarchar](64), [BranchCode] [nvarchar](16), [Amount] [money], [SlipNumber] [nvarchar](64), [SlipImage] [image], [PaidAt] [datetime], [Comments] [nvarchar](768), [CreatedAt] [datetime], [IsApproved] [bit], [ApprovedByID] [uniqueidentifier], ) One of my friends told me that creating two distinct tables for such similar entities is not a well design method and they should be put in one single table for the sake of performance and ease of data manipulations. I’m now wondering what to do? What is the best practice in such a case?

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• Linq to SQL and Realtime Data

  - by Jeremy

  I have an application that needs to constantly (every 50ms), call to an MVC action, and pickup/drop off data. I am using Linq to SQL and MVC because of how simple they are to implement, and I know that they aren't perfect when it comes to performance, but it works relatively well, but the best speed I can get with my current approach is 200ms (without requests overlapping). Each call to the site will create a new instance of the datacontext, query/insert it and return that data. Is there a way to have the datacontext static, but submitchanges say every 5 seconds, so that i am pretty much hitting an in-memory version of the data?

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• Collection type generated by for with yield

  - by Jesper

  When I evaluate a for in Scala, I get an immutable IndexedSeq (a collection with array-like performance characteristics, such as efficient random access): scala> val s = for (i <- 0 to 9) yield math.random + i s: scala.collection.immutable.IndexedSeq[Double] = Vector(0.6127056766832756, 1.7137598183155291, ... Does a for with a yield always return an IndexedSeq, or can it also return some other type of collection class (a LinearSeq, for example)? If it can also return something else, then what determines the return type, and how can I influence it? I'm using Scala 2.8.0.RC3.

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• Ternary operators and variable reassignment in PHP

  - by TomcatExodus

  I've perused the questions on ternary operators vs. if/else structures, and while I understand that under normal circumstances there is no performance loss/gain in using ternary operators over if/else structures, I've not seen any mention of this situation. Language specific to PHP (but any language agnostic details are welcome) does the interpreter reassign values in situations like this: $foo = 'bar' $foo = strlen($foo) > 3 ? substr($foo, 0, 3) : $foo; Since this would evaluate to $foo = $foo; is this inefficient, or does the interpreter simply overlook/discard this evaluation? On a side note, what about: !defined('SECURE') ? exit : null;

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• Library for Dataflow in C

  - by msutherl

  How can I do dataflow (pipes and filters, stream processing, flow based) in C? And not with UNIX pipes. I recently came across stream.py. Streams are iterables with a pipelining mechanism to enable data-flow programming and easy parallelization. The idea is to take the output of a function that turns an iterable into another iterable and plug that as the input of another such function. While you can already do this using function composition, this package provides an elegant notation for it by overloading the operator. I would like to duplicate a simple version of this kind of functionality in C. I particularly like the overloading of the operator to avoid function composition mess. Wikipedia points to this hint from a Usenet post in 1990. Why C? Because I would like to be able to do this on microcontrollers and in C extensions for other high level languages (Max, Pd*, Python). * (ironic given that Max and Pd were written, in C, specifically for this purpose – I'm looking for something barebones)

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• Push notification or thread with timer

  - by neha

  Hi all, In my application, I'm having functionality like twitter that when you have not refreshed your screen, and if there're new messages then you get this message that "You have n new messages" and a refresh button, which on press will refresh the screen. I'm basically fetching all the data from an xml with some url. In case of thread, I need to call a timer after some time period which might affect the app performance. Can anybody please suggest wheather what will be better to use push notifications or thread with timer? Thanx in advance.

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• Spring 3.0 REST implementation or Jersey?

  - by hnilsen

  Hi, SO! I'm currently trying to figure out which implementation of JSR-311 I'm going to recommend further up the food chain. I've pretty much narrowed it down to two options - Spring 3.0 with it's native support for REST - or use Sun's own Jersey (Restlets might also be an option). To me it doesn't seem to be much of a difference in the actual syntax, but there might be issues with performance that I haven't figured out yet. The service is meant to replace some heavy-duty EJB's and make a RESTful Webservice instead. The load is expected to be rather high, up in the 100k users per day (max) range, but will be seriously load balanced. Thanks for all your insights.

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• Best choice for off-site backup: dd vs tar

  - by plok

  I have two 1TB single-partition hard disks configured as RAID1, of which I would like to make an off-site backup on a third disk, which I am still to buy. The idea is to store the backup at a relative's house, considerably far away from my place, in the hope that all the information will be safe in the case of a global thermonuclear apocalypse. Of course, this backup would be well encrypted. What I still have to decide is whether I am going to simply tar the entire partition or, instead, use dd to create an image of the disks. Is there any non-trivial difference between these two approaches that I could be overlooking? This off-site backup would be updated no more than two or three times a year, in the best of the cases, so performance should not be a factor to be pondered at all. What, and why, would you use if you were me? dd, tar, or a third option?

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• Where is Python support for PEM + RSA + DES3?

  - by jasonjs

  I need a Python library that supports PEM files and both RSA signing and DES3 encryption. pycrypto doesn't seem to support PEM, and its mechanism for loading existing keys is undocumented and cryptic. m2crypto doesn't seem to support DES/DES3, oddly. I've been running an openssl subprocess, but I'd rather have something built in and preferably fast. Does this exist? (Failing that, I hesitate to ask, but are there high-level enough C apis available for this that I could write a special-purpose extension without killing myself/introducing vulns?)

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• Indexing XMLType columns

  - by Chris

  Hello, I am working with a XMLType and currently experiencing significant performance issues and would like to incorporate indexing to the column type. Currently I am taking the approach of using the XMLTable() and XQuery functions to create a virtual table. I would like to use this Virtual Table to create a function based index on the table containing the XMLType, but I am receiving this error: Error report: SQL Error: ORA-00907: missing right parenthesis 00907. 00000 - "missing right parenthesis" *Cause: *Action: This is the index.. any assistance would be greatly appreciated. CREATE INDEX indx_medicinalproduct ON d.ProductName XMLTable('for $i at $a in /safetyreport/patient//drug for $j in $i/medicinalproduct return element r { $i/medicinalproduct }' PASSING s.safetyreport COLUMNS ProductName varchar2(70) PATH 'medicinalproduct') d;

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• Save application preferences... registry/file?

  - by spender

  Where is the best place to store application preferences? In particular, I'd like to save preferences for a media player such as volume levels and the like. Two candidates spring to mind... file and registry. Which would be more appropriate? As a follow up to this, I'm also wondering if there are any APIs that aid in creating application specific settings. Unless someone advises me that this is wrong, I'd like to save stuff either in HKCU... or HKLM/Software/MyCompanyName/MyAppName/Key for the registry, or in %APPDATA\MyCompanyName\MyAppName\someTypeOfSettingsFile. As these seem to be commonly used for such settings, I'd assume that .Net makes it easy to store settings in these locations. Is there a simple high level API that can .Net offer me to read and write settings to these common locations?

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• What factors could cause the scalability issue on a 10-core CPU?

  - by JackWM

  I am tuning the performance of parallel Java programs. And want to check the impacts from the Architecture. I'm look into the Intel 10-core CPU, Intel(R) Xeon(R) CPU E7-L8867. I found my program only scales up to 5 cores. What could be the causes? I'm considering the Architecture effects. e.g. memory contention? More specifically, Are the 10 cores symmetric to each other? How many memory controllers does it have?

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• Is scala functional programming slower than traditional coding?

  - by Fred Haslam

  In one of my first attempts to create functional code, I ran into a performance issue. I started with a common task - multiply the elements of two arrays and sum up the results: var first:Array[Float] ... var second:Array[Float] ... var sum=0f; for(ix<-0 until first.length) sum += first(ix) * second(ix); Here is how I reformed the work: sum = first.zip(second).map{ case (a,b) => a*b }.reduceLeft(_+_) When I benchmarked the two approaches, the second method takes 40 times as long to complete! Why does the second method take so much longer? How can I reform the work to be both speed efficient and use functional programming style?

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• Forced to use too many hidden fields; looking for an alternative approach

  - by harisri786

  I am looking for a better approach to do this. I have around 70 to 80 hidden fields in my page. This hidden fields are initialized at the server side and then used at the client side for validations, calculations, etc,. using java script. I wanted to know if there is any other alternative approach to using hidden fields in asp.net. I guess, these many hidden fields are increasing the page size and hence affecting the performance of my web page and I want to do away with it. FYI: I am working on an asp.net web application.

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• Restricting deletion with NHibernate

  - by FrontSvin

  I'm using NHibernate (fluent) to access an old third-party database with a bunch of tables, that are not related in any explicit way. That is a child tables does have parentID columns which contains the primary key of the parent table, but there are no foreign key relations ensuring these relations. Ideally I would like to add some foreign keys, but cannot touch the database schema. My application works fine, but I would really like impose a referential integrity rule that would prohibit deletion of parent objects if they have children, e.i. something similar 'ON DELETE RESTRICT' but maintained by NHibernate. Any ideas on how to approach this would be appreciated. Should I look into the OnDelete() method on the IInterceptor interface, or are there other ways to solve this? Of course any solution will come with a performance penalty, but I can live with that.

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• Is select() Ok to implemnet single socket read/write timeout ?

  - by chmike

  I have an application processing network communication with blocking calls. Each thread manages a single connection. I've added a timeout on the read and write operation by using select prior to read or write on the socket. Select is known to be inefficient when dealing with large number of sockets. But is it ok, in term of performance to use it with a single socket or are there more efficient methods to add timeout support on single sockets calls ? The benefit of select is to be portable.

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• Looking for a source code management system with a good GUI client

  - by Anders Öhrt

  We are currently using CS-RCS Pro for source code management, and are looking for to replace this due to performance issues. It is based on client side file access with no own protocol, which makes it painfully slow to use over a slow VPN line since it always rewrites the whole history of a file. It does however have a GUI client which is very simple and gives a great overview. We have three main requirements in a SCM: Fast. It must have a server side service or some other smart way so working with files with a large history is fast. A good Windows GUI client (not Explorer shell integration, not VS or Eclipse IDE integration), so working with files and branches is easy. The possibility to have several branches checked out at once in different directories. Does anyone have a recommendation of a SCM which fulfills there requirements?

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• Declaring variables for limited scope at the head of the for loop

  - by Helper Method

  In Java, you sometimes do something like this: for (int a = 1, b = 2; b < high;) { if (b % 2 == 0) { result += b; } int tmp = b; b = a + b; a = tmp; } Here, I used a for loop instead of a while loop to limit the scope of a and b. But how can I achieve this in JavaFX? The for loop doesn't seem to offer this possibility. Do I have to use a while loop?

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• Does HTML5 only replace the video aspects of Flash/Silverlight?

  - by John

  I see a lot of talk how HTML5 video tag will kill Flash. But while video is the most widely used part of Flash/SL, it's only a small part of their technical abilities. For instance you can write a game using full 3D graphics and socket connections in Flex, and serious business applications, etc. Is the thinking that Javascript will kill those parts of Flash/Flex/SL? Because while that seems feasible now for even quite rich web-apps, what about any kind of high-performance app like real-time graphics?

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• ANY material writen in/for DELPHI around the graphics topic?

  - by José Eduardo

  Does anyone knows ANY material writen in/for DELPHI around the graphics topic? Planning to build a software for medical imaging processing . Thinking in 3D UI to absorve the power of nvidias GTX graphics card, and some real-time 2D processing integrated with high-end scanners. Please dont take this as a "rant" but, we have zillions of C++ books writen about that kind of topic and nothing for pascal/delphi. If you have some experience could you comment about that? Is it better to learn c++, to have access to that material? Can i go with delphi? I have experience with delphi, but none with graphics... And i have a deadline... Thanks.

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• Erlang Question - Time order of messages

  - by Aiden Bell

  Read (skimmed enough to get coding) through Erlang Programming and Programming Erlang. One question, which is as simple as it sounds: If you have a process Pid1 on machine m1 and a billion million messages are sent to Pid1, are messages handled in parallel by that process (I get the impression no) and(answered below) is there any guarantee of order when processing messages? ie. Received in order sent? If so, how is clock skew handled in high traffic situations for ordering? Coming from the whole C/Thread pools/Shared State background ... I want to get this concrete. I understand distributing an application, but want to ensure the 'raw bones' are what I expect before building processes and distributing workload. Also, am I right in thinking the whole world is currently flicking through Erlang texts ;)

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• How can I get the "Latency" of a process that has a TCP connection open?

  - by Dave

  Hello, I am looking to get the "Latency" field of a TCP connection. I notice windows Resource Monitor has this field, and I was wondering if there was a way I can find it. Preferrably without using WMI. If you are unsure what field I am talking about, open Task Manager, goto the Performance tab and hit the Resource Monitor button. Once Resource Monitor is open, expand the TCP Connections area and you will see a Latency field. Is there anyway to access this programatically? Thanks!

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• Response.Redirect exception

  - by Tedd Hansen

  Executing the line: Response.Redirect("Whateva.aspx", true); Results in: A first chance exception of type 'System.Threading.ThreadAbortException' occurred in mscorlib.dll An exception of type 'System.Threading.ThreadAbortException' occurred in mscorlib.dll but was not handled in user code The exception is because of the "true" part, telling it to end the current request immediately. Is this how it should be? If we consider: Exceptions are generally considered heavy, and many times the reason for ending the request early is to avoid processing the rest of the page. Exceptions show up in performance monitoring, so monitoring the solution will show a false number of exceptions. Is there an alternative way to achieve the same?

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• Is there any disadvantage to putting API code into a JAR along with the classes?

  - by Adam Gent

  In Java if you package the source code (.java) files into the jar along with classes (.class) most IDE's like eclipse will show the javadoc comments for code completion. IIRC there are few open-source projects that do this like JMock. Lets say I have cleanly separated my API code from implementation code so that I have something like myproject-api.jar and myproject-impl.jar is there any reason why I should not put the source code in my myproject-api.jar ? Because of Performance? Size? Why don't other projects do this?

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