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• Provider claiming "all web servers in the cloud are automatically kept in sync" - should I be skeptical?

  - by RobMasters

  I'm no expert in cloud computing - I've spent a fair bit of time researching it and various providers but am yet to get any hands-on experience with it. From what I've read about AWS and auto-scaling EC2 instances though, it seems as though each instance should be completely decoupled from all other instances. i.e. If content is uploaded to the web server's local filesystem from a custom CMS backend then that content won't be available if subsequently requested from a different web server in the auto-scaling group. Is that right? I met with a representative of our existing hosting provider recently and he was claiming that it isn't a problem that our legacy CMS system is highly dependent on having a local filesystem. He said that all web servers, regardless of how many, would be kept as exact duplicates so I shouldn't notice any difference compared to our existing setup of a single dedicated server. This smells a little too much like bull fecal-matter to me...should I be skeptical about this? I'm a little worried because my (non-technical) boss who ultimately makes the decisions is all for signing up to this cloud solution because it won't require any extra work. I'm sure that they must at least be able to provide this, otherwise they wouldn't be attempting to sell it to us. But at what cost? It sounds as though each web server will always need to be checking the other web server(s) for new static content, which to me sounds like unwanted overhead that'll slow things down. I'd really appreciate it if somebody could clear this up to me. I'm all for switching to AWS and using S3+CloudFront for all static content, but that isn't looking very likely to happen at the moment.

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• Diagnosing RAM issues

  - by TaylorND

  I have an old Acer Aspire T180 desktop. The specs are as follows: AMD Athlon 64 3800+ 2.4GHz 1GB DDR2 SDRAM 160GB DVD-Writer (DVD±R/±RW) Gigabit Ethernet 17" Active Matrix TFT Color LCD Windows Vista Home Basic Mini-tower AST180-UA381B According to the information in the computer's documentation the computer comes with 1 GB of RAM. It has two DDR2 SDRAM sticks. I used to have Windows Vista installed. Then I removed it and install Windows 7, and now I have since removed Windows 7 and installed Windows XP. According to Windows XP with both RAM sticks in the computer has 768 MB. Isn't this supposed to be 1 GB of RAM or 1024 MB of RAM? Is the amount of RAM installed only partly used by the Operating System? Is there's something I'm missing? If I remove either one of the RAM sticks I'm left with 448 MB of RAM. These numbers don't seem to add up. If each of the RAM sticks contains at least 448 MB of RAM shouldn't they (both being in) provide 896 MB of RAM. Even then, isn't that less than a GB of RAM? I'm not too experienced in hardware so I thought this would be the best place to ask. As a follow up question, is the RAM I have enough to run/multitask with Windows XP efficiently? I plan to do a lot of computing with the system (although not gaming), should I invest in more RAM?

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• PXELinux and compressed kernels/images

  - by Yvan JANSSENS

  Is it possible to boot compressed kernels with a compressed initrd with PXELinux? First, a little background: We created a custom Linux distro, for diskless OpenCL computing nodes. We want those nodes to fetch their OS from the network. Our Distro is composed out of a kernel (duh) and a large initrd which is loaded into RAM and everything is executed from there. We chose to run everything off the initrd for two reasons: NFS was not an option to serve the filesystem's extra contents Fast file access from RAM. No persistent storage needed, data and config is pulled dynamically through a SOAP service. Now our initrd is about 450M in size. At our network speeds, it takes about two to three minutes to load a single client. Will compression speed up te downloading, and if yes, which one should be used? Is LZMA supported by PXELinux, or do we need to stick to bzip2 or gzip? Because of the 2-3 minutes loading time, booting 15 nodes over the same network link takes quite a lot of time. We decided not to use hard drives or CD/DVD drives, for financial reasons (cheapest HDD @ €30 times 15 is a lot of money saved ;-) ) So, our question is: what compression options are available for this setup? And how do we do this? Thank you for your time! Yvan Janssens

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• The long road to bug-free software

  - by Tony Davis

  The past decade has seen a burgeoning interest in functional programming languages such as Haskell or, in the Microsoft world, F#. Though still on the periphery of mainstream programming, functional programming concepts are gradually seeping into the imperative C# language (for example, Lambda expressions have their root in functional programming). One of the more interesting concepts from functional programming languages is the use of formal methods, the lofty ideal behind which is bug-free software. The idea is that we write a specification that describes exactly how our function (say) should behave. We then prove that our function conforms to it, and in doing so have proved beyond any doubt that it is free from bugs. All programmers already use one form of specification, specifically their programming language's type system. If a value has a specific type then, in a type-safe language, the compiler guarantees that value cannot be an instance of a different type. Many extensions to existing type systems, such as generics in Java and .NET, extend the range of programs that can be type-checked. Unfortunately, type systems can only prevent some bugs. To take a classic problem of retrieving an index value from an array, since the type system doesn't specify the length of the array, the compiler has no way of knowing that a request for the "value of index 4" from an array of only two elements is "unsafe". We restore safety via exception handling, but the ideal type system will prevent us from doing anything that is unsafe in the first place and this is where we start to borrow ideas from a language such as Haskell, with its concept of "dependent types". If the type of an array includes its length, we can ensure that any index accesses into the array are valid. The problem is that we now need to carry around the length of arrays and the values of indices throughout our code so that it can be type-checked. In general, writing the specification to prove a positive property, even for a problem very amenable to specification, such as a simple sorting algorithm, turns out to be very hard and the specification will be different for every program. Extend this to writing a specification for, say, Microsoft Word and we can see that the specification would end up being no simpler, and therefore no less buggy, than the implementation. Fortunately, it is easier to write a specification that proves that a program doesn't have certain, specific and undesirable properties, such as infinite loops or accesses to the wrong bit of memory. If we can write the specifications to prove that a program is immune to such problems, we could reuse them in many places. The problem is the lack of specification "provers" that can do this without a lot of manual intervention (i.e. hints from the programmer). All this might feel a very long way off, but computing power and our understanding of the theory of "provers" advances quickly, and Microsoft is doing some of it already. Via their Terminator research project they have started to prove that their device drivers will always terminate, and in so doing have suddenly eliminated a vast range of possible bugs. This is a huge step forward from saying, "we've tested it lots and it seems fine". What do you think? What might be good targets for specification and verification? SQL could be one: the cost of a bug in SQL Server is quite high given how many important systems rely on it, so there's a good incentive to eliminate bugs, even at high initial cost. [Many thanks to Mike Williamson for guidance and useful conversations during the writing of this piece] Cheers, Tony.

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• What is the fall off of subsecond throughput on Ethernet Network Interfaces

  - by Kyle Brandt

  On a network interface, speeds are given in term of data over time, in particular, they are bits per second. However, in the uber-fast world of computing -- a second is kind of a really long time. So for example, given a linear falloff. A 1 GBit per second interface would do 500MBit per half second, 250Mbit per quarter second etc. I imagine at certain units of time, this is no longer linear. Perhaps this is set by ethernet frequencies, system clock speeds, interrupt timers etc. I am sure this varies depending on the system -- but does anyone have more information or whitepapers on this? One of the main reasons I am curious is to understand output drops on interfaces. Even if the speed per second is much lower than the interface can handle -- perhaps there are spikes that cause drops for only small numbers of milliseconds. Perhaps various coalescing would hide this effect -- or perhaps increase it on the receiving interface? Do queues make a difference here? Example: So given if this is linear down to the MS we would have 1Mbit/MS, and if Wireshark isn't distorting what I see, should I see drops when I have a spike beyond 1Mbit?

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• Mixing both local and nonlocal addresses on three switches

  - by klew

  I have four computers that have nonlocal addresses like 150.X.X.X. Now I also get another few computers that should be only accessible through a gateway (it will be computing cluster) and they addresses are 10.0.0.X. I also wanted to include those four older computers to this new cluster, but I want them to be accessible from internet on nonlocal addresses (so I would like to set up them on both 150.X.X.X and 10.0.0.X addresses - I've set up it as interface eth0:0 since I have only one NIC). Those new computers have their switch and old computers also have their own switch. Both of them are connected to another (third) switch. The problem is that those old computers see each other (I can ping them), and also new computers see each other, but I can't ping old computer from new computer and vice versa. However pinging on nonlocal adresses works as expected. I looked into switch configuration and didn't find anything useful. I have no idea what I missed here. Can somebody help? All computers have Ubuntu Server 10.04

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• Am I safe on Windows if I continue like this?

  - by max

  Of all the available tons of anti-malware software for Windows all over the internet, I've never used any paid solution(I am a student, I have no money). Since the last 10 years, my computers running Windows have never been hacked/compromised or infected so badly that I had to reformat them(of course I did reformat them for other reasons). The only program I have for security is Avast Home Edition, which is free, installed on my computers. It has never caused any problems; always detected malware, updated automatically, has an option to sandbox programs and everything else I need. Even if I got infected, I just did a boot-time scan with it, downloaded and ran Malwarebytes, scanned Autoruns logs, checked running processes with Process Explorer and did some other things and made sure I cleaned my computer. I am quite experienced and I've always taken basic precautions like not clicking suspicious executables, not going to sites which are suspicious according to WOT, and all that blah. But recently I've been doing more and more online transactions and since its 2012 now, I'm doubtful whether I need more security or not. Have I been just lucky, or do my computing habits obviate the need to use any more(or paid) security software?

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• thought about shared storage (NFS, Lustre) [closed]

  - by user134880

  Possible Duplicate: Can you help me with my capacity planning? Now I habe small cluster with total of 8 nodes. 6 of them are computing nodes (apache and vmware) and 2 nodes are for storage. 2 storage nodes are identical. Each storage server is linux box with 8 x 1Tb WD RE4 in soft raid 10. 1st box is master and 2nd is slave. Data is mirrored with DRDB. We export NFSv4 shares to Apache (for document root) and iSCSI to Vmware. Now all is working pretty good and stable. But it will be soon time to upgrade our system. I have been thinking of Lustre. Does some one has any real experience with Lustre or NFS medium clusters? Will it be good idea just to upgrade server and change hdd's to 3Tb ? With NFS we will always have only 2 servers to maintain (one primary and one slave). Thanks. QUESTIONS: 1) Does some one used Lustre? In production? I have seen a lot of info about how it is hard to setup Lustre because you need to compile own kernel and patches. It's answers from newbies. Is there some one who has used Lustre for some period of time? 2) About disk upgrades - it's only description of strategy. I'm not asking if it is enough 3Tb or not. I just ask if it is right just to replace hdds instead of adding new server (like with Lustre) Thanks again.

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• Nvidia 9800GT randomly prevents computer from booting

  - by Blender

  My computer has been running Windows and Linux perfectly fine with my 9800GT for the past year or so, but today it refused to boot. When I press the power button, this is what happens: Power button flashes once. Fans whir. Graphics card makes clicking noise. Computer reboots. Go back to 1. The cycle just keeps going, and I have to yank the cord to make the computer stop. After about 30 attempts at booting it, the computer powers on and everything works. I'm pretty sure that the graphics card isn't malfunctioning, as I've been GPU computing on it for a while now without any hiccups. But the strange thing is, the computer boots perfectly fine in only 5 boots if I remove the card. The computer is a HP Pavilion a6028x Desktop PC: Processor: AMD Athlon 64 X2 (W) 4600+ 2.4 GHz (AM2 socket) Motherboard: ECS MCP61PM-HM (Nettle 1) RAM: 3GB DDR2 (two different brands) More specs here Does anybody know what could be the problem? Any help or information would be greatly appreciated!

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• Network using only switches

  - by mschultz

  So I'm not a network guy - but here's what I want to do - I have an existing network using wifi, which I like, and which is used to connect several computers to the internet. It is headed up by a router, which is in another part of the building. Three of those computers are in my office. All three have gigabit wired ethernet. I have a gigabit switch. Here's what I want to do: Build a 2nd network, out of just that switch, which allows all 3 computers to connect to each other (just to each other is fine, for this purpose, they need no internet). I have a distributed computing task (rendering high-quality fractal artwork, as it were), that requires the best connection speed to all 3 computers. I want them to be able to "talk to each other" as quickly as possible, with the fewest dropped packets (the dataflow over this network will be quite high). So how do I do this. I'm not a networking guy at all - I tried connecting them all, and nobody got an IP address (which I assume is because nobody is running a DNS server?). What all do I need to do to make this work? PS - two are running windows, one is running ubuntu.

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• WebLogic stuck thread protection

  - by doublep

  By default WebLogic kills stuck threads after 15 min (600 s), this is controlled by StuckThreadMaxTime parameter. However, I cannot find more details on how exactly "stuckness" is defined. Specifically: What is the point at which 15 min countdown begins. Request processing start? Last wait()-like method? Something else? Does this apply only to request-processing threads or to all threads? I.e. can a request-processing thread "escape" this protection by spawning a worker thread for a long task? Especially, can it delegate response writing to such a worker without 15 min countdown? My usecase is download of huge files through a permission system. Since a user needs to be authenticated and have permissions to view a file, I cannot (or at least don't know how) leave this to a simple HTTP server, e.g. Apache. And because files can be huge, download could (at least in theory) take more than 15 minutes.

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• WCF ChannelFactory caching

  - by Myles J

  I've just read this great article on WCF ChannelFactory caching by Wenlong Dong. My question is simply how can you actually prove that the ChannelFactory is in fact being cached between calls? I've followed the rules regarding the ClientBase’s constructors. We are using the following overloaded constructor on our object that inherits from ClientBase: ClientBase(string endpointConfigurationName, EndpointAddress remoteAddress); In the article mentioned above it is stated that: For these constructors, all arguments (including default ones) are in the following list: · InstanceContext callbackInstance · string endpointConfigurationName · EndpointAddress remoteAddress As long as these three arguments are the same when ClientBase is constructed, we can safely assume that the same ChannelFactory can be used. Fortunately, String and EndpointAddress types are immutable, i.e., we can make simple comparison to determine whether two arguments are the same. For InstanceContext, we can use Object reference comparison. The type EndpointTrait is thus used as the key of the MRU cache. To test the ChannelFactory cache theory we are checking the Hashcode in the ClientBase constructor e.g. var testHash = RuntimeHelpers.GetHashCode(base.ChannelFactory); The hash value is different between calls which makes us think that the ChannelFactory isn't actually cached. Any thoughts? Regards Myles

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• Gomoku array-based AI-algorithm?

  - by Lasse V. Karlsen

  Way way back (think 20+ years) I encountered a Gomoku game source code in a magazine that I typed in for my computer and had a lot of fun with. The game was difficult to win against, but the core algorithm for the computer AI was really simply and didn't account for a lot of code. I wonder if anyone knows this algorithm and has some links to some source or theory about it. The things I remember was that it basically allocated an array that covered the entire board. Then, whenever I, or it, placed a piece, it would add a number of weights to all locations on the board that the piece would possibly impact. For instance (note that the weights are definitely wrong as I don't remember those): 1 1 1 2 2 2 3 3 3 444 1234X4321 3 3 3 2 2 2 1 1 1 Then it simply scanned the array for an open location with the lowest or highest value. Things I'm fuzzy on: Perhaps it had two arrays, one for me and one for itself and there was a min/max weighting? There might've been more to the algorithm, but at its core it was basically an array and weighted numbers Does this ring a bell with anyone at all? Anyone got anything that would help?

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• Synchronizing Asynchronous request handlers in Silverlight environment

  - by Eric Lifka

  For our senior design project my group is making a Silverlight application that utilizes graph theory concepts and stores the data in a database on the back end. We have a situation where we add a link between two nodes in the graph and upon doing so we run analysis to re-categorize our clusters of nodes. The problem is that this re-categorization is quite complex and involves multiple queries and updates to the database so if multiple instances of it run at once it quickly garbles data and breaks (by trying to re-insert already used primary keys). Essentially it's not thread safe, and we're trying to make it safe, and that's where we're failing and need help :). The create link function looks like this: private Semaphore dblock = new Semaphore(1, 1); // This function is on our service reference and gets called // by the client code. public int addNeed(int nodeOne, int nodeTwo) { dblock.WaitOne(); submitNewNeed(createNewNeed(nodeOne, nodeTwo)); verifyClusters(nodeOne, nodeTwo); dblock.Release(); return 0; } private void verifyClusters(int nodeOne, int nodeTwo) { // Run analysis of nodeOne and nodeTwo in graph } All copies of addNeed should wait for the first one that comes in to finish before another can execute. But instead they all seem to be running and conflicting with each other in the verifyClusters method. One solution would be to force our front end calls to be made synchronously. And in fact, when we do that everything works fine, so the code logic isn't broken. But when it's launched our application will be deployed within a business setting and used by internal IT staff (or at least that's the plan) so we'll have the same problem. We can't force all clients to submit data at different times, so we really need to get it synchronized on the back end. Thanks for any help you can give, I'd be glad to supply any additional information that you could need!

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• UITabbar without controller

  - by Etienne

  Hello. I have a simple app where the only view controller has an outlet to a UITabBar. It also implements UITabBarDelegate and is set as the delegate for the UITabBar: @interface TheMainViewController : UIViewController <UITabBarDelegate> { IBOutlet UITabBar *theTabBar; } I implemented the following method Which gets called whenever any of my 4 UITabBarItems get tapped. I tried just doing something really simple: - (void)tabBar:(UITabBar *)tabBar didSelectItem:(UITabBarItem *)item { tabBar.selectedItem = [tabBar.items objectAtIndex:0]; return; } In theory, it should always stay selected on my first tab and it works perfectly when I just tap any UITabBarItem (nothing happens, the first one always stays selected). But when I touch a UITabBarItem and hold it (not taking my finger off) the selection changes anyway ! Debugging, everything gets called properly. It's like changing the selectedItem property doesn't have any effect is the user still has the item "down" (with his finger on it). What would be a good workaround? I tried overloading UITabBar and messing with touchesBegan and touchesEnd but they don't even get called. Same with UITabBarItem. Oh and please don't suggest using a UITabBarController as it is not flexible enough for my application. So frustrating....thanks!

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• WCF push to client through firewall?

  - by Sire

  See also How does a WCF server inform a WCF client about changes? (Better solution then simple polling, e.g. Coment or long polling) I need to use push-technology with WCF through client firewalls. This must be a common problem, and I know for a fact it works in theory (see links below), but I have failed to get it working, and I haven't been able to find a code sample that demonstrates it. Requirements: WCF Clients connects to server through tcp port 80 (netTcpBinding). Server pushes back information at irregular intervals (1 min to several hours). Users should not have to configure their firewalls, server pushes must pass through firewalls that have all inbound ports closed. TCP duplex on the same connection is needed for this, a dual binding does not work since a port has to be opened on the client firewall. Clients sends heartbeats to server at regular intervals (perhaps every 15 mins) so server knows client is still alive. Server is IIS7 with WAS. The solution seems to be duplex netTcpBinding. Based on this information: WCF through firewalls and NATs Keeping connections open in IIS But I have yet to find a code sample that works.. I've tried combining the "Duplex" and "TcpActivation" samples from Microsoft's WCF Samples without any luck. Please can someone point me to example code that works, or build a small sample app. Thanks a lot!

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• Sample uniformly at random from an n-dimensional unit simplex.

  - by dreeves

  Sampling uniformly at random from an n-dimensional unit simplex is the fancy way to say that you want n random numbers such that they are all non-negative, they sum to one, and every possible vector of n non-negative numbers that sum to one are equally likely. In the n=2 case you want to sample uniformly from the segment of the line x+y=1 (ie, y=1-x) that is in the positive quadrant. In the n=3 case you're sampling from the triangle-shaped part of the plane x+y+z=1 that is in the positive octant of R3: (Image from http://en.wikipedia.org/wiki/Simplex.) Note that picking n uniform random numbers and then normalizing them so they sum to one does not work. You end up with a bias towards less extreme numbers. Similarly, picking n-1 uniform random numbers and then taking the nth to be one minus the sum of them also introduces bias. Wikipedia gives two algorithms to do this correctly: http://en.wikipedia.org/wiki/Simplex#Random_sampling (Though the second one currently claims to only be correct in practice, not in theory. I'm hoping to clean that up or clarify it when I understand this better. I initially stuck in a "WARNING: such-and-such paper claims the following is wrong" on that Wikipedia page and someone else turned it into the "works only in practice" caveat.) Finally, the question: What do you consider the best implementation of simplex sampling in Mathematica (preferably with empirical confirmation that it's correct)? Related questions http://stackoverflow.com/questions/2171074/generating-a-probability-distribution http://stackoverflow.com/questions/3007975/java-random-percentages

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• Ruby - Feedzirra and updates

  - by mplacona

  Hi, trying to get my head around Feedzirra here. I have it all setup and everything, and can even get results and updates, but something odd is going on. I came up with the following code: def initialize(feed_url) @feed_url = feed_url @rssObject = Feedzirra::Feed.fetch_and_parse(@feed_url) end def update_from_feed_continuously() @rssObject = Feedzirra::Feed.update(@rssObject) if @rssObject.updated? puts @rssObject.new_entries.count else puts "nil" end end Right, what I'm doing above, is starting with the big feed, and then only getting updates. I'm sure I must be doing something stupid, as even though I'm able to get the updates, and store them on the same instance variable, after the first time, I'm never able to get those again. Obviously this happens because I'm overwriting my instance variable with only updates, and lose the full feed object. I then thought about changing my code to this: def update_from_feed_continuously() feed = Feedzirra::Feed.update(@rssObject) if feed.updated? puts feed.new_entries.count else puts "nil" end end Well, I'm not overwriting anything and that should be the way to go right? WRONG, this means I'm doomed to always try to get updates to the same static feed object, as although I get the updates on a variable, I'm never actually updating my "static feed object", and newly added items will be appended to my "feed.new_entries" as they in theory are new. I'm sure I;m missing a step here, but I'd really appreciate if someone could shed me a light on it. I've been going through this code for hours, and can't get to grips with it. Obviously it should work fine, if I did something like: if feed.updated? puts feed.new_entries.count @rssObject = initialize(@feed_url) else Because that would reinitialize my instance variable with a brand new feed object, and the updates would come again. But that also means that any new update added on that exact moment would be lost, as well as massive overkill, as I'd have to load the thing again. Thanks in advance!

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• PHPUnit Selenium captureScreenshotOnFailure does not work?

  - by user342775

  I am using PHPUnit 3.4.12 to drive my selenium tests. I'd like to be able to get a screenshot taken automatically when a test fails. This should be supported as explained at http://www.phpunit.de/manual/current/en/selenium.html#selenium.seleniumtestcase.examples.WebTest2.php class WebTest { protected $captureScreenshotOnFailure = true; protected $screenshotPath = 'C:\selenium'; protected $screnshotUrl = 'http://localhost/screenshots'; public function testLandingPage($selenium) { $selenium->open("http://www.example.com"); $selenium->fail("fail"); ... } } As you can see, I am making the test to fail and in theory when it does it should take a screenshot and put it in C:\selenium, as I am running the selenium RC server on Windows. However, when I run the test it will just give me the following: [root@testbox selenium]$ sh run PHPUnit 3.4.12 by Sebastian Bergmann. F Time: 8 seconds, Memory: 5.50Mb There was 1 failure: 1) WebTest::testLandingPage fail /home/root/selenium/WebTest.php:32 FAILURES! Tests: 1, Assertions: 0, Failures: 1. I do not see any screenshot in C:\selenium. I can however get a screenshot with $selenium-captureScreenshot("C:/selenium/image.png"); Any ideas or suggestions most welcome. Thanks

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• Implementing a 2 Legged OAuth Provider

  - by Rob Wilkerson

  I'm trying to find my way around the OAuth spec, its requirements and any implementations I can find and, so far, it really seems like more trouble than its worth because I'm having trouble finding a single resource that pulls it all together. Or maybe it's just that I'm looking for something more specialized than most tutorials. I have a set of existing APIs--some in Java, some in PHP--that I now need to secure and, for a number of reasons, OAuth seems like the right way to go. Unfortunately, my inability to track down the right resources to help me get a provider up and running is challenging that theory. Since most of this will be system-to-system API usage, I'll need to implement a 2-legged provider. With that in mind... Does anyone know of any good tutorials for implementing a 2-legged OAuth provider with PHP? Given that I have securable APIs in 2 languages, do I need to implement a provider in both or is there a way to create the provider as a "front controller" that I can funnel all requests through? When securing PHP services, for example, do I have to secure each API individually by including the requisite provider resources on each? Thanks for your help.

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• Setting httponly in JSESSIONID cookie (Java EE 5)

  - by mythandros

  I'm trying to set the httponly flag on the JSESSIONID cookie. I'm working in Java EE 5, however, and can't use setHttpOnly(). First I tried to create my own JSESSIONID cookie from within the servlet's doPost() by using response.setHeader(). When that didn't work, I tried response.addHeader(). That didn't work either. Then, I learned that the servlet handled converting the session into a JSESSIONID cookie and inserting it into the http header so if I want to play with that cookie, I'll have to write a filter. I wrote a filter and played with setHeader()/addHeader() there, again to no avail. Then, I learned that there's some flush/close action going on in the response object before it gets to the filter so if I want to manipulate the data, I need to extend HttpServletResponseWrapper and pass that to filterChain.doFilter(). This is done but I'm still not getting results. Clearly I'm doing something wrong but I don't know what. I'm not sure if this is at all relevant to the question at hand but no html document is being returned by the servlet to the browser. All that's really happening is that some objects are being populated and returned to a JSP document. I've sort of assumed that The Session object is turned into a JSESSIONID cookie and wrapped -- along with the objects added to the request -- in an http header before being sent to the browser. I'd be happy to post some code but I want to rule out the possibility that my difficulties stem from a misunderstanding of the theory first.

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• Facebooker Causing Problems with Rails Integration Testing

  - by Eric Lubow

  I am (finally) attempting to write some integration tests for my application (because every deploy is getting scarier). Since testing is a horribly documented feature of Rails, this was the best I could get going with shoulda. class DeleteBusinessTest < ActionController::IntegrationTest context "log skydiver in and" do setup do @skydiver = Factory( :skydiver ) @skydiver_session = SkydiverSession.create(@skydiver) @biz = Factory( :business, :ownership = Factory(:ownership, :skydiver = @skydiver )) end context "delete business" do setup do @skydiver_session = SkydiverSession.find post '/businesses/destroy', :id = @biz.id end should_redirect_to('businesses_path()'){businesses_path()} end end end In theory, this test seems like it should pass. My factories seem like they are pushing the right data in: Factory.define :skydiver do |s| s.sequence(:login) { |n| "test#{n}" } s.sequence(:email) { |n| "test#{n}@example.com" } s.crypted_password '1805986f044ced38691118acfb26a6d6d49be0d0' s.password 'secret' s.password_confirmation { |u| u.password } s.salt 'aowgeUne1R4-F6FFC1ad' s.firstname 'Test' s.lastname 'Salt' s.nickname 'Mr. Password Testy' s.facebook_user_id '507743444' end The problem I am getting seems to be from Facebooker only seems to happen on login attempts. When the test runs, I am getting the error: The error occurred while evaluating nil.set_facebook_session. I believe that error is to be expected in a certain sense since I am not using Facebook here for this session. Can anyone provide any insight as to how to either get around this or at least help me out with what is going wrong?

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• Excel export displaying '#####...'

  - by Cypher

  I'm trying to export an Excel database into .txt (Tab Delimited), but some of my cells are quite large. When I export into a txt some of the cells are exported as '#######....' which is surprisingly useless. Has this happened to anyone else? Do you know an easy fix? Data from one cell of my column: Accounting, African Studies, Agricultural/Bioresource Engineering, Agricultural Economics, Agricultural Science, Anatomy/Cell Biology, Animal Biology, Animal Science, Anthropology, Applied Zoology, Architecture, Art History, Atmospheric/Oceanic Science, Biochemistry, Biology, Botanical Sciences, Canadian Studies, Chemical Engineering, Chemistry/Bio-Organic/Environmental/Materials,ChurchMusicPerformance, Civil Engineering/Applied Mechanics, Classics, Composition, Computer Engineering,ComputerScience, ContemporaryGerman Studies, Dietetics, Early Music Performance, Earth/Planetary Sciences, East Asian Studies, Economics, Electrical Engineering, English Literature/ Drama/Theatre/Cultural Studies, Entrepreneurship, Environment, Environmental Biology, Finance, Food Science, Foundations of Computing, French Language/Linguistics/Literature/Translation, Geography, Geography/ Urban Systems, German, German Language/Literature/Culture, Hispanic Languages/Literature/Culture,History,Humanistic Studies, Industrial Relations, Information Systems, International Business, International Development Studies, Italian Studies/Medieval/Renaissance, Jazz Performance, Jewish Studies, Keyboard Studies, Kindergarten/Elementary Education, Kindergarten/Elementary Education/Jewish Studies,Kinesiology, Labor/Management Relations, Latin American/Caribbean Studies, Linguistics, Literature/Translation, Management Science, Marketing, Materials Engineering,Mathematics,Mathematics/Statistics,Mechanical Engineering, Microbiology, Microbiology/Immunology, Middle Eastern Studies, Mining Engineering, Music, Music Education, MusicHistory,Music Technology,Music Theory,North American Studies, Nutrition,OperationsManagement,OrganizationalBehavior/Human Resources Management, Performing Arts, Philosophy, Physical Education, Physics, Physiology, Plant Sciences, Political Science, Psychology, Quebec Studies, Religious Studies/Scriptures/Interpretations/World Religions,ResourceConservation,Russian, Science for Teachers,Secondary Education, Secondary Education/Music, Secondary Education/Science, SocialWork, Sociology, Software Engineering, Soil Science, Strategic Management, Teaching of French/English as a Second Language, Theology, Wildlife Biology, Wildlife Resources, Women’s Studies.

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• Nested Routes and Parameters for Rails URLs (Best Practice)

  - by viatropos

  Hey there, I have a decent understanding of RESTful urls and all the theory behind not nesting urls, but I'm still not quite sure how this looks in an enterprise application, like something like Amazon, StackOverflow, or Google... Google has urls like this: http://code.google.com/apis/ajax/ http://code.google.com/apis/maps/documentation/staticmaps/ https://www.google.com/calendar/render?tab=mc Amazon like this: http://www.amazon.com/books-used-books-textbooks/b/ref=sa_menu_bo0?ie=UTF8&node=283155&pf_rd_p=328655101&pf_rd_s=left-nav-1&pf_rd_t=101&pf_rd_i=507846&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=1PK4ZKN4YWJJ9B86ANC9 http://www.amazon.com/Ruby-Programming-Language-David-Flanagan/dp/0596516177/ref=sr_1_1?ie=UTF8&s=books&qid=1258755625&sr=1-1 And StackOverflow like this: http://stackoverflow.com/users/169992/viatropos http://stackoverflow.com/questions/tagged/html http://stackoverflow.com/questions/tagged?tagnames=html&sort=newest&pagesize=15 So my question is, what is best practice in terms of creating urls for systems like these? When do you start storing parameters in the url, when don't you? These big companies don't seem to be following the rules so hotly debated in the ruby community (that you should almost never nest URLs for example), so I'm wondering how you go about implementing your own urls in larger scale projects because it seems like the idea of not nesting urls breaks down at anything larger than a blog. Any tips?

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• Why does the the Java VM not recover after "Too many open files" errors?

  - by Michael

  In certain well-understood circumstances, our application will open too many sockets (database connections) and reach the maximum open files that the OS allows. We understand this; we are fixing the issue and also bumping up the limit. What we can't explain is why parts of our application don't recover even after the number of connections abates and we're well within the limit. In this case, it's an application running under Tomcat. When this happens, we first start seeing "Too many open files" errors: SEVERE: Socket accept failed java.net.SocketException: Too many open files at java.net.PlainSocketImpl.socketAccept(Native Method) at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:390) at java.net.ServerSocket.implAccept(ServerSocket.java:453) at java.net.ServerSocket.accept(ServerSocket.java:421) at org.apache.tomcat.util.net.DefaultServerSocketFactory.acceptSocket(DefaultServerSocketFactory.java:61) at org.apache.tomcat.util.net.JIoEndpoint$Acceptor.run(JIoEndpoint.java:310) at java.lang.Thread.run(Thread.java:619) Eventually, we start seeing NoClassDefFoundErrors inside an application thread that's trying to open HTTP connections: java.lang.NoClassDefFoundError: org/apache/commons/httpclient/protocol/ControllerThreadSocketFactory at org.apache.commons.httpclient.protocol.DefaultProtocolSocketFactory.createSocket(DefaultProtocolSocketFactory.java:128) at org.apache.commons.httpclient.HttpConnection.open(HttpConnection.java:707) at org.apache.commons.httpclient.MultiThreadedHttpConnectionManager$HttpConnectionAdapter.open(MultiThreadedHttpConnectionManager.java:1349) [...] Caused by: java.lang.ClassNotFoundException: org.apache.commons.httpclient.protocol.ControllerThreadSocketFactory at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1387) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1233) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320) ... 8 more When the errant connections go away, the server starts accepting connections again, and everything seems ok, but we're left with the latter error constantly being spewed to stderr. Although the application typically logs unloaded classes to stdout, I don't see any such logs just before, during or after the "Too many open files" errors. My initial theory was that the Hotspot JVM would unload seemingly unused classes when it encounters "Too many open files," but if so, it doesn't log the fact. I'd also expect it to recover if that were the case. Platform details: Java(TM) SE Runtime Environment (build 1.6.0_14-b08) Java HotSpot(TM) 64-Bit Server VM (build 14.0-b16, mixed mode) Apache Tomcat Version 6.0.18

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