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  • Two Candidates + One Job = Two Different Outcomes

    - by david.talamelli
    Recruiters have always headhunted (sidenote: I do not like this word, in general I think the type of people who use the phrase “headhunting” are the ones who are trying to sound more important than what they likely are). Any serious Recruiter engages in direct recruiting activity, it is part and parcel of the business it is not something unique. With the uptake in Social Media the past 4-5 years, we have seen an increase in the number of Recruiters proactively reaching out to people about job opportunities. We have also seen this activity increase across all levels of hire, from help desk roles to C-Level Executives. While getting approached about a role can be a nice boost to a person’s ego, do not let it give you an inflated sense of entitlement. It is The way that people handle themselves during these calls and subsequent interviews will have a large impact on their potential to land that job. Last week I spoke to two very different candidates, both about the same position and both with very different outcomes. On paper, Candidate #1 looked fantastic; they ticked many of the boxes that we were looking for. The person is working at global IT company and working in a similar role as the one we were hiring for but not in as senior as the role we had. This role would have been the perfect step to getting involved in more complex work for the person. Candidate #2 had less polished IT experience, ticked some of the boxes we were looking for and on paper in comparison to Candidate #1 was not as close a fit as Candidate #1 was. It seemed like I was comparing apples and oranges. After speaking to both candidates it turns out I was comparing apples and oranges except the person better suited for our role was not the one I was expecting it would be. The first candidate on paper looked great – they had the experience we were looking for and appeared to be just right for the role, but after talking to them, they gave me the impression that they thought the world owed them. The impression I was left with was that they did not equate success with hard work, they seemed more interested in “what is in it for me”. Rather than having a proper conversation with me, I was often cut off and asked to hurry it up when explaining our business, what we are doing, etc... . This person seemed more interested in the job title and money than how rather than think about ways to make the role successful. Candidate #2 who had limited experience, made up for any perceived lack of experience and them some with a demonstrated motivation to succeed and do the things needed to make that happen. Candidate #2 made a great first impression, they did not seem afraid of hard work and demonstrated a “team player” attitude. In talking to them they kept me engaged, listened and asked thoughtful questions that made me think this is the type of person who creates their own luck and who would thrive in a place like Oracle. Skills, capabilities, experience and a good resume can certainly get your foot in the door, but the wrong attitude or approach to work can close those opportunities just as easily. On the other hand, hard work, effort and a genuine work ethic may help open those doors that would otherwise closed for you. A resume with all the credentials gets you in the front door but that is just the beginning of the process. It is not how we start the race that is important, it’s how things end that matter most.

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  • IE9 and the Mystery of the Broken Video Tag

    - by David Wesst
    I was very excited when Microsoft released the Internet Explorer 9 Release Candidate. As far as I was concerned, this was another nail in the coffin for IE6 and step in the right direction for us .NET web developers as our base camp was finally starting to support the latest and greatest future-web standards. Unfortunately, my celebration was short lived as I soon hit a snag while loading up an HTML5 site I was building in Visual Studio 2010. The Mystery After updating Internet Explorer, I ran my HTML5 site that had the oh-so-lovely HTML5 video tag showing a video. Even though this worked in IE9 Beta, it appeared that IE9 RC could not load the same file. I figured that it was the video codec. Maybe IE9 RC no longer supported the video codec I used to encode my video. Here's the code I used: <video width="854" height="480" id="myOtherVideo" autoplay="" controls=""> <source src="/DemoSite1/Media/big_buck_bunny.mp4"/> <div> <p>Your browser does not support HTML5 Video.</p> </div> </video> As you can see from the code, I had the "fail-safe" code inside the video tag. The idea there being that if the video tag, or the video files themselves, are not supported by the browser my video should fail gracefully. What was even more strange was the fact that it worked in all the other HTML5 browsers that supported video. The Investigation Whoa! DJ stop the music. How can any of that make sense? Would the IE team really take such huge strides forward only to forget to include a feature that was already in the beta? I don't think so. I did plenty of searching on the web and asking around on the web, but could not seem to find anyone else having the same problem. Eventually I came across this post talking about declaring the MIME type in the .htaccess file. That got me thinking: does my web server support the video MIME type? I was using VS2010, so how do I know what kind of MIME types are supported by default? Still, my page hosted in Cassini (the web development server in VS2010) works on the other browsers. Why wouldn't it work with IE9 RC? To answer that, it was time to open up the upgraded toolbox known as the Developer's Tools in IE9 and use the new Network Tab. The Conclusion If you take a closer look at the results displayed from the Network tab, you can see that IE9 RC has interpreted the video file as text/html rather than video/mp4. To make this work, I decided to use IIS to debug my HTML5 web application by setting the web project's properties. Then, I added the MIME types that I want to support (i.e. video/mp4, video/ogg, video/webm). Et voila! The Mystery of the Broken Video Tag is solved. After Thoughts After solving the mystery, I still had the question about why my site worked in Chrome, Safari, and Firefox 3.6. After asking around, the best answer that I received was from my colleague Tyler Doerksen. He said that IE9 likely depends on the server telling it what kind of file it is downloading rather than trying to read the metadata about the data it is trying to download before doing anything. I have no facts to back this up, but it makes sense to me. In a browser war where milliseconds can make your browser fall back a few places in the race for supremacy, maybe the IE team opted to depend on the server knowing what kind of content it is serving up. Makes sense to me. In any case, that is just an educated guess. If you have any comments, feel free to post on them below. This post also appears at http://david.wes.st

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  • PASS Summit 2013 Review

    - by Ajarn Mark Caldwell
    As a long-standing member of PASS who lives in the greater Seattle area and has attended about nine of these Summits, let me start out by saying how GREAT it was to go to Charlotte, North Carolina this year.  Many of the new folks that I met at the Summit this year, upon hearing that I was from Seattle, commented that I must have been disappointed to have to travel to the Summit this year after 5 years in a row in Seattle.  Well, nothing could be further from the truth.  I cheered loudly when I first heard that the 2013 Summit would be outside Seattle.  I have many fond memories of trips to Orlando, Florida and Grapevine, Texas for past Summits (missed out on Denver, unfortunately).  And there is a funny dynamic that takes place when the conference is local.  If you do as I have done the last several years and saved my company money by not getting a hotel, but rather just commuting from home, then both family and coworkers tend to act like you’re just on a normal schedule.  For example, I have a young family, and my wife and kids really wanted to still see me come home “after work”, but there are a whole lot of after-hours activities, social events, and great food to be enjoyed at the Summit each year.  Even more so if you really capitalize on the opportunities to meet face-to-face with people you either met at previous summits or have spoken to or heard of, from Twitter, blogs, and forums.  Then there is also the lovely commuting in Seattle traffic from neighboring cities rather than the convenience of just walking across the street from your hotel.  So I’m just saying, there are really nice aspects of having the conference 2500 miles away. Beyond that, the training was fantastic as usual.  The SQL Server community has many outstanding presenters and experts with deep knowledge of the tools who are extremely willing to share all of that with anyone who wants to listen.  The opening video with PASS President Bill Graziano in a NASCAR race turned dream sequence was very well done, and the keynotes, as usual, were great.  This year I was particularly impressed with how well attended were the Professional Development sessions.  Not too many years ago, those were very sparsely attended, but this year, the two that I attended were standing-room only, and these were not tiny rooms.  I would say this is a testament to both the maturity of the attendees realizing how important these topics are to career success, as well as to the ever-increasing skills of the presenters and the program committee for selecting speakers and topics that resonated with people.  If, as is usually the case, you were not able to get to every session that you wanted to because there were just too darn many good ones, I encourage you to get the recordings. Overall, it was a great time as these events always are.  It was wonderful to see old friends and make new ones, and the people of Charlotte did an awesome job hosting the event and letting their hospitality shine (extra kudos to SQLSentry for all they did with the shuttle, maps, and other event sponsorships).  We’re back in Seattle next year (it is a release year, after all) but I would say that with the success of this year’s event, I strongly encourage the Board and PASS HQ to firmly reestablish the location rotation schedule.  I’ll even go so far as to suggest standardizing on an alternating Seattle – Charlotte schedule, or something like that. If you missed the Summit this year, start saving now, and register early, so you can join us!

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  • Efficiently separating Read/Compute/Write steps for concurrent processing of entities in Entity/Component systems

    - by TravisG
    Setup I have an entity-component architecture where Entities can have a set of attributes (which are pure data with no behavior) and there exist systems that run the entity logic which act on that data. Essentially, in somewhat pseudo-code: Entity { id; map<id_type, Attribute> attributes; } System { update(); vector<Entity> entities; } A system that just moves along all entities at a constant rate might be MovementSystem extends System { update() { for each entity in entities position = entity.attributes["position"]; position += vec3(1,1,1); } } Essentially, I'm trying to parallelise update() as efficiently as possible. This can be done by running entire systems in parallel, or by giving each update() of one system a couple of components so different threads can execute the update of the same system, but for a different subset of entities registered with that system. Problem In reality, these systems sometimes require that entities interact(/read/write data from/to) each other, sometimes within the same system (e.g. an AI system that reads state from other entities surrounding the current processed entity), but sometimes between different systems that depend on each other (i.e. a movement system that requires data from a system that processes user input). Now, when trying to parallelize the update phases of entity/component systems, the phases in which data (components/attributes) from Entities are read and used to compute something, and the phase where the modified data is written back to entities need to be separated in order to avoid data races. Otherwise the only way (not taking into account just "critical section"ing everything) to avoid them is to serialize parts of the update process that depend on other parts. This seems ugly. To me it would seem more elegant to be able to (ideally) have all processing running in parallel, where a system may read data from all entities as it wishes, but doesn't write modifications to that data back until some later point. The fact that this is even possible is based on the assumption that modification write-backs are usually very small in complexity, and don't require much performance, whereas computations are very expensive (relatively). So the overhead added by a delayed-write phase might be evened out by more efficient updating of entities (by having threads work more % of the time instead of waiting). A concrete example of this might be a system that updates physics. The system needs to both read and write a lot of data to and from entities. Optimally, there would be a system in place where all available threads update a subset of all entities registered with the physics system. In the case of the physics system this isn't trivially possible because of race conditions. So without a workaround, we would have to find other systems to run in parallel (which don't modify the same data as the physics system), other wise the remaining threads are waiting and wasting time. However, that has disadvantages Practically, the L3 cache is pretty much always better utilized when updating a large system with multiple threads, as opposed to multiple systems at once, which all act on different sets of data. Finding and assembling other systems to run in parallel can be extremely time consuming to design well enough to optimize performance. Sometimes, it might even not be possible at all because a system just depends on data that is touched by all other systems. Solution? In my thinking, a possible solution would be a system where reading/updating and writing of data is separated, so that in one expensive phase, systems only read data and compute what they need to compute, and then in a separate, performance-wise cheap, write phase, attributes of entities that needed to be modified are finally written back to the entities. The Question How might such a system be implemented to achieve optimal performance, as well as making programmer life easier? What are the implementation details of such a system and what might have to be changed in the existing EC-architecture to accommodate this solution?

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  • How can I best implement 'cache until further notice' with memcache in multiple tiers?

    - by ajreal
    the term "client" used here is not referring to client's browser, but client server Before cache workflow 1. client make a HTTP request --> 2. server process --> 3. store parsed results into memcache for next use (cache indefinitely) --> 4. return results to client --> 5. client get the result, store into client's local memcache with TTL After cache workflow 1. another client make a HTTP request --> 2. memcache found return memcache results to client --> 3. client get the result, store into client's local memcache with TTL TTL = time to live Is possible for me to know when the data was updated, and to expire relevant memcache(s) accordingly. However, the pitfalls on client site cache TTL Any data update before the TTL is not pick-up by client memcache. In reverse manner, where there is no update, client memcache still expire after the TTL First request (or concurrent requests) after cache TTL will get throttle as it need to repeat the "Before cache workflow" In the event where client require several HTTP requests on a single web page, it could be very bad in performance. Ideal solution should be client to cache indefinitely until further notice. Here are the three proposals about futher notice Proposal 1 : Make use on HTTP header (current implementation) 1. client sent HTTP request last modified time header 2. server check if last data modified time=last cache time return status 304 3. client based on header to decide further processing GOOD? ---- - save some parsing for client - lesser data transfer BAD? ---- - fire a HTTP request is still slow - server end still need to process lots of requests Proposal 2 : Consistently issue a HTTP request to check all data group last modified time 1. client fire a HTTP request 2. server to return last modified time for all data group 3. client compare local last cache time with the result 4. if data group last cache time < server last modified time then request again for that data group only GOOD? ---- - only fetch what is no up-to-date - less requests for server BAD? ---- - every web page require a HTTP request Proposal 3 : Tell client when new data is available (Push) 1. when server end notice there is a change on a data group 2. notify clients on the changes 3. help clients to fetch again data 4. then reset client local memcache after data is parsed GOOD? ---- - let the cache act/behave like a true cache BAD? ---- - encourage race condition My preference is on proposal 3, and something like Gearman could be ideal Where there is a change, Gearman server to sent the task to multiple clients (workers). Am I crazy? (I know my first question is a bit crazy)

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  • Obfuscation is not a panacea

    - by simonc
    So, you want to obfuscate your .NET application. My question to you is: Why? What are your aims when your obfuscate your application? To protect your IP & algorithms? Prevent crackers from breaking your licensing? Your boss says you need to? To give you a warm fuzzy feeling inside? Obfuscating code correctly can be tricky, it can break your app if applied incorrectly, it can cause problems down the line. Let me be clear - there are some very good reasons why you would want to obfuscate your .NET application. However, you shouldn't be obfuscating for the sake of obfuscating. Security through Obfuscation? Once your application has been installed on a user’s computer, you no longer control it. If they do not want to pay for your application, then nothing can stop them from cracking it, even if the time cost to them is much greater than the cost of actually paying for it. Some people will not pay for software, even if it takes them a month to crack a $30 app. And once it is cracked, there is nothing stopping them from putting the result up on the internet. There should be nothing suprising about this; there is no software protection available for general-purpose computers that cannot be cracked by a sufficiently determined attacker. Only by completely controlling the entire stack – software, hardware, and the internet connection, can you have even a chance to be uncrackable. And even then, someone somewhere will still have a go, and probably succeed. Even high-end cryptoprocessors have known vulnerabilities that can be exploited by someone with a scanning electron microscope and lots of free time. So, then, why use obfuscation? Well, the primary reason is to protect your IP. What obfuscation is very good at is hiding the overall structure of your program, so that it’s very hard to figure out what exactly the code is doing at any one time, what context it is running in, and how it fits in with the rest of the application; all of which you need to do to understand how the application operates. This is completely different to cracking an application, where you simply have to find a single toggle that determines whether the application is licensed or not, and flip it without the rest of the application noticing. However, again, there are limitations. An obfuscated application still has to run in the same way, and do the same thing, as the original unobfuscated application. This means that some of the protections applied to the obfuscated assembly have to be undone at runtime, else it would not run on the CLR and do the same thing. And, again, since we don’t control the environment the application is run on, there is nothing stopping a user from undoing those protections manually, and reversing some of the obfuscation. It’s a perpetual arms race, and it always will be. We have plenty of ideas lined about new protections, and the new protections added in SA 6.6 (method parent obfuscation and a new control flow obfuscation level) are specifically designed to be harder to reverse and reconstruct the original structure. So then, by all means, obfuscate your application if you want to protect the algorithms and what the application does. That’s what SmartAssembly is designed to do. But make sure you are clear what a .NET obfuscator can and cannot protect you against, and don’t expect your obfuscated application to be uncrackable. Someone, somewhere, will crack your application if they want to and they don’t have anything better to do with their time. The best we can do is dissuade the casual crackers and make it much more difficult for the serious ones. Cross posted from Simple Talk.

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  • cookieless sessions with ajax

    - by thezver
    ok, i know you get sick from this subject. me too :( I've been developing a quite "big application" with PHP & kohana framework past 2 years, somewhat-successfully using my framework's authentication mechanism. but within this time, and as the app grown, many concerning state-preservation issues arisen. main problems are that cookie-driven sessions: can't be used for web-service access ( at least it's really not nice to do so.. ) in many cases problematic with mobile access don't allow multiple simultaneous apps on same browser ( can be resolved by hard trickery, but still.. ) requires many configurations and mess to work 100% right, and that's without the --browser issues ( disabled cookies, old browsers bugs & vulnerabilities etc ) many other session flaws stated in this old thread : http://lists.nyphp.org/pipermail/talk/2006-December/020358.html After a really long research, and without any good library/on-hand-solution to feet my needs, i came up with a custom solution to majority of those problems . Basically, i'ts about emulating sessions with ajax calls, with additional security/performance measures: state preserved by interchanging SID(+hash) with client on ajax calls. state data saved in memcache(or equivalent), indexed by SID security achieved by: appending unpredictible hash to SID egenerating hash on each request & validating it validating fingerprint of client on each request ( referrer,os,browser etc) (*)condition: ajax calls are not simultaneous, to prevent race-condition with session token. (hopefully Ext-Direct solves that for me) From the first glance that supposed to be not-less-secure than equivalent cookie-driven implementation, and at the same time it's simple, maintainable, and resolves all the cookies flaws.. But i'm really concerned because i often hear the rule "don't try to implement custom security solutions". I will really appreciate any serious feedback about my method, and any alternatives. also, any tip about how to preserve state on page-refresh without cookies would be great :) but thats small technical prob. Sorry if i overlooked some similar post.. there are billions of them about sessions . Big thanks in advance ( and for reading until here ! ).

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  • How do I create a named temporary file on windows in Python?

    - by Chris B.
    I've got a Python program that needs to create a named temporary file which will be opened and closed a couple times over the course of the program, and should be deleted when the program exits. Unfortunately, none of the options in tempfile seem to work: TemporaryFile doesn't have a visible name NamedTemporaryFile creates a file-like object. I just need a filename. I've tried closing the object it returns (after setting delete = False) but I get stream errors when I try to open the file later. SpooledTemporaryFile doesn't have a visible name mkstemp returns both the open file object and the name; it doesn't guarantee the file is deleted when the program exits mktemp returns the filename, but doesn't guarantee the file is deleted when the program exits I've tried using mktemp1 within a context manager, like so: def get_temp_file(suffix): class TempFile(object): def __init__(self): self.name = tempfile.mktemp(suffix = '.test') def __enter__(self): return self def __exit__(self, ex_type, ex_value, ex_tb): if os.path.exists(self.name): try: os.remove(self.name) except: print sys.exc_info() return TempFile() ... but that gives me a WindowsError(32, 'The process cannot access the file because it is being used by another process'). The filename is used by a process my program spawns, and even though I ensure that process finishes before I exit, it seems to have a race condition out of my control. What's the best way of dealing with this? 1 I don't need to worry about security here; this is part of a testing module, so the most someone nefarious could do is cause our unit tests to spuriously fail. The horror!

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  • What is the scope of CONTEXT_INFO in SQL Server?

    - by JasonS
    I am using CONTEXT_INFO to pass a username to a delete trigger for the purposes of an audit/history table. I'm trying to understand the scope of CONTEXT_INFO and if I am creating a potential race condition. Each of my database tables has a stored proc to handle deletes. The delete stored proc takes userId as an parameter, and sets CONTEXT_INFO to the userId. My delete trigger then grabs the CONTEXT_INFO and uses that to update an audit table that indicates who deleted the row(s). The question is, if two deletes sprocs from different users are executing at the same time, can CONTEXT_INFO set in one of the sprocs be consumed by the trigger fired by the other sproc? I've seen this article http://msdn.microsoft.com/en-us/library/ms189252.aspx but I'm not clear on the scope of sessions and batches in SQL Server which is key to the article being helpful! I'd post code, but short on time at the moment. I'll edit later if this isn't clear enough. Thanks in advance for any help.

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  • Presenting UINavigationController modally -- problem setting up tool and nav bar items in root view controller viewDidLoad

    - by Bogatyr
    In my iOS app I'm creating and presenting a UINavigationController modally like so: MyViewController *myvc = [[[MyViewController alloc] initWithNibName:@"MyViewController" bundle:nil] autorelease]; UINavigationController *navVC = [[[UINavigationController alloc] initWithRootViewController:myvc] autorelease]; [self presentModalViewController:navVC animated:YES]; In the MyViewController viewDidLoad I'm creating and setting toolbar items for the navigation controller's toolbar, like so: self.navigationController.toolbar.items = [NSArray arrayWithObjects:(items...), nil]; the problem I'm having is that the items don't show up. If instead I call a method from MyViewController's viewDidLoad method that adds the toolbar items via performSelector:withObject:afterDelay:0, then it works perfectly. So there's obviously some race condition going on here with the initial presentation of the UINavigationController, initialization of its toolbar/navbar, and the initialization of the nav bar's specified initial root view controller. I verified in the debugger that the root view controller's viewDidLoad is called after the UINavigationController's viewDidLoad method. In fact, the root view controller's viewDidLoad method is not called until presentModalViewController: is called, and the UINavigationController's viewDidLoad is called within initWithRootViewController, so doesn't that imply that the UINavigationController object should be "all ready to go", including its nav bar and toolbars? I thought at first that the navigation controller's toolbar object may not exist yet at MyViewController's viewDidLoad time, but it clearly does. At least, NSLog shows that it is not nil during MyViewController's viewDidLoad method. In fact, the UINavigationController's toolbar object is identical at both times: in the root view controller's viewDidLoad, and in the "setupToolbar" method that I called with performSelector:withObject:afterDelay, so it's not getting "re-initialized" somehow. So, what's going on here? Why aren't my toolbar modifications "sticking" in MyViewController's viewDidLoad, and why does performing them in the next iteration of the runloop (performSelector:withObject:afterDelay:0) make it work? What is the "right" way of setting up initial navbar / toolbar items in code from the rootViewController of the UINavigationController?

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  • pthreads: reader/writer locks, upgrading read lock to write lock

    - by ScaryAardvark
    I'm using read/write locks on Linux and I've found that trying to upgrade a read locked object to a write lock deadlocks. i.e. // acquire the read lock in thread 1. pthread_rwlock_rdlock( &lock ); // make a decision to upgrade the lock in threads 1. pthread_rwlock_wrlock( &lock ); // this deadlocks as already hold read lock. I've read the man page and it's quite specific. The calling thread may deadlock if at the time the call is made it holds the read-write lock (whether a read or write lock). What is the best way to upgrade a read lock to a write lock in these circumstances.. I don't want to introduce a race on the variable I'm protecting. Presumably I can create another mutex to encompass the releasing of the read lock and the acquiring of the write lock but then I don't really see the use of read/write locks. I might as well simply use a normal mutex. Thx

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  • Windows-mobile app won't run after being closed by Task Manager

    - by pithyless
    I've inherited some windows-mobile code that I've been bringing up-to-date. I've come across a weird bug, and I was hoping that even though a bit vague, maybe it will spark someone's memory: Running the app (which is basically a glorified Forms app with P/Invoke gps code), I switch to the task manager, and close the app via End Task. Seems to exit fine (no errors and disappears from Task Manager). Unfortunately, the app refuses to start a second time until I reboot the phone or reinstall the CAB. What's worse: this bug is reproducible on a HTC Diamond, but works fine (ie. can run again after EndTask) on an HTC HD2. The only thing I can think of is some kind of timing race between a Dispose() and the Task Manager. Any ideas? I'm also thinking of a workaround - I do have a working "Exit Application" routine that correctly cleans up the app; can I catch the EndTask event in the c# code in order to complete a proper cleanup? Maybe I'm just missing the pain point... all ideas welcome :)

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  • .NET Process.Kill() in a safe way

    - by Orborde
    I'm controlling a creaky old FORTRAN simulator from a VB.NET GUI, using redirected I/O to communicate with the simulator executable. The GUI pops up a "status" window with a progress bar, estimated time, and a "STOP" button (Button_Stop). Now, I want the Button_Stop to terminate the simulator process immediately. The obvious way to do this is to call Kill() on the Child Process object. This gives an exception if it's done after the process has exited, but I can test whether the process is exited before trying to kill it, right? OK, so I do the following when the button is clicked: If Not Child.HasExited Then Child.Kill() Button_Stop.Enabled = False End If However, what if the process happens to exit between the test and the call to Kill()? In that case, I get an exception. The next thing to occur to me was that I can do Button_Stop.Enabled = False in the Process.Exited event handler, and thus prevent the Child.Kill() call in the Button_Stop.Clicked handler. But since the Process.Exited handler is called on a different thread, that still leaves the following possible interleaving: Child process exits. Process.Exited fires, calls Invoke to schedule the Button_Stop.Enabled = False User clicks on Button_Stop, triggering Child.Kill() Button_Stop.Enabled = False actually happens. An exception would then be thrown on step 3. How do I kill the process without any race conditions? Am I thinking about this entirely wrong?

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  • Ajax call to parent window after form submission

    - by David
    Hi all, Pardon the complicated title. Here's my situation: I'm working on a Grails app, and using jQuery for some of the more complex UI stuff. The way the system is set up, I have an item, which can have various files (user-supplied) associated with it. On my Item/show view, there is a link to add a file. This link pops up a jQuery modal dialog, which displays my file upload form (a remote .gsp). So, the user selects the file and enters a comment, and when the form is submitted, the dialog gets closed, and the list of files on the Item/show view is refreshed. I was initially accomplishing this by adding onclick="javascript:window.parent.$('#myDialog').dialog('close');" to my submit button. This worked fine, but when submitting some larger files, I end up with a race condition where the dialog closes and the file list is refreshed before the new file is saved, and so the list of files is out of date (the file still gets saved properly). So my question is, what is the best way to ensure that the dialog is not closed until after the form submit operation completes? I've tried using the <g:formRemote tag in Grails, and closing the dialog in the "after" attribute (according to the Grails docs, the script is called after form submission), but I receive an error (taken from FireBug) stating that window.parent.$('#myDialog').dialog is not a function Is this a simple JavaScript/Grails syntax issue that I'm missing here, or am I going about this entirely wrong? Thanks so much for your time and assistance!

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  • Automatically stashing

    - by Readonly
    The section Last links in the chain: Stashing and the reflog in http://ftp.newartisans.com/pub/git.from.bottom.up.pdf recommends stashing often to take snapshots of your work in progress. The author goes as far as recommending that you can use a cron job to stash your work regularly, without having to do a stash manually. The beauty of stash is that it lets you apply unobtrusive version control to your working process itself: namely, the various stages of your working tree from day to day. You can even use stash on a regular basis if you like, with something like the following snapshot script: $ cat <<EOF > /usr/local/bin/git-snapshot #!/bin/sh git stash && git stash apply EOF $ chmod +x $_ $ git snapshot There’s no reason you couldn’t run this from a cron job every hour, along with running the reflog expire command every week or month. The problem with this approach is: If there are no changes to your working copy, the "git stash apply" will cause your last stash to be applied over your working copy. There could be race conditions between when the cron job executes and the user working on the working copy. For example, "git stash" runs, then the user opens the file, then the script's "git stash apply" is executed. Does anybody have suggestions for making this automatic stashing work more reliably?

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  • How to make Stack.Pop threadsafe

    - by user260197
    I am using the BlockingQueue code posted in this question, but realized I needed to use a Stack instead of a Queue given how my program runs. I converted it to use a Stack and renamed the class as needed. For performance I removed locking in Push, since my producer code is single threaded. My problem is how can thread working on the (now) thread safe Stack know when it is empty. Even if I add another thread safe wrapper around Count that locks on the underlying collection like Push and Pop do, I still run into the race condition that access Count and then Pop are not atomic. Possible solutions as I see them (which is preferred and am I missing any that would work better?): Consumer threads catch the InvalidOperationException thrown by Pop(). Pop() return a nullptr when _stack-Count == 0, however C++-CLI does not have the default() operator ala C#. Pop() returns a boolean and uses an output parameter to return the popped element. Here is the code I am using right now: generic <typename T> public ref class ThreadSafeStack { public: ThreadSafeStack() { _stack = gcnew Collections::Generic::Stack<T>(); } public: void Push(T element) { _stack->Push(element); } T Pop(void) { System::Threading::Monitor::Enter(_stack); try { return _stack->Pop(); } finally { System::Threading::Monitor::Exit(_stack); } } public: property int Count { int get(void) { System::Threading::Monitor::Enter(_stack); try { return _stack->Count; } finally { System::Threading::Monitor::Exit(_stack); } } } private: Collections::Generic::Stack<T> ^_stack; };

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  • Debugging strategy to find the cause of bad_alloc

    - by SalamiArmi
    I have a fairly serious bug in my program - occasional calls to new() throw a bad_alloc. From the documentation I can find on bad_alloc, it seems to be thrown for these reasons: When the computer runs out of memory (which definitely isn't happening, I have 4GB of RAM, program throws bad_alloc when using less than 5MB (checked in taskmanager) with nothing serious running in the background). If the memory becomes too fragmented to allocate new blocks (which, again, is unlikely - the largest sized block I ever allocate would be about 1KB, and that doesn't get done more than 100 times before the crash occurs). Based on these descriptions, I don't really have anywhere in which a bad_alloc could be thrown. However, the application I am running runs more than one thread, which could possibly be contributing to the problem. By testing all of the objects on a single thread, everything seems to be working smoothly. The only other thing that I can think of that is going on here could be some kind of race-condition caused by calling new() in more than one place at the same time, but I've tried adding mutexes to prevent that behaviour to no effect. Because the program is several hundred lines and I have no idea where the problem actually lies, I'm not sure of what, if any, code snippets to post. Instead, I was wondering if there were any tools that will help me test for this kind of thing, or if there are any general strategies that can help me with this problem. I'm using Microsoft Visual Studio 2008, with Poco for threading.

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  • calling asp.net mvc action method using jquery post method expires the session

    - by nccsbim071
    hi, i have a website where i provicde a link. On clicking the link a controller action method is called to generate a zip file after creation of zip file is done, i show the link to download the zip file by replacing the link to create a zip with the link to download the zip. the problem is that after zip file creation is over and link is shown, when user clicks on the link to download the zip file, they are sent to login. After providing correct credentials in the login page they are prompted to download the zip file. they sould not be sent to the login page. In the action to generate zip file i haven't abondoned the session or haven't not done anything that abondons the session. the user should not be sen't to login page after successful creation of zip file user should be able to download the file without login. i search internet on this problem, but i did not find any solution. In one of the blog written by hanselman i found this statement that creates the problem with the session: Is some other thing like an Ajax call or IE's Content Advisor simultaneously hitting the default page or login page and causing a race condition that calls Session.Abandon? (It's happened before!) so i thought there might be some problem with ajax call that causes the session to expire, but i don't know what is happening? any help please thanks

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  • How to implement Session timeout in Web Server Side?

    - by Morgan Cheng
    I beheld a web framework implementing in-memory session in this way. The session object is added to Cache with timeout. When the time is out, the session is removed from Cache automatically. To protect race condition, each request should acquire lock on given session object to proceed. Each request will "touch" the session in Cache to refresh the timeout. Everything looks fine, until this scenario is discovered. Say, one operation takes a long time, longer than timeout. Another request comes and wait on session lock which is currently hold by the long-time request. Finally, the long-time request is over, it releases the lock. But, since it already takes longer time than timeout, the session object is already removed from Cache. This is obvious because the only request holding the lock doesn't have a chance to "touch" the session object in cache. The second request gets the lock but cannot retrieve the expired Session object. Oops... To fix this issue, the second request has to re-create the Session object. But, this is just like digging a buried dead body from tomb and try to bring it back to life. It causes buggy code. I'm wondering what's the best way to implement timeout in session to handle such scenario. I know that current platform must have good session mechanism. I just want to know the under-the-hood how.

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  • Get directory path by fd

    - by tylerl
    I've run into the need to be able refer to a directory by path given its file descriptor in Linux. The path doesn't have to be canonical, it just has to be functional so that I can pass it to other functions. So, taking the same parameters as passed to a function like fstatat(), I need to be able to call a function like getxattr() which doesn't have a f-XYZ-at() variant. So far I've come up with these solutions; though none are particularly elegant. The simplest solution is to avoid the problem by calling openat() and then using a function like fgetxattr(). This works, but not in every situation. So another method is needed to fill the gaps. The next solution involves looking up the information in proc: if (!access("/proc/self/fd",X_OK)) { sprintf(path,"/proc/self/fd/%i/",fd); } This, of course, totally breaks on systems without proc, including some chroot environments. The last option, a more portable but potentially-race-condition-prone solution, looks like this: DIR* save = opendir("."); fchdir(fd); getcwd(path,PATH_MAX); fchdir(dirfd(save)); closedir(save); The obvious problem here is that in a multithreaded app, changing the working directory around could have side effects. However, the fact that it works is compelling: if I can get the path of a directory by calling fchdir() followed by getcwd(), why shouldn't I be able to just get the information directly: fgetcwd() or something. Clearly the kernel is tracking the necessary information. So how do I get to it?

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  • Dropping all user tables/sequences in Oracle

    - by Ambience
    As part of our build process and evolving database, I'm trying to create a script which will remove all of the tables and sequences for a user. I don't want to do recreate the user as this will require more permissions than allowed. My script creates a procedure to drop the tables/sequences, executes the procedure, and then drops the procedure. I'm executing the file from sqlplus: drop.sql: create or replace procedure drop_all_cdi_tables is cur integer; begin cur:= dbms_sql.OPEN_CURSOR(); for t in (select table_name from user_tables) loop execute immediate 'drop table ' ||t.table_name|| ' cascade constraints'; end loop; dbms_sql.close_cursor(cur); cur:= dbms_sql.OPEN_CURSOR(); for t in (select sequence_name from user_sequences) loop execute immediate 'drop sequence ' ||t.sequence_name; end loop; dbms_sql.close_cursor(cur); end; / execute drop_all_cdi_tables; / drop procedure drop_all_cdi_tables; / Unfortunately, dropping the procedure causes a problem. There seems to cause a race condition and the procedure is dropped before it executes. E.g.: SQL*Plus: Release 11.1.0.7.0 - Production on Tue Mar 30 18:45:42 2010 Copyright (c) 1982, 2008, Oracle. All rights reserved. Connected to: Oracle Database 11g Enterprise Edition Release 11.1.0.7.0 - 64bit Production With the Partitioning, OLAP, Data Mining and Real Application Testing options Procedure created. PL/SQL procedure successfully completed. Procedure created. Procedure dropped. drop procedure drop_all_user_tables * ERROR at line 1: ORA-04043: object DROP_ALL_USER_TABLES does not exist SQL Disconnected from Oracle Database 11g Enterprise Edition Release 11.1.0.7.0 - 64 With the Partitioning, OLAP, Data Mining and Real Application Testing options Any ideas on how to get this working?

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  • What programming hack from your past are you most ashamed of?

    - by LeopardSkinPillBoxHat
    We've all been there (usually when we are young and inexperienced). Fixing it properly is too difficult, too risky or too time-consuming. So you go down the hack path. Which hack from your past are you most ashamed of, and why? I'm talking about the ones where you would be really embarrassed if someone could attribute the hack to you (quite easily if you are using revision control software). One hack per answer please. Mine was shortly after I started in my first job. I was working on a legacy C system, and there was this strange defect where a screen view failed to update properly under certain circumstances. I wasn't familiar with how to use the debugger at this time, so I added traces into the code to figure out what was going on. Then I realised that the defect didn't occur anymore with the traces in the code. I slowly backed out the traces one-by-one, until I realised that only a single trace was required to make the problem go away. My logic now would tell me that I was dealing with some sort of race-condition or timing related issue that the trace just "hid under the rug". But I checked in the code with the following line, and all was well: printf(""); Which hacks are you ashamed of?

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  • WPF, C# - Making Intellisense/Autocomplete list, fastest way to filter list of strings

    - by user559548
    Hello everyone, I'm writing an Intellisense/Autocomplete like the one you find in Visual Studio. It's all fine up until when the list contains probably 2000+ items. I'm using a simple LINQ statement for doing the filtering: var filterCollection = from s in listCollection where s.FilterValue.IndexOf(currentWord, StringComparison.OrdinalIgnoreCase) >= 0 orderby s.FilterValue select s; I then assign this collection to a WPF Listbox's ItemSource, and that's the end of it, works fine. Noting that, the Listbox is also virtualised as well, so there will only be at most 7-8 visual elements in memory and in the visual tree. However the caveat right now is that, when the user types extremely fast in the richtextbox, and on every key up I execute the filtering + binding, there's this semi-race condition, or out of sync filtering, like the first key stroke's filtering could still be doing it's filtering or binding work, while the fourth key stroke is also doing the same. I know I could put in a delay before applying the filter, but I'm trying to achieve a seamless filtering much like the one in Visual Studio. I'm not sure where my problem exactly lies, so I'm also attributing it to IndexOf's string operation, or perhaps my list of string's could be optimised in some kind of index, that could speed up searching. Any suggestions of code samples are much welcomed. Thanks.

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  • Microsoft Detours - DetourUpdateThread?

    - by pault543
    Hi, I have a few quick questions about the Microsoft Detours Library. I have used it before (successfully), but I just had a thought about this function: LONG DetourUpdateThread(HANDLE hThread); I read elsewhere that this function will actually suspend the thread until the transaction completes. This seems odd since most sample code calls: DetourUpdateThread(GetCurrentThread()); Anyway, apparently this function "enlists" threads so that, when the transaction commits (and the detours are made), their instruction pointers are modified if they lie "within the rewritten code in either the target function or the trampoline function." My questions are: When the transaction commits, is the current thread's instruction pointer going to be within the DetourTransactionCommit function? If so, why should we bother enlisting it to be updated? Also, if the enlisted threads are suspended, how can the current thread continue executing (given that most sample code calls DetourUpdateThread(GetCurrentThread());)? Finally, could you suspend all threads for the current process, avoiding race conditions (considering that threads could be getting created and destroyed at any time)? Perhaps this is done when the transaction begins? This would allow us to enumerate threads more safely (as it seems less likely that new threads could be created), although what about CreateRemoteThread()? Thanks, Paul For reference, here is an extract from the simple sample: // DllMain function attaches and detaches the TimedSleep detour to the // Sleep target function. The Sleep target function is referred to // through the TrueSleep target pointer. BOOL WINAPI DllMain(HINSTANCE hinst, DWORD dwReason, LPVOID reserved) { if (dwReason == DLL_PROCESS_ATTACH) { DetourTransactionBegin(); DetourUpdateThread(GetCurrentThread()); DetourAttach(&(PVOID&)TrueSleep, TimedSleep); DetourTransactionCommit(); } else if (dwReason == DLL_PROCESS_DETACH) { DetourTransactionBegin(); DetourUpdateThread(GetCurrentThread()); DetourDetach(&(PVOID&)TrueSleep, TimedSleep); DetourTransactionCommit(); } return TRUE; }

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  • Obj-C: ++variable is increasing by two instead of one

    - by Eli Garfinkel
    I am writing a program that asks users yes/no questions to help them decide how to vote in an election. I have a variable representing the question number called questionnumber. Each time I go through the switch-break loop, I add 1 to the questionnumber variable so that the next question will be displayed. This works fine for the first two questions. But then it skips the third question and moves on to the fourth. When I have more questions in the list, it skips every other question. Somewhere, for some reasons, the questionnumber variable is increasing when I don't want it to. Please look at the code below and tell me what I'm doing wrong. Thank you! Eli import "MainView.h" import @implementation MainView @synthesize Question; @synthesize mispar; int conservative = 0; int liberal = 0; int questionnumber = 1; (IBAction)agreebutton:(id)sender { ++liberal; } (IBAction)disagreebutton:(id)sender { ++conservative; } (IBAction)nextbutton:(id)sender { ++questionnumber; switch (questionnumber) { case 2: Question.text = @"Congress should pass a law that would ban Americans from earning more than one hundred million dollars in any given year."; break; case 3: Question.text = @"It is not fair to admit people to a university or employ them on the basis of merit alone. Factors such as race, gender, class, and sexual orientation must also be considered."; break; case 4: Question.text = @"There are two Americas - one for the rich and one for the poor."; break; case 5: Question.text = @"Top quality health care should be free for all."; break; default: break; } } @end

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