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  • dev and prod systems in rails

    - by poseid
    What exactly is the difference in rails between dev and prod environments. When I develop an application in dev mode, do I have peformance problems, or others if I clone my dev environment on prod?

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  • Dealing with external processes

    - by Jesse Aldridge
    I've been working on a gui app that needs to manage external processes. Working with external processes leads to a lot of issues that can make a programmer's life difficult. I feel like maintenence on this app is taking an unacceptably long time. I've been trying to list the things that make working with external processes difficult so that I can come up with ways of mitigating the pain. This kind of turned into a rant which I thought I'd post here in order to get some feedback and to provide some guidance to anybody thinking about sailing into these very murky waters. Here's what I've got so far: Output from the child can get mixed up with output from the parent. This can make both outputs misleading and hard to read. It can be hard to tell what came from where. It becomes harder to figure out what's going on when things are asynchronous. Here's a contrived example: import textwrap, os, time from subprocess import Popen test_path = 'test_file.py' with open(test_path, 'w') as file: file.write(textwrap.dedent(''' import time for i in range(3): print 'Hello %i' % i time.sleep(1)''')) proc = Popen('python -B "%s"' % test_path) for i in range(3): print 'Hello %i' % i time.sleep(1) os.remove(test_path) I guess I could have the child process write its output to a file. But it can be annoying to have to open up a file every time I want to see the result of a print statement. If I have code for the child process I could add a label, something like print 'child: Hello %i', but it can be annoying to do that for every print. And it adds some noise to the output. And of course I can't do it if I don't have access to the code. I could manually manage the process output. But then you open up a huge can of worms with threads and polling and stuff like that. A simple solution is to treat processes like synchronous functions, that is, no further code executes until the process completes. In other words, make the process block. But that doesn't work if you're building a gui app. Which brings me to the next problem... Blocking processes cause the gui to become unresponsive. import textwrap, sys, os from subprocess import Popen from PyQt4.QtGui import * from PyQt4.QtCore import * test_path = 'test_file.py' with open(test_path, 'w') as file: file.write(textwrap.dedent(''' import time for i in range(3): print 'Hello %i' % i time.sleep(1)''')) app = QApplication(sys.argv) button = QPushButton('Launch process') def launch_proc(): # Can't move the window until process completes proc = Popen('python -B "%s"' % test_path) proc.communicate() button.connect(button, SIGNAL('clicked()'), launch_proc) button.show() app.exec_() os.remove(test_path) Qt provides a process wrapper of its own called QProcess which can help with this. You can connect functions to signals to capture output relatively easily. This is what I'm currently using. But I'm finding that all these signals behave suspiciously like goto statements and can lead to spaghetti code. I think I want to get sort-of blocking behavior by having the 'finished' signal from QProcess call a function containing all the code that comes after the process call. I think that should work but I'm still a bit fuzzy on the details... Stack traces get interrupted when you go from the child process back to the parent process. If a normal function screws up, you get a nice complete stack trace with filenames and line numbers. If a subprocess screws up, you'll be lucky if you get any output at all. You end up having to do a lot more detective work everytime something goes wrong. Speaking of which, output has a way of disappearing when dealing external processes. Like if you run something via the windows 'cmd' command, the console will pop up, execute the code, and then disappear before you have a chance to see the output. You have to pass the /k flag to make it stick around. Similar issues seem to crop up all the time. I suppose both problems 3 and 4 have the same root cause: no exception handling. Exception handling is meant to be used with functions, it doesn't work with processes. Maybe there's some way to get something like exception handling for processes? I guess that's what stderr is for? But dealing with two different streams can be annoying in itself. Maybe I should look into this more... Processes can hang and stick around in the background without you realizing it. So you end up yelling at your computer cuz it's going so slow until you finally bring up your task manager and see 30 instances of the same process hanging out in the background. Also, hanging background processes can interefere with other instances of the process in various fun ways, such as causing permissions errors by holding a handle to a file or someting like that. It seems like an easy solution to this would be to have the parent process kill the child process on exit if the child process didn't close itself. But if the parent process crashes, cleanup code might not get called and the child can be left hanging. Also, if the parent waits for the child to complete, and the child is in an infinite loop or something, you can end up with two hanging processes. This problem can tie in to problem 2 for extra fun, causing your gui to stop responding entirely and force you to kill everything with the task manager. F***ing quotes Parameters often need to be passed to processes. This is a headache in itself. Especially if you're dealing with file paths. Say... 'C:/My Documents/whatever/'. If you don't have quotes, the string will often be split at the space and interpreted as two arguments. If you need nested quotes you can use ' and ". But if you need to use more than two layers of quotes, you have to do some nasty escaping, for example: "cmd /k 'python \'path 1\' \'path 2\''". A good solution to this problem is passing parameters as a list rather than as a single string. Subprocess allows you to do this. Can't easily return data from a subprocess. You can use stdout of course. But what if you want to throw a print in there for debugging purposes? That's gonna screw up the parent if it's expecting output formatted a certain way. In functions you can print one string and return another and everything works just fine. Obscure command-line flags and a crappy terminal based help system. These are problems I often run into when using os level apps. Like the /k flag I mentioned, for holding a cmd window open, who's idea was that? Unix apps don't tend to be much friendlier in this regard. Hopefully you can use google or StackOverflow to find the answer you need. But if not, you've got a lot of boring reading and frusterating trial and error to do. External factors. This one's kind of fuzzy. But when you leave the relatively sheltered harbor of your own scripts to deal with external processes you find yourself having to deal with the "outside world" to a much greater extent. And that's a scary place. All sorts of things can go wrong. Just to give a random example: the cwd in which a process is run can modify it's behavior. There are probably other issues, but those are the ones I've written down so far. Any other snags you'd like to add? Any suggestions for dealing with these problems?

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  • Working through exercises in "Cocoa Programming for Mac OS X" - I'm stumped

    - by Zigrivers
    I've been working through the exercises in a book recommended here on stackoverflow, however I've run into a problem and after three days of banging my head on the wall, I think I need some help. I'm working through the "Speakline" exercise where we add a TableView to the interface and the table will display the "voices" that you can choose for the text to speech aspect of the program. I am having two problems that I can't seem to get to the bottom of: I get the following error: * Illegal NSTableView data source (). Must implement numberOfRowsInTableView: and tableView:objectValueForTableColumn:row: The tableView that is supposed to display the voices comes up blank I have a feeling that both of these problems are related. I'm including my interface code here: #import <Cocoa/Cocoa.h> @interface AppController : NSObject <NSSpeechSynthesizerDelegate, NSTableViewDelegate> { IBOutlet NSTextField *textField; NSSpeechSynthesizer *speechSynth; IBOutlet NSButton *stopButton; IBOutlet NSButton *startButton; IBOutlet NSTableView *tableView; NSArray *voiceList; } - (IBAction)sayIt:(id)sender; - (IBAction)stopIt:(id)sender; @end And my implementation code here: #import "AppController.h" @implementation AppController - (id)init { [super init]; //Log to help me understand what is happening NSLog(@"init"); speechSynth = [[NSSpeechSynthesizer alloc] initWithVoice:nil]; [speechSynth setDelegate:self]; voiceList = [[NSSpeechSynthesizer availableVoices] retain]; return self; } - (IBAction)sayIt:(id)sender { NSString *string = [[textField stringValue] stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]]; //Is the string zero-length? if([string length] == 0) { NSLog(@"String from %@ is a string with a length of %d.", textField, [string length]); [speechSynth startSpeakingString:@"Please enter a phrase first."]; } [speechSynth startSpeakingString:string]; NSLog(@"Started to say: %@", string); [stopButton setEnabled:YES]; [startButton setEnabled:NO]; } - (IBAction)stopIt:(id)sender { NSLog(@"Stopping..."); [speechSynth stopSpeaking]; } - (void) speechSynthesizer:(NSSpeechSynthesizer *)sender didFinishSpeaking:(BOOL)complete { NSLog(@"Complete = %d", complete); [stopButton setEnabled:NO]; [startButton setEnabled:YES]; } - (NSInteger)numberOfRowsInTableView:(NSTableView *)aTableView { return [voiceList count]; } - (id)tableView: (NSTableView *)tv objecValueForTableColumn: (NSTableColumn *)tableColumn row:(NSInteger)row { NSString *v = [voiceList objectAtIndex:row]; NSLog(@"v = %@",v); NSDictionary *dict = [NSSpeechSynthesizer attributesForVoice:v]; return [dict objectForKey:NSVoiceName]; } /* - (BOOL)respondsToSelector:(SEL)aSelector { NSString *methodName = NSStringFromSelector(aSelector); NSLog(@"respondsToSelector: %@", methodName); return [super respondsToSelector:aSelector]; } */ @end Hopefully, you guys can see something obvious that I've missed. Thank you!

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  • Formatting in a UITextView

    - by richard Stephenson
    hi all , im having problems with formatting for a UITextView. my app pulls in XML, saves some of it to a string , and then displays the text in a UITextView. it understands if you put a return in there, and it starts a new line. but i want to put paragraphs in there, any idea how i can pass that information without doing multiple UITextViews Thanks :)

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  • IIS7 - 401.3 Error

    - by Echilon
    I'm trying to get a site working on IIS7 with classic ASP and having problems. I've created a directory and added both Network Service and IIS_IUSRS with full control. I've also changed the anonymous authentication to the application pool identity, but still no joy. I really have no idea what to try next.

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  • Why might the Large Object Heap grow rather than throw an exception?

    - by Unsliced
    In a previous question I asked possible programatic ways of maximising the largest block allocatable on the LOH. I'm still seeing the problems, but now I'm trying to get my head around why the LOH seems to grow and shrink in size, yet I'm still seeing OutOfMemoryExceptions that tally with what others have reported as being due to LOH fragmentation. Why might one call to, for example, StringBuilder.EnsureCapacity throw an OutOfMemoryException for me, but another call from somewhere else result in the LOH expanding in size (according to the performance counters, it is growing and shrinking)?

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  • Creating a Cerificate for Bouncy Castle Encryption

    - by Gordon
    I am trying to create a self-signed certificate to use for encrypting an email using bouncycaste. What would be the best way to generate a certificate? I have tried using openssl but I have had problems with certificate. Here is the code I am using to encrypt, I am using 3des. SMIMEEnvelopedGenerator gen = new SMIMEEnvelopedGenerator(); gen.addKeyTransRecipient(x509Cert); // adds an X509Certificate MimeBodyPart encData = gen.generate(mimeBodyPart, SMIMEEnvelopedGenerator.DES_EDE3_CBC, "BC");

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  • Why is TransactionScope using a distributed transaction when I am only using LinqToSql and Ado.Net

    - by Ian Ringrose
    We are having problems on one machine, with the error message: "MSDTC on server XXX is unavailable." The code is using a TransactionScope to wrap some LingToSql database code; there is also some raw Ado.net inside of the transaction. As only a single sql database (2005) is being accessed, why is a distributed transaction being used at all? (I don’t wish to know how to enable MSDTC, as the code needs to work on the server with their current setup)

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  • Problem with jquery-droppable in Chrome

    - by ripper234
    I have a simple application that users jquery-ui's draggable and droppable. In Firefox, it works perfectly. In Chrome, however, I'm having problems. This is the code: $(".cell").droppable({ drop: function(event, ui) { var originalTarget = event.originalTarget; ... } }); In Chrome the 'event' object is of type 'Object' (using Chrome Dev Kit), and event.originalTarget is 'undefined'. What am I doing wrong?

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  • Finding key Solr performance metrics

    - by Mike Malloy
    To improve performance of Solr find your slowest searches, monitor query results, cache hit rate and cache size, document cache and filter cache; find problems with Solr update handlers by tracking index operations and document operations. There is a tool from New Relic which may help. http://www.newrelic.com/solr.html

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  • How to resume CUPS printer from command line

    - by stach81
    Hello I have printer in CUPS that due driver problems (hp 1010) form time to time goes into pause. I would like to write a shell script that will be once per hour resuming printer in cups. But I have no idea after googling for couple of minutes how to resume printer from shell command line. Regards Stan

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  • Ideas for student parallel programming project

    - by chi42
    I'm looking to do a parallel programming project in C (probably using pthreads or maybe OpenMP) for a class. It will done by a group of about four students, and should take about 4 weeks. I was thinking it would be interesting to attack some NP-complete problem with a more complex algorithm like a genetic algo with simulated annealing, but I'm not sure if it would be a big enough project. Anyone knew of any cool problems that could benefit from a parallel approach?

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  • Creating UI problem

    - by Xaver
    I create program which have the installer-like interface. How better realize that with ShowDialog method of Form-class or doing MDI interface? when i using ShowDialog method i doing this ways and i have next problems: 1) First form have ShowInTaskbar property=true other form false, formm appeared by .ShowDialog() method in event of press button "Next", event of pressing "" (also this function do .visible=false to undisplay form), event of pressing "

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  • What movie website allows people to scrape it?

    - by Sergio Tapia
    I've wanted to make a C# library to scrape movie information and return it to the application, but someone told me that it's against the TOS. RottenTomatoes seems to have no problems with it from what I've read on their licensing page, but I'm not quite sure. Where could I aquire movie information legally and without cost? It's for an open source application hosted here: LINK

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  • h2 in-memory tables, remote connection

    - by Carolyn
    I am having problems with creating an in memory table, using H2 database, and accessing it outside of the JVM it is created and running in. The documentation structures the url as "jdbc:h2:tcp:///mem:' I've tried many combinations, but simply cannot get the remote connection to work. Is this feature working, can anyone give me the details of how they used this.

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  • How do I correct "Commit Failed. File xxx is out of date. xxx path not found."

    - by Ryan Taylor
    I have recently run into a particularly sticky issue regarding committing the result of a merge in subversion. Our Subversion server is @ 1.5.0 and my TortoiseSVN client is now @ 1.6.1. I am trying to merge a feature branch back into my trunk. The merge appears to work okay; however, the commit fails with the following error message. Commit failed (details follow): File 'flex/src/com/penbay/invision/portal/services/http/soap/ReportServices/GetAllBldgsParamsByRegionBySiteResultEvent.as' is out of date '/svn/ibis/!svn/wrk/531d459d-80fa-ea46-bfb4-940d79ee6d2e/visualization/trunk/source/flex/src/com/penbay/invision/portal/services/http/soap/ReportServices/GetAllBldgsParamsByRegionBySiteResultEvent.as' path not found You have to update your working copy first. My working trunk is up to date. I have even checked out a new one into a different folder to make sure there wasn't any local cruft messing with the merge. I have done some more research into this and I think part of the problem is user error. I think our problems are: We had some developers committing work with a subversion client before 1.5 and some after. I believe this has the potential to corrupt the merge info. In other branches we have performed partial merges. That is, we did not always perform merges at the root of the branch. This was to facilitate updating Flex and .NET efforts within the same branch. We performed cyclic (reflexive) merges on our branch. This was done because we had multiple parallel branches and we wanted to periodically update our branch with the latest code in trunk. All of these things are explicitly not recommended by the Subversion book/team. We have learned our lesson and now know the best practices. However, we first need to merge and commit our latest branch. What it the best way to correct the problems we are encountering? Would deleting all the merge info in the trunk and branch be a viable solution? No. I have done this but it does not resolve the error that I am getting above.

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  • Run Application Command to open Terminal

    - by Narcolapser
    Question: What command do you type in to the "Run Application" box on ubuntu to open the terminal? Info: I'm having horrible horrible driver issues on my netbook. I might be able to solve some of these problems if I could just get to Terminal, but all I have is my keyboard, no mouse, so i need to know what command to type in to run application (Which I can get to with alt-f2) to open terminal. Thanks, ~N

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  • Modifying jQuery ajax request Connectino header

    - by Pat
    I'm trying to modify the Connection header with the following code with no success jQuery.ajax ( { url: URL, async: boolVariable, beforeSend: function(xhr) { xhr.setRequestHeader("Connection", "close"); } } ) The request headers via Firebug show: Connection keep-alive X-Requested-With XMLHttpRequest Any odd bugs/problems with setting this particular header known? Or is there something I'm doing wrong?

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  • Simulated Annealing Applications

    - by Andrei Vajna II
    Do you know any real applications for Simulated Annealing? Simulated Annealing is a heuristic algorithm used for problems like the traveling salesman or the knapsack problem. And yes, this is homework. I have to write a paper on this, and I thought this would be the best starting point. Perhaps someone actually works on a project that relies on Simulated Annealing.

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  • Enterprise Architect Communication Diagrams question

    - by devoured elysium
    I want to achieve something like this in Enterprise Architect's Communication Diagrams: start() ---------------- 1. create() ------------ ------------> | RGController | ---------------> | U : User | ---------------- ------------ But I am facing 2 problems: a) it seems I have to always make a connection between 2 objects (I can't have the start() message just come out of nowhere, like I'd want). b) I can't control the numbering as I'd want. Is there any way I could just set the numbering by myself?

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  • Security for ASP.NET Diagnostics page

    - by Moe Sisko
    I'm thinking of creating a diagnostics page for an ASP.NET app, which would be mostly intended for admin use to get more information about the application for diagnosing problems. Examples of the info the page might have : System.Environment.MachineName (might be useful in web farm scenarios) System.Environment.Version Environment.UserName database name current user's session ID Some of the info on this page might be sensitive from a security perspective. If you've done this sort of page before, what sort of security did you put on access to this page ? .

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  • Weird bug in header in IE7

    - by Luuk
    Hi all, I have a weird bug in IE7. http://www.luukratief-design.nl/dump/simplefolio/ the navigation has to be centered. same goes for the background. Now every browser does it perfectly. even IE6! (didnt do pngfix yet). The only one who is having problems is IE7 who shifts the whole navbar element to the right. Anyone knows how this is possible?

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