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• sendmail and MX records when mail server is not on web host

  - by Jim Nelson

  This is a problem I'm sure is easy to fix, but I've been banging my head on it all day. I'm developing a new web site for a client. The web site resides at (this is an example) website.com. I have a PHP form script to email visitors' requests to [email protected]. When I coded this on a staging server on a different domain, all worked fine. When I moved it to website.com, the mail messages never arrived. The web server is on a virtual host with a major ISP. Here's what I've learned since then: My client's mail server is Microsoft Exchange on a box physically in their office. Whenever someone on the outside world emails [email protected], the mail arrives. But if the web server sends to the same email address, it fails every time. This is not a PHP problem. I secure shell in to the web server and have tested this both with sendmail and the UNIX mail application. I've also tested it by emailing various email accounts from the shell. I can email myself, for example, just nobody at the website.com domain. In short, when I'm logged in to website.com, mail to [email protected], [email protected], [email protected] all fail. All other addresses work fine. What I've discovered is those dropped emails are routed to the web server's "catchall" account where they sit in its inbox. I've done an MX lookup on website.com. The MX record points to mailsec.website.com. I can telnet to mailsec.website.com port 25 and see the SMTP server. It appears to me that website.com isn't doing an MX lookup when it's sending mail to [email protected]. My theory is that it recognizes the domain as local, sees that there's no "requests" user account to deliver it to, and drops the mail into the catchall account. What I want is to force sendmail to do the MX lookup and send the message on to the Exchange server. I'm at wit's end here. I can't figure out how to do this. For that matter, I may be way off base here and have misdiagnosed this entirely. Internet mail and MX has always seemed a black art to me, and my ignorance is certainly showing in this question.

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• How do we, as a community, help encourage programming in public schools? (Or state Schools for the U

  - by NoMoreZealots

  PRIMARY MOTIVATION My office gets involved with the "First Robotics" competitions and one thing that lingers year to year is the students typically have no preparation for doing even simple programming as part of the public schools system. While the science classes provide some basic grasp of mechanical and electrical concepts, by in large computer programming gets no coverage from the curriculum. (This my be different in other areas of the country/world.) What makes it worse is there is only a short period of time you have to prepare the student's and help them design the robot. Talking to some professors from local colleges, it's a problem because you can't assume even the most basic understanding for freshman CS majors. Languages like Python, Lua and BASIC are simple enough for at least high school level students, if not younger. SCOPE So how do you get public schools to support a programming, at least to the level of "Try it in BASIC" examples that used to be at the end of a chapter in my Algebra book? At least enough to prepare them for event's such as the FIRST Robotic competitions. Which the primary objectives are to teach problem solving and team work, and to possible foster an interest in Math, Science and Engineering in general. (Not force feed to them, as some people her seem to be implying.) Edit: Why teach kids: (Since 2000 CS enrollment in US colleges has decreased by 70% while college enrollment has increased, this is a PROBLEM.) Saying there is no value in teaching someone programming in Jr./High school because they might think "they know programming." Is like saying there's no value in teaching High school science and physics, because they might decide they "know physics." Leading to abuse like: "I passed a high school physics class, I'm going to develop a Unified Quantum Gravitational Theory." Better Prepared students are better students. Instead it would allows college programs to raise the bar on the entry level courses, allowing students to be weeded out based on their understanding of more advanced material. Plus people who did poorly in that in topic in High school aren't as likely to say "I think there's money in computer's so I'll computer science." Plus if people take it in high school and decide THEN that it's not for them, it's better than them wasting their money to PAY a college to figure that out. The result is that people who take the degree are more likely to succeed and be there for the RIGHT reasons. (i.e. It's what they REALLY want to do. And that's REALLY the key to being good at anything.) Programming is like anything else, the more practice and genuine interest you have the better you get. If you start them later, they get less practice. The earlier give them the opportunity to start, the more practice they will get. All other things equal, the more practice the better the programmer.

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• How does Sentry aggregate errors?

  - by Hugo Rodger-Brown

  I am using Sentry (in a django project), and I'd like to know how I can get the errors to aggregate properly. I am logging certain user actions as errors, so there is no underlying system exception, and am using the culprit attribute to set a friendly error name. The message is templated, and contains a common message ("User 'x' was unable to perform action because 'y'"), but is never exactly the same (different users, different conditions). Sentry clearly uses some set of attributes under the hood to determine whether to aggregate errors as the same exception, but despite having looked through the code, I can't work out how. Can anyone short-cut my having to dig further into the code and tell me what properties I need to set in order to manage aggregation as I would like? [UPDATE 1: event grouping] This line appears in sentry.models.Group: class Group(MessageBase): """ Aggregated message which summarizes a set of Events. """ ... class Meta: unique_together = (('project', 'logger', 'culprit', 'checksum'),) ... Which makes sense - project, logger and culprit I am setting at the moment - the problem is checksum. I will investigate further, however 'checksum' suggests that binary equivalence, which is never going to work - it must be possible to group instances of the same exception, with differenct attributes? [UPDATE 2: event checksums] The event checksum comes from the sentry.manager.get_checksum_from_event method: def get_checksum_from_event(event): for interface in event.interfaces.itervalues(): result = interface.get_hash() if result: hash = hashlib.md5() for r in result: hash.update(to_string(r)) return hash.hexdigest() return hashlib.md5(to_string(event.message)).hexdigest() Next stop - where do the event interfaces come from? [UPDATE 3: event interfaces] I have worked out that interfaces refer to the standard mechanism for describing data passed into sentry events, and that I am using the standard sentry.interfaces.Message and sentry.interfaces.User interfaces. Both of these will contain different data depending on the exception instance - and so a checksum will never match. Is there any way that I can exclude these from the checksum calculation? (Or at least the User interface value, as that has to be different - the Message interface value I could standardise.) [UPDATE 4: solution] Here are the two get_hash functions for the Message and User interfaces respectively: # sentry.interfaces.Message def get_hash(self): return [self.message] # sentry.interfaces.User def get_hash(self): return [] Looking at these two, only the Message.get_hash interface will return a value that is picked up by the get_checksum_for_event method, and so this is the one that will be returned (hashed etc.) The net effect of this is that the the checksum is evaluated on the message alone - which in theory means that I can standardise the message and keep the user definition unique. I've answered my own question here, but hopefully my investigation is of use to others having the same problem. (As an aside, I've also submitted a pull request against the Sentry documentation as part of this ;-)) (Note to anyone using / extending Sentry with custom interfaces - if you want to avoid your interface being use to group exceptions, return an empty list.)

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• How can I refactor this JavaScript code to avoid making functions in a loop?

  - by Bungle

  I wrote the following code for a project that I'm working on: var clicky_tracking = [ ['related-searches', 'Related Searches'], ['related-stories', 'Related Stories'], ['more-videos', 'More Videos'], ['web-headlines', 'Publication'] ]; for (var x = 0, length_x = clicky_tracking.length; x < length_x; x++) { links = document.getElementById(clicky_tracking[x][0]) .getElementsByTagName('a'); for (var y = 0, length_y = links.length; y < length_y; y++) { links[y].onclick = (function(name, url) { return function() { clicky.log(url, name, 'outbound'); }; }(clicky_tracking[x][1], links[y].href)); } } What I'm trying to do is: define a two-dimensional array, with each instance the inner arrays containing two elements: an id attribute value (e.g., "related-searches") and a corresponding description (e.g., "Related Searches"); for each of the inner arrays, find the element in the document with the corresponding id attribute, and then gather a collection of all <a> elements (hyperlinks) within it; loop through that collection and attach an onclick handler to each hyperlink, which should call clicky.log, passing in as parameters the description that corresponds to the id (e.g., "Related Searches" for the id "related-searches") and the value of the href attribute for the <a> element that was clicked. Hopefully that wasn't thoroughly confusing! The code may be more self-explanatory than that. I believe that what I've implemented here is a closure, but JSLint complains: http://img.skitch.com/20100526-k1trfr6tpj64iamm8r4jf5rbru.png So, my questions are: How can I refactor this code to make JSLint agreeable? Or, better yet, is there a best-practices way to do this that I'm missing, regardless of what JSLint thinks? Should I rely on event delegation instead? That is, attaching onclick event handlers to the document elements with the id attributes in my arrays, and then looking at event.target? I've done that once before and understand the theory, but I'm very hazy on the details, and would appreciate some guidance on what that would look like - assuming this is a viable approach. Thanks very much for any help!

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• translating specifications into query predicates

  - by Jeroen

  I'm trying to find a nice and elegant way to query database content based on DDD "specifications". In domain driven design, a specification is used to check if some object, also known as the candidate, is compliant to a (domain specific) requirement. For example, the specification 'IsTaskDone' goes like: class IsTaskDone extends Specification<Task> { boolean isSatisfiedBy(Task candidate) { return candidate.isDone(); } } The above specification can be used for many purposes, e.g. it can be used to validate if a task has been completed, or to filter all completed tasks from a collection. However, I want to re-use this, nice, domain related specification to query on the database. Of course, the easiest solution would be to retrieve all entities of our desired type from the database, and filter that list in-memory by looping and removing non-matching entities. But clearly that would not be optimal for performance, especially when the entity count in our db increases. Proposal So my idea is to create a 'ConversionManager' that translates my specification into a persistence technique specific criteria, think of the JPA predicate class. The services looks as follows: public interface JpaSpecificationConversionManager { <T> Predicate getPredicateFor(Specification<T> specification, Root<T> root, CriteriaQuery<?> cq, CriteriaBuilder cb); JpaSpecificationConversionManager registerConverter(JpaSpecificationConverter<?, ?> converter); } By using our manager, the users can register their own conversion logic, isolating the domain related specification from persistence specific logic. To minimize the configuration of our manager, I want to use annotations on my converter classes, allowing the manager to automatically register those converters. JPA repository implementations could then use my manager, via dependency injection, to offer a find by specification method. Providing a find by specification should drastically reduce the number of methods on our repository interface. In theory, this all sounds decent, but I feel like I'm missing something critical. What do you guys think of my proposal, does it comply to the DDD way of thinking? Or is there already a framework that does something identical to what I just described?

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• Strange Map Reduce Behavior in CouchDB. Rereduce?

  - by Tony

  I have a mapreduce issue with couchdb (both functions shown below): when I run it with grouplevel = 2 (exact) I get accurate output: {"rows":[ {"key":["2011-01-11","staff-1"],"value":{"total":895.72,"count":2,"services":6,"services_ignored":6,"services_liked":0,"services_disliked":0,"services_disliked_avg":0,"Revise":{"total":275.72,"count":1},"Review":{"total":620,"count":1}}}, {"key":["2011-01-11","staff-2"],"value":{"total":8461.689999999999,"count":2,"services":41,"services_ignored":37,"services_liked":4,"services_disliked":0,"services_disliked_avg":0,"Revise":{"total":4432.4,"count":1},"Review":{"total":4029.29,"count":1}}}, {"key":["2011-01-11","staff-3"],"value":{"total":2100.72,"count":1,"services":10,"services_ignored":4,"services_liked":3,"services_disliked":3,"services_disliked_avg":2.3333333333333335,"Revise":{"total":2100.72,"count":1}}}, However, changing to grouplevel=1 so the values for all the different staff keys should be all grouped by date no longer gives accurate output (notice the total is currect but all others are wrong): {"rows":[ {"key":["2011-01-11"],"value":{"total":11458.130000000001,"count":2,"services":0,"services_ignored":0,"services_liked":0,"services_disliked":0,"services_disliked_avg":0,"None":{"total":11458.130000000001,"count":2}}}, My only theory is this has something to do with rereduce, which I have not yet learned. Should I explore that option or am I missing something else here? This is the Map function: function(doc) { if(doc.doc_type == 'Feedback') { emit([doc.date.split('T')[0], doc.staff_id], doc); } } And this is the Reduce: function(keys, vals) { // sum all key points by status: total, count, services (liked, rejected, ignored) var ret = { 'total':0, 'count':0, 'services': 0, 'services_ignored': 0, 'services_liked': 0, 'services_disliked': 0, 'services_disliked_avg': 0, }; var total_disliked_score = 0; // handle status function handle_status(doc) { if(!doc.status || doc.status == '' || doc.status == undefined) { status = 'None'; } else if (doc.status == 'Declined') { status = 'Rejected'; } else { status = doc.status; } if(!ret[status]) ret[status] = {'total':0, 'count':0}; ret[status]['total'] += doc.total; ret[status]['count'] += 1; }; // handle likes / dislikes function handle_services(services) { ret.services += services.length; for(var a in services) { if (services[a].user_likes == 10) { ret.services_liked += 1; } else if (services[a].user_likes >= 1) { ret.services_disliked += 1; total_disliked_score += services[a].user_likes; if (total_disliked_score >= ret.services_disliked) { ret.services_disliked_avg = total_disliked_score / ret.services_disliked; } } else { ret.services_ignored += 1; } } } // loop thru docs for(var i in vals) { // increment the total $ ret.total += vals[i].total; ret.count += 1; // update totals and sums for the status of this route handle_status(vals[i]); // do the likes / dislikes stats if(vals[i].groups) { for(var ii in vals[i].groups) { if(vals[i].groups[ii].services) { handle_services(vals[i].groups[ii].services); } } } // handle deleted services if(vals[i].hidden_services) { if (vals[i].hidden_services) { handle_services(vals[i].hidden_services); } } } return ret; }

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• Extend argparse to write set names in the help text for optional argument choices and define those sets once at the end

  - by Kent

  Example of the problem If I have a list of valid option strings which is shared between several arguments, the list is written in multiple places in the help string. Making it harder to read: def main(): elements = ['a', 'b', 'c', 'd', 'e', 'f'] parser = argparse.ArgumentParser() parser.add_argument( '-i', nargs='*', choices=elements, default=elements, help='Space separated list of case sensitive element names.') parser.add_argument( '-e', nargs='*', choices=elements, default=[], help='Space separated list of case sensitive element names to ' 'exclude from processing') parser.parse_args() When running the above function with the command line argument --help it shows: usage: arguments.py [-h] [-i [{a,b,c,d,e,f} [{a,b,c,d,e,f} ...]]] [-e [{a,b,c,d,e,f} [{a,b,c,d,e,f} ...]]] optional arguments: -h, --help show this help message and exit -i [{a,b,c,d,e,f} [{a,b,c,d,e,f} ...]] Space separated list of case sensitive element names. -e [{a,b,c,d,e,f} [{a,b,c,d,e,f} ...]] Space separated list of case sensitive element names to exclude from processing What would be nice It would be nice if one could define an option list name, and in the help output write the option list name in multiple places and define it last of all. In theory it would work like this: def main_optionlist(): elements = ['a', 'b', 'c', 'd', 'e', 'f'] # Two instances of OptionList are equal if and only if they # have the same name (ALFA in this case) ol = OptionList('ALFA', elements) parser = argparse.ArgumentParser() parser.add_argument( '-i', nargs='*', choices=ol, default=ol, help='Space separated list of case sensitive element names.') parser.add_argument( '-e', nargs='*', choices=ol, default=[], help='Space separated list of case sensitive element names to ' 'exclude from processing') parser.parse_args() And when running the above function with the command line argument --help it would show something similar to: usage: arguments.py [-h] [-i [ALFA [ALFA ...]]] [-e [ALFA [ALFA ...]]] optional arguments: -h, --help show this help message and exit -i [ALFA [ALFA ...]] Space separated list of case sensitive element names. -e [ALFA [ALFA ...]] Space separated list of case sensitive element names to exclude from processing sets in optional arguments: ALFA {a,b,c,d,e,f} Question I need to: Replace the {'l', 'i', 's', 't', 's'} shown with the option name, in the optional arguments. At the end of the help text show a section explaining which elements each option name consists of. So I ask: Is this possible using argparse? Which classes would I have to inherit from and which methods would I need to override? I have tried looking at the source for argparse, but as this modification feels pretty advanced I don´t know how to get going.

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• What would you do to make this code more "over-engineered"? [closed]

  - by Mez

  A friend and I got bored, and, long story short, decided to make an over-engineered FizzBuzz in PHP <?php interface INumber { public function go(); public function setNumber($i); } class FBNumber implements INumber { private $value; private $fizz; private $buzz; public function __construct($fizz = 3 , $buzz = 5) { $this->setFizz($fizz); $this->setBuzz($buzz); } public function setNumber($i) { if(is_int($i)) { $this->value = $i; } } private function setFizz($i) { if(is_int($i)) { $this->fizz = $i; } } private function setBuzz($i) { if(is_int($i)) { $this->buzz = $i; } } private function isFizz() { return ($this->value % $this->fizz == 0); } private function isBuzz() { return ($this->value % $this->buzz == 0); } private function isNeither() { return (!$this->isBuzz() AND !$this->isFizz()); } private function isFizzBuzz() { return ($this->isFizz() OR $this->isBuzz()); } private function fizz() { if ($this->isFizz()) { return "Fizz"; } } private function buzz() { if ($this->isBuzz()) { return "Buzz"; } } private function number() { if ($this->isNeither()) { return $this->value; } } public function go() { return $this->fizz() . $this->buzz() . $this->number(); } } class FizzBuzz { private $limit; private $number_class; private $numbers = array(); function __construct(INumber $number_class, $limit = 100) { $this->number_class = $number_class; $this->limit = $limit; } private function collectNumbers() { for ($i=1; $i <= $this->limit; $i++) { $n = clone($this->number_class); $n->setNumber($i); $this->numbers[$i] = $n->go(); unset($n); } } private function printNumbers() { $return = ''; foreach($this->numbers as $number){ $return .= $number . "\n"; } return $return; } public function go() { $this->collectNumbers(); return $this->printNumbers(); } } $fb = new FizzBuzz(new FBNumber()); echo $fb->go(); In theory, what could we/would you do to make it even more "over-engineered"?

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• Applying styles to a GridView matching certain criteria

  - by NickK

  Hi everyone. I'm fairly new to ASP.Net so it's probably just me being a bit stupid, but I just can't figure out why this isn't working. Basically, I have a GridView control (GridView1) on a page which is reading from a database. I already have a CSS style applied to the GridView and all I want to do is change the background image applied in the style depending on if a certain cell has data in it or not. The way I'm trying to handle this change is updating the CSS class applied to each row through C#. I have the code below doing this: protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e) { GridViewRow row = e.Row; string s = row.Cells[7].Text; if (s.Length > 0) { row.CssClass = "newRowBackground"; } else { row.CssClass = "oldRowBackground"; } } In theory, the data from Cell[7] will either be null or be a string (in this case, likely a person's name). The problem is that when the page loads, every row in the GridView has the new style applied to it, whether it's empty or not. However, when I change it to use hard coded examples, it works fine. So for example, the below would work exactly how I want it to: protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e) { GridViewRow row = e.Row; string s = row.Cells[7].Text; if (s == "Smith") //Matching a name in one of the rows { row.CssClass = "newRowBackground"; } else { row.CssClass = "oldRowBackground"; } } It seems as if the top piece of code is always returning the string with a value greater than 0, but when I check the database the fields are all null (except for my test record of "Smith"). I'm probably doing something very simple that's wrong here, but I can't see what. Like I said, I'm still very new to this. One thing I have tried is changing the argument in the if statement to things like: if (s != null), if (s != "") and if (s == string.empty) all with no luck. Any help is greatly appreciated and don't hesitate to tell me if I'm just being stupid here. :)

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• What is the best practice to segment c#.net projects based on a single base project

  - by Anthony

  Honestly, I can't word my question any better without describing it. I have a base project (with all its glory, dlls, resources etc) which is a CMS. I need to use this project as a base for othe custom bake projects. This base project is to be maintained and updated among all custom bake projects. I use subversion (Collabnet and Tortise SVN) I have two questions: 1 - Can I use subversion to share the base project among other projects What I mean here is can I "Checkout" the base project into another "Checked Out" project and have both update and commit seperatley. So, to paint a picture, let's say I am working on a custom project and I modify the core/base prject in some way (which I know will suit the others) can I then commit those changes and upon doing so when I update the base project in the other "Checked out" resources will it pull the changes? In short, I would like not to have to manually deploy updated core files whenever I make changes into each seperate project. 2 - If I create a custom file (let's say an webcontrol or aspx page etc) can I have it compile seperatley from the base project Another tricky one to explain. When I publish my web application it creates DLLs based on the namespaces of projects attached to it. So I may have a number of DLLs including the "Website's" namespace DLL, which could simply be website. I want to be able to make a seperate, custom, control which does not compile into those DLLs as the custom files should not rely on those DLLS to run. Is it as simple to set a seperate namespace for those files like CustomFiles.ProjectName for example? Think of the whole idea as adding modules to the .NET project, I don't want the module's code in any of the core DLLs but I do need for module to be able to access the core dlls. (There is no need for the core project to access the module code as it should be one way only in theory, though I reckon it woould not be possible anyway without using JSON/SOAP or something like that, maybe I am wrong.) I want to create a pluggable environment much like that of Joomla/Wordpress as since PHP generally doesn't have to be compiled first I see this is the reason why all this is possible/easy. The idea is to allow pluggable themes, modules etc etc. (I haven't tried simply adding .NET themes after compile/publish but I am assuming this is possible anyway? OR does the compiler need to reference items in the files?)

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• Coping with feelings of technical mediocrity

  - by Karim

  As I've progressed as a programmer, I noticed more nuance and areas I could study in depth. In part, I've come to think of myself from, at one point, a "guru" to now much less, even mediocre or inadequate. Is this normal, or is it a sign of a destructive excessive ambition? Background I started to program when I was still a kid, I had about 10 or 11 years. I really enjoy my work and never get bored from it. It's amazing how somebody could be paid for what he really likes to do and would be doing it anyway even for free. When I first started to program, I was feeling proud of what I was doing, each application I built was for me a success and after 2-3 year I had a feeling that I'm a coding guru. It was a nice feeling. ;-) But the more I was in the field and the more types of software I started to develop, I was starting to have a feeling that I'm completely wrong in thinking I'm a guru. I felt that I'm not even a mediocre developer. Each new field I start to work on is giving me this feeling. Like when I once developed a device driver for a client, I saw how much I need to learn about device drivers. When I developed a video filter for an application, I saw how much do I still need to learn about DirectShow, Color Spaces, and all the theory behind that. The worst thing was when I started to learn algorithms. It was several years ago. I knew then the basic structures and algorithms like the sorting, some types of trees, some hashtables, strings, etc. and when I really wanted to learn a group of structures I learned about 5-6 new types and saw that in fact even this small group has several hundred subtypes of structures. It's depressing how little time people have in their lives to learn all this stuff. I'm now a software developer with about 10 years of experience and I still feel that I'm not a proficient developer when I think about things that others do in the industry.

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• SwingWorker exceptions lost even when using wrapper classes

  - by Ti Strga

  I've been struggling with the usability problem of SwingWorker eating any exceptions thrown in the background task, for example, described on this SO thread. That thread gives a nice description of the problem, but doesn't discuss recovering the original exception. The applet I've been handed needs to propagate the exception upwards. But I haven't been able to even catch it. I'm using the SimpleSwingWorker wrapper class from this blog entry specifically to try and address this issue. It's a fairly small class but I'll repost it at the end here just for reference. The calling code looks broadly like try { // lots of code here to prepare data, finishing with SpecialDataHelper helper = new SpecialDataHelper(...stuff...); helper.execute(); } catch (Throwable e) { // used "Throwable" here in desperation to try and get // anything at all to match, including unchecked exceptions // // no luck, this code is never ever used :-( } The wrappers: class SpecialDataHelper extends SimpleSwingWorker { public SpecialDataHelper (SpecialData sd) { this.stuff = etc etc etc; } public Void doInBackground() throws Exception { OurCodeThatThrowsACheckedException(this.stuff); return null; } protected void done() { // called only when successful // never reached if there's an error } } The feature of SimpleSwingWorker is that the actual SwingWorker's done()/get() methods are automatically called. This, in theory, rethrows any exceptions that happened in the background. In practice, nothing is ever caught, and I don't even know why. The SimpleSwingWorker class, for reference, and with nothing elided for brevity: import java.util.concurrent.ExecutionException; import javax.swing.SwingWorker; /** * A drop-in replacement for SwingWorker<Void,Void> but will not silently * swallow exceptions during background execution. * * Taken from http://jonathangiles.net/blog/?p=341 with thanks. */ public abstract class SimpleSwingWorker { private final SwingWorker<Void,Void> worker = new SwingWorker<Void,Void>() { @Override protected Void doInBackground() throws Exception { SimpleSwingWorker.this.doInBackground(); return null; } @Override protected void done() { // Exceptions are lost unless get() is called on the // originating thread. We do so here. try { get(); } catch (final InterruptedException ex) { throw new RuntimeException(ex); } catch (final ExecutionException ex) { throw new RuntimeException(ex.getCause()); } SimpleSwingWorker.this.done(); } }; public SimpleSwingWorker() {} protected abstract Void doInBackground() throws Exception; protected abstract void done(); public void execute() { worker.execute(); } }

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• Declare Locally or Globally in Delphi?

  - by lkessler

  I have a procedure my program calls tens of thousands of times that uses a generic structure like this: procedure PrintIndiEntry(JumpID: string); type TPeopleIncluded = record IndiPtr: pointer; Relationship: string; end; var PeopleIncluded: TList<TPeopleIncluded>; PI: TPeopleIncluded; begin { PrintIndiEntry } PeopleIncluded := TList<TPeopleIncluded>.Create; { A loop here that determines a small number (up to 100) people to process } while ... do begin PI.IndiPtr := ...; PI.Relationship := ...; PeopleIncluded.Add(PI); end; DoSomeProcess(PeopleIncluded); PeopleIncluded.Clear; PeopleIncluded.Free; end { PrintIndiEntry } Alternatively, I can declare PeopleIncluded globally rather than locally as follows: unit process; interface type TPeopleIncluded = record IndiPtr: pointer; Relationship: string; end; var PeopleIncluded: TList<TPeopleIncluded>; PI: TPeopleIncluded; procedure PrintIndiEntry(JumpID: string); begin { PrintIndiEntry } { A loop here that determines a small number (up to 100) people to process } while ... do begin PI.IndiPtr := ...; PI.Relationship := ...; PeopleIncluded.Add(PI); end; DoSomeProcess(PeopleIncluded); PeopleIncluded.Clear; end { PrintIndiEntry } procedure InitializeProcessing; begin PeopleIncluded := TList<TPeopleIncluded>.Create; end; procedure FinalizeProcessing; begin PeopleIncluded.Free; end; My question is whether in this situation it is better to declare PeopleIncluded globally rather than locally. I know the theory is to define locally whenever possible, but I would like to know if there are any issues to worry about with regards to doing tens of thousands of of "create"s and "free"s? Making them global will do only one create and one free. What is the recommended method to use in this case? If the recommended method is to still define it locally, then I'm wondering if there are any situations where it is better to define globally when defining locally is still an option.

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• avoiding enums as interface identifiers c++ OOP

  - by AlasdairC

  Hi I'm working on a plugin framework using dynamic loaded shared libraries which is based on Eclipse's (and probally other's) extension-point model. All plugins share similar properties (name, id, version etc) and each plugin could in theory satisfy any extension-point. The actual plugin (ie Dll) handling is managed by another library, all I am doing really is managing collections of interfaces for the application. I started by using an enum PluginType to distinguish the different interfaces, but I have quickly realised that using template functions made the code far cleaner and would leave the grunt work up to the compiler, rather than forcing me to use lots of switch {...} statements. The only issue is where I need to specify like functionality for class members - most obvious example is the default plugin which provides a particular interface. A Settings class handles all settings, including the default plugin for an interface. ie Skin newSkin = settings.GetDefault<ISkin>(); How do I store the default ISkin in a container without resorting to some other means of identifying the interface? As I mentioned above, I currently use a std::map<PluginType, IPlugin> Settings::defaults member to achieve this (where IPlugin is an abstract base class which all plugins derive from. I can then dynamic_cast to the desired interface when required, but this really smells of bad design to me and introduces more harm than good I think. would welcome any tips edit: here's an example of the current use of default plugins typedef boost::shared_ptr<ISkin> Skin; typedef boost::shared_ptr<IPlugin> Plugin; enum PluginType { skin, ..., ... } class Settings { public: void SetDefault(const PluginType type, boost::shared_ptr<IPlugin> plugin) { m_default[type] = plugin; } boost::shared_ptr<IPlugin> GetDefault(const PluginType type) { return m_default[type]; } private: std::map<PluginType, boost::shared_ptr<IPlugin> m_default; }; SkinManager::Initialize() { Plugin thedefault = g_settings.GetDefault(skinplugin); Skin defaultskin = boost::dynamic_pointer_cast<ISkin>(theskin); defaultskin->Initialize(); } I would much rather call the getdefault as the following, with automatic casting to the derived class. However I need to specialize for every class type. template<> Skin Settings::GetDefault<ISkin>() { return boost::dynamic_pointer_cast<ISkin>(m_default(skin)); }

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• Directly Jump to another C++ function

  - by maligree

  I'm porting a small academic OS from TriCore to ARM Cortex (Thumb-2 instruction set). For the scheduler to work, I sometimes need to JUMP directly to another function without modifying the stack nor the link register. On TriCore (or, rather, on tricore-g++), this wrapper template (for any three-argument-function) works: template< class A1, class A2, class A3 > inline void __attribute__((always_inline)) JUMP3( void (*func)( A1, A2, A3), A1 a1, A2 a2, A3 a3 ) { typedef void (* __attribute__((interrupt_handler)) Jump3)( A1, A2, A3); ( (Jump3)func )( a1, a2, a3 ); } //example for using the template: JUMP3( superDispatch, this, me, next ); This would generate the assembler instruction J (a.k.a. JUMP) instead of CALL, leaving the stack and CSAs unchanged when jumping to the (otherwise normal) C++ function superDispatch(SchedulerImplementation* obj, Task::Id from, Task::Id to). Now I need an equivalent behaviour on ARM Cortex (or, rather, for arm-none-linux-gnueabi-g++), i.e. generate a B (a.k.a. BRANCH) instruction instead of BLX (a.k.a. BRANCH with link and exchange). But there is no interrupt_handler attribute for arm-g++ and I could not find any equivalent attribute. So I tried to resort to asm volatile and writing the asm code directly: template< class A1, class A2, class A3 > inline void __attribute__((always_inline)) JUMP3( void (*func)( A1, A2, A3), A1 a1, A2 a2, A3 a3 ) { asm volatile ( "mov.w r0, %1;" "mov.w r1, %2;" "mov.w r2, %3;" "b %0;" : : "r"(func), "r"(a1), "r"(a2), "r"(a3) : "r0", "r1", "r2" ); } So far, so good, in my theory, at least. Thumb-2 requires function arguments to be passed in the registers, i.e. r0..r2 in this case, so it should work. But then the linker dies with undefined reference to `r6' on the closing bracket of the asm statement ... and I don't know what to make of it. OK, I'm not the expert in C++, and the asm syntax is not very straightforward... so has anybody got a hint for me? A hint to the correct __attribute__ for arm-g++ would be one way, a hint to fix the asm code would be another. Another way maybe would be to tell the compiler that a1..a3 should already be in the registers r0..r2 when the asm statement is entered (I looked into that a bit, but did not find any hint).

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• PHP/MySQL Interview - How would you have answered?

  - by martincarlin87

  I was asked this interview question so thought I would post it here to see how other users would answer: Please write some code which connects to a MySQL database (any host/user/pass), retrieves the current date & time from the database, compares it to the current date & time on the local server (i.e. where the application is running), and reports on the difference. The reporting aspect should be a simple HTML page, so that in theory this script can be put on a web server, set to point to a particular database server, and it would tell us whether the two servers’ times are in sync (or close to being in sync). This is what I put: // Connect to database server $dbhost = 'localhost'; $dbuser = 'xxx'; $dbpass = 'xxx'; $dbname = 'xxx'; $conn = mysql_connect($dbhost, $dbuser, $dbpass) or die (mysql_error()); // Select database mysql_select_db($dbname) or die(mysql_error()); // Retrieve the current time from the database server $sql = 'SELECT NOW() AS db_server_time'; // Execute the query $result = mysql_query($sql) or die(mysql_error()); // Since query has now completed, get the time of the web server $php_server_time = date("Y-m-d h:m:s"); // Store query results in an array $row = mysql_fetch_array($result); // Retrieve time result from the array $db_server_time = $row['db_server_time']; echo $db_server_time . '<br />'; echo $php_server_time; if ($php_server_time != $db_server_time) { // Server times are not identical echo '<p>Database server and web server are not in sync!</p>'; // Convert the time stamps into seconds since 01/01/1970 $php_seconds = strtotime($php_server_time); $sql_seconds = strtotime($db_server_time); // Subtract smaller number from biggest number to avoid getting a negative result if ($php_seconds > $sql_seconds) { $time_difference = $php_seconds - $sql_seconds; } else { $time_difference = $sql_seconds - $php_seconds; } // convert the time difference in seconds to a formatted string displaying hours, minutes and seconds $nice_time_difference = gmdate("H:i:s", $time_difference); echo '<p>Time difference between the servers is ' . $nice_time_difference; } else { // Timestamps are exactly the same echo '<p>Database server and web server are in sync with each other!</p>'; } Yes, I know that I have used the deprecated mysql_* functions but that aside, how would you have answered, i.e. what changes would you make and why? Are there any factors I have omitted which I should take into consideration? The interesting thing is that my results always seem to be an exact number of minutes apart when executed on my hosting account: 2012-12-06 11:47:07 2012-12-06 11:12:07

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• Exception: Zend Extension ./filename.php does not exist

  - by safarov

  When i try to execute php file though CLI this message appear: Exception: Zend Extension ./filename.php does not exist But while run like this /usr/local/bin/php -q -r "echo 'test';" works as expected I tried to figure out what causing this, no success yet. Here some information about enviroment may be usefull: I have eaccelerator installed (working ok). In php.ini: zend_extension="/usr/local/lib/php/extensions/no-debug-non-zts-20100525/eaccelerator.so" eaccelerator.shm_size="16" eaccelerator.cache_dir="/var/cache/eaccelerator" eaccelerator.enable="1" eaccelerator.optimizer="1" eaccelerator.check_mtime="1" eaccelerator.debug="0" eaccelerator.filter="" eaccelerator.shm_ttl="0" eaccelerator.shm_prune_period="0" eaccelerator.shm_only="0" Apache and all sites are working Content of filename.php #!/usr/local/bin/php -q <?php echo 'test'; ?> What is the problem ?

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• xf86OpenConsole: Cannot find a free VT: Invalid argument

  - by Oliver Seeliger

  I'v set up an Ubuntu 12.04 from the precreated OpenVZ template. The host system is configured as follows: # $ cat /etc/issue Debian GNU/Linux 6.0 # $ uname -a Linux openvz-02 2.6.32-16-pve #1 SMP Fri Nov 9 11:42:51 CET 2012 x86_64 GNU/Linux # $ apt-cache showpkg proxmox-ve-2.6.32 Package: proxmox-ve-2.6.32 # $ tail -n 3 /etc/apt/sources.list # PVE packages provided by proxmox.com deb http://download.proxmox.com/debian squeeze pve For a software project I need a minimal xserver and followed the instructions at https://help.ubuntu.com/community/ServerGUI. I simply installed the package xorg (xorg 1:7.6+7ubuntu7.1). Now when I 'startx' I get an error message Fatal server error: xf86OpenConsole: Cannot find a free VT: Invalid argument The complete output of startx # startx X.Org X Server 1.11.3 Release Date: 2011-12-16 X Protocol Version 11, Revision 0 Build Operating System: Linux 2.6.42-23-generic x86_64 Ubuntu Current Operating System: Linux www 2.6.32-16-pve #1 SMP Fri Nov 9 11:42:51 CET 2012 x86_64 Kernel command line: quiet Build Date: 29 August 2012 12:12:33AM xorg-server 2:1.11.4-0ubuntu10.8 (For technical support please see http://www.ubuntu.com/support) Current version of pixman: 0.24.4 Before reporting problems, check http://wiki.x.org to make sure that you have the latest version. Markers: (--) probed, (**) from config file, (==) default setting, (++) from command line, (!!) notice, (II) informational, (WW) warning, (EE) error, (NI) not implemented, (??) unknown. (==) Log file: "/var/log/Xorg.0.log", Time: Tue Nov 20 08:46:04 2012 (==) Using system config directory "/usr/share/X11/xorg.conf.d" Fatal server error: xf86OpenConsole: Cannot find a free VT: Invalid argument Please consult the The X.Org Foundation support at http://wiki.x.org for help. Please also check the log file at "/var/log/Xorg.0.log" for additional information. ddxSigGiveUp: Closing log Server terminated with error (1). Closing log file.

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• 'Certificate types are not available' When creating computer certificate?

  - by Anicho

  Environment Windows Server 2008 sp1 Xeon CPU E5430 @ 2.66 GHz 16.0 GB Ram 64-bit Operating System 1TB Disk Space Server Role: SQL Server Other Information: Joint to domain, Logged in user domain administrator Issue Steps that cause issue: Create a computer certificate using mmc snap-in 'certificates' by right clicking on 'Certificates' folder Under 'root\Personal' tree, and clicking All Tasks - Request New Certificate. Certificate Enrollment window appears, you verify you are connected to your network and you are logged onto the domain. Then Click Next, which leads to a window stating the issue: "Certificate types are not available" "You cannot request a certificate this time because no certificate types are available. If you need a certificate contact your administrator." Wanted Solution Create a certificate on this server, to implement SSL connection to MSSQL servers.

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• CertMgr fails trying to import an SPC file

  - by nsr81

  We have an SPC files which came with the Cisco IP Communicator installer. It needs to be imported into the localMachine ROOT store. However, which the certmgr.exe is run against this SPC file, it errors out. Doesn't matter if it's run from within the installer or manually. The commands I've tried using are: certmgr.exe -add -all CDPcredentials.spc -s -r localMachine root The result displayed is: Error: Failed to save to the destination store CertMgr Failed There is no other information, no log file, nothing in the eventviewer. I's almost as if the ROOT store is in a read-only state. I would also like to point out that I'm able to import single certificates. Just not an SPC files, which contains multiple certificates. I have also tried different versions of the CertMgr utility. Running on Windows 7 Enterprise 64bit. Any assistance would be appreciated.

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• How to suppress an unwanted external Autodiscover lookup?

  - by chris

  In a small network with Exchange 2007, when starting Outlook 2010 (and once in a while afterwards), users get a prompt to confirm that it's safe to get account configuration information from cpanelemaildiscovery.cpanel.net/autodiscover/autodiscover.xml (I could read in a couple of forums that there is a bug in cpanel, but that's beside the point.) I'm puzzled because I can't find any autodiscover DNS entries anywhere, neither internally nor externally. The only hint is that we use an external hosting company for our website and for one single email address, which runs on cpanel. So I guess that Outlook makes an external DNS query to test all entries? It reates a lot of confusion for the users and frankly I'm not too happy that the external hosting company gets contacted by all our users. How can I suppress this behavior? Thanks

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• Environment variable ORACLE_UNQNAME not defined. Please set ORACLE_UNQNAME to database unique name

  - by Tapas Bose

  I have a batch file which starts the Oracle Services net start OracleOraDb11g_home1TNSListener net start OracleServiceORCL call C:\app\Edifixio\product\11.2.0\dbhome_1\BIN\emctl.bat start dbconsole pause But on executing the script I am getting: C:\windows\system32>net start OracleOraDb11g_home1TNSListener The requested service has already been started. More help is available by typing NET HELPMSG 2182. C:\windows\system32>net start OracleServiceORCL The OracleServiceORCL service is starting......... The OracleServiceORCL service was started successfully. C:\windows\system32>call C:\app\Edifixio\product\11.2.0\dbhome_1\BIN\emctl.bat start dbconsole Environment variable ORACLE_UNQNAME not defined. Please set ORACLE_UNQNAME to database unique name. Press any key to continue . . . I am using Windows 7 64 bit with Oracle 11gR2 64 bit. Any information will be very helpful. Thanks and Regards.

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• Hyper-V and Hyper-threading: On or off?

  - by CapBBeard

  Hey all, With the new Xeon CPUs supporting Hyper-threading, what is the current wisdom with regard to using it (or not) on a Hyper-V host machine? I was originally under the impression that turning it on in a virtual host environment could be detrimental as the 'extra' CPUs were not true cores. However I've also read (unconfirmed) comments along the lines of MS doing some hard work to get Hyper-V running well in a Hyper-threading environment. Does anyone have any solid information or experience in this regard? Cheers!

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• "no MPM loaded", but I'm not even using mpm

  - by ezuk

  Running Apache2 on Ubuntu Precise64 in Vagrant. When I try to start it, it says: vagrant@precise64:/etc/apache2$ /etc/init.d/apache2 start * Starting web server apache2 * * The apache2 configtest failed. Output of config test was: AH00534: apache2: Configuration error: No MPM loaded. Action 'configtest' failed. The Apache error log may have more information. But the thing is, my /etc/apache2/apache2.conf file doesn't call for MPM anywhere! I would paste it here but it would make for a huge post... I tried looking up the error log, but I can't find that anywhere, either. Help?

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• SQL SERVER – 2011 – Wait Type – Day 25 of 28

  - by pinaldave

  Since the beginning of the series, I have been getting the following question again and again: “What are the changes in SQL Server 2011 – Denali with respect to Wait Types?” SQL Server 2011 – Denali is yet to be released, and making statements on the subject will be inappropriate. Denali CTP1 has been released so I suggest that all of you download the same and experiment on it. I quickly compared the wait stats of SQL Server 2008 R2 and Denali (CTP1) and found the following changes: Wait Types Exists in SQL Server 2008 R2 and Not Exists in SQL Server 2011 “Denali” SOS_RESERVEDMEMBLOCKLIST SOS_LOCALALLOCATORLIST QUERY_WAIT_ERRHDL_SERVICE QUERY_ERRHDL_SERVICE_DONE XE_PACKAGE_LOCK_BACKOFF Wait Types Exists in SQL Server 2011 and Not Exists in SQL Server 2008 SLEEP_MASTERMDREADY SOS_MEMORY_TOPLEVELBLOCKALLOCATOR SOS_PHYS_PAGE_CACHE FILESTREAM_WORKITEM_QUEUE FILESTREAM_FILE_OBJECT FILESTREAM_FCB FILESTREAM_CACHE XE_CALLBACK_LIST PWAIT_MD_RELATION_CACHE PWAIT_MD_SERVER_CACHE PWAIT_MD_LOGIN_STATS DISPATCHER_PRIORITY_QUEUE_SEMAPHORE FT_PROPERTYLIST_CACHE SECURITY_KEYRING_RWLOCK BROKER_TRANSMISSION_WORK BROKER_TRANSMISSION_OBJECT BROKER_TRANSMISSION_TABLE BROKER_DISPATCHER BROKER_FORWARDER UCS_MANAGER UCS_TRANSPORT UCS_MEMORY_NOTIFICATION UCS_ENDPOINT_CHANGE UCS_TRANSPORT_STREAM_CHANGE QUERY_TASK_ENQUEUE_MUTEX DBCC_SCALE_OUT_EXPR_CACHE PWAIT_ALL_COMPONENTS_INITIALIZED PREEMPTIVE_SP_SERVER_DIAGNOSTICS SP_SERVER_DIAGNOSTICS_SLEEP SP_SERVER_DIAGNOSTICS_INIT_MUTEX AM_INDBUILD_ALLOCATION QRY_PARALLEL_THREAD_MUTEX FT_MASTER_MERGE_COORDINATOR PWAIT_RESOURCE_SEMAPHORE_FT_PARALLEL_QUERY_SYNC REDO_THREAD_PENDING_WORK REDO_THREAD_SYNC COUNTRECOVERYMGR HADR_DB_COMMAND HADR_TRANSPORT_SESSION HADR_CLUSAPI_CALL PWAIT_HADR_CHANGE_NOTIFIER_TERMINATION_SYNC PWAIT_HADR_ACTION_COMPLETED PWAIT_HADR_OFFLINE_COMPLETED PWAIT_HADR_ONLINE_COMPLETED PWAIT_HADR_FORCEFAILOVER_COMPLETED PWAIT_HADR_WORKITEM_COMPLETED HADR_WORK_POOL HADR_WORK_QUEUE HADR_LOGCAPTURE_SYNC LOGPOOL_CACHESIZE LOGPOOL_FREEPOOLS LOGPOOL_REPLACEMENTSET LOGPOOL_CONSUMERSET LOGPOOL_MGRSET LOGPOOL_CONSUMER LOGPOOLREFCOUNTEDOBJECT_REFDONE HADR_SYNC_COMMIT HADR_AG_MUTEX PWAIT_SECURITY_CACHE_INVALIDATION PWAIT_HADR_SERVER_READY_CONNECTIONS HADR_FILESTREAM_MANAGER HADR_FILESTREAM_BLOCK_FLUSH HADR_FILESTREAM_IOMGR XDES_HISTORY XDES_SNAPSHOT HADR_FILESTREAM_IOMGR_IOCOMPLETION UCS_SESSION_REGISTRATION ENABLE_EMPTY_VERSIONING HADR_DB_OP_START_SYNC HADR_DB_OP_COMPLETION_SYNC HADR_LOGPROGRESS_SYNC HADR_TRANSPORT_DBRLIST HADR_FAILOVER_PARTNER XDESTSVERMGR GHOSTCLEANUPSYNCMGR HADR_AR_UNLOAD_COMPLETED HADR_PARTNER_SYNC HADR_DBSTATECHANGE_SYNC We already know that Wait Types and Wait Stats are going to be the next big thing in the next version of SQL Server. So now I am eagerly waiting to dig deeper in the wait stats. Read all the post in the Wait Types and Queue series. Note: The information presented here is from my experience and there is no way that I claim it to be accurate. I suggest reading Book OnLine for further clarification. All the discussion of Wait Stats in this blog is generic and varies from system to system. It is recommended that you test this on a development server before implementing it to a production server. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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