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• Concurrency pattern of logger in multithreaded application

  - by Dipan Mehta

  The context: We are working on a multi-threaded (Linux-C) application that follows a pipeline model. Each module has a private thread and encapsulated objects which do processing of data; and each stage has a standard form of exchanging data with next unit. The application is free from memory leak and is threadsafe using locks at the point where they exchange data. Total number of threads is about 15- and each thread can have from 1 to 4 objects. Making about 25 - 30 odd objects which all have some critical logging to do. Most discussion I have seen about different levels as in Log4J and it's other translations. The real big questions is about how the overall logging should really happen? One approach is all local logging does fprintf to stderr. The stderr is redirected to some file. This approach is very bad when logs become too big. If all object instantiate their individual loggers - (about 30-40 of them) there will be too many files. And unlike above, one won't have the idea of true order of events. Timestamping is one possibility - but it is still a mess to collate. If there is a single global logger (singleton) pattern - it indirectly blocks so many threads while one is busy putting up logs. This is unacceptable when processing of the threads are heavy. So what should be the ideal way to structure the logging objects? What are some of the best practices in actual large scale applications? I would also love to learn from some of the real designs of large scale applications to get inspirations from!

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• Why would Java app make RPC call to itself?

  - by amphibient

  I am working with a multithreaded homegrown multi-module app in my new job. We use the the Thrift protocol to communicate RPC calls between different stand-alone applications in a distributed system. One of them listens on multiple ports and I just noticed that it actually makes an RPC call to itself from one thread invoked from one socket it listens to (web service call) to another port within the same app. I verified that it could accomplish the same thing if it just went and directly called the method that the remote procedure ultimately invokes as it is all within the same application, same JVM. To make it even more mysterious, the call is completely synchronous, i.e. no callbacks involved. The first thread totally sits and waits until it makes a call across the wire to itself and comes back. Now, I am perplexed why anybody would do it this way. It seems like calling somebody on the phone that sits in the same room as you do. Can anybody provide an explanation why the developer before me would come up with the above mentioned model? Maybe there is a reason and I am missing something.

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• First ATMs programming language

  - by revo

  First ATMs performed tasks like a cash dispenser, they were offline machines which worked with punch cards impregnated with Carbon and a 6-digit PIN code. Maximum withdrawal with a card was 10 pounds and each one was a one-time use card - ATM swallowed cards! The first ATM was installed in London in the year 1967, as I looked at time line of programming languages, there were many programming languages made before that decade. I don't know about the hardware neither, but in which programming language it was written? *I didn't find a detailed biography of John Shepherd-Barron (ATM inventor at 70s) Update I found this picture, which is taken from a newspaper back to the year 1972 in Iran. Translated PS : Shows Mr. Rad-lon (if spelled correctly), The manager of Barros (if spelled correctly) International Educational Institute in United Kingdom at the right, and Mr. Jim Sutherland - Expert of Computer Kiosks. In the rest of the text I found on this paper, these kind of ATMs which called "Automated Computer Kiosk" were advertised with this: Mr. Rad-lon (if spelled correctly) puts his card to one specific location of Automated Computer Kiosk and after 10 seconds he withdraws his cash. Two more questions are: 1- How those ATMs were so fast? (withdrawal in 10 seconds in that year) 2- I didn't find any text on Internet which state about "Automated Computer Kiosk", Is it valid or were they being called Computer in that time?

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• Versioning APIs

  - by Sharon

  Suppose that you have a large project supported by an API base. The project also ships a public API that end(ish) users can use. Sometimes you need to make changes to the API base that supports your project. For example, you need to add a feature that needs an API change, a new method, or requires altering of one of the objects, or the format of one of those objects, passed to or from the API. Assuming that you are also using these objects in your public API, the public objects will also change any time you do this, which is undesirable as your clients may rely on the API objects remaining identical for their parsing code to work. (cough C++ WSDL clients...) So one potential solution is to version the API. But when we say "version" the API, it sounds like this also must mean to version the API objects as well as well as providing duplicate method calls for each changed method signature. So I would then have a plain old clr object for each version of my api, which again seems undesirable. And even if I do this, I surely won't be building each object from scratch as that would end up with vast amounts of duplicated code. Rather, the API is likely to extend the private objects we are using for our base API, but then we run into the same problem because added properties would also be available in the public API when they are not supposed to be. So what is some sanity that is usually applied to this situation? I know many public services such as Git for Windows maintains a versioned API, but I'm having trouble imagining an architecture that supports this without vast amounts of duplicate code covering the various versioned methods and input/output objects. I'm aware that processes such as semantic versioning attempt to put some sanity on when public API breaks should occur. The problem is more that it seems like many or most changes require breaking the public API if the objects aren't more separated, but I don't see a good way to do that without duplicating code.

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• Using a Vertex Buffer and DrawUserIndexedPrimitives?

  - by MattMcg

  Let's say I have a large but static world and only a single moving object on said world. To increase performance I wish to use a vertex and index buffer for the static part of the world. I set them up and they work fine however if I throw in another draw call to DrawUserIndexedPrimitives (to draw my one single moving object) after the call to DrawIndexedPrimitives, it will error out saying a valid vertex buffer must be set. I can only assume the DrawUserIndexedPrimitive call destroyed/replaced the vertex buffer I set. In order to get around this I must call device.SetVertexBuffer(vertexBuffer) every frame. Something tells me that isn't correct as that kind of defeats the point of a buffer? To shed some light, the large vertex buffer is the final merged mesh of many repeated cubes (think Minecraft) which I manually create to reduce the amount of vertices/indexes needed (for example two connected cubes become one cuboid, the connecting faces are cut out), and also the amount of matrix translations (as it would suck to do one per cube). The moving objects would be other items in the world which are dynamic and not fixed to the block grid, so things like the NPCs who move constantly. How do I go about handling the large static world but also allowing objects to freely move about?

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• Best Usage of Multiple Computers For a Developer

  - by whaley

  I have two Macbook Pros - both are comparable in hardware. One is a 17" and the other a 15". The 17" has a slightly swifter CPU clock speed, but beyond that the differences are completely negligible. I tried a setup a while back where I had the 17" hooked up to an external monitor in the middle of my desk with the 15" laptop immediately to the right of it, and was using teleport to control the 15" from my 17". All development, terminal usage, etc. etc. was being done on the 17" and the 15" was primarily used for email / IM / IRC... or anything secondary to what I was working on. I have a MobileMe account so preferences were synced, but otherwise I didn't really use anything else to keep the computers in sync (I use dropbox/git but probably not optimally). For reasons I can't put my finger on, this setup never felt quite right. A few things that irked me was the 15" was way under-utlized and the 17" was overutilized having 2 laptops and a 21" monitor all on one desk actually took up lots of desk space and it felt like I had too much to look at. I reverted back to just using the 17" and the external monitor and keeping the 15" around the house (and using it very sparingly). For those of you who are using multiple laptops (or just multiple machines for that matter), I'd like to see setups that work for you for when you have 2 or more machines that gives you optimal productivity and why. I'd like to give this one more shot but with a different approach than my previous - which was using the 15" as a machine for secondary things (communication, reading documentation, etc. etc).

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• Threading models when talking to hardware devices

  - by Fuzz

  When writing an interface to hardware over a communication bus, communications timing can sometimes be critical to the operation of a device. As such, it is common for developers to spin up new threads to handle communications. It can also be a terrible idea to have a whole bunch of threads in your system, an in the case that you have multiple hardware devices you may have many many threads that are out of control of the main application. Certainly it can be common to have two threads per device, one for reading and one for writing. I am trying to determine the pros and cons of the two different models I can think of, and would love the help of the Programmers community. Each device instance gets handles it's own threads (or shares a thread for a communication device). A thread may exist for writing, and one for reading. Requested writes to a device from the API are buffered and worked on by the writer thread. The read thread exists in the case of blocking communications, and uses call backs to pass read data to the application. Timing of communications can be handled by the communications thread. Devices aren't given their own threads. Instead read and write requests are queued/buffered. The application then calls a "DoWork" function on the interface and allows all read and writes to take place and fire their callbacks. Timing is handled by the application, and the driver can request to be called at a given specific frequency. Pros for Item 1 include finer grain control of timing at the communication level at the expense of having control of whats going on at the higher level application level (which for a real time system, can be terrible). Pros for Item 2 include better control over the timing of the entire system for the application, at the expense of allowing each driver to handle it's own business. If anyone has experience with these scenarios, I'd love to hear some ideas on the approaches used.

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• Emulating Button Press Using Kinect/SimpleOpenNI + Processing Depth

  - by Alex Lu

  I am using Kinect with Simple OpenNI and Processing, and I was trying to use the Z position of a hand to emulate a button press. So far when I try it using one hand it works really well, however, when I try to get it to work with a second hand, only one of the hands work. (I know it can be more efficient by moving everything except the fill out of the if statements, but I kept those in there just in case I want to change the sizes or something.) irz and ilz are the initial Z positions of the hands when they are first recognized by onCreateHands and rz and lz are the current Z positions. As of now, the code works fine with one hand, but the other hand will either stay pressed or unpressed. If i comment one of the sections out, it works fine as well. if (rz - irz > 0) { pushStyle(); fill(60); ellipse(rx, ry, 10, 10); popStyle(); rpressed = true; } else { pushStyle(); noFill(); ellipse(rx, ry, 10, 10); popStyle(); rpressed = false; } if (lz - ilz > 0) { pushStyle(); fill(60); ellipse(lx, ly, 10, 10); popStyle(); lpressed = true; } else { pushStyle(); noFill(); ellipse(lx, ly, 10, 10); popStyle(); lpressed = false; } I tried outputting the values of rz - irz and lz - ilz and the numbers range from small negative values to small positive values (around -8 to 8) for lz - ilz. But rz - irz outputs numbers from around 8-30 depending on each time I run it and is never consistent. Also, when I comment out the code for the lz-ilz, the values for rz-irz look just fine and it operates as intended. Is there a reason tracking both Z positions throws off one hand? And is there a way to get it to work? Thanks!

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• Parse text file on click - and then display

  - by John R

  I am thinking of a methodology for rapid retrieval of code snippets. I imagine an HTML table with a setup like this: one two ... ten one oneTwo() oneTen() two twoOne() twoTen() ... ten tenOne() tenTwo() When a user clicks a function in this HTML table, a snippet of code is shown in another div tag or perhaps a popup window (I'm open to different solutions). I want to maintain only one PHP file named utitlities.php that contains a class called 'util'. This file & class will hold all the functions referenced in the above table (it is also used on various projects and is functional code). A key idea is that I do not want to update the HTML documentation everytime I write/update a new function in utilities.php. I should be able to click a function in the table and have PHP open the utilities file, parse out the apropriate function and display it in an HTML window. Questions: 1) I will be coding this in PHP and JavaScript but am wondering if similar scripts are available (for all or part) so I don't reinvent the wheel. 2) Quick & easy Ajax suggestions appreciated too (probably will use jquery, but am rusty). 3) Methodology for parsing out the functions from the utilities.php file (I'm not to good with regex).

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• Virtual Pageview Goal Funnel Not Tracking Correctly

  - by cphill

  I have an AJAX form that has three stages: 1. The landing page where a user fills out a form and selects between three question sets and clicks begin assessment 2. The assessment page, where users fill out questions relating to the question set that they selected on the landing page. 3.The results page, which shows whether they are at High Risk or Low Risk. Since this is an AJAX form that does not open a new page for each step of the process, I implemented a virtual pageview that would fire on the pageload of each step of the form process. The following is my virtual pageview setup for each stage: /form/begin-assessment /form/assessment/* (* = Three different virtual pageviews depending on the users selection of the three sets of questions: /one, /two, /three) 3./form/finished-assessment I have set up three separate goals to track user progress through each step of the form assessment. Here is my Goal setup: Goal Description: -Goal Type: Destination Goal Details: -Destination: /form/finished-assessment -Funnel: On Step 1: /form/begin-assessment (Required: Yes) Step 2: /form/assessment/one (Step 2: replace /one with /two or /three and you have my two other goals setup) Now my goals are recording the correct data in the first step and show the completions in the destination, but the second step does not show any drop offs. They show the same data as the destination. Any ideas of how I set up the goals wrong?

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• How do you make slides for programming talks?

  - by Yuvi Masory

  I've given a few talks recently and I have not found a good way to make slides. Here are a few desirable characteristics for programming slides: They're slides. A standard emacs buffer won't do it. They have syntax highlighting for code. They support basic formatting, like font size and color and bullets. No fancy animations needed. The only animation I desire is one-by-one appearance of bullets. So far I have considered: Microsoft Office - out of the question for Linux users. OpenOffice.org - too much for my needs, code formatting/highlighting needs to be done externally and pasted in. On the plus side supports bullets, bullet-by-bullet animation, and font formatting. Emacs - Supports all the code formatting but I haven't found a slides mode that lets me transition from one chunk to another. HTML5 - I once made slides using html5rocks as a template. It supports everything, but is too hard and time-consuming the "throw together" a few slides before a minor talk. Also the html5-only features may not work on the podium computer's installed browser. Any suggestions for programs/techniques for making code-centric presentations?

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• I have discovered a fundamental truth about TV shows and plots

  - by Steve Loethen

  For years, we have all known (okay, maybe I give people too much credit) that there is a very small finite number of plots.  I propose a project.  Let’s use the blogosphere to catalog those plotlines, and then find and document the episodes of shows that use them, including the show title. As evidence, how many shows have used the following plot line:? The standard “evil twin” plotline?  Once relegated to soaps, it has show up in crime shows, with the twist of DNA.  Step one, concentrate one this one.  Tell me about every show you recall that has used this plot.  I will collect and document the shows on my website (www.loethen.net) and we can build a database of the plots. Step two, what other common themes should I offer up?  How about the bigamist plot line?  The “bad guy was dead” plot line (revenge from the dead"?  The “vast government conspiracy” plotline? Let the games begin….

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• Why does Unity not extend to my 2nd monitor, even when it is displaying an X-Screen?

  - by Gridwalker

  I recently added a 2nd video card to my system, but unity refuses to extend my desktop over to the second screen. Although the secondary monitor initialises when I boot and I can move the mouse cursor over to the 2nd screen, the screen is otherwise blank (showing no wallpaper or interface elements) and I am unable to move any windows to this monitor. Moving the mouse cursor over to the 2nd monitor changes it from the default cursor to the old-style X cursor, such as the one that appears when you run X-kill, indicating that this screen is initialised in the X Server but that Unity is not recognising it. Although the Nvidia X Server Settings application can see both monitors, the unity systems settings application does not detect the 2nd adapter. Sometimes the additional drivers application can see both adapters, but it doesn't consistently show options for them both. Xrandr also fails to detect the 2nd monitor, but iNex lists both adapters. I have experimented with several different drivers for each adapter and with setting each of the graphics cards as the primary adapter in the BIOS, but this has made little difference. The two adapters are an onboard Geforce 8200 and a PCIE Geforce 7200 GX. The onboard adapter is currently set as the primary, however this adapter crashes whenever I use the Nouveau driver and I have to switch over to the PCIE as a primary whenever I purge the proprietary drivers (switching back when the 304 driver has been reinstalled). It doesn't matter which adapter I set as my primary, the results are the same : one screen showing the unity interface and one screen showing an X-Screen that only displays the mouse cursor. All I want is to be able to run this system in a dual screen configuration. I am not a gamer, nor do I require 3D rendering capabilities. Anything you can suggest to get the desktop to extend across both screens will be massively appreciated!

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• Parameterized Django models

  - by mgibsonbr

  In principle, a single Django application can be reused in two or more projects, providing functionality relevent to both. That implies that the same database structure (tables and relations) will be re-created identically in different databases, and most times this is not a problem (assuming the projects/databases are unrelated - for instance when someone downloads a complete app to use in their own projects). Sometimes, however, the models must be "tweaked" a little to better fit the problem needs. This can be accomplished by forking the app, but I wondered if there wouldn't be a better option in cases where the app designer can anticipate the most common customizations. For instance, if I have a model that could relate to another as one-to-one or one-to-many, I could specify the unique property as a parameter, that can be specified in the project's settings: class This(models.Model): other = models.ForeignKey(Other, unique=settings.OTHER_TO_THIS) Or if a model can relate to many others, I could create an intermediate table for each of them (thus enforcing referential integrity) instead of using generic fks: for related in settings.MODELS_RELATED_TO_OTHER: model_name = '%s_Other' % related globals()[model_name] = type(model_name, (models.Model,) { me:models.ForeignKey(find_model_class(related)), other:models.ForeignKey(Other), # Some other properties all intersection tables must have }) Etc. Let me stress out that I'm not proposing to change the models at runtime nor anything like that; once the parameters were defined and syncdb called for the first time, those parameters are not to be changed again (unless you're doing a schema migration). Is this a good design? Are there better ways to accomplish the same thing, or maybe drawbacks I coulnd't anticipate? This technique is meant to be used sparingly (only on apps meant to be reused in wildly different contexts, and only when a specific need of customization can be detected while the app model is being designed).

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• Law of Demeter confusion [duplicate]

  - by user2158382

  This question already has an answer here: Rails: Law of Demeter Confusion 4 answers I am reading a book called Rails AntiPatterns and they talk about using delegation to to avoid breaking the Law of Demeter. Here is their prime example: They believe that calling something like this in the controller is bad (and I agree) @street = @invoice.customer.address.street Their proposed solution is to do the following: class Customer has_one :address belongs_to :invoice def street address.street end end class Invoice has_one :customer def customer_street customer.street end end @street = @invoice.customer_street They are stating that since you only use one dot, you are not breaking the Law of Demeter here. I think this is incorrect, because you are still going through customer to go through address to get the invoice's street. I primarily got this idea from a blog post I read: http://www.dan-manges.com/blog/37 In the blog post the prime example is class Wallet attr_accessor :cash end class Customer has_one :wallet # attribute delegation def cash @wallet.cash end end class Paperboy def collect_money(customer, due_amount) if customer.cash < due_ammount raise InsufficientFundsError else customer.cash -= due_amount @collected_amount += due_amount end end end The blog post states that although there is only one dot customer.cash instead of customer.wallet.cash, this code still violates the Law of Demeter. Now in the Paperboy collect_money method, we don't have two dots, we just have one in "customer.cash". Has this delegation solved our problem? Not at all. If we look at the behavior, a paperboy is still reaching directly into a customer's wallet to get cash out. Can somebody help me clear the confusion. I have been searching for the past 2 days trying to let this topic sink in, but it is still confusing.

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• Why doesn't unity show icons or panel after installing numix theme?

  - by Sid

  I'm a beginner to Ubuntu/Linux and I have a problem: Unity is not loading! When I choose Unity in the log-in screen, I get notifications and I can see the mouse, but that's it. I have Ubuntu 14.04 installed, along with Bumblebee/Primus. I had no issues whatsoever, until I decided to try the numix-theme and the numix icon pack. I added the PPA and installed it, but when I logged off and logged back on, nothing showed up. I panicked, and in tty1, I purged numix-* but that did not solve the issue. To get by day-to-day use, I installed gnome-flashback, and among those environments, only the metacity one works. (The compiz one does not.) I've tried installing the unity-tweak-tool to reset unit, installing dconf and doing: dconf reset -f /org/compiz/ but that didn't work either. One site even told me to delete /org/compiz/, but that did not resolve the issue. When I checked ccsm, the Unity plugin had a check to it. I also tried with Unity doesn't load, no Launcher, no Dash appears, but it gets stuck on "loading icons". Any help will be awesome!

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• Whats a good way to do Collision with 2D Rectangles? can someone give me a tip?

  - by Javier

  using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Xna.Framework; namespace BreakOut { class Field { public static Field generateField() { List<Block> blocks = new List<Block>(); for (int j = 0; j < BlockType.BLOCK_TYPES.Length; j++) for (int i = 0; i < (Game1.WIDTH / Block.WIDTH); i++) { Block b = new Block(BlockType.BLOCK_TYPES[j], new Vector2(i * Block.WIDTH, (Block.HEIGHT + 2) * j + 5)); blocks.Add(b); } return new Field(blocks); } List<Block> blocks; public Field(List<Block> blocks) { this.blocks = blocks; } public void Update(GameTime gameTime, Ball b) { List<Block> removals = new List<Block>(); foreach (Block o in blocks) { if (o.BoundingBox.Intersects(new Rectangle((int)b.pos.X, (int)b.pos.Y, Ball.WIDTH, Ball.HEIGHT))) //collision with blocks { removals.Add(o); } } foreach(Block o in removals) blocks.Remove(o); //removes the blocks, but i need help hitting one at a time } public void Draw(GameTime gameTime) { foreach (Block b in blocks) b.Draw(gameTime); } } } My problem is that My collision in this sucks. I'm trying to add collision with a ball and hitting against a block and then one of the blocks dissapear. The problem i'm having is: When the ball hits the block, it removes it all in one instance. Please people don't be mean and say mean answers to me, im just in highschool, still a nooby and trying to learn more c#/XNA..

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• Multiple URL's going to same page - Kosher for Google?

  - by Ashoka15

  I hear conflicting answers from people about this, and I'm a developer by trade, and my SEO knowledge is not what it should be. Here's my situation: I run a website that lists hotels, restaurants, bars, shops, etc for a small Asian beach town. Lots of establishments here are hotels with a restaurant and bar, as well as restaurants that are also bars. As en example, a Mexican restaurant that also functions as a full cocktail bar. I first set it up so each establishment has one page, but can create multiple pages based on their other areas of business. This forces people to create TWO listings under the same name, and most just add the exact same information onto each page, making things redundant. I am re-arranging the database so that a establishment has only ONE listing (one unique page referenced by the unique code '12345ABCDEF') that is accessible from browsing under "Restaurants" and "Bars", and has the URL structures: site.com/dining/mexican/12345ABCDEF/business-name.html site.com/bars/cocktail_bars/12345ABCDEF/business-name.html I could easily simplify the URL to just the unique code and name: site.com/12345ABCDEF/business-name.html But, I found that Google has parsed by URL structure and lists like this on their SERP: Home > Dining > Mexican With each pointing to the default page for homepage, restaurants and Mexican restaurants. If I simplify the URL structure, will I lose these associations? Could Google also be picking up this structure from my breadcrumb trail at the top of the page? What is the best way to set up URL's on these pages so I am not penalized by Google for having identical information on two URL's, while still being able to have places show up as they did with the old system?

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• Tomcat + Spring + CI workflow

  - by ex3v

  We're starting our very first project with Spring and java web stack. This project will be mainly about rewriting quite large ERP/CRM from Zend Framework to Java. Important factor in my question is that I come from php territory, where things (in terms of quality) tend to look different than in java world. Fatcs: there will be 2-3 developers, at least one of developers uses Windows, rest uses Linux, there is one remote linux-based machine, which should handle test and production instances, after struggling with buggy legacy code, we want to introduce good programming and development practices (CI, tests, clean code and so on) client: internal, frequent business logic changes, scrum, daily deployments What I want to achieve is good workflow on as many development stages as possible (coding - commiting - testing - deploying). The problem is that I've never done this before, so I don't know what are best practices to do this. What I have so far is: developers code locally, there is vagrant instance on every development machine, managed by puppet. It contains the same linux, jenkins and tomcat versions as production machine, while coding, developer deploys to vagrant machine, after local merge to test branch, jenkins on vagrant handles tests, when everything is fine, developer pushes commits and merges jenkins on remote machine pulls commit from test branch, runs tests and so on, if everything looks green, jenkins deploys to test tomcat instance Deployment to production is manual (altough it can be done using helping scripts) when business logic is tested by other divisions and everything looks fine to client. Now, the real question: does above make any sense? Things that I'm not sure about: Remote machine: won't there be any problems with two (or even three, as jenkins might need one) instances of same app on tomcat? Using vagrant to develop on php environment is just vise. Isn't this overkill while using Tomcat? I mean, is there higher probability that tomcat will act the same on every machine? Is there sense of having local jenkins on vagrant?

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• How system services are started in 12.10?

  - by Salem

  One thing that always confused me in Ubuntu was how system services are started. I know that Ubuntu uses Upstart and supports SysV, but which one is used to start the services? This matters when you want a "manual" start for a service. For example, on my system i have files for the following services either in /etc/init.d/<service> (Upstart) and /etc/init/<service>.conf (SysV): acpid, mysql, networking, qemu-kvm, ufw, libvirt-bin So if i want to disable MySQL execution at startup, i must use the Upstart way or the SysV way to disable it? Also, how can i tell which of those is really used to start a generic service? Edit The really doubt here is not how disable/enable services using SysV/Upstart. What really confuses me is that some services seem to be defined (and enabled) in SysV and Upstart at the same time. Is there any precedence between them (like if mysql is enabled in both launch it using SysV)? Or can it be the case that one tool uses the other in background?

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• Parse text file on click and display

  - by John R

  I am thinking of a methodology for rapid retrieval of code snippets. I imagine an HTML table with a setup like this: one two ... ten one oneTwo() oneTen() two twoOne() twoTen() ... ten tenOne() tenTwo() When a user clicks a function in this HTML table, a snippet of code is shown in another div tag or perhaps a popup window (I'm open to different solutions). I want to maintain only one PHP file named utitlities.php that contains a class called 'util'. This file & class will hold all the functions referenced in the above table (it is also used on various projects and is functional code). A key idea is that I do not want to update the HTML documentation everytime I write/update a new function in utilities.php. I should be able to click a function in the table and have PHP open the utilities file, parse out the apropriate function and display it in an HTML window. Questions: 1) I will be coding this in PHP and JavaScript but am wondering if similar scripts are available (for all or part) so I don't reinvent the wheel. 2) Quick & easy Ajax suggestions appreciated too (probably will use jquery, but am rusty). 3) Methodology for parsing out the functions from the utilities.php file (I'm not to good with regex).

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• General List of Common Programming Errors

  - by javamonkey79

  As one journey's from apprentice to journeyman to master I've noticed that one accumulates a list of best practices for things they've been bitten by. Personally, I write most of my stuff in java & SQL so my list tends to be slated towards them. I've accumulated the following: When doing list removal, always reverse iterate Avoid adding items to a list you are currently iterating on Watch out for NullPointerExceptions Now, I know there are language specific "common errors" links out there like this one. And I'm also aware of the pragmatic programmer tips, Martin Fowler's "code smells". Does anyone know of any good lists out there of things like I've listed above (re: list removal, adding items, etc). My guess is that there are some good QA folks out there that can probably throw me a bone here. I'm not looking for things the compiler can catch - I'm looking for common things that cause bugs. In the event that there isn't a list out there already then I welcome posting your own findings here. Thanks in advance!

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• Dual Monitor 'How To' for 12.04

  - by Kim Prince

  I recently built my own PC and was delighted with the result, except for a problem with dual monitors. After having tried a few different combinations of hardware, I think what I really need is a 'how to' explanation. My motherboard is an MSI Z77MA-G45, which has an analogue, a DVI, and a HDMI port. Initially I hooked monitors up to the DVI and analogue port and it seemed to work fine. Both screens worked independently of each other, it was great. After a few days I started turning my PC off at night, and when I tried to turn it back on it would boot into the terminal mode. I would have to turn one of the monitors off and after rebooting a few times, it would eventually boot into an X Window session. Occasionally I would see an error relating to Xorg. I upgraded the motherboard BIOS but that made no difference. Eventually, I installed a graphics card - an NVIDIA GeForce GT 520. Now it seems that my on board graphics have been disabled completely, and I am reliant on the graphics card. Furthermore, the graphics card seems to only recognise one screen at a time. (The first time I rebooted with both plugged in, it flashed up a message saying that it was auto-selecting DVI). Anyhow, I think I need some 'how to' (or perhaps 'where to'), from here. For example, is X Windows configuration the next place to look? And how do I go about configuring X Windows? (Note that in Systems Settings it says my graphics driver is 'unknown', and when I ask it to detect monitors, it sees only the one!)

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• java web application best practices

  - by Bruce

  Hi all I'm trying to figure out the optimum way to develop and release a fairly simple web application, and I'm running into several problems. I'll outline the decisions I've made, because somewhere I've clearly gone off the rails.. Hugely grateful for any help! I have what I think is a fairly simple web application. It contains a couple of jsps that reference a couple of java beans, and the usual static html, js, css and images. Decision 1) I wanted to have a clear and clean release procedure, such that I could develop on my local machine and then release reliably to a production machine. I therefore made the decision to package the application into a war file (including all the static resources), to minimize the separate bits and pieces I would need to release. So far so good? Decision 2) I wanted things on my local machine to be as similar as possible to the production environment. So in my html, for example, I may have a reference to a static file such as http://static.foo.com/file . To keep this code working seamlessly on dev and prod, I decided to put static.foo.com in my /etc/hosts when developing locally, so that all the urls work correctly without changing anything. Decision 3) I decided to use eclipse and maven to give me a best practice environment for administering and building my project. So I have a nice tight set up now, except that: Every time I want to change anything in development, like one line in an html file, I have to rebuild the entire project and then wait for tomcat to load the war before I can see if it's what I wanted. So my questions are: 1) Is there a way to connect up eclipse and tomcat so that I don't have to rebuild the war each time? ie tomcat is looking straight at my actual workspace to serve up the static files? 2)I think I'm maybe making things harder by using /etc/hosts to reflect production urls - is there a better way that doesn't involve manually changing over urls (relative urls are fine of course, but where you have many subdomains, say one for static files and one for dynamic, you have to write out the full path, surely?) 3) Is this really best practice?? How do people set things up so that they balance the requirement for an automated, all-encompassing build process on the one hand, and the speed and flexibility to be able to develop javascript and html and css quickly, as quickly as if one just pointed apache at the directory and developed live? What do people find works? Many thanks!

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• overwrite existing entity via bulkloader.Loader

  - by Ray Yun

  I was going to CSV based export/import for large data with app engine. My idea was just simple. First column of CSV would be key of entity. If it's not empty, that row means existing entity and should overwrite old one. Else, that row is new entity and should create new one. I could export key of entity by adding key property. class FrontExporter(bulkloader.Exporter): def __init__(self): bulkloader.Exporter.__init__(self, 'Front', [ ('__key__', str, None), ('name', str, None), ]) But when I was trying to upload CSV, it had failed because bulkloader.Loader.generate_key() was just for "key_name" not "key" itself. That means all exported entities in CSV should have unique 'key_name' if I want to modify-and-reupload them. class FrontLoader(bulkloader.Loader): def __init__(self): bulkloader.Loader.__init__(self, 'Front', [ ('_UNUSED', lambda x: None), ('name', lambda x: x.decode('utf-8')), ]) def generate_key(self,i,values): # first column is key keystr = values[0] if len(keystr)==0: return None return keystr I also tried to load key directly without using generate_key(), but both failed. class FrontLoader(bulkloader.Loader): def __init__(self): bulkloader.Loader.__init__(self, 'Front', [ ('Key', db.Key), # not working. just create new one. ('__key__', db.Key), # same... So, how can I overwrite existing entity which has no 'key_name'? It would be horrible if I should give unique name to all entities..... From the first answer, I could handle this problem. :) def create_entity(self, values, key_name=None, parent=None): # if key_name is None: # print 'key_name is None' # else: # print 'key_name=<',key_name,'> : length=',len(key_name) Validate(values, (list, tuple)) assert len(values) == len(self._Loader__properties), ( 'Expected %d columns, found %d.' % (len(self._Loader__properties), len(values))) model_class = GetImplementationClass(self.kind) properties = { 'key_name': key_name, 'parent': parent, } for (name, converter), val in zip(self._Loader__properties, values): if converter is bool and val.lower() in ('0', 'false', 'no'): val = False properties[name] = converter(val) if key_name is None: entity = model_class(**properties) #print 'create new one' else: entity = model_class.get(key_name) for key, value in properties.items(): setattr(entity, key, value) #print 'overwrite old one' entities = self.handle_entity(entity) if entities: if not isinstance(entities, (list, tuple)): entities = [entities] for entity in entities: if not isinstance(entity, db.Model): raise TypeError('Expected a db.Model, received %s (a %s).' % (entity, entity.__class__)) return entities def generate_key(self,i,values): # first column is key if values[0] is None or values[0] in ('',' ','-','.'): return None return values[0]

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