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• Good Secure Backups Developers at Home

  - by slashmais

  What is a good, secure, method to do backups, for programmers who do research & development at home and cannot afford to lose any work? Conditions: The backups must ALWAYS be within reasonably easy reach. Internet connection cannot be guaranteed to be always available. The solution must be either FREE or priced within reason, and subject to 2 above. Status Report This is for now only considering free options. The following open-source projects are suggested in the answers (here & elsewhere): BackupPC is a high-performance, enterprise-grade system for backing up Linux, WinXX and MacOSX PCs and laptops to a server's disk. Storebackup is a backup utility that stores files on other disks. mybackware: These scripts were developed to create SQL dump files for basic disaster recovery of small MySQL installations. Bacula is [...] to manage backup, recovery, and verification of computer data across a network of computers of different kinds. In technical terms, it is a network based backup program. AutoDL 2 and Sec-Bk: AutoDL 2 is a scalable transport independant automated file transfer system. It is suitable for uploading files from a staging server to every server on a production server farm [...] Sec-Bk is a set of simple utilities to securely back up files to a remote location, even a public storage location. rsnapshot is a filesystem snapshot utility for making backups of local and remote systems. rbme: Using rsync for backups [...] you get perpetual incremental backups that appear as full backups (for each day) and thus allow easy restore or further copying to tape etc. Duplicity backs directories by producing encrypted tar-format volumes and uploading them to a remote or local file server. [...] uses librsync, [for] incremental archives Other Possibilities: Using a Distributed Version Control System (DVCS) such as Git(/Easy Git), Bazaar, Mercurial answers the need to have the backup available locally. Use free online storage space as a remote backup, e.g.: compress your work/backup directory and mail it to your gmail account. Strategies See crazyscot's answer

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• Soon to be PhD in Computer Science - Which Path to Follow?

  - by mttr

  I am going to submit my PhD thesis within the next six months. My PhD is on managing the availabiity of large-scale distributed systems, so I have some experience actually building non-trivial systems (+ I have four years experience working as a programmer). I am now trying to figure out what I should do following the PhD. I enjoy research (a quick definition: identify problem, come up with solution, ask interesting questions, find ways to answer them, build system, experiment, contribute some new knowledge and publish). I also like teaching and supervising students. It would seem that a career in academia is the ideal thing to do (can work on non-trivial problems and contribute something of use to some or more people). However, a career in academia has two significant drawbacks. First, it can be difficult to gain access to real systems with real users which then display real problems. This creates the danger that you do work that seems important (to you and maybe to some of your colleagues), but is not really relevant to anything or anyone. Second, the pay is pretty sad. Apparently, you have to sacrifice this for the privilege of doing research. I enjoy programming, but don't just want to hack some web-based system for the rest of my life. That is, working in IT for a bank is not a future I see myself enjoying. I want to work on interesting problms (that's difficult to define clearly): things where you don't know how to start, that take some time to figure out and attack, that require a rigorous approach to demonstrate that the problem has been solved, and problems that need a solution in the real world. Give the experience of people on stackoverflow, what do you think suitable options are and why (or alternatively, what gaps in my thinking does the above reveal)? Is industrial research (aka IBM Research, Microsoft Research) the only alternative avenue to a career in academia? What other areas, companies, occupations, etc. could provide me with stimulating, inspiring work? Which regions, countries am I most likely to find such work? Please share your experience.

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• Setting up Django on an internal server (os.environ() not working as expected?)

  - by monkut

  I'm trying to setup Django on an internal company server. (No external connection to the Internet.) Looking over the server setup documentation it appears that the "Running Django on a shared-hosting provider with Apache" method seems to be the most-likely to work in this situation. Here's the server information: Can't install mod_python no root access Server is SunOs 5.6 Python 2.5 Apache/2.0.46 I've installed Django (and flup) using the --prefix option (reading again I probably should've used --home, but at the moment it doesn't seem to matter) I've added the .htaccess file and mysite.fcgi file to my root web directory as mentioned here. When I run the mysite.fcgi script from the server I get my expected output (the correct site HTML output). But, it won't when trying to access it from a browser. It seems that it may be a problem with the PYTHONPATH setting since I'm using the prefix option. I've noticed that if I run mysite.fcgi from the command-line without setting the PYTHONPATH enviornment variable it throws the following error: prompt$ python2.5 mysite.fcgi ERROR: No module named flup Unable to load the flup package. In order to run django as a FastCGI application, you will need to get flup from http://www.saddi.com/software/flup/ If you've already installed flup, then make sure you have it in your PYTHONPATH. I've added sys.path.append(prefixpath) and os.environ['PYTHONPATH'] = prefixpath to mysite.fcgi, but if I set the enviornment variable to be empty on the command-line then run mysite.fcgi, I still get the above error. Here are some command-line results: >>> os.environ['PYTHONPATH'] = 'Null' >>> >>> os.system('echo $PYTHONPATH') Null >>> os.environ['PYTHONPATH'] = '/prefix/path' >>> >>> os.system('echo $PYTHONPATH') /prefix/path >>> exit() prompt$ echo $PYTHONPATH Null It looks like Python is setting the variable OK, but the variable is only applicable inside of the script. Flup appears to be distributed as an .egg file, and my guess is that the egg implementation doesn't take into account variables added by os.environ['key'] = value (?) at least when installing via the --prefix option. I'm not that familiar with .pth files, but it seems that the easy-install.pth file is the one that points to flup: import sys; sys.__plen = len(sys.path) ./setuptools-0.6c6-py2.5.egg ./flup-1.0.1-py2.5.egg import sys; new=sys.path[sys.__plen:]; del sys.path[sys.__plen:]; p=getattr(sys,'__egginsert',0); sy s.path[p:p]=new; sys.__egginsert = p+len(new) It looks like it's doing something funky, anyway to edit this or add something to my code so it will find flup?

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• Is Zend Framework a total waste of my time?

  - by Citizen

  Ok, I'm about 50% done with the "30 minute" quickstart guide from Zend. I must be missing something, because this seems like a total waste of time. The point of this quickguide is to create a guestbook, something I could do in 5 minutes with regular naked non-framework php. Here's my path to zend framework: c:/program files/wamp/www/_zend/ Here's my path to my quickstart project: c:/program files/wamp/www/_zend/bin/quickstart/ I have a number of questions at this point: http://framework.zend.com/docs/quickstart/create-a-model-and-database-table 1: I'm running the command line to run my database loading script. I get an error stating the it can't find the Zend/AutoLoader.php becuase my path to the zend library is wrong. I followed all of the steps. I defined the path to my zend library in the main config file, but for some reason, its defined again in my db loader. In all of these scripts that they have me load, it points the relative path to the zend library as being /../library Problem is, there's nothing in that folder. To get to my actual zend folder, you'd need to be (relatively) /../../../../library Which brings me to my 2nd question: 2: Where the #$#$ is the main Zend files supposed to be? The install directions were basically "put it wherever you want", when the real answer (after a bunch of errors and wasted time was) was "put it somewhere so that its really easy to type the full path a thousand times in command line" and "it also better be in a runnable place on your webserver since its going to create your quickstart application in a subdirectory within zend". Which brings us to the third question 3: Am I supposed to have this libary in both the parent core Zend (wamp/_zend/library) AND my application (quickstart/library)? 4: If that is the case, it seems like a ton of wasted files to be uploading. I'd like to use Zend to create products that my customers will download. 5 megs of overhead seems like a bit much. Zend claims you can use these library components separately, but it looks to me like I'm going to have to upload them every time. Which leads to the next question: 5: It appears that perhaps Zend is more for a single application that is not supposed to be distributed. Is this not the case? 6: According to their default file structure everything but my /public folder would be above public_html on my server if I wanted this to rest on my TLD. I would need to rename every reference of /public/ to /public_html/, or am I missing something else?

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• What is the best python module skeleton code?

  - by user213060

  == Subjective Question Warning == Looking for well supported opinions or supporting evidence. Let us assume that skeleton code can be good. If you disagree with the very concept of module skeleton code then fine, but please refrain from repeating that opinion here. Many python IDE's will start you with a template like: print 'hello world' That's not enough... So here's my skeleton code to get this question started: My Module Skeleton, Short Version: #!/usr/bin/env python """ Module Docstring """ # ## Code goes here. # def test(): """Testing Docstring""" pass if __name__=='__main__': test() and, My Module Skeleton, Long Version: #!/usr/bin/env python # -*- coding: ascii -*- """ Module Docstring Docstrings: http://www.python.org/dev/peps/pep-0257/ """ __author__ = 'Joe Author ([email protected])' __copyright__ = 'Copyright (c) 2009-2010 Joe Author' __license__ = 'New-style BSD' __vcs_id__ = '$Id$' __version__ = '1.2.3' #Versioning: http://www.python.org/dev/peps/pep-0386/ # ## Code goes here. # def test(): """ Testing Docstring""" pass if __name__=='__main__': test() Notes: """ ===MODULE TYPE=== Since the vast majority of my modules are "library" types, I have constructed this example skeleton as such. For modules that act as the main entry for running the full application, you would make changes such as running a main() function instead of the test() function in __main__. ===VERSIONING=== The following practice, specified in PEP8, no longer makes sense: __version__ = '$Revision: 1.2.3 $' for two reasons: (1) Distributed version control systems make it neccessary to include more than just a revision number. E.g. author name and revision number. (2) It's a revision number not a version number. Instead, the __vcs_id__ variable is being adopted. This expands to, for example: __vcs_id__ = '$Id: example.py,v 1.1.1.1 2001/07/21 22:14:04 goodger Exp $' ===VCS DATE=== Likewise, the date variable has been removed: __date__ = '$Date: 2009/01/02 20:19:18 $' ===CHARACTER ENCODING=== If the coding is explicitly specified, then it should be set to the default setting of ascii. This can be modified if necessary (rarely in practice). Defaulting to utf-8 can cause anomalies with editors that have poor unicode support. """ There are a lot of PEPs that put forward coding style recommendations. Am I missing any important best practices? What is the best python module skeleton code? Update Show me any kind of "best" that you prefer. Tell us what metrics you used to qualify "best".

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• Maven mercurial extension constantly fails

  - by TheLQ

  After 2+ hours I was able to get the maven-scm-provider-hg extension (for pushing to mercurial repos from Maven) semi working, meaning that it was executing commands instead of just giving errors. However I think I've run into a wall with this error [INFO] [deploy:deploy {execution: default-deploy}] [INFO] Retrieving previous build number from pircbotx.googlecode.com [INFO] Removing C:\DOCUME~1\Owner\LOCALS~1\Temp\wagon-scm1210107000.checkout\pir cbotx\pircbotx\1.3-SNAPSHOT [INFO] EXECUTING: cmd.exe /X /C "hg clone -r tip https://*SNIP*@site.pircbotx.googlecode.com/hg/maven2/snapshots/pircbotx/pircbotx/1.3-SNAPSHOT C:\DOCUME~1\Owner\LOCALS~1\Temp\wagon-scm1210107000.checkout\pircbotx\pircbotx\1.3-SNAPSHOT" [INFO] EXECUTING: cmd.exe /X /C "hg locate" [INFO] repository metadata for: 'snapshot pircbotx:pircbotx:1.3-SNAPSHOT' could not be found on repository: pircbotx.googlecode.com, so will be created Uploading: scm:hg:https://site.pircbotx.googlecode.com/hg/maven2/snapshots/pircbotx/pircbotx/1.3-SNAPSHOT/pircbotx-1.3-SNAPSHOT.jar [INFO] ------------------------------------------------------------------------ [ERROR] BUILD ERROR [INFO] ------------------------------------------------------------------------ [INFO] Error deploying artifact: Error listing repository: No such command 'list'. What on earth would cause that error? I'm on a Windows box, so any commands that aren't commands give "'list' is not recognized as an internal or external command...", not "No such command 'list'." POM <build> <extensions> <extension> <groupId>org.apache.maven.scm</groupId> <artifactId>maven-scm-provider-hg</artifactId> <version>1.4</version> </extension> <extension> <groupId>org.apache.maven.wagon</groupId> <artifactId>wagon-scm</artifactId> <version>1.0-beta-7</version> </extension> </extensions> ... <distributionManagement> <snapshotRepository> <id>pircbotx.googlecode.com</id> <name>PircBotX Site</name> <url>scm:hg:https://site.pircbotx.googlecode.com/hg/maven2/snapshots</url> <uniqueVersion>false</uniqueVersion> </snapshotRepository> </distributionManagement> Mercurial version W:\programming\pircbot-hg>hg version Mercurial Distributed SCM (version 1.7.2) Any suggestions?

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• Logging raw HTTP request/response in ASP.NET MVC & IIS7

  - by Greg Beech

  I'm writing a web service (using ASP.NET MVC) and for support purposes we'd like to be able to log the requests and response in as close as possible to the raw, on-the-wire format (i.e including HTTP method, path, all headers, and the body) into a database. What I'm not sure of is how to get hold of this data in the least 'mangled' way. I can re-constitute what I believe the request looks like by inspecting all the properties of the HttpRequest object and building a string from them (and similarly for the response) but I'd really like to get hold of the actual request/response data that's sent on the wire. I'm happy to use any interception mechanism such as filters, modules, etc. and the solution can be specific to IIS7. However, I'd prefer to keep it in managed code only. Any recommendations? Edit: I note that HttpRequest has a SaveAs method which can save the request to disk but this reconstructs the request from the internal state using a load of internal helper methods that cannot be accessed publicly (quite why this doesn't allow saving to a user-provided stream I don't know). So it's starting to look like I'll have to do my best to reconstruct the request/response text from the objects... groan. Edit 2: Please note that I said the whole request including method, path, headers etc. The current responses only look at the body streams which does not include this information. Edit 3: Does nobody read questions around here? Five answers so far and yet not one even hints at a way to get the whole raw on-the-wire request. Yes, I know I can capture the output streams and the headers and the URL and all that stuff from the request object. I already said that in the question, see: I can re-constitute what I believe the request looks like by inspecting all the properties of the HttpRequest object and building a string from them (and similarly for the response) but I'd really like to get hold of the actual request/response data that's sent on the wire. If you know the complete raw data (including headers, url, http method, etc.) simply cannot be retrieved then that would be useful to know. Similarly if you know how to get it all in the raw format (yes, I still mean including headers, url, http method, etc.) without having to reconstruct it, which is what I asked, then that would be very useful. But telling me that I can reconstruct it from the HttpRequest/HttpResponse objects is not useful. I know that. I already said it. Please note: Before anybody starts saying this is a bad idea, or will limit scalability, etc., we'll also be implementing throttling, sequential delivery, and anti-replay mechanisms in a distributed environment, so database logging is required anyway. I'm not looking for a discussion of whether this is a good idea, I'm looking for how it can be done.

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• .NET Application broken on one PC, unhandleable exception

  - by Bobby

  Hello people. I have a .NET 2.0 application with nothing fancy in it. It worked until yesterday on every PC I installed or copied it to, no matter if 2.0, 3.0, 3.5 or 3.5 SP1 was installed, no matter if it was Win2000, XP or even Win7 (in total 100+ machines). Yesterday I did my normal installation procedure and wanted to start it one time to check if everything is working...and it wasn't. The program crashed hard leaving me with the uninformative "Do you wanna report this error?" dialog. The problem is an exception in the Main(String[] args) routine of my application. The event viewer is showing the following entry: Event Type: ErrorEvent Source: .NET Runtime 2.0 Error Reporting Event Category: None Event ID: 5000 Date: 05/05/2010 Time: 16:09:09 User: N/A Computer: myClientPC Description: EventType clr20r3, P1 apomenu.exe, P2 1.4.90.53, P3 4bdedea4, P4 system.configuration, P5 2.0.0.0, P6 4889de74, P7 1a6, P8 136, P9 ioibmurhynrxkw0zxkyrvfn0boyyufow, P10 NIL. Well...great information. After a lot of searching I finally was able to get further information about this exception (by adding a handler for UnhandledExceptions directly in My.MyApplication.New(), Application.Designer.vb): System.Configuration.ConfigurationErrorsException Configuration system failed to initialize at System.Configuration.ClientConfigurationSystem.EnsureInit(String configKey) at System.Configuration.ClientConfigurationSystem.PrepareClientConfigSystem(String sectionName) at System.Configuration.ClientConfigurationSystem.System.Configuration.Internal.IInternalConfigSystem.GetSection(String sectionName) at System.Configuration.ConfigurationManager.GetSection(String sectionName) at System.Configuration.PrivilegedConfigurationManager.GetSection(String sectionName) at System.Net.Configuration.SettingsSectionInternal.get_Section() at System.Net.Sockets.Socket.InitializeSockets() at System.Net.Sockets.Socket.get_SupportsIPv4() at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.get_HostName() at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.RegisterChannel(Boolean SecureChannel) at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.Run(String[] commandLine) at MyAppNameHere.My.MyApplication.Main(String[] Args) in 17d14f5c-a337-4978-8281-53493378c1071.vb:Line 81. And at this point I'm stuck...I'm out of ideas. I'm not using any kind of configuration system from the framework (no reference to System.Configuration, and there never was a MyAppnameHere.exe.config generated or distributed, nor have I seen this error before). I also found a bug report at Microsoft (Google Cache) about this bug (in another context, though). But as it seems, they won't even look at it. Every help is greatly appreciated! Edit: I'm using Visual Studio 2008 Prof.. Crash happens in Release- and Debug-Build on the client machine. Debugging the application directly on this machine is out of question I fear, 300+ Miles and they only have two computers to work with.

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• What's the best way to do base36 arithmetic in perl?

  - by DVK

  What's the best way to do base36 arithmetic in Perl? To be more specific, I need to be able to do the following: Operate on positive N-digit numbers in base 36 (e.g. digits are 0-9 A-Z) N is finite, say 9 Provide basic arithmetic, at the very least the following 3: Addition (A+B) Subtraction (A-B) Whole division, e.g. floor(A/B). Strictly speaking, I don't really need a base10 conversion ability - the numbers will 100% of time be in base36. So I'm quite OK if the solution does NOT implement conversion from base36 back to base10 and vice versa. I don't much care whether the solution is brute-force "convert to base 10 and back" or converting to binary, or some more elegant approach "natively" performing baseN operations (as stated above, to/from base10 conversion is not a requirement). My only 3 considerations are: It fits the minimum specifications above It's "standard". Currently we're using and old homegrown module based on base10 conversion done by hand that is buggy and sucks. I'd much rather replace that with some commonly used CPAN solution instead of re-writing my own bicycle from scratch, but I'm perfectly capable of building it if no better standard possibility exists. It must be fast-ish (though not lightning fast). Something that takes 1 second to sum up 2 9-digit base36 numbers is worse than anything I can roll on my own :) P.S. Just to provide some context in case people decide to solve my XY problem for me in addition to answering the technical question above :) We have a fairly large tree (stored in DB as a bunch of edges), and we need to superimpose order on a subset of that tree. The tree dimentions are big both depth- and breadth- wise. The tree is VERY actively updated (inserts and deletes and branch moves). This is currently done by having a second table with 3 columns: parent_vertex, child_vertex, local_order, where local_order is an 9-character string built of A-Z0-9 (e.g. base 36 number). Additional considerations: It is required that the local order is unique per child (and obviously unique per parent), Any complete re-ordering of a parent is somewhat expensive, and thus the implementation is to try and assign - for a parent with X children - the orders which are somewhat evenly distributed between 0 and 36**10-1, so that almost no tree inserts result in a full re-ordering.

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• Coming Up with a Good Algorithm for a Simple Idea

  - by mkoryak

  I need to come up with an algorithm that does the following: Lets say you have an array of positive numbers (e.g. [1,3,7,0,0,9]) and you know beforehand their sum is 20. You want to abstract some average amount from each number such that the new sum would be less by 7. To do so, you must follow these rules: you can only subtract integers the resulting array must not have any negative values you can not make any changes to the indices of the buckets. The more uniformly the subtraction is distributed over the array the better. Here is my attempt at an algorithm in JavaScript + underscore (which will probably make it n^2): function distributeSubtraction(array, goal){ var sum = _.reduce(arr, function(x, y) { return x + y; }, 0); if(goal < sum){ while(goal < sum && goal > 0){ var less = ~~(goal / _.filter(arr, _.identity).length); //length of array without 0s arr = _.map(arr, function(val){ if(less > 0){ return (less < val) ? val - less : val; //not ideal, im skipping some! } else { if(goal > 0){ //again not ideal. giving preference to start of array if(val > 0) { goal--; return val - 1; } } else { return val; } } }); if(goal > 0){ var newSum = _.reduce(arr, function(x, y) { return x + y; }, 0); goal -= sum - newSum; sum = newSum; } else { return arr; } } } else if(goal == sum) { return _.map(arr, function(){ return 0; }); } else { return arr; } } var goal = 7; var arr = [1,3,7,0,0,9]; var newArray = distributeSubtraction(arr, goal); //returned: [0, 1, 5, 0, 0, 7]; Well, that works but there must be a better way! I imagine the run time of this thing will be terrible with bigger arrays and bigger numbers. edit: I want to clarify that this question is purely academic. Think of it like an interview question where you whiteboard something and the interviewer asks you how your algorithm would behave on a different type of a dataset.

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• How to split HTML code with javascript or JQuery

  - by Dean

  Hi I'm making a website using JSP and servlets and I have to now break up a list of radio buttons to insert a textarea and a button. I have got the button and textarea to hide and show when you click on the radio button it shows the text area and button. But this only appears at the top and when there are hundreds on the page this will become awkward so i need a way for it to appear underneath. Here is what my HTML looks like when complied: <form action="addSpotlight" method="POST"> <table> <tr><td><input type="radio" value="29" name="publicationIDs" ></td><td>A System For Dynamic Server Allocation in Application Server Clusters, IEEE International Symposium on Parallel and Distributed Processsing with Applications, 2008</td> </tr> <tr><td><input type="radio" value="30" name="publicationIDs" ></td><td>Analysing BitTorrent's Seeding Strategies, 7th IEEE/IFIP International Conference on Embedded and Ubiquitous Computing (EUC-09), 2009</td> </tr> <tr><td><input type="radio" value="31" name="publicationIDs" ></td><td>The Effect of Server Reallocation Time in Dynamic Resource Allocation, UK Performance Engineering Workshop 2009, 2009</td> </tr> <tr><td><input type="radio" value="32" name="publicationIDs" ></td><td>idk, hello, 1992</td> </tr> <tr><td><input type="radio" value="33" name="publicationIDs" ></td><td>sad, safg, 1992</td> </tr> <div class="abstractWriteup"><textarea name="abstract"></textarea> <input type="submit" value="Add Spotlight"></div> </table> </form> Now here is what my JSP looks like: <form action="addSpotlight" method="POST"> <table> <%int i = 0; while(i<ids.size()){%> <tr><td><input type="radio" value="<%=ids.get(i)%>" name="publicationIDs" ></td><td><%=info.get(i)%></td> </tr> <%i++; }%> <div class="abstractWriteup"><textarea name="abstract"></textarea> <input type="submit" value="Add Spotlight"></div> </table> </form> Thanks in Advance Dean

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• jQuery multiple running totals

  - by Benjamin Randal

  0I am using jQuery to calculate a running total on multiple textboxes. Just found an awesome response on how to get that working a few days ago, but now I am running into another problem. When using one selector, the total for GetTotal is calculated perfectly. However, when I include the second selector, the totals begin to conflict with one another, and no longer calculate properly. I have been searching for a solution to this for some time now, does anyone have any ideas? Here is the selector i am currently using: function GetTotal(txtBox) { var total = 0; $('input:text').each(function(index, value) { total += parseInt($(value).val() || 0); }); $("#chkTotal").html(total); } My view uses these txt boxes <div class="editor-field"> @Html.TextBox("Field1", String.Empty, new {InputType = "text", id = "field1", onchange = "GetTotal(this)" }) </div> <div class="editor-field"> @Html.TextBox("Field2", String.Empty, new {InputType = "text", id = "field2", onchange = "GetTotal(this)" }) </div> <div> <h3>Total Checked</h3> </div> <div id="chkTotal"></div> Now I am trying to implement another selector which will total two additional editor fields... function GetTotal1(txtBox) { var total1 = 0; $('input:text').each(function (index, value) { total1 += parseInt($(value).val() || 0); }); $("#disTotal").html(total1); } View: <div class="editor-field"> @Html.TextBox("Field3", String.Empty, new {InputType = "text", id = "field3", onchange = "GetTotal1(this)" }) </div> <div class="editor-field"> @Html.TextBox("Field4", String.Empty, new {InputType = "text", id = "field4", onchange = "GetTotal1(this)" }) </div> <div> <h3>Total Distributed</h3> </div> <div id="disTotal"></div>

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• Is this scenario in compliance with GPLv3?

  - by Sean Kinsey

  For arguments sake, say that we create a web application , that depends on a GPLv3 licensed component, lets say Ext JS. Based on Section 0 of the license, the common notion is that the entire web application (the client side javascript) falls under the definition of a covered work: A “covered work” means either the unmodified Program or a work based on the Program. and that it will therefor have to be distributed under the same license Ok, so here comes the fun part: This is a short 'program' that is based on Ext JS var myPanel = new Ext.Panel(); The question that arises is: Have I now violated the GPL by not including the source of Ext JS and its license? Ok, so lets take another example <!doctype html> <html> <head> <title>my title</title> <script type="text/javascript" src="http://extjs.cachefly.net/ext-3.2.1/ext-all.js"> </script> <link rel="stylesheet" type="text/css" href="http://extjs.cachefly.net/ext-3.2.1/resources/css/ext-all.css" /> <script type="text/javascript"> var myPanel = new Ext.Panel(); </script> </head> <body> </body> </html> Have I now violated the terms of the GPL? The code conveyed by me to you is in a non-functional state - it will have to be combined with the actual source of Ext JS, which you(your browser) will have to retrieve, from a source made public by someone else to be usable. Now, if the answer to the above is no, how does me conveying this code in visible form differ from the 'invisible' form conveyed by my web server? As a side note, a very similar thing is done in Linux with many projects that depends on less permissive licenses - the user has to retrieve these on its own and make these available for the primary lib/executable. How is this not the same if the user is informed on beforehand that he (the browser) will have to retrieve the needed resources from a different source? Just to make it clear, I'm pro FLOSS, and I have also published a number of projects licensed under more permissive licenses. The reason I'm asking this is that I still haven't found anyone offering a definitive answer to this.

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• Segmenting a double array of labels

  - by Ami

  The Problem: I have a large double array populated with various labels. Each element (cell) in the double array contains a set of labels and some elements in the double array may be empty. I need an algorithm to cluster elements in the double array into discrete segments. A segment is defined as a set of pixels that are adjacent within the double array and one label that all those pixels in the segment have in common. (Diagonal adjacency doesn't count and I'm not clustering empty cells). |-------|-------|------| | Jane | Joe | | | Jack | Jane | | |-------|-------|------| | Jane | Jane | | | | Joe | | |-------|-------|------| | | Jack | Jane | | | Joe | | |-------|-------|------| In the above arrangement of labels distributed over nine elements, the largest cluster is the “Jane” cluster occupying the four upper left cells. What I've Considered: I've considered iterating through every label of every cell in the double array and testing to see if the cell-label combination under inspection can be associated with a preexisting segment. If the element under inspection cannot be associated with a preexisting segment it becomes the first member of a new segment. If the label/cell combination can be associated with a preexisting segment it associates. Of course, to make this method reasonable I'd have to implement an elaborate hashing system. I'd have to keep track of all the cell-label combinations that stand adjacent to preexisting segments and are in the path of the incrementing indices that are iterating through the double array. This hash method would avoid having to iterate through every pixel in every preexisting segment to find an adjacency. Why I Don't Like it: As is, the above algorithm doesn't take into consideration the case where an element in the double array can be associated with two unique segments, one in the horizontal direction and one in the vertical direction. To handle these cases properly, I would need to implement a test for this specific case and then implement a method that will both associate the element under inspection with a segment and then concatenate the two adjacent identical segments. On the whole, this method and the intricate hashing system that it would require feels very inelegant. Additionally, I really only care about finding the large segments in the double array and I'm much more concerned with the speed of this algorithm than with the accuracy of the segmentation, so I'm looking for a better way. I assume there is some stochastic method for doing this that I haven't thought of. Any suggestions?

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• Under what circumstances is an SqlConnection automatically enlisted in an ambient TransactionScope T

  - by Triynko

  What does it mean for an SqlConnection to be "enlisted" in a transaction? Does it simply mean that commands I execute on the connection will participate in the transaction? If so, under what circumstances is an SqlConnection automatically enlisted in an ambient TransactionScope Transaction? See questions in code comments. My guess to each question's answer follows each question in parenthesis. Scenario 1: Opening connections INSIDE a transaction scope using (TransactionScope scope = new TransactionScope()) using (SqlConnection conn = ConnectToDB()) { // Q1: Is connection automatically enlisted in transaction? (Yes?) // // Q2: If I open (and run commands on) a second connection now, // with an identical connection string, // what, if any, is the relationship of this second connection to the first? // // Q3: Will this second connection's automatic enlistment // in the current transaction scope cause the transaction to be // escalated to a distributed transaction? (Yes?) } Scenario 2: Using connections INSIDE a transaction scope that were opened OUTSIDE of it //Assume no ambient transaction active now SqlConnection new_or_existing_connection = ConnectToDB(); //or passed in as method parameter using (TransactionScope scope = new TransactionScope()) { // Connection was opened before transaction scope was created // Q4: If I start executing commands on the connection now, // will it automatically become enlisted in the current transaction scope? (No?) // // Q5: If not enlisted, will commands I execute on the connection now // participate in the ambient transaction? (No?) // // Q6: If commands on this connection are // not participating in the current transaction, will they be committed // even if rollback the current transaction scope? (Yes?) // // If my thoughts are correct, all of the above is disturbing, // because it would look like I'm executing commands // in a transaction scope, when in fact I'm not at all, // until I do the following... // // Now enlisting existing connection in current transaction conn.EnlistTransaction( Transaction.Current ); // // Q7: Does the above method explicitly enlist the pre-existing connection // in the current ambient transaction, so that commands I // execute on the connection now participate in the // ambient transaction? (Yes?) // // Q8: If the existing connection was already enlisted in a transaction // when I called the above method, what would happen? Might an error be thrown? (Probably?) // // Q9: If the existing connection was already enlisted in a transaction // and I did NOT call the above method to enlist it, would any commands // I execute on it participate in it's existing transaction rather than // the current transaction scope. (Yes?) }

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• With EJB 2.1, is declaring references to resources in ejb-jar.xml required?

  - by zwerd328

  I'm using Weblogic 9.2 with a lot of MDBs. These MDBs access JDBC DataSources and write to both locally and externally managed JMS Destinations using local and foreign XAConnectionFactorys, respectively. Each MDB demarcates a container-managed JTA transaction that should be distributed amongst all of these resources. Below is an excerpt from my ejb-jar.xml for an MDB that consumes from a local Queue called "MyDestination" and produces to an IBM Websphere MQ Queue called "MyOtherDestination". These logical names are linked to physical objects in my weblogic-ejb-jar.xml file. Is it required to use the <resource-ref> and <message-destination-ref> tags to expose the ConnectionFactory and Queue to the MDB? If so, is it required by Weblogic or is it required by the J2EE spec? And for what purpose? For example, is it required to support XA transactionality? I'm already aware of the benefit of decoupling the administered objects from my MDB using names exposed to the naming context of the MDB. Is this the only value added when specifying these tags? In other words, is it acceptable to just reference these objects from my MDB using the InitialContext and the objects' fully-qualified names? <enterprise-bean> <message-driven> <ejb-name>MyMDB</ejb-name> <ejb-class>com.mycompany.MyMessageDrivenBean</ejb-class> <transaction-type>Container</transaction-type> <message-destination-type>javax.jms.Queue</message-destination> <message-destination-link>MyDestination</message-destination-link> <resource-ref> <res-ref-name>jms/myQCF</res-ref-name> <res-type>javax.jms.XAConnectionFactory</res-type> <res-auth>Container</res-auth> </resource-ref> <message-destination-ref> <message-destination-ref-name>jms/myOtherDestination</message-destination-ref-name> <message-destination-type>javax.jms.Queue</message-destination-type> <message-destination-usage>Produces</message-destination-usage> <message-destination-link>MyOtherDestination</message-destination-link> </message-destination-ref> </message-driven> <enterprise-bean>

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• The best way to separate admin functionality from a public site?

  - by AndrewO

  I'm working on a site that's grown both in terms of user-base and functionality to the point where it's becoming evident that some of the admin tasks should be separate from the public website. I was wondering what the best way to do this would be. For example, the site has a large social component to it, and a public sales interface. But at the same time, there's back office tasks, bulk upload processing, dashboards (with long running queries), and customer relations tools in the admin section that I would like to not be effected by spikes in public traffic (or effect the public-facing response time). The site is running on a fairly standard Rails/MySQL/Linux stack, but I think this is more of an architecture problem than an implementation one: mainly, how does one keep the data and business logic in sync between these different applications? Some strategies that I'm evaluating: 1) Create a slave database of the public facing database on another machine. Extract out all of the model and library code so that it can be shared between the applications. Create new controllers and views for the admin interfaces. I have limited experience with replication and am not even sure that it's supposed to be used this way (most of the time I've seen it, it's been for scaling out the read capabilities of the same application, rather than having multiple different ones). I'm also worried about the potential for latency issues if the slave is not on the same network. 2) Create new more task/department-specific applications and use a message oriented middleware to integrate them. I read Enterprise Integration Patterns awhile back and they seemed to advocate this for distributed systems. (Alternatively, in some cases the basic Rails-style RESTful API functionality might suffice.) But, I have nightmares about data synchronization issues and the massive re-architecting that this would entail. 3) Some mixture of the two. For example, the only public information necessary for some of the back office tasks is a read-only completion time or status. Would it make sense to have that on a completely separate system and send the data to public? Meanwhile, the user/group admin functionality would be run on a separate system sharing the database? The downside is, this seems to keep many of the concerns I have with the first two, especially the re-architecting. I'm sure the answers are going to be highly dependent on a site's specific needs, but I'd love to hear success (or failure) stories.

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• Akka framework support for finding duplicate messages

  - by scala_is_awesome

  I'm trying to build a high-performance distributed system with Akka and Scala. If a message requesting an expensive (and side-effect-free) computation arrives, and the exact same computation has already been requested before, I want to avoid computing the result again. If the computation requested previously has already completed and the result is available, I can cache it and re-use it. However, the time window in which duplicate computation can be requested may be arbitrarily small. e.g. I could get a thousand or a million messages requesting the same expensive computation at the same instant for all practical purposes. There is a commercial product called Gigaspaces that supposedly handles this situation. However there seems to be no framework support for dealing with duplicate work requests in Akka at the moment. Given that the Akka framework already has access to all the messages being routed through the framework, it seems that a framework solution could make a lot of sense here. Here is what I am proposing for the Akka framework to do: 1. Create a trait to indicate a type of messages (say, "ExpensiveComputation" or something similar) that are to be subject to the following caching approach. 2. Smartly (hashing etc.) identify identical messages received by (the same or different) actors within a user-configurable time window. Other options: select a maximum buffer size of memory to be used for this purpose, subject to (say LRU) replacement etc. Akka can also choose to cache only the results of messages that were expensive to process; the messages that took very little time to process can be re-processed again if needed; no need to waste precious buffer space caching them and their results. 3. When identical messages (received within that time window, possibly "at the same time instant") are identified, avoid unnecessary duplicate computations. The framework would do this automatically, and essentially, the duplicate messages would never get received by a new actor for processing; they would silently vanish and the result from processing it once (whether that computation was already done in the past, or ongoing right then) would get sent to all appropriate recipients (immediately if already available, and upon completion of the computation if not). Note that messages should be considered identical even if the "reply" fields are different, as long as the semantics/computations they represent are identical in every other respect. Also note that the computation should be purely functional, i.e. free from side-effects, for the caching optimization suggested to work and not change the program semantics at all. If what I am suggesting is not compatible with the Akka way of doing things, and/or if you see some strong reasons why this is a very bad idea, please let me know. Thanks, Is Awesome, Scala

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• Technical non-terminating condition in a loop

  - by Snarfblam

  Most of us know that a loop should not have a non-terminating condition. For example, this C# loop has a non-terminating condition: any even value of i. This is an obvious logic error. void CountByTwosStartingAt(byte i) { // If i is even, it never exceeds 254 for(; i < 255; i += 2) { Console.WriteLine(i); } } Sometimes there are edge cases that are extremely unlikeley, but technically constitute non-exiting conditions (stack overflows and out-of-memory errors aside). Suppose you have a function that counts the number of sequential zeros in a stream: int CountZeros(Stream s) { int total = 0; while(s.ReadByte() == 0) total++; return total; } Now, suppose you feed it this thing: class InfiniteEmptyStream:Stream { // ... Other members ... public override int Read(byte[] buffer, int offset, int count) { Array.Clear(buffer, offset, count); // Output zeros return count; // Never returns -1 (end of stream) } } Or more realistically, maybe a stream that returns data from external hardware, which in certain cases might return lots of zeros (such as a game controller sitting on your desk). Either way we have an infinite loop. This particular non-terminating condition stands out, but sometimes they don't. A completely real-world example as in an app I'm writing. An endless stream of zeros will be deserialized into infinite "empty" objects (until the collection class or GC throws an exception because I've exceeded two billion items). But this would be a completely unexpected circumstance (considering my data source). How important is it to have absolutely no non-terminating conditions? How much does this affect "robustness?" Does it matter if they are only "theoretically" non-terminating (is it okay if an exception represents an implicit terminating condition)? Does it matter whether the app is commercial? If it is publicly distributed? Does it matter if the problematic code is in no way accessible through a public interface/API? Edit: One of the primary concerns I have is unforseen logic errors that can create the non-terminating condition. If, as a rule, you ensure there are no non-terminating conditions, you can identify or handle these logic errors more gracefully, but is it worth it? And when? This is a concern orthogonal to trust.

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• Can I have a workspace that is both a git workspace and a svn workspace?

  - by Troy

  I have checked out now a local working copy of a codebase that lives in an svn repo. It's a big Java project that I use Eclipse to develop in. Eclipse of course builds everything on the fly, in it's own way with all the binaries ending up in [project root]/bin. That's perfectly fine with me, for development, but when the build runs on the build server, it looks quite a lot different (maven build, binaries end up in a different directory structure, etc). Sometimes I need to recreate the build server environment on my local development system to debug the build or what have you, so I usually end up downloading an entirely new working copy into a new workspace and running the build from there (prevents cluttering my development workspace with all the build artifacts and dirtying up the working copy). Of course sometimes I'm interested in running the full build on code that I don't want to check in yet, so I will manually copy over the "development" workspace onto the "build" workspace. Besides taking a lot of extra time copying a lot of files that I don't actually need (just overlaying the new over the old), this also screws up my svn metadata, meaning that I can't check in changes from that "build workspace" working copy, and I often end up having to re-download the code to get it back into a known state. So I'm thinking I make my svn working copy a local git repo, then "check out" the in-development code from the svn working copy/git master, into the local build workspace. Then I can build, revert my changes, have all the advantages of a version controlled working copy in the build workspace. Then if I need to make changes to the build, push those back into the git master (which is also a svn working copy), then check them into the main svn repo. |-------------| |main svn repo| <------- |---------------------| |-------------| |svn working copy | <------- |--------------------| | (svn dev workspace/ | | non-svn-versioned | | git master) | | build workspace | |---------------------| | (git working copy) | |--------------------| Just switching everything to git would obviously be better, but, big company, too many people using svn, too costly to change everything, etc. We're stuck with svn as the main repo for now. BTW, I know there is a maven plugin for Eclipse and everything, I'm mainly interested to know if there is a way to maintain a workspace that is both a git working copy and an svn working copy. Actually any distributed version control system would probably work (hg possibly?). Advice? How does everybody else handle this situation of having a to manage both a "development" build process and a "production" build process?

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• organizing external libraries and include files

  - by stijn

  Over the years my projects use more and more external libraries, and the way I did it starts feeling more and more awkward (although, that has to be said, it does work flawlessly). I use VS on Windows, CMake on others, and CodeComposer for targetting DSPs on Windows. Except for the DSPs, both 32bit and 64bit platforms are used. Here's a sample of what I am doing now; note that as shown, the different external libraries themselves are not always organized in the same way. Some have different lib/include/src folders, others have a single src folder. Some came ready-to-use with static and/or shared libraries, others were built /path/to/projects /projectA /projectB /path/to/apis /apiA /src /include /lib /apiB /include /i386/lib /amd64/lib /path/to/otherapis /apiC /src /path/to/sharedlibs /apiA_x86.lib -->some libs were built in all possible configurations /apiA_x86d.lib /apiA_x64.lib /apiA_x64d.lib /apiA_static_x86.lib /apiB.lib -->other libs have just one import library /path/to/dlls -->most of this directory also gets distributed to clients /apiA_x86.dll and it's in the PATH /apiB.dll Each time I add an external libary, I roughly use this process: build it, if needed, for different configurations (release/debug/platform) copy it's static and/or import libraries to 'sharedlibs' copy it's shared libraries to 'dlls' add an environment variable, eg 'API_A_DIR' that points to the root for ApiA, like '/path/to/apis/apiA' create a VS property sheet and a CMake file to state include path and eventually the library name, like include = '$(API_A_DIR)/Include' and lib = apiA.lib add the propertysheet/cmake file to the project needing the library It's especially step 4 and 5 that are bothering me. I am pretty sure I am not the only one facing this problem, and would like see how others deal with this. I was thinking to get rid of the environment variables per library, and use just one 'API_INCLUDE_DIR' and populating it with the include files in an organized way: /path/to/api/include /apiA /apiB /apiC This way I do not need the include path in the propertysheets nor the environment variables. For libs that are only used on windows I even don't need a propertysheet at all as I can use #pragmas to instruct the linker what library to link to. Also in the code it will be more clear what gets included, and no need for wrappers to include files having the same name but are from different libraries: #include <apiA/header.h> #include <apiB/header.h> #include <apiC_version1/header.h> The withdrawal is off course that I have to copy include files, and possibly** introduce duplicates on the filesystem, but that looks like a minor price to pay, doesn't it? ** actually once libraries are built, the only thing I need from them is the include files and thie libs. Since each of those would have a dedicated directory, the original source tree is not needed anymore so can be deleted..

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• Achieving C# "readonly" behavior in C++

  - by Tommy Fisk

  Hi guys, this is my first question on stack overflow, so be gentle. Let me first explain the exact behavior I would like to see. If you are familiar with C# then you know that declaring a variable as "readonly" allows a programmer to assign some value to that variable exactly once. Further attempts to modify the variable will result in an error. What I am after: I want to make sure that any and all single-ton classes I define can be predictably instantiated exactly once in my program (more details at the bottom). My approach to realizing my goal is to use extern to declare a global reference to the single-ton (which I will later instantiate at a time I choose. What I have sort of looks like this, namespace Global { extern Singleton& mainInstance; // not defined yet, but it will be later! } int main() { // now that the program has started, go ahead and create the singleton object Singleton& Global::mainInstance = Singleton::GetInstance(); // invalid use of qualified name Global::mainInstance = Singleton::GetInstance(); // doesn't work either :( } class Singleton { /* Some details ommited */ public: Singleton& GetInstance() { static Singleton instance; // exists once for the whole program return instance; } } However this does not really work, and I don't know where to go from here. Some details about what I'm up against: I'm concerned about threading as I am working on code that will deal with game logic while communicating with several third-party processes and other processes I will create. Eventually I would have to implement some kind of synchronization so multiple threads could access the information in the Singleton class without worry. Because I don't know what kinds of optimizations I might like to do, or exactly what threading entails (never done a real project using it), I was thinking that being able to predictably control when Singletons were instantiated would be a Good Thing. Imagine if Process A creates Process B, where B contains several Singletons distributed against multiple files and/or libraries. It could be a real nightmare if I can not reliably ensure the order these singleton objects are instantiated (because they could depend on each other, and calling methods on a NULL object is generally a Bad Thing). If I were in C# I would just use the readonly keyword, but is there any way I can implement this (compiler supported) behavior in C++? Is this even a good idea? Thanks for any feedback.

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• Hosting a subversion working copy in an remote WebDAV folder

  - by Daniel Baulig

  This might be a bit awkward, but I'll try to explain what I am trying to achieve and what problems I encountered. First of all: whats this about? I am currently trying to set up a distributed working enviroment for developing a web page. My plan was to setup a SVN repository for version control, a live server where the actual live page ist hosted and a development server where I can work on the page. To ease things I intended to not have a local copy of the project on my disk, but to actually work directy on the files, that the development server hosts. For that I setup a WebDAV directory, under devserver.com/workspace, that actually mapped to files served under devserver.com/. So I could connect to devserver.com/workspace, change something and view the results live at devserver.com/. So far this worked perfectly. The next step was to create a SVN repository that would take care of my version control. I intended to be able to checkin to the reposiroty from my development server and at any time, with a small shell script, deploy any revision from the svn to the live server by checking out a copy of the revision into the live server directories. The second part, checking out into the live server, also worked perfectly. The first part though is where problems arose: My workstation is a Windows 7 machine. I connected to the WebDAV share using Windows built-in WebDAV support, which worked quite well. I can create, move, delete, edit, whatever files on my WebDAV share from my Windows machine perfectly. The next step was to checkout a working copy from the SVN (actually hosted at devserver.com/subversion/) into the WebDAV share. In the first try I used the Eclipse plugin subversive. The actual checkout worked fine and I can update and commit stuff to the repository, however, I cannot add any files to the ignore list. It always brings me an error. So I tried the same thing with a complete fresh repository using TortoiseSVN - and again it failed with the same errors. Here is what it says when trying to add files to svnignore: Some of selected resources were not added to ignore. svn: Cannot rename file '\\devserver.com@SSL\DavWWWRoot\workspace\.svn\tmp\dir-props.66fd8936-2701-0010-bb76-472f0b56a5d1.tmp' to '\\devserver.com@SSL\DavWWWRoot\workspace\.svn\tmp\dir-props' This is what apache2 tells me, when I try to add a file to svnignore: [Sun Mar 07 03:54:19 2010] [error] [client xxx.xxx.xxx.xxx] Negotiation: discovered file(s) matching request: /var/www/devserver.com/.svn/tmp/dir-props (None could be negotiated). [Sun Mar 07 03:54:31 2010] [error] [client xxx.xxx.xxx.xxx] (20)Not a directory: The URL contains extraneous path components. The resource could not be identified. [400, #0] Actually both messages are repeated several times. The first one occurs first and is repeated about 5 times and the second comes there after and is repeated propably more than 20 times. If I create a regular file, delete, rename or modify it none of those messages appear in my error.log While writing this question now I was able to add fils to svnignore using TortoiseSVN. However, after that, Eclipse would not let me commit anymore. The error that used to pop up when adding files to svnignore now also shows up while commiting. While searching the web I found some people having this same message appearing because they had files only different in upper- / lower-case naming. I checked my repository and did not find such files. I also read somewhere about people having troubles with WebDAV and file locking, because WebDAV's file locking capabilities seem to be very limited. At some stage I got errors telling me my repository was locked and thus the operations could not be completed. This error though did not appear anymore, since I setup a completely fresh repository and working copy. I would really appreciate any help anyone can provide me in fixing this problem! If there are any more questions feel free to ask. I know this is a somewhat unusual setup. Best regards, Daniel

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• Oracle performance problem

  - by jreid42

  We are using an Oracle 11G machine that is very powerful; has redundant storage etc. It's a beast from what I have been told. We just got this DB for a tool that when I first came on as a coop had like 20 people using, now its upwards of 150 people. I am the only one working on it :( We currently have a system in place that distributes PERL scripts across our entire data center essentially giving us a sort of "grid" computing power. The Perl scripts run a sort of simulation and report back the results to the database. They do selects / inserts. The load is not very high for each script but it could be happening across 20-50 systems at the same time. We then have multiple data centers and users all hitting the same database with this same approach. Our main problem with this is that our database is getting overloaded with connections and having to drop some. We sometimes have upwards of 500 connections. These are old perl scripts and they do not handle this well. Essentially they fail and the results are lost. I would rather avoid having to rewrite a lot of these as they are poorly written, and are a headache to even look at. The database itself is not overloaded, just the connection overhead is too high. We open a connection, make a quick query and then drop the connection. Very short connections but many of them. The database team has basically said we need to lower the number of connections or they are going to ignore us. Because this is distributed across our farm we cant implement persistent connections. I do this with our webserver; but its on a fixed system. The other ones are perl scripts that get opened and closed by the distribution tool and thus arent always running. What would be my best approach to resolving this issue? The scripts themselves can wait for a connection to be open. They do not need to act immediately. Some sort of queing system? I've been suggested to set up a few instances of a tool called "SQL Relay". Maybe one in each data center. How reliable is this tool? How good is this approach? Would it work for what we need? We could have one for each data center and relay requests through it to our main database, keeping a pipeline of open persistent connections? Does this make sense? Is there any other suggestions you can make? Any ideas? Any help would be greatly appreciated. Sadly I am just a coop student working for a very big company and somehow all of this has landed all on my shoulders (there is literally nobody to ask for help; its a hardware company, everybody is hardware engineers, and the database team is useless and in India) and I am quite lost as what the best approach would be? I am extremely overworked and this problem is interfering with on going progress and basically needs to be resolved as quickly as possible; preferably without rewriting the whole system, purchasing hardware (not gonna happen), or shooting myself in the foot. HELP LOL!

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• disk-to-disk backup without costly backup redundancy?

  - by AaronLS

  A good backup strategy involves a combination of 1) disconnected backups/snapshots that will not be affected by bugs, viruses, and/or security breaches 2) geographically distributed backups to protect against local disasters 3) testing backups to ensure that they can be restored as needed Generally I take an onsite backup daily, and an offsite backup weekly, and do test restores periodically. In the rare circumstance that I need to restore files, I do some from the local backup. Should a catastrophic event destroy the servers and local backups, then the offsite weekly tape backup would be used to restore the files. I don't need multiple offsite backups with redundancy. I ALREADY HAVE REDUNDANCY THROUGH THE USE OF BOTH LOCAL AND REMOTE BACKUPS. I have recovery blocks and par files with the backups, so I already have protection against a small percentage of corrupt bits. I perform test restores to ensure the backups function properly. Should the remote backups experience a dataloss, I can replace them with one of the local backups. There are historical offsite backups as well, so if a dataloss was not noticed for a few weeks(such as a bug/security breach/virus), the data could be restored from an older backup. By doing this, the only scenario that poses a risk to complete data loss would be one where both the local, remote, and servers all experienced a data loss in the same time period. I'm willing to risk that happening since the odds of that trifecta negligibly small, and the data isn't THAT valuable to me. So I hope I have emphasized that I don't need redundancy in my offsite backups because I have covered all the bases. I know this exact technique is employed by numerous businesses. Of course there are some that take multiple offsite backups, because the data is so incredibly valuable that they don't even want to risk that trifecta disaster, but in the majority of cases the trifecta disaster is an accepted risk. I HAD TO COVER ALL THIS BECAUSE SOME PEOPLE DON'T READ!!! I think I have justified my backup strategy and the majority of businesses who use offsite tape backups do not have any additional redundancy beyond what is mentioned above(recovery blocks, par files, historical snapshots). Now I would like to eliminate the use of tapes for offsite backups, and instead use a backup service. Most however are extremely costly for $/gb/month storage. I don't mind paying for transfer bandwidth, but the cost of storage is way to high. All of them advertise that they maintain backups of the data, and I imagine they use RAID as well. Obviously if you were using them to host servers this would all be necessary, but for my scenario, I am simply replacing my offsite backups with such a service. So there is no need for RAID, and absolutely no value in another layer of backups of backups. My one and only question: "Are there online data-storage/backup services that do not use redundancy or offer backups(backups of my backups) as part of their packages, and thus are more reasonably priced?" NOT my question: "Is this a flawed strategy?" I don't care if you think this is a good strategy or not. I know it pretty standard. Very few people make an extra copy of their offsite backups. They already have local backups that they can use to replace the remote backups if something catastrophic happens at the remote site. Please limit your responses to the question posed. Sorry if I seem a little abrasive, but I had some trolls in my last post who didn't read my requirements nor my question, and were trying to go off answering a totally different question. I made it pretty clear, but didn't try to justify my strategy, because I didn't ask about whether my strategy was justifyable. So I apologize if this was lengthy, as it really didn't need to be, but since there are so many trolls here who try to sidetrack questions by responding without addressing the question at hand.

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