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• Is it possible to write map/reduce jobs for Amazon Elastic MapReduce using .NET?

  - by Chris

  Is it possible to write map/reduce jobs for Amazon Elastic MapReduce (http://aws.amazon.com/elasticmapreduce/) using .NET languages? In particular I would like to use C#. Preliminary research suggests not. The above URL's marketing text suggests you have a "choice of Java, Ruby, Perl, Python, PHP, R, or C++", without mentioning .NET languages. This Amazon thread (http://developer.amazonwebservices.com/connect/thread.jspa?messageID=136051 -- "Support for C# / F# map/reducers") explicitly says that "currently Amazon Elastic MapReduce does not support Mono platform or languages such as C# or F#." The above suggests that it can't be done. I'm wondering if there are any workarounds, though. For example, can I modify the Elastic MapReduce machine image for my account, and install Mono on there? An alternative, suggested by Amazon FAQs "Using Other Software Required by Your Jar" (http://docs.amazonwebservices.com/ElasticMapReduce/latest/DeveloperGuide/index.html?CHAP_AdvancedTopics.html) and "How to Use Additional Files and Libraries With the Mapper or Reducer" (http://docs.amazonwebservices.com/ElasticMapReduce/latest/DeveloperGuide/index.html?addl_files.html), is to make the first step of the Map/Reduce job be to install Mono on the local instance. That sounds kind of inefficient, but maybe it could work? Maybe a saner alternative would be to try to forgo the convenience of Elastic MapReduce, and manually set up my own Hadoop cluster on EC2. Then I assume I could install Mono without difficulty.

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• running .net application over a network

  - by Marlon

  Hello, I need some advice please. I need to enable a .Net application to run over a network share, the problem is that this will be on clients network shares and so the path will not be identical. I've had a quick look at ClickOnce and the publish options in VS2008 but it wants a specific network share location - and I'm assuming this location gets stored somewhere when it does its thing. At the moment the job is being done with a old VB6 application and so gets around all these security issues, but that application is poorly written and almost impossible to maintain so it really needs to go. Is it possible for the domain controller to be set up to allow this specific .Net application to execute? Any other options would be welcomed as I want to get this little application is very business critical. I aught to say that the client networks are schools, and thus are often quite locked down as are the client machines, so manually adding exceptions to each client machine is a big no no. Marlon --Edit-- Apologies, I forgot to mention we're restricted to .net 2.0 for the moment, we are planning to upgrade this to 4.0 but that won't be immediate.

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• XElement vs Dcitionary

  - by user135498

  Hi All, I need advice. I have application that imports 10,000 rows containing name & address from a text file into XElements that are subsequently added to a synchronized queue. When the import is complete the app spawns worker threads that process the XElements by deenqueuing them, making a database call, inserting the database output into the request document and inserting the processed document into an output queue. When all requests have been processed the output queue is written to disk as an XML doc. I used XElements for the requests because I needed the flexibility to add fields to the request during processing. i.e. Depending on the job type the app might require that it add phone number, date of birth or email address to a request based on a name/address match against a public record database. My questions is; The XElements seems to use quite a bit of memory and I know there is a lot of parsing as the document makes its way through the processing methods. I’m considering replacing the XElements with a Dictionary object but I’m skeptical the gain will be worth the effort. In essence it will accomplish the same thing. Thoughts?

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• C# webservice async callback not getting called on HTTP 407 error.

  - by Ben

  Hi, I am trying to test the use-case of a customer having a proxy with login credentials, trying to use our webservice from our client. If the request is synchronous, my job is easy. Catch the WebException, check for the 407 code, and prompt the user for the login credentials. However, for async requests, I seem to be running into a problem: the callback is never getting called! I ran a wireshark trace and did indeed see that the HTTP 407 error was being passed back, so I am bewildered as to what to do. Here is the code that sets up the callback and starts the request: TravelService.TravelServiceImplService svc = new TravelService.TravelServiceImplService(); svc.Url = svcUrl; svc.CreateEventCompleted += CbkCreateEventCompleted; svc.CreateEventAsync(crReq, req); And the code that was generated when I consumed the WSDL: public void CreateEventAsync(TravelServiceCreateEventRequest CreateEventRequest, object userState) { if ((this.CreateEventOperationCompleted == null)) { this.CreateEventOperationCompleted = new System.Threading.SendOrPostCallback(this.OnCreateEventOperationCompleted); } this.InvokeAsync("CreateEvent", new object[] { CreateEventRequest}, this.CreateEventOperationCompleted, userState); } private void OnCreateEventOperationCompleted(object arg) { if ((this.CreateEventCompleted != null)) { System.Web.Services.Protocols.InvokeCompletedEventArgs invokeArgs = ((System.Web.Services.Protocols.InvokeCompletedEventArgs)(arg)); this.CreateEventCompleted(this, new CreateEventCompletedEventArgs(invokeArgs.Results, invokeArgs.Error, invokeArgs.Cancelled, invokeArgs.UserState)); } } Debugging the WS code, I found that even the SoapHttpClientProtocol.InvokeAsync method was not calling its callback as well. Am I missing some sort of configuration?

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• File Storage for Web Applications: Filesystem vs DB vs NoSQL engines

  - by El Yobo

  I have a web application that stores a lot of user generated files. Currently these are all stored on the server filesystem, which has several downsides for me. When we move "folders" (as defined by our application) we also have to move the files on disk (although this is more due to strange design decisions on the part of the original developers than a requirement of storing things on the filesystem). It's hard to write tests for file system actions; I have a mock filesystem class that logs actions like move, delete etc, without performing them, which more or less does the job, but I don't have 100% confidence in the tests. I will be adding some other jobs which need to access the files from other service to perform additional tasks (e.g. indexing in Solr, generating thumbnails, movie format conversion), so I need to get at the files remotely. Doing this over network shares seems dodgy... Dealing with permissions on the filesystem as sometimes given us problems in the past, although now that we've moved to a pure Linux environment this should be less of an issue. What are the downsides of storing files as BLOBs in MySQL? I guess that it would massively increase the database size and reduce the effectiveness of caches, but are there other problems? Do the same problems exist with NoSQL systems like Cassandra? Does anyone have any other suggestions that might be appropriate?

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• Hiring my first employee

  - by Ady

  A few years ago I moved to a new job having been programming for 2 years using C#, however this new company was mainly using VB6. I made the case for .NET and won, but one of the consessions I had to make was to use VB.NET and not C# (understandable as most of the other developers were already using VB). Three years later it was time to move on, but when applying for jobs I couldn't get past the recruitment agents. I realised that when they were looking at the basic requirements (5 years experience) that they could not add 2 and 3 together to make 5. They were looking for 5 years in VB or C# not across both. Frustrated I decided to combine my skills with a designer friend and start my own company. After two years of hard graft we are now looking for our first employee (a programmer), and this question has hit me again, but now I see the employers perspective. Why take the risk of someone getting up to speed when you have thousands of applicants to choose from. So my question is this, if I define the requirements to be too narrow, I could miss the really great candidates. But if they are too broad it's going to take ages to go through them all. This will be our first 'employee' so the choice needs to be good, I can't afford to make a mistake and employ someone naff. Another option would be to choose a bright university graduate, and train them up (less of a risk because we can pay them less). What have others done in this situation, and what would you recommend I do?

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• Script to add user to MediaWiki

  - by Marquis Wang

  I'm trying to write a script that will create a user in MediaWiki, so that I can run a batch job to import a series of users. I'm using mediawiki-1.12.0. I got this code from a forum, but it doesn't look like it works with 1.12 (it's for 1.13) $name = 'Username'; #Username (MUST start with a capital letter) $pass = 'password'; #Password (plaintext, will be hashed later down) $email = 'email'; #Email (automatically gets confirmed after the creation process) $path = "/path/to/mediawiki"; putenv( "MW_INSTALL_PATH={$path}" ); require_once( "{$path}/includes/WebStart.php" ); $pass = User::crypt( $pass ); $user = User::createNew( $name, array( 'password' => $pass, 'email' => $email ) ); $user->confirmEmail(); $user->saveSettings(); $ssUpdate = new SiteStatsUpdate( 0, 0, 0, 0, 1 ); $ssUpdate->doUpdate(); Thanks!

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• acts_as_xapian jobs table

  - by Grnbeagle

  Hi, Can someone explain to me the inner workings of acts_as_xapian_jobs table? I ran into an issue with the acts_as_xapian plugin recently, where I kept getting the following error when it creates an object with xapian indexed fields: Mysql::Error: Duplicate entry 'String-2147483647' for key 2: INSERT INTO `acts_as_xapian_jobs` (`action`, `model`, `model_id`) VALUES ('update', 'String', 23730251831560) It turns out the model_id exceeded the max int value of 2147483647. The workaround was to update model_id to use bigint. Why would the model_id be so huge? By looking at content of acts_as_xapian_jobs, it seems it creates a row for every field that is being indexed.. Understanding how a job gets created in the table would help a great deal. Here's a sampling of the table: mysql> select * from acts_as_xapian_jobs limit 5\G *************************** 1. row *************************** id: 19 model: String model_id: 23804037900560 action: update *************************** 2. row *************************** id: 49 model: String model_id: 23804037191200 action: update *************************** 3. row *************************** id: 79 model: String model_id: 23804037932180 action: update *************************** 4. row *************************** id: 109 model: String model_id: 23804037101700 action: update *************************** 5. row *************************** id: 139 model: String model_id: 23804037722160 action: update Thanks in advance, Amie

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• What should the standard be for ReSTful URLS?

  - by gargantaun

  Since I can't find a chuffing job, I've been reading up on ReST and creating web services. The way I've interpreted it, the future is all about creating a web service for all your data before you build the web app. Which seems like a good idea. However, there seems to be a lot of contradictory thoughts on what the best scheme is for ReSTful URLs. Some people advocate simple pretty urls http://api.myapp.com/resource/1 In addition, some people like to add the API version to the url like so http://api.myapp.com/v1/resource/1 And to make things even more confusing, some people advocate adding the content-type to get requests http://api.myapp.com/v1/resource/1.xml http://api.myapp.com/v1/resource/1.json http://api.myapp.com/v1/resource/1.txt Whereas others think the content-type should be sent in the HTTP header. Soooooooo.... That's a lot of variation, which has left me unsure of what the best URL scheme is. I personally see the merits of the most comprehensive URL that includes a version number, resource locator and content-type, but I'm new to this so I could be wrong. On the other hand, you could argue that you should do "whatever works best for you". But that doesn't really fit with the ReST mentality as far as I can tell since the aim is to have a standard. And since a lot of you people will have more experience than me with ReST, I thought I'd ask for some guidance. So, with all that in mind... What should the standard be for ReSTful URLS?

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• Python and a "time value of money" problem.

  - by jamieb

  (I asked this question earlier today, but I did a poor job of explaining myself. Let me try again) I have a client who is an industrial maintenance company. They sell service agreements that are prepaid 20 hour blocks of a technician's time. Some of their larger customers might burn through that agreement in two weeks while customers with fewer problems might go eight months on that same contract. I would like to use Python to help model projected sales revenue and determine how many billable hours per month that they'll be on the hook for. If each customer only ever bought a single service contract (never renewed) it would be easy to figure sales as monthly_revenue = contract_value * qty_contracts_sold. Billable hours would also be easy: billable_hrs = hrs_per_contract * qty_contracts_sold. However, how do I account for renewals? Assuming that 90% (or some other arbitrary amount) of customers renew, then their monthly revenue ought to grow geometrically. Another important variable is how long the average customer burns through a contract. How do I determine what the revenue and billable hours will be 3, 6, or 12 months from now, based on various renewal and burn rates? I assume that I'd use some type of recursive function but math was never one of my strong points. Any suggestions please? Edit: I'm thinking that the best way to approach this is to think of it as a "time value of money" problem. I've retitled the question as such. The problem is probably a lot more common if you think of "monthly sales" as something similar to annuity payments.

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• Passing Binary Data to a Stored Procedure in SQL Server 2008

  - by Joe Majewski

  I'm trying to figure out a way to store files in a database. I know it's recommended to store files on the file system rather than the database, but the job I'm working on would highly prefer using the database to store these images (files). There are also some constraints. I'm not an admin user, and I have to make stored procedures to execute all the commands. This hasn't been of much difficulty so far, but I cannot for the life of me establish a way to store a file (image) in the database. When I try to use the BULK command, I get an error saying "You do not have permission to use the bulk load statement." The bulk utility seemed like the easy way to upload files to the database, but without permissions I have to figure a work-a-round. I decided to use an HTML form with a file upload input type and handle it with PHP. The PHP calls the stored procedure and passes in the contents of the file. The problem is that now it's saying that the max length of a parameter can only be 128 characters. Now I'm completely stuck. I don't have permissions to use the bulk command and it appears that the max length of a parameter that I can pass to the SP is 128 characters. I expected to run into problems because binary characters and ascii characters don't mix well together, but I'm at a dead end... Thanks

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• Hadoop reduce task gets hung

  - by user806098

  I set up a hadoop cluster with 4 nodes, When running a map-reduce task, the map task finishes quickly, while the reduce task hangs at 27% percent. I checked the log, it's that the reduce task fails to fetch map output from map nodes. The job tracker log of master shows messages like this: 2011-06-27 19:55:14,748 INFO org.apache.hadoop.mapred.JobTracker: Adding task (REDUCE) 'attempt_201106271953_0001_r_000000_0' to tip task_201106271953_0001_r_000000, for tracker 'tracker_web30.bbn.com.cn:localhost/127.0.0.1:56476' And the name node log of master shows messages like this: 2011-06-27 14:00:52,898 INFO org.apache.hadoop.ipc.Server: IPC Server handler 4 on 54310, call register(DatanodeRegistration(202.106.199.39:50010, storageID=DS-1989397900-202.106.199.39-50010-1308723051262, infoPort=50075, ipcPort=50020)) from 192.168.225.19:16129: error: java.io.IOException: verifyNodeRegistration: unknown datanode 202.106.199.3 9:50010 However, neither the "web30.bbn.com.cn" or 202.106.199.39, 202.106.199.3 is the slave node. I think such ip/domains appear because hadoop fails to resolve a node(first in the Intranet DNS server), then it goes to a higher-level DNS server, later to the top, still fails, then the "junk" ip/domains are returned. But I checked my config, it goes like this: /etc/hosts: 127.0.0.1 localhost.localdomain localhost ::1 localhost6.localdomain6 localhost6 192.168.225.16 master 192.168.225.66 slave1 192.168.225.20 slave5 192.168.225.17 slave17 conf/core-site.xml: hadoop.tmp.dir /root/hadoop_tmp/hadoop_${user.name} fs.default.name hdfs://master:54310 io.sort.mb 1024 hdfs-site.xml: dfs.replication 3 masters: master slaves: master slave1 slave5 slave17 Also, all firewalls(iptables) are turned off, and ssh between each 2 nodes is ok. so I don't know where exact the error comes from. Please help. Thanks a lot.

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• Vertically Merge Multiple Tables in MySQL by Joint Primary Key

  - by world

  Hello, I'll attempt to make my question as clear as possible. I'm fairly unexperienced with SQL, only know the really basic queries. In order to have a better idea I'd been reading the MySQL manual for the past few days, but I couldn't really find a concrete solution and my needs are quite specific. I've got 3 MySQL MyISAM tables: table1, table2 and table3. Each table has an ID column (ID, ID2, ID3 respectively), and different data columns. For example table1 has [ID, Name, Birthday, Status, ...] columns, table2 has [ID2, Country, Zip, ...], table3 has [ID3, Source, Phone, ...] you get the idea. The ID, ID2, ID3 columns are common to all three tables... if there's an ID value in table1 it will also appear in table2 and table3. The number of rows in these tables is identical, about 10m rows in each table. What I'd like to do is create a new table that contains (most of) the columns of all three tables and merge them into it. The dates, for instance, must be converted because right now they're in VARCHAR YYYYMMDD format. Reading the MySQL manual I figured STR_TO_DATE() would do the job, but I don't know how to write the query itself in the first place so I have no idea how to integrate the date conversion. So basically, after I create the new table (which I do know how to do), how can I merge the three tables into it, integrating into the query the date conversion?

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• java: can't use constructors in abstract class

  - by ufk

  Hi. I created the following abstract class for job scheduler in red5: package com.demogames.jobs; import com.demogames.demofacebook.MysqlDb; import org.red5.server.api.IClient; import org.red5.server.api.IConnection; import org.red5.server.api.IScope; import org.red5.server.api.scheduling.IScheduledJob; import org.red5.server.api.so.ISharedObject; import org.apache.log4j.Logger; import org.red5.server.api.Red5; /** * * @author ufk */ abstract public class DemoJob implements IScheduledJob { protected IConnection conn; protected IClient client; protected ISharedObject so; protected IScope scope; protected MysqlDb mysqldb; protected static org.apache.log4j.Logger log = Logger .getLogger(DemoJob.class); protected DemoJob (ISharedObject so, MysqlDb mysqldb){ this.conn=Red5.getConnectionLocal(); this.client = conn.getClient(); this.so=so; this.mysqldb=mysqldb; this.scope=conn.getScope(); } protected DemoJob(ISharedObject so) { this.conn=Red5.getConnectionLocal(); this.client=this.conn.getClient(); this.so=so; this.scope=conn.getScope(); } protected DemoJob() { this.conn=Red5.getConnectionLocal(); this.client=this.conn.getClient(); this.scope=conn.getScope(); } } Then i created a simple class that extends the previous one: public class StartChallengeJob extends DemoJob { public void execute(ISchedulingService service) { log.error("test"); } } The problem is that my main application can only see the constructor without any parameters. with means i can do new StartChallengeJob() why doesn't the main application sees all the constructors ? thanks!

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• Ultra-Portable Laptop or Tablet PC for Development and Sketching

  - by Nelson LaQuet

  I am a software developer that primarily writes in PHP, [X]HTML, CSS, Javascript, C# and C++. I use Eclipse for web development, Visual Studio 2008 for C++ and C# work, TortoiseSVN, Subversion server for local repositories, SQL Server Express, Apache and MYSQL. I also use Office 2007 for word processing and spreadsheets and use Vista Ultimate 64 as my primary operating system. The only other things I do on my laptop are watch movies, surf the internet and listen to music. I currently have a Acer Aspire 5100 (1.4 GHz AMD Turion X2, 2 GB of RAM and a 15.4" screen). This thing does not cut it in performance or portability, and in addition, my DVD drive failed. And before anybody posts about vista: I have had XP Professional 32 on it for the last two years, and recently upgraded to Vista 64. It is actually faster (with areo disabled) then XP; so it is not the OS that is causing the laptop to be slow. I usually sketch a lot, for explaining things, developing user interfaces and software architecture. Because of my requirements, I was thinking about a Lenovo X61 Tablet PC. It outperforms my current laptop, is significantly more portable, and... is a tablet. My question is: do any other software developers use this (or other tablets) for programming? Does it help to be able to sketch on the computer itself? And is it capable of being a good development machine? Will it handle the above software listed? If not, what is the best ultra-portable laptop that is good for programming? Or are ultra-portable laptops even good for programming? I could manage with my 15.4" screen, but am spoiled by my two 19" at my home desktop and my job's workstation.

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• How can I diagnose "Cannot determine peer address" in my Perl TCP script?

  - by MadBoy

  I've this little script which does it's job pretty well but sometimes it tends to fail. It fails in 2 cases: with error send: Cannot determine peer address at ./tcp-new.pl line 52 with no output or anything, it just fails to deliver what it got to connected Tcp Client. Usually it happens after I disconnect from server, go home and connect it again. To fix this restart is required and it starts working. Sometimes this problem is followed by problem mentioned in point 1. Note: it's not problem when I disconnect and reconnect to it again within short amount of time (unless error nr 1 happens). So can anyone help me make this code be a bit more stable so I don't have to restart it every day? #!/usr/bin/perl use strict; use warnings; use IO::Socket; use IO::Select; my $tcp_port = "10008"; my $udp_port = "2099"; my $tcp_socket = IO::Socket::INET->new( Listen => SOMAXCONN, LocalPort => $tcp_port, Proto => 'tcp', ReuseAddr => 1, ); my $udp_socket = IO::Socket::INET->new( LocalPort => $udp_port, Proto => 'udp', ); my $read_select = IO::Select->new(); my $write_select = IO::Select->new(); $read_select->add($tcp_socket); $read_select->add($udp_socket); while (1) { my @read = $read_select->can_read(); foreach my $read (@read) { if ($read == $tcp_socket) { my $new_tcp = $read->accept(); $write_select->add($new_tcp); } elsif ($read == $udp_socket) { my $recv_buffer; $udp_socket->recv($recv_buffer, 1024, undef); my @write = $write_select->can_write(); foreach my $write (@write) { $write->send($recv_buffer); } } } }

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• About redirected stdout in System.Diagnostics.Process

  - by sforester

  I've been recently working on a program that convert flac files to mp3 in C# using flac.exe and lame.exe, here are the code that do the job: ProcessStartInfo piFlac = new ProcessStartInfo( "flac.exe" ); piFlac.CreateNoWindow = true; piFlac.UseShellExecute = false; piFlac.RedirectStandardOutput = true; piFlac.Arguments = string.Format( flacParam, SourceFile ); ProcessStartInfo piLame = new ProcessStartInfo( "lame.exe" ); piLame.CreateNoWindow = true; piLame.UseShellExecute = false; piLame.RedirectStandardInput = true; piLame.RedirectStandardOutput = true; piLame.Arguments = string.Format( lameParam, QualitySetting, ExtractTag( SourceFile ) ); Process flacp = null, lamep = null; byte[] buffer = BufferPool.RequestBuffer(); flacp = Process.Start( piFlac ); lamep = new Process(); lamep.StartInfo = piLame; lamep.OutputDataReceived += new DataReceivedEventHandler( this.ReadStdout ); lamep.Start(); lamep.BeginOutputReadLine(); int count = flacp.StandardOutput.BaseStream.Read( buffer, 0, buffer.Length ); while ( count != 0 ) { lamep.StandardInput.BaseStream.Write( buffer, 0, count ); count = flacp.StandardOutput.BaseStream.Read( buffer, 0, buffer.Length ); } Here I set the command line parameters to tell lame.exe to write its output to stdout, and make use of the Process.OutPutDataRecerved event to gather the output data, which is mostly binary data, but the DataReceivedEventArgs.Data is of type "string" and I have to convert it to byte[] before put it to cache, I think this is ugly and I tried this approach but the result is incorrect. Is there any way that I can read the raw redirected stdout stream, either synchronously or asynchronously, bypassing the OutputDataReceived event? PS: the reason why I don't use lame to write to disk directly is that I'm trying to convert several files in parallel, and direct writing to disk will cause severe fragmentation. Thanks a lot!

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• Stale connection with Pheanstalk

  - by token47

  I'm using beanstalkd to offload some work to other machines. The setup is a bit unusual, the server is on the internet (public ip) but the consumers are behind adsl lines on some peoples homes. So there is a linux server as client going out through a dynamic ip and connecting to the server to get a job. It's all PHP and I'm using pheanstalk library. Everything runs smoothly for some time, but then the adsl changes the IP (every 24h hours the provider forces a disconnect-reconnect) the client just hangs, never to go out of "reserve". I thought that putting a timeout on the reserve would help it, but it didn't. As it seems, the client issues a command and blocks, it never checks the timeout. It just issues a reserve-with-timeout (instead of a simple reserve) and it is the servers responsibility to return a TIME_OUT as the timeout occurs. The problem is, the connection is broken (but the TCP/IP doesn't know about that yet until any of the sides try to talk to the other side) and if the client blocked reading, it will never return. The library seems to have support for some kind of timeouts locally (for example when trying to connect to server), but it does not seem to contemplate this scenario. How could I detect the stale connection and force a reconnect? Is there some kind of keepalive on the protocol (and on the pheanstalk itself)? Thanks!

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• Licensing iPhone apps per user in existing system

  - by Alxandr

  I've been asked by my job to write a iPhone app for an existing system for managing worktasks. This system is proprietary and costs money, so in order to login you need to be a customer. Now, I've got two questions about the legality of licensing iPhone apps with this system: My company would like to be able to sell the app for profit, but not as a one-time payment, but as a added subscription-fee to the already existing one. Is it legal for us (according with the terms of distributing an iPhone app on the Apple App Store) to do this? That way we'll just add another field to the users-database saying weather or not iPhone is enabled for them, and distribute the app as a free app on App Store. If the previous question is not legal, we'd like to just create a free app and distribute it as part of the existing system. In other words, no extra fee for using the iPhone app for the users, but still free distribution trough App Store. Due to our company not being american or having an office in the U.S. at all enterprice account is not an option. Please let me know if there is anything wrong with any of the above approaches.

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• Elegant way of parsing Data files for Simulation

  - by sc_ray

  I am working on this project where I need to read in a lot of data from .dat files and use the data to perform simulations. The data in my .dat file looks as follows: DeviceID InteractingDeviceID InteractionStartTime InteractionEndTime 1 2 1101 1105 1,2 1101 and 1105 are tab delimited and it means Device 1 interacted with Device 2 at 1101 ms and ended the interaction at 1105ms. I have a trace data sets that compile thousands of such interactions and my job is to analyze these interactions. The first step is to parse the file. The language of choice is C++. The approach I was thinking of taking was to read the file, for every line that's read create a Device Object. This Device object will contain the property DeviceId and an array/vector of structs, that will contain a list of all the devices the given DeviceId interacted with over the course of the simulation.The struct will contain the Interacting Device Id, Interaction Start Time and Interaction End Time. I have a two fold question here: Is my approach correct? If I am on the right track, how do I rapidly parse these tab delimited data files and create Device objects without excessive memory overhead using C++? A push in the right direction will be much appreciated. Thanks

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• Extension methods for encapsulation and reusability

  - by tzaman

  In C++ programming, it's generally considered good practice to "prefer non-member non-friend functions" instead of instance methods. This has been recommended by Scott Meyers in this classic Dr. Dobbs article, and repeated by Herb Sutter and Andrei Alexandrescu in C++ Coding Standards (item 44); the general argument being that if a function can do its job solely by relying on the public interface exposed by the class, it actually increases encapsulation to have it be external. While this confuses the "packaging" of the class to some extent, the benefits are generally considered worth it. Now, ever since I've started programming in C#, I've had a feeling that here is the ultimate expression of the concept that they're trying to achieve with "non-member, non-friend functions that are part of a class interface". C# adds two crucial components to the mix - the first being interfaces, and the second extension methods: Interfaces allow a class to formally specify their public contract, the methods and properties that they're exposing to the world. Any other class can choose to implement the same interface and fulfill that same contract. Extension methods can be defined on an interface, providing any functionality that can be implemented via the interface to all implementers automatically. And best of all, because of the "instance syntax" sugar and IDE support, they can be called the same way as any other instance method, eliminating the cognitive overhead! So you get the encapsulation benefits of "non-member, non-friend" functions with the convenience of members. Seems like the best of both worlds to me; the .NET library itself providing a shining example in LINQ. However, everywhere I look I see people warning against extension method overuse; even the MSDN page itself states: In general, we recommend that you implement extension methods sparingly and only when you have to. So what's the verdict? Are extension methods the acme of encapsulation and code reuse, or am I just deluding myself?

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• how to determine if a character vector is a valid numeric or integer vector

  - by Andrew Barr

  I am trying to turn a nested list structure into a dataframe. The list looks similar to the following (it is serialized data from parsed JSON read in using the httr package). myList <- list(object1 = list(w=1, x=list(y=0.1, z="cat")), object2 = list(w=2, x=list(y=0.2, z="dog"))) unlist(myList) does a great job of recursively flattening the list, and I can then use lapply to flatten all the objects nicely. flatList <- lapply(myList, FUN= function(object) {return(as.data.frame(rbind(unlist(object))))}) And finally, I can button it up using plyr::rbind.fill myDF <- do.call(plyr::rbind.fill, flatList) str(myDF) #'data.frame': 2 obs. of 3 variables: #$ w : Factor w/ 2 levels "1","2": 1 2 #$ x.y: Factor w/ 2 levels "0.1","0.2": 1 2 #$ x.z: Factor w/ 2 levels "cat","dog": 1 2 The problem is that w and x.y are now being interpreted as character vectors, which by default get parsed as factors in the dataframe. I believe that unlist() is the culprit, but I can't figure out another way to recursively flatten the list structure. A workaround would be to post-process the dataframe, and assign data types then. What is the best way to determine if a vector is a valid numeric or integer vector?

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• Looking for fast, minimal, preferrably free disc cloning software [closed]

  - by Dave

  We have to test our application installation and functionality on many Windows operating system versions and languages (XP, Vista, Win7; English, Spanish, Portuguese, etc; 32-bit & b4-bit.) While we can do much of this in virtual machines, we have noticed that VM's sometimes hide problems, or raise false bugs. So, we need to do "bare metal" OS installation for much of our testing. I have been using Acronis True Image for the past year, and am not impressed. It often gives random errors which require a reboot, and is really slow. For example, when trying to restore an image, it goes through a "Locking partition" cycle about three times (once after you click OK on each step of the wizard), each of which can take 5 minutes to complete. This all happens BEFORE it actually starts the image copy, which is sometimes quick (3-5 minutes), sometimes long (hours). The size of all of our images are roughly the same, so that is not related. So, anyway, I'm looking to switch to something else: I only need very basic functionality--just creating images of entire discs, and then restoring those images onto the exact same hard drive at a later date. That's it. I'm not opposed to paying for a good piece of software, but if there is something free out there that does the job well, that would be a preference. My OS on which the imaging software would run is Windows Vista, but a bootable media (into a Linux flavor) would be fine also, as long as its quick to use and reliable. Recommendations? (Also, moderators, if this should be a CW, I'll be happy to mark it as such; unclear about the rules there.)

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• IE browser script to determine which (if any) ActiveX control will handle specific mime type

  - by Jay13

  I'm trying to figure out in an IE script (javascript or vbscript) which ActiveX control will handle a specific mime type, "image/tiff" in this case. This is easy to do in other browsers that use plugins with; navigator.mimeTypes["image/tiff"].enabledPlugin.name which would return something like QuickTime Plug-in X.X.X I've found plenty of examples to tell if a specific plugin is loaded but since there are several plugins available that can handle tiff images I need to know which, if any, is registered to handle this mime type. The problem I'm trying to deal with is that QuickTime always wants to register itself as the default tiff viewer but it does a terrible job of it resulting in lots of support calls. Unfortunately, simply detecting that QuickTime is installed isn't good enough since the user may also have another tiff viewer installed (like Alternatiff) as the default tiff viewer or the user may have configured QuickTime to not be the default viewer for tiff images so the browser could be using a helper app to display the image instead. Not meaning to be difficult but before anyone suggests reengineering workarounds; yes I know I could force the user to use a specific ActiveX viewer in IE or to use a Java tiff viewer but I'd rather let them use a viewer of their choice rather than forcing them to install a viewer of my choosing, especially since their viewer may be a helper app that loads the tiff image into a business workflow within their office yes I know there are other image formats that I could use but tiff is the defacto standard for document imaging and that's what the vast majority of these users prefer to use. The problem isn't the image format, it's that QuickTime just doesn't cut it as a tiff viewer Thanks in advance for any suggestions or solutions...

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• Message queue proxy in Python + Twisted

  - by gasper_k

  Hi, I want to implement a lightweight Message Queue proxy. It's job is to receive messages from a web application (PHP) and send them to the Message Queue server asynchronously. The reason for this proxy is that the MQ isn't always avaliable and is sometimes lagging, or even down, but I want to make sure the messages are delivered, and the web application returns immediately. So, PHP would send the message to the MQ proxy running on the same host. That proxy would save the messages to SQLite for persistence, in case of crashes. At the same time it would send the messages from SQLite to the MQ in batches when the connection is available, and delete them from SQLite. Now, the way I understand, there are these components in this service: message listener (listens to the messages from PHP and writes them to a Incoming Queue) DB flusher (reads messages from the Incoming Queue and saves them to a database; due to SQLite single-threadedness) MQ connection handler (keeps the connection to the MQ server online by reconnecting) message sender (collects messages from SQlite db and sends them to the MQ server, then removes them from db) I was thinking of using Twisted for #1 (TCPServer), but I'm having problem with integrating it with other points, which aren't event-driven. Intuition tells me that each of these points should be running in a separate thread, because all are IO-bound and independent of each other, but I could easily put them in a single thread. Even though, I couldn't find any good and clear (to me) examples on how to implement this worker thread aside of Twisted's main loop. The example I've started with is the chatserver.py, which uses service.Application and internet.TCPServer objects. If I start my own thread prior to creating TCPServer service, it runs a few times, but the it stops and never runs again. I'm not sure, why this is happening, but it's probably because I don't use threads with Twisted correctly. Any suggestions on how to implement a separate worker thread and keep Twisted? Do you have any alternative architectures in mind?

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