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• Need help with WCF design

  - by Jason

  I have been tasked with creating a set of web services. We are a Microsoft shop, so I will be using WCF for this project. There is an interesting design consideration that I haven't been able to figure out a solution for yet. I'll try to explain it with an example: My WCF service exposes a method named Foo(). 10 different users call Foo() at roughly the same time. I have 5 special resources called R1, R2, R3, R4, and R5. We don't really need to know what the resource is, other than the fact that a particular resource can only be in use by one caller at a time. Foo() is responsible to performing an action using one of these special resources. So, in a round-robin fashion, Foo() needs to find a resource that is not in use. If no resources are available, it must wait for one to be freed up. At first, this seems like an easy task. I could maybe create a singleton that keeps track of which resources are currently in use. The big problem is the fact that I need this solution to be viable in a web farm scenario. I'm sure there is a good solution to this problem, but I've just never run across this scenario before. I need some sort of resource tracker / provider that can be shared between multiple WCF hosts. Any ideas from the architects out there would be greatly appreciated!

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• rewrite not a member of LiftRules

  - by José Leal

  Hi guys, I was following http://www.assembla.com/wiki/show/liftweb/URL_Rewriting tutorial for url rewritting in liftweb.. but I get this error: error: value rewrite is not a member of object net.liftweb.http.LiftRules .. it is really odd.. and the documentation says that it exists. I'm using idea IDE, and I've done everything from scratch, using the lift maven blank archifact. Some more info: [INFO] ------------------------------------------------------------------------ [INFO] Building Joseph3 [INFO] task-segment: [tomcat:run] [INFO] ------------------------------------------------------------------------ [INFO] Preparing tomcat:run [INFO] [resources:resources {execution: default-resources}] [WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent! [INFO] Copying 0 resource [INFO] [yuicompressor:compress {execution: default}] [INFO] nb warnings: 0, nb errors: 0 [INFO] artifact org.mortbay.jetty:jetty: checking for updates from scala-tools.org [INFO] artifact org.mortbay.jetty:jetty: checking for updates from central [INFO] [compiler:compile {execution: default-compile}] [INFO] Nothing to compile - all classes are up to date [INFO] [scala:compile {execution: default}] [INFO] Checking for multiple versions of scala [INFO] /home/dpz/Scala/Doit/Joseph3/src/main/scala:-1: info: compiling [INFO] Compiling 2 source files to /home/dpz/Scala/Doit/Joseph3/target/classes at 1274922123910 [ERROR] /home/dpz/Scala/Doit/Joseph3/src/main/scala/bootstrap/liftweb/Boot.scala:16: error: value rewrite is not a member of object net.liftweb.http.LiftRules [INFO] LiftRules.rewrite.prepend(NamedPF("ProductExampleRewrite") { [INFO] ^ [ERROR] one error found [INFO] ------------------------------------------------------------------------ [ERROR] BUILD ERROR [INFO] ------------------------------------------------------------------------ [INFO] wrap: org.apache.commons.exec.ExecuteException: Process exited with an error: 1(Exit value: 1) [INFO] ------------------------------------------------------------------------ [INFO] For more information, run Maven with the -e switch [INFO] ------------------------------------------------------------------------ [INFO] Total time: 19 seconds [INFO] Finished at: Thu May 27 03:02:07 CEST 2010 [INFO] Final Memory: 20M/175M [INFO] ------------------------------------------------------------------------ Process finished with exit code 1 enter code here

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• Full Text Search in SQL Server 2008 shows wrong display_item for Thai language

  - by ensecoz

  I am working with SQL Server 2008. My task is to investigate the issue where FTS cannot find the right result for Thai. First, I have the table which enables the FTS on the column 'ItemName' which is nvarchar. The Catalog is created with the Thai Language. Note that the Thai language is one of the languages that doesn't separate the word by spaces, so '????' '???' '????' are written like this in a sentence: '???????????' In the table, there are many rows that include the word (????); for example row#1 (ItemName: '???????????') On the webpage, I try to search for '????' but SQL Server cannot find it. So I try to investigate it by trying the following query in SQL Server: select * from sys.dm_fts_parser(N'"???????????"', 1054, 0, 0) ...to see how the words are broken. The first one is the text to be broken. The second parameter is to specify that we're using Thai (WorkBreaker, so on). Here is the result: row#1 (display_item: '????', source_item: '???????????') row#2 (display_item: '????', source_item: '???????????') row#3 (display_item: '??', source_item: '???????????') Notice that the first and second row display the wrong display_item '?' in the '????' isn't even Thai characters. '?' in '????' is not a Thai character either. So the question is where did those alien characters come from? I guess this why I cannot search for '????' because the word breaker is broken and keeping the wrong character in the indexes. Please help!

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• DB2 Child Table Not Working - Create Table

  - by gamerzfuse

  I have a bit of a task before me. (DB2 Database) I need to create a table that will be a child table (is that what it is called in SQL?) I need it so that it has a foreign key constraint with my other table, so when the parent table is modified (record deleted) the child table also loses that record. Once I have the table, I also need to populate it with the data from the other table (if there is an easy way to UPDATE this). If you could point me in the right direction, this would help alot, as I do not even know what syntax to look for. Thanks in advance The table I have in place: create table titleauthors ( au_id char(11), title_id char(6), au_ord integer, royaltyshare decimal(5,2)); The table I am creating: create table titles ( title_id char(6), title varchar(80), type varchar(12), pub_id char(4), price decimal(9,2), advance decimal(9,2), ytd_sales integer, contract integer, notes varchar(200), pubdate date); I need the title_id to be matched with the title_id from the parent table AND use the ON DELETE CASCADE syntax to delete when that table is deleted from. My Attempt: CREATE TABLE BookTitles ( title_id char(6) NOT NULL CONSTRAINT BookTitles_title_id_pk REFERENCES titleauthors(title_id) ON DELETE CASCADE, title varchar(80) NOT NULL, type varchar(12), pub_id char(4), price decimal(9,2), advance decimal(9,2), ytd_sales integer, contract integer, notes varchar(200), pubdate date) ; Thanks in advance!

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• Lazy non-modifiable list

  - by mindas

  I was looking for a decent implementation of a generic lazy non-modifiable list implementation to wrap my search result entries. The unmodifiable part of the task is easy as it can be achieved by Collections.unmodifiableList() so I only need to sort out the the lazy part. Surprisingly, google-collections doesn't have anything to offer; while LazyList from Apache Commons Collections does not support generics. I have found an attempt to build something on top of google-collections but it seems to be incomplete (e.g. does not support size()), outdated (does not compile with 1.0 final) and requiring some external classes, but could be used as a good starting point to build my own class. Is anybody aware of any good implementation of a LazyList? If not, which option do you think is better: write my own implementation, based on google-collections ForwardingList, similar to what Peter Maas did; write my own wrapper around Commons Collections LazyList (the wrapper would only add generics so I don't have to cast everywhere but only in the wrapper itself); just write something on top of java.util.AbstractList; Any other suggestions are welcome.

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• Help, my CentOS servers keep going down , No route to host after a random uptime [closed]

  - by user249071

  Hello , I have a couple of Centos linux servers, that have a very simple task, they run nginx + fastcgi for php , and some NFS mounts between them, readonly They have some RPC commands to start some downloading processes with wget, nothing fancy , from a main server, but their behavior is very unstable, they simply go down, we tried to monitor ram , processor usage, even network connections, they don't load up so much, max network connections up to... 250 max, 15% processor usage and memory , well, doesn't even fill up, 2.5GB from 8GB max , I have no ideea why can a linux server go down like that, they aren't even public servers, no domain names installed no public serving, for sites. The only thing that I've discovered was that if i didn't restart the network service every couple of hours or so... the servers were becoming very slow, starting apps very slow, but not repoting a high usage of resources...Maybe Centos doesn't free the timeout connections, or something like that...It's based on Red Hat right? I'm not a linux expert , but I'm sure that there are a few guys out there that can easily have an answer to this , or even have some leads to what i can do ... I haven't installed snort, or other things to view if we have some DOS attacks, still the scheduled script that restarts the network each hour should put the system back online, and it doesn't.... Thank you in advance

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• jQuery server ping slowly but surely filling memory?

  - by danspants

  I use the following piece of code to test if our server is running whilst the user is in a page. I've also started adding other functions that grab small amounts of data that are constantly changing and are to be relayed to the user (Files waiting for download, messages, reports etc). I've noticed recently that if I leave any page open (all pages contain the same function), the browser takes up more and more system memory which I can only attribute to this regular task (overnight it reached 1.6 gb). Is there some way of clearing out the data that is being accumulated? Is this normal behaviour? As far as i can tell, every time I call the function it should overwrite the previously retrieved data? function testServer(){ jQuery.ajax({ type:"HEAD", url:"/media/d_arrow_blue.png", error: function(msg) { jQuery.jGrowl("Server Disconnected"); } }); //retrieves count of files awaiting download - move to seperate function jQuery.get("/get_files/",{"type":"count"},function(data) { jQuery("#downloadList").children("div").text(data); }); }; jQuery().doTimeout(6000,function() { testServer(); return true; });

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• What should a self-taught programmer with no degree learn/read?

  - by sjbotha

  I am a self-taught programmer and I do do not have any degrees. I started pretty young and I've got about 7 years of actual programming work experience. I believe I'm a pretty good programmer, but I admit that I have not played much with algorithms or delved into any really low-level aspects of programming such as how compilers work. I have worked with other programmers with and without degrees. Some were good and some not; having a degree didn't seem to make any difference as to which pot they fell into. Since then I've come to realize that it does depend on the school where the degree is obtained. Some people suggest that you really should get a degree; that there are things you'll learn in the process that you won't learn in the real world. Of course there is personal growth and discipline learned from completing a task of that magnitude, but let's just concentrate on the technical knowledge. What would I have been taught in a GOOD CS course that would aid me today and what can I read to fill the gap? I've heard the book "Algorithms" mentioned and I plan on reading that. What other books would you recommend? Edit: Clarification on 'actual work experience': Have worked for 2 small companies on teams with fewer than 5 people. About 2 years experience with Perl, Python, PHP, C, C++. About 5 years experience in Java, Applets, RMI, T-SQL, PL/SQL, VB6. 7 years experience in HTML, Javascript, bash, SQL. Most recently in Java designed and helped build an N-tier Java app with web frontend and RMI.

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• PHP: Aggregate Model Classes or Uber Model Classes?

  - by sunwukung

  In many of the discussions regarding the M in MVC, (sidestepping ORM controversies for a moment), I commonly see Model classes described as object representations of table data (be that an Active Record, Table Gateway, Row Gateway or Domain Model/Mapper). Martin Fowler warns against the development of an anemic domain model, i.e. a class that is nothing more than a wrapper for CRUD functionality. I've been working on an MVC application for a couple of months now. The DBAL in the application I'm working on started out simple (on account of my understanding - oh the benefits of hindsight), and is organised so that Controllers invoke Business Logic classes, that in turn access the database via DAO/Transaction Scripts pertinent to the task at hand. There are a few "Entity" classes that aggregate these DAO objects to provide a convenient CRUD wrapper, but also embody some of the "behaviour" of that Domain concept (for example, a user - since it's easy to isolate). Taking a look at some of the code, and thinking along refactoring some of the code into a Rich Domain Model, it occurred to me that were I to try and wrap the CRUD routines and behaviour of say, a Company into a single "Model" class, that would be a sizeable class. So, my question is this: do Models represent domain objects, business logic, service layers, all of the above combined? How do you go about defining the responsibilities for these components?

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• Can a standalone ruby script (windows and mac) reload and restart itself?

  - by user30997

  I have a master-workers architecture where the number of workers is growing on a weekly basis. I can no longer be expected to ssh or remote console into each machine to kill the worker, do a source control sync, and restart. I would like to be able to have the master place a message out on the network that tells each machine to sync and restart. That's where I hit a roadblock. If I were using any sane platform, I could just do: exec('ruby', __FILE__) ...and be done. However, I did the following test: p Process.pid sleep 1 exec('ruby', __FILE__) ...and on Windows, I get one ruby instance for each call to exec. None of them die until I hit ^C on the window in question. On every platform I tried this on, it is executing the new version of the file each time, which I have verified this by making simple edits to the test script while the test marched along. The reason I'm printing the pid is to double-check the behavior I'm seeing. On windows, I am getting a different pid with each execution - which I would expect, considering that I am seeing a new process in the task manager for each run. The mac is behaving correctly: the pid is the same for every system call and I have verified with dtrace that each run is trigging a call to the execve syscall. So, in short, is there a way to get a windows ruby script to restart its execution so it will be running any code - including itself - that has changed during its execution? Please note that this is not a rails application, though it does use activerecord.

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• How to design Models the correct way: Object-oriented or "Package"-oriented?

  - by ajsie

  I know that in OOP you want every object (from a class) to be a "thing", eg. user, validator etc. I know the basics about MVC, how they different parts interact with each other. However, i wonder if the models in MVC should be designed according to the traditional OOP design, that is to say, should every model be a database/table/row (solution 2)? Or is the intention more like to collect methods that are affecting the same table or a bunch of related tables (solution 1). example for an Address book module in CodeIgniter, where i want be able to "CRUD" a Contact and add/remove it to/from a CRUD-able Contact Group. Models solution 1: bunching all related methods together (not real object, rather a "package") class Contacts extends Model { function create_contact() {) function read_contact() {} function update_contact() {} function delete_contact() {} function add_contact_to_group() {} function delete_contact_from_group() {} function create_group() {} function read_group() {} function update_group() {} function delete_group() {} } Models solution 2: the OOP way (one class per file) class Contact extends Model { private $name = ''; private $id = ''; function create_contact() {) function read_contact() {} function update_contact() {} function delete_contact() {} } class ContactGroup extends Model { private $name = ''; private $id = ''; function add_contact_to_group() {} function delete_contact_from_group() {} function create_group() {} function read_group() {} function update_group() {} function delete_group() {} } i dont know how to think when i want to create the models. and the above examples are my real tasks for creating an Address book. Should i just bunch all functions together in one class. then the class contains different logic (contact and group), so it can not hold properties that are specific for either one of them. the solution 2 works according to the OOP. but i dont know why i should make such a dividing. what would the benefits be to have a Contact object for example. Its surely not a User object, so why should a Contact "live" with its own state (properties and methods). you experienced guys with OOP/MVC, please shed a light on how one should think here in this very concrete task.

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• Which DHT algorithm to use (if I want to join two separate DHTs)?

  - by webdreamer

  I've been looking into some DHT systems, specially Pastry and Chord. I've read some concerns about Chord's reaction to churn, though I believe that won't be a problem for the task I have at hands. I'm implementing some sort of social network service that doesn't rely on any central servers for a course project. I need the DHT for the lookups. Now I don't know of all the servers in the network in the beginning. As I've stated, there's no main tracker server. It works this way: each client has three dedicated servers. The three servers have the profile of the client, and it's wall, it's personal info, replicated. I only get to know about other group of servers when the user adds a friend (inputing the client's address). So I would create two separate DHTs on the two groups of three servers and when they friend each other I would like to join the DHTs. I would like to this consistently. I haven't had a lot of time to get all that familiar with the protocols, so I would like to know which one is better if I want to join the two separate DHTs?

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• Hadoop Map/Reduce - simple use example to do the following...

  - by alexeypro

  I have MySQL database, where I store the following BLOB (which contains JSON object) and ID (for this JSON object). JSON object contains a lot of different information. Say, "city:Los Angeles" and "state:California". There are about 500k of such records for now, but they are growing. And each JSON object is quite big. My goal is to do searches (real-time) in MySQL database. Say, I want to search for all JSON objects which have "state" to "California" and "city" to "San Francisco". I want to utilize Hadoop for the task. My idea is that there will be "job", which takes chunks of, say, 100 records (rows) from MySQL, verifies them according to the given search criteria, returns those (ID's) which qualify. Pros/cons? I understand that one might think that I should utilize simple SQL power for that, but the thing is that JSON object structure is pretty "heavy", if I put it as SQL schemas, there will be at least 3-5 tables joins, which (I tried, really) creates quite a headache, and building all the right indexes eats RAM faster than I one can think. ;-) And even then, every SQL query has to be analyzed to be utilizing the indexes, otherwise with full scan it literally is a pain. And with such structure we have the only way "up" is just with vertical scaling. But I am not sure it's the best option for me, as I see how JSON objects will grow (the data structure), and I see that the number of them will grow too. :-) Help? Can somebody point me to simple examples of how this can be done? Does it make sense at all? Am I missing something important? Thank you.

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• How to change default locale in BIRT

  - by zlajo

  Hi everybody, I am working with the BIRT reporting engine and my current task is to implement internationalization for reports. We are using the webviewer to generate and download pdf reports. There is a parameter (__locale) which allows me to specify the locale that should be used to generate a report. So far everything works fine. There is an additional requirement I have not been able to implement, though. Additionally to the locale which is set by the http parameter there should also be the possibility to specify some kind of fallback locale. Take the following example: There are two property-files common_en_US.properties and common_en_GB.properties. The first locale to be used should be en_GB (__locale=en_GB). Everything works fine if the common_en_GB.properties file exist. But I would also like to tell BIRT to use common_en_US.properties if the en_GB-file cannot be found, which does not work as expected. I tried to solve this by manually setting the Java default locale before executing BIRT because I thought that BIRT would use the Java mechanism to resolve localized strings. Unfortunately this attempt does not work. Is there a different way to do what I would like to do? Is it possible to do something like that at all? Thanks a lot! Johannes

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• Simplest way to automatically alter "const" value in Java during compile time

  - by Michael Mao

  Hi all: This is a question corresponds to my uni assignment so I am very sorry to say I cannot adopt any one of the following best practices in a short time -- you know -- assignment is due tomorrow :( link to Best way to alter const in Java on StackOverflow Basically the only task (I hope so) left for me is the performance tuning. I've got a bunch of predefined "const" values in my single-class agent source code like this: //static final values private static final long FT_THRESHOLD = 400; private static final long FT_THRESHOLD_MARGIN = 50; private static final long FT_SMOOTH_PRICE_IDICATOR = 20; private static final long FT_BUY_PRICE_MODIFIER = 0; private static final long FT_LAST_ROUNDS_STARTTIME = 90; private static final long FT_AMOUNT_ADJUST_MODIFIER = 5; private static final long FT_HISTORY_PIRCES_LENGTH = 10; private static final long FT_TRACK_DURATION = 5; private static final int MAX_BED_BID_NUM_PER_AUC = 12; I can definitely alter the values manually and then compile the code to give it another go around. But the execution time for a thorough "statistic analysis" usually requires over 2000 times of execution, which will typically lasts more than half an hour on my own laptop... So I hope there is a way to alter values using other ways than dig into the source code to change the "const" values there, so I can automatically distributed compiled code to other people's PC and let them run the statistic analysis instead. One other reason for a automatically value adjustment is that I can try using my own agent to defeat itself by choosing different "const" values. Although my values are derived from previous history and statistical results, they are far from the most optimized values. I hope there is a easy way so I can quickly adopt that so to have a good sleep tonight while the computer does everything for me... :) Any hints on this sort of stuff? Any suggestion is welcomed and much appreciated.

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• Can't get data with spaces into the database from Ajax POST request

  - by J Jones

  I have a real simple form with a textbox and a button, and my goal is to have an asynchronous request (jQuery: $.ajax) send the text to the server (PHP/mysql a la Joomla) so that it can be added to a database table. Here's the javascript that is sending the data from the client: var value= $('#myvalue').val(); $.ajax( { type: "POST", url: "/administrator/index.php", data: { option: "com_mycomponent", task: "enterValue", thevalue: value, format: "raw"}, dataType: "text", success: reportSavedValue } ); The problem arises when the user enters text with a space in it. The $_POST variable that I receive has all the spaces stripped out, so that if the user enters "This string has spaces", the server gets the value "Thisstringhasspaces". I have been googling around, and have found lots of references that I need to use encodeURIComponent. So I have tried it, but now the value that I get from $_POST is "This20string20has20spaces". So it appears to be encoding it the way I would expect, only to have the percent signs stripped instead of the spaces, and leaving the hex numbers. I'm really confused. It seems that this sort of question is asked and answered everywhere on the web, and everywhere encodeURIComponent is hailed as the silver bullet. But apparently I'm fighting a different breed of lycanthrope. Does anyone have any suggestions?

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• How do you read a file line by line in your language of choice?

  - by Jon Ericson

  I got inspired to try out Haskell again based on a recent answer. My big block is that reading a file line by line (a task made simple in languages such as Perl) seems complicated in a functional language. How do you read a file line by line in your favorite language? So that we are comparing apples to other types of apples, please write a program that numbers the lines of the input file. So if your input is: Line the first. Next line. End of communication. The output would look like: 1 Line the first. 2 Next line. 3 End of communication. I will post my Haskell program as an example. Ken commented that this question does not specify how errors should be handled. I'm not overly concerned about it because: Most answers did the obvious thing and read from stdin and wrote to stdout. The nice thing is that it puts the onus on the user to redirect those streams the way they want. So if stdin is redirected from a non-existent file, the shell will take care of reporting the error, for instance. The question is more aimed at how a language does IO than how it handles exceptions. But if necessary error handling is missing in an answer, feel free to either edit the code to fix it or make a note in the comments.

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• How to know if all the Thread Pool's thread are already done with its tasks?

  - by mcxiand

  I have this application that will recurse all folders in a given directory and look for PDF. If a PDF file is found, the application will count its pages using ITextSharp. I did this by using a thread to recursively scan all the folders for pdf, then if then PDF is found, this will be queued to the thread pool. The code looks like this: //spawn a thread to handle the processing of pdf on each folder. var th = new Thread(() => { pdfDirectories = Directory.GetDirectories(pdfPath); processDir(pdfDirectories); }); th.Start(); private void processDir(string[] dirs) { foreach (var dir in dirs) { pdfFiles = Directory.GetFiles(dir, "*.pdf"); processFiles(pdfFiles); string[] newdir = Directory.GetDirectories(dir); processDir(newdir); } } private void processFiles(string[] files) { foreach (var pdf in files) { ThreadPoolHelper.QueueUserWorkItem( new { path = pdf }, (data) => { processPDF(data.path); } ); } } My problem is, how do i know that the thread pool's thread has finished processing all the queued items so i can tell the user that the application is done with its intended task?

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• Learning Clojure - What should I know about Java and more.

  - by kartan

  Hello, I have started learning Clojure recently, my main programming language is Ruby and I have no Java experience whatsoever. Which Java standard classes are a must to know when working with Clojure? Obviously Clojure doesn't come with a wrapper for everything and a lot of functionality is provided by Java's libraries. There's like a gazillion of them on javadocs - which ones should I explore? Where do I look for and how do I install third party libraries? In Ruby I'd visit Rubyforge or Rubytoolbox and then just gem install the package I found interesting. Which editor/ide for Clojure would you recommend (with the lowest learning curve)? I am trying to use Netbeans with Enclojure and paradoxally it's my biggest obstacle so far: Each generated project has some xml files, folders, library dependencies etc. the purpose of I have no clue. I am doing some labrepl exercises and wanted to try out some of the bundled libraries separately in a new project, but this simple task I cannot accomplish :/ Are there any clojure community driven blogs with news, code tips etc?

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• Strangely structured xml code finding last value of a certain type using java

  - by Damien.Bell

  Thus the structure is something like this: OasisReportMessagePayloadRTOReport_ItemReport_Data Under report data it's broken into categories: >>Zone >>Type >>Value >>Interval What I need to do is: Get the value if the type is equal to 'myType' and the interval value is the LARGEST. So an example of the xml might be (under report_data): OasisReport MessagePayload RTO REPORT_ITEM REPORT_DATA <zone>myZone1</zone> -- This should be the same in all reports since I only get them for 1 zone <type>myType</type> --This can change from line to line <value>12345</value>--This changes every interval <Interval>122</Interval> -- This is essentially how many 5 minute intervals have taken place since the beginning of a day, finding the "max" lets me know it's the newest data. Thereby I want to find stuff of "MyType" for the "max" interval and pull the Value (into a string, or a double, if not I can convert from string. Can someone help me with this task? Thanks! Note: I've used Xpath to handle things like this in the past, but it seems outlandish for this... as it's SO complex (since not all the reports live in the same report_item, and not all the types are the same in each report)

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• Database Functional Programming in Clojure

  - by Ralph

  "It is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail." - Abraham Maslow I need to write a tool to dump a large hierarchical (SQL) database to XML. The hierarchy consists of a Person table with subsidiary Address, Phone, etc. tables. I have to dump thousands of rows, so I would like to do so incrementally and not keep the whole XML file in memory. I would like to isolate non-pure function code to a small portion of the application. I am thinking that this might be a good opportunity to explore FP and concurrency in Clojure. I can also show the benefits of immutable data and multi-core utilization to my skeptical co-workers. I'm not sure how the overall architecture of the application should be. I am thinking that I can use an impure function to retrieve the database rows and return a lazy sequence that can then be processed by a pure function that returns an XML fragment. For each Person row, I can create a Future and have several processed in parallel (the output order does not matter). As each Person is processed, the task will retrieve the appropriate rows from the Address, Phone, etc. tables and generate the nested XML. I can use a a generic function to process most of the tables, relying on database meta-data to get the column information, with special functions for the few tables that need custom processing. These functions could be listed in a map(table name -> function). Am I going about this in the right way? I can easily fall back to doing it in OO using Java, but that would be no fun. BTW, are there any good books on FP patterns or architecture? I have several good books on Clojure, Scala, and F#, but although each covers the language well, none look at the "big picture" of function programming design.

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• Packaging reference documentation with jar file

  - by soren.enemaerke

  We are porting our .NET library to a java equivalent and is now looking at how to distribute this port. Packaging the classes into a jar-file seems like best practice and we would then ship this jar file in a zip along with some license terms. But what about the documentation? In .NET land it seems like best practice to distribute the xml file that can be consumed by tooling (Visual Studio) but we can't seem to find such best practices for java. We have javadoc comments on our public classes and interfaces, so we are just looking for a way to generate and distribute these comments in a way that is developer friendly (we're thinking easily consumed from various IDEs). What are developers expecting and how do you best deliver this? We would really prefer to bundle the documentation along with the jar file and not have to host the documentation on our website EDIT: We would like for our documentation to appear inside the java IDEs so we want to provide the documentation in a way that integrates into the IDEs as gracefully as possible. In .NET land this is as an xml file placed next to the .dll file, but is there a similar concept for jar files that enables the integration into tooling? PS: We are developing in Eclipse and have an ant task doing the building and jar-file packaing in our automated build.

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• Improve Application Performace

  - by Gtest

  Hello, Want To Improvide Performace Of C#.Net Applicaiton.. In My Application I am using Third Party Interop/Dll To Process .doc Files. It's a Simple Operation, Which Pass Input/Output FilePath to Interop dll ...& dll will execute text form input file. To Improve Performace I have Tried, Execute 2 therad to process 32 files.(each Thread process 16 files) Execute application code by creating 2 new AppDomains(each AppDomain Code process 16 files) Execute Code Using TPL(Task Parellel Library) But all options take around same time (32 sec) to process 32 files.Manually process tooks same 32 sec to process 32 files. Just tried one thing ..when i have created sample exe to process 16 files as input & output for refrence PAth given in TextBox. ..I open 2 exe instance to process. 1 exe has differnt 16 input files & output Created with input file path 2 exe has differnt 16 input files & output Created with input file path When i click on start button of both exe ..it use 100% cpu & Utilize both core significantly & Process Completed within 16 sec for 32 files. Can we provide this kind of explicit prallism to Improve my applicaiton Peformace? Thanks.

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• How do I start up an NSRunLoop, and ensure that it has an NSAutoreleasePool that gets emptied?

  - by Nick Forge

  I have a "sync" task that relies on several "sub-tasks", which include asynchronous network operations, but which all require access to a single NSManagedObjectContext. Due to the threading requirements of NSManagedObjectContexts, I need every one of these sub-tasks to execute on the same thread. Due to the amount of processing being done in some of these tasks, I need them to be on a background thread. At the moment, I'm launching a new thread by doing this in my singleton SyncEngine object's -init method: [self performSelectorInBackground:@selector(initializeSyncThread) withObject:nil]; The -initializeSyncThread method looks like this: - (void)initializeSyncThread { self.syncThread = [NSThread currentThread]; self.managedObjectContext = [(MyAppDelegate *)[UIApplication sharedApplication].delegate createManagedObjectContext]; NSRunLoop *runLoop = [NSRunLoop currentRunLoop]; [runLoop run]; } Is this the correct way to start up the NSRunLoop for this thread? Is there a better way to do it? The run loop only needs to handle 'performSelector' sources, and it (and its thread) should be around for the lifetime of the process. When it comes to setting up an NSAutoreleasePool, should I do this by using Run Loop Observers to create the autorelease pool and drain it after every run-through?

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• How to check the backtrace of a "USER process" in the Linux Kernel Crash Dump

  - by Biswajit

  I was trying to debug a USER Process in Linux Crash Dump. The normal steps to go to the crash dump are: Go to the path where the dump is located. Use the command crash kernel_link dump.201104181135. Where kernel_link is a soft link I have created for vmlinux image. Now you will be in the CRASH prompt. If you run the command foreach <PID Of the process> bt Eg: crash> **foreach 6920 bt** **PID: 6920 TASK: ffff88013caaa800 CPU: 1 COMMAND: **"**climmon**"**** #0 [ffff88012d2cd9c8] **schedule** at ffffffff8130b76a #1 [ffff88012d2cdab0] **schedule_timeout** at ffffffff8130bbe7 #2 [ffff88012d2cdb50] **schedule_timeout_uninterruptible** at ffffffff8130bc2a #3 [ffff88012d2cdb60] **__alloc_pages_nodemask** at ffffffff810b9e45 #4 [ffff88012d2cdc60] **alloc_pages_curren**t at ffffffff810e1c8c #5 [ffff88012d2cdc90] **__page_cache_alloc** at ffffffff810b395a #6 [ffff88012d2cdcb0] **__do_page_cache_readahead** at ffffffff810bb592 #7 [ffff88012d2cdd30] **ra_submit** at ffffffff810bb6ba #8 [ffff88012d2cdd40] **filemap_fault** at ffffffff810b3e4e #9 [ffff88012d2cdda0] **__do_fault** at ffffffff810caa5f #10 [ffff88012d2cde50] **handle_mm_fault** at ffffffff810cce69 #11 [ffff88012d2cdf00] **do_page_fault** at ffffffff8130f560 #12 [ffff88012d2cdf50] **page_fault** at ffffffff8130d3f5 RIP: 00007fd02b7e9071 RSP: 0000000040e86ea0 RFLAGS: 00010202 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007fd02b7e9071 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000040e86ec0 RBP: 0000000040e87140 R8: 0000000000000800 R9: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 00007fff16ec43d0 R13: 00007fd02bcadf00 R14: 0000000040e87950 R15: 0000000000001000 ORIG_RAX: ffffffffffffffff CS: 0033 SS: 002b If you check the above backtrace it shows the kernel functions used for scheduling/handling page fault but not the functions that were executed in the USER process (here eg. climmon). So I am not able to debug this process as I am not able to see the functions executed in that process. Can any one help me with this case?

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