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• Whats the difference between Paxos and W+R>=N in Cassandra?

  - by user1128016

  Dynamo-like databases (e.g. Cassandra) provide ability to enforce consistency by means of quorum, i.e. a number of synchronously written replicas (W) and a number of replicas to read (R) should be chosen in such a way that W+RN where N is a replication factor. On the other hand, PAXOS-based systems like Zookeeper are also used as a consistent fault-tolerant storage. What is the difference between these two approaches? Does PAXOS provide guarantees that are not provided by W+RN schema?

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• Best approach to create a security environment in Java

  - by Tom Brito

  I need to create a desktop application that will run third party code, and I need to avoid the third party code from export by any way (web, clipboard, file io) informations from the application. Somethig like: public class MyClass { private String protectedData; public void doThirdPartyTask() { String unprotedtedData = unprotect(protectedData); ThirdPartyClass.doTask(unprotectedData); } private String unprotect(String data) { // ... } } class ThirdPartyClass { public static void doTask(String unprotectedData) { // Do task using unprotected data. // Malicious code may try to externalize the data. } } I'm reading about SecurityManager and AccessControler, but I'm still not sure what's the best approach to handle this. What should I read about to do this implementation?

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• HSQLDB and in-memory files

  - by lewap

  Is it possible to setup HSQLDB in a way, so that the files with the db information are written into memory instead of using actual files? I want to use hsqldb to export some data structures together with hibernate mappings. Is is, however, not possible to write temporary files, so that I need to generate the files in-memory and return a stream with their contents as a response. Setting hsqldb to use nio seems not to be a solution, because there is no way to get hold of those files before they get written onto the filesystem. What I'm thinking of is a protocol handler for hsqldb, but I didn't find a suitable solution yet. Just to describe in other words: A hack solution would be to pass hsqldb a stream or several streams. It would then during its operation write data into those streams. After all data is written, the user of the db could then use those streams to send it back over the network.

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• javascript: getting two sibling windows communicate

  - by romuwild

  i have 2 windows: window A and window B. -window A and window B have same domain -window A and window B doesn't have any parent window. first question: -is it possible for window A to get a reference of window B? second question: -what is the most elegant way to make window A notify something to window B? (modern browser supporting HTML5 restriction is not a problem) 2 ways i am aware of doing this: -messaging by server: where window B regulary asks the server if window A has notified something -messaging by local data (HTML5): when window A wants to notify something it changes the local data, window B regulary checks the local data for any change. but the 2 ways are not so elegant. for example it would be nice to get an reference of window B and using window.postMessage() (HTML5) ultimate goal is to make something like facebook where if you open 4 facebook tabs, and chat in one tab, the chat is actualized on every facebook tab, which is neat! thanks folks!

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• UNIX FIFO: How to allow only one writer/reader pair to use a FIFO?

  - by Max Krug

  Hi! I've written two programs: the first, the "writer", creates a FIFO and writes data into it. The second one, the "reader" runs in background and looks for data in the FIFO. Once data is there, the reader reads it out. If I start e.g. two writers and two readers, they all can write/read into/from the same FIFO. How can I restrict it for 3rd and 4th readers/writers to use the FIFO and allow only one writer and one reader to use the FIFO? thanks a lot. -- kind regards, Max Krug

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• Best way to show a loading screen in an iPhone app?

  - by pkulak

  I'm building what is essentially a web app. Every piece of data has to be fetched from a web API. So, every UITableView that I show takes some amount of time to fill with data and I'm struggling to find a good way to show the user a loading screen. Right now I'm popping up an action sheet, but that just seems a bit wrong. Ideally, I'd popup up a blank view over the tableview with "Loading..." on it, then fade it away when the data comes in, but I can't think of a way to do that in 8 places in my app without massive code duplication.

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• How to skip extra lines before the header of a tab delimited delimited file in R

  - by Michael Dunn

  The software I am using produces log files with a variable number of lines of summary information followed by lots of tab delimited data. I am trying to write a function that will read the data from these log files into a data frame ignoring the summary information. The summary information never contains a tab, so the following function works: read.parameters <- function(file.name, ...){ lines <- scan("tmp.log", what="character", sep="\n") first.line <- min(grep("\\t", lines)) return(read.delim(file.name, skip=first.line-1, ...)) } However, these logfiles are quite big, and so reading the file twice is very slow. Surely there is a better way?

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• iPhone: Error and error handling confusion in comparison.

  - by Mr. McPepperNuts

  NSArray *results = [managedObjectContext executeFetchRequest:request error:&error]; if(results == nil){ NSLog(@"No results found"); searchObj = nil; }else{ if ([[[results objectAtIndex:0] name] caseInsensitiveCompare:passdTextToSearchFor] == 0) { NSLog(@"results %@", [[results objectAtIndex:0] name]); searchObj = [results objectAtIndex:0]; }else { NSLog(@"No results found"); searchObj = nil; } } The code above compares data a user enters to data pulled from a database. If I enter data which is in the database; it works. But if I enter complete gibberish it returns the error below instead of "No results found." *** WebKit discarded an uncaught exception in the webView:shouldInsertText:replacingDOMRange:givenAction: delegate: <NSRangeException> *** -[NSCFArray objectAtIndex:]: index (0) beyond bounds (0) The results array being null should be accounted for during the checks in the above code, no?

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• XML file creation Using XDocument

  - by Pramodh

  i've a list (List< string) "sampleList" which contains Data1 Data2 Data3... How to create an XML file using XDocument by iterating the items in the list in c sharp. The file structure is like <file> <name="samplee"/> <date=" "/> <info> <data value="Data1"/> <data value="Data2"/> <data value="Data3"/> </info> </file please help me to do this

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• Trigger for insert table

  - by shanks

  I have sql server 2005 and need to create trigger for insert query. I have Table naemd as "Log" with column named as UserID,UserName,LogDate,LogTime and want to transfer data into other table named as "DataTable" with same column name. I have created trigger GO SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TRIGGER [dbo].[Transfer] on [dbo].[Log] AFTER INSERT AS BEGIN insert into DataTable (UserID,UserName,LogDate,LogTime) SELECT UserID,UserName,LogDate,LogTime FROM Log where UserID not in(select UserID from DataTable) END New Data is updated on daily basis in "Log" table and so i want to transfer new data from Log table to DataTable with trigger.Execution time is very high and so no output .

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• Problem about socket communication

  - by Ahmet Altun

  I have two separate socket projects in VS.NET. One of them is sender, other one is receiver. After starting receiver, i send data from sender. Although send method returns 13 bytes as successfully transferred, the receiver receives 0 (zero). The receiver accepts sender socket and listens to it. But cannot receive data. Why? P.S. : If sender code is put in receiver project, receiver can get data, as well.

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• Issues rendering image in flash via Context.Response.Write C# asp.

  - by Justin

  I am having an issue rendering images in flash via a character array. I am sending it from a webhandler via Context.Response.Write as a Base64CharacterArray. It functions 100% properly in a windows environment, however when using a Mac the image data is not retrieved correctly causing the image to appear incorrectly. It does not affect the data,however as it is rendered properly in a player which accesses the data via a webservice. I am at the end of my rope on this one. Anything will help. You can find an example at the following url http://www.discoverirelandtoday.com/photoalbum/Public/Main.aspx Thanks

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• Visual Studio 2008 profiler analysis - missing time

  - by Scott Vercuski

  I ran the Visual Studio 2008 profiler against my ASP.NET application and came up with the following result set. CURRENT FUNCTION TIME (msec) ---------------------------------------------------|-------------- Data.GetItem(params) | 10,158.12 ---------------------------------------------------|-------------- Functions that were called by Data.GetItem(params) TIME (msec) ---------------------------------------------------|-------------- Model.GetSubItem(params) | 0.83 Model.GetSubItem2(params) | 0.77 Model.GetSubItem3(params) | 0.76 etc. The issue I'm facing is that the sum of the Functions called by Data.GetItem(params) do not sum up to the 10,158.12 msec total. This would lead me to believe that the bulk of the time is actually spent executing the code within that method. My question is ... does Visual Studio provide a way to analyze the method itself so I can see which sections of code are taking the longest? if it does not are there any recommended tools to do this? or should I start writing my own timing scripts? Thank you

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• Question about the lifecycle of a simple Android application

  - by jul

  Hi, I've got a simple application with 3 activities: -the first contains a search box which calls a web service and show the results (restaurants) below in a listview -when a restaurant is clicked another activity is started showing the description of the restaurant and a button "show map" -when the button "show map" is clicked, guess what, the map is shown in a third activity. All the data is loaded in the first activity by a web service (restaurant descriptions and coordinates), and data required by each activity is passed in a bundle using "intent.putExtra". Now everything seems to run smoothly when clicking on the back button (eg. clicking on the back button from the map resumes the "restaurant description" activity with all data set properly), while I haven't done anything about the lifecycle yet. Why? Are all variables saved automatically? Should I use onSaveInstanceState() and onRestoreInstanceState() anyway? Thanks Jul

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• i2c on silicon image c8051f32x (using USBXpress)

  - by tosa

  I have the I2C (SMBus) working properly in this uC and have a VB GUI which can communicate over USB (using USBXpress) and do I2C transactions from the uC to a separate IC. The problem is that I am having the uC poll a register on the IC every 1s. When I do an asynchronous GUI I2C transaction, every once in a while, I believe it collides with the polling I2C transaction and all the I2C data gets shifted at the GUI (i.e., register 0x00's data shows up on register 0x01) . The I2C data in the IC looks correct (by spying on the I2C bus with a LA). What exactly is happening and how can I fix this?

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• Problems and solution for Developing a connected web and desktop application?

  - by Taz

  hi, I am trying to develop a web application(Using ASP.NET and c#) that uses a specific database hosted on web server. I will have another desktop application that will use a local database. Both databases have same structure and data at start up. Then databases will change when users add data to web application and an employee adds data to the desktop application. After a while I have to sync both databases. What will be best way to do this? Is there any opensource example/ starter kit to start with? Thanks.

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• Which Happens First? Anyone Know Exactly How The Apache Server Will Handle This Request?

  - by user310594

  Hello, To keep things simple, please allow the "assumption" that some code requires the use of a full URL, even though the domain is on the same server, i.e. a simple file path cannot be used. TCP/IP?? Question: If a form action target = "http://this-full-URL.com/postdata" (for example) and that URL is also on the same server, then which happens first? A) Data is sent "out onto the web", and then returns to the same server, or B) Before sending any (possibly sensitive) data, the server (Linux, Apache, PHP), first "discovers" the target address is local, so (clearly) no data is sent over the net? Thank you.

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• Integration of Magento with third party CRM, POS and ERP solutions

  - by SIA

  Hi there, First of all I would like to Thank the Varien Company for providing the best ecommerce solution and free community edition. I am very excited since i started knowing about magento. I am a web developer and very much interested. I have some concerns about the Integration of Magento with other CRM,ERP systems. How is it possible to integrate Magento with any other Industry standard CRM and ERP system? How can i fetch the data from a ERP and update Magento database, like transactiona replication. Is this possible? And Whats the right way to do it? Also, How can i integrate Magento with POS? Is it possible to have bi-directional data update between Magento and Industry Standard POS? I hope I have stated all my doubts and made it clear. I would be thankful if someone guides me to do the integration, the Right way. Thanks and Regards SIA

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• Creating a unique key based on file content in python

  - by Cawas

  I got many, many files to be uploaded to the server, and I just want a way to avoid duplicates. Thus, generating a unique and small key value from a big string seemed something that a checksum was intended to do, and hashing seemed like the evolution of that. So I was going to use hash md5 to do this. But then I read somewhere that "MD5 are not meant to be unique keys" and I thought that's really weird. What's the right way of doing this? edit: by the way, I took two sources to get to the following, which is how I'm currently doing it and it's working just fine, with Python 2.5: import hashlib def md5_from_file (fileName, block_size=2**14): md5 = hashlib.md5() f = open(fileName) while True: data = f.read(block_size) if not data: break md5.update(data) f.close() return md5.hexdigest()

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• Random List of millions of elements in Python Efficiently

  - by eWizardII

  Hello, I have read this answer potentially as the best way to randomize a list of strings in Python. I'm just wondering then if that's the most efficient way to do it because I have a list of about 30 million elements via the following code: import json from sets import Set from random import shuffle a = [] for i in range(0,193): json_data = open("C:/Twitter/user/user_" + str(i) + ".json") data = json.load(json_data) for j in range(0,len(data)): a.append(data[j]['su']) new = list(Set(a)) print "Cleaned length is: " + str(len(new)) ## Take Cleaned List and Randomize it for Analysis shuffle(new) If there is a more efficient way to do it, I'd greatly appreciate any advice on how to do it. Thanks,

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• REST - why we need million urls and different HTTP request?

  - by Andre

  I asked this question. But I still don't understand why we need to utilize different HTTP requests: DELETE/PUT/POST/GET in order to build nice API Wouldn't it be a lot simpler to pass all information in request parameters and have a SINGLE ENTRY-POINT for your api?: GET www.example.com/api?id=1&method=delete&returnformat=JSON GET www.example.com/api?id=1&method=delete&returnformat=XML or POST www.example.com/api {post data: id=1&method=delete&returnformat=JSON} POST www.example.com/api {post data: id=1&method=delete&returnformat=XML} and then - we can handle all methods and data internally without the need for hundreds of urls... how would you call this type of API - It's not REST apparently, it's not SOAP. then - what is it? UPDATE I'm not proposing any new standards here. I merely asking a question in order to better understand why web services work the way they work.

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• Why does UMN-Mapserver shows an ERDAS Image-File (.img) as white shape?

  - by Mnementh

  I want to render an ERDAS-Image-file (suffix .img) with the UMN-Mapserver. The data is rendered on the right position and with the correct shape, but all data is white instead of an raster-image. The Image contains many layers. My mapfile looks like this: MAP NAME "Test" WEB METADATA "wms_title" "test" "WMS_SRS" "epsg:31466 epsg:31467 epsg:31468 epsg:31469 epsg:4326 epsg:25832 epsg:3035" END LOG "test.log" IMAGEPATH "." END SHAPEPATH "." PROJECTION "init=epsg:32632" END LAYER NAME "testlayer" TYPE RASTER DATA "test.img" STATUS ON OFFSITE 0 0 0 END OUTPUTFORMAT NAME png DRIVER "GD/PNG" MIMETYPE "image/png" IMAGEMODE RGBA END END

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• Codeigniter database update

  - by Carry All

  The table is like this and I want to update DecryptionDate by specify ArchiveID and RecipientID this is my code $this->load->database(); $date = date("Y-m-d H:i:s"); $data = array('DecryptionDate' => $date); $array = array('ArchiveID'=>$archiveID.'','RecipientID'=>$userID.''); $this->db->where($array); $this->db->update('log', $data); if ($this->db->affected_rows() > 0) { echo "SUCCESS"; } else { echo "FAIL"; } my problem is I can update the data only when $archiveID is 911 and $userID is test01 but the program fail to update when $archiveID is 911 and $userID is test02

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• ASP.net repeater, scroll 3 at a time

  - by Christo Fur

  I have a list of data that I need to display in a web page 3 at a time The first needs to be displayed in a div called "left" , the second in a div called "centre" and the third in a div called "right". And I need to be able to scroll through the data with a pager. And so the next 3 results will be displayed in a similar way, and so on till the end of the data set Obviously the alternating templates in the repeater are not suitable for this. Is there a smarter way to achieve this?

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• From me friends, know who is already using the app

  - by Toni Michel Caubet

  I got working to get all friends from 'me' user, like this: FB.api('/me/friends?fields=id,name,updated_time&date_format=U&<?=$access_token?>', {limit:3, function(response){ console.log('Friend name: '+response.data[0].name); } ); But i need to get if the user is in the app already or not, how can I alter the query to get an extra row in the object 'is_in_app' true/false? FB.api('/me/friends?fields=id,name,updated_time&date_format=U&<?=$access_token?>', {limit:3, function(response){ var text = 'is not in app'; if(response.data[0].is_in_app == true) text = 'is in app!!'; console.log('Friend name: '+response.data[0].name + ' ' + text); } ); How can i achieve this?

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