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• Passing Extras and screen rotation

  - by Luis A. Florit

  This kind of questions appear periodically. Sorry if this has been covered before, but I'm a newbie and couldn't find the appropriate answer. It deals with the correct implementation of communication between classes and activities. I made a gallery app. It has 3 main activities: the Main one, to search for filenames using a pattern; a Thumb one, that shows all the images that matched the pattern as thumbnails in a gridview, and a Photo activity, that opens a full sized image when you click a thumb in Thumbs. I pass to the Photo activity via an Intent the filenames (an array), and the position (an int) of the clicked thumb in the gridview. This third Photo activity has only one view on it: a TouchImageView, that I adapted for previous/next switching and zooming according to where you shortclick on the image (left, right or middle). Moreover, I added a longclick listener to Photo to show EXIF info. The thing is working, but I am not happy with the implementation... Some things are not right. One of the problems I am experiencing is that, if I click on the right of the image to see the next in the Photo activity, it switches fine (position++), but when rotating the device the original one at position appears. What is happening is that Photo is destroyed when rotating the image, and for some reason it restarts again, without obeying super.onCreate(savedInstanceState), loading again the Extras (the position only changed in Photo, not on the parent activities). I tried with startActivityForResult instead of startActivity, but failed... Of course I can do something contrived to save the position data, but there should be something "conceptual" that I am not understanding about how activities work, and I want to do this right. Can someone please explain me what I am doing wrong, which is the best method to implement what I want, and why? Thanks a lot!!!

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• Configure nHibernate for multiple-project solution

  - by NoOne

  Hello, Im doing a project with C# winforms. This project is composed by: Client project: Windows Forms where user will do CRUD operations on the models; Server project; Common Project: This project will hold the models (in the image only have the model Item); ListSingleton: Remote Object that will do the operations on the models; I already have all the communication working, but now I need to work on the persistence of the data in a mysql database. I was trying to use nHibernate but I’m having some troubles. My main problem is how to organize my hibernate configuration. In which project do I keep the mapping? Common project? In which project do I keep the hibernate configuration file (App.config)? ListSingleton project? In which project do I do this: Configuration cfg = new Configuration(); cfg.AddXmlFile("Item.hbm.xml"); ISessionFactory factory = cfg.BuildSessionFactory(); ISession session = factory.OpenSession(); ITransaction transaction = session.BeginTransaction(); Item newItem = new Item("BLAA"); // Tell NHibernate that this object should be saved session.Save(newItem); // commit all of the changes to the DB and close the ISession transaction.Commit(); session.Close(); In the ListSingleton project? Altho I had reference to the Common Project in the ListSingleton I keep getting error in the addXml line… My mapping is correct because I tried with a one-project solution and it worked :X

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• Android Service setForeground While Display Sleeps

  - by c12

  I have a background Android Service that's purpose is to communicate with another device (non-phone) using a Bluetooth socket. Everything works fine except that the service gets stopped and restarted by the OS when the phone display is sleeping. This restart sometimes leaves a 15-20 minute gaps where there is no communication between the Service and the Bluetooth device and I need to be able to query the device every minute. Is startForeground the proper approach? Attempted to use: startForeground(int, Notification) //still see gaps when phone sleeps Service: public class ForegroundBluetoothService extends Service{ private boolean isStarted = false; @Override public void onDestroy() { super.onDestroy(); stop(); } /** * @see android.app.Service#onBind(android.content.Intent) */ @Override public IBinder onBind(Intent intent) { return null; } /** * @see android.app.Service#onStartCommand(android.content.Intent, int, int) */ @Override public int onStartCommand(Intent intent, int flags, int startId) { loadServiceInForeground(); return(START_STICKY); } private void loadServiceInForeground() { if (!isStarted) { isStarted=true; Notification notification = new Notification(R.drawable.icon, "Service is Running...", System.currentTimeMillis()); Intent notificationIntent = new Intent(this, MainScreen.class); PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, notificationIntent, 0); notification.setLatestEventInfo(this, "Notification Title", "Service is Running...", pendingIntent); startForeground(12345, notification); try{ queryTheBluetoothDevice(); } catch(Exception ex){ ex.printStackTrace(); } } } private void stop() { if (isStarted) { isStarted=false; stopForeground(true); } } }

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• Process data BEFORE a 301 Redirect?

  - by Jesse

  So, I've been working on a PHP link shortener (I know, just what the world needs). Basically when the page loads, php determines where it needs to go and sends a 301 Header to redirect the browser, like so... Header( "HTTP/1.1 301 Moved Permanently" ); header("Location: http://newsite.com"; Now, I'm trying to add some tracking to my redirects and insert some custom analytics data into a MySQL table before the redirect happen. It works perfectly if I don't specify the a redirect type and just use: header("Location: http://newsite.com"; But, of course as soon as you add in the 301 header, nothing else gets processed. Actually, on the first request, it sends the data to MySQL, but on any subsequent requests there's no communication with the database. I assume it's a browser caching issue, once it's seen the 301 it decides they're no reason to parse anything on future requests. But, does anyone know if there's any way to get around this? I'd really like to keep it as a 301 for SEO purposes (I believe if you don't specify it sends a 404 by default?). I thought about using .htaccess to prepend a file to the page that will do the MySQL work, but with the 301, wouldn't that just get ignored as well? Anyway, I'm not sure if there's any solution other than using a different type of redirect, but I'm ready to give up just yet. So, any suggestions would be much appreciated. Thanks!

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• Loading GWT Messages from a Database

  - by Lars Tackmann

  In GWT one typically loads i18n strings using a interface like this: public interface StatusMessage extends Messages { String error(String username); : } which then loads the actual strings from a StatusMessage.property file: error=User: {0} does not have access to resource This is a great solution, however my client is unbendable in his demand for putting the i18n strings in a database so they can be changed at runtime (though its not a requirement that they be changed realtime). One solution is to create a async service which takes a message ID and user locale and returns a string. I have implemented this and find it terribly ugly (and it introduces a huge amount of extra communication with the server, plus it makes property placeholder replacement rather complicated). So my question is this, can I in some nice way implement a custom message provider that loads the messages from the backend in one big swoop (for the current user session). If it can also hook into the default GWT message mechanism, then I would be completely happy (i.e. so I can create a interface like above and keep using the the nice {0}, {1}... property replacement format). Other suggestions for clean database driven messages in GWT are also welcome.

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• How to model and handle presentation DTO's to abstract from complicated domain model?

  - by arrages

  Hi I am developing an application that needs to work with a complex domain model using Hibernate. This application uses Spring MVC and using the domain objects in the presentation layer is very messy so I think I should use DTO's that go to and from my service layer so that these match what I need in my views. Now lets assume I have a CarLease entity whose properties are not simple java primitives but it's composed with other entities like Make, Model, etc public class CarLease { private Make make; Private Model model; . . . } most properties are in this fashion and they are selectable using drop down selects on the jsp view, each will post back an ID to the controller. Now considering some standard use cases: create, edit, display How would you go about modeling the presentation DTO's to be used as form backing objects and communication between presentation and service layers?? Would you create a different DTO for each case (create, edit, display), would you make DTO's for the complex attributes? if so where would you translate the ID to entity? how and where would you handle validation, DTO/Domain assembly, what would you return from service layer methods? (create, edit, get) As you can see, I now I will benefit by separating my view from the domain objects (very complex with lots of stuff I don't need.) but I am having a hard time finding any real world examples and best practices for this. I need some architecture guidance from top to bottom, please keep in mind I will use Spring MVC in case that may leverage on your anwser. thanks in advance.

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• Functioning Socket read no longer works when called in AsyncTask

  - by bibismcbryde

  I'm making an app that sends a string to a server over a socket and then reads the output after the server has processed that data. It worked perfectly when it was my foreground task, but I have since used AsyncTask to show a process dialog while the socket communication runs in the background, and things start breaking after I read the output from the server and then try to close the socket. private class Progressor extends AsyncTask<String, Void, Void> { ProgressDialog dialog; protected void onPreExecute() { dialog = ProgressDialog.show(ClearTalkInputActivity.this, "Loading..", "Analyzing Text", true, false); } protected Void doInBackground(String... strings) { String language = strings[0].toLowerCase(); String the_text = strings[1]; Socket socket = null; DataOutputStream dos = null; DataInputStream dis = null; try { socket = new Socket(my_ip, port); dos = new DataOutputStream(socket.getOutputStream()); dis = new DataInputStream(socket.getInputStream()); dos.writeUTF(language+"****"+the_text); String in = ""; while (in.indexOf("</content>") < 0) { in += dis.readUTF(); } socket.close(); save_str(OUTPUT_KEY, in); } catch (UnknownHostException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { if (socket != null) { try { socket.close(); } catch (IOException e) { e.printStackTrace(); } } } if (dos != null) { try { dos.close(); } catch (IOException e) { e.printStackTrace(); } } if (dis != null) { try { dis.close(); } catch (IOException e) { e.printStackTrace(); } } return null; } protected void onPostExecute() { if (dialog.isShowing()) dialog.dismiss(); startActivity(new Intent (output_intent)); } }

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• calling same function on different buttons not loaded yet

  - by Jordan Faust

  I can not get this to work for every button and I cannot find anything explaining why. I guessing it is something small that I am missing $(document).ready(function() { // delete the selected row from the database $(document).on('click', '#business-area-delete-button', { model: "BusinessArea" }, deleteRow); $(document).on('click', '#business-type-delete-button', { model: "BusinessType" }, deleteRow); $(document).on('click', '#client-delete-button', { model: "Client" }, deleteRow); $(document).on('click', '#client-type-delete-button', { model: "ClientType" }, deleteRow); $(document).on('click', '#communication-channel-type', { model: "CommunicationChannelType" }, deleteRow); $(document).on('click', '#parameter-type-delete-button', { model: "ParameterType" }, deleteRow); $(document).on('click', '#validation-method-delete-button', { model: "ValidationMethod" }, deleteRow); } the event function deleteRow(event){ $.ajax( { type:'POST', data: { id: $(".delete-row").attr("id") }, url:"/mysite/admin/delete" + event.data.model, success:function(data,textStatus){ $('#main-content').html(data); }, error:function(XMLHttpRequest,textStatus,errorThrown){ jQuery('#alerts').html(XMLHttpRequest.responseText); }, complete:function(XMLHttpRequest,textStatus){ placeAlerts() } } ); return false }; This works only for a the button with id validation-method-delete-button. I use document and not the button its self because the button is contained in a template that is loaded later via ajax. I have this working for a similar function that is selecting a row in a table however I am not attempting to pass data in that scenario.

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• Is it possible to use a serial port like session in c#?

  - by Pandiya Chendur

  I am using serial port communication in my asp.net webform application... private bool sendSMS(int portNo, string mobNo, string details) { try { SerialPort SerialPort1 = new SerialPort(); SerialPort1.PortName = "COM" + portNo.ToString(); SerialPort1.BaudRate = 9600; SerialPort1.Parity = Parity.None; SerialPort1.DataBits = 8; SerialPort1.StopBits = StopBits.One; SerialPort1.RtsEnable = true; SerialPort1.DtrEnable = true; SerialPort1.Encoding.GetEncoder(); SerialPort1.ReceivedBytesThreshold = 1; SerialPort1.NewLine = Environment.NewLine; SerialPort1.Open(); SerialPort1.Write("AT" + SerialPort1.NewLine); Sleep(500); SerialPort1.Write("AT+CMGF=1" + SerialPort1.NewLine); Sleep(500); SerialPort1.Write("AT+CMGS=" + (char)34 + mobNo + (char)34 + SerialPort1.NewLine); Sleep(1000); SerialPort1.Write(details + (char)26); Sleep(2000); SerialPort1.Close(); } catch { } return true; } This method works when i send i single message... But when want to send sms in bulk opening and closing port everytime is not a good idea... So my question is it possible to use a serial port like session in c#?... When i open a port i want it to be open for 1 hour and then if my time expires i want to close the port and open it the next time... Any suggestion...

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• Flash browser game - HTTP + PHP vs Socket + Something else

  - by Maurycy Zarzycki

  I am developing a non-real time browser RPG game (think Kingdom of Loathing) which would be played from within a Flash app. At first I just wanted to make the communication with server using simply URLLoader to tell PHP what I am doing, and using $_SESSION to store data needed in-between request. I wonder if it wouldn't be better to base it on a socket connection, an app residing on a server written in Java or Python. The problem is I have never ever written such an app so I have no idea how much I'd have to "shift" my thoughts from simple responding do request (like PHP) to continuously working application. I won't hide I am also concerned about the memory and CPU usage of such Server app, when for example there would be hundreds of users connected. I've done some research. I have tried to do some research, but thanks to my nil knowledge on the sockets subject I haven't found anything helpful. So, considering the fact I don't need real time data exchange, will it be wise to develop the server side part as socket server, not in plain ol' PHP?

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• Please suggest other ways of communicating between server & client.

  - by Geo

  I'm writing a TCP chat server ( programming language does not mather ). It's a school project for my nephew, so it won't be released, and all questions I'm asking are just for my knowledge :). . Some of the things it will support: chatting between users ( doh ), it will be multithreaded sending each other files I know I could easily get away with all the stuff above if I go with serialization, and just send objects from client to server and back. But, if I do that, it will be limited to a specific programming language ( meaning clients written in other programming languages may not be able to deserialize the objects ). What would be the way to go so that other clients written in other languages could be supported? One way to go, off the top of my head, would be to go in this direction: the server & the client communicate by sending messages & chunks ( in lieu of other names ). Here's what I mean by this: every time the client/server wants to send something ( text message or file ) it will first send a simple text message ( newline terminated ) with the number of the chunks it will send. Example: command 4,20,30,40,50 Where command would be something like instant-message or file,4 would be the number of chunks to be sent, 20 would be the size in bytes of the first chunk, 30 of the 2nd, and so forth. after the message was sent, the client/server will start sending chunks ( of sizes mentioned in the sent message ). What do you think about implementing the client/server communication this way? What better options are there?

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• Response time increasing (worsening) over time with consistent load

  - by NJ

  Ok. I know I don't have a lot of information. That is, essentially, the reason for my question. I am building a game using Flash/Flex and Rails on the back-end. Communication between the two is via WebORB. Here is what is happening. When I start the client an operation calls the server every 60 seconds (not much, right?) which results in two database SELECTS and an UPDATE and a resulting response to the client. This repeats every 60 seconds. I deployed a test version on heroku and NewRelic's RPM told me that response time degraded over time. One client with one task every 60 seconds. Over several hours the response time drifted from 150ms to over 900ms in response time. I have been able to reproduce this in my development environment (my Macbook Pro) so it isn't a problem on Heroku's side. I am not doing anything sophisticated (by design) in the server app. An action gets called, gets some data from the database, performs an AR update and then returns a response. No caching, etc. Any thoughts? Anyone? I'd really appreciate it.

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• Hashing 11 byte unique ID to 32 bits or less

  - by MoJo

  I am looking for a way to reduce a 11 byte unique ID to 32 bits or fewer. I am using an Atmel AVR microcontroller that has the ID number burned in at the factory, but because it has to be transmitted very often in a very low power system I want to reduce the length down to 4 bytes or fewer. The ID is guaranteed unique for every microcontroller. It is made up of data from the manufacturing process, basically the coordinates of the silicone on the wafer and the production line that was used. They look like this: 304A34393334-16-11001000 314832383431-0F-09000C00 Obviously the main danger is that by reducing these IDs they become non-unique. Unfortunately I don't have a large enough sample size to test how unique these numbers are. Having said that because there will only be tens of thousands of devices in use and there is secondary information that can be used to help identify them (such as their approximate location, known at the time of communication) collisions might not be too much of an issue if they are few and far between. Is something like MD5 suitable for this? My concern is that the data being hashed is very short, just 11 bytes. Do hash functions work reliably on such short data?

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• How often should network traffic/collisions cause SNMP Sets to fail?

  - by A. Levy

  My team has a situation where an SNMP SET will fail once every two weeks or so. Since this set happens automatically, we don't necessarily notice it immediately when it fails, and this can result in an inconsistent configuration and associated wailing and gnashing of teeth. The plan is to fix this by having our software automatically retry the SET when it fails. The problem is, we aren't sure why the failure is happening. My (extremely limited) knowledge of SNMP isn't particularly helpful in diagnosing this problem, so I thought I'd ask StackOverflow for some advice. We think that every so often a spike in network traffic will cause the SET to fail. Since SNMP uses UDP for communication, I would think it would be relatively easy for a command to be drowned out if traffic was high for a short period of time. However, I have no idea how common this is. We have a small network with a single cisco router and there are less than a dozen SNMP controlled devices on that network. In addition to the SNMP traffic, there are some status web pages being loaded from the various devices. In case it makes a difference, I believe we are using the AdventNet SNMP API version 4.0.4 for Java. Does it sound reasonable that there will be some SET commands dropped occasionally, or should we be looking for other causes?

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• How to write a generic USB Host Driver for Printers from various vendors?

  - by Ullas

  I want to develop a USB host on an embedded device that will talk to printers from various vendors. Drivers for the vendor specific printers would be available on PC which is ultimately communicating with printer but my device is facilitating this communication and needs to perform the basic handshaking/setup of the printer (i.e, it needs to know when the printer is connected, what are the socket IDs that needs to be opened for CTRL and DATA transmissions etc). All of these printers are supposed to comply with IEEE 1284.4 standards but I see that many of them vary quiet a bit. One approach I have is to take the USB traces of handshaking from each of these printers and write various sections of code respectively (I know, that sounds ridiculous!). Is there a generic way to do this? Is there any available forum where these standard informations are mentioned? For eg: EPSON uses 'EPSON-CTRL' and 'EPSON-DATA' for its control and data services which needs to be provided to get the socket ID for these services. I am pretty sure HPs, Canon's etc would have their own service names as well. As per the standards, this was supposed to be captured in IANA but I dont see anything there. Any help on this would be greatly appreciated. Thanks and regards, Ullas

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• Is a web-server (e.g servlets) a good solution for an IM server?

  - by John

  I'm looking at a new app, broadly speaking an IM application with a strong client-server model - all communications go through a server so they can be logged centrally. The server will be Java in some form, clients could at this point be anything from a .NET Desktop app to Flex/Silverlight, to a simple web-interface using JS/AJAX. I had anticipated doing the server using standard J2EE so I get a thread-safe, multi-user server for 'free'... to make things simple let's say using Servlets (but in practice SpringMVC would be likely). This all seemed very neat but I'm concerned if the stateless nature of Servlets is the best approach. If my memory of servlets (been a year or two) is right, each time a client sent a HTTP request, typically a new message entered by the user, the servlet could not assume it had the user/chat in memory and might have to get it from the DB... regardless it has to look it up. Then it either has to use some PUSH system to inform other members of the chat, or cache that there are new messages, for other clients who poll the server using AJAX or similar - and when they poll it again has to lookup the chat, including new messages, and send the new data. I'm wondering if a better system would be the server is running core Java, and implements a socket-based communication with clients. This allows much more immediate data transfer and is more flexible if say the IM client included some game you could play. But then you're writing a custom server and sockets don't sound very friendly to a browser-based client on current browsers. Am I missing some big piece of the puzzle here, it kind of feels like I am? Perhaps a better way to ask the question would simply be "if the client was browser-based using HTML/JS and had to run on IE7+,FF2+ (i.e no HTML5), how would you implement the server?" edit: if you are going to suggest using XMPP, I have been trying to get my head around this in another question, so please consider if that's a more appropriate place to discuss this specifically.

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• Build system for multi-language project

  - by Epcylon

  I am getting ready to embark on a project mainly for experimenting with languages, but also with a hint of usefulness. It will consist of a server-application, written in Erlang, and client-libraries in a number of languages. Initially I will want to write clients in Java, Ruby and Python. The actual protocol for communication will be Thrift. I'm looking for a build system that will allow me to build the server and all the client libraries in one go, running unit-tests in each language, then packaging up a releasable artifact of some sort in whatever way is the "standard" for each language. That means a Jar for Java, a RubyGem and a distribute/setuptools tarball for Python. Erlang probably has something too, but I'm not yet familiar with that. It should also be able to run the Thrift compiler to generate the various Thrift-stubs in each language. On the pad at the start is Maven. I'm fairly certain Maven can do all I need, but I fear it's too Java-centric, and leaves me with a ton of work for every new language I need to add.

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• subversion: how to manage tweaked files

  - by punk4funk

  Our group is considering moving to SVN. But, I can't seem to find a way to do the following: I need to make minor tweaks locally to about 20 files in the repository w/o having SVN consider them "changed" and included in the commit. (Changes like communication time-outs and logging levels.) Ideally I would want to merge the tweaked files to newer versions in the repository. (Keeping the tweaked local file up-to-date with committed changes form other users.) I can't imagine we're unique in wanting/needing this. Are there best practices around this type of use case? One thing I'm considering is putting all the tweaked files into a branched "tweaked" working copy. Then merging my tweaked files into my "official" working copy. Then using a script, which compares the "tweaked" and "official" working copies, to update my ignore list. The script would also un-ignore and alert me to any files that had tweaks and other changes that, presumably, needed to be committed to the repository. This seems kinda hacky and I can't imagine there's not a better way.

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• What happens if I just add a second IP to a domain?

  - by tntu

  We have two servers that are in constant sync. We have two applications that connect to them. Each app to different server. We devised a new version of those apps that will read a dns entry and get a list of IP addresses and try them in order. Now problem is old apps. We have noticed that some ppl still use the old ones even if we have released the new. If we were to add two IP's to each domain would they receive the IP's in the order we set them or random? Either way it will still work for us but I'm just curious. If first server goes offline will the client application try the other? To be noted for old version: Interruption does not affect in any way the continuation once connection is reestablished. Each communication is independent of previous ones. Applications connect at set intervals of time anywhere between 5 seconds to 1 hour. Connection is done simply using an http post to the URL in question.

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• How to drop/restart a client connection to a flaky socket server

  - by Steve Prior

  I've got Java code which makes requests via sockets from a server written in C++. The communication is simply that the java code writes a line for a request and the server then writes a line in response, but sometimes it seems that the server doesn't respond, so I've implemented an ExecutorService based timeout which tries to drop and restart the connection. To work with the connection I keep: Socket server; PrintWriter out; BufferedReader in; so setting up the connection is a matter of: server = new Socket(hostname, port); out = new PrintWriter(new OutputStreamWriter(server.getOutputStream())); in = new BufferedReader(new InputStreamReader(socket.getInputStream())); If it weren't for the timeout code the request/receive steps are simply: String request="some request"; out.println(request); out.flush(); String response = in.readLine(); When I received a timeout I was trying to close the connection with: in.close(); out.close(); socket.close(); but one of these closes seems to block and never return. Can anyone give me a clue why one of these would block and what would be the proper way to abandon the connection and not end up with resource leak issues?

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• Setting up GCALDaemon in Eclipse

  - by amadib

  Hello, my eventual goal is to be able to use the authentication and communication to a GMail inbox. In my attempt, I stumbled up on GCALDaemon and am trying to set it up as a project within eclipse. However, I am running into problems running the project from the included .launch files. I am receiving the following errors after running with -Dlog4j.debug on log4j: Trying to find [log4j.xml] using context classloader sun.misc.Launcher$AppClassLoader@1ba34f2. log4j: Trying to find [log4j.xml] using sun.misc.Launcher$AppClassLoader@1ba34f2 class loader. log4j: Trying to find [log4j.xml] using ClassLoader.getSystemResource(). log4j: Trying to find [log4j.properties] using context classloader sun.misc.Launcher$AppClassLoader@1ba34f2. log4j: Trying to find [log4j.properties] using sun.misc.Launcher$AppClassLoader@1ba34f2 class loader. log4j: Trying to find [log4j.properties] using ClassLoader.getSystemResource(). log4j: Could not find resource: [null]. log4j:WARN No appenders could be found for logger (org.gcaldaemon.core.Configurator). log4j:WARN Please initialize the log4j system properly. FATAL | Service terminated! Thanks.

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• Still some questions about USB

  - by b-gen-jack-o-neill

  Hi, few days ago I asked here about implementing USB. Now, If I may, would like to ask few more questions, about thing I dind´t quite understood. So, first, If I am right, Windows has device driver for USB interface, for the physical device that sends and receives communication. But what this driver offers to system (user)? I mean, USB protocol is made so its devices are adressed. So you first adress device than send message to it. But how sophisticted is the device controller (HW) and its driver? Is it so sophisticated that it is a chip you just send device adress and data, and it writes the outcomming data out and incomming data to some internal register to be read, or thru DMA directly to memory? Or, how its drivers (SW) really work? Does its driver has some advanced functions like send _data to _device? Becouse I somewhat internally hope there is a way to directly send some data thru USB, maybe by calling USB drivers itself? Is there any good article, tutorial you know about to really explain how all this logic works? Thanks.

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• Question about how AppFabric's cache feature can be used.

  - by Kevin Buchan

  Question about how AppFabric's cache feature can be used. I apologize for asking a question that I should be able to answer from the documentation, but I have read and read and searched and cannot answer this question, which leads me to believe that I have a fundamentally flawed understanding of what AppFabric's caching capabilities are intended for. I work for a geographically disperse company. We have a particular application that was originally written as a client/server application. It’s so massive and business critical that we want to baby step converting it to a better architected solution. One of the ideas we had was to convert the app to read its data using WCF calls to a co-located web server that would cache communication with the database in the United States. The nature of the application is such that everyone will tend to be viewing the same 2000 records or so with only occasional updates and those updates will be made by a limited set of users. I was hoping that AppFabric’s cache mechanism would allow me to set up one global cache and when a user in Asia, for example, requested data that was not in the cache or was stale that the web server would read from the database in the USA, provide the data to the user, then update the cache which would propagate that data to the other web servers so that they would know not to go back to the database themselves. Can AppFabric work this way or should I just have the servers retrieve their own data from the database?

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• Parallel programming, are we not learning from history again?

  - by mezmo

  I started programming because I was a hardware guy that got bored, I thought the problems being solved in the software side of things were much more interesting than those in hardware. At that time, most of the electrical buses I dealt with were serial, some moving data as fast as 1.5 megabit!! ;) Over the years these evolved into parallel buses in order to speed communication up, after all, transferring 8/16/32/64, whatever bits at a time incredibly speeds up the transfer. Well, our ability to create and detect state changes got faster and faster, to the point where we could push data so fast that interference between parallel traces or cable wires made cleaning the signal too expensive to continue, and we still got reasonable performance from serial interfaces, heck some graphics interfaces are even happening over USB for a while now. I think I'm seeing a like trend in software now, our processors were getting faster and faster, so we got good at building "serial" software. Now we've hit a speed bump in raw processor speed, so we're adding cores, or "traces" to the mix, and spending a lot of time and effort on learning how to properly use those. But I'm also seeing what I feel are advances in things like optical switching and even quantum computing that could take us far more quickly that I was expecting back to the point where "serial programming" again makes the most sense. What are your thoughts?

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• .net remoting - Better solution to wait for a service to initialize ?

  - by CitizenInsane

  Context I have a client application (which i cannot modify, i.e. i only have the binary) that needs to run from time to time external commands that depends on a resource which is very long to initialize (about 20s). I thus decided to initialize this resource once for all in a "CommandServer.exe" application (single instance in the system tray) and let my client application call an intermediate "ExecuteCommand.exe" program that uses .net remoting to perform the operation on the server. The "ExecuteCommand.exe" is in charge for starting the server on first call and then leave it alive to speed up further commands. The service: public interface IMyService { void ExecuteCommand(string[] args); } The "CommandServer.exe" (using WindowsFormsApplicationBase for single instance management + user friendly splash screen during resource initializations): private void onStartupFirstInstance(object sender, StartupEventArgs e) { // Register communication channel channel = new TcpServerChannel("CommandServerChannel", 8234); ChannelServices.RegisterChannel(channel, false); // Register service var resource = veryLongToInitialize(); service = new MyServiceImpl(resource); RemotingServices.Marshal(service, "CommandServer"); // Create icon in system tray notifyIcon = new NotifyIcon(); ... } The intermediate "ExecuteCommand.exe": static void Main(string[] args) { startCommandServerIfRequired(); var channel = new TcpClientChannel(); ChannelServices.RegisterChannel(channel, false); var service = (IMyService)Activator.GetObject(typeof(IMyService), "tcp://localhost:8234/CommandServer"); service.RunCommand(args); } Problem As the server is very long to start (about 20s to initialize the required resources), the "ExecuteCommand.exe" fails on service.RunCommand(args) line because the server is yet not available. Question Is there a elegant way I can tune the delay before to receive "service not available" when calling service.RunCommand ? NB1: Currently I'm working around the issue by adding a mutex in server to indicate for complete initiliazation and have "ExecuteCommand.exe" to wait for this mutex before to call service.RunCommand. NB2: I have no background with .net remoting, nor WCF which is recommended replacer. (I chose .net remoting because this looked easier to set-up for this single shot issue in running external commands).

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