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  • I can't use my iPod touch (32GB)

    - by Silambarasan
    Hi All.. I have connected my ipod touch 32gb in my ubuntu 10.10 os.It's connected on os and shows in desktop. but it's not showing as a device in Rhythmbox music player. and also I can't open directly like folder or drive or usb device. when I try to open it show this Error: Could not display "gphoto2://[usb:001,003]/". Error: DBus error org.freedesktop.DBus.Error.ServiceUnknown: The name :1.207 was not provided by any .service files Please select another viewer and try again. Any solution for this problem?

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  • La Chine concurrence Apple avec l'iPed, une tablette 5 fois moins chère que l'iPad tournant sous And

    La Chine concurrence Apple avec l'iPed, une tablette 5 fois moins chère que l'iPad tournant sous Android Au salon Computex, qui a actuellement lieu à Taïwan, divers constructeurs présentent leurs nouveaux produits. Parmi les nouveaux appareils, plusieurs Tablet PC. Et, parmi ces tablettes... l'iPed. Ce gadget chinois est commercialisé par plusieurs revendeurs chinois. Non content d'emprunter le nom de la tablette d'Apple à une lettre près, il en reprend aussi le design et les icônes (et même l'emballage). Se voulant bon marché et abordable, l'iPed ne coûte que 105 dollars (86 euros, soit cinq fois moins cher que l'original). Pour ce prix, l'appareil est équipé d'un processeur Intel et de l'OS de Google : Android. Mai...

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  • NetworkManager refuses to manage my WLAN interface

    - by user104167
    I'm using Ubuntu 12.10 with Gnome 3.6 on a brand-new Samsung NP900X4C. The installer detected the wireless adapter, took in the SSID and WPA passphrase, wrote these into /etc/network/interfaces and connected perfectly. Once installation was finished I wanted to switch to using NetworkManager to manage the wireless adapter, since this is much more convenient than fiddling with /etc/network/interfaces every time I find a new hotspot. Therefore I edited /etc/NetworkManager/NetworkManager.conf to set: [ifupdown] managed=true When I rebooted NetworkManager, the problems started: - The NetworkManager tray applet changed from saying device not managed to device not ready - I lost all internet connectivity as wlan0 would not associate to the Access Point - if I set managed=false in NetworkManager.conf and restarted both NetworkManager and networking services from the command-line, the Gnome desktop "semi-crashed" and lost all its Window Decorations, the panel, the launcher and basically became unusable. However if I restart the computer completely after setting managed=false, wlan0 once again works perfectly.

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  • Grub cannot boot Windows 7 loader entry on 3tb drive

    - by twicejr
    It fails and it says 'cannot find device'. It will work again if I reinstall Windows, and use something like EasyBCD. But I'd like grub as a loader only, can someone help me out here? My system has a regular BIOS (p35-ds4 mainboard) so no UEFI support. Previously ran Windows 8 alongside ubuntu 13.04, now wanted windows 7 again with ubuntu 13.10. I am using disk /dev/sda. 3000.6 GB, 3000591900160 bytes 255 head, 63 sectors/track, 364801 cylinders, 5860531055 sectors Sector size (logical/fysical): 512 bytes / 4096 bytes Device Begin End Blocks ID System /dev/sda1 2048 419432447 209715200 83 Linux /dev/sda2 419432448 436013055 8290304 82 Linux swap /dev/sda3 436015102 1576339455 570162177 5 extended Partition 3 does not start on a fysical sector limit. /dev/sda4 * 1576339456 5860530175 2142095360 7 HPFS/NTFS/exFAT /dev/sda5 436015104 855443455 209714176 7 HPFS/NTFS/exFAT /dev/sda6 855445504 1576339455 360446976 7 HPFS/NTFS/exFAT

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  • DropVox Records Voice Memos Right to Your Dropbox Account

    - by Jason Fitzpatrick
    DropVox is a clever and highly specialized application that, quite effectively, turns your iOS device into a voice recorder with Dropbox-based storage. Install the app, launch it, hit the record button, and your recording is uploaded to your Dropbox account in .m4a format as soon as you’re finished creating it. You can also configure DropVox to start recording immediately after launch and to continue recording if the device is locked or other applications are in use. Hit up the link to grab a copy. DropVox is currently $0.99 (50% off for a limited time) and works on the iPhone, iPad, and iPod Touch with microphone attached. DropVox [via Download Squad] HTG Explains: What’s the Difference Between the Windows 7 HomeGroups and XP-style Networking?Internet Explorer 9 Released: Here’s What You Need To KnowHTG Explains: How Does Email Work?

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  • Adobe jette l'éponge sur l'iPhone, «Puisqu'on ne veut pas de nous, on va voir ailleurs» déclare le r

    Mise à jour du 21.04.2009 par Katleen Adobe jette l'éponge sur l'iPhone, «Puisqu'on ne veut pas de nous, on va voir ailleurs» déclare le responsable de Flash Suite à la situation qui s'envenime entre Adobe et Apple, Mike Chambers, le responsable du produit Flash pour la firme a décidé de s'exprimre publiquement dans un long billet, publié sur son blog. Pour contrer la compagnie de Jobs, il expose ses projets avec sa rivale de Mountain View. «Heureusement, Apple n'est pas le seul acteur. Les téléphones sous Android connaissent un succès croissant et de nombreuses tablettes Android doivent sortir cette année. Nous travaillons main dans la main avec Google pour amener Flash Player et Adobe Air s...

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  • Unable to stop TOSHIBA TransMemory

    - by user66498
    I have a USB,when I choose safety remove, occur this error message.How to solve the problem? Unable to stop TOSHIBA TransMemory Error detaching: helper exited with exit code 1: Detaching device /dev/sdb USB device: /sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2) SYNCHRONIZE CACHE: synchronize cache(10): Fixed format, current; Sense key: Key=9 Additional sense: Logical unit not ready, cause not reportable Info fld=0x0 [0] FAILED: No such file or directory (Continuing despite SYNCHRONIZE CACHE failure.) STOP UNIT: start stop unit: transport: Host_status=0x07 [DID_ERROR] Driver_status=0x00 [DRIVER_OK, SUGGEST_OK] FAILED: No such file or directory

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  • Really, Mobile Devices will Take Over the World?

    - by p.gielens
    My blog has been quiet for quite a while. My inspiration comes from crunching/exchanging information which I should do more often. Gartner analysis tells us that by 2013 mobile phones will overtake PC’s as the most common Web access device worldwide. A few years back I would have said non sense, but apparently most Web users are comfortable with less processing power. Just take a look at the increasing business in Netbooks. Wouldn’t it be great to have a mobile phone which can connect wirelessly to my home TV, monitor, car display, mouse, keyboard, etc? And to have the processing power of the current Netbook generation? Where can I buy it? Why are we making our PC devices (for instance the slate) smaller while we can make our mobile device’s functionality bigger? What about the single responsibility principle? Does it apply to physical devices as well as good object-oriented software?

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  • Is the Apple iPad for you now or should you wait until the iPhone 4 is released?

    The iPad came to the market last Saturday and as always with the Apple marketing came the big lines and small tents that never seen a camp site but the Apple stores. There are the people that want one right away and want to be the first person to own the new shiny device from Apple and there are the people that are willing to wait a month for the device with 3G instead of just WiFi only. The iPad is an interesting concept, a bigger iTouch that can be used as a replacement for your Netbook, Kindle,...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Google s'intéresse de près au bureau en 3D en rachetant une start-up canadienne : bientôt dans Chrom

    Google s'intéresse de près au bureau en 3D En rachetant une start-up canadienne : bientôt dans Chrome et Android ? BumpTop vient d'être rachetée par Google. Cette start-up canadienne a mis au point une interface 3D destinée à remplacer le bureau de Windows ou de Mac OS. Visiblement très intéressé par ce produit - et très satisfait de son état d'avancement - Google a décidé de faire l'acquisition de la société pour un montant resté confidentiel. Un des atouts de BumpTop est de supporter le multi-touch. Une fonctionnalité qui en fait un client idéal pour intégrer Android, l'OS de Google pour les smartphones (ou les terminaux tels que les télévisions), voire pou...

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  • Ubuntu 13.10 is terrible

    - by user137017
    I was satisfied with 13.04. But when I upgraded to 13.10, I've had a lot of issues and some things just no longer work. To name a few problems: Can't change the brightness My laptop makes more noise than before It freezes more frequently (the kind that doesn't respond to ctr + alt + f2) Sometimes it boots up and and can't play any media files When running a full screened virtual machine in Workstation, ubuntu catches mouse at the edges When I have a VM opened in Workstation and I try to open up another, the first one gets powered off Most irritatingly, when I have a virtual machine running in full screen, every now and then the vm screen goes black and I have to switch to the host and come back 13.10 has offered nothing to compensate for these problems. I would like to get some advice about what I can do. Should I stick with 13.10 and hope the bugs will be fixed? Would a clean reinstall of 13.10 help? Btw, I'm giving some thought to trying other distros.

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  • How to decrypt an encrypted Apple iTunes iPhone backup?

    - by afit
    I've been asked by a number of unfortunate iPhone users to help them restore data from their iTunes backups. This is easy when they are unencrypted, but not when they are encrypted, whether or not the password is known. As such, I'm trying to figure out the encryption scheme used on mddata and mdinfo files when encrypted. I have no problems reading these files otherwise, and have built some robust C# libraries for doing so. (If you're able to help, I don't care which language you use. It's the principle I'm after here!) The Apple "iPhone OS Enterprise Deployment Guide" states that "Device backups can be stored in encrypted format by selecting the Encrypt iPhone Backup option in the device summary pane of iTunes. Files are encrypted using AES128 with a 256-bit key. The key is stored securely in the iPhone keychain." That's a pretty good clue, and there's some good info here on Stackoverflow on iPhone AES/Rijndael interoperability suggesting a keysize of 128 and CBC mode may be used. Aside from any other obfuscation, a key and initialisation vector (IV)/salt are required. One might assume that the key is a manipulation of the "backup password" that users are prompted to enter by iTunes and passed to "AppleMobileBackup.exe", padded in a fashion dictated by CBC. However, given the reference to the iPhone keychain, I wonder whether the "backup password" might not be used as a password on an X509 certificate or symmetric private key, and that the certificate or private key itself might be used as the key. (AES and the iTunes encrypt/decrypt process is symmetric.) The IV is another matter, and it could be a few things. Perhaps it's one of the keys hard-coded into iTunes, or into the devices themselves. Although Apple's comment above suggests the key is present on the device's keychain, I think this isn't that important. One can restore an encrypted backup to a different device, which suggests all information relevant to the decryption is present in the backup and iTunes configuration, and that anything solely on the device is irrelevant and replacable in this context. So where might be the key be? I've listed paths below from a Windows machine but it's much of a muchness whichever OS we use. The "\appdata\Roaming\Apple Computer\iTunes\itunesprefs.xml" contains a PList with a "Keychain" dict entry in it. The "\programdata\apple\Lockdown\09037027da8f4bdefdea97d706703ca034c88bab.plist" contains a PList with "DeviceCertificate", "HostCertificate", and "RootCertificate", all of which appear to be valid X509 certs. The same file also appears to contain asymmetric keys "RootPrivateKey" and "HostPrivateKey" (my reading suggests these might be PKCS #7-enveloped). Also, within each backup there are "AuthSignature" and "AuthData" values in the Manifest.plist file, although these appear to be rotated as each file gets incrementally backed up, suggested they're not that useful as a key, unless something really quite involved is being done. There's a lot of misleading stuff out there suggesting getting data from encrypted backups is easy. It's not, and to my knowledge it hasn't been done. Bypassing or disabling the backup encryption is another matter entirely, and is not what I'm looking to do. This isn't about hacking apart the iPhone or anything like that. All I'm after here is a means to extract data (photos, contacts, etc.) from encrypted iTunes backups as I can unencrypted ones. I've tried all sorts of permutations with the information I've put down above but got nowhere. I'd appreciate any thoughts or techniques I might have missed.

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  • problem with send me log

    - by Lynnooi
    Hi, I had try to implement the send me log feature into my apps but I can't get it right. Can anyone please help me with it? In the logcat, it shows the errors: 03-29 21:23:37.636: ERROR/AndroidRuntime(820): Uncaught handler: thread AsyncTask #1 exiting due to uncaught exception 03-29 21:23:37.726: ERROR/AndroidRuntime(820): java.lang.RuntimeException: An error occured while executing doInBackground() 03-29 21:23:37.726: ERROR/AndroidRuntime(820): at android.os.AsyncTask$3.done(AsyncTask.java:200) 03-29 21:23:37.726: ERROR/AndroidRuntime(820): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:234) 03-29 21:23:37.726: ERROR/AndroidRuntime(820): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:258) 03-29 21:23:37.726: ERROR/AndroidRuntime(820): at java.util.concurrent.FutureTask.run(FutureTask.java:122) 03-29 21:23:37.726: ERROR/AndroidRuntime(820): at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:648) 03-29 21:23:37.726: ERROR/AndroidRuntime(820): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:673) 03-29 21:23:37.726: ERROR/AndroidRuntime(820): at java.lang.Thread.run(Thread.java:1058) 03-29 21:23:37.726: ERROR/AndroidRuntime(820): Caused by: java.lang.NullPointerException 03-29 21:23:37.726: ERROR/AndroidRuntime(820): at resonet.android.androidgallery.helloAndroid$CheckForceCloseTask.doInBackground(helloAndroid.java:1565) 03-29 21:23:37.726: ERROR/AndroidRuntime(820): at resonet.android.androidgallery.helloAndroid$CheckForceCloseTask.doInBackground(helloAndroid.java:1) 03-29 21:23:37.726: ERROR/AndroidRuntime(820): at android.os.AsyncTask$2.call(AsyncTask.java:185) 03-29 21:23:37.726: ERROR/AndroidRuntime(820): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:256) 03-29 21:23:37.726: ERROR/AndroidRuntime(820): ... 4 more Thanks. Here is my code: public class helloAndroid extends Activity implements OnClickListener { public static final int DIALOG_SEND_LOG = 345350; protected static final int DIALOG_PROGRESS_COLLECTING_LOG = 3255; protected static final int DIALOG_FAILED_TO_COLLECT_LOGS = 3535122; private static final int DIALOG_REPORT_FORCE_CLOSE = 3535788; private LogCollector mLogCollector; public void onCreate(Bundle savedInstanceState) { requestWindowFeature(Window.FEATURE_NO_TITLE); Bundle b = this.getIntent().getExtras(); s = b.getString("specialValue").trim(); String xmlURL = ""; CheckForceCloseTask task = new CheckForceCloseTask(); task.execute(); } private void throwException() { throw new NullPointerException(); } @Override protected Dialog onCreateDialog(int id) { Dialog dialog = null; switch (id) { case DIALOG_SEND_LOG: case DIALOG_REPORT_FORCE_CLOSE: Builder builder = new AlertDialog.Builder(this); String message; if (id==DIALOG_SEND_LOG) message = "Do you want to send me your logs?"; else message = "It appears this app has been force-closed, do you want to report it to me?"; builder.setTitle("Warning") .setIcon(android.R.drawable.ic_dialog_alert) .setMessage(message) .setPositiveButton("Yes", this) .setNegativeButton("No", this); dialog = builder.create(); break; case DIALOG_PROGRESS_COLLECTING_LOG: ProgressDialog pd = new ProgressDialog(this); pd.setTitle("Progress"); pd.setMessage("Collecting logs..."); pd.setIndeterminate(true); dialog = pd; break; case DIALOG_FAILED_TO_COLLECT_LOGS: builder = new AlertDialog.Builder(this); builder.setTitle("Error") .setMessage("Failed to collect logs.") .setNegativeButton("OK", null); dialog = builder.create(); } return dialog; } class CheckForceCloseTask extends AsyncTask { @Override protected Boolean doInBackground(Void... params) { return mLogCollector.hasForceCloseHappened(); } @Override protected void onPostExecute(Boolean result) { if (result) { showDialog(DIALOG_REPORT_FORCE_CLOSE); } else Toast.makeText(getApplicationContext(), "No force close detected.", Toast.LENGTH_LONG).show(); } } public void onClick(DialogInterface dialog, int which) { switch (which) { case DialogInterface.BUTTON_POSITIVE: new AsyncTask() { @Override protected Boolean doInBackground(Void... params) { return mLogCollector.collect(); } @Override protected void onPreExecute() { showDialog(DIALOG_PROGRESS_COLLECTING_LOG); } @Override protected void onPostExecute(Boolean result) { dismissDialog(DIALOG_PROGRESS_COLLECTING_LOG); if (result) mLogCollector.sendLog("[email protected]", "Error Log", "Preface\nPreface line 2"); else showDialog(DIALOG_FAILED_TO_COLLECT_LOGS); } }.execute(); } dialog.dismiss(); } }

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  • NHibernate Proxy Creation

    - by Chris Meek
    I have a class structure like the following class Container { public virtual int Id { get; set; } public IList<Base> Bases { get; set; } } class Base { public virtual int Id { get; set; } public virtual string Name { get; set; } } class EnemyBase : Base { public virtual int EstimatedSize { get; set; } } class FriendlyBase : Base { public virtual int ActualSize { get; set; } } Now when I ask the session for a particular Container it normally gives me the concrete EnemyBase and FriendlyBase objects in the Bases collection. I can then (if I so choose) cast them to their concrete types and do something specific with them. However, sometime I get a proxy of the "Base" class which is not castable to the concrete types. The same method is used both times with the only exception being that in the case that I get proxies I have added some related entities to the session (think the friendly base having a collection of people or something like that). Is there any way I can prevent it from doing the proxy creating and why would it choose to do this in some scenarios? UPDATE The mappings are generated with the automap feature of fluentnhibernate but look something like this when exported <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" default-access="property" auto-import="true" default-cascade="none" default-lazy="true"> <class xmlns="urn:nhibernate-mapping-2.2" mutable="true" name="Base" table="`Base`"> <id name="Id" type="System.Int32, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <column name="Id" /> <generator class="MyIdGenerator" /> </id> <property name="Name" type="String"> <column name="Name" /> </property> <joined-subclass name="EnemyBase"> <key> <column name="Id" /> </key> <property name="EstimatedSize" type="Int"> <column name="EstimatedSize" /> </property> </joined-subclass> <joined-subclass name="FriendlyBase"> <key> <column name="Id" /> </key> <property name="ActualSize" type="Int"> <column name="ActualSize" /> </property> </joined-subclass> </class> </hibernate-mapping> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" default-access="property" auto-import="true" default-cascade="none" default-lazy="true"> <class xmlns="urn:nhibernate-mapping-2.2" mutable="true" name="Container" table="`Container`"> <id name="Id" type="System.Int32, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <column name="Id" /> <generator class="MyIdGenerator" /> </id> <bag cascade="all-delete-orphan" inverse="true" lazy="false" name="Bases" mutable="true"> <key> <column name="ContainerId" /> </key> <one-to-many class="Base" /> </bag> </class> </hibernate-mapping>

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  • Prevent lazy loading in nHibernate

    - by Ciaran
    Hi, I'm storing some blobs in my database, so I have a Document table and a DocumentContent table. Document contains a filename, description etc and has a DocumentContent property. I have a Silverlight client, so I don't want to load up and send the DocumentContent to the client unless I explicity ask for it, but I'm having trouble doing this. I've read the blog post by Davy Brion. I have tried placing lazy=false in my config and removing the virtual access modifier but have had no luck with it as yet. Every time I do a Session.Get(id), the DocumentContent is retrieved via an outer join. I only want this property to be populated when I explicity join onto this table and ask for it. Any help is appreciated. My NHibernate mapping is as follows: <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="Jrm.Model" namespace="Jrm.Model"> <class name="JrmDocument" lazy="false"> <id name="JrmDocumentID"> <generator class="native" /> </id> <property name="FileName"/> <property name="Description"/> <many-to-one name="DocumentContent" class="JrmDocumentContent" unique="true" column="JrmDocumentContentID" lazy="false"/> </class> <class name="JrmDocumentContent" lazy="false"> <id name="JrmDocumentContentID"> <generator class="native" /> </id> <property name="Content" type="BinaryBlob" lazy="false"> <column name="FileBytes" sql-type="varbinary(max)"/> </property> </class> </hibernate-mapping> and my classes are: [DataContract] public class JrmDocument : ModelBase { private int jrmDocumentID; private JrmDocumentContent documentContent; private long maxFileSize; private string fileName; private string description; public JrmDocument() { } public JrmDocument(string fileName, long maxFileSize) { DocumentContent = new JrmDocumentContent(File.ReadAllBytes(fileName)); FileName = new FileInfo(fileName).Name; } [DataMember] public virtual int JrmDocumentID { get { return jrmDocumentID; } set { jrmDocumentID = value; OnPropertyChanged("JrmDocumentID"); } } [DataMember] public JrmDocumentContent DocumentContent { get { return documentContent; } set { documentContent = value; OnPropertyChanged("DocumentContent"); } } [DataMember] public virtual long MaxFileSize { get { return maxFileSize; } set { maxFileSize = value; OnPropertyChanged("MaxFileSize"); } } [DataMember] public virtual string FileName { get { return fileName; } set { fileName = value; OnPropertyChanged("FileName"); } } [DataMember] public virtual string Description { get { return description; } set { description = value; OnPropertyChanged("Description"); } } } [DataContract] public class JrmDocumentContent : ModelBase { private int jrmDocumentContentID; private byte[] content; public JrmDocumentContent() { } public JrmDocumentContent(byte[] bytes) { Content = bytes; } [DataMember] public int JrmDocumentContentID { get { return jrmDocumentContentID; } set { jrmDocumentContentID = value; OnPropertyChanged("JrmDocumentContentID"); } } [DataMember] public byte[] Content { get { return content; } set { content = value; OnPropertyChanged("Content"); } } }

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  • How do I get a delete trigger working using fluent API in CTP5?

    - by user668472
    I am having trouble getting referential integrity dialled down enough to allow my delete trigger to fire. I have a dependent entity with three FKs. I want it to be deleted when any of the principal entities is deleted. For principal entities Role and OrgUnit (see below) I can rely on conventions to create the required one-many relationship and cascade delete does what I want, ie: Association is removed when either principal is deleted. For Member, however, I have multiple cascade delete paths (not shown here) which SQL Server doesn't like, so I need to use fluent API to disable cascade deletes. Here is my (simplified) model: public class Association { public int id { get; set; } public int roleid { get; set; } public virtual Role role { get; set; } public int? memberid { get; set; } public virtual Member member { get; set; } public int orgunitid { get; set; } public int OrgUnit orgunit { get; set; } } public class Role { public int id { get; set; } public virtual ICollection<Association> associations { get; set; } } public class Member { public int id { get; set; } public virtual ICollection<Association> associations { get; set; } } public class Organization { public int id { get; set; } public virtual ICollection<Association> associations { get; set; } } My first run at fluent API code looks like this: protected override void OnModelCreating(System.Data.Entity.ModelConfiguration.ModelBuilder modelBuilder) { DbDatabase.SetInitializer<ConfDB_Model>(new ConfDBInitializer()); modelBuilder.Entity<Member>() .HasMany(m=>m.assocations) .WithOptional(a=>a.member) .HasForeignKey(a=>a.memberId) .WillCascadeOnDelete(false); } My seed function creates the delete trigger: protected override void Seed(ConfDB_Model context) { context.Database.SqlCommand("CREATE TRIGGER MemberAssocTrigger ON dbo.Members FOR DELETE AS DELETE Assocations FROM Associations, deleted WHERE Associations.memberId = deleted.id"); } PROBLEM: When I run this, create a Role, a Member, an OrgUnit, and an Association tying the three together all is fine. When I delete the Role, the Association gets cascade deleted as I expect. HOWEVER when I delete the Member I get an exception with a referential integrity error. I have tried setting ON CASCADE SET NULL because my memberid FK is nullable but SQL complains again about multiple cascade paths, so apparently I can cascade nothing in the Member-Association relationship. To get this to work I must add the following code to Seed(): context.Database.SqlCommand("ALTER TABLE dbo.ACLEntries DROP CONSTRAINT member_aclentries"); As you can see, this drops the constraint created by the model builder. QUESTION: this feels like a complete hack. Is there a way using fluent API for me to say that referential integrity should NOT be checked, or otherwise to get it to relax enough for the Member delete to work and allow the trigger to be fired? Thanks in advance for any help you can offer. Although fluent APIs may be "fluent" I find them far from intuitive.

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  • How to design a high-level application protocol for metadata syncing between devices and server?

    - by Jaanus
    I am looking for guidance on how to best think about designing a high-level application protocol to sync metadata between end-user devices and a server. My goal: the user can interact with the application data on any device, or on the web. The purpose of this protocol is to communicate changes made on one endpoint to other endpoints through the server, and ensure all devices maintain a consistent picture of the application data. If user makes changes on one device or on the web, the protocol will push data to the central repository, from where other devices can pull it. Some other design thoughts: I call it "metadata syncing" because the payloads will be quite small, in the form of object IDs and small metadata about those ID-s. When client endpoints retrieve new metadata over this protocol, they will fetch actual object data from an external source based on this metadata. Fetching the "real" object data is out of scope, I'm only talking about metadata syncing here. Using HTTP for transport and JSON for payload container. The question is basically about how to best design the JSON payload schema. I want this to be easy to implement and maintain on the web and across desktop and mobile devices. The best approach feels to be simple timer- or event-based HTTP request/response without any persistent channels. Also, you should not have a PhD to read it, and I want my spec to fit on 2 pages, not 200. Authentication and security are out of scope for this question: assume that the requests are secure and authenticated. The goal is eventual consistency of data on devices, it is not entirely realtime. For example, user can make changes on one device while being offline. When going online again, user would perform "sync" operation to push local changes and retrieve remote changes. Having said that, the protocol should support both of these modes of operation: Starting from scratch on a device, should be able to pull the whole metadata picture "sync as you go". When looking at the data on two devices side by side and making changes, should be easy to push those changes as short individual messages which the other device can receive near-realtime (subject to when it decides to contact server for sync). As a concrete example, you can think of Dropbox (it is not what I'm working on, but it helps to understand the model): on a range of devices, the user can manage a files and folders—move them around, create new ones, remove old ones etc. And in my context the "metadata" would be the file and folder structure, but not the actual file contents. And metadata fields would be something like file/folder name and time of modification (all devices should see the same time of modification). Another example is IMAP. I have not read the protocol, but my goals (minus actual message bodies) are the same. Feels like there are two grand approaches how this is done: transactional messages. Each change in the system is expressed as delta and endpoints communicate with those deltas. Example: DVCS changesets. REST: communicating the object graph as a whole or in part, without worrying so much about the individual atomic changes. What I would like in the answers: Is there anything important I left out above? Constraints, goals? What is some good background reading on this? (I realize this is what many computer science courses talk about at great length and detail... I am hoping to short-circuit it by looking at some crash course or nuggets.) What are some good examples of such protocols that I could model after, or even use out of box? (I mention Dropbox and IMAP above... I should probably read the IMAP RFC.)

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  • Lockless queue implementation ends up having a loop under stress

    - by Fozi
    I have lockless queues written in C in form of a linked list that contains requests from several threads posted to and handled in a single thread. After a few hours of stress I end up having the last request's next pointer pointing to itself, which creates an endless loop and locks up the handling thread. The application runs (and fails) on both Linux and Windows. I'm debugging on Windows, where my COMPARE_EXCHANGE_PTR maps to InterlockedCompareExchangePointer. This is the code that pushes a request to the head of the list, and is called from several threads: void push_request(struct request * volatile * root, struct request * request) { assert(request); do { request->next = *root; } while(COMPARE_EXCHANGE_PTR(root, request, request->next) != request->next); } This is the code that gets a request from the end of the list, and is only called by a single thread that is handling them: struct request * pop_request(struct request * volatile * root) { struct request * volatile * p; struct request * request; do { p = root; while(*p && (*p)->next) p = &(*p)->next; // <- loops here request = *p; } while(COMPARE_EXCHANGE_PTR(p, NULL, request) != request); assert(request->next == NULL); return request; } Note that I'm not using a tail pointer because I wanted to avoid the complication of having to deal with the tail pointer in push_request. However I suspect that the problem might be in the way I find the end of the list. There are several places that push a request into the queue, but they all look generaly like this: // device->requests is defined as struct request * volatile requests; struct request * request = malloc(sizeof(struct request)); if(request) { // fill out request fields push_request(&device->requests, request); sem_post(device->request_sem); } The code that handles the request is doing more than that, but in essence does this in a loop: if(sem_wait_timeout(device->request_sem, timeout) == sem_success) { struct request * request = pop_request(&device->requests); // handle request free(request); } I also just added a function that is checking the list for duplicates before and after each operation, but I'm afraid that this check will change the timing so that I will never encounter the point where it fails. (I'm waiting for it to break as I'm writing this.) When I break the hanging program the handler thread loops in pop_request at the marked position. I have a valid list of one or more requests and the last one's next pointer points to itself. The request queues are usually short, I've never seen more then 10, and only 1 and 3 the two times I could take a look at this failure in the debugger. I thought this through as much as I could and I came to the conclusion that I should never be able to end up with a loop in my list unless I push the same request twice. I'm quite sure that this never happens. I'm also fairly sure (although not completely) that it's not the ABA problem. I know that I might pop more than one request at the same time, but I believe this is irrelevant here, and I've never seen it happening. (I'll fix this as well) I thought long and hard about how I can break my function, but I don't see a way to end up with a loop. So the question is: Can someone see a way how this can break? Can someone prove that this can not? Eventually I will solve this (maybe by using a tail pointer or some other solution - locking would be a problem because the threads that post should not be locked, I do have a RW lock at hand though) but I would like to make sure that changing the list actually solves my problem (as opposed to makes it just less likely because of different timing).

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