Search Results

Search found 956 results on 39 pages for 'synchronization'.

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

Page 3/39 | < Previous Page | 1 2 3 4 5 6 7 8 9 10 11 12  | Next Page >

  • Any techniques to interrupt, kill, or otherwise unwind (releasing synchronization locks) a single de

    - by gojomo
    I have a long-running process where, due to a bug, a trivial/expendable thread is deadlocked with a thread which I would like to continue, so that it can perform some final reporting that would be hard to reproduce in another way. Of course, fixing the bug for future runs is the proper ultimate resolution. Of course, any such forced interrupt/kill/stop of any thread is inherently unsafe and likely to cause other unpredictable inconsistencies. (I'm familiar with all the standard warnings and the reasons for them.) But still, since the only alternative is to kill the JVM process and go through a more lengthy procedure which would result in a less-complete final report, messy/deprecated/dangerous/risky/one-time techniques are exactly what I'd like to try. The JVM is Sun's 1.6.0_16 64-bit on Ubuntu, and the expendable thread is waiting-to-lock an object monitor. Can an OS signal directed to an exact thread create an InterruptedException in the expendable thread? Could attaching with gdb, and directly tampering with JVM data or calling JVM procedures allow a forced-release of the object monitor held by the expendable thread? Would a Thread.interrupt() from another thread generate a InterruptedException from the waiting-to-lock frame? (With some effort, I can inject an arbitrary beanshell script into the running system.) Can the deprecated Thread.stop() be sent via JMX or any other remote-injection method? Any ideas appreciated, the more 'dangerous', the better! And, if your suggestion has worked in personal experience in a similar situation, the best!

    Read the article

  • absolute audio synchronization

    - by user1780526
    I would like to synchronize my computer with an external camcorder recording so that I can know exactly (to the millisecond) when certain recored events happen with respect to other sensors logged by the computer. One idea is to playback short sound pulses or chirps every second from the computer that get picked up by the microphone on the camcorder. But the accuracy of a simple cron job playing a sound clip is not precise enough. I was thinking of using something like gstreamer, but how does one get it to playback a clip at precisely a certain time according to the system clock?

    Read the article

  • What would be my best MySQL Synchronization method?

    - by Kerry
    We're moving a social media service to be on separate data centers with global load balancing, as our other hosting provider's entire data center went down. Twice. This means that both websites need to be synchronized in some sense -- I'm less worried about the code of the pages, that's easy enough to sync, but they need to have the same database data. From my research on SO, it seems MySQL Replication is a good option, but the MySQL manual, for scaling out, says that its best when there are far more reads then there are writes/updates: http://dev.mysql.com/doc/refman/5.0/en/replication-solutions-scaleout.html In our case, it's about equal. We're getting around 200-300 thousand requests a day right now, and we can grow rapidly. Every request is both a read and write request. What would be the best method or tool to handle this?

    Read the article

  • Win32 reset event like synchronization class with boost C++

    - by fgungor
    I need some mechanism reminiscent of Win32 reset events that I can check via functions having the same semantics with WaitForSingleObject() and WaitForMultipleObjects() (Only need the ..SingleObject() version for the moment) . But I am targeting multiple platforms so all I have is boost::threads (AFAIK) . I came up with the following class and wanted to ask about the potential problems and whether it is up to the task or not. Thanks in advance. class reset_event { bool flag, auto_reset; boost::condition_variable cond_var; boost::mutex mx_flag; public: reset_event(bool _auto_reset = false) : flag(false), auto_reset(_auto_reset) { } void wait() { boost::unique_lock<boost::mutex> LOCK(mx_flag); if (flag) return; cond_var.wait(LOCK); if (auto_reset) flag = false; } bool wait(const boost::posix_time::time_duration& dur) { boost::unique_lock<boost::mutex> LOCK(mx_flag); bool ret = cond_var.timed_wait(LOCK, dur) || flag; if (auto_reset && ret) flag = false; return ret; } void set() { boost::lock_guard<boost::mutex> LOCK(mx_flag); flag = true; cond_var.notify_all(); } void reset() { boost::lock_guard<boost::mutex> LOCK(mx_flag); flag = false; } }; Example usage; reset_event terminate_thread; void fn_thread() { while(!terminate_thread.wait(boost::posix_time::milliseconds(10))) { std::cout << "working..." << std::endl; boost::this_thread::sleep(boost::posix_time::milliseconds(1000)); } std::cout << "thread terminated" << std::endl; } int main() { boost::thread worker(fn_thread); boost::this_thread::sleep(boost::posix_time::seconds(1)); terminate_thread.set(); worker.join(); return 0; } EDIT I have fixed the code according to Michael Burr's suggestions. My "very simple" tests indicate no problems. class reset_event { bool flag, auto_reset; boost::condition_variable cond_var; boost::mutex mx_flag; public: explicit reset_event(bool _auto_reset = false) : flag(false), auto_reset(_auto_reset) { } void wait() { boost::unique_lock<boost::mutex> LOCK(mx_flag); if (flag) { if (auto_reset) flag = false; return; } do { cond_var.wait(LOCK); } while(!flag); if (auto_reset) flag = false; } bool wait(const boost::posix_time::time_duration& dur) { boost::unique_lock<boost::mutex> LOCK(mx_flag); if (flag) { if (auto_reset) flag = false; return true; } bool ret = cond_var.timed_wait(LOCK, dur); if (ret && flag) { if (auto_reset) flag = false; return true; } return false; } void set() { boost::lock_guard<boost::mutex> LOCK(mx_flag); flag = true; cond_var.notify_all(); } void reset() { boost::lock_guard<boost::mutex> LOCK(mx_flag); flag = false; } };

    Read the article

  • Speed of Synchronization vs Normal

    - by Swaranga Sarma
    I have a class which is written for a single thread with no methods being synchronized. class MyClass implements MyInterface{ //interface implementation methods, not synchronized } But we also needed a synchronized version of the class. So we made a wrapper class that implements the same interface but has a constructor that takes an instance of MyClass. Any call to the methods of the synchronized class are delegated to the instance of MyClass. Here is my synchronized class.. class SynchronizedMyClass implements MyInterface{ //the constructor public SynchronizedMyClass(MyInterface i/*this is actually an instance of MyClass*/) //interface implementation methods; all synchronized; all delegated to the MyInterface instance } After all this I ran numerous amounts of test runs with both the classes. The tests involve reading log files and counting URLs in each line. The problem is that the synchronized version of the class is consistently taking less time for the parsing. I am using only one thread for the teste, so there is no chance of deadlocks, race around condition etc etc. Each log file contains more than 5 million lines which means calling the methods more than 5 million times. Can anyone explain why synchronized versiuon of the class migt be taking less time than the normal one?

    Read the article

  • Directory Synchronization

    - by Robert May
    We’re using federated security with Office 365 and everything was running swimmingly and then I started getting the following error when trying to synchronize security information: “An unknown error occurred with the Microsoft Online Services Sign-in Assistant. Contact Technical Support.” Great.  Very descriptive.  In the event viewer, you get a bit more detail: GetAuthState() failed with -2147186688 state. HResult:0. Contact Technical Support.  (0x80048831) If you do some searching, you’ll find that there are a couple of MSDN articles about this error.  In KB2502710 you’re told to reinstall sign in assistant.  This one requires a reboot.  In KB2517393 you’re told to make sure that your proxy settings are working correctly.  I’m not using a proxy and everything was set up right. Rather frustrating and I couldn’t figure out what was going on.  What finally keyed me in was the error number being presented.  Rather than 80048800, which is listed in the second article, I was getting 80048831.  I did a quick search and found something that was seemingly unrelated here.  Could it really be so simple as the password having expired for my synchronization user? Turns out, it was that simple.  Once the password was reset and reentered, everything worked great again. Since this isn’t a user that humans use, I also don’t want the password to expire.  You can find the instructions for that (use Set-MsolUser –UserPrincipalName <user ID> –PasswordNeverExpires $true) here. Technorati Tags: Office 365

    Read the article

  • Unable to sync time using `ntpdate`, error: "no server suitable for synchronization found"

    - by William Ting
    My ntp.conf file: user@pc[0][07:37:40]:/etc$ cat /etc/ntp.conf idriftfile /var/lib/ntp/ntp.drift server 0.pool.ntp.org server 1.pool.ntp.org server 2.pool.ntp.org server pool.ntp.org Command output: user@pc[0][07:37:24]:/etc$ sudo ntpdate -dv pool.ntp.org 18 Jun 07:37:35 ntpdate[10737]: ntpdate [email protected] Tue Apr 19 07:15:05 UTC 2011 (1) Looking for host pool.ntp.org and service ntp host found : conquest.kjsl.com transmit(198.137.202.16) transmit(216.45.57.38) transmit(64.6.144.6) transmit(198.137.202.16) transmit(216.45.57.38) transmit(64.6.144.6) transmit(198.137.202.16) transmit(216.45.57.38) transmit(64.6.144.6) transmit(198.137.202.16) transmit(216.45.57.38) transmit(64.6.144.6) transmit(198.137.202.16) transmit(216.45.57.38) transmit(64.6.144.6) 198.137.202.16: Server dropped: no data 216.45.57.38: Server dropped: no data 64.6.144.6: Server dropped: no data server 198.137.202.16, port 123 stratum 0, precision 0, leap 00, trust 000 refid [198.137.202.16], delay 0.00000, dispersion 64.00000 transmitted 4, in filter 4 reference time: 00000000.00000000 Thu, Feb 7 2036 0:28:16.000 originate timestamp: 00000000.00000000 Thu, Feb 7 2036 0:28:16.000 transmit timestamp: d1a71a93.1f16c1e3 Sat, Jun 18 2011 7:37:39.121 filter delay: 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 filter offset: 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 delay 0.00000, dispersion 64.00000 offset 0.000000 server 216.45.57.38, port 123 stratum 0, precision 0, leap 00, trust 000 refid [216.45.57.38], delay 0.00000, dispersion 64.00000 transmitted 4, in filter 4 reference time: 00000000.00000000 Thu, Feb 7 2036 0:28:16.000 originate timestamp: 00000000.00000000 Thu, Feb 7 2036 0:28:16.000 transmit timestamp: d1a71a93.524a05dd Sat, Jun 18 2011 7:37:39.321 filter delay: 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 filter offset: 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 delay 0.00000, dispersion 64.00000 offset 0.000000 server 64.6.144.6, port 123 stratum 0, precision 0, leap 00, trust 000 refid [64.6.144.6], delay 0.00000, dispersion 64.00000 transmitted 4, in filter 4 reference time: 00000000.00000000 Thu, Feb 7 2036 0:28:16.000 transmitted 4, in filter 4 reference time: 00000000.00000000 Thu, Feb 7 2036 0:28:16.000 originate timestamp: 00000000.00000000 Thu, Feb 7 2036 0:28:16.000 transmit timestamp: d1a71a93.524a05dd Sat, Jun 18 2011 7:37:39.321 filter delay: 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 filter offset: 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 delay 0.00000, dispersion 64.00000 offset 0.000000 server 64.6.144.6, port 123 stratum 0, precision 0, leap 00, trust 000 refid [64.6.144.6], delay 0.00000, dispersion 64.00000 transmitted 4, in filter 4 reference time: 00000000.00000000 Thu, Feb 7 2036 0:28:16.000 originate timestamp: 00000000.00000000 Thu, Feb 7 2036 0:28:16.000 transmit timestamp: d1a71a93.857c6fbd Sat, Jun 18 2011 7:37:39.521 filter delay: 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 filter offset: 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 delay 0.00000, dispersion 64.00000 offset 0.000000 18 Jun 07:37:40 ntpdate[10737]: no server suitable for synchronization found

    Read the article

  • Lock-Free, Wait-Free and Wait-freedom algorithms for non-blocking multi-thread synchronization.

    - by GJ
    In multi thread programming we can find different terms for data transfer synchronization between two or more threads/tasks. When exactly we can say that some algorithem is: 1)Lock-Free 2)Wait-Free 3)Wait-Freedom I understand what means Lock-free but when we can say that some synchronization algorithm is Wait-Free or Wait-Freedom? I have made some code (ring buffer) for multi-thread synchronization and it use Lock-Free methods but: 1) Algorithm predicts maximum execution time of this routine. 2) Therad which call this routine at beginning set unique reference, what mean that is inside of this routine. 3) Other threads which are calling the same routine check this reference and if is set than count the CPU tick count (measure time) of first involved thread. If that time is to long interrupt the current work of involved thread and overrides him job. 4) Thread which not finished job because was interrupted from task scheduler (is reposed) at the end check the reference if not belongs to him repeat the job again. So this algorithm is not really Lock-free but there is no memory lock in use, and other involved threads can wait (or not) certain time before overide the job of reposed thread. Added RingBuffer.InsertLeft function: function TgjRingBuffer.InsertLeft(const link: pointer): integer; var AtStartReference: cardinal; CPUTimeStamp : int64; CurrentLeft : pointer; CurrentReference: cardinal; NewLeft : PReferencedPtr; Reference : cardinal; label TryAgain; begin Reference := GetThreadId + 1; //Reference.bit0 := 1 with rbRingBuffer^ do begin TryAgain: //Set Left.Reference with respect to all other cores :) CPUTimeStamp := GetCPUTimeStamp + LoopTicks; AtStartReference := Left.Reference OR 1; //Reference.bit0 := 1 repeat CurrentReference := Left.Reference; until (CurrentReference AND 1 = 0)or (GetCPUTimeStamp - CPUTimeStamp > 0); //No threads present in ring buffer or current thread timeout if ((CurrentReference AND 1 <> 0) and (AtStartReference <> CurrentReference)) or not CAS32(CurrentReference, Reference, Left.Reference) then goto TryAgain; //Calculate RingBuffer NewLeft address CurrentLeft := Left.Link; NewLeft := pointer(cardinal(CurrentLeft) - SizeOf(TReferencedPtr)); if cardinal(NewLeft) < cardinal(@Buffer) then NewLeft := EndBuffer; //Calcolate distance result := integer(Right.Link) - Integer(NewLeft); //Check buffer full if result = 0 then //Clear Reference if task still own reference if CAS32(Reference, 0, Left.Reference) then Exit else goto TryAgain; //Set NewLeft.Reference NewLeft^.Reference := Reference; SFence; //Try to set link and try to exchange NewLeft and clear Reference if task own reference if (Reference <> Left.Reference) or not CAS64(NewLeft^.Link, Reference, link, Reference, NewLeft^) or not CAS64(CurrentLeft, Reference, NewLeft, 0, Left) then goto TryAgain; //Calcolate result if result < 0 then result := Length - integer(cardinal(not Result) div SizeOf(TReferencedPtr)) else result := cardinal(result) div SizeOf(TReferencedPtr); end; //with end; { TgjRingBuffer.InsertLeft } RingBuffer unit you can find here: RingBuffer, CAS functions: FockFreePrimitives, and test program: RingBufferFlowTest Thanks in advance, GJ

    Read the article

  • Thread Synchronization - UI thread and Worker thread

    This article describes how a Worker thread can take the control of the UI and can update the UI, created by the UI thread. This will be useful when a worker thread needs to update the UI in the mid of the background processing or on the completion without relying on UI thread to synchronize the work

    Read the article

  • Enabling Hyper-V Integrated Services Time Sync Services versus Internet Time Synchronization

    - by cpuguru
    Should I deselect the "Synchronize with an Internet Time Server" checkbox under the VM's "Date and Time - Internet Time Settings" tab if the "Time Synchronization Service" for a Hyper-V-based Virtual Machine is enabled? One of the Integration Services that Hyper-V provides is the Time Synchronization Service, which can be enabled/disabled by going to a VM's Settings-Integration Services setting in the Management section. I believe this is checked by default. When you install a Windows Server 2008 OS in a VM on the Hyper-V server, it comes with the "Synchronize with an Internet Time Server" option set, pointing to "time.windows.com". I'd think that if the parent Hyper-V server is set to one time server, and the child VM is pointing to a different time server, there would be a momentary blip if the two are not spot on with their times when the synchronization services run. So the question is, which time sync service should I use? I'm assuming not both. And what is the advantage of one over the other? Note: This question assumes that the machines are not joined to a domain. If they were, the machines would also try to update their time against the domain controller with the primary domain controller role too, right? Thanks!

    Read the article

  • Metaphor for task synchronization [closed]

    - by nkint
    I'm looking for a metaphor. A friend of mine taught me to use metaphors from nature, everyday life, math, and use them to design my projects. They can help in creating a better design or better understanding or the problem, and they are cool. Now I'm working on a project with hardware and micro-controllers in C. For convenience, I have decided to use multiple micro-controllers as co-processor units for real-time (the slaves) and a master. This has saved me a lot of headache: I can code the main logic in the master without paying too much attention to super optimizing everything; I don't care if I need some blocking-call; I don't worry about serial communication with the computer. I just send messages to the slaves and they are super fast super in real time. I like my design and it seems to work well. So here are the important concepts that I'm trying capture in the metaphor: hierarchy of processing Not using one big brain but rather several small, distributed brain units using distributed power or resources I'm looking for a good metaphor for this concept of having one unit synchronize the work of all the others. Preferably, the metaphor would come from nature, biology, or zoology.

    Read the article

  • Healthcare Mobile Database Synchronization Demonstration

    - by Jim Connors
    Like many of you, I learn best by getting my hands dirty.  When confronted with the task of understanding a new set of products and technologies and figuring out how they might apply to a vertical industry like healthcare, I set out to create a demonstration.  The video that follows aims to show how the Oracle embedded software portfolio can be applied to a healthcare application.  The demonstration utilizes among others, Java SE Embedded, Berkeley DB, Apache Tomcat, Oracle 11gR2 and Oracle Database Mobile Server. Eric Jensen gives a great critique and description of the demo here.  To sum it up, we aim to show how live medical data can be collected on a medical device, stored in a local database, synchronized to a master database and furthermore propagated to a mobile phone (Android) application.  Come take a look!

    Read the article

  • Multi-Threaded Pipelined Game Engine Data Synchronization Questions

    - by Douglas
    Let's say I'm setting up a worker pool based game engine with pipelining. Let's say I have 4 stages in my pipeline as such: Stage 1: Physics Stage 2: AI/Input Stage 3: Game Logic Stage 4: Rendering Now let's say that the physics detects a collision between a bullet and a character in stage 1. Two frames later the game logic may choose to remove that bullet from the simulation, however none of the other copies of the data for the other pipeline stages will get this information. How is this sort of thing and other things like it get handled? Do you generally make changes like this to every pipeline stage's data at the end of a frame?

    Read the article

  • Data Synchronization in mobile apps - multiple devices, multiple users

    - by ProgrammerNewbie
    I'm looking into building my first mobile app. One of the core features of the application is that multiple devices/users will have access to the same data -- and all of them will have CRUD rights. I believe the architecture should involve a central server where all the data is stored. The devices will use an API to interact with the server to perform its data operations (e.g. adding a record, editing a record, deleting a record). I imagine a scenario where synchronizing the data will become a problem. Assume the application should work when it is not connected to the Internet, and thus cannot communicate with this central server. So: User A is offline and edits record #100 User B is offline and edits record #100 User C is offline and deletes record #100 User C goes online (presumably, record #100 should get deleted on the server) User A and B goes online, but the records they edited no longer exist All sorts of scenarios similar to the above can come up. How is this generally handled? I plan to use MySQL, but am wondering if it's not appropriate for such a problem.

    Read the article

  • Unison synchronization problem. Roots are not identical after synchronization.

    - by binary255
    Hi. When I synchronize two folders using Unison, only one of the roots seems to be affected. Below are all the information I would think is necessary to figure out why it is working like it is. I'm using $ unison -version unison version 2.27.57 From the Ubuntu repositories. My work laptop: $ echo $UNISONLOCALHOSTNAME worklaptop $ pwd /home/userfoo $ ls -lAR .unison* .unison: total 8 drwxr-xr-x 2 userfoo userfoo 4096 2010-04-26 11:39 backups -rw-r--r-- 1 userfoo userfoo 231 2010-04-26 11:38 default.prf .unison/backups: total 0 .unisonroot: total 0 $ cat .unison/default.prf # Roots of the synchronization root = /home/userfoo/.unisonroot root = ssh://devel//home/userbar/.unisonroot path = * backuplocation = central backupdir = /home/.unison/backups backupprefix = $VERSION.bak $ mkdir .unisonroot/aDirectoryFrom-$UNISONLOCALHOSTNAME $ echo something >.unisonroot/aFileFrom-$UNISONLOCALHOSTNAME $ ls .unisonroot/ aDirectoryFrom-worklaptop aFileFrom-worklaptop And the Ubuntu server I want to synchronize with: $ echo $UNISONLOCALHOSTNAME workcmpuserbardevel $ pwd /home/userbar $ ls -lAR .unison* .unison: total 4 drwxr-xr-x 2 userbar userbar 4096 2010-04-26 11:38 .unison .unison/.unison: total 0 .unisonroot: total 0 $ mkdir .unisonroot/aDirectoryFrom-$UNISONLOCALHOSTNAME $ echo something >.unisonroot/aFileFrom-$UNISONLOCALHOSTNAME $ ls .unisonroot/ aDirectoryFrom-workcmpuserbardevel aFileFrom-workcmpuserbardevel I perform the unison synchronization: $ echo $UNISONLOCALHOSTNAME worklaptop $ unison Contacting server... Connected [//worklaptop//home/userfoo/.unisonroot -> //workcmpuserbardevel//home/userbar/.unisonroot] Looking for changes Warning: No archive files were found for these roots, whose canonical names are: /home/userfoo/.unisonroot //workcmpuserbardevel//home/userbar/.unisonroot This can happen either because this is the first time you have synchronized these roots, or because you have upgraded Unison to a new version with a different archive format. Update detection may take a while on this run if the replicas are large. Unison will assume that the 'last synchronized state' of both replicas was completely empty. This means that any files that are different will be reported as conflicts, and any files that exist only on one replica will be judged as new and propagated to the other replica. If the two replicas are identical, then no changes will be reported. If you see this message repeatedly, it may be because one of your machines is getting its address from DHCP, which is causing its host name to change between synchronizations. See the documentation for the UNISONLOCALHOSTNAME environment variable for advice on how to correct this. Donations to the Unison project are gratefully accepted: http://www.cis.upenn.edu/~bcpierce/unison Press return to continue.[<spc>] Waiting for changes from server Reconciling changes local workcmps... dir ----> aDirectoryFrom-worklaptop [f] file ----> aFileFrom-worklaptop [f] Proceed with propagating updates? [] y Propagating updates UNISON 2.27.57 started propagating changes at 11:49:14 on 26 Apr 2010 [BGN] Copying aDirectoryFrom-worklaptop from /home/userfoo/.unisonroot to //workcmpuserbardevel//home/userbar/.unisonroot [BGN] Copying aFileFrom-worklaptop from /home/userfoo/.unisonroot to //workcmpuserbardevel//home/userbar/.unisonroot [END] Copying aDirectoryFrom-worklaptop [END] Copying aFileFrom-worklaptop UNISON 2.27.57 finished propagating changes at 11:49:14 on 26 Apr 2010 Saving synchronizer state Synchronization complete (2 items transferred, 0 skipped, 0 failures) And then check the .unisonroot directory on the computer I started the synchronization from: $ ls .unisonroot/ aDirectoryFrom-worklaptop aFileFrom-worklaptop And on the server: $ echo $UNISONLOCALHOSTNAME workcmpuserbardevel $ ls .unisonroot/ aDirectoryFrom-worklaptop aFileFrom-worklaptop aDirectoryFrom-workcmpuserbardevel aFileFrom-workcmpuserbardevel As can be seen above, the contents of the laptop .unisonroot has not changed while the servers .unisonroot has. The desired result would have been that the two folders would have ended up being identical, holding the union of the contents of the two roots.

    Read the article

  • Conflict resolution for two-way sync

    - by K.Steff
    How do you manage two-way synchronization between a 'main' database server and many 'secondary' servers, in particular conflict resolution, assuming a connection is not always available? For example, I have an mobile app that uses CoreData as the 'database' on the iOS and I'd like to allow users to edit the contents without Internet connection. In the same time, this information is available on a website the devices will connect to. What do I do if/when the data on the two DB servers is in conflict? (I refer to CoreData as a DB server, though I am aware it is something slightly different.) Are there any general strategies for dealing with this sort of issue? These are the options I can think of: 1. Always use the client-side data as higher-priority 2. Same for server-side 3. Try to resolve conflicts by marking each field's edit timestamp and taking the latest edit Though I'm certain the 3rd option will open room for some devastating data corruption. I'm aware that the CAP theorem concerns this, but I only want eventual consistency, so it doesn't rule it out completely, right? Related question: Best practice patterns for two-way data synchronization. The second answer to this question says it probably can't be done.

    Read the article

  • List with non-null elements ends up containing null. A synchronization issue?

    - by Alix
    Hi. First of all, sorry about the title -- I couldn't figure out one that was short and clear enough. Here's the issue: I have a list List<MyClass> list to which I always add newly-created instances of MyClass, like this: list.Add(new MyClass()). I don't add elements any other way. However, then I iterate over the list with foreach and find that there are some null entries. That is, the following code: foreach (MyClass entry in list) if (entry == null) throw new Exception("null entry!"); will sometimes throw an exception. I should point out that the list.Add(new MyClass()) are performed from different threads running concurrently. The only thing I can think of to account for the null entries is the concurrent accesses. List<> isn't thread-safe, after all. Though I still find it strange that it ends up containing null entries, instead of just not offering any guarantees on ordering. Can you think of any other reason? Also, I don't care in which order the items are added, and I don't want the calling threads to block waiting to add their items. If synchronization is truly the issue, can you recommend a simple way to call the Add method asynchronously, i.e., create a delegate that takes care of that while my thread keeps running its code? I know I can create a delegate for Add and call BeginInvoke on it. Does that seem appropriate? Thanks.

    Read the article

  • SharePoint 2010 User Profile Synchronization

    - by manemawanna
    Hello, I'm completely new to working with SharePoint and Windows Server, but last week I was given a small brief to play with SharePoint 2010 to see how I got along with it. Anyway I've set up a SharePoint server and had a mess around to get some new sites and pages created etc, but I'm now looking to have a try at importing some AD groups. As part of this I've look at these tutorials, here and here. So far I've got through to the process of starting the User Profile Service which works fine, but when I get it starting the User Profile Synchronization service it sits on starting. But when I refresh the page or go to the monitoring section it shows it as aborted. Now I'm new to administering servers like I say and when I start the User Profile Synchronization service it tries to run as NT AUTHORITY\NETWORK SERVICE and asks for a password so I've been providing it with the admin password, now I'm not sure if this is part of the issue or not as I've checked the log files and they seem to say that it doesn't have permissions, which is fair enough, but I can't see how you can change the account even if I wanted to. So if anyone could help it would be appreciated, if you need any further information to help with an answer, just let me know.

    Read the article

  • What is a good design pattern / lib for iOS 5 to synchronize with a web service?

    - by Junto
    We are developing an iOS application that needs to synchronize with a remote server using web services. The existing web services have an "operations" style rather than REST (implemented in WCF but exposing JSON HTTP endpoints). We are unsure of how to structure the web services to best fit with iOS and would love some advice. We are also interested in how to manage the synchronization process within iOS. Without going into detailed specifics, the application allows the user to estimate repair costs at a remote site. These costs are broken down by room and item. If the user has an internet connection this data can be sent back to the server. Multiple photographs can be taken of each item, but they will be held in a separate queue, which sends when the connection is optimal (ideally wifi). Our backend application controls the unique ids for each room and item. Thus, each time we send these costs to the server, the server echoes the central database ids back, thus, that they can be synchronized in the mobile app. I have simplified this a little, since the operations contract is actually much larger, but I just want to illustrate the basic requirements without complicating matters. Firstly, the web service architecture: We currently have two operations: GetCosts and UpdateCosts. My assumption is that if we used a strict REST architecture we would need to break our single web service operations into multiple smaller services. This would make the services much more chatty and we would also have to guarantee a delivery order from the app. For example, we need to make sure that containing rooms are added before the item. Although this seems much more RESTful, our perception is that these extra calls are expensive connections (security checks, database calls, etc). Does the type of web api (operation over service focus) determine chunky vs chatty? Since this is mobile (3G), are we better handling lots of smaller messages, or a few large ones? Secondly, the iOS side. What is the current advice on how to manage data synchronization within the iOS (5) app itself. We need multiple queues and we need to guarantee delivery order in each queue (and technically, ordering between queues). The server needs to control unique ids and other properties and echo them back to the application. The application then needs to update an internal database and when re-updating, make sure the correct ids are available in the update message (essentially multiple inserts and updates in one call). Our backend has a ton of business logic operating on these cost estimates. We don't want any of this in the app itself. Currently the iOS app sends the cost data, and then the server echoes that data back with populated ids (and other data). The existing cost data is deleted and the echoed response data is added to the client database on the device. This is causing us problems, because any photos might not have been sent, but the original entity tree has been removed and replaced. Obviously updating the costs tree rather than replacing it would remove this problem, but I'm not sure if there are any nice xcode libraries out there to do such things. I welcome any advice you might have.

    Read the article

  • How is thread synchronization implemented, at the assembly language level?

    - by Martin
    While I'm familiar with concurrent programming concepts such as mutexes and semaphores, I have never understood how they are implemented at the assembly language level. I imagine there being a set of memory "flags" saying: lock A is held by thread 1 lock B is held by thread 3 lock C is not held by any thread etc But how is access to these flags synchronized between threads? Something like this naive example would only create a race condition: mov edx, [myThreadId] wait: cmp [lock], 0 jne wait mov [lock], edx ; I wanted an exclusive lock but the above ; three instructions are not an atomic operation :(

    Read the article

  • How to use locks/synchronization here

    - by MasterGberry
    I have this code block here and i need to make sure the rankedPlayersWaitingForMatch is synchronized between threads properly. I was going to use synchronize but that i don't think will work here because of the variable being used in the if statement. I read online about final Lock lock = new ReentrantLock(); but I am a bit confused on how to use it in this case properly with the try/finally block. Can I get a quick example? Thanks // start synchronization if (rankedPlayersWaitingForMatch.get(rankedType).size() >= 2) { Player player1 = rankedPlayersWaitingForMatch.get(rankedType).remove(); Player player2 = rankedPlayersWaitingForMatch.get(rankedType).remove(); // end synchronization // ... I don't want this all to be synchronized, just after the first 2 remove() } else { // end synchronization // ... }

    Read the article

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

< Previous Page | 1 2 3 4 5 6 7 8 9 10 11 12  | Next Page >