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  • how can I save/keep-in-sync an in-memory graph of objects with the database?

    - by Greg
    Question - What is a good best practice approach for how can I save/keep-in-sync an jn-memory graph of objects with the database? Background: That is say I have the classes Node and Relationship, and the application is building up a graph of related objects using these classes. There might be 1000 nodes with various relationships between them. The application needs to query the structure hence an in-memory approach is good for performance no doubt (e.g. traverse the graph from Node X to find the root parents) The graph does need to be persisted however into a database with tables NODES and RELATIONSHIPS. Therefore what is a good best practice approach for how can I save/keep-in-sync an jn-memory graph of objects with the database? Ideal requirements would include: build up changes in-memory and then 'save' afterwards (mandatory) when saving, apply updates to database in correct order to avoid hitting any database constraints (mandatory) keep persistence mechanism separate from model, for ease in changing persistence layer if needed, e.g. don't just wrap an ADO.net DataRow in the Node and Relationship classes (desirable) mechanism for doing optimistic locking (desirable) Or is the overhead of all this for a smallish application just not worth it and I should just hit the database each time for everything? (assuming the response times were acceptable) [would still like to avoid if not too much extra overhead to remain somewhat scalable re performance]

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  • How to build a windows/web application that stores data locally and sync's with remote database?

    - by Jason
    Hello, I am needing to build an application that stores data locally and then synchronizes with a remote MS SQL database. I am not sure how to go about doing this. Enter data offline on a form and store the data. Synchronize the data with a remote MS SQL database when online. There will be many users who enter data offline, the local database on each pc needs to update when online and grab the 30 most recent records for use offline. Example: Each day users will enter data on their "form". The users will be offline. The users will return to the office and need to sync with the "online" database. The next morning the users will need to sync with the online database before going offline. They will need to have offline access to the 30 most recent records. (They will use the 30 records for charting/graphing while they are offline) I am very new to building apps. I have VS 2010. I am wondering where to start? What language to use? Is there a "framework" for doing this type of app? Any info or suggestions would be greatly appreciated. Thanks!

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  • In sync query calls, one query causing other query to run slower. Why?

    - by Irchi
    Sorry for the long question, but I think this is an interesting situation and I couldn't find any explanations for it: I was involved in optimization of an application that performed a large number of sequential SELECT and INSERT statements on a single dedicated SQL Server database. The process needs to INSERT a large number of records into a table, but for each of them there should be some value mappings, which performed using SELECT statements on another table in the same database. For a specific execution, it took 90 minutes to run. I used a profiler (JProfiler - the application is Java-based) to determine how much time does each part of the application take. It yields that 60% of the time was spent on INSERT method calls, and almost 20% on SELECT calls (the rest distributed in other parts). After some trials, I came to this situation: I commented out the INSERT query that took 60% of the time. I was expecting for the total run time to be around 35 minutes, as I have removed 60% of the 90 minutes. But the whole process took the same 90 minutes (doing only SELECTs and nothing else), but each SELECT took longer this time! Everything was running sync, there were no async calls. And there was only one single thread of execution. SELECT and INSERT queries are very simple, and don't have anything special, and they are on different tables, but on the same DB. I tested with both the DB on the application machine, and on a remote network machine. I can't think of any explanation for this, as the Profiler (Application profiler, not SQL Profiler) reported the changes in the method call times, and by removing INSERT statements SELECT statements took longer to run. Can anyone give me some kind of explanation of what could have happened? (there can't be cache / query optimization stuff, because the queries were run in sync, and in a single thread, and it was far from affecting the cache this much) I should note that the bottleneck of the speed was in SQL server, using most of the CPU time.

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  • Access denied error while mounting a shared folder?

    - by SSH
    I am a linux newbie and I have a very basic question. I have three machines - machineA 10.108.24.132 machineB 10.108.24.133 machineC 10.108.24.134 and all those machines have Ubuntu 12.04 installed in it and I have root access to all those three machines. Now I am supposed to do below things in my above machines - Create mount point /opt/exhibitor/conf Mount the directory in all servers. sudo mount <NFS-SERVER>:/opt/exhibitor/conf /opt/exhibitor/conf/ I have already created /opt/exhibitor/conf directory in all those three machines as mentioned above. Now I am trying to create a Mount Point on all those three machines. So I followed the below process - Install NFS support files and NFS kernel server in all the above three machines $ sudo apt-get install nfs-common nfs-kernel-server Create the shared directory in all the above three machines $ mkdir /opt/exhibitor/conf/ Edited the /etc/exports and added the entry like this in all the above three machines - # /etc/exports: the access control list for filesystems which may be exported # to NFS clients. See exports(5). # # Example for NFSv2 and NFSv3: # /srv/homes hostname1(rw,sync,no_subtree_check) hostname2(ro,sync,no_subtree_check) # # Example for NFSv4: # /srv/nfs4 gss/krb5i(rw,sync,fsid=0,crossmnt,no_subtree_check) # /srv/nfs4/homes gss/krb5i(rw,sync,no_subtree_check) # /opt/exhibitor/conf/ 10.108.24.*(rw) Run exportfs in all the above three machines root@machineA:/# exportfs -rv exportfs: /etc/exports [1]: Neither 'subtree_check' or 'no_subtree_check' specified for export "10.108.24.*:/opt/exhibitor/conf/". Assuming default behaviour ('no_subtree_check'). NOTE: this default has changed since nfs-utils version 1.0.x exporting 10.108.24.*:/opt/exhibitor/conf Now I did showmount on machineA root@machineA:/# showmount -e 10.108.24.132 Export list for 10.108.24.132: /opt/exhibitor/conf 10.108.24.* And also I have started the NFS server like this in all the above three machines - sudo /etc/init.d/nfs-kernel-server start And now when I did this, I am getting an error - root@machineA:/# sudo mount -t nfs 10.108.24.132:/opt/exhibitor/conf /opt/exhibitor/conf/ mount.nfs: access denied by server while mounting 10.108.24.132:/opt/exhibitor/conf I have also tried doing the same thing from machineB and machineC as well and still I get the same error- root@machineB:/# sudo mount -t nfs 10.108.24.132:/opt/exhibitor/conf /opt/exhibitor/conf/ root@machineC:/# sudo mount -t nfs 10.108.24.132:/opt/exhibitor/conf /opt/exhibitor/conf/ Did my /etc/exports file looks good? As I have the same content in all the three machines. And also are there any logs related to NFS which I can see to find any clues? Any idea what wrong I am doing here? UPDATE:- So my etc/exports files would be like this in all the three machines - # /etc/exports: the access control list for filesystems which may be exported # to NFS clients. See exports(5). # # Example for NFSv2 and NFSv3: # /srv/homes hostname1(rw,sync,no_subtree_check) hostname2(ro,sync,no_subtree_check) # # Example for NFSv4: # /srv/nfs4 gss/krb5i(rw,sync,fsid=0,crossmnt,no_subtree_check) # /srv/nfs4/homes gss/krb5i(rw,sync,no_subtree_check) # /opt/exhibitor/conf/ 10.108.24.132(rw) /opt/exhibitor/conf/ 10.108.24.133(rw) /opt/exhibitor/conf/ 10.108.24.134(rw) Just a quick check - The IP Address that I am taking for each machine as mentioned above is like this - root@machineB:/# ifconfig eth0 Link encap:Ethernet HWaddr 00:50:56:ad:5b:a7 inet addr:10.108.24.133 Bcast:10.108.27.255 Mask:255.255.252.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:5696812 errors:0 dropped:12462 overruns:0 frame:0 TX packets:5083427 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:7904369145 (7.9 GB) TX bytes:601844910 (601.8 MB) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:187144 errors:0 dropped:0 overruns:0 frame:0 TX packets:187144 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:24012302 (24.0 MB) TX bytes:24012302 (24.0 MB) Here the IP Address that I am taking for machineB is 10.108.24.133.

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  • Best way to say "sync all system clocks to this server, when and ONLY when I say so?" Mixed setup of Windows+Linux servers.

    - by twblamer
    Title pretty much explains it. Let's say there's 100 servers, various versions of Windows and Linux, and one Windows server is the "master clock." I did look at this question: How do I synchronize clocks between Linux and Windows? This hints that ntp can do what I want if I run "ntpd -q" on a client (?). If I install ntp I also need to guarantee that it will only sync the times when I force it to. Even better if I have a log that tells me every time a sync was performed. I'm doing benchmark runs and I need to be able to say something like this: "Clocks were synced on all the benchmark systems at 09:42:01am on the master. A benchmark run was then initiated and allowed to run for six hours. None of the system clocks were altered during this time interval." I understand there is subsequent clock drift, but for now that's the way we're doing things and I'm doing it with a manual process. I'd rather at least automate the one-time sync.

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  • Has anyone achieved true differential sync with rsync in ESXi?

    - by Julius
    Berate me later on the fact that I'm using the service console to do anything in ESXi... I've got a working rsync binary (v3.0.4) that I can use in ESXi 4.1U1. I tend to use rsync over cp when copying VM's or backups from one local datastore to another local datastore. I've used rsync to copy data from one ESXi box to another but that was just for small files. In now trying to do true differential syncs of backups taken via ghettoVCB between my primary ESXi machine and a secondary one. But even when I do this locally (one datastore to another datastore on the same ESXi machine) rsync appears to copy the files in their entirety. I've got two VMDK's totally 80GB in size, and rsync still takes anywhere between 1 and 2 hours but the VMDK's aren't growing that much daily. Below is the rsync command I'm executing. I am copying locally because ultimately these files will get copied onto a datastore created from a LUN on a remote system. Its not an rsync that'll be serviced by an rsync daemon on a remote system. rsync -avPSI VMBACKUP_2011-06-10_02-27-56/* VMBACKUP_2011-06-01_06-37-11/ --stats --itemize-changes --existing --modify-window=2 --no-whole-file sending incremental file list >f..t...... VM-flat.vmdk 42949672960 100% 15.06MB/s 0:45:20 (xfer#1, to-check=5/6) >f..t...... VM.vmdk 556 100% 4.24kB/s 0:00:00 (xfer#2, to-check=4/6) >f..t...... VM.vmx 3327 100% 25.19kB/s 0:00:00 (xfer#3, to-check=3/6) >f..t...... VM_1-flat.vmdk 42949672960 100% 12.19MB/s 0:56:01 (xfer#4, to-check=2/6) >f..t...... VM_1.vmdk 558 100% 2.51kB/s 0:00:00 (xfer#5, to-check=1/6) >f..t...... STATUS.ok 30 100% 0.02kB/s 0:00:01 (xfer#6, to-check=0/6) Number of files: 6 Number of files transferred: 6 Total file size: 85899350391 bytes Total transferred file size: 85899350391 bytes Literal data: 2429682778 bytes Matched data: 83469667613 bytes File list size: 129 File list generation time: 0.001 seconds File list transfer time: 0.000 seconds Total bytes sent: 2432530094 Total bytes received: 5243054 sent 2432530094 bytes received 5243054 bytes 295648.92 bytes/sec total size is 85899350391 speedup is 35.24 Is this because ESXi is itself making so many changes to the VMDK's that as far as rsync is concerned the entire file has to be retransmitted? Has anyone actually achieved actual diff sync with ESXi?

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  • How to sync bookmarks across Google Chrome and Mozilla Firefox bookmarks?

    - by ViliusK
    How to sync bookmarks across Google Chrome and Mozilla Firefox bookmarks? As I, currently, understand, Google Chrome puts bookmarks seperatly from Google Bookmarks, which is accessible in Firefox by using Google Toolbar for Firefox. Right? So how should I synchronize my browsers? I use Google Chrome as my primary browser and it works good and bookmarks are synchronized across number of computers I'm using. Thanks, viliusk

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  • Subversion: How to make local changes to a file *never* check in, but have it sync with remote anyway?

    - by Niels Heidenreich
    I have a file with local changes that should never sync back to the repository because it's for my local installation only. But if that same file is changed in the repo, I want those changes to update my local copy, anyway. At the moment, the file in question always shows up in the list of changes when I want to check-in my changes, and I have to manually exclude it from the check-in. How do I make it so that I can just update, with the above restriction in place? Thanks :)

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  • How can I setup a flexible local web development environment I can easily sync with a production, Amazon AWS based environment?

    - by user607057
    I'm running on an OS X environment and would like to create a flexible web development environment locally... including the option to run on an Nginx server for my PHP-based application. At the end of the day (or, development cycle), I'd like to be able to hit a switch and have it all sync over to Amazon AWS hosting (EC2, S3) - instances, databases, files, configurations, and all. Are there any simple ways to do this?

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  • How do I keep a datastructure in sync across several servers in Java?

    - by sanity
    Have a Map which contains objects that I want to keep in sync across multiple servers, such that if objects in the map are created, deleted, or modified - this is reflected immediately (ie. within a second or two) across all servers, in a way that can potentially scale up to tens of servers. Is there a lightweight open source Java tool that can do something like this? I'm aware of Terracotta but it is rather heavy weight for what I need.

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  • iPhone 3G refuses to transfer purchased apps to iTunes

    - by andynormancx
    My iPhone 3G refuses to transfer purchased apps to iTunes. This is causing me major problems with syncing. Whenever I attempt to transfer apps from the iPhone to iTunes it goes through the motions, but never actually transfers anything. It displays the various apps in the info area at the top of the screen, but the progress bar never advances. In comparison when I sync other iPhones, using the same install of iTunes, the progress bar advances and apps are transferred. The same also happens on clean installs of iTunes on other computers, it seems to be my iPhone that is the common factor. I have tried restoring the phone from a backup, which makes no difference. This started happening months ago and the phone has since been upgraded to 3.0 and 3.1, but the problem still persists. Originally it was just a minor irritation, but I made and attempt to fix it which has made things worse. I deleted all the apps from with iTunes and then did "Transfer purchases" in the hope that it might fix something. It didn't fix anything. Also, I cannot now sync at all. If I do sync iTunes now does "transferring purchases", fails to transfer and then deletes all the apps (and data) from my iPhone. It also means I can't sync music, podcasts or anything else. I can't sync anything else, because I can't temporarily turn off app syncing because then iTunes warns that the apps on the iPhone will be deleted. I also tried de-authorising and re-authorising. What can I do to get app syncing working again ? P.S. I have considered deleting all the apps and reinstalling them one by one, in the hope that it will fix the problem. However I don't really want to embark on doing that for 55+ apps and re-entering login details etc for the apps that need them, especially as I might then find out it didn't solve the problem. Update: The latest update to iTunes 9 has improved things in one key aspect. If I let a sync run to completion iTunes no longer deletes all the apps from my phone. So I can now sync all my other data, even if I still can't sync my apps. Resolved: See my answer to the question for how I finally resolved the problem.

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  • Sync Framework - In order to evaluate an indexed property, the property must be qualified and the ar

    - by Khor
    I trying to do a snapshot between SQLCE 3.5 SP1 and SQL Server 2008 by using the sync framework. I received a inner exception stated that "{"Unable to enumerate changes at the DbServerSyncProvider for table 'ArInvoice' in synchronization group 'ArInvoiceSyncTableSyncGroup'."}". The inner text for the inner exception stated that "Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.". And the item for the inner exception indicated that "In order to evaluate an indexed property, the property must be qualified and the arguments must be explicitly supplied by the user.". What is going wrong? Any setting i miss out?

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  • How do you handle the deletion of your model working with ViewModels and keeping them in sync ?

    - by Lisa
    Hello, these could be my entity relations: 1 Pupil has 1 Chair 1 Pupil has N Documents 1 Pupil has N Marks 1 Pupil has N IncidentReports etc... So with that sample I get 4 IEnumerable from my database put each into an ObservableCollection. Now I have 4 different Views each bound to one of those 4 collections. Lets assume I delete a single PupilViewModel in the AdministrationController which is the only View where I can delete a PupilViewModel. Now I have to inform 3 other Controller and their ObservableCollections about the one deleted PupilViewModel to keep the whole application synchronized... thats stupid somehow. Do you have any good advice on that scenario? AND it gets even worse. If I delete a schoolclass I have to sync the pupils everywhere AND the documents or incidentreports or marks... gush... o_O

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  • Microsoft Sync Framework - Local DB and Remote DB have to have the same schema?

    - by Josh
    When using MSF, is it implied in the technology that the sync tables are supposed to be 1-1? The reason I'm wondering is that if I'm synching from a SQL2005 database to a SQLCE, I might want the CE one to be a little more flattened out so I can get data out with a simpler SELECT statement (as CE does not support sprocs). For example, I might have a tblCustomer, tblOrder, and tblCustomerOrder in the central database, but in the local databases one table with all the data might be preferred. Of course I'd still want the updates to reflect back and forth between the two databases. Does MSF make this possible, or does the local DB have to have the same tables as the central?

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  • iphone poll application to sync with myspace or facebook poll.

    - by Zach
    Hi, We are developing an iphone application, which requires us to add polling(survey) functionality in the app. We also have same poll in either MySpace or Facebook. We have to sync the polling data to our iphone application. How can we achieve this? We have found some third party polling service provider like Zoomerang, Poll Daddy polls, etc., but they don't have supporting API for iphone application or at least one we are not aware of. If anyone can shed light on this on how to proceed with this, it will be really very helpful. Thanks in advance. Zach.

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  • How do i keep my DB and lucene in sync?

    - by acidzombie24
    So i can have a transaction in sql. But i am sure its not a good idea to wait in the middle of a transaction for lucene to finish also i am unsure if lucene is permanently saved in the DB until i do something there. Whats the best way to keep my DB and lucene in sync? I am thinking of adding a lucene_queue in my sql db and everytime i make a change i add it into the queue (removing older queue if any) and delete it once it is done. Is this the best way? Also i am unsure how to make lucene permanently keep the changes i made and how frequent i can/should do it.

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  • How to keep statefull web clients in sync, when multiple clients are looking at the same data?

    - by Hilbrand
    In a RIA web client, created with GWT, the state is maintained in the web client, while the server is (almost) stateless (this is the preferred technique to keep the site scalable). However, if multiple users looking at the same data in their browser and one user changes something, which is send to the server and stored in the database, the other users still have the old data in their browser state. For example a tree is shown and one of the users adds/removes an item from the tree. Since there can be a lot of state in the client, what is the best technique to keep the state in the clients in sync? Are there any java frameworks that take care of this?

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  • Why is my WPF splash screen progress bar out of sync with the execution of the startup steps?

    - by denny_ch
    Hello, I've implemented a simple WPF splash screen window which informs the user about the progress of the application startup. The startup steps are defined this way: var bootSequence = new[] { new {Do = (Action) InitLogging, Message = "Init logging..."}, new {Do = (Action) InitNHibernate, Message = "Init NHibernate..."}, new {Do = (Action) SetupUnityContainer, Message = "Init Unity..."}, new {Do = (Action) UserLogOn, Message = "Logon..."}, new {Do = (Action) PrefetchData, Message = "Caching..."}, }; InitLogging etc. are methods defined elsewhere, which performs some time consuming tasks. The boot sequence gets executed this way: foreach (var step in bootSequence) { _status.Update(step.Message); step.Do(); } _status denotes an instance of my XAML splash screen window containing a progress bar and a label for status information. Its Update() method is defined as follows: public void Update(string status) { int value = ++_updateSteps; Update(status, value); } private void Update(string status, int value) { var dispatcherOperation = Dispatcher.BeginInvoke( DispatcherPriority.Background, (ThreadStart) delegate { lblStatus.Content = status; progressBar.Value = value; }); dispatcherOperation.Wait(); } In the main this works, the steps get executed and the splash screen shows the progress. But I observed that the splash screen for some reasons doesn't update its content for all steps. This is the reason I called the Dispatcher async and wait for its completion. But even this didn't help. Has anyone else experienced this or some similar behaviour and has some advice how to keep the splash screen's update in sync with the execution of the boot sequence steps? I know that the users will unlikely notice this behaviour, since the splash screen is doing something and the application starts after booting is completed. But myself isn't sleeping well, because I don't know why it is not working as expected... Thx for your help, Denny

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  • How do I get my ActivityUnitTestCases to sync with the MessageQueue thread and call my Handler?

    - by Ricardo Gladwell
    I'm writing unit tests for a ListActivity in Android that uses a handler to update a ListAdapter. While my activity works in the Android emulator, running the same code in a unit test doesn't update my adapter: calls to sendEmptyMessage do not call handleMessage in my activity's Handler. How do I get my ActivityUnitTestCase to sync with the MessageQueue thread and call my Handler? The code for the Activity is somewhat like this: public class SampleActivity extends ListActivity implements SampleListener { List samples = new ArrayList(); public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.sample_list); listView.setEmptyView(findViewById(R.id.empty)); } private final Handler handler = new Handler() { @Override public void handleMessage(Message msg) { // unit test never reaches here sharesAdapter = new SampleAdapter(SampleActivity.this, samples); setListAdapter(sharesAdapter); } }; public void handleSampleUpdate(SampleEvent event) { samples.add(event.getSample()); handler.sendEmptyMessage(0); } } The code for my unit test is somewhat like this: public class SampleActivityTest extends ActivityUnitTestCase<SampleActivity> { public SampleActivityTest() { super(SampleActivity.class); } @MediumTest public void test() throws Exception { final SampleActivity activity = startActivity(new Intent(Intent.ACTION_MAIN), null, null); final ListView listView = (ListView) activity.findViewById(android.R.id.list); activity.handleSampleUpdate(new SampleEvent(this)); // unit test assert fails on this line: assertTrue(listView.getCount() == 1); } }

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  • Flash video plays well, but time and time-remaining are out of sync.

    - by sparkyfied
    Hey guys, Could be a known issue, an issue with my code or an oversight on my part. I have created a video player in flash. I have got it playing progressive and streaming over rtmp/rtmpt so that is all fine. My only issue is that when the video's are playing, the time-codes for time played and time remaining are not synced. So, if my video is 20 secs long and 5 have been played, time played will be 5secs, time remaining will be 16secs until it updates about half a second later. So even though they are both being set with the same line of code, there are not changing at the same time. The time played changes, then a split second later the time remaining changes. Anyone got any idea what this could be. Maybe a miscalculation on my part. Maybe I need to round up or down the remaining time. How can I sync the two times. I understand this is probably an tough question to answer, I have done my best to explain it. Thanks in advance.

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