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  • Cloud sync between iPad/iPhone app

    - by Macatomy
    I have a Core Data app that will end up being an iPhone/iPad universal application. I would like to implement cloud syncing so that an iPhone and an iPad both running the app could share data. I'm planning to use the recently released Dropbox API. Does anyone have any thoughts on the best way to go about doing this? The Dropbox API allows for apps to store files on the cloud. What I was thinking was to original store the database (sqlite) for the app on the cloud and then download that database, but I then realized that using that method would make it painfully difficult to merge changes (rather than replacing the whole database). Any thoughts are appreciated. Thanks.

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  • Writing a synchronized thread-safety wrapper for NavigableMap

    - by polygenelubricants
    java.util.Collections currently provide the following utility methods for creating synchronized wrapper for various collection interfaces: synchronizedCollection(Collection<T> c) synchronizedList(List<T> list) synchronizedMap(Map<K,V> m) synchronizedSet(Set<T> s) synchronizedSortedMap(SortedMap<K,V> m) synchronizedSortedSet(SortedSet<T> s) Analogously, it also has 6 unmodifiedXXX overloads. The glaring omission here are the utility methods for NavigableMap<K,V>. It's true that it extends SortedMap, but so does SortedSet extends Set, and Set extends Collection, and Collections have dedicated utility methods for SortedSet and Set. Presumably NavigableMap is a useful abstraction, or else it wouldn't have been there in the first place, and yet there are no utility methods for it. So the questions are: Is there a specific reason why Collections doesn't provide utility methods for NavigableMap? How would you write your own synchronized wrapper for NavigableMap? Glancing at the source code for OpenJDK version of Collections.java seems to suggest that this is just a "mechanical" process Is it true that in general you can add synchronized thread-safetiness feature like this? If it's such a mechanical process, can it be automated? (Eclipse plug-in, etc) Is this code repetition necessary, or could it have been avoided by a different OOP design pattern?

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  • Storing data locally and synchronizing it with data base on linux server

    - by Miraaj
    Hi all, I have developed a mac application, which is continuously interacting with database on linux server. As data is increasing it has become costlier affair in terms of time to fetch data from server. So I am planning to store required data locally, say on mysqlite and find some mechanism through which I can synchronize it with database on linux server. Can anyone suggest me some way to accomplish it? Thanks, Miraaj

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  • Callers block until getFoo() has a value ready?

    - by Sean Owen
    I have a Java Thread which exposes a property which other threads want to access: class MyThread extends Thread { private Foo foo; ... Foo getFoo() { return foo; } ... public void run() { ... foo = makeTheFoo(); ... } } The problem is that it takes some short time from the time this runs until foo is available. Callers may call getFoo() before this and get a null. I'd rather they simply block, wait, and get the value once initialization has occurred. (foo is never changed afterwards.) It will be a matter of milliseconds until it's ready, so I'm comfortable with this approach. Now, I can make this happen with wait() and notifyAll() and there's a 95% chance I'll do it right. But I'm wondering how you all would do it; is there a primitive in java.util.concurrent that would do this, that I've missed? Or, how would you structure it? Yes, make foo volatile. Yes, synchronize on an internal lock Object and put the check in a while loop until it's not null. Am I missing anything?

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  • How can I fix this touch event / draw loop "deadlock"?

    - by Josh
    Just want to start out by saying this seems like a great site, hope you guys can help! I'm trying to use the structure laid out in LunarLander to create a simple game in which the user can drag some bitmaps around on the screen (the actual game is more complex, but that's not important). I ripped out the irrelevant parts of LanderLander, and set up my own bitmap drawing, something like BoardThread (an inner class of BoardView): run() { while(mRun) { canvas = lockSurfaceHolder... syncronized(mSurfaceHolder) { /* drawStuff using member position fields in BoardView */ } unlockSurfaceHolder } } My drawStuff simply walks through some arrays and throws bitmaps onto the canvas. All that works fine. Then I wanted to start handling touch events so that when the user presses a bitmap, it is selected, when the user unpresses a bitmap, it is deselected, and if a bitmap is selected during a touch move event, the bitmap is dragged. I did this stuff by listening for touch events in the BoardView's parent, BoardActivity, and passing them down into the BoardView. Something like In BoardView handleTouchEvent(MotionEvent e) { synchronized(mSurfaceHolder) { /* Modify shared member fields in BoardView so BoardThread can render the bitmaps */ } } This ALSO works fine. I can drag my tiles around the screen no problem. However, every once in a while, when the app first starts up and I trigger my first touch event, the handleTouchEvent stops executing at the synchronized line (as viewed in DDMS). The drawing loop is active during this time (I can tell because a timer changes onscreen), and it usually takes several seconds or more before a bunch of touch events come through the pipeline and everything is fine again. This doesn't seem like deadlock to me, since the draw loop is constantly going in and out of its syncronized block. Shouldn't this allow the event handling thread to grab a lock on mSurfaceHolder? What's going on here? Anyone have suggestions for improving how I've structured this? Some other info. This "hang" only ever occurs on first touch event after activity start. This includes on orientation change after restoreState has been called. Also, I can remove EVERYTHING within the syncronized block in the event handler, and it will still get hung up at the syncronized call. Thanks!

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  • Are C++ Reads and Writes of an int atomic

    - by theschmitzer
    I have two threads, one updating an int and one reading it. This value is a statistic where the order of the read and write is irrelevant. My question is, do I need to synchronize access to this multi-byte value anyway? Or, put another way, can part of the write be complete and get interrupted, and then the read happen. For example, think of value = ox0000FFFF increment value to 0x00010000 Is there a time where the value looks like 0x0001FFFF that I should be worried about? Certainly the larger the type, the more possible something like this is I've always synchronized these types of accesses, but was curious what the community thought.

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  • Why is JSON outputting out of order?

    - by dcp3450
    I'm am trying to get a list of weather information for 8 locations. I'm using a weather API that accepts longitude and latitude and spits back json output with the weather info for that location. I feed the coords in order 0-7 but when json processes the data it comes back in a seemingly random order. I assume it's because some process faster than others and json is outputing what it gets back as it gets it. The output is correct, only the order is wrong. var loc = null; var body = ""; var campuses = new Array(8); campuses[0] = "34.47242,-84.42489,1"; campuses[1] = "33.81488,-84.62048,2"; campuses[2] = "34.27502,-84.46976,3"; campuses[3] = "33.92987,-84.55065,4"; campuses[4] = "34.03433,-84.46723,5"; campuses[5] = "34.08362,-84.67115,6"; campuses[6] = "33.91124,-84.82634,7"; campuses[7] = "34.10409,-84.51804,8"; function getWeather(campusArray) { body += '<p class="topTitle">Campus Weather</p>'; var cSplit = new Array(); cSplit = campusArray.split(','); var loc = "http://www.worldweatheronline.com/feed/weather.ashx?q="+cSplit[0]+","+cSplit[1]+"&format=json&num_of_days=2&key=0a05fff921162948110401&callback=?"; $('#content').html('asdf'); $.getJSON(loc,function(js) { var data = js.data; var humidity = data.current_condition[0].humidity; var tempF = data.current_condition[0].temp_F; var iconDESC = data.current_condition[0].weatherDesc[0].value; var iconURL = data.current_condition[0].weatherIconUrl[0].value; var windDir = data.current_condition[0].winddir16Point; var windSpeed = data.current_condition[0].windspeedMiles; var tempMaxF = data.weather[0].tempMaxF; var tempMinF = data.weather[0].tempMinF; body += '<p class="title">'+cSplit[2]+'</p>'+ '<span class="body">'+tempF+ ' '+windSpeed+ '<img src="'+iconURL+'" /></span>'; $('#content').html(body); }); } getWeather(campuses[0]); getWeather(campuses[1]); getWeather(campuses[2]); getWeather(campuses[3]); getWeather(campuses[4]); getWeather(campuses[5]); getWeather(campuses[6]); getWeather(campuses[7]); I have also tried it as $.ajax var loc = null; var body = ""; var campuses = new Array(8); campuses[0] = "34.47242,-84.42489,1"; campuses[1] = "33.81488,-84.62048,2"; campuses[2] = "34.27502,-84.46976,3"; campuses[3] = "33.92987,-84.55065,4"; campuses[4] = "34.03433,-84.46723,5"; campuses[5] = "34.08362,-84.67115,6"; campuses[6] = "33.91124,-84.82634,7"; campuses[7] = "34.10409,-84.51804,8"; function getWeather(campusArray) { body += '<p class="topTitle">Campus Weather</p>'; var cSplit = new Array(); cSplit = campusArray.split(','); var loc = "http://www.worldweatheronline.com/feed/weather.ashx?q="+cSplit[0]+","+cSplit[1]+"&format=json&num_of_days=2&key=0a05fff921162948110401&callback=?"; $.ajax({ url: loc, async: true, dataType: "json", success: function(js) { var data = js.data; var humidity = data.current_condition[0].humidity; var tempF = data.current_condition[0].temp_F; var iconDESC = data.current_condition[0].weatherDesc[0].value; var iconURL = data.current_condition[0].weatherIconUrl[0].value; var windDir = data.current_condition[0].winddir16Point; var windSpeed = data.current_condition[0].windspeedMiles; var tempMaxF = data.weather[0].tempMaxF; var tempMinF = data.weather[0].tempMinF; body += '<p class="title">'+cSplit[2]+'</p>'+ '<span class="body">'+tempF+ ' '+windSpeed+ '<img src="'+iconURL+'" /></span>'; $('#content').html(body); } }); } getWeather(campuses[0]); getWeather(campuses[1]); getWeather(campuses[2]); getWeather(campuses[3]); getWeather(campuses[4]); getWeather(campuses[5]); getWeather(campuses[6]); getWeather(campuses[7]); EDIT: example of json output: { "data": { "current_condition": [ {"cloudcover": "100", "humidity": "93", "observation_time": "04:04 PM", "precipMM": "0.0", "pressure": "1009", "temp_C": "2", "temp_F": "36", "visibility": "8", "weatherCode": "116", "weatherDesc": [ {"value": "Mist" } ], "weatherIconUrl": [ {"value": "http:\/\/www.worldweatheronline.com\/images\/wsymbols01_png_64\/wsymbol_0006_mist.png" } ], "winddir16Point": "WNW", "winddirDegree": "290", "windspeedKmph": "7", "windspeedMiles": "4" } ], "request": [ {"query": "Lat 34.47 and Lon -84.42", "type": "LatLon" } ], "weather": [ {"date": "2011-01-06", "precipMM": "9.3", "tempMaxC": "7", "tempMaxF": "45", "tempMinC": "2", "tempMinF": "35", "weatherCode": "113", "weatherDesc": [ {"value": "Sunny" } ], "weatherIconUrl": [ {"value": "http:\/\/www.worldweatheronline.com\/images\/wsymbols01_png_64\/wsymbol_0001_sunny.png" } ], "winddir16Point": "WNW", "winddirDegree": "293", "winddirection": "WNW", "windspeedKmph": "20", "windspeedMiles": "13" }, {"date": "2011-01-07", "precipMM": "0.0", "tempMaxC": "6", "tempMaxF": "44", "tempMinC": "0", "tempMinF": "31", "weatherCode": "116", "weatherDesc": [ {"value": "Partly Cloudy" } ], "weatherIconUrl": [ {"value": "http:\/\/www.worldweatheronline.com\/images\/wsymbols01_png_64\/wsymbol_0002_sunny_intervals.png" } ], "winddir16Point": "WNW", "winddirDegree": "286", "winddirection": "WNW", "windspeedKmph": "25", "windspeedMiles": "16" } ] }}

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  • Syncing Data to Remote Services, Best Practices for Caching?

    - by viatropos
    I want to be able to publish events to Eventbrite, Eventful, and Google Calendar for my Google Apps. Each service has slightly different properties for events... I will be syncing many other things too, such as users with Google Contacts and MailChimp, Documents with Google Docs and some other services, etc... So I'm wondering, what is the recommended way of retrieving the data for the end user so that it's reasonably maintainable and optimized? Here are the things I'm thinking that I'm having trouble with: My App keeps a central database of all the models (Event, Document, User, Form, etc.), and whenever Admin creates an object (e.g. create through Eventbrite or through our Admin panel), we sync them and store a copy in our local database. When User goes to the site /events, App retrieves the events from the database. Read Events from a target feed, such as the Eventbrite or Eventful feed, and scrap the local database. Basically, I'm wondering, if we're storing all of the data on a remote service, do we really need to have a local database copy of the data? When would we need to have a local database, when wouldn't we?

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  • Is there a better way to throttle a high throughput job?

    - by ChaosPandion
    I created a simple class that shows what I am trying to do without any noise. Feel free to bash away at my code. That's why I posted it here. public class Throttled : IDisposable { private readonly Action work; private readonly Func<bool> stop; private readonly ManualResetEvent continueProcessing; private readonly Timer throttleTimer; private readonly int throttlePeriod; private readonly int throttleLimit; private int totalProcessed; public Throttled(Action work, Func<bool> stop, int throttlePeriod, int throttleLimit) { this.work = work; this.stop = stop; this.throttlePeriod = throttlePeriod; this.throttleLimit = throttleLimit; continueProcessing = new ManualResetEvent(true); throttleTimer = new Timer(ThrottleUpdate, null, throttlePeriod, throttlePeriod); } public void Dispose() { throttleTimer.Dispose(); ((IDisposable)continueProcessing).Dispose(); } public void Execute() { while (!stop()) { if (Interlocked.Increment(ref totalProcessed) > throttleLimit) { lock (continueProcessing) { continueProcessing.Reset(); } if (!continueProcessing.WaitOne(throttlePeriod)) { throw new TimeoutException(); } } work(); } } private void ThrottleUpdate(object state) { Interlocked.Exchange(ref totalProcessed, 0); lock (continueProcessing) { continueProcessing.Set(); } } }

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  • .NET platform independant sync framework

    - by Quandary
    Question: I need to synchronize a few ActionScript files from my computer to a network share (backup). I saw a quick fix would be using Microsoft Sync Framework for this, and write a windows service. My problem is I also use Linux, and before I start with MS vendor lockin, is there any sync framework/library/whatever I could use that works accross platform? Or does the MS sync framework work on Linux, too? It is my understanding that it is a wrapper around some com objects, thus it wouldn't work. All I need is synchronizing files. So never mind the database part, although it would be nice to have it, too.

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  • Do the 'up to date' guarantees provided by final field in Java's memory model extend to indirect ref

    - by mattbh
    The Java language spec defines semantics of final fields in section 17.5: The usage model for final fields is a simple one. Set the final fields for an object in that object's constructor. Do not write a reference to the object being constructed in a place where another thread can see it before the object's constructor is finished. If this is followed, then when the object is seen by another thread, that thread will always see the correctly constructed version of that object's final fields. It will also see versions of any object or array referenced by those final fields that are at least as up-to-date as the final fields are. My question is - does the 'up-to-date' guarantee extend to the contents of nested arrays, and nested objects? An example scenario: Thread A constructs a HashMap of ArrayLists, then assigns the HashMap to final field 'myFinal' in an instance of class 'MyClass' Thread B sees a (non-synchronized) reference to the MyClass instance and reads 'myFinal', and accesses and reads the contents of one of the ArrayLists In this scenario, are the members of the ArrayList as seen by Thread B guaranteed to be at least as up to date as they were when MyClass's constructor completed?

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  • Develop a custom file sync provider over file transfer WCF service

    - by user336622
    Hi All I'm trying to develop a custom sync provider to sync files over the internet using WCF service. We already have a file transfer service and it's working in production but I need to implement a custom sync provider on top of it. I've checked the solution in Braynt Likes blog here but this doesn't fulfill my needs. Any advices, guidance, or sample code to help is really appreciated?

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  • Open source framework à la Microsoft Sync Framework suggestions?

    - by drskol
    We are implementing a warehouse management system atop an open source stack (Java, web services & friends). In this system, we want to integrate many mobile devices which should also be capable of adequate online/offline functionality, e.g. preparing database inserts while a mobile device is temporarily unconnected, and performing them on the backend database when reconnected. For a .NET stack, Microsoft Sync Framework would be a perfect solution, e.g. to do database replication and hoarding. Can anyone suggest an open source alternative to the MS Sync Framework and possibly describe his experiences with it? Thanks in advance for any answers.

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  • Will this make the object thread-safe?

    - by sharptooth
    I have a native Visual C++ COM object and I need to make it completely thread-safe to be able to legally mark it as "free-threaded" in th system registry. Specifically I need to make sure that no more than one thread ever accesses any member variable of the object simultaneously. The catch is I'm almost sure that no sane consumer of my COM object will ever try to simultaneously use the object from more than one thread. So I want the solution as simple as possible as long as it meets the requirement above. Here's what I came up with. I add a mutex or critical section as a member variable of the object. Every COM-exposed method will acquire the mutex/section at the beginning and release before returning control. I understand that this solution doesn't provide fine-grained access and this might slow execution down, but since I suppose simultaneous access will not really occur I don't care of this. Will this solution suffice? Is there a simpler solution?

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  • Booking logic and architecture, database sync: Hotels, tennis courts reservation system ...

    - by coulix
    Hello Stackers, Imagine that you want to design a tennis booking system. You have 5 tennis clubs as partenrs with no online api allowing you to check on their side if a court is booked or not: You have to build this part as well. Every time a booking is done on their side you want it to be know by our system. Probably using a POST request form tennis partner to our server. Every time a booking is done on our website, we want to push the booking to their system. The difficulty is that their system need to be online and accessible from outside. Ip may change, we have to use a dns updater. In case their system is not available we still accept the booking and fallback to an async email with 'i confirm booking/reject booking' link sent to the club. I find the whole process quite complex and was wondering about the way online hotel booking system and hotel were working. Do they all have their data open and online ? The good thing is that the data will grow large and fits nicely to some no SQL ;) like couch db

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  • Questions about HTML5 audio

    - by Nimbuz
    <audio src="http://upload.wikimedia.org/wikipedia/commons/8/82/Riddle_song.ogg"></audio> <ul id="lyrics"> <li>line 1</li> <li>line 2</li> <li>line 3</li> <li>and so on...</li> </ul><!-- end #lyrics --> So I want to: Highlight (change color or background) of the line that is being played. Save current time to a cookie and resume on next visit. I'm not sure if either of these are possible in HTML5, but even in Flash or other technology, I'd like to know if and how it is possible. I understand #2 is asking too much, but #1 is really important. So almost similar to this: http://randallagordon.com/jaraoke/ but all the lines are visible, just the current line is highlighted. Many thanks for your help.

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  • What time function do I need to use with pthread_cond_timedwait?

    - by Vincent
    The pthread_cond_timedwait function needs an absolute time in a time timespec structure. What time function I'm suppose to use to obtain the absolute time. I saw a lot of example on the web and I found almost all time function used. (ftime, clock, gettimeofday, clock_gettime (with all possible CLOCK_...). The pthread_cond_timedwait uses an absolute time. Will this waiting time affected by changing the time of the machine? Also if I get the absolute time with one of the time function, if the time of the machine change between the get and the addition of the delta time this will affect the affect the wait time? Is there a possibility to wait for an event with a relative time instead?

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  • Sync data between a windows desktop app and windows mobile client app

    - by Chris W
    I need to knock up a very quick prototype/proof of concept application to demo to someone within the next couple of days so I've minimal time to research this as fully as I normally would. The set-up is a very simple database application running on a laptop - will only ever be a single user updating a couple of tables so I was thinking of knocking up a basic Win Forms app against SQL Compact. Visual Studio's auto generated data grid edit screens will be fine with a little customisation. The second aspect is to then add a windows mobile client application that can pull data from both tables stored on the laptop, edit some data and insert some extra rows before sending the changes back to the laptop copy of the database. I've not done any WinMo development so what's the best approach for me to look at. Is it easy enough to sync data between the two databases when the WinMo device is connected to the laptop with USB? Most of the samples I've looked at so far seem to be syncing SQL Compact with SQL Standard using IIS which seems a bit overkill. The volumes of data to be synced are so small that I can easily write some manual sync code if it's easy for me to query/update the Compact DB from the laptop application when the device is connected.

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  • Why timed lock doesnt throws a timeout exception in C++0x?

    - by Vicente Botet Escriba
    C++0x allows to lock on a mutex until a given time is reached, and return a boolean stating if the mutex has been locked or not. template <class Clock, class Duration> bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time); In some contexts, I consider an exceptional situation that the locking fails because of timeout. In this case an exception should be more appropriated. To make the difference a function lock_until could be used to get a timeout exception when the time is reached before locking. template <class Clock, class Duration> void lock_until(const chrono::time_point<Clock, Duration>& abs_time); Do you think that lock_until should be more adequate in some contexts? if yes, on which ones? If no, why try_lock_until will always be a better choice?

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  • Emacs: Often switching between Emacs and my IDE's editor, how can I 'synch' the file?

    - by WizardOfOdds
    I very often need to do some Emacs magic on some files and I need to go back and forth my IDE (IntelliJ IDEA) and Emacs. When a change is made under Emacs (and after I've saved the file) and I go back to IntelliJ the change appears immediately (if I recall correctly I configured IntelliJ to "always reload file when a modification is detected on disk" or something like that). I don't even need to reload: as soon as IntelliJ IDEA gains focus, it instantly reloads the file (and I hence have immediately access to the modifications I made from Emacs). So far, so very good. However "the other way round", it doesn't work yet. Can I configure Emacs so that everytime a file is changed on disk it reloads it? Or make Emacs, everytime it "gains focus", verify if any file currently opened has been modified on disk? I know I can start modifying the buffer under Emacs and it shall instantly warn that it has been modified, but I'd rather have it do it immediately (for example if I used my IDE to do some big change, when I come back to Emacs what I see may not be at all anymore what the file contains and it's a bit weird).

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  • MS Sync framework - Identity crisis resolution by partitioning the primary key.

    - by user326136
    Hello, We implementing offline feature to an existing application. We have implemented the syn with SQL Server internal change tracking and over WCF using MS Sync Framework (http://msdn.microsoft.com/en-us/sync/default.aspx) All of our tables have primary key as integer, we cannot move to GUID. So as you are thinking we will have identity crises between applications. So we decided to go with the way Merge replication does(http://msdn.microsoft.com/en-us/library/aa179416(SQL.80).aspx) partition the primary key range. Below is the example scenario - Server Table A - ID Range - 0 to 100 Client 1 Table A - ID Range - 101 to 200 Client 2 Table A - ID Range - 201 to 300 how to implement this ? i know we can use BCC CHECKIDENT (yourtable, reseed, value) CHECK (([ID]<=(100))) but this does not solve the issue.... Merge replication provides an option of "Not for replication"(http://msdn.microsoft.com/en-us/library/aa237102(SQL.80).aspx) to achieve insert form clients and still maintain the set range.. can i use that somehow here? please help...

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  • How to synchronize two (or n) replication processes for MS SQL databases?

    - by Yauheni Sivukha
    There are two master databases and two read-only copies updated by standard transactional replication. It is needed to map some entity from both read-only databases, lets say that A databases contains orders and B databases contains lines. The problem is that replication to one database can lag behind replication of second database, and at the moment of mapping R-databases will have inconsistent data. For example. We stored 2 orders with lines at 19:00 and 19:03. Mapping process started at 19:05, but to the moment of mapping A database replication processed all changes up to 19:03, but B database replication processed only changes up to 19:00. After mapping we will have order entity with order as of 19:03 and lines as of 19:00. The troubles are guaranteed:) In my particular case both databases have temporal model, so it is possible to fetch data for every time slice, but the problem is to identify time of latest replication. Question: How to synchronize replication processes for several databases to avoid situation described above?

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