synchronization

问题 I need to set up real time sync process between a on premise postgresql instance with cloud postgresql instance. Please let me know what are all the options available through which i can achieve it. Do i have to use any specific tool or it can be managed through replication . Please advice 回答1: Use PgPool http://www.pgpool.net/mediawiki/index.php/Main_Page from their web page: pgpool-II can manage multiple PostgreSQL servers. Using the replication function enables creating a realtime backup

问题 I'm writing some JavaScript that interacts with a browser plugin (add-on in FF, ActiveX in IE). Some of the calls are asynchronous and trigger an event when complete. There are certain cases where I need to chain calls together, but need to wait for the first call to complete before initiating the second call. For instance: A call to attach a device needs to first check if a device is already attached, and disconnect it. So the calls would be: pluginObject.disconnectDevice(deviceKey);

问题 Can I ask a rookie Java question? I am downloading some files from the web. This method download(url location) is called multiple times. public static void download(final String url) { Thread t = new Thread("download") { @Override public void run() { try { synchronized (object) { // download & save } } catch(Exception e) {} } }; t.start(); } I added "synchronized" so that downloads happens one-by-one. (not multiple downloads occur at the same time). I am guessing even though download() is

问题 I've been developing an Android application using version 2.3.3 (API 10). The application simply uses Flickr Java API (flickrj) to make certain search queries based on tags, date, geographical info etc. and displays the search result photos to the user. I have been working on it for 2 weeks and using my HTC Sensation to debug it via the USB debugger. Today, I somehow started to get an annoying warning message that loops over and over in my LogCat. It is as follows: 11-30 00:31:43.083: I/org

问题 This is a composed concurrent list multimap implementation. A lower-level implementation would be better, but more complex. Ignoring the O(n) removal in the sublist, is this the correct way to compose a ConcurrentMap and CopyOnWriteArrayList into a functional ConcurrentMultimap? Are there any unresolved data races? private final ConcurrentMap<K, Collection<V>> map = ...; // inconsequential public boolean put(K key, V value) { Collection<V> list = map.get(key); if(list != null) { list.add

问题 I have a non-GUI thread that starts a JFrame using java.awt.EventQueue.invokeLater(new Runnable() { public void run() { cardReadPunchGUI = new IBM1622GUI(); // instantiate cardReadPunchGUI.setVisible(true); } }); Part of IBM1622GUI's constructor instantiates a "model" for itself, which my non-GUI thread needs access to: cardReadPunch = IBM1622GUI.getModel(); What is the correct way for my non-GUI thread to synchronize with the new GUI that's been "invoked later"? (Without synchronization, of

问题 I have two activities. In activity 1 I write a value to a SQLite database by entering that value into an EditText field. Once I press the submit button, the data is written and I am moved along to another activity - activity 2. Activity2 also does the same thing in that I can write new data and persist it to the database with a button click. So, my question is: do I need to synchronize the method (which is on a separate thread from the UI) in activity 1, as well as the method in activity 2 in

问题 I need some help here. I am trying to create an example that shows volatile is needed to protect against instruction re-ordering. In this example I am trying to show that b > a only if reordering happens and that volatile will prevent it. The problem is that in every run I get b>a, and I must be missing something idiotic, but I can't see it. What am I missing here? public class Example04Reorder extends Thread { volatile static int a = 0; volatile static int b = 0; public static void main

问题 Let's say I have a UI thread and a background thread that subscribe to a custom thread-safe ObservableCollection that I created so that whenever the collection changes it executes the callback within the appropriate context. Now let's say I add something to the collection (from either thread, doesn't matter which one) and it now has to marshall the callback to both threads. To execute the callback within the UI's context I can simply do a Dispatcher.Invoke(...) and it executes the callback

问题 I have a situation I'm trying to cope with involving my company's SVN server. We keep all of our important code in a locked-down server (we'll call this the "dev" server). There are some files that need to be edited by users outside the corporate network, so we have another SVN server (the "global" server) which is accessible outside the firewall and contains copies of those directories containing the files needed externally. If it matters, the folder structure of the global server is a