make sure only one sequence datasource initialization thread runs at any one time

diff --git a/src/jalview/gui/SequenceFetcher.java b/src/jalview/gui/SequenceFetcher.java
index 7b42a3d..c5a9235 100755 (executable)
--- a/src/jalview/gui/SequenceFetcher.java
+++ b/src/jalview/gui/SequenceFetcher.java
@@ -57,7 +57,8 @@ public class SequenceFetcher extends JPanel implements Runnable
   private static jalview.ws.SequenceFetcher sfetch = null;
 
   private static String dasRegistry = null;
-
+  private static boolean _initingFetcher=false;
+  private static Thread initingThread=null;
   /**
    * Blocking method that initialises and returns the shared instance of the
    * SequenceFetcher client
@@ -69,9 +70,29 @@ public class SequenceFetcher extends JPanel implements Runnable
   public static jalview.ws.SequenceFetcher getSequenceFetcherSingleton(
           final IProgressIndicator guiWindow)
   {
+    if (_initingFetcher && initingThread!=null && initingThread.isAlive())
+    {
+      if (guiWindow != null)
+      {
+        guiWindow.setProgressBar("Waiting for Sequence Database Fetchers to initialise",
+                Thread.currentThread().hashCode());
+      }
+      // initting happening on another thread - so wait around to see if it finishes.
+      while (_initingFetcher && initingThread!=null && initingThread.isAlive())
+      {
+        try {Thread.sleep(10);} catch (Exception e){};
+      }
+      if (guiWindow != null)
+      {
+        guiWindow.setProgressBar("Waiting for Sequence Database Fetchers to initialise",
+                Thread.currentThread().hashCode());
+      }
+    }
     if (sfetch == null
             || dasRegistry != DasSourceBrowser.getDasRegistryURL())
     {
+      _initingFetcher=true;
+      initingThread=Thread.currentThread();
       /**
        * give a visual indication that sequence fetcher construction is occuring
        */
@@ -85,10 +106,11 @@ public class SequenceFetcher extends JPanel implements Runnable
       if (guiWindow != null)
       {
         guiWindow.setProgressBar("Initialising Sequence Database Fetchers",
-                Thread.currentThread().hashCode());
+                initingThread.hashCode());
       }
       sfetch = sf;
-
+      _initingFetcher=false;
+      initingThread=null;
     }
     return sfetch;
   }