SSDM-351: Implement a queue for all asynchronous registartion from openbis UI

SVN: 32456

openbis/source/java/ch/systemsx/cisd/openbis/plugin/generic/server/queue/ConsumerQueue.java

+package ch.systemsx.cisd.openbis.plugin.generic.server.queue;
+
+import java.util.Deque;
+import java.util.LinkedList;
+
+import ch.systemsx.cisd.common.logging.LogCategory;
+import ch.systemsx.cisd.common.logging.LogFactory;
+
+import org.apache.log4j.Level;
+import org.apache.log4j.Logger;
+
+/*
+ * This class models a simple queue with tasks and starts a thread that consumes the tasks.
+ */
+public final class ConsumerQueue
+{
+    private static final Deque<ConsumerTask> consumerQueue = new LinkedList<ConsumerTask>();
+    private static final Logger trackingLog = LogFactory.getLogger(LogCategory.TRACKING, ConsumerQueue.class);
+    
+    public static final synchronized void addTaskAsLast(ConsumerTask task) {
+        consumerQueue.addLast(task);
+    }
+    
+    private static final synchronized ConsumerTask getNextTask() {
+        return consumerQueue.pollFirst();
+    }
+    
+    // Consumer Thread
+    static {
+        Thread consumerThread = new Thread() {
+            
+            @Override
+            public void run() {
+                 while(true) {
+                     //We start with a null task for save coding
+                     ConsumerTask consumerTask = new ConsumerTask() {
+                        @Override
+                        public String getTaskName() { return "Null Task"; }
+
+                        @Override
+                        public void executeTask() {}
+                     };
+                     
+                     try {
+                         consumerTask = getNextTask();
+                         if(consumerTask != null) {
+                             consumerTask.executeTask();
+                         } else {
+                             Thread.sleep(1000 * 5);
+                         }
+                     } catch(Throwable anyError) {
+                         trackingLog.log(Level.ERROR, consumerTask.getTaskName(),  anyError);
+                     }
+                 }
+            }
+        };
+        consumerThread.start();
+    }
+}

openbis/source/java/ch/systemsx/cisd/openbis/plugin/generic/server/queue/ConsumerTask.java

+package ch.systemsx.cisd.openbis.plugin.generic.server.queue;
+
+public interface ConsumerTask
+{
+    String getTaskName();
+    void executeTask();
+}