org.eclipse.linuxtools.tmf.core/src/org/eclipse/linuxtools/tmf/core/request/TmfRequestExecutor.java

   1 /*******************************************************************************
   2  * Copyright (c) 2009, 2010 Ericsson
   3  *
   4  * All rights reserved. This program and the accompanying materials are
   5  * made available under the terms of the Eclipse Public License v1.0 which
   6  * accompanies this distribution, and is available at
   7  * http://www.eclipse.org/legal/epl-v10.html
   8  *
   9  * Contributors:
  10  *   Francois Chouinard - Initial API and implementation
  11  *******************************************************************************/
  12
  13 package org.eclipse.linuxtools.tmf.core.request;
  14
  15 import java.util.Comparator;
  16 import java.util.concurrent.Executor;
  17 import java.util.concurrent.ExecutorService;
  18 import java.util.concurrent.Executors;
  19 import java.util.concurrent.PriorityBlockingQueue;
  20
  21 import org.eclipse.linuxtools.tmf.core.Tracer;
  22 import org.eclipse.linuxtools.tmf.core.component.TmfThread;
  23 import org.eclipse.linuxtools.tmf.core.request.ITmfDataRequest.ExecutionType;
  24
  25 /**
  26  * <b><u>TmfRequestExecutor</u></b>
  27  *
  28  * A simple, straightforward request executor.
  29  */
  30 public class TmfRequestExecutor implements Executor {
  31
  32         private final ExecutorService fExecutor;
  33         private final String fExecutorName;
  34         private final PriorityBlockingQueue<TmfThread> fRequestQueue = new PriorityBlockingQueue<TmfThread>(100, new Comparator<TmfThread>() {
  35                 @Override
  36                 public int compare(TmfThread o1, TmfThread o2) {
  37                         if (o1.getExecType() == o2.getExecType())
  38                                 return 0;
  39                         if (o1.getExecType() == ExecutionType.BACKGROUND)
  40                                 return 1;
  41                         return -1;
  42                 }
  43         });
  44         private TmfThread fCurrentRequest;
  45
  46         // ------------------------------------------------------------------------
  47         // Constructors
  48         // ------------------------------------------------------------------------
  49
  50         public TmfRequestExecutor() {
  51                 this(Executors.newSingleThreadExecutor());
  52         }
  53
  54         public TmfRequestExecutor(ExecutorService executor) {
  55                 fExecutor = executor;
  56                 String canonicalName = fExecutor.getClass().getCanonicalName();
  57                 fExecutorName = canonicalName.substring(canonicalName.lastIndexOf('.') + 1);
  58                 if (Tracer.isComponentTraced()) Tracer.trace(fExecutor + " created"); //$NON-NLS-1$
  59         }
  60
  61         /**
  62          * @return the number of pending requests
  63          */
  64         public synchronized int getNbPendingRequests() {
  65                 return fRequestQueue.size();
  66         }
  67
  68         /**
  69          * @return the shutdown state (i.e. if it is accepting new requests)
  70          */
  71         public synchronized boolean isShutdown() {
  72                 return fExecutor.isShutdown();
  73         }
  74
  75         /**
  76          * @return the termination state
  77          */
  78         public synchronized boolean isTerminated() {
  79                 return fExecutor.isTerminated();
  80         }
  81
  82         /**
  83          * Stops the executor
  84          */
  85         public synchronized void stop() {
  86             if (fCurrentRequest != null) {
  87                 fCurrentRequest.cancel();
  88             }
  89
  90             while ((fCurrentRequest = fRequestQueue.poll()) != null) {
  91                 fCurrentRequest.cancel();
  92             }
  93
  94                 fExecutor.shutdown();
  95                 if (Tracer.isComponentTraced()) Tracer.trace(fExecutor + " terminated"); //$NON-NLS-1$
  96         }
  97
  98         // ------------------------------------------------------------------------
  99         // Operations
 100         // ------------------------------------------------------------------------
 101
 102         /* (non-Javadoc)
 103          * @see java.util.concurrent.Executor#execute(java.lang.Runnable)
 104          */
 105         @Override
 106         public synchronized void execute(final Runnable requestThread) {
 107                 fRequestQueue.offer(new TmfThread(((TmfThread) requestThread).getExecType()) {
 108                         @Override
 109                         public void run() {
 110                                 try {
 111                                         requestThread.run();
 112                                 } finally {
 113                                         scheduleNext();
 114                                 }
 115                         }
 116             @Override
 117             public void cancel() {
 118                 ((TmfThread) requestThread).cancel();
 119             }
 120                 });
 121                 if (fCurrentRequest == null) {
 122                         scheduleNext();
 123                 }
 124         }
 125
 126         /**
 127          * Executes the next pending request, if applicable.
 128          */
 129         protected synchronized void scheduleNext() {
 130                 if ((fCurrentRequest = fRequestQueue.poll()) != null) {
 131                         if (!isShutdown())
 132                                 fExecutor.execute(fCurrentRequest);
 133                 }
 134         }
 135
 136         // ------------------------------------------------------------------------
 137         // Object
 138         // ------------------------------------------------------------------------
 139
 140         @Override
 141     @SuppressWarnings("nls")
 142         public String toString() {
 143                 return "[TmfRequestExecutor(" + fExecutorName + ")]";
 144         }
 145
 146 }