org.eclipse.linuxtools.tmf.core/src/org/eclipse/linuxtools/internal/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.internal.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.internal.tmf.core.Tracer;
  22 import org.eclipse.linuxtools.internal.tmf.core.component.TmfThread;
  23 import org.eclipse.linuxtools.tmf.core.request.ITmfDataRequest.ExecutionType;
  24
  25 /**
  26  * A simple, straightforward request executor.
  27  *
  28  * @version 1.0
  29  * @author Francois Chouinard
  30  */
  31 public class TmfRequestExecutor implements Executor {
  32
  33         private final ExecutorService fExecutor;
  34         private final String fExecutorName;
  35         private final PriorityBlockingQueue<TmfThread> fRequestQueue = new PriorityBlockingQueue<TmfThread>(100, new Comparator<TmfThread>() {
  36                 @Override
  37                 public int compare(TmfThread o1, TmfThread o2) {
  38                         if (o1.getExecType() == o2.getExecType())
  39                                 return 0;
  40                         if (o1.getExecType() == ExecutionType.BACKGROUND)
  41                                 return 1;
  42                         return -1;
  43                 }
  44         });
  45         private TmfThread fCurrentRequest;
  46
  47         // ------------------------------------------------------------------------
  48         // Constructors
  49         // ------------------------------------------------------------------------
  50
  51         public TmfRequestExecutor() {
  52                 this(Executors.newSingleThreadExecutor());
  53         }
  54
  55         public TmfRequestExecutor(ExecutorService executor) {
  56                 fExecutor = executor;
  57                 String canonicalName = fExecutor.getClass().getCanonicalName();
  58                 fExecutorName = canonicalName.substring(canonicalName.lastIndexOf('.') + 1);
  59                 if (Tracer.isComponentTraced()) Tracer.trace(fExecutor + " created"); //$NON-NLS-1$
  60         }
  61
  62         /**
  63          * @return the number of pending requests
  64          */
  65         public synchronized int getNbPendingRequests() {
  66                 return fRequestQueue.size();
  67         }
  68
  69         /**
  70          * @return the shutdown state (i.e. if it is accepting new requests)
  71          */
  72         public synchronized boolean isShutdown() {
  73                 return fExecutor.isShutdown();
  74         }
  75
  76         /**
  77          * @return the termination state
  78          */
  79         public synchronized boolean isTerminated() {
  80                 return fExecutor.isTerminated();
  81         }
  82
  83         /**
  84          * Stops the executor
  85          */
  86         public synchronized void stop() {
  87             if (fCurrentRequest != null) {
  88                 fCurrentRequest.cancel();
  89             }
  90
  91             while ((fCurrentRequest = fRequestQueue.poll()) != null) {
  92                 fCurrentRequest.cancel();
  93             }
  94
  95                 fExecutor.shutdown();
  96                 if (Tracer.isComponentTraced()) Tracer.trace(fExecutor + " terminated"); //$NON-NLS-1$
  97         }
  98
  99         // ------------------------------------------------------------------------
 100         // Operations
 101         // ------------------------------------------------------------------------
 102
 103         /* (non-Javadoc)
 104          * @see java.util.concurrent.Executor#execute(java.lang.Runnable)
 105          */
 106         @Override
 107         public synchronized void execute(final Runnable requestThread) {
 108                 fRequestQueue.offer(new TmfThread(((TmfThread) requestThread).getExecType()) {
 109                         @Override
 110                         public void run() {
 111                                 try {
 112                                         requestThread.run();
 113                                 } finally {
 114                                         scheduleNext();
 115                                 }
 116                         }
 117             @Override
 118             public void cancel() {
 119                 ((TmfThread) requestThread).cancel();
 120             }
 121                 });
 122                 if (fCurrentRequest == null) {
 123                         scheduleNext();
 124                 }
 125         }
 126
 127         /**
 128          * Executes the next pending request, if applicable.
 129          */
 130         protected synchronized void scheduleNext() {
 131                 if ((fCurrentRequest = fRequestQueue.poll()) != null) {
 132                         if (!isShutdown())
 133                                 fExecutor.execute(fCurrentRequest);
 134                 }
 135         }
 136
 137         // ------------------------------------------------------------------------
 138         // Object
 139         // ------------------------------------------------------------------------
 140
 141         @Override
 142     @SuppressWarnings("nls")
 143         public String toString() {
 144                 return "[TmfRequestExecutor(" + fExecutorName + ")]";
 145         }
 146
 147 }