fix a thread pool exception

webmagic-core/src/main/java/us/codecraft/webmagic/Spider.java

@@ -21,21 +21,26 @@ import java.util.concurrent.atomic.AtomicInteger;
 
 /**
  * Entrance of a crawler.<br>
- * A spider contains four modules: Downloader, Scheduler, PageProcessor and Pipeline.<br>
+ * A spider contains four modules: Downloader, Scheduler, PageProcessor and
+ * Pipeline.<br>
  * Every module is a field of Spider. <br>
  * The modules are defined in interface. <br>
  * You can customize a spider with various implementations of them. <br>
  * Examples: <br>
  * <br>
  * A simple crawler: <br>
- * Spider.create(new SimplePageProcessor("http://my.oschina.net/", "http://my.oschina.net/*blog/*")).run();<br>
+ * Spider.create(new SimplePageProcessor("http://my.oschina.net/",
+ * "http://my.oschina.net/*blog/*")).run();<br>
  * <br>
  * Store results to files by FilePipeline: <br>
- * Spider.create(new SimplePageProcessor("http://my.oschina.net/", "http://my.oschina.net/*blog/*"))                   <br>
+ * Spider.create(new SimplePageProcessor("http://my.oschina.net/",
+ * "http://my.oschina.net/*blog/*")) <br>
  * .pipeline(new FilePipeline("/data/temp/webmagic/")).run(); <br>
  * <br>
- * Use FileCacheQueueScheduler to store urls and cursor in files, so that a Spider can resume the status when shutdown.                 <br>
+ * Use FileCacheQueueScheduler to store urls and cursor in files, so that a
- * Spider.create(new SimplePageProcessor("http://my.oschina.net/", "http://my.oschina.net/*blog/*"))                                   <br>
+ * Spider can resume the status when shutdown. <br>
+ * Spider.create(new SimplePageProcessor("http://my.oschina.net/",
+ * "http://my.oschina.net/*blog/*")) <br>
  * .scheduler(new FileCacheQueueScheduler("/data/temp/webmagic/cache/")).run(); <br>
  * 
  * @author code4crafter@gmail.com <br>
@@ -221,8 +226,7 @@ public class Spider implements Runnable, Task {
 
 	@Override
 	public void run() {
-        if (!stat.compareAndSet(STAT_INIT, STAT_RUNNING)
+		if (!stat.compareAndSet(STAT_INIT, STAT_RUNNING) && !stat.compareAndSet(STAT_STOPPED, STAT_RUNNING)) {
-                && !stat.compareAndSet(STAT_STOPPED, STAT_RUNNING)) {
 			throw new IllegalStateException("Spider is already running!");
 		}
 		checkComponent();
@@ -233,7 +237,8 @@ public class Spider implements Runnable, Task {
 			startUrls.clear();
 		}
 		Request request = scheduler.poll(this);
-        //single thread
+        logger.info("Spider " + getUUID() + " started!");
+		// single thread
 		if (threadNum <= 1) {
 			while (request != null && stat.compareAndSet(STAT_RUNNING, STAT_RUNNING)) {
 				processRequest(request);
@@ -243,11 +248,12 @@ public class Spider implements Runnable, Task {
 			synchronized (this) {
 				this.executorService = ThreadUtils.newFixedThreadPool(threadNum);
 			}
-            //multi thread
+			// multi thread
 			final AtomicInteger threadAlive = new AtomicInteger(0);
 			while (true && stat.compareAndSet(STAT_RUNNING, STAT_RUNNING)) {
 				if (request == null) {
-                    //when no request found but some thread is alive, sleep a while.
+					// when no request found but some thread is alive, sleep a
+					// while.
 					try {
 						Thread.sleep(100);
 					} catch (InterruptedException e) {
@@ -274,7 +280,7 @@ public class Spider implements Runnable, Task {
 			executorService.shutdown();
 		}
 		stat.compareAndSet(STAT_RUNNING, STAT_STOPPED);
-        //release some resources
+		// release some resources
 		destroy();
 	}
 
@@ -299,7 +305,8 @@ public class Spider implements Runnable, Task {
 	/**
 	 * Process specific urls without url discovering.
 	 * 
-     * @param urls urls to process
+	 * @param urls
+	 *            urls to process
 	 */
 	public void test(String... urls) {
 		checkComponent();
@@ -316,7 +323,7 @@ public class Spider implements Runnable, Task {
 			sleep(site.getSleepTime());
 			return;
 		}
-        //for cycle retry
+		// for cycle retry
 		if (page.getHtml() == null) {
 			addRequest(page);
 			sleep(site.getSleepTime());
@@ -365,9 +372,15 @@ public class Spider implements Runnable, Task {
 	}
 
 	public void stop() {
-        stat.compareAndSet(STAT_RUNNING, STAT_STOPPED);
+		if (stat.compareAndSet(STAT_RUNNING, STAT_STOPPED)) {
+			if (executorService != null) {
 				executorService.shutdown();
 			}
+			logger.info("Spider " + getUUID() + " stop success!");
+		} else {
+			logger.info("Spider " + getUUID() + " stop fail!");
+		}
+	}
 
 	public void stopAndDestroy() {
 		stop();

webmagic-core/src/main/java/us/codecraft/webmagic/utils/ThreadUtils.java

@@ -1,7 +1,7 @@
 package us.codecraft.webmagic.utils;
 
 import java.util.concurrent.ExecutorService;
-import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.SynchronousQueue;
 import java.util.concurrent.ThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
 
@@ -12,21 +12,10 @@ import java.util.concurrent.TimeUnit;
 public class ThreadUtils {
 
 	public static ExecutorService newFixedThreadPool(int threadSize) {
-        return new ThreadPoolExecutor(threadSize, threadSize, 0L, TimeUnit.MILLISECONDS,
+		if (threadSize <= 1) {
-                new LinkedBlockingQueue<Runnable>(1) {
+			throw new IllegalArgumentException("ThreadSize must be greater than 1!");
-
-                    private static final long serialVersionUID = -9028058603126367678L;
-
-                    @Override
-                    public boolean offer(Runnable e) {
-                        try {
-                            put(e);
-                            return true;
-                        } catch (InterruptedException ie) {
-                            Thread.currentThread().interrupt();
 		}
-                        return false;
+		return new ThreadPoolExecutor(threadSize - 1, threadSize - 1, 0L, TimeUnit.MILLISECONDS,
-                    }
+				new SynchronousQueue<Runnable>(), new ThreadPoolExecutor.CallerRunsPolicy());
-                });
 	}
 }

webmagic-core/src/test/java/us/codecraft/webmagic/SpiderTest.java

@@ -18,11 +18,12 @@ public class SpiderTest {
             public void process(ResultItems resultItems, Task task) {
                 System.out.println(1);
             }
-        });
+        }).thread(2);
         spider.start();
         Thread.sleep(10000);
         spider.stop();
-//        spider.run();
+        Thread.sleep(10000);
+        spider.start();
         Thread.sleep(10000);
     }
 }