FULL PRODUCT VERSION :
java version "1.5.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0-b64)
Java HotSpot(TM) Client VM (build 1.5.0-b64, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Linux 2.4.22 i686

EXTRA RELEVANT SYSTEM CONFIGURATION :
Viewing applet using Mozilla 1.7

A DESCRIPTION OF THE PROBLEM :
When a caching download (ie getting a file using caches that is not already in the cache) is in progress, all other cached downloads block until this download is complete (even if the file they require _is_ in the cache)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Clear java cache
Download a small .au file (using URLConnection.getInputStream())
Start a thread downloading a large .au file
Try downloading the small .au file again - it will block until the large download is complete

Example applet that does this (apart from clearing the cache, which must be done manually) is at http://wwwb.forbidden.co.uk/~nae/cache_blocking/
Source code for this applet is below

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
I would expect the small file to download (from the cache) immediately.
ACTUAL -
The small file's getInputStream() blocks until the large file has finished downloading

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.awt.*;
import java.io.*;
import java.net.*;

public final class downloader extends java.applet.Applet implements Runnable
{
   volatile boolean killed = false;
   boolean finished = false;
   TextArea display = new TextArea();

   static final String BigFile = "big";
   static final String SmallFile = "small";

   String suffix = ".au";

   public final String getAppletInfo()
   { return "File downloader demo";
   }

   public final void init()
   {
      System.out.println("Applet loaded");
      setLayout(new GridLayout(1,1));
      add(display);
      if (getParameter("suffix") != null)
         suffix = getParameter("suffix");
   }

   public final void start() {
      (new Thread(this)).start();
   }


   public void downloadFile(String fname)
   {
      try
      {
         display.append("Opening connection to file '"+fname+"'\n");
         URL url = new URL(getCodeBase(),fname,null);
         long startTime = System.currentTimeMillis();
         URLConnection c = url.openConnection();
         c.setUseCaches(true);
         long connectTime = System.currentTimeMillis();
         InputStream stream = c.getInputStream();
         long streamTime = System.currentTimeMillis();
         int bytesDownloaded = 0;
         byte buffer[] = new byte[1024];
         display.append("Got input stream to file '"+fname+"', downloading bytes\n");
         while (!killed)
         {
            int length = stream.read(buffer, 0, 1024);
            if (length == -1)
               break;
            bytesDownloaded += length;
         }
         long downloadTime = System.currentTimeMillis();
         stream.close();
         if (!killed)
         {
            int dr1 = streamTime==connectTime?-1:(int)((long)bytesDownloaded*8/(streamTime - connectTime)); // d/r if download happened at connect
            int dr2 = downloadTime==streamTime?-1:(int)((long)bytesDownloaded*8/(downloadTime-streamTime)); // d/r if download happened at get
            synchronized(display) {
               display.append("Downloaded "+bytesDownloaded+" bytes from "+fname+"\n");
               display.append("Times: getInputStream() : "+(streamTime - connectTime)+"ms ("+dr1+"kb/s)\n");
               display.append(" download : "+(downloadTime - streamTime)+"ms ("+dr2+"kb/s)\n");
            }
         }
      }
      catch (Exception e) {
         display.append("Threw exception '"+e.toString()+"'\n");
      }
   }

   public final void run()
   {
      // Download small file to cache
      downloadFile(SmallFile+suffix);
      // Start downloading big file
      new Thread(new Runnable()
                 {
                  public final void run() {
                     downloadFile(BigFile+suffix);
                  }
                 },"big download").start();
      try {
         Thread.sleep(100);
      }
      catch (InterruptedException e)
      {
      }
      // Would expect small file to arrive immediately from cache
      downloadFile(SmallFile+suffix);
   }


   public final void stop() {
      killed = true;
   }

   public final void destroy() {
   }
}

---------- END SOURCE ----------
 2005-04-11 23:00:59 GMT