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From "Maurice Codik Moscoso (JIRA)" <j...@apache.org>
Subject [jira] Commented: (FILEUPLOAD-136) FileUpload race condition with used with Jetty 6
Date Tue, 17 Jul 2007 21:12:04 GMT

    [ https://issues.apache.org/jira/browse/FILEUPLOAD-136?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12513359
] 

Maurice Codik Moscoso commented on FILEUPLOAD-136:
--------------------------------------------------

Ah, I see. That does make sense, but I would argue that its likely safer to do that "scan
to the next item" when you call FileItemIterator.next(), not when you attempt to close an
item's stream. 

Since a programmer is probably using close() inside a finally block, its possible to run into
situations like the above: an exception is thrown, you say "close", and then you actually
read some more in the background, which can cause unpredictable results. However, doing it
when trying to iterate to the next item completely avoid this issue, since a developer is
unlikely to be doing this after an exception is thrown.

Just my 2c... I do agree that its certainly much more of a problem with jetty -- code should
never be able to go into wacky busy loops.

> FileUpload race condition with used with Jetty 6
> ------------------------------------------------
>
>                 Key: FILEUPLOAD-136
>                 URL: https://issues.apache.org/jira/browse/FILEUPLOAD-136
>             Project: Commons FileUpload
>          Issue Type: Bug
>    Affects Versions: 1.2
>         Environment: Running on Windows XP SP2 with Jetty 6 embedded and Firefox 2.0.0.4
>            Reporter: Keith Kowalczykowski
>            Priority: Critical
>         Attachments: FileUploadTest.zip, TestJetty.java
>
>
> When running commons file upload with Jetty 6, ServletFileUpload.parseRequest spins and
never returns when the user clicks the "stop" button in their browser while an upload is in
progress.
> Reproduction Steps:
>  * Create a simple servlet / html form which accepts a file upload using commons file
upload (or use the example code below).
>  * Upload a sufficiently large file that you have time to click the stop button before
the upload completes.
>  * Observe that the thread is now stuck within file upload.
> Other Information:
> Using jstack, I was able to get the following trace of where it is blocking. It looks
like it is on a read() call that file upload is making.
>     at org/mortbay/jetty/HttpParser$Input.blockForContent(HttpParser.java:922)
>     at org/mortbay/jetty/HttpParser$Input.read(HttpParser.java:897)
>     at org/apache/commons/fileupload/MultipartStream$ItemInputStream.makeAvailable(MultipartStream.java:959)
>     at org/apache/commons/fileupload/MultipartStream$ItemInputStream.close(MultipartStream.java:910)
>     at org/apache/commons/fileupload/util/Streams.copy(Streams.java:119)
>     at org/apache/commons/fileupload/util/Streams.copy(Streams.java:64)
>     at org/apache/commons/fileupload/FileUploadBase.parseRequest(FileUploadBase.java:354)
>     at org/apache/commons/fileupload/servlet/ServletFileUpload.parseRequest(ServletFileUpload.java:126)
>     at test/Main$1.handle(Main.java:43)
>     at org/mortbay/jetty/handler/HandlerWrapper.handle(HandlerWrapper.java:139)
>     at org/mortbay/jetty/Server.handle(Server.java:285)
>     at org/mortbay/jetty/HttpConnection.handleRequest(HttpConnection.java:502)
>     at org/mortbay/jetty/HttpConnection$RequestHandler.content(HttpConnection.java:835)
>     at org/mortbay/jetty/HttpParser.parseNext(HttpParser.java:641)
>     at org/mortbay/jetty/HttpParser.parseAvailable(HttpParser.java:208)
>     at org/mortbay/jetty/HttpConnection.handle(HttpConnection.java:378)
>     at org/mortbay/jetty/bio/SocketConnector$Connection.run(SocketConnector.java:226)
>     at org/mortbay/thread/BoundedThreadPool$PoolThread.run(BoundedThreadPool.java:442)
>     at jrockit/vm/RNI.c2java(IIII)V(Native Method)
>     -- end of trac
> Originally I thought this was an issue with our code, however, I have since isolated
it to a simple test case. Bellow is a class file called Main which when run will instantiate
an instance of Jetty on port 8080 and an HTML document that will post a file upload to the
servlet. When the stop button is pressed, you will see that the line "Starting processing"
is printed, but neither the "Exception occured in processing" or "Processing completed" are
printed. I have a full eclipse project (jars and all) on my machine that I was planning on
uploading with this ticket, however, I don't see a way to attach a file. Therefore, I have
copied and pasted the two files bellow. Let me know if you want the full project.
> === Main.java ===
> /**
>  * 
>  */
> package test;
> import java.io.IOException;
> import java.util.List;
> import javax.servlet.ServletException;
> import javax.servlet.http.HttpServletRequest;
> import javax.servlet.http.HttpServletResponse;
> import org.apache.commons.fileupload.FileItem;
> import org.apache.commons.fileupload.disk.DiskFileItemFactory;
> import org.apache.commons.fileupload.servlet.ServletFileUpload;
> import org.mortbay.jetty.Handler;
> import org.mortbay.jetty.Server;
> import org.mortbay.jetty.handler.AbstractHandler;
> /**
>  * @author Keith Kowalczykowski
>  * 
>  */
> public class Main {
> 	public static void main(String[] args) {
> 		Handler handler = new AbstractHandler() {
> 			public void handle(String arg0, HttpServletRequest arg1,
> 					HttpServletResponse arg2, int arg3) throws IOException,
> 					ServletException 
> 			{
> 				System.out.println("Starting processing");
> 				try
> 				{
> 					 // Create a factory for disk-based file items
> 		            DiskFileItemFactory factory = new DiskFileItemFactory();
> 		            
> 		            // Create a new file upload handler
> 		            ServletFileUpload upload = new ServletFileUpload(factory);
> 	
> 		            // Parse the request
> 		            List items = upload.parseRequest(arg1);
> 		            for (int i = 0; i < items.size(); i++)
> 		            {
> 		                FileItem file_item = (FileItem) items.get(i);
> 		                
> 		                System.out.println("Field Name: " + file_item.getFieldName());
> 		            }
> 				}
> 				catch (Exception e)
> 				{
> 					e.printStackTrace();
> 					System.out.println("Exception occured in processing");
> 				}
> 				finally
> 				{
> 					System.out.println("Processing completed");
> 				}
> 			}
> 		};
> 		try
> 		{
> 			Server server = new Server(8080);
> 			server.setHandler(handler);
> 			server.start();
> 		}
> 		catch (Exception e)
> 		{
> 			
> 		}
> 	}
> }
> === HTML Document ===
> <html>
>     <head>
>     </head>
>     <body>
>         <form name="test" action="http://localhost:8080/" method="post" enctype="multipart/form-data">
>             <input type="file" name="fileupload"/>
>             <input type="submit"/>
>         </form>
>     </body>
> </html>

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