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From "Agent Vinod (JIRA)" <j...@apache.org>
Subject [jira] [Created] (NET-460) _retrieveFile() blocks calling thread, on FTP I/O till the time file transfer is complete
Date Sun, 22 Apr 2012 09:49:36 GMT
Agent Vinod created NET-460:
-------------------------------

             Summary: _retrieveFile() blocks calling thread, on FTP I/O till the time file
transfer is complete
                 Key: NET-460
                 URL: https://issues.apache.org/jira/browse/NET-460
             Project: Commons Net
          Issue Type: Wish
          Components: FTP
    Affects Versions: 3.1
         Environment: linux/windows
            Reporter: Agent Vinod


The Function _retrieveFile in file: FTPClient.java , does not respond to interrupts from calling
thread.

For Example:

A Basic FTP Client Application has 1 Main (Parent) Thread and 1 Child Thread.
Main (Parent) thread handles all functions except the FtpClient download/upload.
Child Thread handles only FtpClient related functions mainly (_retrieveFile()) etc.

Steps to reproduce:

1) Main Thread has initiated child Thread .
2) Child thread is presently downloading a file using _retrieveFile(String command, String
remote, OutputStream local) . 
3) After some time, Main Thread fires Interrupt on child Thread to stop( Abort) download.

Expected behavior:

Child Thread immediately aborts download and dies.

Observed behavior:

Child Thread blocks on retrieveFile(String command, String remote, OutputStream local) till
the file finishes download. 
Only after this ,does the Child thread respond to any interrupt from Parent Thread.

My Workaround:

file:  FTPClient.java
Class: FTPClient    

Step 1: declare private Socket mySocket;

Step 2: In the function : protected boolean _retrieveFile(String command, String remote, OutputStream
local) throws IOException{}
Comment out:  Socket socket;
and instead use:  mySocket ( declared as global in step1)

Step 3:  In the function : public boolean abort() throws IOException
Add a statement: Util.closeQuietly(mySocket);
before the statement: return FTPReply.isPositiveCompletion(abor());


This way, every time the Main Thread calls abort(), the download active and blocked on mySocket
in _retrieveFile() is immediately interrupted and stopped.
raising an immediate Exception and thus stopping the Child thread (of course one needs to
catch this exception properly).

I am not sure if this is the right way of doing it and am afraid if this breaks something
else.
Requesting the core developers to look into a better solution to this workaround.

thank




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