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From: "Jens Viebig" <jsurf@gmx.de>
To: <commons-user@jakarta.apache.org>
Subject: [VFS] FTPClientWrapper Broken Pipe
Date: Thu, 1 Sep 2005 18:09:59 +0200
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Hello List,
i'm using VFS to regulary check some files on an FTP server. This works =
fine for a long time, but after a while the check crashes with the =
following stacktrace:

org.apache.commons.vfs.FileSystemException: Could not determine the type =
of file ftp://user:password@myserver.com/myfile.txt.
        at =
org.apache.commons.vfs.provider.AbstractFileObject.attach()V(Optimized =
Method)
        at =
org.apache.commons.vfs.provider.AbstractFileObject.exists()Z(AbstractFile=
Object.java:391)
        at my.class.Something.toDo(Unknown Source)
        at java.lang.Thread.run()V(Unknown Source)
        at =
java.lang.Thread.startThreadFromVM(Ljava.lang.Thread;)V(Unknown Source)
Caused by: java.net.SocketException: Broken pipe
        at jrockit.net.SocketNativeIO.write(IIIZ)I(Unknown Source)
        at jrockit.net.SocketNativeIO.write(III)I(Unknown Source)
        at =
jrockit.io.NativeIO.write(Ljava.io.FileDescriptor;II)I(Optimized Method)
        at java.net.AbstractSocketImpl$2.write(II)V(Optimized Method)
        at jrockit.io.NativeIOOutputStream.write([BII)V(Optimized =
Method)
        at java.io.BufferedOutputStream.flushBuffer()V(Optimized Method)
        at java.io.BufferedOutputStream.write(I)V(Optimized Method)
        at org.apache.commons.net.telnet.Telnet._sendByte(I)V(Optimized =
Method)
        at =
org.apache.commons.net.telnet.TelnetOutputStream.write(I)V(Optimized =
Method)
        at =
org.apache.commons.net.io.ToNetASCIIOutputStream.write([BII)V(Optimized =
Method)
        at =
sun.nio.cs.StreamEncoder$CharsetSE.writeBytes()V(StreamEncoder.java:325)
        at sun.nio.cs.StreamEncoder$CharsetSE.implWrite([CII)V(Optimized =
Method)
        at sun.nio.cs.StreamEncoder.write([CII)V(StreamEncoder.java:136)
        at =
java.io.OutputStreamWriter.write([CII)V(OutputStreamWriter.java:191)
        at =
java.io.BufferedWriter.flushBuffer()V(BufferedWriter.java:107)
        at java.io.BufferedWriter.flush()V(BufferedWriter.java:228)
        at =
org.apache.commons.net.ftp.FTP.sendCommand(Ljava.lang.String;Ljava.lang.S=
tring;)I(Optimized Method)
        at =
org.apache.commons.net.ftp.FTP.sendCommand(ILjava.lang.String;)I(Optimize=
d Method)
        at =
org.apache.commons.net.ftp.FTP.port(Ljava.net.InetAddress;I)I(Optimized =
Method)
        at =
org.apache.commons.vfs.provider.ftp.FTPClientWrapper.listFiles(Ljava.lang=
.String;Ljava.lang.String;)[Lorg.apache.commons.net.ftp.FTPFile;(Optimize=
d Method)
        at =
org.apache.commons.vfs.provider.ftp.FtpFileObject.doGetChildren()V(Optimi=
zed Method)
        at =
org.apache.commons.vfs.provider.ftp.FtpFileObject.getChildFile(Ljava.lang=
.String;Z)Lorg.apache.commons.net.ftp.FTPFile;(Optimized Method)
        at =
org.apache.commons.vfs.provider.ftp.FtpFileObject.getInfo(Z)V(Optimized =
Method)
        at =
org.apache.commons.vfs.provider.ftp.FtpFileObject.doAttach()V(Optimized =
Method)
        ... 6 more

When it comes to that error, the filesystem provider never recovers from =
that crash and all actions on files on the same ftp server fail. The ftp =
server works fine, i can connect fine from the commandline. it seems =
that the VFS ftp provider tries to reuse that old damaged connection, i =
don't see a new attempt to login in my ftp server log. There is no =
connection from VFS to the ftp server.

I looked in the source code of FTPClientWrapper, and tracked the error =
down to the listFiles function:

...
    public FTPFile[] listFiles(String key, String relPath) throws =
IOException
    {
        try
        {
            return getFtpClient().listFiles(key, relPath);
        }
        catch (FTPConnectionClosedException e)
        {
            disconnect();
            return getFtpClient().listFiles(key, relPath);
        }
    }
...

the FTPClient of commons.net throws FTPConnectionClosedException and =
IOException. if a FTPConnectionClosedException is thrown everything is =
fine, the old connection is closed and a new one is created. If a more =
general IOException is thrown the connection is not closed and not set =
to null, so the FTPClientWrapper tries to use it again. Normally =
isConnected() should fail then, but it seems that it still returns true =
und is a weak test. I suggest that the connection should also be =
disconnected and set to null on more general errors, if there is an =
IOException there is a big chance that the connection is not usable =
anymore.

Maybe like this:

    public FTPFile[] listFiles(String key, String relPath) throws =
IOException
    {
        try
        {
            return getFtpClient().listFiles(key, relPath);
        }
        catch (FTPConnectionClosedException e)
        {
            disconnect();
            return getFtpClient().listFiles(key, relPath);
        }
        catch (IOException ie)
        {
            disconnect();
            throw ie;
        }
    }

This fix should be applied to all functions in FTPClientWrapper

Maybe you have a better approach on fixing this issue ?
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