RE: [JSch-users] Infinite loop/hang on connect

[Ned M. <Edw...@va...>]

I had a similar problem with the sftp connection that would occur very
occassionally.  The workaround I implemented was certainly not an eloquent
one but it has worked.  Basically, I created a very simple class that would
start a timer when the connection call was made.  If the call had not
returned within some liberal amount of time (say 1 minute) I interupted the
thread and retried the operation.   Like I said, not real pretty but it has
done the trick.

-----Original Message-----
From: Adam Fanello
To: jsc...@li...
Sent: 2/27/2006 10:00 PM
Subject: [JSch-users] Infinite loop/hang on connect

Hello fellow jsch-users (and author).

I've been using jsch for some time, now at version 0.1.24, and am now
having an occasional hang problem. This software is running on remote
servers... I can't have it hanging! Here's the thread's stack trace
where it gets stuck:

"CommAgent" prio=1 tid=0x4de2b3f8 nid=0x8fa waiting on condition
[0xbddff000..0xbddff65c]
        at java.lang.Thread.sleep(Native Method)
        at com.jcraft.jsch.Session.write(Unknown Source)
        at com.jcraft.jsch.Session.connect(Unknown Source)
        at
com.intelio.common.io.SSHConnection.connect(SSHConnection.java:84)
        at
com.intelio.common.comm.PayloadTransmitter.sendPackages(PayloadTransmitt
er.java:253)
        at
com.intelio.common.comm.PayloadTransmitter.run(PayloadTransmitter.java:1
13)
        at
com.intelio.edge.agent.comm.CommAgent.execute(CommAgent.java:164)
        at com.intelio.edge.component.Component.run(Component.java:92)

Apparently the variable "in_kex" never becomes true. I'm not sure about
the interaction here, but apparently its waiting for another thread to
change the value. Without a synchronization or declaring the variable as
volatile, could it be that the value is in fact changing and it just
isn't noticing? It seems to me that the CPU cache would flush
eventually, while this is hanging for hours (until I receive a notice
that files are piling up because the transfer is stuck, and I kill it).

Anyway, I do think that the variable needs to be declared volatile, but
it probably would only solve a short hang, not an infinite one. Any
other ideas?

--
Adam Fanello
Sr. Engineer/Architect
Intelio Technologies, Inc



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