Unison 2.9.20 and OpenSSH-4.1p1-2: hangs as server.

[Andrew Schulman]

> > Brooks, I do remember seeing a lot of reports about 6 months or so
> > ago, that Unison was hanging.  My recollection is dim but I think it
> > had to do with some bad combination of versions of cygwin.dll and
> > Unison.  Are you using the latest cygwin.dll on your servers?
> 
> "uname -sr" returns "CYGWIN_NT-5.2 1.5.18(0.132/4/2)", which I believe 
> means I'm running the latest version.
> 
> I also noticed that there was a new OpenSSH package out; I've upgraded 
> to OpenSSH-4.2p1-1 on the server side, and found that this changed 
> nothing with regards to this bug.

OK.

> > Invoking unison with -debug will provide a lot of output, which may or
> > may not be useful.  At least you can see what was the last thing
> > Unison was doing before it hung, and that may ring a bell somewhere.
> > Also, exceptions and broken pipes are obvious errors that may lead
> > more easily to a solution if you report the details.
> 
> True enough.  I've attached the text of unison -debug 'all' to this; I'm 
> not sure if it's meaningful or not.

No, probably not.  At least not to me... it just looks like the
typical Unison hang:  everything seems to be going along fine, and
then it just stops.

> > Uncaught exception File "/home/aschulma/usr/cygwin/unison2.9.20/unison2.9.20-2.9.20/.build/remote.ml
> > ", line 483, characters 2-8: Assertion failed
> > Broken pipe
> 
> Incidentally, this points out a definite bug in Unison-2.9.20.  This 
> exact output also occurs if I specify "-maxthreads 1" on the command 
> line, indicating that it is ignoring that option and opening the default 
> 20 threads anyway.  (If I use the "-debug 'all'" option along with 
> "-maxthreads 1", it does report "maxthreads = 1" in the list at the 
> beginning, so it's parsing the option, just ignoring it.)

I suggest that you report both of these errors to the unison-users
list: http://groups.yahoo.com/group/unison-users.  The Unison
developers are generally pretty good about fixing failed assertions,
which shouldn't ever happen.  They may ask you for more information
and/or testing and then post a patch, in which case I'll immediately
incorporate it into the Cygwin package and release a new version.
However, they may also decline to keep supporting version 2.9.20-- I
don't know.  If they do, then that suggests that it may be time to
remove 2.9.20 (and also 2.9.1) from Cygwin, too.  We'll see.

> Unfortunately, I don't have root on the remote server, so it may be a 
> little difficult to upgrade, but I see that Cygwin does seem to allow 
> having multiple versions of unison around -- many thanks to whomever was 
> responsible for that!

You're welcome :)  As for being root on your server, that's not
required.  You can build and install a private copy of Unison
(whatever version you like), then from your client just run unison
with -serverCmd /path/to/your/local/unison.

Good luck,
A.


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