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

[Brooks Moses]

Andrew Schulman wrote:
> 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.

> 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.

Here's what the broken pipe error looks like, meanwhile (note that I've 
snipped portions of this, noted with [... snip ...] blocks:

[Quoting from my terminal window]
> brooks-laptop:~/temp> unison references-home
> Contacting server...
> brooks@192.168.0.1's password:
> Looking for changes
>   Administrative_Stuff
> 
> [... snip a bunch ...]
> 
>   whitepapers/ME271_Combustion
>   Waiting for changes from server
> Reconciling changes
> 
> local          mindolluin
> new file <-?-> new file   journal_papers/ARFM2005_Dimotakis_Turbulent_Mixing.pdf  [] /
> new file <-?-> new file   journal_papers/ARFM2005_Dimotakis_Turbulent_Mixing.pdf
> new file ---->            journal_papers/ACM2005_Song_Stable_Non-Dissipative_Water.pdf  [f]
> 
> [... snip a bunch ...]
> 
> new file ---->            whitepapers/LKT-01-00_Meier_Towards_DNS_of_Multiphase.ps.gz  [f]
> 
> Proceed with propagating updates? []
> No default command [type '?' for help]
> Proceed with propagating updates? [] y
> Propagating updates
> 
> 
> UNISON started propagating changes at 11:30:37 on 15 Sep 2005
> [CONFLICT] Skipping journal_papers/ARFM2005_Dimotakis_Turbulent_Mixing.pdf
> [BGN] Copying journal_papers/ACM2005_Song_Stable_Non-Dissipative_Water.pdf
>   from /disk2/brooks/reference-pdfs
>   to //mindolluin//disk2/brooks/reference-pdfs
> 
> [... snip 19 more [BGN] blocks ...]
> 
> 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.)

[Now back to quoting Andrew Schulman]
> On balance though, I recommend that you upgrade to a recent (or at
> least more recent) version of Unison if you can.  2.9.20 is getting
> pretty old now.  It's still provided in Cygwin in order to allow
> maximum version compatibility with other hosts, but there are a ton of
> bug fixes and many new features in later versions.
> 
> Several more recent versions of Unison are available in Cygwin.  On
> FreeBSD I don't know, but even if you have to fetch and build a more
> recent version yourself, this is usually easy as long as you have
> OCaml installed.  Of course all of your hosts have to be running the
> same version of Unison, since different versions won't talk to each
> other; or with versions 2.13.x and later, only the first two version
> numbers (e.g. 2.13) have to match.

I'll give that a try next; I just wanted to get these errors confirmed 
and documented first.

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!

Thanks again,
- Brooks



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