[Monotone-devel] Re: ViewMTN multi-db

[Roland McGrath]

Thanks, Grahame!  Now that I know nagging works, I'll have to figure out
whom to badger thrice a week to have someone fix the db locking, integrate
multi-db netsync (usher/whatnot) with a sensible mtn: url schema, and
whatever else I've forgotten I can't possibly live without! ;-)

I had been imagining the option of:

        dbfiles = lambda prefix: ...

for dynamically looking up a prefix in some other table, filesystem, etc.
But that approach does not mesh so well with the nice db selector page,
a feature I was not expecting to have.  Nice!

What happens if I don't set a defaultdb?  What I'd really like is for the
top-level url to just get to the 'Change DB' page (with slightly different
titling and text for no db currently selected).  Really swift would be a
configurable inserted chunk of html for that page, so that could just be
the top-level page of a hosting site with some random local content above
the db selection list.

Can the description strings contain random html?

What I'm now toying with is:

        import os.path
        import glob

        def _flatten(l):
            return reduce(lambda a, b: a + b, l)

        def _dbfile_tuple(file):
            dir = os.path.dirname(file)
            name = os.path.basename(dir)
            description = None
            try:
                description = open(os.path.join(dir, 'description')).read()
            except IOError:
                pass
            return (name, file, description)

        dbfiles = _flatten(map(_dbfile_tuple, glob.glob('/srv/mtn/*/db.mtn')])

I don't really know Python, so perhaps I missed something obvious.  But
note how the flattening is necessary because you want a single tuple of
several triples, instead of a sequence of sequences of some sort.  It would
seem more in keeping with e.g. config.graphopts to make it:

        dbfiles = ({'name' : 'foo', 'description' : 'bar',
                    'dbfile' : '/srv/mtn/foo/db.mtn'},
                    {'name' : 'quux, 'description' : 'yowza,
                    'dbfile' : '/srv/mtn/quux/db.mtn'})

Or at least simpler all round to make it:

        dbfiles = [('foo', '/.../db.mtn', 'bar') ('quux', '/.../db.mtn', 'xx')]

But I did conquer it for a more complex case in about 10 minutes without
knowing Python, so it clearly doesn't much matter.

This was the last piece preventing me from figuring out how I wanted to do
things in Fedora packaging to make a viewmtn server setup work more or less
out of the box.  (As soon as I get that packaged setup working, I can get
it deployed on fedorahosted.org.)

Unfortunately, it's not working for me at all. :-(
The setup I did for Fedora packaging is under Apache with mod_wsgi.
http://people.redhat.com/roland/tmp/ has the setup I did for that.
If you use Fedora you can do 'yum localinstall viewmtn-*.noarch.rpm'
to get mod_wsgi and everything else you need for a test install.

This was working before with 0.09/0.08, though I sure never really
understood mod_wsgi or web.py when I got it working.

Now I always get this:

[Wed Feb 20 19:16:25 2008] [error] [client 127.0.0.1] Traceback (most recent 
call last):
[Wed Feb 20 19:16:25 2008] [error] [client 127.0.0.1]   File 
"/usr/lib/python2.5/site-packages/viewmtn/web/webapi.py", line 304, in wsgifunc
[Wed Feb 20 19:16:25 2008] [error] [client 127.0.0.1]     result = func()
[Wed Feb 20 19:16:25 2008] [error] [client 127.0.0.1]   File 
"/usr/lib/python2.5/site-packages/viewmtn/web/request.py", line 131, in <lambda>
[Wed Feb 20 19:16:25 2008] [error] [client 127.0.0.1]     func = lambda: 
handle(inp, fvars)
[Wed Feb 20 19:16:25 2008] [error] [client 127.0.0.1]   File 
"/usr/lib/python2.5/site-packages/viewmtn/web/request.py", line 22, in handle
[Wed Feb 20 19:16:25 2008] [error] [client 127.0.0.1]     for url, ofno in 
utils.group(mapping, 2):
[Wed Feb 20 19:16:25 2008] [error] [client 127.0.0.1]   File 
"/usr/lib/python2.5/site-packages/viewmtn/web/utils.py", line 325, in group
[Wed Feb 20 19:16:25 2008] [error] [client 127.0.0.1]     seq = iter(seq)
[Wed Feb 20 19:16:25 2008] [error] [client 127.0.0.1] TypeError: 'module' 
object is not iterable


The mod_wsgi glue magic in the rpm is via this .../viewmtn/__init__.py file:

        from viewmtn import *
        application = web.wsgifunc(web.webpyfunc(urls, globals()))

Maybe that idiom has changed?



Thanks,
Roland