[Zope] CoreSession + Non-undoable databases

[CJ Kucera]

On Tue Oct  9 12:43:16 2001, Chris McDonough wrote:
> Ugh!  This isn't as easy as it should be.

Excellent; thanks for your help.  It appears to be working.
Some notes:

  1) BerkeleyDB installs by default into /usr/local/BerkeleyDB.3.2
     (obviously if you're installing a different version that'll be
     slightly different).  This means that to compile bsddb3 you have
     to do the following:

        $ python setup.py build_ext --inplace --berkeley-db=/usr/local...

     What the bsdbb3 README files don't tell you is that you have to
     pass in the --berkeley-db= line to the "python setup.py install"
     command as well, or it won't be built properly.  To find out if
     it's been built properly, cd into "bsddb3/{arch}/bsddb3" [1] and:

        $ nm _db.so | grep db_create

     If you get a line like "000242e0 T db_create" you're okay.  If you
     get one like "     U db_create" there's problems because it wasn't
     linked properly.  The "_db.so" created inside the "build" directory
     during the initial "build_ext" step doesn't seem to actually have
     anything to do with anything; the one under "bsddb3" gets compiled
     at the "install" step.

  2) The bsddb3Storage READMEs are a little obtuse.  [2] When you've
     untarred the package, you'll have a "bsddb3Storage" directory with
     just .py files in it.  THAT's the directory to copy into
     {ZOPE_HOME}/lib/python/Products.

  3) Also, the "custom_zodb.sample" mentioned in the docs doesn't
     actually exist.  It's "custom_zodb.py" in the current release
     (1.0beta4), and the syntax of the file doesn't work in Python < 2
     (so if you're using Python 2, you should be okay).  The
     custom_zodb.py I ended up using is here:

> from bsddb3Storage.Packless import Packless
> #from bsddb3Storage.Minimal  import Minimal  as ConcreteStorage
> #from bsddb3Storage.Full     import Full     as ConcreteStorage
> 
> import os
> env = os.path.join('var', 'bsddb3Storage')
> 
> Storage = Packless(name='BerkeleyStorage', env=env)

     Note that the "env" line is telling the BerkeleyDB that it's
     data directory will be in "var/bsddb3Storage" (your Data.fs
     is in "var").

  4) When you've created the "sessionData" folder in BerkeleyDB,
     shut down your temporary Zope instance and I recommend tarring
     up the bsddb3Storage directory under var, to move it over to
     your "real" zope instance.  For instance:

       $ cd $TEMP_ZOPE/var; tar zcvf ../berkeleydb.tgz bsddb3Storage

  5) Here's the correct syntax for "Extensions/sessionDB":

> import ZODB
> from bsddb3Storage import Packless
> 
> def getSessionDB():
>   return ZODB.DB(Packless.Packless('session','berkeleyStorage'))

     Note that "berkeleyStorage" is the name of the directory where
     the BerkeleyDB is going to be located (was "var/bsddb3Storage"
     on your "temp" Zope instance earlier).  So, using my tarfile from
     before, here's basically what I did:

       $ cd $ZOPE_HOME; tar zxf ../temp_zope/berkeleydb.tgz
       $ mv bsddb3Storage berkeleyStorage

     So for me, I put the BerkeleyDB Storage directory in the same
     directory as var, lib, zpasswd.py, etc . . .

  6) When it's been inserted into your tree, for all intents and
     purposes it looks EXACTLY like just a regular folder, as far
     as I can tell, which threw me off.  There's even an "undo"
     tab and everything.  So be careful; there doesn't seem to be
     an indication that it's actually an Externally Mounted
     folder as opposed to a regular one.

In any case, after all that it appears to be working.  You might
want to update your HOWTO with what I've mentioned here.

Thanks very much!

-CJ

[1] Replace "{arch}" with the directory there.  On my system, it was
    "lib.linux-i686-1.5"

[2] I lie.  They're astonishingly useless.  The READMEs distributed
    with 1.0beta4 are actually the 1.0beta3 files, which may account
    or most if not all of the problems.  Under the "docs" directory
    there's a "PacklessReadme.txt" that you're much better off not
    reading.  It makes references like "Once you've untarred the
    product, you should have a subdirectory named
    'PacklessBerkeley3Storage'" which turn out to be patently false.
    So anyway . . . [3]

[3] I'm being a bit harsh; they're not really THAT bad, just overly
    confusing at times. :)

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