Configure and Run ContentMirror

Install ContentMirror 

The fine details of this are beyond the scope of this document, but you can find out more here: ContentMirror.

 For my buildout-based installation, I added ContentMirror to the "productdistros" section, like this:

[productdistros]
urls +=
    http://contentmirror.googlecode.com/files/ContentMirror-0-4-1.tgz

1. Find the settings-example.zcml.  For buildout-based installations, it is located at parts/productdistros/ContentMirror/settings-example.zcml.  For non-buildout installations, look in Products/ContentMirror/settings-example.zcml.
2. Copy settings-example.zcml to settings.zcml.
   
3. Edit settings.zcml to point to the database:
   

   <!-- setup a database connection -->
   <db:engine url="postgres://localhost/mydatabase"
              name="mirror-db"
              echo="True"/>

   Be sure that you specify the correct username and password in this file, too. See the "Configuration" section here: http://code.google.com/p/contentmirror/wiki/Installation
4. Create SQL statements for tables

   ddl.py postgres > somestuff.sql

5. Run that SQL against your database, to create ContentMirror table.
   
   psql mydatabase < somestuff.sql
6. Run bulk.py to export existing Plone content into the database.  (NOTE: bulk.py is buried in the eggs somewhere.)

Everything worked fine the first time I tried this. But the second time, I ran into a couple roadblocks. They might not be true bugs, in the sense that they might work fine on normal data. But my database is full of bad, corrupted data. So, I had to make a couple hacks to get this to work.

Hack #1 - Run as Admin User

ContentMirror is only designed to mirror content that has been Published, and is viewable by Anonymous users. I needed to mirror ALL content, regardless of its workflow state. In bulk.py, I added three lines in main():

 def main( app ):
    if not len(sys.argv) == 2:
        print "mirror-batch portal_path"
        sys.exit(1)


    #Hack: run as admin user - 06/30/2010
    from AccessControl.SecurityManagement import newSecurityManager
    admin = app.acl_users.getUserById("admin")
    newSecurityManager(None, admin)

Incidentally, ContentMirror does mirror the workflow state to the external database, so I am able to see which content is Public, Private, etc. after export.

Hack #2 - Fix ReferenceTransform for bad data

I also had to hack transform.py, so that ContentMirror would keep going, despite the bad data in my database. In class ReferenceTransform, I added four lines to the copy() method:

    def copy( self, instance, peer ):
        value = self.context.getAccessor( instance )()

        if not value:
            return

        if not isinstance( value, (list, tuple)):
            value= [ value ]

        #Hack - remove None values.
        goods = [x for x in value if x is not None]
        if len(goods) < 1:
            return
        value = goods

I even compared this to the latest source code (version 0.6.0rc2) and found that the latest source still has this vulnerability. So, in true open-source spirit, I submitted an issue to the ContentMirror team.