post_change_branch_tip hook in the server not being called

Some more information:

- The plugin does work when installed on the client side. The plugin is given below:

from bzrlib import hooks

def post_change_branch_tip(tipparams):
    print "plugin called, revno=", tipparams.new_revno
    return

hooks.install_lazy_named_hook('bzrlib.branch', 'Branch.hooks',
    'post_change_branch_tip', post_change_branch_tip, 'My post change branch tip hook')

Thank you,
Raman

Also if I do "bzr info" on the client machine inside the project directory, I get the following (from the documentation I understand that bzr+http:// should invoke the server's post_change_branch_tip)

bzr info
Lightweight checkout (format: 2a)
Location:
  light checkout root: /home/raman/work/7.0.0
   checkout of branch: bzr+http://code/repo/Platform/7.0.0/
    shared repository: bzr+http://code/repo/

Related branches:
  parent branch: bzr+http://code/repo/Platform/6.0.0/
  submit branch: bzr+http://code/repo/Platform/7.0.0/

What are you doing to try to trigger the hook?

"bzr info" won't change the branch tip, so will not trigger the post_change_branch_tip hook.

I am doing a bzr commit on the client. The commit does happen, and it does not invoke the server side post_change_branch_tip hook. But it invokes the client side hook.

Is the plugin installed on the server, too, or just on the client?

Yes, it is installed on the server.

On the server:
apache2 is running with username 'bzr'
The repository is located in /home/bzr/repo/
So, I installed the plugin in /home/bzr/.bazaar/plugins

Thank you very much Jelmer for the prompt responses. The problem was in the apache server configuration.
We compared the configuration with bazaar documentation and made the following corrections after which it worked.

1. Our directory was wrong in the apache configuration for WSGIApplicationGroup (it was pointing to scripts instead of repo). Now it is:
<Directory /home/bzr/repo>
            WSGIApplicationGroup %{GLOBAL}
 </Directory>

2. In the wsgi script for make_app, we added load_plugins=True (it seems like by default it is true, but we anyway added since you mentioned. The example in the documentation (http://doc.bazaar.canonical.com/beta/en/user-guide/http_smart_server.html) did not have that for mod_wsgi, but it had it for mod_python.)

Thank you very much again,
Raman

Thanks Jelmer Vernooij, that solved my question.