Pulp

In pulp server/pulp/plugins/rsync/publish.py there is the following code which appears to be incorrect:

    def is_fastforward(self):
       ...
       if self.last_deleted:
           last_deleted = self.last_deleted.replace(tzinfo=None)
       else:
           last_published = None
       ...
       return last_published and ((last_deleted and last_published > last_deleted) or
                                  not last_deleted) and not force_full and\
           not delete

If last_deleted is None (a unit has never been deleted from the repo), then last_published is set to None and fast-forward publish doesn't happen. There's no indication of why this should happen and it seems likely to be a mistake. "last_published = None" may have been intended to be "last_deleted = None".

Steps to reproduce in development environment: (see also https://pulp.plan.io/issues/2532 )

# start with clean pulp
pclean ; ppopulate

dnf download cowsay

pulp-admin rpm repo sync run --repo-id zoo

# rsync_distributor.json example:
# {
#     "distributor_id": "my_rpm_rsync_distributor",
#     "distributor_type_id": "rpm_rsync_distributor",
#     "distributor_config": {
#         "remote": {
#             "auth_type": "publickey",
#             "ssh_user": "vagrant",
#             "ssh_identity_file": "/usr/share/httpd/.ssh/id_rsa",
#             "host": "localhost",
#             "root": "/home/vagrant/pulp_root" 
#         },
#         "predistributor_id": "yum_distributor" 
#     }
# }

phttp POST https://localhost/pulp/api/v2/repositories/zoo/distributors/ < rsync_distributor.json

# ensure both distributors are fully published:

phttp POST https://localhost/pulp/api/v2/repositories/zoo/actions/publish/ id=yum_distributor
# and wait until the publish task completes

phttp POST https://localhost/pulp/api/v2/repositories/zoo/actions/publish/ id=my_rpm_rsync_distributor
# and wait until the publish task completes

pulp-admin rpm repo uploads rpm --repo-id zoo --file cowsay-3.04-4.fc25.noarch.rpm

phttp POST https://localhost/pulp/api/v2/repositories/zoo/actions/publish/ id=yum_distributor
# and wait until publish completes

phttp POST https://localhost/pulp/api/v2/repositories/zoo/actions/publish/ id=my_rpm_rsync_distributor
# expected behavior: fast-forward publish is used
# actual behavior: fast-forward publish is not used since a unit has never been deleted from zoo repo

Note the distributor doesn't make it obvious whether fast-forward publish was used. When reproducing this I added logs to the distributor to determine which code paths were taken.