Comment 0 for bug 1828259

[rocky][19.04] Upgrading a DVR deployment from Queens to Rocky purged neutron-l3-agent package

Upgrading OpenStack from Queens to Rocky results in removal of neutron-l3-agent package which leads to a networking outage.

The issue with the fact that first python3 packages are installed and then python2 packages are purged. The neutron-l3-agent package depends on both.

At the same time neutron-dhcp-agent survives the upgrade while both packages seem to have identical "Depends" directives for python[3]-neutron:

https://git.launchpad.net/~ubuntu-server-dev/ubuntu/+source/neutron/tree/debian/control?h=stable/rocky#n178
Package: neutron-l3-agent
Architecture: all
Depends:
 conntrack,
 iputils-arping,
 keepalived,
 neutron-metadata-agent (= ${source:Version}),
 python-neutron (= ${source:Version}) | python3-neutron (= ${source:Version}),
 python-neutron-fwaas (>= 1:13.0.0~) | python3-neutron-fwaas (>= 1:13.0.0~),

https://git.launchpad.net/~ubuntu-server-dev/ubuntu/+source/neutron/tree/debian/control?h=stable/rocky#n156
Package: neutron-dhcp-agent
Architecture: all
Depends:
 dnsmasq-base (>= 2.76),
 dnsmasq-utils (>= 2.76),
 neutron-metadata-agent (= ${source:Version}),
 python-neutron (= ${source:Version}) | python3-neutron (= ${source:Version}),

When I try to install neutron-l3-agent it tries to pull python2 dependencies again (even though the python3 ones are already there):
https://paste.ubuntu.com/p/J7Vq8KKnBf/

More info below:

------
2019-05-07 16:42:41 DEBUG neutron-plugin-api-relation-changed Selecting previously unselected package neutron-l3-agent.
2019-05-07 16:42:41 DEBUG neutron-plugin-api-relation-changed Preparing to unpack .../6-neutron-l3-agent_2%3a12.0.5-0ubuntu1_all.deb ...
2019-05-07 16:42:41 DEBUG neutron-plugin-api-relation-changed Unpacking neutron-l3-agent (2:12.0.5-0ubuntu1) ...

2019-05-07 16:42:47 DEBUG neutron-plugin-api-relation-changed Setting up neutron-l3-agent (2:12.0.5-0ubuntu1) ...
2019-05-07 16:42:47 DEBUG neutron-plugin-api-relation-changed Created symlink /etc/systemd/system/multi-user.target.wants/neutron-l3-agent.service → /lib/systemd/syst
em/neutron-l3-agent.service.

/var/log/apt/term.log:

update-alternatives: using /usr/bin/python3-nova-metadata-wsgi to provide /usr/bin/nova-metadata-wsgi (nova-metadata-wsgi) in auto mode
(Reading database ... ^M(Reading database ... 5%^M(Reading database ... 10%^M(Reading database ... 15%^M(Reading database ... 20%^M(Reading database ... 25%^M(Reading database ... 30%^M(Reading database ... 35%^M(Reading database ... 40%^M(Reading database ... 45%^M(Reading database ... 50%^M(Reading database ... 55%^M(Reading database ... 60%^M(Reading database ... 65%^M(Reading database ... 70%^M(Reading database ... 75%^M(Reading database ... 80%^M(Reading database ... 85%^M(Reading database ... 90%^M(Reading database ... 95%^M(Reading database ... 100%^M(Reading database ... 113229 files and directories currently installed.)
Purging configuration files for python-neutron (2:13.0.2-0ubuntu1~cloud0) ...
Purging configuration files for neutron-l3-agent (2:13.0.2-0ubuntu1~cloud0) ...
Purging configuration files for python-neutron-fwaas (1:13.0.1-0ubuntu1~cloud0) ...
Purging configuration files for python-nova (2:18.1.0-0ubuntu1~cloud0) ...
Processing triggers for ureadahead (0.100.0-21) ...
Processing triggers for systemd (237-3ubuntu10.21) ...
Log ended: 2019-05-08 13:46:55

/var/log/apt/history.log:

# install python3 packages
Start-Date: 2019-05-08 13:45:18
Commandline: apt-get --assume-yes --option=Dpkg::Options::=--force-confold install nova-compute genisoimage librbd1 xfsprogs nfs-common ceph-common nova-compute-kvm n
ova-api-metadata python3-nova python3-memcache python3-rados python3-rbd python3-neutron

# purge python2 packages
Start-Date: 2019-05-08 13:46:40
Commandline: apt-get --assume-yes purge python-neutron python-nova
Purge: neutron-l3-agent:amd64 (2:13.0.2-0ubuntu1~cloud0), python-nova:amd64 (2:18.1.0-0ubuntu1~cloud0), python-neutron:amd64 (2:13.0.2-0ubuntu1~cloud0), python-neutron-fwaas:amd64 (1:13.0.1-0ubuntu1~cloud0)
End-Date: 2019-05-08 13:46:55

apt policy python3-neutron
https://paste.ubuntu.com/p/3vKsFBf9Hn/

apt-rdepends:

neutron-l3-agent
  Depends: conntrack
  Depends: iputils-arping
  Depends: keepalived
  Depends: neutron-metadata-agent (= 2:13.0.2-0ubuntu1~cloud0)
  Depends: python-neutron (= 2:13.0.2-0ubuntu1~cloud0)
  Depends: python-neutron-fwaas (>= 1:13.0.0~)
  Depends: python3-neutron (= 2:13.0.2-0ubuntu1~cloud0)
  Depends: python3-neutron-fwaas (>= 1:13.0.0~)
# ...

neutron-dhcp-agent
  Depends: dnsmasq-base (>= 2.76)
  Depends: dnsmasq-utils (>= 2.76)
  Depends: neutron-metadata-agent (= 2:13.0.2-0ubuntu1~cloud0)
  Depends: python-neutron (= 2:13.0.2-0ubuntu1~cloud0)
  Depends: python3-neutron (= 2:13.0.2-0ubuntu1~cloud0)
# ...

Charm code:
https://opendev.org/openstack/charm-neutron-openvswitch/src/branch/stable/19.04/hooks/neutron_ovs_utils.py#L323-L325

    if cmp_release >= 'rocky':
        return PURGE_PACKAGES
    return []

https://opendev.org/openstack/charm-neutron-openvswitch/src/branch/master/hooks/neutron_ovs_utils.py#L119-L122
PURGE_PACKAGES = [
    'python-neutron',
    'python-neutron-fwaas',
]

https://opendev.org/openstack/charm-neutron-openvswitch/src/branch/master/hooks/neutron_ovs_hooks.py#L115-L124

    install_packages()
    install_tmpfilesd()

    # NOTE(jamespage): purge any packages as a result of py3 switch
    # at rocky.
    packages_to_purge = determine_purge_packages()
    request_nova_compute_restart = False
    if packages_to_purge:
        purge_packages(packages_to_purge)
        request_nova_compute_restart = True