Comment 8 for bug 1826916

After having a look at all the provided logs, I see the following:

1. On dpkg.log I see that packages where installed and removed:

 - on 2019-04-19, non-maas related packages were configured (likely upgraded)
 - on 2019-04-24, maas related packages were marked for removal, and removed, e.g:

2019-04-24 06:02:09 startup packages remove
2019-04-24 06:02:09 status installed maas-region-controller:all 2.3.0-6434-gd354690-0ubuntu1~16.04.1
2019-04-24 06:02:11 remove maas-region-controller:all 2.3.0-6434-gd354690-0ubuntu1~16.04.1 <none>

2. On term.log, I see the counterparts of the above, were:

 - on 2019-04-19 packages were upgraded and MAAS wasn't removed
 - on 2019-04-24 I see that MAAS packages were removed, but nothing was upgraded nor updated.

3. On history.log, I confirm what I see the above, which is that:

 - on 2019-04-19 packages were ntfs-3g:amd64 was upgraded, and nothing removed automatically.
 - on 2019-04-24 MAAS related packages were removed.

From looking at the above, nothing really tells me what could be wrong and why MAAS packages were removed. However, the one thing to notice here is that MAAS 2.3.0-6434-gd354690 was the one removed. The interesting part, is the following:

4. From looking at install.log things turn interesting. This is because what's installed is MAAS 2.3.5-6511-gf466fdb-0ubuntu1.

So, from looking at all of the above I can conclude that:

a. There's not enough information why MAAS got removed.
b. The installed MAAS version on the system was *2.3.0-6434-gd354690* while the version available in -updates was *2.3.5-6511-gf466fdb-0ubuntu1*. This to me means that unattended upgrades never really upgraded the MAAS version with the latest in -updates (e.g. it seems this MAAS could've been installed when 2.3.0 was in -updates).
c. More interestingly, is that:
  - In previous unattended upgrades, no MAAS packages were removed, so why in the latest?
  - When MAAS was removed, no other packages were installed, which if there were to have been a conflict that would have caused MAAS to be removed, I would have expected a dependency would have conflicted and installed instead, which would have caused the upgrade? Unless unattended upgrades simply managed to remove while not upgrade a given dep?
 - When MAAS was manually installed, the installation happened just fine without really any issues, so if there would've been dependency issues, I would have expected the install to complain.

So from the above, it would seem that someone or something marked the MAAS package for removal, and doesn't seem related to a dependency because we can see no dep issues, or new deps installed which would've caused this. That said, I'm not certain how unattended upgrades works internally so not sure why it never did upgrade the MAAS version in previous upgrades, and why it removed it in the latest.