While Docker isn't officially supported by Hometown, leaving the
Mastodon 3.5.5 Docker configuration in place with the new 4.0.2 code is
a bad idea. At minimum, you'll have a stale Node install that's months
behind on security updates. There are some minor tweaks to the default
configuration, but they're flagged by comments so they're easy to revert
or modify as necessary.
# Running Hometown on Docker
I'll by typing up my own longer blog post in due time, but there's no
harm dropping a cheat sheet here. By following this outline, I was able
to upgrade a Hometown 1.0.8 install to 1.1.0 with nothing worse than a
minute or two of downtime.
My configuration uses the GitHub repository as its source, rather than
images drawn from DockerHub. I like to tweak and fiddle with my setup,
especially the themes, and I'm happy to sacrifice some disk space for
the privilege.
## Installing from Scratch
This is by far the easiest approach, you just follow [one
of](https://gist.github.com/TrillCyborg/84939cd4013ace9960031b803a0590c4)
the [existing
guides](https://sleeplessbeastie.eu/2022/05/02/how-to-take-advantage-of-docker-to-install-mastodon/)
for running Mastodon via Docker, pause after you've set up
`.env.production`, add any Hometown-specific features to it [as per the
Wiki](https://github.com/hometown-fork/hometown/wiki), then resume what
the guide says to do.
If you're enabling ElastiSearch, the second of the two guides has some
additional actions you'll need to do, plus be aware of [this
bug](https://github.com/mastodon/mastodon/issues/18625) in Mastodon
which can quietly block ES from working at all.
## Upgrading from Hometown 1.0.8
Here's how I accomplished this. I committed any leftover changes, then
ran these commands from the non-Docker instructions in the root of my
local Hometown repository:
```
git remote update
git checkout v4.0.2+hometown-1.1.0
```
This "wiped out" my customizations, but as I committed them all to a
branch I can reconstruct them later via diffs. I then ran:
```
sudo docker-compose build
```
to build the new image. The old image will continue running in the
background, as per usual. I like adding `2>&1 | less` to the end and
mashing `PgDn`, as if a compilation error happens it almost invariably
requires scrolling back a few screens to find the issue.
If the build succeeded, we're almost clear to start the dangerous
portion. If you're running on the cloud, now would be a great time to
take a snapshot. Whatever the case, you should back up the existing
database. If you haven't changed the defaults from the Dockerfile, then
```
sudo docker exec -it hometown_db_1 pg_dump -U postgres -Fc postgres > hometown.db.dump
```
should do the trick. If you have changed the defaults, you may need to
use `sudo docker ps` to figure out the name of the PostgreSQL image to
swap in place of "hometown_db_1", then browse through `.env.production`
to extract the username to place after `-U` and the database name to
place after `-Fc`. The Hometown docs don't say how to restore the
database should the process go South, but after reading a manpage or two
I think the magic words are roughly
```
sudo docker exec -it hometown_db_1 pg_restore -U postgres --clean --if-exists -d postgres < hometown.db.dump
```
Now we're ready for the scary "you could destroy everything" part. All
the earlier commands are trivial to roll back, but after this point any
delay could cause data corruption. As per the Hometown docs, run the
pre-deployment database migrations.
```
sudo docker-compose run -e SKIP_POST_DEPLOYMENT_MIGRATIONS=true -e RAILS_ENV=production --rm web bundle exec rails db:migrate
```
where `web` is the name of the webserver image in `docker-compose.yml`.
The docs state you should precompile all assets next, but I'm 95% sure
they were already built when you ran `sudo docker-compose build`. If
you're paranoid and want to be absolutely sure precompilation is done,
then at this stage run:
```
sudo docker-compose run -e RAILS_ENV=production --rm web bundle exec rails assets:precompile
```
Here, the Hometown docs say you should run the post-deployment
migrations. In Docker-ese:
```
sudo docker-compose run -e RAILS_ENV=production --rm web bundle exec rails db:migrate
```
Finally, we need to stop the old images and spin up the new ones. Run:
```
sudo docker-compose up -d
```
and give Docker some time to finish rotating. A quick `sudo docker ps`
should confirm the new images are booting up, and in a short while
(10-15 seconds for the teeny-tiny instance I manage) you should be back
to fully functional.
Some bundle options are saved as global user config and not project local.
Specially, `deployment` must be saved as local config to be run on copied environment
[Rkt](https://coreos.com/rkt) doesn't allow ports to be exposed to containers unless they are declared in the container manifest. Re-adding EXPOSE back in (removed in 1dbf993bce) allows the container to be used on rkt based systems.
- Always run apt update before any other apt command. (This fixes
incremental builds failing if a remote package is updated.)
- Only copy dependency lists before installing dependencies. (This means
editing code doesn't force all dependencies to be re-downloaded.)
- Delete cache in the same layer that it is created. (Otherwise,
deleting cache *increases* the size of the image on non-squashed
builds.)
- Move the installation of some static dependencies to *before* Mastodon
code is imported to Docker.
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