These are just defensive cleanup tasks that we run.
In the good case, there's nothing to kill or remove, so they trigger an
error like this:

> Error response from daemon: Cannot kill container: something: No such container: something

and:

> Error: No such container: something

People often ask us if this is a problem, so instead of always having to
answer with "no, this is to be expected", we'd rather eliminate it now
and make logs cleaner.

In the event that:
- a container is really stuck and needs cleanup using kill/rm
- and cleanup fails, and we fail to report it because of error
suppression (`2>/dev/null`)

.. we'd still get an error when launching ("container name already in use .."),
so it shouldn't be too hard to investigate.

This needs to be added for WebSocket upgrades to work properly (see doc:
http://nginx.org/en/docs/http/websocket.html)

While administering we will occasionally invoke this script interactively with the "non-interactive" switch still there, yet still sit at the desk waiting for 300 seconds for this timer to run out.

The systemd-timer already uses a 3h randomized delay for automatic renewals, which serves this purpose well.

> WARNING: Error loading config file: .dockercfg: $HOME is not defined

.. which appeared in Docker 20.10.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/756

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/737

I feel like timers are somewhat more complicated and dirty (compared to
cronjobs), but they come with these benefits:

- log output goes to journald
- on newer systemd distros, you can see when the timer fired, when it
will fire, etc.
- we don't need to rely on cron (reducing our dependencies to just
systemd + Docker)

Cronjobs work well, but it's one more dependency that needs to be
installed. We were even asking people to install it manually
(in `docs/prerequisites.md`), which could have gone unnoticed.

Once in a while someone says "my SSL certificates didn't renew"
and it's likely because they forgot to install a cron daemon.

Switching to systemd timers means that installation is simpler
and more unified.

Not sure if it breaks with them or not, but no other directive
uses quotes and the nginx docs show examples without quotes,
so we're being consistent with all of that.

Code was clean up and simplified to make it simpler and easier to
maintain. No features were modified.

The different configurations are now all lower case, for consistent
naming.

`matrix_nginx_proxy_ssl_config` is now called
`matrix_nginx_proxy_ssl_preset`. The different options for "modern",
"intermediate" and "old" are stored in the main.yml file, instead of
being hardcoded in the configuration files. This will improve the
maintainability of the code.

The "custom" preset was removed. Now if one of the variables is set, it
will use it instead of the preset. This will allow to mix and match more
easily, for example using all the intermediate options but only
supporting TLSv1.2. This will also provide better backward
compatibility.

A new variable called `matrix_nginx_proxy_ssl_config` is created for
configuring how the nginx proxy configures SSL. Also a new configuration
validation option and other auxiliary variables are created.

A new variable configuration called `matrix_nginx_proxy_ssl_config` is
created. This allow to set the SSL configuration easily using the
default options proposed by Mozilla. The default configuration is set to
"Intermediate", removing the weak ciphers used in the old
configurations.

The new variable can also be set to "Custom" for a more granular control.
This allows to set another three variables called:

- `matrix_nginx_proxy_ssl_protocols`,
- `matrix_nginx_proxy_ssl_prefer_server_ciphers`
- `matrix_nginx_proxy_ssl_ciphers`

Also a new task is added to validate the SSL configuration variable.

The Docker 19.04 -> 20.10 upgrade contains the following change
in `/usr/lib/systemd/system/docker.service`:

```
-BindsTo=containerd.service
-After=network-online.target firewalld.service containerd.service
+After=network-online.target firewalld.service containerd.service multi-user.target
-Requires=docker.socket
+Requires=docker.socket containerd.service
Wants=network-online.target
```

The `multi-user.target` requirement in `After` seems to be in conflict
with our `WantedBy=multi-user.target` and `After=docker.service` /
`Requires=docker.service` definitions, causing the following error on
startup for all of our systemd services:

> Job matrix-synapse.service/start deleted to break ordering cycle starting with multi-user.target/start

A workaround which appears to work is to add `DefaultDependencies=no`
to all of our services.

Fixup for 12867e9f18.

This shouldn't have been caught in the `if`.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/734

Since the switch from `-v` to `--mount` (in 1fca917ad1),
we've regressed when `matrix_ssl_retrieval_method == 'none'`.

In such a case, we don't create `/matrix/ssl` directories at all
and shouldn't be trying to mount them into the `matrix-nginx-proxy`
container.

Previously, with `-v`, Docker would auto-create them, effectively hiding
our mistake. Now that `--mount` doesn't do such auto-creation magic,
the `matrix-nginx-proxy` container was failing to start.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/734

Continuation of 1fca917ad1.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/722

`-v` magically creates the source destination as a directory,
if it doesn't exist already. We'd like to avoid this magic
and the potential breakage that it might cause.

We'd rather fail while Docker tries to find things to `--mount`
than have it automatically create directories and fail anyway,
while having contaminated the filesystem.

There's a lot more `-v` instances remaining to be fixed later on.
This is just some start.

Things like `matrix_synapse_container_additional_volumes` and
`matrix_nginx_proxy_container_additional_volumes` were not changed to
use `--mount`, as options for each one are passed differently
(`ro` is `ro`, but `rw` doesn't exist and `slave` is `bind-propagation=slave`).
To avoid breaking people's custom volume mounts, we keep it as it is for now.

A deficiency with `--mount` is that it lacks the `z` option (SELinux
ownership changes), and some of our `-v` instances use that. I'm not
sure how supported SELinux is for us right now, but it might be,
and breaking that would not be a good idea.

Fixes #696 (Github Issue)

The regex introduced in 63a49bb2dc seems to take precedence
over the bare location blocks, causing a regression.

> It is important to understand that, by default, Nginx will serve regular expression matches in preference to prefix matches.
> However, it evaluates prefix locations first, allowing for the administer to override this tendency by specifying locations using the = and ^~ modifiers.

Source: https://www.digitalocean.com/community/tutorials/understanding-nginx-server-and-location-block-selection-algorithms

Fixes #685 (Github Issue).

This is mainly to address SSL renewal not working for us due to:
- https://github.com/ansible/ansible/issues/71213
- https://github.com/ansible/ansible/pull/71207

Using the cron module was hacky anyway. We shouldn't need an extra
level of buggy abstraction to manage a cronjob file.

In #628 I proposed a CORS change that turns out not to be the root of the issue. Caffeine-addled diagnosis leads to sloppy thinking, and this change should be reverted. In fact, if left it will cause problems for new installations.

Even with the v2 updates listed in #503 and partially addressed in #614, this is still needed to enable identity services to function with Element Desktop/Web. Testing on multiple clients with a clean config has confirmed this, at least for my installation.

Hopefully fixes a regression caused by b106a9592e.

Related to #597 (Github Pull Request).

Fix regression since 2a50b8b6bb (#597).

Dimension is intended to be embedded in various clients,
be it the Element service that we host (at element.DOMAIN),
some other Element (element-desktop running locally), etc.

Fixes #586 (Github Issue)

Besides /_synapse/admin, there are other things like
/_synapse/oidc, etc.

We should just proxy everything.

Fixes #534 (Github Issue).

Depending on the distro, common commands like sleep and chown may either
be located in /bin or /usr/bin.

Systemd added path lookup to ExecStart in v239, allowing only the
command name to be put in unit files and not the full path as
historically required. At least Ubuntu 18.04 LTS is however still on
v237 so we should maintain portability for a while longer.

Fixes #417 (Github Issue)

Continuation of #234 (Github Pull Request).

I had unintentionally updated the documentation for the feature,
saying the page is available at `https://matrix.DOMAIN/nginx_status`.

Looks like it wasn't the case, going against my expectations.

I'm correcting this with this patch.
The status page is being made available on both HTTP and HTTPS.
Serving over HTTP is likely necessary for services like
Longview
(https://www.linode.com/docs/platform/longview/longview-app-for-nginx/)

Fixes #191 (Github Issue).

Reasoning is the same as for matrix-org/synapse#5023.

For us, the journal used to contain `docker` for all services, which
is not very helpful when looking at them all together (`journalctl -f`).

Use Jinja2 lstrip_blocks option in templates to ensure consistent
indentation in generated files.