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.
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.
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.
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.
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`).
Most (all?) of our Matrix services are running in the `matrix` network,
so they were safe -- not accessible from Coturn to begin with.
Isolating Coturn into its own network is a security improvement
for people who were starting other services in the default
Docker network. Those services were potentially reachable over the
private Docker network from Coturn.
Discussed in #120 (Github Pull Request)
We run containers as a non-root user (no effective capabilities).
Still, if a setuid binary is available in a container image, it could
potentially be used to give the user the default capabilities that the
container was started with. For Docker, the default set currently is:
- "CAP_CHOWN"
- "CAP_DAC_OVERRIDE"
- "CAP_FSETID"
- "CAP_FOWNER"
- "CAP_MKNOD"
- "CAP_NET_RAW"
- "CAP_SETGID"
- "CAP_SETUID"
- "CAP_SETFCAP"
- "CAP_SETPCAP"
- "CAP_NET_BIND_SERVICE"
- "CAP_SYS_CHROOT"
- "CAP_KILL"
- "CAP_AUDIT_WRITE"
We'd rather prevent such a potential escalation by dropping ALL
capabilities.
The problem is nicely explained here: https://github.com/projectatomic/atomic-site/issues/203
With this change, the following roles are now only dependent
on the minimal `matrix-base` role:
- `matrix-corporal`
- `matrix-coturn`
- `matrix-mailer`
- `matrix-mxisd`
- `matrix-postgres`
- `matrix-riot-web`
- `matrix-synapse`
The `matrix-nginx-proxy` role still does too much and remains
dependent on the others.
Wiring up the various (now-independent) roles happens
via a glue variables file (`group_vars/matrix-servers`).
It's triggered for all hosts in the `matrix-servers` group.
According to Ansible's rules of priority, we have the following
chain of inclusion/overriding now:
- role defaults (mostly empty or good for independent usage)
- playbook glue variables (`group_vars/matrix-servers`)
- inventory host variables (`inventory/host_vars/matrix.<your-domain>`)
All roles default to enabling their main component
(e.g. `matrix_mxisd_enabled: true`, `matrix_riot_web_enabled: true`).
Reasoning: if a role is included in a playbook (especially separately,
in another playbook), it should "work" by default.
Our playbook disables some of those if they are not generally useful
(e.g. `matrix_corporal_enabled: false`).
As suggested in #63 (Github issue), splitting the
playbook's logic into multiple roles will be beneficial for
maintainability.
This patch realizes this split. Still, some components
affect others, so the roles are not really independent of one
another. For example:
- disabling mxisd (`matrix_mxisd_enabled: false`), causes Synapse
and riot-web to reconfigure themselves with other (public)
Identity servers.
- enabling matrix-corporal (`matrix_corporal_enabled: true`) affects
how reverse-proxying (by `matrix-nginx-proxy`) is done, in order to
put matrix-corporal's gateway server in front of Synapse
We may be able to move away from such dependencies in the future,
at the expense of a more complicated manual configuration, but
it's probably not worth sacrificing the convenience we have now.
As part of this work, the way we do "start components" has been
redone now to use a loop, as suggested in #65 (Github issue).
This should make restarting faster and more reliable.
Michael Collins
Dan Arnfield
Michael
Hardy Erlinger
Slavi Pantaleev
Chris van Dijk
Hugues De Keyzer
Sylvia van Os